New Sticky Things in Holopelagic Nemerteans

NORENBURG, J.L.*; ROE, P.: New Sticky Things in Holopelagic Nemerteans

Biology and diversity of delicate, gelatinous, holopelagic deep-sea organisms continue to be sources of major surprises, despite more than a century of studies. Nemerteans are among the least studied groups of these organisms. Recent collaborative deep-sea mid-water collections made with J. Childress (UCSB) and Monterey Bay Aquarium demonstrated that taxonomic diversity of holopelagic nemerteans was vastly under-appreciated and that previously studied species were poorly known. One surprise is a pair of epidermal, specialized glandular regions found near the posterior of the body, more or less along the left and right lateral margins, occuring in 13 of our recently collected morpho-species. The taxonomic distribution of the glandular structures is suggestive of a strong phylogenetic correlation, providing some welcome relief in this character-impoverished group of worms. In fact, the structures appear to constitute a synapomorphy for Pelagonemertidae and Balaenanemertidae.These glandular structures generally appear as an elongate patch of thickened epidermis comprised of two mostly segregated types of glandular cells, with staining properties suggestive of acid mucins and more proteinaceous mucoids respectively. A key attribute of these structures is strong bonding with underlying connective tissue, unlike the rest of the epidermis, which is readily lost in the collecting process. Homology of these structures with a ventral, more complex glandular specialization known previously from Plotonemertes remains to be tested. In the course of our study we found additional regional glandular specialization of epidermis in three other species of pelagic nemerteans; these seem to be non-homologous. Neither structure nor location offer self-evident suggestions for function of these specializations.

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