122,197 research outputs found
Pleojassa lowryi Conlan 2021, n. sp.
No full textPleojassa lowryi n. sp. (Figs 25 and 26) Description of male. Holotype: Length 5.3 mm. Without antenna 1. (Paratype, male, 3.8 mm, antenna 2 overlapped by antenna 1 to the end of article 5). Antenna 2: article 5 and flagellum, posterior margin bearing abundant plumose setae, simple filter setae interspersed, these sparser and shorter than in the female; flagellum 3 articles, article 1 86% of full flagellum length. Mandible: palp articles 2 and 3 without a dorsal fringe of setae; raker spines 4 right, 6 left. Gnathopod 1: coxal margins, anterior 112% of dorsal length; ventral margin straight; basis, antero-medial margin with a row of short, spine-like setae, antero-lateral and posterior margins setose only distally; carpus, length 60% of propodus length, posterior lobe 42% of anterior margin length, setal cluster short, 16% of the anterior margin length; propodus, palm nearly straight, one defining spine slightly proximal of centre. Gnathopod 2: coxal margins, anterior 48% and posterior 70% of ventral length; ventral margin shallowly concave; carpus less than a quarter the length of the propodus; propodus, hinge tooth conical, shallowly bifid, palm densely plumose throughout, defined by a single minute spine at the end of a short hook-like protuberance. Pereopod 3: basis slender, anterior margin shallowly convex; merus, anterior margin setose centrally and distally, central setae less than 1/4 article width, article width 73% of length; carpus three quarters to fully overlapped by the merus; propodus width 58% of length. Pereopods 5–7: stout, basis of pereopod 6 and 7 posterodistally produced, anterior margin of each basis spinose; merus bearing spines along its posterior margin. Uropod 1: peduncle, posteroventral spinous process underlying 39% of the inner ramus, inner and outer rami with 3 and 5 mid-dorsal spines respectively. Uropod 2: peduncle, posteroventral spinous process underlying 17% of the inner ramus. Uropod 3: inner ramus with 1 spine mid-dorsally. Condition. Without antennae 1, right antenna 2, right pereopods 5 and 6, and both pereopods 7. Remaining right appendages (or left appendage when right lacking), telson, and mouthparts slide mounted. Other left appendages with the carcass. Description of adult female. Allotype: Length 5.1 mm. Character states as in the male except as follows. Antenna 1: overlapping antenna 2 to the end of article 5; article 5, posterior margin with long filter setae and a few plumose setae distally; flagellum, posterior margin with a few plumose setae proximally and brush setae distally. Gnathopod 2: propodus without a hinge tooth, palm 58% the length of the posterior margin, setae plumose, so abundant as to obscure the palm’s shape. Condition. Without left pereopod 7. Variation. Maximum body length: male 5.3 mm, female 5.1 mm. Males of comparable body length to adult females have abundant plumose setae on the posterior margin of the second antennal article 5 and flagellum. Small males and juvenile females lack plumose setae on antenna 2 but bear long filter setae. The palm of gnathopod 2 is abundantly plumose in both adult females and comparably sized males and less so in small males and females. There is no evidence of thumb production in males of similar body length to adult females. There is some divergence in the gnathopod 2 propodus length between the sexes, with a greater length achieved by males than females of similar body length (Fig. 26). Type material examined. Holotype, ♂, Rima Islet, The Snares, New Zealand (48°07ʹS, 166°36ʹE), in a crevice in the Durvillea zone, barnacles encrusted with sponge, 21 Nov. 1976, G. D. Fenwick, coll. (AM P.34948, collection event SA-3417). Allotype, ♀, same location (AM P.37922). Paratypes, 5 adult ♂♂, 25 adult ♀♀, and 163 juveniles, same location (AM P.37923). Other material examined. Alert Stack, The Snares, New Zealand (48°07ʹ S, 166°36ʹE), from algae below the Durvillea zone to 7m depth, 20 Dec. 1976, G. D. Fenwick, coll., 2 juveniles (AM P.34949, collection event SA- 3456). Etymology. In gratitude to Dr. Jim Lowry (Australian Museum) for assistance in locating Southern Hemisphere material. Remarks. The spination on the anterior margin of the basis of gnathopod 1 is not homologous with that of the Southern Hemisphere Jassa alonsoae Conlan, 1990, J. justi Conlan, 1990, J. fenwicki Conlan, 1990 and J. hartmannae Conlan, 1990 because it is medial instead of lateral. Readily recognizable differences between Pleojassa lowryi and P. moorei are listed in Table 4.Published as part of Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1) on pages 44-45, DOI: 10.11646/zootaxa.4921.1.1, http://zenodo.org/record/449601
Schisturella spinirama Hendrycks & Conlan 2003
No full textSchisturella spinirama Hendrycks & Conlan, 2003 Schisturella spinirama Hendrycks & Conlan, 2003: 2329, figs 11, 12.― Larsen, 2007: 14 (key). Types. Holotype, male, 9 mm, CMNC 2002-0037. Type locality. Off Point Conception, California, USA (34°47.18’N 123°04.18’W), 4050 m. Habitat. Not recorded. Depth range. 4050 m (Hendrycks & Conlan 2003). Distribution. Eastern Pacific Ocean. Off central California (Hendrycks & Conlan 2003).Published as part of Kilgallen, N. M. & Lowry, J. K., 2014, The Tryphosa group (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae), pp. 501-545 in Zootaxa 3768 (5) on page 525, DOI: 10.11646/zootaxa.3768.5.1, http://zenodo.org/record/490968
Ischyrocerus Conlan, 2021, n. comb.
