evolution of the reproductive system of Urodasys (Gastrotricha: Macrodasyida)

Macrodasyidan gastrotrichs are hermaphrodites with complex reproductive organs that function in sperm transfer and receipt, but homology among the organs of members of different clades remains undetermined, as does a broader understanding of evolutionary trends in the reproductive biology of macroda...

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Bibliographic Details
Published in:Invertebrate biology 2014-12, Vol.133 (4), p.314-323
Main Authors: Atherton, Sarah, Hochberg, Rick
Format: Article
Language:English
Subjects:
Adhesives
Animal vivipary
Evolution
females
Gastrotricha
genetic databases
hermaphroditism
Macrodasyida
Macrodasyidae
males
meiofauna
new species
nucleotide sequences
Ova
Ovaries
parthenogenesis
phylogenetics
phylogeny
Reproductive system
ribosomal DNA
Specimens
spermatophore
Spermatophores
Spermatozoa
stylets
Testes
Urodasys
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Summary:Macrodasyidan gastrotrichs are hermaphrodites with complex reproductive organs that function in sperm transfer and receipt, but homology among the organs of members of different clades remains undetermined, as does a broader understanding of evolutionary trends in the reproductive biology of macrodasyidans. In this study, we investigate the evolution of reproduction in Urodasys, a clade of 15 macrodasyidan species that shows variability in reproductive mode (hermaphroditic and parthenogenetic) and sexual anatomy. We use partial 18S rDNA sequence data from 30 specimens representing five described species, sequence data from one undescribed species in GenBank, and sequence data from a potentially new species found at Capron Shoal, Florida, to gain insight into the phylogeny of the clade and clarify evolutionary trends in reproductive modality. Based on a total of 33 specimens of seven potential species, we found that members of Urodasys can be separated into three clades reflective of different reproductive modalities: Clade I, species with paired male and female gonads but without accessory sexual organs; Clade II, species with a single left testis, paired ova, and accessory organs including a sclerotic stylet; and Clade III, parthenogenetic species without testes or accessory organs. In addition, we find that the potentially new species from Florida can form spermatophores, a condition shared with another species in Clade I. Herein, we describe this novel spermatophore‐bearing species and discuss the significance of spermatophore formation in the genus.
ISSN:1077-8306
1744-7410
DOI:10.1111/ivb.12068