111,972 research outputs found
Telestula ridgensis Periasamy & Kurian & Ingole 2023, sp. nov.
No full textTelestula ridgensis sp. nov. Figs 1–8 Type material: holotype: Specimen, NCPOR /HYD-CIR/0048, Seamount of the Central Indian Ridge, Indian Ocean, R / V ‘ MGS Sagar’ cruise MGS–35 (Station MGS-35A-BD21), 24 April 2020, 23°10′28.92′′ S, 69°32′47.04′′ E, 1917 to 2053 m, Benthic Sledge, Coll. Periasamy R, samples in 90% ethanol. Paratypes: One specimen NCPOR /HYD-CIR/0049 from the same locality as the holotype. Ecological note: The specimen was collected along with two types of carnivorous sponges; three types of deepsea coral, three types of brittle stars, shrimps; and dead gastropod shells from medium-grained basalt rocky bottom with thick Fe-Mn crust. Coloration: The color of colonies ranges from yellowish-brown to dark brown or black; with their ends forming white or cream polyps. Distribution: Telestula ridgensis sp. nov. is known only for its type locality in the seamounts of the Central Indian Ridge system. Etymology: The specific name refers to the type locality of the Indian Ocean Ridge. Gender is feminine. Description Coral colonies are inter-connected with polyps by ribbon - like stolon expanding in irregular patterns on the surface of a dead coral (Fig. 2A), and budding of secondary polyps (Fig. 2C). The polyps arise from a ribbon - like stolon (0.6 mm in width). The holotype is about 19.7 mm tall and 0.2 mm in diameter, with eight polyps attached (Fig. 2D). Fully retracted polyps are up to 12 mm in height and 1.5 mm in width. Sclerites in the polyp (Fig. 3A,B,C) form a thick layer in the calyx wall region, being longitudinally arranged and tightly packed (Fig. 3D). The stolon is ribbon-shaped, with sclerites longitudinally arranged along the thin basal stolon (Fig. 3E). The sclerites in the tentacles and middle of the neck zone are transversely set (Fig. 4A, B,C). Tentacles sclerites are narrow and stellate plates; cross-like forms with slightly tubercular ornamentation; stellate plates (0.19– 0.06 mm long 0.08– 0.02 mm wide); cross-like sclerites (0.058 –0.082 mm long 0.047 –0.064 mm wide); smaller crosses, all of them with tubercular ornamentation (Fig. 5A). Pharyngeal sclerites are small warty plates (0.07–0.13 mm long, 0.010 –0.032 mm wide) (Fig. 5B). Neck zone sclerites are short, blunt rods, crosses with tubercular ornamentation; 0.16– 0.07 mm in length, 0.05– 0.01 mm wide; some crosses (Fig. 6A). I ntrusion sclerites are irregular-shaped, branched rods with tubercular ornamentation (0.14–0.52 mm long, 0.03–0.11 mm wide) (Fig. 6B). Calyx wall sclerites are irregular-shaped; crosses with dense tubercular ornamentation (0.45– 0.15 mm long 0.37– 0.06 mm wide); frequently with cross-like prominences (Fig.7A). Stolon sclerites are smooth to slightly warty plate,crosses; irregular-shaped with slightly tubercular ornamentation (0.40– 0.19 mm long 0.42– 0.02 mm wide); less cross-shaped forms (0.12– 0.25 mm long) (Fig. 7B). Remarks. The sclerome found in Telestula ridgensis sp. nov. is unique among the north-eastern Atlantic congeners having longitudinal rows of small warty rods and cross-like forms that extend from the distal end of the calyx towards the base of the tentacles. The sclerites of the new species from the neck zone, intrusion tissue, calyx wall, and ribbon-like stolon are notably different among the genus Telestula with an evident abundance of warty, irregular, and cylinder-like forms of small flattened ovals. Telestula ridgensis sp. nov. is morphologically closely related to Telestula septentrionalis, T. cf. batoni , and T. cf. spiculicula . According to Tixier-Durivault (1964) species, T. tubaria has eight chevrons of small sclerites in the neck region and eight longitudinal ridges of sclerites in a calyx wall. However, T. versluysi has densely tuberculate rounded spindles from the calyx wall and irregular spindles from the stolon (Weinberg 1990). T. mosaica has some arrowhead-like sclerites. The sclerites of T. kuekenthali have loose polyps, plump, coarsely tuberculate spindles from the calyx wall, irregular spindles, and cross-shaped sclerites from the top of the polyp (Weinberg 1990 ). Telestula stocki has plates on top of tentacles, sparse long spindles, warty spindles with complex tubercles, rods from stolon, and plump (Weinberg 1990).Published as part of Periasamy, Rengaiyan, Kurian, Palayil John & Ingole, Baban, 2023, A new deep-water coral species Telestula ridgensis sp. nov (Scleralcyonacea: Sarcodictyonidae) from the seamount of theCentral Indian Ridge, pp. 231-244 in Zootaxa 5254 (2) on pages 233-238, DOI: 10.11646/zootaxa.5254.2.4, http://zenodo.org/record/772729