No full textGenus Ischyrocerus n. comb. Supplementary Table S4 Type species. Ischyrocerus anguipes Krøyer, 1838 Diagnosis (with differences from Neoischyrocerus in bold). Body length at maturity 2–18 mm, though most species are> 5 mm long at adulthood. Primarily known from the Northern Hemisphere in cold temperate to polar waters from 32°N (La Jolla, California; J.L. Barnard 1969) to 81°N in the Arctic Ocean (Stephensen 1944), collected from algae, hydroids, crabs or substrate unknown, 1 to ~ 2000 m. Widely known in Europe but not in the Southern Hemisphere, although one species was found at 42°S off of Chile (J.L. Barnard 1964). Pereon: dorsally smooth (most species), ridged or carinate (some species). Antenna 1: accessory flagellum 2 articles (second minute), flush with the flagellum or rarely projecting forward; antenna 2 peduncle article 4, 115–170% wider than antenna 1 peduncle article 2 (or rarely equal width), setae and setal pattern similar to antenna 1 or setae shorter, occasionally plumose. Gnathopod 2, adult male: 100–220% the length of gnathopod 1, basis usually not especially elongate, propodus elongate and slender or short and broad (rarely similar to gnathopod 1); coxa 1 70–140% the depth of coxa 2; basis concave or straight; ischium anteriorly rounded or straight; propodus variably shaped, slender or broad (posterior length 120–290% of central width), palm only on the distal portion of the propodus or nearly the full length of the propodus, without a bulge or tooth defining it proximally at the junction of the carpus, palm variously toothed; dactyl 33–75% the length of the propodus. Gnathopod 2, juvenile male: shorter than the adult male gnathopod 2, palm bearing 1–2 strong spines about midway along the length of the propodus, dactyl ending at the spines. Gnathopod 2, female: only slightly larger than gnathopod 1, palm of the propodus convex or concave. Pereopods 3 and 4: propodus, posterior margin bearing setae but not spines; c oxa 4, posterior margin straight to shallowly concave. Pereopod 5, male: similar to but shorter than pereopods 6 and 7 or basis posteriorly concave; merus not differing. Uropod 1: peduncle with short ventrodistal spinous process underlying the rami, length ~25–50% of the outer ramus length. Uropod 3: peduncle bearing 0–2 rows of spines dorsally, ending in a corona of spines at the distal margin (rarely a single seta or single spine); rami with 0–1 spines (outer), 0–4 spines (inner), outer ramus subequal to a third shorter than the inner and bearing 0–9 cusps, occasionally with 1–2 apical spines that are straight or dorsally recurved. Component species. Ischyrocerus anguipes Krøyer, 1838 (N. Europe and Arctic Ocean); I. latipes Krøyer, 1842 (Arctic Ocean); I. minutus Liljeborg, 1851 (N. Europe); I. megacheir (Boeck, 1871) (40°N– 80°N, Atlantic to Arctic Ocean); I. brevicornis (Sars, 1879) (E. Greenland, Arctic Ocean); I. tuberculatus (Hoek, 1882) (Barents Sea, 71°N– 77°N); I. tenuicornis (Sars, 1885) (N. Europe); I. nanoides (Hansen, 1887) (Arctic, Baffin Bay and W Greenland, 61°N – 81°N); I. megalops Sars, 1894 (N. Europe); I. commensalis Chevreux, 1900 (E. Atlantic Canada and Saguenay Fjord); I. brusilovi Gurjanova, 1933 (Russian waters); I. enigmaticus Gurjanova, 1934 (Kara Sea, 78°58ʹN); I. cristatus Gurjanova, 1938 (Sea of Japan); I. elongatus Gurjanova, 1938 (Sea of Japan); I. rhodomelae Gurjanova, 1938 (Sea of Japan); I. serratus Gurjanova, 1938 (Sea of Japan); I. hanseni Stephensen, 1944 (64°N, between Iceland and Greenland); I. albanovi Gurjanova, 1946 (Arctic Ocean); I. laptevi Gurjanova, 1946 (Arctic Ocean); I. chamissoi Gurjanova, 1951 (Russian waters); I. dezhnevi Gurjanova, 1951 (Russian waters); I. krascheninnikovi Gurjanova, 1951 (Russian waters); I. stephenseni Gurjanova, 1951 (Russian waters); I. pelagops J.L. Barnard, 1962 (California); I. hortator J.L. Barnard, 1964 (off Chile); I. malacus J.L. Barnard, 1964 (California); I. gurjanovae Kudrjaschov, 1975 (Kurile Islands); I. tzvetkovae Kudrjaschov, 1975 (Kurile Islands); I. fractus King & Holmes, 2004 (Ireland). Remarks. Species were retained in Ischyrocerus if they lacked the key characters noted above for Neoischyrocerus in the appearance of the male gnathopod 2, pereopod dactyls or uropod 3 spination pattern. Ischyrocerus fractus is the only species known in this genus where the male’s gnathopod 2 propodus is very little different from the female’s. It is also the smallest known at adulthood for this genus (2 mm). Excluded, but uncertain generic status. Ischyrocerus camptonyx Thurston, 1974b from subantarctic Signy Island is not Ischyrocerus. It is possibly an undescribed species of Jassa or synonymous with J. alonsoae, in which case Thurston’s name would take precedence. Jassa thurstoni Conlan, 1990 (called J. falcata form 2 by Thurston) and Pleojassa moorei n. sp. (called J. falcata form 3) are also known from Thurston’s collections there. For I. camptonyx, hallmarks of the genus Jassa, rather than Ischyrocerus are the spines at the tip of the antenna 2, the sinuous palmed gnathopod 2, the strong overlap of the merus over the carpus on pereopods 3 and 4, the typical Jassa -like uropod 3 with long peduncle lacking mid-dorsal spines (but with a corona of spines around the distal margin), a lateral setal brush and the strong hooked spines at the tip of the outer ramus, and the telson with a long seta at each corner rather than a spine. However, Thurston describes the uropod outer ramus “with three stout hooked spines dorsally near apex and a minute comb with five-six teeth laterally”, which does not correspond to his illustration and are not Jassa -like. Possibly, though, his description could be interpreted differently. One of the three spines may be the apically immersed, dorsally recurved spine typical of Jassa, the other two spines are cusps, and the five–six teeth are minute dorsal cusps proximal to the two large ones. If so, then this also speaks of I. camptonyx as being a Jassa, either its own species or synonymous with J. alonsoae. It is not a Pleojassa, even though the male’s second-gnathopod resembles that of P. moorei, because this genus lacks a gill on gnathopod 2 while I. camptonyx possesses one. Thurston considered that the few males available for study were juvenile because they all lacked a thumb as in Jassa. However, some of these specimens were larger than the adult, ovigerous females. The female allotype was 4.5 mm and the male holotype was 5.5 mm. This suggests that the male holotype is actually an adult that will not produce a thumb, in which case it is not Jassa. Therefore, until the range of variation can be assessed in Thurston’s specimens, this species should remain in Ischyrocerus with a question as to its proper generic placement. Uncertain status of Ischyrocerus anguipes in the Southern Hemisphere. Sars’ (1894) excellent illustrations of I. anguipes may have resulted in some mis-identifications by early workers in the Southern Hemisphere. Alternatively, their identifications were correct and I. anguipes was being introduced by shipping if the specimens came from ports. K.H. Barnard’s (1916) “ I. anguipes ” could have been a species of Neoischyrocerus, however, as the specimens were 3 mm and the male’s second gnathopod propodus was 3.5 x longer than wide with the dactyl nearly the full length of the propodus, which is typical of adult male Neoischyrocerus. Schellenberg’s (1953) “ I. anguipes ” from L̹deritzbucht, Namibia was a 4.8 mm male which he stated differed from K.H. Barnard’s (1916) “ I. anguipes ” in its gnathopod 2 morphology. “The metacarpus of the 2nd gnathopod is shaped in the same way but stronger and exhibits a spination like on the first gnathopod. The palm is evenly finely corrugated (or: “wavy”) along its almost entire length.” (Der fast gleich geformte, aber stärkere Metacarpus des 2. Gnathopoden zeigt die Bestachelung wie am 1. Gnathopoden. Die Palma ist fast in ihrer ganzen Länge gleichmässig fein gewellt.) (translated from German to English by Jan Beermann, Alfred Wegener Institute, Bremerhaven, Germany). The similarly shaped gnathopods 1 and 2 suggest that this specimen was a female or juvenile, or an adult male of a different species, as adult male I. anguipes have a gnathopod 2 that is more than twice the length of gnathopod 1, with a concave, rather than convex palm. Schellenberg illustrated the uropod 3 outer ramus as 5-cusped, terminating in a basally immersed, dorsally recurved spine similar to Jassa. The corona of spines at the peduncle’s distal margin is typical of Ischyrocerus and Jassa. “ I. anguipes ” captured off the coast of Ceylon in ~ 150 m depth were briefly described by Walker (1904) but not illustrated. One male and one ovigerous female were 2.5 mm long. The male’s gnathopod 2 was similar to that of I. anguipes, but this could also be Neoischyrocerus which has similarly shaped, though more pendulous second gnathopods with the dactyl in the largest males nearly the full length of the propodus. Chilton (1921) described “ I anguipes ” from Lyttelton, New Zealand which were up to 6 mm long, saying that they closely resembled Sars’ (1894) illustrations of that species. His description was minimal, however, and he provided no illustrations.Published as part of Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1) on pages 59-61, DOI: 10.11646/zootaxa.4921.1.1, http://zenodo.org/record/449601
Neoischyrocerus Conlan, 2021, n. comb.
