Diversity of reproductive features in some Antarctic polynoid and sabellid polychaetes, with a description of Demonax polarsterni sp. n. (Polychaeta, Sabellidae)

The Polynoidae and Sabellidae represent two polychaete families with contrasting life habits and different phylogenetic constraints. Species of both families studied in this work were collected on the shelf of the Eastern Weddell Sea (Antarctica) during the EASIZ-I (1996) and EASIZ-II (1998) expeditions. Among the Polynoidae, three different species of the genus Harmothoe were observed to brood eggs under the dorsal elytra, which is an uncommon feature in this family. The egg size of all brooding taxa ranged between 120 and 216 µm. Three Sabellidae species were studied: Myxicola cf sulcata is gonochoric with eggs among the largest (up to 1000 µm) recorded for the sabellids. Eggs, as well as larvae, are incubated within the branchial crown, a feature newly discovered for the genus Myxicola. Demonax polarsterni n. sp. (a newly discovered taxon) and Euchone pallida are gonochoric and possess relatively large eggs (350 µm and 270 µm, respectively). In comparison with cogeneric species of temperate areas, the Antarctic Sabellidae have larger egg dimensions and egg brooding that seems unconstrained by adult size.