New Records of Thecacineta cothurnioides and Trematosoma rotunda (Ciliophora, Suctorea) as epibionts on nematodes from the Indian Ocean
No full textThis article deals with the report of two suctorian ciliates species viz. Thecacineta
cothurnioides Collin, 1909 and Trematosoma rotunda (Allgén, 1952 ) as epibionts
on Tricoma sp. and Pseudochromadora sp. (Nematoda) respectively from Ratnagiri,
west coast of India, Arabian Sea (Indian Ocean). Redescription of two species with
distribution and nomenclatural notes are given. Both species are recorded here first
time from Indian coast and the Indian Ocean. Genus Tricoma Cobb, 1894 is also
recorded here first time as a host of Th. cothurnioides
Munidopsis parvatee Periasamy & Kurian & Ingole 2023, sp. nov.
No full textMunidopsis parvatee sp. nov. Fig 2–4 Material examined: female holotype: NCPOR /HYD–CIR/0048, ♀ (CL 14.2 mm, PCL 10.4 mm) Central Indian Ridge, Indian Ocean, R / V ‘ MGS Sagar’ cruise MGS35 (Station no: MGS35B– BD25), 27 April 2020, 24° 42′ 47.88′′ S, 70° 1′ 54.12′′ E, 1981 to 2033 m, Benthic Sledge, Coll. Periasamy R, samples in 90% ethanol. Paratypes: One specimen NCPOR /HYD–CIR/0049 from the same locality as the holotype. Ecological note: The specimen was collected along with three types of deep-sea corals, two types of brittle stars, shrimps, dead Gastropod shells, and Isopods from a basalt rocky bottom. Coloration: The yellow-orange base colour of the body. Distribution: Seamount is located near the Edmond vent field, Central Indian Ridge (CIR), in a depth range of 1981–2033 meters. Etymology: The species name “ parvatee ” is a Hindi word given based on its habitat i.e., seamount. parvatee means belong to the mountain. Description: The carapace (without rostrum) is approximately 1.34 times as long as broad. Frontal margins are tilted. Lateral margins are feebly convex, each with three to six prominent spines; small anterolateral spine; one or two spines on the anterior branchial margin; one to three spines on the posterior branchial margin (spine on the lateral base of posterior cervical groove strongest; posterior one or two spines usually reduced); scale-like tubercles and short ridges present among spines; especially on posterior branchial margin. Posterior margin ridged, and tubercles laterally. Dorsal surface with regions clearly defined; covered with numerous tubercles; tubercles fairly scale-like on posterior branchial region; conical on anterior branchial; cardiac and gastric regions. Six pairs of strong spines are present along the dorsal midline: three pairs of spines in the gastric region; two pairs of spines in the cardiac region (each in the anterior and posterior cardiac region); and one pair of very small spines on the intestinal region (Figure 2A). The gastric region is somewhat eminent. The cervical groove is different (Figures 2 & 3). Rostrum distinctly elongate; flat; and dagger-shaped; 0.5 times as long as the remaining carapace length; 4 times longer than broad; narrow; horizontal; dorsal surface covered with rugae (fine serrations); weakly depressed proximally (Figures 3A). Eyestalk movable. Cornea oval; globular; cupped in the anterolateral end of the ocular peduncle. Ocular peduncle without eye spine; reaching proximal 0.2 of the rostrum (Figures 3A). The pterygostomial flaps with broad tubercles on the lateral surface; anterior end blunt (Figure 3B). Abdominal tergites unarmed; tergites 2 and 3 each with two transverse ridges medially connected and laterally separated by deep grooves; lateral part of dorsal surfaces smooth (Figures 3H). Sternal plastron longer than broad (Figure 3D). Sternite 3 is 1.5 times broader than long; divided into two parts by a median groove; anterior margin serrated; with acute anterolateral spines. Sternite 4 three times broader than long; anterolateral surface depressed and sloping anteriorly. Sternites 5–7 medially grooved; separated from one another with elevated; transverse ridges (Figure 3D). Antennal peduncle stout; reaching at least proximal half of rostrum. Article 1 immovable; with a short distomesial spine. Article 2; article 3; and article 4 unarmed (Figure 3A). Antennular peduncle with basal