The culture, experimental taxonomy, and comparative morphology of the planktonic stages of Norfolk autolytoids (Polychaeta: Syllidae: Autolytinae)

Abstract

Stocks of two species were cultured as described to yield stolons for mating trials with one another and with planktonic stolons of unknown origins, which were progressively linked to known taxa by mating reactions and/or morphological comparisons. The most hardy and sexually vigorous species in culture was the low-intertidal Proceraea cornuta (Agassiz); fewer results were obtained with the much less hardy and principally offshore Autolytus brachycephalus (von Marenzeller), and mating was seen once in A. alexandri Malmgren. Healthy males of each species showed all or part of a consistent pattern of mating responses to a pheromone from preovulatory (= virgin) or newly postovulatory homospecific females, but none whatever to heterospecific females. Planktonic males, possibly of A. langerhansi Gidholm, reacted anomalously to virgin females of the closely allied A. brachycephalus. The stolons of both sexes fell into three groups, with respectively 14 (A. alexandri only), 6 (the genera Proceraea and Procerastea, distinguished from each other by the degree of development of the dorsal cirri and the number of eggbags in the female), and 3 or fewer (Autolytus of the prolifer-group) setigers in the front region. These groups also have different arrangements of the appendages on and immediately behind the stolon head; the numbers of setigers in their middle regions and tails show variations which are not statistically significant. The sexual stages in North Norfolk plankton comprise two species found only in winter and spring (Proceraea prismatica and A. alexandri), one found all year but mainly in spring (P. cornuta), one from late spring to early autumn (A. brachycephalus), and two found only in summer (Procerastea halleziana and A. ?langerhansi); the relationship between seasonally, zoogeography, and water-temperature is briefly discussed.