Opening the black box: diet, feeding mechanism, and pelagic duration of predatory Nemertean larvae (Nemertea: Hoplonemertea)

Abstract

Many factors, both demographic and geographic, can influence connectivity in animal populations. Among the demographic factors, the type of reproduction, especially the larval development, can influence population connectivity. It is largely accepted that species with planktotrophic larvae have longer pelagic duration then species with lecithotrophic larvae. Consequently, populations of species with planktotrophic development tend to be less differentiated (better connected by dispersal) than those of species with lecithotrophic development. Both types of development are found within the phylum Nemertea, and within each of the three nemertean classes: the Palaeonemertea, the Pilidiophora, and the Hoplonemertea. Most pilidiophorans and palaeonemerteans possess planktotrophic larvae. Until recently, the third group, the Hoplonemertea, was thought to possess only lecithotrophic larvae. However, recent studies by Maslakova and collaborators have shown that at least some hoplonemertean species might be feeding in the plankton. This increases estimates of pelagic larval duration, and may explain surprising lack of population differentiation found in some species. However, what and how hoplonemertean larvae eat, and how long they remain in the plankton remains a mystery. Here we propose an internship of 12 months in the Maslakova Lab, at the Oregon Institute of Marine Biology (University of Oregon, USA), to assess the diet, feeding behavior, and pelagic duration of hoplonemertean larvae. This facility was chosen because Svetlana Maslakova is a leading expert in the world on nemertean development, biodiversity and systematics. Maslakova Lab pioneered techniques for raising nemertean larvae through metamorphosis, documenting their feeding and development, DNA-based identification of wild-caught nemertean larvae and their prey. I propose to use a PCR approach to assess the diet of wild-caught hoplonemertean larvae, and then to raise larvae of two species common in Southern Oregon, Carcinonemertes errans and Emplectonema sp., in the laboratory by exposing them to candidate prey, documenting their feeding behaviour, development, and pelagic duration. (AU)