The 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.
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|Anno di pubblicazione:||2009|
|Titolo:||Meiofaunal cryptic species revealed by confocal microscopy: the case of Xenotrichula intermedia (Gastrotricha).|
|Autori:||Leasi F.; Todaro M.A.|
|Appare nelle tipologie:||Articolo su rivista|
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