Reproductive differences among species, and between individuals and cohorts, in the leech genus Helobdella (Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae), with implications for reproductive resource allocation in hermaphrodites.

Roshni G Iyer,Christopher J Winchell,David A Weisblat,Michelle Levine,D Valle Rogers,Patrick Callaerts

doi:10.1371/journal.pone.0214581

Roshni G Iyer, Christopher J Winchell + Show 4 more

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https://doi.org/10.1371/journal.pone.0214581

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Abstract

Leeches and oligochaetes comprise a monophyletic group of annelids, the Clitellata, whose reproduction is characterized by simultaneous hermaphroditism. While most clitellate species reproduce by cross-fertilization, self-fertilization has been described within the speciose genus Helobdella. Here we document the reproductive life histories and reproductive capacities for three other Helobdella species. Under laboratory conditions, both H. robusta and H. octatestisaca exhibit uniparental reproduction, apparently reflecting self-fertility, and suggesting that this trait is ancestral for the genus. However, the third species, H. austinensis, seems incapable of reproduction by self-fertilization, so we inferred its reproductive life history by analyzing reproduction in breeding cohorts. Comparing the reproductive parameters for H. robusta reproducing in isolation and in cohorts revealed that reproduction in cohorts is dramatically delayed with respect to that of isolated individuals, and that cohorts of leeches coordinate their cocoon deposition in a manner that is not predicted from the reproductive parameters of individuals reproducing in isolation. Finally, our comparisons of reproductive capacity for individuals versus cohorts for H. robusta, and between different sizes of cohorts for H. austinensis, reveal differences in resource allocation between male and female reproductive roles that are consistent with evolutionary theory.

Highlights

Leeches comprise a monophyletic group of segmented worms within the phylum Annelida
The data presented here detail our findings concerning the reproductive life history, under similar conditions of laboratory culture, for H. robusta [19] and for a scute-bearing (H. stagnalis-like) species that we identify as H. octatestisaca [20] on the basis of its cytochrome oxidase 1 (CO1) sequence
Molecular phylogenies have revealed that the morphologically defined H. stagnalis is a complex of species [15, 28, 29]; CO1 sequencing indicates that the species used here is H. octatestisaca (Hoc) [20]

Summary

Introduction

Leeches comprise a monophyletic group of segmented worms within the phylum Annelida. They occupy primarily freshwater habitats, as fluid-feeding ectoparasites on vertebrate hosts, or predators or scavengers of freshwater invertebrates [1]. Primarily in the family Glossiphoniidae, have been used in studies of cell lineage and embryonic development, speciation, predator-prey interactions and genome evolution in the superphylum Lophotrochozoa [1, 9,10,11,12]. Leeches generally, and those species in the glossiphoniid genus Helobdella in particular, provide models for integrating the questions and approaches from a wide range of biological sub-disciplines, from physiology and development to ecology, genomics and evolution in a less well explored branch of animals

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