COMPARATIVE OBSERVATIONS ON REPRODUCTIVE FEATURES OF FOUR PERKINSIANA (SABELLIDAE: SABELLINAE) SPECIES
Gambi M.C.1; Giangrande A.2 & Patti F.P.1
1 Laboratorio di Ecologia del benthos, Stazione Zoologica "A. Dohrn", Punta S. Pietro, 80077, Ischia, Napoli, Italy.
2 Dipartimento di Biologia, Università di Lecce, Lecce Italy
Reproductive biology within the genus Perkinsiana Knight-Jones has been previously known only for P. antarctica (Kinberg), P. rubra (Langerhans), and P. riwo (Rouse). Because of the lack of morphological synapomorphies establishing monophyly of the genus, information on reproductive features could be of value for understanding the relationship of the genus to other Sabellinae. The finding of several specimens belonging to four different species of Antarctic and sub-Antarctic Perkinsiana, obtained during Italian and German polar research, provides additional information on the reproductive biology and ecology within this genus. The small species, P. antarctica (mean body length 10 mm), was collected from the type locality, the Strait of Magellan, in the intertidal and shallow subtidal. It is a simultaneous hermaphrodite, brooding embryos within the branchial crown (in adults longer than 10 mm), with a mean egg diameter of 235 µm, and mature spermatozoa with elongate, pointed acrosomes. The larger species, P. littoralis (Hartman) (mean body length 80 mm), and P. borsibrunoi Giangrande & Gambi (mean body length 70 mm), were both collected from the deep shelf (up to 800 m depth) in the Eastern Weddell Sea, Antarctica. Both species have oocytes at different stages of maturation, with sizes ranging from 30 to 300 µm in diameter; P. littoralis has a mean egg size of 140 µm (eggs seen in individuals longer than 38 mm), and P. borsibrunoi a mean egg size of 190 µm (eggs seen in individuals longer than 40 mm). In the small species, P. milae Giangrande & Gambi (mean body length 14 mm), collected in the Ross Sea, Antarctica (74-200 m depth), gametes were never found, and some small individuals found inside tubes together with larger specimens, may indicate the presence of asexual reproduction (scissiparity). These data demonstrate the high variability in reproductive characters within the genus. The most interesting features of the studied species include brooding in P. antarctica, which seems not to be constrained by size, and possible cissiparity in P. milae, both of which could be both related to the colonised habitats.