1,720,988 research outputs found
Further data on the Italiana marine gastrotrich fauna.
No full textThis study reports on the gastrotrich fauna recorded in 14 new or newly investigated Italian locations, during surveys carried out from 2003-2005. As some of these unpublished faunistic data were included in the chapter devoted to Gastrotricha in the recent check-list of Italian marine species, this paper aims to provide details regarding the locations, people involved, sampling times, characteristics of the surveyed microhabitats and, of course, a list of species found at any single location. The research should be relevant as it provides the first lists of meiobenthic taxa from some protected Italian areas, such as “Area marina protetta di Porto Guaceto” and Asinara island. Other interesting locations, from a faunistic point of view, seem to be Cala Pisana, on the island of Lampedusa, where 16 species were recorded and Pomonte on the island of Elba, home to a dense population of lepidodasyid gastrotrichs that belong to an undescribed genus and species. Overall, it is hoped that the 40 species reported can contribute to debate on the biogeography of the Mediterranean gastrotrich
A new eye-bearing Macrodasys (Gastrotricha : Macrodasyida) from Jamaica
No full textA new macrodasyidan gastrotrich is described from fine-medium sand collected at Doctor's cave beach of Montego Bay, Jamaica. Macrodasys ommatus n. sp. is the first gastrotrich to be reported from the Jamaica, the second described species in the genus to bear eye-spots and the . The shape of the frontal organ distinguishes the Jamaican species from its sibling M. nigrocellus: elongate and undulate without an accessory lateral chamber in the former vs. rather short with an accessory lateral chamber in the latter. The following combination of characters further distinguish the new species from its congeners: up to 7 anterior adhesive tubes per side arranged in a transversal row, three pairs of lateral adhesive tubes equally spaced along the intestinal region, up to 21 ventro-lateral adhesive tubes per side, two of which arise along the posterior region of the pharynx
The muscular system of Musellifer delamarei (Renaud-Mornant, 1968) and other chaetonotidans with implications for the phylogeny and systematisation of the Paucitubulatina (Gastrotricha)
No full textWe studied comparatively the muscle organization of several gastrotrich species, aiming at shedding some light onthe evolutionary relationships among the taxa of the suborder Paucitubulatina. Under confocal laser scanningmicroscope, the circular muscles were present in the splanchnic position as incomplete circular rings in Muselliferdelamarei (Chaetonotidae) and Xenotrichula intermedia (Xenotrichulidae) and as dorsoventral bands in Xenotrichulapunctata, Heteroxenotrichula squamosa and Draculiciteria tesselata (Xenotrichulidae); in the somaticposition, M. delamarei shares the presence of dorsoventral muscles with all the Xenotrichulidae, in contrast withthe remaining Chaetonotidae that lack these muscles. Maximum parsimony analysis of the muscular charactersconfirmed monophyly of Paucitubulatina and Xenotrichulidae, while the Chaetonotidae was paraphyletic, with theexclusion of Musellifer, which is the most basal genus within the Paucitubulatina. Xenotrichulidae is the sistertaxon to Chaetonotidae, which in turn has Polymerurus as the most basal taxon. In general, the results agree withrecent phylogenetic inferences based on molecular characters and support the hypothesis that, within Paucitubulatina,dorsoventral muscles are plesiomorphies retained in marine, interstitial, hermaphroditic gastrotrichs.Dorsoventral muscles were subsequently lost during changes in lifestyle and reproduction modality that took placewith the invasion of the freshwater environment. This new information prompted us to reconsider the systematizationof Chaetonotidae, proposing the establishment of Muselliferidae fam. nov. to include the genera Muselliferand Diuronotus
The gastrotrich community of a northAdriatic Sea site, with a redescription of Musellifer profundus (Chaetonotida: Muselliferidae).