No full text<p> <b> Genus <i>Neoischyrocerus</i> n. comb.</b> </p> <p>Supplementary Table S3</p> <p> <b>Type species.</b> <i>N. claustris</i> J.L. Barnard, 1969</p> <p> <b> Diagnosis. (with differences from <i>Ischyrocerus</i> in bold).</b> Body length at maturity <b>1–2 mm (usually), rarely 4–6 mm. Tropical and warm temperate</b> distribution, collected from algae, sponges, corals or from a spiny lobster, <b>0–16 m, 9– 40°N and 5– 34°S.</b></p> <p> <i>Pereon</i>: dorsally smooth (most species), ridged or carinate (some species).</p> <p> <i>Antenna 1</i>: accessory flagellum 2 articles (second minute), projecting forward or flush with the flagellum; antennae 1 and 2 peduncles <b>subequal</b> in width or antenna 2, <b>10% wider</b> (based on comparison of antenna 1 peduncle article 2 with antenna 2 peduncle article 4), peduncular setae and setal pattern similar to antenna 1, or slightly shorter, <b>not plumose.</b></p> <p> <i>Gnathopod 2, adult male</i>: <b>190–350%</b> the length of gnathopod 1, <b>basis and propodus especially elongate</b>; coxa 1, <b>60–110%</b> the depth of coxa 2; basis <b>concave or sinuous</b>; ischium anteriorly rounded; propodus often slender (posterior length <b>180–400%</b> of central width), <b>palm nearly the full length of the propodus, often with a bulge or tooth defining it proximally at the junction of the carpus (sometimes palm continuous with the carpus), sometimes centrally toothed instead and with shallow bulge or teeth at the junction of the dactyl</b>; <b>dactyl half or nearly the full length</b> of the propodus.</p> <p> <i>Gnathopod 2, juvenile male</i>: shorter than the adult male gnathopod 2, palm bearing 1–2 strong spines about midway along the length of the propodus, dactyl ending at the spines.</p> <p> <i>Gnathopod 2, female</i>: only slightly larger than gnathopod 1, palm of the propodus convex (usually) or shallowly concave (rarely).</p> <p> <i>Pereopods 3 and 4</i>: propodus, posterior margin bearing <b>spines or setae</b>; coxa 4, posterior margin <b>straight, not shallowly concave.</b></p> <p> <i>Pereopod 5, male</i>: similar to but shorter than pereopods 6 and 7 or <b>variously modified with posteriorly concave basis or posteriorly expanded and spinose merus.</b></p> <p> <i>Uropod 1</i>: peduncle with short ventrodistal spinous process underlying the rami, length <b>~15–35%</b> of the outer ramus length.</p> <p> <i>Uropod 3</i>: peduncle bearing 1–2 rows of spines dorsally, ending in a single spine at the distal margin, but <b>without a corona of spines</b> around the margin or setae; rami <b>without spines mid-dorsally</b>, outer ramus subequal to or shorter than the inner and bearing <b>3–8</b> minute dorsal cusps apically, <b>without (rarely with) a small apical straight spine</b>.</p> <p> <b>Component species (with transferred species in bold).</b> <b> <i>Ischyrocerus longimanus</i> (Haswell, 1879)</b> (Australia); <b> <i>I. parvus</i> Stout, 1913</b> (California); <b> <i>I. carinatus</i> K.H. Barnard, 1916</b> (South Africa); <b> <i>I. gorgoniae</i> K.H. Barnard, 1940</b> (South Africa); <b> <i>I. ctenophorus</i> Schellenberg, 1953</b> (South Africa); <b> <i>Coxischyrocerus inexpectatus</i> (Ruffo, 1959)</b> (Mediterranean, Red Sea?); <i>N. claustris</i> J.L. Barnard, 1969 (California); <i>N. lilipuna</i> J.L. Barnard, 1970 (Hawaii); <b> <i>I. oahu</i> J.L. Barnard, 1970</b> (Hawaii); <b> <i>I. oahu oahu</i> J.L. Barnard, 1970</b> (Hawaii); <i>N. chinipa</i> J.L. Barnard, 1979 (Galapagos Islands and Panama); <b> <i>I. oahu armatus</i> Ledoyer, 1979</b> (Madagascar); <b> <i>Tropischyrocerus socia</i> (Myers, 1989)</b> (Bora Bora); <b> <i>I. mediodens</i> Myers, 1995</b> (Papua New Guinea); <b> <i>I. parma</i> Myers, 1995</b> (Papua New Guinea); <b> <i>I. apiensis</i> Myers, 1997</b> (Samoa); <i>N. vidali</i> Ortiz & Lalana, 2002 (Cuba); <b> <i>C. rhombocoxus</i> Just, 2009</b> (Australia); <b> <i>T. pugilus</i> Just, 2009</b> (Australia).</p> <p> <b>Remarks.</b> Species of <i>Ischyrocerus</i> were transferred to <i>Neoischyrocerus</i> if they demonstrated at least one key character (grossly enlarged and pendulous male gnathopod 2 similar in shape to that of others in the genus; dactyls with comb-like striae as noted in J.L. Barnard (1970), Conlan (1995) and Ortiz & Lalana (2002); similar spination on uropod 3). Presence or absence of these striae were not mentioned by other authors, therefore questioning as to whether this character had been looked for. Mouthpart characteristics were not widely described, but may be useful for generic definition, especially the clavate vs slenderer shape of the mandibular palp and the presence/absence of a long apical seta on the maxilla 1 inner plate.</p> <p> <b>Excluded but uncertain generic status</b>. <i>Ischyrocerus kapu</i> J.L. Barnard, 1970 from Hawaii. The author based the generic assignment on a single male specimen. He noted its resemblance to <i>N. lilipuna</i> but also considered that it should be in a new genus. On balance, though, he assigned it to <i>Ischyrocerus</i> but noted that this was based on limited information because the specimen lacked antennae and pereopods and the female was also unknown. The male’s gnathopod 2 is unusual in having a long conical extension of the merus underneath the propodus, a feature that is not known for either <i>Ischyrocerus</i> or <i>Neoischyrocerus</i>. Myers (1995) stated that <i>I. kapu</i> is congeneric with other species being transferred to <i>Neoischyrocerus</i>. The male’s propodus is wider than in other members of <i>Neoischyrocerus</i>, but its uropod 3 resembles other species of <i>Neoischyrocerus</i> rather than <i>Ischyrocerus</i>. Further material demonstrating the species’ complete morphology is required before it can be confidently transferred to <i>Neoischyrocerus</i> or to a new genus.</p>Published as part of <i>Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1)</i> on pages 58-59, DOI: 10.11646/zootaxa.4921.1.1, <a href="http://zenodo.org/record/4496015">http://zenodo.org/record/4496015</a>
Plumulojassa Conlan 2021, n. gen.