article longer than broad; distal margin armed with strong ventrolateral and dorsolateral (rarely with affiliated spine) spines; lateral face inflated; ventral surface with short rugae (Figure 3C). Third maxilliped stout; ischium slightly longer than broad; approximately 0.5 times merus length; distoflexor corner acute; crista dentata well developed. Merus longer than broad; extensor margin rugose; flexor margin with small median spines and strong proximal process (divided into two spines); ventral surface with rugae. Carpus short; unarmed. Propodus with distoflexor margin convex (Figure 3F&G). Telson is composed of eight separate plates; covered with scale-like tubercles (Figure 3G). P1 subequal; distinctly elongate; 5 times PCL; each segment covered with numerous scale-like tubercles longitudinally arranged on surfaces and margins and bearing fine setae. Ischium with strong dorsodistal spine; ventrodistal margin anteriorly produced. Merus approximately 1.8 times PCL; distal margin with strong dorsal; mesial; ventral; and lateral spines; dorsodistal spine followed by a row of spines; distomesial spine strongest; followed by two or three slender spines; ventrodistal spine followed by two or three spines (usually on proximal half) along the midline of the ventral surface. Carpus approximately 0.6 times merus length; distal margin with strong dorsal; mesial and lateral spines; dorsodistal spine followed by spines and pointed tubercles; distomesial spine occasionally followed by few spines. Palm is relatively compressed; approximately 0.6 times merus length; 5 times as long as broad; mesial margin with a row of small spines or pointed tubercles. Fingers 0.5 times palm length; slightly spooned distally; occlusal margins straight and denticulate; bearing fringe of simple setae; with several triangular teeth on a movable finger (Figure 4A–D). P2 –4 slender, sparsely setose; P2 approximately 2.2 times PCL; falling short of distal margin of P1 merus; lateral surfaces of Ischia; meri; carpi; propodi covered with scale-like tubercles. Meri compressed; subequal in breadth but decreasing in length posteriorly; P2 merus approximately 0.8 times of PCL and 5 times as long as broad; P3 merus 1-time P2 merus length; P4 merus 0.7 times P2 merus length; extensor margin tuberculate; armed with a strong distal spine; flexor margin tuberculate; without a distinct spine. Carpi subequal in length; approximately 0.5 times P2 merus length; extensor surface with two longitudinal ridges each covered with scale-like tubercles and armed with a distinct distal spine; spine on mesial ridge much more prominent; flexor margin unarmed. Propodi subcylindrical; subequal in length and breadth; approximately 1-time P2 merus length and 6.5 times as long as broad; extensor margin with scale-like tubercles; flexor margin with four or five movable corneous spines on distal half; including distal pair. Dactyli slender; narrowing distally; approximately 0.5 times propodus length; flexor margin straight; with 12 or 13 movable corneous spines (spines on median part much larger) on the entire length; and distal spine closely appressed to claw; each corneous spine located on elevated base (Figure 4E). Pereopods without epipod. Egg diameter 2 mm (Figure 2D). Remarks: The new species from CIR is the closest to Munidopsis guochuani Dong, Gan & Li, 2021 known from the seamount on the Caroline Plate, West Pacific Ocean. The new species from CIR can be differentiated from M. guochuani by carapace posterior margin ridged, with a row of spines on median part and tubercles laterally (Dong et al. 2021, Figure 21A), without a row of spines on median part (Figure 3A), the shape of the sternite 3 and 4 in the sternal plastron, and seven distinct plates in telson. Genetic data. DNA sequencing for this species was successful for mtCOI gene (Accession numbers: COI: OP311614). The average K2P distance between the closely related M. guochuani (MT901058) and the CIR specimen was 0.07% for COI.Published as part of Periasamy, Rengaiyan, Kurian, Palayil John & Ingole, Baban, 2023, Two new deep-water species of squat lobsters (Crustacea: Anomura: Galatheoidea) from the Central and Southwest Indian Ridge, pp. 165-178 in Zootaxa 5231 (2) on pages 167-170, DOI: 10.11646/zootaxa.5231.2.3, http://zenodo.org/record/757527
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Typhlonida milindi Periasamy & Kurian & Ingole 2023, sp. nov.
