Berghia

Abstract: The aeolid genus Berghia was described by Trinchese in 1877, with Berghia coerulescens (Laurillard, 1832) as type species. The validity of Berghia has been questioned by some authors, who have considered it a junior synonym of Spurilla Bergh, 1864. The lack of consensus has caused confusion, blurring the differences between these two genera. A recent molecular phylogeny of Aeolidiidae supported the monophyly of Berghia and helped to resolve the controversy about its relationship with Spurilla. Here, specimens of Berghia from the eastern and western Atlantic were examined from molecular and morphological points of view. Berghia was found to be monophyletic, although its relationship with other aeolidiids was not resolved. The morphological studies corroborate our molecular findings and differences in external coloration can distinguish closely related species. So far, Berghia comprises 10 species: B. coerulescens, B. verrucicornis, B. norvegica, B. benteva, B. creutzbergi, B. columbina, B. rissodominguezi, B. stephanieae, B. marcusi and a new species from Senegal, B. marinae.

Abstract: The Indo-Pacific sea anemone, Boloceroides mcmurrichi, swims by coordinated lashing of tentacles and can cast off tentacles by autotomy. A predator of Boloceroides, the aeolid Berghia major, causes the anemone to detach its pedal disc and swim away after brief contact with the tentacles, a response apparently due to a chemical substance in the aeolid. Berghia generally attacks the anemone by making a lunge into the midst of the tentacles. Any tentacles seized by the aeolid autotomize, so that the anemone is not held by the aeolid when it begins to swim. Thus these two adaptations, swimming and autotomy, while not preventing predation, keep it to levels easily countered by regeneration. In electrophysiological studies on Boloceroides, the pulses assocated with the conduction systems in other anemones (NN, SS1 and SS2) were not detected. The following identifiable pulses were consistently recorded: (i) tentacle burst pulses (TBP) from isolated and intact tentacles correlated with tentacle flexions; (ii) flexion trigger pulses (FTP) recorded from oral disc and intact tentacles correlated with coordinated tentacle flexions; (iii) swimming trigger pulses (STP) recorded from the pedal disc, preceding bouts of swimming in response to the aeolid, B. major, and to mechanical and electrical stimuli; (iv) swimming arrest pulses (SAP) recorded from the pedal disc and appearing towards the end of bouts of swimming and followed almost at once by their cessation; (v) through-conduction pulses (TCP) recorded from the oral disc as a result of electrical stimuli on the column. The contrast between these pulses and those in other sea anemones probably reflects differences in the structure and mode of life of the anemone in question. A high degree of local autonomy of conduction systems is indicated. The pulses so far detected in Boloceroides reflect the behavioural capacities and the special adaptations of this atypical anemone, but pulses associated with overall coordination remain to be discovered.