Reproductive cycle of Bispira volutacornis (Polychaeta: Sabellidae) on the west coast of Ireland Received: 1 July 2002 / Accepted: 27 May 2003 / Published online: 12 July 2003 Ó Springer-Verlag 2003 Abstract The reproductive cycle of Bispira volutacornis, a dioecious polychaete, was followed over two spawning periods in Lettercallow Bay, on the west coast of Ire- land. In the younger generation of sexually mature adults, gender can be determined on the basis of colour, the dorsal aspect of the males being cream at matura- tion, whilst the females are pink at the previtellogenic stage and an olive green at maturation. An annual reproductive cycle of 12 months shows that oocyte/ sperm maturation is extraovarian. The male reproduc- tive cycle proceeded at a more rapid pace than that of the female cycle, with sperm maturing earlier. Spawning in B. volutacornis occurred between late July and early September. B. volutacornis is a polytelic species, surviv- ing spawning and releasing all gametes in a single batch, with a mean spawned oocyte diameter of 118 lm. The reproductive cycle appears to be regulated by a seasonal change in water temperature, and spawning is timed to produce larvae during the autumnal planktonic bloom in Lettercallow Bay. Introduction Bispira volutacornis (Montagu) is considered a large sa- bellid polychaete whose geographical range is now thought to be more limited than was hitherto described, and is perhaps confined to the western coasts of Europe (Knight-Jones and Perkins 1998). B. volutacornis ranges from the littoral to the sublittoral, and is often found in large aggregations on and under rock surfaces and in rock crevices. At many locations, these polychaetes can be the numerically dominant non-colonial members of epiben- thic assemblages (Bell 1982). Related literature is restricted almost exclusively to faunal records and descriptions of the external morphology, with knowledge of the species biology and ecology being very fragmentary (Rathke 1843; Fauvel 1927; Dewarumez et al. 1992). The family Sabellidae shows a range of reproductive behaviour including: broadcasting of gametes, deposi- tion of benthic egg masses and brooding both outside the lip of the tube and within the tube (Schroeder and Hermans 1975; McEuen et al. 1983; Wilson 1991). Of the 290 described species in this family (Fauchald 1977), knowledge of their reproductive biology is limited, in whole or in part, to no more than 40 species (McEuen et al. 1983; Knight-Jones and Bowden 1984). Materials and methods Samples were collected in situ in Lettercallow Bay, an embayment off Lettermore Island within Kilkieran Bay, on the west coast of Ireland (53°17.4¢N; 9°42¢W; Fig. 1). A quantitative survey of gametogenesis in Bispira volutacornis was carried out over the periods October 1997–November 1998 and June 1999–August 1999. Sampling was executed at monthly intervals outside and ev- ery 2 weeks within the active spawning period. Water temperature was recorded on each sampling date. A minimum of six females per month was selected and, fol- lowing relaxation in menthol crystals, their oocytes were removed by syringe from the coelom and placed on a cavity slide. Random measurements of 100 oocytes per female were made, under a bin- ocular microscope, in tandem with a computer-based image ana- lyser. The findings were staged using the following diagnostics (after Olive 1995), based on extraoovarian oogenesis: stage 1, onset (majority of oocytes <30 lm); stage 2, developing (majority of oocytes 40–60 lm); stage 3, developing (majority of oocytes 60– 70 lm); stage 4, developing (majority of oocytes 80–130 lm); stage 5, mature (oocytes >110 lm); and stage 6, resting (oversized oocytes). To examine the reproductive cycle, two to four segments were taken from each individual polychaete, just below the thorax. Sections were fixed and impregnated with paraffin wax (Bancroft and Stevens 1977). Microtome sections, of 5–10 lm thickness, were stained for general tissue structure using Ehrlich’s haematoxylin and eosin. Marine Biology (2003) 143: 919–925 DOI 10.1007/s00227-003-1146-0 R. Nash Æ B. F. Keegan Communicated by J.P. Thorpe, Port Erin R. Nash (&) Æ B. F. Keegan Department of Zoology, Martin Ryan Institute, NUI, Galway, Ireland E-mail: roisin.nash@nuigalway.ie Tel.: +353-87-7640224 Fax: +353-91-525005