No full textDuring a survey of the marine meiobenthos in a predominantly muddy area, 40 km south of Venice (northern Adriatic Sea,Italy), 11 species of gastrotrichs were recorded. Gastrotrichs were found in 11 out of the 16 investigated stations, with densities(mean + standard deviation) ranging from 0.6 + 0.5 to 97.7 + 71.2 ind./10 cm2. The community was dominated byMusellifer profundus, which made up 24.5% of the entire gastrotrich assemblage and reached in a single station the abundancepeak of 18.3 ind./10 cm2. The finding bears relevance to the biogeography and ecology of several species. The presence ofnumerous specimens of the rare M. profundus allowed new insights into the arrangement and functioning of the hermaphroditicsexual apparatus in this phylogenetically important genus, for which such data are scanty. The new information willcertainly be useful in evolutionary studies aimed at reconstructing the phylogenetic relationships within Gastrotricha, whileoffering at the same time additional morphological traits to be used in reliable species identification. Although only threespecies of Musellifer have been described so far, there are several others awaiting a formal affiliation, a task that willbenefit from this new information
A new species, genus and family of marine Gastrotricha from Jamaica, with a phylogenetic analysis of Macrodasyida based on molecular data
No full textGastrotricha is a phylum of aquatic microinvertebrates counting about 850 species divided into the two orders Chaetonotida and Macrodasyida. Currently, Chaetonotida includes 8 families and 31 genera while Macrodasyida includes 9 families and 32 genera; however, systematics is in a state of flux due to phylogenetic incongruences of the classical systematization. The process of re-systematization will benefit from additional surveys of insufficiently known taxa and especially from the discovery of new species bearing novel characteristics that could help to recognize plesiomorphy in these morphologically diverse animals. Herein, a new and interesting macrodasyidan species from the northwestern shore of Jamaica is described.
Specimens up to 1170 mm in length have: a vermiform body with numerous epidermal glands; naked cuticle; head weakly demarked; posterior end in the form of two caudal pedicles; TbA, arranged in two diagonal rows, inserting directly on the cuticle; TbL/TbVL scarce; TbD and TbV absent; TbP at the tip of each caudal pedicle and along its inner margins; midsized terminal mouth; pharynx with pores at the base; PhIJ at U20; intestine rectilinear, anus ventral; hermaphroditic sexual apparatus; gonads paired: female anterior, male posterior; gametes maturing in a caudo-cephalic direction; spermatozoa relatively short, with spiralled head and spiralled tail; sperm ducts directed posteriorly, converging ventrally on the midline
and joining the sac-like caudal organ; and frontal organ, dorsal to the intestine, not obviously muscularized. External
morphology and layout of the reproductive system appear so unique among Gastrotricha to grant the establishment of a new taxon, for which the name Hummondasys jamaicensis gen. et sp. nov. is proposed. Furthermore, to allocate the new genus, the creation of the new family Hummondasyidae is proposed based both on the morphological peculiarities and results of phylogenetic analyses based on the 18S rRNA gene, which involved all of the relevant macrodasyidan taxa
First record of Musellifer profundus (Gastrotricha) in the Italian seas.
No full textSeveral specimens of Musellifer profundus were found during a survey of the meiobenthos in the Northern Adriatic Sea. The finding bears relevance with respect to the biogeography and biology of marine gastrotricha as it widens the distributional boundaries of a rare species (thus far known only from the North and Baltic seas and from off Marseille), at the same time allowing new insights into the arrangement and functioning of the hermaphroditic sexual apparatus in a genus for which data in this regard are scanty
Meiofauna densities and gastrotrich community composition in a Mediterranean sea cave
No full textDuring the past 5 decades, the large-sized biota inhabiting dark marine caves has attracted the attention of many marine biologists; in contrast, studies concerning the meiofaunal organisms of these peculiar biotopes remain scanty and mostly with a taxonomic aim. In this study, the nature and abundance of meiofaunal taxa living in a Mediterranean, semi-submerged sea cave was surveyed in relation to distance from the entrance and over two different seasonal periods. Particular attention was paid to the Gastrotricha taxocene. Research was carried out in a cave along the Ionian coast of Apulia (southern Italy), the Grotta Piccola del Ciolo which opens for approximately 120 m on the north-eastern side of a shallow fjord and has a bottom blanketed by fine to very fine sand, occasionally rich in detritus. Quantitative samples in four replicates were collected by SCUBA diving, in November 2000 and June 2001, coring the sediment with a hand-held piston corer in three light-free sites (stations 1-3) located at increasing distances from the entrance. At each site, two additional 500-ml sediment samples were collected for an in vivo study of the Gastrotricha. Faunistic analysis found a fairly high meiobenthic diversity, identifying representatives of more than 12 major groups, with total abundances ranging from 656 ind./10 cm(2) (10 cm(2)) in November to 1,069 ind./10 cm(2) in June. Station 1, the closest to the entrance invariably hosted the most abundant meiofaunal community (851 ind./10 cm2 in November and 1932 ind./10 cm(2) in June), followed by station 2 or 3 depending on the season. While nematodes and harpacticoids appear as the most abundant taxa when the cave is considered as a whole, other