Atypical reproduction in a syllid worm: the stolon ofSyllis rosea(Annelida, Syllidae) takes care of its offspring

Abstract

The family Syllidae, aside from representing the most species-rich family in Annelida, is characterized by a number of sexual and asexual reproductive strategies. With the exception of a few viviparous species, the subfamily Syllinae is characterized by schizogamous reproduction with pelagic larval stages and without parental care. Laboratory rearing of ripe specimens of Syllis rosea showed a different reproductive strategy, hitherto unknown in this subfamily. While male stolons rapidly degenerated after fertilization, female ones released large eggs in a gelatinous cluster attached to the middle-posterior chaetigers. The gel mass progressively compacted as a cocoon wrapped by the stolon body; 7 days after the deposition the larvae hatched out from the cocoon at the metatrochophore stage and the female stolon died after a few days. After hatching the larvae remained associated to the stolon, and young specimens of S. rosea survived up to the 3-chaetiger stage. Until now cocoon brooding by the stolon has only been reported for some Autolytinae. The production of gelatinous egg masses and parental care are known in basally branching clades within Syllidae, suggesting that this reproduction mode might retain some ancestral features. The scarce knowledge about reproductive cycles in Syllinae does not allow clarification whether this strategy is unique for S. rosea, or it occurs in other congeneric species. Further research is needed to understand possible relationships between sexual reproduction and phylogeny, stolon morphology and its adaptation to parental care, and ultimately between reproductive strategies and ecology.

How oogenesis analysis combined with DNA barcode can help to elucidate taxonomic ambiguities: a polychaete study-based approach

“…In this way, integrative approaches encompassing one or more morphological analyses (i.e. histology, transmission electron microscopy, scanning electron microscopy) with molecular data, namely DNA barcodes, are desirable and encouraged for a better taxonomic resolution (Langeneck et al 2020;Martin et al 2020;Teixeira et al 2020) Given this scenario, this study aims to describe female gametogenesis in these three species of polychaetes, bringing to light new data regarding oogenesis of this group and investigate the utility of histology as a relevant associate tool to discriminate species, particularly useful for putative cryptic species, which are supposed to be distinguishable through molecular methods only. Considering the apparently high incidence of cryptic species among polychaetes (Nygren 2014, Lobo et al 2016, we anticipate that the application of histological and histophysiological analysis will be particularly relevant for the taxonomy and systematics of this highly diverse group of invertebrates.…”

Effect of temperature and body size on anterior and posterior regeneration in Hermodice carunculata (Polychaeta, Amphinomidae)

“…Posterior segment regeneration appears to be nearly universal within the phylum, while the ability to regenerate anteriorly is less common (Bely 2006(Bely , 2010Brockes and Kumar 2008;Zoran 2010;Licciano et al 2012Licciano et al , 2015. In some species, high regenerative potential is essential for increasing the number of specimens through asexual reproduction, while the combination of sexual and asexual reproduction is typical of the life cycles of certain groups (e.g., Syllidae) since it allows the asexual production of stolons, (the formation sexually mature individuals), that may later reproduce sexually (Franke 1999;Langeneck et al 2020). However, regeneration may also occur after accidental injury or predation (Bely and Nyberg 2010).…”