Meeting Abstract

P1.108  Tuesday, Jan. 4  Description of a novel chemosensory organ in the nudibranch Tritonia diomedea GALLAGHER, CA*; ROHOZINSKI, D; STANTON, K; MURRAY, JA; CAIN, SD; Cal. State U. East Bay; U. Washington; U. Washington; Cal. State U. East Bay; Eastern Oregon U shaun.cain@eou.edu

The nudibranch gastropod Tritonia diomedea has an a pair of rhinophores that are homologous to the posterior tentacles of the ancestral gastropods, and an oral veil that is in-part derived from the anterior tentacles of ancestral gastropods. The rhinophores have been shown to be distance chemoreceptors that contribute to the detection of odors emitted by prey, predators, and conspecifics. The oral veil is mechanosensory, has the ability to distinguish the taste of prey and predator, and has been shown to be necessary for the detection of tidal flow direction. The oral veil of this species has ~18 white tips, 2-5mm long, which serve as finger-like touch-sensitive papillae oriented anteriorly that are used to explore items they contact by crawling. In contrast, the 2 most lateral tips are 5-10mm long, are oriented ventrally during crawling, and have a ciliated groove along the ventro-medial surface. This has previously been named the Organ of Hancock, but it may not be homologous to this organ. The groove has motile cilia oriented to transport fluid from the tip towards the base at 1-2 mm/s. The groove may be chemosensory, as it sometimes pinched closed when exposed to 7% Sumi ink in seawater (avg speed 0.9±0.2 mm/s), but did not do so when exposed to chemically-neutral glass microbeads (avg speed 1.3±0.2 mm/s). The cilia continued to beat after the tip is excised from the body (0.5-1.2 mm/s), and we plan to explore which neurons might control the rate of cilia-driven flow. We propose that these organs are oriented such that they could be capable of sniffing odors off the soft bottom, perhaps transporting odors from the viscous layer to chemosensory cilia on the oral veil.