A new nemertean with a branched proboscis, Gorgonorhynchus citrinus sp. nov. (Nemertea: Pilidiophora), with molecular systematics of the genus

Among ~1300 species of world nemerteans, seven species in five genera of lineid heteronemerteans have been known to possess a branched proboscis. In this paper, we describe the eighth branched-proboscis species: Gorgonorhynchus citrinus sp. nov. from Okinawa, Japan. We also report Gorgonorhynchus cf. repens Dakin & Fordham, 1931 with uniformly orange body, as a new member for the Japanese nemertean fauna. We infer the phylogenetic relationships between these forms and other members of Lineidae McIntosh, 1874 for which partial sequences of the mitochondrial 16S rRNA and cytochrome c oxidase subunit I, and the nuclear 18S rRNA, 28S rRNA, and histone H3 genes are available in public databases, along with newly sequenced data of another branched-proboscis heteronemertean, Polydendrorhynchus zhanjiangensis (Yin & Zheng, 1984) from China. In the resulting tree, Gorgonorhychus Dakin & Fordham, 1931 was sister group to non-branched-proboscis Dushia Corrêa, 1963, whereas P. zhanjiangensis was sister group to likewise non-branched-proboscis Cerebratulus lacteus (Leidy, 1851). http://zoobank.org/urn:lsid:zoobank.org:pub:685992C5-F595-4C28-9178-256D945E595A

Predator–prey relationship between the nemertean Cerebratulus lacteus and the soft-shell clam, Mya arenaria: surface-exploration activity and qualitative observations on feeding behaviour

The presence of predators at soft-shell clam (Mya arenaria) culture sites is of great concern in Atlantic Canada. Laboratory studies were undertaken (i) to monitor the surface-exploration activity of the nemertean Cerebratulus lacteus to obtain a general indication of its activities throughout a 24-h period, and (ii) to describe its behaviour while feeding on M. arenaria to obtain a better understanding of the predation mechanisms involved. The first experiment showed that surface exploration varied significantly according to the presence or absence of prey. When clams were present, C. lacteus left its burrow at all times. In their absence, no predators were observed exploring the sediment surface between 21:00 and 03:00. Predator density also had an impact on surface-exploration activity. The second experiment showed that initial encounters between C. lacteus and its prey did not necessarily trigger proboscis eversion. Attacks with the proboscis, before consumption of the prey started, were concentrated in the siphon and foot areas. Cerebratulus lacteus introduced itself into the mantle cavity of M. arenaria through the same siphon and foot areas to feed. Our observations also revealed that C. lacteus may feed in a group on a single prey individual. The observations from this study provide preliminary and fundamental information for use in investigating adequate predator-control measures that may be useful for aquaculture.