taxa may prevail numerically in selected stations, e. g. priapulids, which are the second most abundant taxon at station 1 (30 ind./10 cm(2) in November and 83 ind./10 cm(2) in June). Although the density of total meiofauna and that of the single groups may not be very high, the cave is interesting by virtue of the peculiarity of the hosted fauna, e. g., species and genera new to science or new to the Mediterranean Sea. Regarding the Gastrotricha, we found 16 species, accounting for 1.3-2.6% of the total meiobenthos (density = 8.4 ind./10 cm(2) in November and 27.4 ind./10 cm(2) in June). Analysis of the gastrotrich community found, particularly in June, an assemblage of taxa quite different from those found in open habitats, even at the family level; differences that are probably due to the exploitation of different food resources by animals populating the two environments, i.e. algae in the open sea versus bacteria in the caves. Results indicate that for meiofauna, as happens for macrofauna, the marine caves may represent hotspots of biodiversity and endemism; the driving forces at the base of the trophic depletion hypothesis seem to be responsible for structuring the meiofauna community inside the cave
Meiofaunal cryptic species revealed by confocal microscopy: The case of Xenotrichula intermedia (Gastrotricha)
No full textThe phylum Gastrotricha includes about 750species of meiobenthic marine and freshwater species thatare often widely distributed. The microscopic size, shortlife cycle, low motility of adults, and the absence of larvalstages normally required for dispersal raise doubts aboutthe putative cosmopolitan distribution of many of gastrotrichspecies. The phenomenon of cosmopolitanism isacknowledged for all major meiobenthic taxa (“the meiofaunaparadox”) and can be explained, at least in part, withthe existence of sibling species, so far identiWed primarilyby molecular analysis. In this paper, we report thediscovery of sibling species in the marine chaetonotidanXenotrichula intermedia using confocal laser scanningmicroscopy (CLSM). A total of 40 specimens collectedfrom two geographically separate populations, the Mediterranean(Adriatic Sea) and the Arabian Gulf (Kuwait), wereinvestigated. Fifteen specimens of each population werestudied in vivo with a contrast interference microscope(DIC) in order to obtain the main morphometric parameters;ten other animals (Wve in each population) were Wxedand marked with Xuorescent phalloidin for the observationof their muscular systems under CLSM. The metrics andmeristic data of the two populations fall within the range ofmeasures recognized for the species. Pairwise comparisons(t-test) in general did not reveal statistically signiWcantdiVerences between the traits of specimens belonging to the two populations; moreover, multivariate analyses (clusterandMDS analysis) were unable to separate clearly theMediterranean from the Arabian specimens. In contrast, anexamination of their muscular systems revealed cleardissimilarities between the two geographic groups. In particular,while the Italian specimens possessed incompletecircular bands and dorsoventrally orientated muscles thatare partially inserted into the basal lamina of the cuticle, inboth splanchnic- and somatic positions, their Arabian counterpartsshowed partial dorsoventral bands and completecircular muscles that surround the entire body of the animalin the same corresponding positions. Additional diVerencesin the position of helicoidal bands (present in a more anteriorlocation in the Italian specimens) are noted betweenMediterranean and Arabian specimens. Since the investigatedanimals share a similar interstitial habitat, a workinghypothesis connects the diVerences in the musculature topossible diVerences in the reproductive modality of specimensbetween the two populations
Different diversification rates between sexual and asexual organisms
No full textPatterns of diversity reflect the balance between speciation and extinction over time. Here we estimate net diversification rates for samples of sexual and asexual rotifers using phylogenetic reconstructions from sequence data of one mtDNA locus, cytochrome oxidase c subunit I. All four clades of bdelloid rotifers, obligate asexuals, had higher number of species per clade and significantly higher accumulation of diversification events towards the root of the trees than the four clades of their sexual relatives, the monogonont rotifers. Such differences were robust to confounding effects of number of analysed sequences, haplotype diversity, overall genetic divergence, age of the clades or geographic coverage. Our results support the idea that differences in diversification rates could thus be ascribed to different mechanisms of speciation, with ecological speciation as the most plausible mechanism for asexual organisms
Biomonitoring of a dumping area: the meiobenthic community
No full textMeiofauna abundance and community structure were investigated in a sea disposal site in the Ligurian Sea, 1 year after the dumping of material dredged from the harbour of Leghorn. Faunistic analysis of cores taken in three stations subject to sediment discard and one in a control site found in all cases the Nematoda as the dominant taxon followed by the Harpacticoida Copepoda. While ANOVA could not detect statistically significant differences among stations, except station H5, the number of taxa and their density were higher than values obtain from samples collected two weeks and two months after the dumping. Sites H5 previously indicated as the most impacted site showed the higher density of total meiofauna and the most well-balanced repartition of taxa. Overall data support the working hypothesis of a progressive but differentiated faunistic recovery of the impacted sites
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