Life history and seasonal breeding of the deep-sea annelid Ophryotrocha sp. (Polychaeta: Dorvelleidae)

- A bathyal polychaete was monitored for several years under laboratory conditions.
- It exhibited seasonal feeding and reproductive patterns.
- Gametogenesis, fecundity, mating, egg laying and development were assessed.
- Feeding habits and growth to sexual maturity were monitored.
- Three generations developed successively over the course of this study.

Shallow-water annelids of the genus Ophryotrocha have become a popular biological system for exploring ecological, behavioral, developmental, and toxicological questions. Here we report on the successful maintenance in holding tanks, complete life cycle, and reproductive phenology of a first deep-water representative that could be used as a model species. This Ophryotrocha, which has yet to be formally described, is large (12-16 mm long) and exhibits simultaneous hermaphroditism. Specimens collected off northeast Newfoundland (eastern Canada) between 500 and 1500 m depth were monitored under flow-through laboratory conditions for over three years. They consistently exhibited seasonal feeding from April to February, followed by a reproductive season between February and May. Gametogenesis was initiated in early January and completed in early to mid-February, followed by courtship, which mainly involved pairs of individuals attached head to tail for hours to days. Transparent gelatinous masses containing 80-110 eggs were laid from mid-February to late-March. Propagules developed in the mass to the 1-chaetiger stage and, at an ambient temperature of ~1-4 °C, offspring emerged 30-45 days post-laying. Only ~40-45% of the eggs laid developed to the 1-chaetiger stage, with evidence of adelphophagy. After emerging from the gelatinous mass, 1-chaetiger stages remained aggregated and were guarded by adults for a few days before dispersing. All parents died following the dispersal of their offspring. The new generation reached sexual maturity in 8-9 months and was ready to reproduce the following January-February. A few cases of segmenting adult worms were also observed. Three complete generations developed successively to sexual maturity over the course of this study.