No full textGenus Plumulojassa n. gen. Description of male. Maximum body length 4.1 mm. Head lobe: triangular, apically acute. Antenna 1: accessory flagellum 1 article. Antenna 2: slightly stouter than antenna 1 but hardly longer, filter setae somewhat shorter, never with plumose setae; flagellum with at least the last two articles bearing posteriorly curved spines, first article considerably longer than any of the following articles. Maxilla 1: inner plate bearing a few short, fine setae; palp without setae at the base of article 1, article 2 with 1 row of facial setae. Gnathopod 1: coxa rectangular; propodus defined by 3 spines (medial-lateral-medial), these mid-distant along the palm; dactyl not facially striated. Gnathopod 2: with a gill; coxa deeper posteriorly; basis, anterolateral and anteromedial margins clothed in long plumose setae; carpus less than 1/4 propodus length; propodus, palm with a broad, bifid or trifid hinge tooth, defined by two narrow, apically acute teeth, these reaching nearly to the depth of the hinge tooth, thus giving the palm a transverse appearance; dactyl shorter than the propodus, inner margin slightly sinuous, tip reaching beyond the posterior defining tooth; dactyl, cusps reduced to small buttons interspersed with a few short setae. Pereopod 3: coxa deepest at the centre; basis not slenderer in larger males, margins convex; merus overlapping the carpus, anterior margin bearing a series of single plumose setae; propodus not posteriorly spinose. Pereopods 5–7: at least one basis posterodistally produced, anterior margin with a few short setae and no spines; merus not posteriorly spinose; carpus bearing 2 spines at the posterodistal angle on pereopod 5 and sometimes also on pereopod 6; spines lacking on pereopod 7; propodus not markedly expanded anteriorly; dactyl without facial striations, posterior (outer) margin not cusped distally, anterior (inner) margin bearing a seta only at the unguis. Pleopods: rami long, length> depth of the pleon, each with 2 coupling hooks. Urosome: segment 1 bearing a pair of setae dorsally. Uropod 3: peduncle mid-ventrally setose, without mid-dorsal spines or mid-ventral setae, but with a crown of spines dorsomedially at the insertion of the rami, and a small cluster of setae distolaterally; outer ramus not setose mid-dorsally, tipped by a basally immersed, dorsally recurved spine, a single seta at the spine’s point of immersion and a dorsal cluster of minute cusps proximal to the spine, none of these cusps particularly larger than the other; inner ramus with a single apical spine. Telson: dorsolateral cusps accompanied by setae (1 long, single and 2 short, plumose) but without spines. Description of adult female. Body length at maturity 2.4–4.0 mm. Character states as in the male except as follows. Brood plates: broad, setae abundant, hook-tipped. Antenna 2: posterior filter setae long, not shorter in larger individuals. Gnathopod 1: basis not flanged, without plumose setae. Gnathopod 2: propodus much larger and different in shape from the propodus of gnathopod 1 but differing only in the following respects from the large male: size slightly smaller, hinge tooth bifid, distal palmar tooth more central, proximal tooth little more than an acute expansion, bearing a large, single medial defining spine; dactyl, inner margin straight, tip apposing the defining spine. Type species. Podocerus ocius Bate, 1862 (monotypy). Etymology. The name refers to the abundant plumose setae on the anterior legs, particularly gnathopod 2, which makes this genus unmistakable among the Jassa -like genera, even at young stages.Published as part of Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1) on pages 9-10, DOI: 10.11646/zootaxa.4921.1.1, http://zenodo.org/record/449601
Jassa slatteryi Conlan 1990
No full textJassaslatteryi Conlan, 1990 (Table 10, Figs 22–27) J. cadetta Krapp etal., 2008, pp. 337–345, figs. 4–7 J. trinacriae Krapp etal., 2010, pp. 85–100, figs. 5–7 Diagnosis. Both sexes: Mandibular palp: article 2, dorsal margin without a fringe of setae. Maxilla 1: without a seta or setal cluster at the base of the palp article 1. Gnathopod 1: basis, anterolateral margin without a row of short setae along its length; carpus with a single or group of long setae at the anterodistal junction of the propodus, (seta(e) Ẑ50% the length of the anterior margin length and slightly medial). Gnathopod 2: basis with a row of setae along the anterolateral margin (length of most setae <40% of the basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width). Pereopods 5–7: propodus not expanded anteriorly. Uropod 1: ventral peduncular spinous process underlying about ¼ of the longest ramus. Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine). Telson: tip without apical setae (only the usual short setae at each dorsolateral cusp). Thumbed male: Antenna 2: large individuals with plumose setae on the flagellum and peduncular article 5. Gnathopod 2: propodus, palmar defining spines not produced on a ledge, present in small thumbed males but absent in large thumbed males. In minor males, the thumb is distally acute, short relative to body length and located on the distal half of the propodus. The dactyl is not centrally toothed. In major males, the thumb is distally acute, longer relative to body length and on the proximal half of the propodus. The dactyl is expanded close to the junction with the propodus but is not centrally toothed. Adult female: Antenna 2: large animals with plumose setae on the flagellum and peduncular article 5. Gnathopod 2: propodus, palm shallowly concave, palmar defining angle acute. Remarks. Smaller males and females lack the plumose setae on the distal parts of the antenna 2. The long filter setae on antenna 2 are absent or much shorter in the thumbed males than the females or juveniles. Large subadult males have some plumose setae on the flagellum but retain the long setae typical of juveniles and females on the peduncle (Figs 22–23). The long seta on the anterodistal margin of the gnathopod 1 carpus is usually visible, extending upright or away from the propodus. However, it may also lay flat against the medial face of the propodus, so it is necessary to check for its presence using a fine needle inserted into a rod for grasping or with needle-nosed forceps. Presence of this long seta (or setal cluster), along with lack of apical setae on the telson are key distinguishing characters for J. slatteryi of any size or sex, except from J. carltoni, which also has these character states. Differences from J. carltoni are more in the shape of the gnathopod 1 palm (straighter in J. slatteryi and concave in J. carltoni), the density of setae on the anterior margin of the basis of gnathopod 2 (more setae in J. slatteryi than J. carltoni) and