No full text<i>Typhlonida milindi</i> sp. nov. <p>Figs 5–7</p> <p> <b>Material examined:</b> Female holotype: NCPOR /HYD-CIR/0048, ♀ (CL 8.6 mm, PCL 3.2 mm), Seamount of the Southwest Indian Ridge, Indian Ocean, <i>R / V</i> ‘ <i>MGS Sagar’</i> cruise MGS35 (Station No: MGS35C–BD5A), 02 April 2020, 26° 21′ 10.8′′ S, 67° 41′ 27.6′′ E, 2070 to 2404 m, Benthic Sledge, Coll. Periasamy R, samples in 90% ethanol.</p> <p> <b>Ecological note:</b> The specimen was collected along with associated benthic communities of deep-sea fish, glass sponge, and coral in the ferromanganese (Fe–Mn) covered basalt rocky with a thickness of 2–4 cm.</p> <p> <b>Distribution:</b> <i>Typhlonida milindi</i> <b>sp. nov.</b> is known for its type locality in the seamount of the SWIR.</p> <p> <b>Etymology</b>: It is named in honor of our senior scientific colleague <i> — <i>Late Dr. Milind Wakadikar</i>,</i> who contributed diligently to accomplish the objectives of the Indian deep-sea mission, especially the deepsea hydrothermal exploration program.</p> <p> <b>Description:</b> Moderately small species, carapace as long as the width. Dorsal surface with main transverse ridges, without secondary transverse striae between main ridges, and striae lined with short; non-iridescent setae. Epigastric region with 2 pairs of spines, without a median row of spines behind the rostrum. Cervical groove deep; a hepatic region without spines on the dorsal surface. The anterior part of the branchial region between the cervical groove and post-cervical groove with 2 or 3 short tuberculate ridges and often 1 small spine anteriorly, posterior part of the branchial region with 5 transverse ridges excluding posterodorsal ridge. The cardiac region with 2 main transverse ridges. An intestinal region without striae; posterodorsal ridge distinct; without secondary stria. Front margin oblique; inclined posteriorly at 115° from the midline. Lateral margin slightly convex; anterolateral spine very small; far from reaching sinus between rostrum and supraocular spine; 5 spines branchial lateral or margin (Figure 6A).</p> <p> <b>Rostrum</b> spiniform; 0.6× PCL; supraocular spine 0.26× length of the rostrum; exceeding eyes. Epistomial ridge straight ending at antennal gland, mesial protuberance different (Figure 6A).</p> <p> <b>Abdominal tergites</b> unarmed; one transverse continuous stria on the second abdominal segment; without striae from the third to fifth segments.</p> <p> <b>Thoracic sternum</b> sternal surface smooth; sternite 4 with only a few striae. Sternite 3 0.3× width of sternite 4. Sternite 4 anterior margin triangular; narrowly contiguous with sternite 3. Mid-length of the sternal plastron (sternites 4–7) 0.5× width of sternite 7 (Figure 6E).</p> <p> <b>Eye</b> very small eyes; maximum corneal diameter 0.18× distance between anterolateral spines (Figure 6A).</p> <p> <b>Antenna peduncle</b> article 1 distomesial spine almost reaching the distal margin of article 2. Article 2 distomesial spine reaching distal margin of article 3; distolateral spine not reaching midlength of article 3. Articles 3 and 4 unarmed (Figure 6B).</p> <p> <b>Antennule peduncle</b> basal article (distal spines excluded) overreaching corneae; distolateral spine much longer than distomesial spine; 2 lateral spines, proximal smaller; longer lateral spine not reaching the end of distolateral spines (Figure 6C).</p> <p> <b>Third maxilliped</b> surface smooth; ischium with a small distal spine on extensor margin; ischium as long as merus length. Merus with small median spine; carpus; propodus and dactylus unarmed (Figure 6D).</p> <p> <b>Telson</b> with few striae; greatest width 1.2× median length; anterolateral margin weakly concave (Figure 6F).</p> <p> <b>P1</b> length 2.4–3.2× PCL; covered in rows of short plumose setae. Merus length 0.9–1.1× PCL; with a row of 2 large spines and 2 small spines on dorsal margin; 1 strong spine on dorsolateral margin; 4 spines on mesial margin; distomesial spine not reaching midlength of the carpus. Carpus length 0.5× merus; length 3× width, with 6 spines along the mesial margin. Propodus 1.3× merus length; palm with a row of 3 or 4 spines on the dorsal surface of the palm; fingers 0.4–0.5× total propodus length; without spines on outer margins (Figure 7).