Dipolydora cf. socialis (Schmarda, 1861)
Rare, pseudocosmopolitan or non-indigenous
Largest specimen up to 180 chaetigers. Eyes absent. Prostomium bifid, extending as a caruncle towards the middle of chaetiger 3. Notochaetae present on chaetiger 1. Hooded hooks begin on chaetiger 7 (3-4 per fascicle) accompanied by 1-2 capillary chaetae; companion chaetae lost by chaetiger 10. Hooded hooks present on anterior and posterior chaetigers. Chaetiger 5 enlarged, about twice the size of preceding segment with 4-5 simple stout spines, falcate shaped with sub-terminal protuberance and alternating row of companion chaetae, also accompanied by dorsal bundle of geniculate chaetae and ventral fascicle of capillaries. Posterior notopodial spines present as fine needle like capillaries. Branchiae small and consistently begin on chaetiger 8 for all specimens examined. Branchiae appear to increase in length after chaetiger 10 and are absent on terminal chaetigers. Gizzardobservable at chaetiger 16 with 2-3 longitudinal muscles (only apparent under light microscope). Pygidium disc-shaped with notch and tuft of cilia at the centre.
South Africa: Knysna
Chile (type locality), Caribbean Sea, Gulf of Mexico, North Atlantic, New Zealand
Sexual reproduction in South African specimens remains undescribed. Evidence for asexual reproduction via architomic division (fragmentation with middle regions regenerating both anterior and posterior segments).
May be non-indigenous. The gizzard present at chaetiger 16 is characteristic of D. socialis but identification needs to be confirmed molecularly.