in the shape and spination of the gnathopod 2 propodus: slenderer in the female of J. slatteryi with the defining spines tightly clustered and the major form male’s thumb always acute at the tip and not curved posteriorly, while in J. carltoni the female’s defining spines are more dispersed and the major form male’s thumb is more rounded at the tip and curved posteriorly. While J. slatteryi has been found on many coasts, J. carltoni is only known from the Pacific coast of North America. Jassa slatteryi also occurs on the Pacific coast of North America, however, though it has not been found in the same collections as J. carltoni. Asubset of the specimens described by Hong (1983) as J. falcata were lent for analysis for this study. They had been collected in Deukryang Bay, The Republic of Korea from a settling plate. Major forms ranged from 5.5 to 7.2 mm in body length while minor forms were 3.0– 6.2 mm (Fig. 24). Thumb length was less relative to body size in minor forms than major forms. Aplot of propodus length to body length for the same males, with addition of females from the Deukryang Bay population showed a longer propodus length relative to body length for the adult males than for the females, juvenile and subadult males (Fig. 25). For the adult males that overlapped in body length (5.58–6.41 mm), propodus length did not significantly differ between major and minor form (ANOVA, F = 0.211, p = 0.654, df = 14; major form propodus length 1.863 ± 0.122 mm, n = 7; minor form propodus length 1.830 ± 1.51 mm, n = 8). Lim and Park (2006) redescribed and illustrated a minor form of J. slatteryi from a collection taken from the screw of a ship in Samcheon-po bay on the south coast of The Republic of Korea. Rumbold et al. (2015a) examined J. slatteryi from Argentina both morphologically and with the CO1 gene, comparing it with J. marmorata and J. staudei. They also provided a photograph of live pigmentation of a subadult male and photographs of various body parts of a minor form thumbed male. Their Fig. 3I is the tip of the maxilliped palp, not the mandible as stated. Pilgrim & Darling (2010) found J. slatteryi, J. marmorata and J. staudei to be unique based on the CO1 gene. Aloan of J. slatteryi that was obtained after Conlan (1990) was of three samples at 11–24 m depth offshore of Rio de Janeiro and Ubatuba, Brazil in 1964–1966. This is the earliest known collection of J. slatteryi on the Atlantic coast of South America (Table 3). Conlan (1990) cited in error that J. slatteryi occurred in the Galapagos Islands, Ecuador, based on identification of 7 major form males, 3 adult females and 1 juvenile borrowed from the Swedish Museum of Natural History. The collection location was Cumberland Bay, Masatiera, but this is located in Robinson Crusoe Island, Chile (formerly Más a Tierra). The reference by Rumbold et al. (2015a) to J. slatteryi occurring in the Galapagos Islands is therefore also in error. Some other location errors in Conlan (1990) were also found when collections were re-examined for this paper as some specimens of “ J. slatteryi ” on the Pacific North American coast were unrecognized J. morinoi or J. carltoni. Corrected distributions indicate that both J. slatteryi and J. morinoi are indeed trans-hemispheric (Figs 3–6) yet also occur at remote locations along the Pacific North American coast, particularly in British Columbia. Jassa carltoni is only known from the Pacific coast of North America and is now known from British Columbia (Fig. 10; update of Conlan 1990). Intersexes, having characteristics of both females (setose brood plates) and males (penial papillae and thumbed second gnathopods) were found in Santa Ynez, Eureka Harbor, and Morro Bay, California, Tanabe Bay, Japan and Adelaide, Australia (Fig. 26). The intersexes had small thumbs which could differ in size between right and left gnathopod. Two species described after the revision by Conlan (1990) are submerged under J. slatteryi: J. cadetta Krapp et al., 2008 and J. trinacriae Krapp et al., 2010. Jassa cadetta was described by Krapp et al. (2008) based on specimens collected in algae at shallow depth in the Venice Lagoon, Malamocco, Italy (~ 45°22′18ʺN, 12°20′15ʺE). These had a different karyotype and morphology than J. marmorata, which was also found there, and therefore was designated a new species. The possibility that J.cadetta could be J. slatteryi was not considered by the authors, but examination of the types lent by the Museo Civico di Storia Naturale di Verona, Italy showed that their morphology was unmistakeably that of J. slatteryi (Supplementary data file S2). Both J. marmorata and J. slatteryi are common inhabitants of fouling communities in populated areas such as Venice Lagoon (Table 4). Jassa trinacriae was described based onspecimens collected at Grotta Conza, Sicily (~ 38°11′14″N, 13°16′57″E), at the northern end of the Conca d’Oro, a cave of about 90 m length, 175 m above sea level, and 1 km distant from the sea. Presumably the specimens were in saline water as Jassa is not known from fresh water (Table 4). Additional specimens collected in 1952 from Sampieri, Sicily were also ascribed to this species by Krapp et al. (2010). Aloan of these individuals fromthe same museum as for J. cadetta allowed confirmation that all specimens were clearly J. slatteryi (Supplementary data file S3). Therefore, J. trinacriae is submerged. These specimens are the earliest collection known for the Mediterranean, since the record for Rovinj, Croatia noted in Conlan (1990) had no collection date (Table 3). Navarro-Barranco etal. (2015), Fernandez-Leborans etal. (2016), Fernandez-Gonzalez & Sanchez-Jerez (2017) and Bonifazi et al. (2018) document other Mediterranean locations where J. slatteryi has been confirmed. Krapp et al. (2010) also described a Jassa sp. from a thermal spring in Fordongianus, Sardinia where the water was 45 °C (54–58 °C at the origin of the spring). Angelone et al. (2005) reported an electrical conductivity of 1,547 µS cm-1, pH 8.40 and Eh 259 mV in this spring, which is in range of that found in seawater. Fordongianus is about 20 km east of the Sardinian west coast. This specimen was also borrowed from the Museo civico di Storia Naturale di Verona, Italy and examined (Supplementary data file S4). Its immature appearance and small size (2.2 mm length) suggest that it is a hatchling. If indeed a species of Jassa, this would be the warmest water recorded (Table 4). The specimenwasslidemountedandthereforecouldnotbemanipulatedtoviewallbodyparts. Conclusivedetermination would require specimens at a more advanced age.Published as part of Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1) on pages 54-60, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/458062
Pleojassa Conlan 2021, n. gen.
