The Breeding of Arenicola Ecaudata Johnston and A. Branchialis Aud. & Edw. at Plymouth

Abstract

The two ‘tail-less’ lugworms, Arenicola ecaudata Johnston and A.branchialis Audouin and Mime-Edwards (= A.grubii Claparede), live in gravel and under stones, unlike the 'tailed' species which are found mainly in sandy beaches. Both are local in distribution compared with the wide-spread caudate species. A. ecaudata is known to occur from Iceland to northern Spain, and thus has a rather more boreal distribution than A. branchialis which ranges from the west coast of Scotland to Morocco, the Mediterranean and the Black Sea. (Ashworth, 1912; Mclntosh, 1915; Fauvel, 1927; Rioja, 1935; WesenbergLundj 1951.) Neither species is known from the western side of the Atlantic.Since the two species can often occur side by side and it appeared that they were adapted, not for life in different habitats, but for different temperature regimes, it was suggested to us by Prof. G. P. Wells, F.R.S., that an investigation of their breeding seasons at Plymouth might help in understanding their distribution and specific separation. It happened that we had already made some preliminary investigations in the Isle of Man, and we were therefore pleased to adopt Prof. Wells's suggestion.Mature specimens of both species have been noted by previous workers. Ashworth (1912) found mature gametes in A. ecaudata at Port Erin in April and at Plymouth in August. Fauvel (1899) recorded mature worms at Cherbourg from March to October, while Hentschel (1930) believed spawning occurred at Plymouth in February-March and August-September.