DIVELOG JUNE 406

Eubranchus sp. (sp. 18). An undescribed Eubranchus with long tubular cerata where the circlets of tubercles are crowded and confined towards the apices.

hydroid food. Often it is their spawn, laid upon the hydroid branches, that will betray their presence to the searching photographer. Knowing food sources is an excellent aid to finding sea slugs and with many species of Eubranchus the same applies. At times you might be fortunate to find several of the one species preying upon a single hydroid. The images in this NudiNote are of Eubranchus species from Indo-Pacific tropical to sub-tropical regions. This serves to explain the reason why two thirds of those illustrated here are currently undescribed. (Note: sp. numbers in brackets in the captions refer to species on the NudibranchDomain website.) - References relating to this article will be appended to a related article to be placed on NudibranchDomain.org in the near future. Eubranchus mandapamensis. Recognised by the distinctive colour pattern on the cerata apices. As well as circlets of tubercles on the cerata the rhinophores bear tubercles as well.

the rhinophores are known. Oral tentacles are usually much shorter than rhinophores. The body is elongate and narrow with a wide foot, often wider than the body; useful for those that need to grip and traverse hydroid branches. The anterior corners of the foot may be rounded or angular or even further developed into propodial tentacles. For those who are interested, the Eubranchus possess a triseriate radula (three toothed), a feature that assists taxonomists to separate them from similar looking species in other related genera. The diet of Eubranchus , where it is known, consists of colonial hydroids, either the type that are free growing or others that are epibiotic on various kinds of algae. Not all species of Eubranchus are observed in the open with many being found in and under coral rubble in the tropic and subtropical habitat. Most are small, less than 20 mm, (but a few do grow over 40 mm) with many being less than 10 mm in length and often quite cryptic on their

Eubranchus sp. (sp. 16). Also with distinctive colouration to the cerata apices. The digestive gland forms a small crucifix shape on the distal half.

Eubranchus sp. (sp. 23). A translucent species with the maroon-coloured digestive gland visible through the notum and cerata, the cerata capped with white-frosted cones.

21

www.divelog.net.au

DIVE LOG Australasia #406 - June ‘24