No full textGenus Pleojassa n. gen. Description of male. Maximum body length 10.8 mm. Head lobe: squared, dorsal angle more acute, lower angle lobe more rounded. Antenna 1: accessory flagellum 2 articles, the second minute, setose only distally. Antenna 2: stouter and longer than antenna 1, setation variable, filter setae shorter and sparser in larger individuals, flagellum spination variable, first article considerably longer than following articles. Maxilla 1: inner plate bearing a few short, fine setae; palp without setae at the base of article 1, article 2 with 1 row of facial setae. Gnathopod 1: coxa rectangular; carpus, anterior margin length <propodus length; propodus, palm defined by 1–2 medial defining spines, this central or slightly proximal of centre; dactyl facially striated. Gnathopod 2: without a gill; coxa not deeper posteriorly; basis without filter setae; carpus a quarter of propodus length or less, lobe apically setose; propodus without anteroproximal setae, hinge tooth rectangular cuboid or conical, shallowly or deeply bifid, or multiply incised, palm concave to the single medial defining spine, there produced or not into a short “hook” or long thumb; dactyl shorter than the propodus, variably expanded at the hinge tooth, tip apposing the defining spine, or if thumb present, its posterior margin, cusps reduced and interspersed with short setae. Pereopod 3: coxa deepest centrally or slightly posterior of centre; basis a little slenderer in larger individuals; merus, anterior margin bearing well-spaced single or clustered setae; carpus, overlap by merus variable; propodus not posteriorly spinose. Pereopods 5–7: basis variably posterodistally produced or not produced, anterior margin spinose or setose; merus not posterodistally spinose; carpus with a cluster of spines posterodistally at least on pereopod 5; propodus not strongly expanded anteriorly; dactyl not facially serrated, posterior (outer) margin not cusped distally, anterior (inner) margin, setation variable. Pleopods: rami very short, length ± depth of the pleon, each with 2 coupling hooks. Urosome: segment 1 with dorsal pair of erect setae. Uropod 3: peduncle mid-ventrally setose, without mid-dorsal spines, but with a crown of spines dorsomedially at the insertion of the rami and a cluster of setae distolaterally; outer ramus not setose mid-dorsally, tipped by a basally immersed, dorsally recurved spine and associated seta and serrations, cusps variable, but never as on Jassa; inner ramus with or without a spine or spines mid-dorsally in addition to the single apical spine. Telson: each dorsolateral corner with a pair of cusps accompanied by setae (2 long, simple, and 2 short, plumose) but not spines. Description of adult female. Maximum body length 9.8 mm. Character states as in the male except as follows. Brood plates: broad, setae well separated, abundant, at least some hook-tipped. Antenna 2: peduncle, posterior filter setae long, not shorter in larger individuals. Gnathopod 2: propodus much larger and different in shape from propodus of gnathopod 1, palm concave, defined by a single medial spine and without a thumb; dactyl tip apposing the defining angle and spine, dactyl cusps strong. Pereopod 3: basis somewhat broader than in the male. Variation. Antenna 2 peduncular setal change appears to be similar to that of Jassa, with the male’s setae shorter in larger specimens and the female’s remaining long. Male gnathopod 2 thumbing is not homologous, however, because the thumb develops at the palmar defining spine rather than distal to it. Consequently the thumb’s setation pattern is quite different. Type species. Jassa wandeli Chevreux, 1906. Included species. Pleojassa wandeli (Chevreux, 1906), P. multidentata (Schellenberg, 1931), P. moorei n. sp., P. lowryi n. sp. and P. orientalis n. sp. Remarks. Distinguishing features from Jassa are a single spine defining the palm of gnathopod 2, and hence different thumb setation, closure of the second gnathopod’s dactyl at, rather than distal to, the defining spine, lack of a gnathopod 2 gill, reduced pleopods and lack of a double cusp on the uropod 3 outer ramus. The males of P. wandeli and P. multidentata produce a long thumb if sufficiently larger than the adult female and thus would superficially appear to be a Jassa. Thumb development appears from specimens to be a progressive transformation, not at a terminal molt, however (although this has not been tested experimentally as it has for Jassa). Males of P. orientalis probably also produce a thumb as this species closely resembles P. multidentata. Pleojassa moorei and P. lowryi are not known to produce thumbs in the males and sufficient specimens were available to find males of similar or larger size than adult females to indicate that the males were adult as well. However, the five species resemble each other in characters that are conservative within Jassa, such as the tendency toward setal reduction in the antenna 2 of the male compared to the female, and in similar morphologies of the mouthparts, gnathopod 1, female gnathopod 2, female brood plates and third uropod hooking. Key to World species of Pleojassa (both sexes) 1 Uropod 1, posteroventral peduncular spinous process nearly as long as the outer ramus. Gnathopod 1, carpus without a seta at the anterodistal junction of the propodus. Female gnathopod 2, palmar setae not densely plumose (Fig. 22)....................................................................................................... P. moorei n.sp. - Uropod 1, posteroventral peduncular spinous process ½ to ¾ the length of the outer ramus. Gnathopod 1, carpus with or without a single seta or cluster of setae at the anterodistal junction of the propodus. Female gnathopod 2, palm bearing abundant plumose setae (Figs 27 and 28).......................................................................... 2 2 Pereopods 3 and 4, carpus nearly fully overlapped by the merus (Fig. 25). Female body size at maturity 2.5–5.1 mm. Gnathopod 2, propodus, palm densely plumose in both sexes; larger male ~ 3 mm body length or more, palm defined by a small hook but not by a thumb (Fig. 25)..................................................................... P. lowryi n.sp. - Pereopods 3 and 4, carpus 1/2 to 3/4 overlapped by the merus (Figs 27–29). Female body size at maturity 5.9–9.8 mm. Gnathopod 2, propodus, only the female palm densely plumose; larger male ~ 6 mm body length or more, palm defined by a thumb (Fig. 30)............................................................................................ 3 3 Female gnathopod 2, propodus, dactylar hinge tooth shallow (Fig. 33). Antenna 2, large male and female, posterior margin of article 5 and flagellum plumose (Fig. 33)............................................ P. wandeli (Chevreux, 1906) - Female gnathopod 2, propodus, dactylar hinge tooth deep (Figs 27 and 28). Antenna 2, adult female and comparably sized male, posterior margin of article 5 and flagellum not plumose (Figs 27 and 28)......................................... 4 4 Gnathopod 1, carpus with a single or cluster of setae at the anterodistal junction of the propodus (Fig. 27). Known only from South Georgia (Fig. 2)..................................................... P. multidentata (Schellenberg, 1931) - Gnathopod 1, carpus without a single or cluster of setae at the anterodistal junction of the propodus (Fig. 28). Known only from Macquarie Island (Fig. 2).................................................................. P. orientalis n. sp.Published as part of Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1) on pages 37-39, DOI: 10.11646/zootaxa.4921.1.1, http://zenodo.org/record/449601
