Comparative internal anatomy of Staurozoa (Cnidaria), with functional and evolutionary inferences.
Comparative efforts to understand the body plan evolution of stalked jellyfishes are scarce. Most characters, and particularly internal anatomy, have neither been explored for the class Staurozoa, nor broadly applied in its taxonomy and classification. Recently, a molecular phylogenetic hypothesis was derived for Staurozoa, allowing for the first broad histological comparative study of staurozoan taxa. This study uses comparative histology to describe the body plans of nine staurozoan species, inferring functional and evolutionary aspects of internal morphology based on the current phylogeny of Staurozoa. We document rarely-studied structures, such as ostia between radial pockets, intertentacular lobules, gametoducts, pad-like adhesive structures, and white spots of nematocysts (the last four newly proposed putative synapomorphies for Staurozoa). Two different regions of nematogenesis are documented. This work falsifies the view that the peduncle region of stauromedusae only retains polypoid characters; metamorphosis from stauropolyp to stauromedusa occurs both at the apical region (calyx) and basal region (peduncle). Intertentacular lobules, observed previously in only a small number of species, are shown to be widespread. Similarly, gametoducts were documented in all analyzed genera, both in males and females, thereby elucidating gamete release. Finally, ostia connecting adjacent gastric radial pockets appear to be universal for Staurozoa. Detailed histological studies of medusozoan polyps and medusae are necessary to further understand the relationships between staurozoan features and those of other medusozoan cnidarians.
Department of Zoology, Instituto de Biociências, Universidade de São Paulo , São Paulo , Brazil.
Lucília S
LS
Miranda
National Systematics Laboratory, National Marine Fisheries Service (NMFS), National Museum of Natural History, Smithsonian Institution , Washington, D.C. , United States of America.
Allen G
AG
Collins
Coastal Branch of Natural History Museum and Institute, Chiba , Katsuura, Chiba , Japan.
Yayoi M
YM
Hirano
Friday Harbor Laboratories and the Department of Biology, University of Washington , Friday Harbor, Washington , United States of America.
Claudia E
CE
Mills
Department of Zoology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil; Centro de Biologia Marinha, Universidade de São Paulo, São Sebastião, São Paulo, Brazil.
Antonio C
0000-0002-2884-0541
AC
Marques
Claustrum; Gonad; Histology; Medusozoa; Morphology; Nematogenesis; Reproduction; Stauromedusae; Taxonomy