</p> <p> <b>P2–4</b> long and slender; with few small scales on lateral sides of meri and carpi; extensor margin with short plumose setae and few longer setae. P2 1.8–2.3× PCL; merus 0.7–0.8×PCL; length 8× width; 3.0× carpus length; 1.5× propodus length; extensor margin with 5–7 spines; flexor margin with 3 spines; well-developed distal spine; carpus extensor margin with the spine at midlength and a distal end; flexor margin with distal spine; propodus length about 8×height; with 5 movable flexor spines on flexor margin; dactylus gently curved distally; 0.6–0.7× propodus length, length about 7× height, extensor margin densely lined with stiff short setae on distal half; flexor margin armed along the entire length with 10–12 movable spines including spine at the base of unguis (Figure 7F). The end of P2 carpus does not reach the end of P1 merus. P3 with similar spination and article proportions as P2; merus 0.9× P2 merus length; propodus; and dactylus as long as those of P2. P4 length 0.7–0.8× P2 length, merus length 0.3–0.5× PCL; propodus and dactylus similar in length to those of P3; merocarpal articulation reaching hepatic marginal spine carapace (Figure 7).</p> <p> <b>Colour in life:</b> carapace pink anteriorly fading to white at posterior; abdominal somite 2 white; somites 3–6 pink, P1 and P2–4 white.</p> <p> <b>Genetic data:</b> DNA sequencing for this species was successful for mtCOI gene (Accession numbers: COI: OP311615). The average K2P distance between the morphologically closest <i>Typhlonida tiresias</i> (AY351014) and the SWIR specimen was 0.04% for COI.</p> <p> <b>Remarks:</b> The SWIR new species is the closest relative of <i>Typhlonida tiresias</i> (Macpherson, 1994) and <i>T. parvioculata</i> (Baba, 1982). The new species from SWIR can be differentiated from <i>Typhlonida tiresias</i> by gastric region with a row of epigastric spines, extensor border of merus of the third maxilliped, and the shape of the sternite 3. While <i>T. parvioculata</i> has a second abdominal segment with 2 to 4 spines anteriorly, a third maxilliped merus elongates with 2 prominent inner marginal spines of subequal size: one distal and another proximal to midlength and not in <i>Typhlonida milindi</i> <b>sp. nov.</b></p>Published as part of <i>Periasamy, Rengaiyan, Kurian, Palayil John & Ingole, Baban, 2023, Two new deep-water species of squat lobsters (Crustacea: Anomura: Galatheoidea) from the Central and Southwest Indian Ridge, pp. 165-178 in Zootaxa 5231 (2)</i> on pages 171-175, DOI: 10.11646/zootaxa.5231.2.3, <a href="http://zenodo.org/record/7575272">http://zenodo.org/record/7575272</a>
Social inequalities in heat-attributable mortality in the city of Turin, northwest of Italy: a time series analysis from 1982 to 2018
No full textBackground: Understanding context specific heat-health risks in urban areas is important, especially given anticipated severe increases in summer temperatures due to climate change effects. We investigate social inequalities in the association between daily temperatures and mortality in summer in the city of Turin for the period 1982–2018 among different social and demographic groups such as sex, age, educational level, marital status and household occupants. Methods: Mortality data are represented by individual all-cause mortality counts for the summer months between 1982 and 2018. Socioeconomic level and daily mean temperature were assigned to each deceased. A time series Poisson regression with distributed lag non-linear models was fitted to capture the complex nonlinear dependency between daily mortality and temperature in summer. The mortality risk due to heat is represented by the Relative Risk (RR) at the 99th percentile of daily summer temperatures for each population subgroup. Results: All-cause mortality risk is higher among women (1.88; 95% CI = 1.77, 2.00) and the elderly (2.13; 95% CI = 1.94, 2.33). With regard to education, the highest significant effects for men is observed among higher education levels (1.66; 95% CI = 1.38, 1.99), while risks for women is higher for the lower educational level (1.93; 95% CI = 1.79, 2.08). Results on marital status highlighted a stronger association for widower in men (1.66; 95% CI = 1.38, 2.00) and for separated and divorced in women (2.11; 95% CI = 1.51, 2.94). The risk ratio of household occupants reveals a stronger association for men who lived alone (1.61; 95% CI = 1.39, 1.86), while for women results are almost equivalent between alone and not alone groups. Conclusions: The associations between heat and mortality is unequal across different aspects of social vulnerability, and, inter alia, factors influencing the population vulnerability to temperatures can be related to demographic, social, and economic aspects. A number of issues are identified and recommendations for the prioritisation of further research are provided. A better knowledge of these effect modifiers is needed to identify the axes of social inequality across the most vulnerable population sub-groups
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
First reports jf Limnoricus ponticus Dovgal & Lozovkiy (Ciliophora: Suctorea) as epibionts jn, Pycnophyes (Kinorhyncha) from the Sndians Octan with key to spesies of the genus Limnoricus
No full textThis article deals withs the characteristics of the Limnoricus ponticus Dovgal & Lozovkiy, 2008 that was observes for the first time on Kinorhyncha as a horst and in a new lokality
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Habitat heterogeneity and its influence on benthic biodiversity in oxygen minimum zones
No full textOxygen minimum zones (OMZs; midwater regions with O2 concentrations <0.5 ml l?1) are mid-water features that intercept continental margins at bathyal depths (100–1000 m). They are particularly well developed in the Eastern Pacific Ocean, the Arabian Sea and the Bay of Bengal. Based on analyses of data from these regions, we consider (i) how benthic habitat heterogeneity is manifested within OMZs, (ii) which aspects of this heterogeneity exert the greatest influence on alpha and beta diversity within particular OMZs and (iii) how heterogeneity associated with OMZs influences regional (gamma) diversity on continental margins. Sources of sea-floor habitat heterogeneity within OMZs include bottom-water oxygen and sulphide gradients, substratum characteristics, bacterial mats, and variations in the organic matter content of the sediment and pH. On some margins, hard grounds, formed of phosphorites, carbonates or biotic substrata, represent distinct subhabitats colonized by encrusting faunas. Most of the heterogeneity associated with OMZs, however, is created by strong sea-floor oxygen gradients, reinforced by changes in sediment characteristics and organic matter content. For the Pakistan margin, combining these parameters revealed clear environmental and faunal differences between the OMZ core and the upper and lower boundary regions. In all Pacific and Arabian Sea OMZs examined, oxygen appears to be the master driver of alpha and beta diversity in all benthic faunal groups for which data exist, as well as macrofaunal assemblage composition, particularly in the OMZ core. However, other factors, notably organic matter quantity and quality and sediment characteristics, come into play as oxygen concentrations begin to rise. The influence of OMZs on meiofaunal, macrofaunal and megafaunal regional (gamma) diversity is difficult to assess. Hypoxia is associated with a reduction in species richness in all benthic faunal groups, but there is also evidence for endemism in OMZ settings. We conclude that, on balance, OMZs probably enhance regional diversity, particularly in taxa such as Foraminifera, which are more tolerant of hypoxia than others. Over evolutionary timescales, they may promote speciation by creating strong gradients in selective pressures and barriers to gene flow
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