Schwaha T, Winston JE & Gordon DP. 2022.
J. Morphol.. Accepted Author Manuscript. doi.org/10.1002/jmor.21494. Link. Published online 5 July 2022

Abstract

Ctenostome bryozoans are a small group of gymnolaemates that comprise only few hundred described species. Soft-tissue morphology remains the most important source for analyzing morphological characters and inferring relationships within this clade. The current study focuses on the genus Sundanella, for which morphological data is scarce to almost absent. We studied two species of the genus, including one new to science, using histology and 3D-reconstruction techniques, and confocal laser scanning microscopy. Sundanella generally has a thick, sometimes arborescent cuticle and multiporous interzooidal pore-plates. The lophophore is bilateral with an oral rejection tract and generally has 30 or 31 tentacles in both species. The digestive tract shows a large cardia in S. floridensis sp. nov. and an extremely elongated intestine in S. sibogae. Both terminate via a vestibular anus. Only a single pair of parieto-diaphragmatic muscles is present and 4‒6 duplicature bands. Both species show a large broad frontal duplicature band further splitting into four individual bands. The collar is vestibular. Sundanella sibogae shows highly vacuolated cells at the diaphragm, whereas S. floridensis sp. nov. has unique glandular pouches at the diaphragmal area of the tentacle sheath. Such apertural glands have never been encountered in other ctenostomes. Both species of Sundanella are brooders that brood embryos either in the vestibular or cystid wall. Taken together, the current analysis shows numerous characters that refutes an assignment of Sundanella to victorellid ctenostomes, which only show superficial resemblance, but differ substantially in most of their soft-body morphological traits. Instead, a close relationship with other multiporate ctenostomes is evident and the families Pherusellidae, Flustrellidrae and Sundanellidae should be summarized as clade ‘Multiporata’ in the future.