Jassa morinoi Conlan 1990
No full textJassamorinoi Conlan, 1990 (Table 10, Figs 28–30) Diagnosis. Both sexes: Mandibular palp: article 2, dorsal margin without a fringe of setae. Maxilla 1: without a seta or setal cluster at the base of the palp article 1. Gnathopod 1: basis, anterolateral margin with a few short setae at the distal angle; carpus with a single or small cluster of long setae at the anterodistal junctionof the propodus (setae Ẑ50% the length of the anterior margin length andslightly medial). Gnathopod 2: basis with about 5–10 widely spaced, short setae along the anterolateral margin (length of most setae <40% of the basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width). Pereopods 5–7: propodus not expanded anteriorly. Uropod 1: ventral peduncular spinous process underlying about 1/3 of the longest ramus. Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine). Telson: tip with apical setae in addition to the usual short setae at each dorsolateral cusp. Thumbed male: Antenna 2: without plumose setae on the flagellum and peduncular article 5. Gnathopod 2: propodus, palmar defining spines pronounced and produced on a ledge in large minor form males. Palmar defining spines absent in major form males. Thumb distally acute in both minor and major males and sinuous in major males. The dactyl is proximally expanded but not centrally toothed in minor forms. Adult female: Antenna 2: without plumose setae on the flagellum and peduncular article 5. Gnathopod 2: propodus, palm concave, palmar defining angle acute. Remarks. Jassa morinoi, J. valida and J. monodon are unique among the species of Jassa in having a seta or group of setae at the tip of the telson which extend between the third uropods as a horizontal extension of the body. This apical seta or setae can be most easily seen when the third uropods are held downward. The apical setae should not be confused with the usual upright seta or setae that accompany each telson knob on each lateral edge in every species of Jassa. The three species can be told apart by the length (if present) or absence of the diagnostic seta or cluster of setae at the anterodistal junction of the carpus and propodus of gnathopod 1. This seta or setal cluster is slightly medial in J. morinoi and J. valida and absent in J. monodon. Care must be taken to twist the gnathopod 1 to check for this seta on the medial face of the propodus as it may lay flat against the propodus and therefore be obscured from view. This seta or setal cluster is long in J. morinoi (length as great as the width of the gnathopod 1 basis) but much shorter in J. valida, to the extent that it may not be visible at low magnification (length << the width of the gnathopod 1 basis). Jassa morinoi can also be confused with J. slatteryi as both can co-occur in collections and both have the long seta(e) at the anterodistal junction of the carpus and propodus of gnathopod 1. The key character separating these species at any age or sex is the presence of the apical seta or setae on the telson in J. morinoi and absence in J. slatteryi. Jassa morinoi has been found widely, dating as far back as 1885 in the Mediterranean Sea (Table 3). An illustration of two specimens of Jassa (named “ J. falcata ”) by Ledoyer (1986), collected from Madagascar (Thomassin st. 270, microatolls of Sarodrano, 23°30′30ʺS, 43°44′00ʺE) and Thomassin st. 263, microatolls of Songoritelo, 23°14ʹS, 43°37ʹE) shows key features that suggest that the specimens are J. morinoi (telson tip with long setae, gnathopod 2 basis with sparse setae, male antenna 2 flagellum not plumose). However, the long seta(e) at the junction of carpus and propodus of gnathopod 1 is not shown or described, leaving the identification suggestive but not certain. Jassa morinoi is known from neighbouring South Africa. The earliest collection record for J. morinoi on the coast of Pacific North America is 1909 near the (then) remote village of Ucluelet on British Columbia’s exposed outer coast of Vancouver Island. It may be indigenous on the Pacific North American coast because it has been found frequently on exposed coasts away from harbours. For this study, it is known from 38 Pacific North American collections, ranging from Athlone Island, British Columbia (52°N) to Santa Catalina Island, California (33°N). Some “ J. slatteryi ” listed in Conlan (1990), from Pacific North America were found to be mis-identified and were actually J. morinoi. However, re-examination of the entire NMNS/CMN collection of “ J. slatteryi ” found that J. slatteryi does indeed occur on this coast and the two species can be found mixed together in aggregate collections. The re-examination of the NMNS/CMN collection also revealed that some of the major form males previously thought to be J. slatteryi were actually J. morinoi. Illustrations of some of these newly found major forms have been added to Fig. 28 along with the minor form male previously thought to be a major form in Conlan (1990). Therefore, like most of the other species of Jassa, the major form of J. morinoi can lose its palmar defining spines, although this does not always happen, as shown in Fig. 28. Afirst discovery of “ J. morinoi ” in the southwestern Gulf of Mexico by Winfield et al. (2021) is questionable as it is more likely J. valida (Supplementary Data File S1). It is apparent from their identification criteria that they were not aware of the key character that separates the species (setal length at the anterodistal junction of carpus and propodus). Winfield et al. (2021) were also identifying relatively small specimens (3.03 ± 0.46 mm body length, n = 3) which may have been difficult to manipulate in order to view this seta. It was not possible to borrow the specimens to confirm the identification as the museum collections were closed due to the COVID-19 pandemic. Specimens of J. morinoi noted in Conlan (1990) as lent by Dr. H. Morino, Ibaraki University, Japan, have been recently transferred to the National Museum of Nature and Science, Tsukuba, Japan. This includes the type specimens (Morino 2019).Published as part of Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1) on pages 60-64, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/458062
Pleojassa orientalis Conlan 2021, n. sp.
