Morphological adaptations of the Cratenemertidae (Nemertea, Enopla, Hoplonemertea) to the epipelagic habitat and lifestyle

Abstract

Four species (in three genera) of the family Cratenemertidae are found in the epipelagic (depth: <300 m) habitat. These species share many morphological differences from the benthic and intertidal majority of cratenemertids: the change in habitat (and, consequently, in lifestyle) can account for some, but not all, of these differences. The organ systems most affected are the body wall, musculature and sensory structures, particularly, the proboscis apparatus and alimentary canal, where the modifications can be attributed to a shift from active predation to passive feeding.

Keywords:

• Epipelagic habitat
• morphologic adaptation
• Achoronemertes
• Korotkevitschia

Acknowledgements

I am indebted to the Natural History Museum, London, for the loan of Achoronemertes specimens and permission to section and stain one of them. I am indebted to the University of Bergen Zoology Museum for the loan of specimens of “Atlantic H” and permission to restain one section series. I am grateful to two anonymous referees who made a number of extremely valuable suggestions on the original draft of this paper. This material is based upon work supported by the National Science Foundation under Grant no. 9712463. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.