Postembryonic development, paedomorphosis, secondary sexual dimorphism and population structure of a new Florarctus species (Tardigrada, Heterotardigrada)

A large number of specimens (1563) of a new Florarctus species were collected in a single intertidal sample from the Ionian Sea, Italy. The postembryonic development of the new species was studied with emphasis on external morphology and functional anatomy. The new Florarctus species was recognized as having two distinct larval stages, during which the anus is formed and the gonads mature prior to the development of a gonopore. The larval stages are followed by one adult stage in females and two adult stages in males. Cuticular structures change in morphology during postembryonic development, so that they exhibit a juvenile and an adult appearance. The accelerated growth in gonadal development could be the result of paedomorphosis, which was observed in the tendency of adult males of the new Florarctus species to maintain juvenile character conditions.