No full text<i>Pleojassa orientalis</i> n. sp. <p>(Fig. 28)</p> <p> <b>Description of adult female.</b> Holotype: Length 9.8 mm.</p> <p> <i>Antenna 2</i>: overlapped by antenna 1 to the end of article 5; article 5, posterior margin bearing long simple setae only, without plumose setae; flagellum 3 articles, article 1 89% of the full flagellum length.</p> <p> <i>Mandible</i>: palp articles 2 and 3 without a dorsal fringe of setae; raker spines, number not measured.</p> <p> <i>Gnathopod 1</i>: coxal margins, anterior 140% of dorsal length; ventral margin shallowly convex; basis, anterior margin with a few short setae distally, posterior margin not setose; carpus, length 75% of propodus length, posterior lobe 59% of anterior margin length, without an anterodistal setal cluster; propodus, palm convex, with two defining spines slightly proximal of centre.</p> <p> <i>Gnathopod 2</i>: coxal margins, anterior 44% and posterior 73% of ventral length; ventral margin shallowly concave; carpus less than 1/4 the length of propodus; propodus, hinge tooth large and conical, not anteriorly bifid, palmar setae plumose, distributed throughout the palm, but not so dense as to obscure the palm’s shape, palmar angle acute, with a single, minute spine at its corner; dactyl, inner margin slightly sinuous.</p> <p> <i>Pereopod 3</i>: coxa, greatest depth posterior of centre; basis, anterior margin shallowly convex; merus, anterior marginal setae in well separated clusters, central setae, length 1/2 or less the article width, article width 72% of length; carpus 42% overlapped by merus; propodus, width 48% of length.</p> <p> <i>Pereopods 5–7</i>: setae and spines moderately abundant, basis posterodistally produced, anterior margin spinose; merus, posterior margin not spinose.</p> <p> <i>Uropod 1</i>: peduncle, posteroventral spinous process underlying 52% of the inner ramus, inner and outer rami with 10 and 6 mid-dorsal spines respectively.</p> <p> <i>Uropod 2</i>: peduncle, posteroventral spinous process underlying 42% of the inner ramus.</p> <p> <i>Uropod 3</i>: inner ramus with 2 spines mid-dorsally.</p> <p> <b>Condition.</b> Without left pereopod 5 and right pereopod 6. Flagellum of right antenna 1 lacking terminal article(s). Right appendages, left pereopod 6, and telson slide mounted.</p> <p> <b>Description of male.</b> Allotype: Length approximately 6.5 mm; head to end of segment 6, 3.9 mm. Character states as in the female except as follows.</p> <p> <i>Antenna 2</i>: article 5, filter setae half or less the length of those in the female, interspersed with plumose setae.</p> <p> <i>Gnathopod 2</i>: as in the female, but palm less densely setose and dactyl inner margin straight.</p> <p> <b>Condition.</b> Without body segments posterior of segment 6, antennae 1 flagella, left antenna 2 distal flagellum, right antenna 2, left pereopods 5–7, and right pereopods 5 and 7.</p> <p> <b>Variation.</b> Maximum body length: male unknown, female 9.8 mm. The male is 2/3 the body length of the adult female holotype (judging by relative difference in head length). This suggests that this male may not yet be mature, so it cannot be assumed that larger males lack a thumb as illustrated for the smaller male. Due to lack of material, sexual variation and growth is not well known and only can be inferred from congeners. Judging by its close resemblance to <i>P. multidentata</i>, in which the male is known to grow a thumb, this development is probably similar in <i>P. orientalis</i>. The small male bears plumose setae on the antenna 2 while the adult female lacks plumose setae. However, as in <i>P. wandeli</i>, larger females may have plumose setae.</p> <p> <b>Type material examined.</b> Holotype, ♀, ovigerous (AM), type no. P.34955, station no. MA-147, Macquarie Island: Gorilla Head Rock, southeast corner (54 o 29ʹS, 158 o 58ʹE), 23 December 1977, in a small <i>Durvillea antarctica</i> holdfast, 8 m. Allotype, small (juvenile?) ♂ (AM), type no. P.37924, same location. Paratype, juvenile ♀ (AM), type no. P.37925, same location.</p> <p> <b>Etymology.</b> In reference to the eastern location of the species relative to <i>P. multidentata</i>.</p> <p> <b>Remarks.</b> <i>Pleojassa orientalis</i> differs from <i>P. multidentata</i> in the shape of the gnathopod 2 palm (both sexes) (Figs 27 and 28), and in lacking a cluster of short setae at the anterodistal margin of the carpus of gnathopod 1, which is present in <i>P. multidentata</i>. <i>Pleojassa orientalis</i> may prove to be a geographic variant of <i>P. multidentata</i>, given the wide longitudinal range that Southern Hemisphere species can have (Figs 1 and 2). They are given separate species status herein because these morphological differences are key characters for distinguishing species in <i>Jassa</i> (Conlan <i>et al.</i>, in press) and this may be the same case in <i>Pleojassa</i> and other relatives of <i>Jassa</i>.</p>Published as part of <i>Conlan, Kathleen E., 2021, New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini, pp. 1-72 in Zootaxa 4921 (1)</i> on pages 48-49, DOI: 10.11646/zootaxa.4921.1.1, <a href="http://zenodo.org/record/4496015">http://zenodo.org/record/4496015</a>
Jassa myersi Conlan 1990
No full text<i>Jassamyersi</i> Conlan, 1990 <p>(Table 12, Figs 85–87)</p> <p> <b>Diagnosis.</b></p> <p> <b>Both sexes:</b></p> <p> <i>Mandibular palp</i>: article 2, dorsal margin without a fringe of setae.</p> <p> <i>Maxilla 1</i>: without a seta or setal cluster at the base of the palp article 1.</p> <p> <i>Gnathopod 1</i>: basis, anterolateral margin with a few short setae along its length; carpus with a single or small cluster of relatively long setae at the anterodistal junction of the propodus (setal length about 1/3 the length of the anterior margin length).</p> <p> <i>Gnathopod 2</i>: basis with only a few short setae along the anterolateral margin (setal lengths <20% of the basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width).</p> <p> <i>Pereopods 5–7</i>: propodus not expanded anteriorly.</p> <p> <i>Uropod 1</i>: ventral peduncular spinous process very short, underlying about 6% of the longest ramus.</p> <p> <i>Uropod 3</i>: inner ramus without spines mid-dorsally (with only the single apical spine).</p> <p> <i>Telson</i>: tip without apical setae (only the usual short setae at each dorsolateral cusp).</p> <p> <b>Thumbed male:</b></p> <p> <i>Antenna 2</i>: without plumose setae on the flagellum and peduncular article 5.</p> <p> <i>Gnathopod 2</i>: propodus, palmar defining spines not produced on a ledge.</p> <p> <b>Adult female:</b></p> <p> <i>Antenna 2</i>: without plumose setae on the flagellum and peduncular article 5.</p> <p> <i>Gnathopod 2</i>: propodus, palm sinuous, palmar defining angle shallowly rounded and towards the centre of the palm (not close to the palmar defining spines).</p> <p> <b>Remarks.</b> This is the only Northern Hemisphere species that has a sinuous palm on the propodus of gnathopod 2. It also has a variably fringed basis, leading to mixed interpretation of whether a fringe of setae is present or absent. It shares with <i>J. borowskyae</i> and <i>J. shawi</i> a reduced peduncular process underlying the rami of uropod 1. Among the 166 specimens available for study, there were only 8 thumbed males. These all had very short thumbs and palmar defining spines proximal to the base of the thumb. The thumbed males had shorter setae on the antenna 2 than the females (Fig. 85) but none had plumose setae as develops in thumbed males of some other species of <i>Jassa</i>. This may signify that <i>J. myersi</i> does not develop plumose setae but the sample size is small. However, none had slenderized bases of pereopods 3–4 which is typical of large thumbed males. Conlan (1990) suggested, therefore, that these males were not at maximal size for the species. Aplot of gnathopod 2 propodus length relative to body length shows an apparent greater size for males than females (Fig. 87). Analysis of variance on adult females (<i>n</i> = 4) and juvenile males (<i>n</i> = 6) that overlapped in body length (3.5–4.5 mm) found that the differences in mean propodus length was not sufficiently great to exclude the possibility that the difference was due to random sampling variability (<i>F</i> = 1.041 -15, <i>p</i> = 1.0).</p> <p> <b>Southern Hemispherespecies</b></p>Published as part of <i>Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1)</i> on pages 133-137, DOI: 10.11646/zootaxa.4939.1.1, <a href="http://zenodo.org/record/4580622">http://zenodo.org/record/4580622</a>
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