Meeting Abstract

90.4  Friday, Jan. 6  Reproduction and fecundity in the nemertean worm Prosorhochmus americanus (Nemertea, Hoplonemertea) CAPLINS, S.A.*; TURBEVILLE, J.M; Virginia Commonwealth University; Virginia Commonwealth University

The nemertean worm Prosorhochmus americanus resides on rock jetties in coastal areas of the Southeastern United States and is uncommon among nemerteans in being hermaphroditic and viviparous. Early observations revealed that isolated individuals are able to reproduce in the absence of cross-fertilization. As part of a comprehensive investigation of reproduction in this species, individual fecundity was examined whereby worms were either placed in pairs, with the potential to cross-fertilize, or kept isolated, preventing cross-fertilization. Specifically, 120 adult worms (treatment 1; n=40 replicates) and 42 juvenile worms (treatment 2; n=14 replicates) were raised in pairs or in isolation and monitored for the development and emergence of offspring. Worms were examined every 24 hours for juvenile emergence and were fed amphipod crustaceans once weekly. Worms in treatment 2 were examined weekly for the development of gonads, eggs, and embryos. Experiments were carried out for 160 days, over which period a total of 2,863 juveniles were produced. Isolated individuals in treatment 1 produced slightly more juveniles (n, mean=21.3±3.8) than paired worms (n/2, mean=19.1±3.4; t-test, p=0.0102, α=0.05). In contrast, worms in treatment 2 produced approximately the same number of offspring regardless of being isolated or paired (p=0.26). Newly emerged juveniles averaged 2.5 mm in length, and produced gonads within 2 weeks of emergence. Developing juveniles appeared within 5 weeks and emerged approximately 3 weeks later, resulting in a two-month generation time (juvenile-to-juvenile). Microsatellite DNA markers are currently being developed to determine the degree at which cross-fertilization occurs between paired worms and will provide a starting point in determining potential fitness advantages that may be associated with differing modes of reproduction.