Tiaropsis multicirrata M. Sars 1835

• Main Author: Calder, Dale R.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2017
• Subjects: Biodiversity; Taxonomy; Animalia; Cnidaria; Hydrozoa; Leptothecata; Tiaropsidae; Tiaropsis; Tiaropsis multicirrata; Barents Sea; Bergen; Medusa; Norway
• Online Access: https://zenodo.org/record/6015996; https://doi.org/10.5281/zenodo.6015996

Tiaropsis multicirrata (M. Sars, 1835) Figs. 17 a, b Thaumantias multicirrata M. Sars, 1835: 26, pl. 5, figs. 12 a–c [medusa]. Type locality. Norway: near Bergen (M. Sars 1835). Material examined. NB: Richardson, Deer Island, 44°59’42”N, 66°56’45”W, on pontoon slip of wharf, <1 m, on Mytilus edulis, 34‰, 9° C, 22.v.1999, one colony, without gonophores, coll. D. Calder, ROMIZ B3089. Description. Colony stolonal, with hydrorhiza entangled in filamentous algae growing on a mussel. Hydrorhiza mostly smooth, 0.1 mm in diameter, lacking internal septa, bearing pedicellate hydrothecae. Hydrothecal pedicels very short, less than 0.15 mm high, appearing irregularly annulated, supporting a hydrotheca at distal end. Hydrothecae erect, slender, deep, subcylindrical with smooth walls, without a distinct diaphragm basally, infrequently renovated, capped by a long cone-shaped operculum, hydrothecal walls typically widening very gradually from proximal to distal end, total length of hydrothecae from base to tip of operculum 0.4–0.8 mm, width at base of operculum about 0.15 mm and at insertion with pedicel 0.10 mm. Operculum a folded continuation of hydrothecal wall having about 10 pleats when closed, not distinctly demarcated from hydrothecal wall. Perisarc everywhere moderately thin but not flimsy. Nematothecae absent. Gonothecae not seen. Remarks. Tiaropsis multicirrata (M. Sars, 1835) was originally described from a medusa discovered in Norway. Knowledge of its hydroid remained obscure until a colony was linked to T. multicirrata in studies by Rees (1941) at Millport, Scotland. Rees found the hydroid on an old Buccinum shell, and based his identification on a medusa liberated from it in the laboratory. Later, Korsakova (1949) and Naumov (1951) raised similar hydroids from planulae released by medusae of the species. Based on the morphology of its trophosome, Naumov (1960) concluded that the hydroid was identical with one described earlier as Cuspidella mollis Spasskii, 1929 from the Russian coast of the Barents Sea. The ...