Abstract

We describe the embryonic and larval development of the soil-living annelid Stenoninereis martini (Polychaeta, Annelida) based on collection of natural spawning in the locality Manche-à-eau in Guadeloupe FWI. Thousands of embryos are contained in a single large mucuous cocoon collected in the environment. S. martini follows the typical spiral cleavage mode of development that is highly conserved among annelids. Developmental stages were documented using light and scanning electron microscopy. Scanning electron microscopy (SEM) of whole mounted embryos was used to reconstruct and document cellular movements and organogenesis from early cleavage stages until metamorphosis. First cilia of the prototroch appear in young gastrula at T0+14h while swimming trochophores are first seen 20 hours after spawning (T0 + 20 h). Such trochophores developing and swimming inside the mucuous capsule have a well-developed prototroch, telotroch and a less conspicuous neurotroch and metatroch. Two chaetigers are first observed at T0 + 64 h and hatching and settlement occur 5 - 6 days after spawning. Metamorphosis occurs gradually from days 6 - 8. As the worms mature, there is an increase in overall size and in the number of setigers, paragnaths, and setae. To our knowledge, this is the first reported description of larval development throughout embryonic and larval development to settlement and metamorphosis for this species. With the help of these data we have established a scheme of morphologically defined stages in order to facilitate future studies on the molecular and histological level that will allow a detailed cross-species comparison among annelids and other phyla

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