A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea hares (Aplysiomorpha), and sap-sucking sea slugs (Sacoglossa).
The name relates to the rhinophore's function as an organ of "smell". Rhino- means nose from Ancient Greek ῥίς rhis and from its genitive ῥινός rhinos. "Phore" means "to bear" from Neo-Latin -phorus and from Greek -phoros (φορος) "bearing", a derivative of phérein (φέρειν).
Rhinophores are scent or taste receptors, also known as chemosensory organs situated on the dorsal surface of the head. They are primarily used for distance chemoreception and rheoreception (response to water current). [1]
The "scents" detected by rhinophores are chemicals dissolved in the sea water. The fine structure and hairs of the rhinophore provide a large surface area so that chemical detection is maximized. [2] This allows the nudibranchs to stay close to their food source (for example species of sponges) and to find mates. In the sea hare Aplysia californica , the rhinophores are able to detect pheromones. [1]
To protect the prominent rhinophores against nibbling by predators, including fish, most species of dorid nudibranchs are able to withdraw their rhinophores into a pocket beneath the skin. [2]
In reproductively mature Aplysia adults, the rhinophore is about 1 cm in length. [1] The neuroanatomical organization includes a rhinophore groove where most of the sensory cells appear to be concentrated. Its sensory epithelium contains sensory neurons that project axons back to rhinophore ganglia and dendrites that end in either a surface-exposed cilium or a small protuberance. [1]
 Scale bar is 300 μm. rg - rhinophore groove tip - rhinophore tip. |  Scale bar is 100 μm. f - folds |  Scale bar is 10 μm. ci - numerous long cilia |
In A. californica, the oral tentacles, which are situated in a more ventral position, are possibly involved in contact chemoreception and mechanoreception. [1]
Nudibranchs are a group of soft-bodied marine gastropod molluscs that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, such as "clown", "marigold", "splendid", "dancer", "dragon", and "sea rabbit". Currently, about 3,000 valid species of nudibranchs are known.
A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.
The California sea hare is a species of sea slug in the sea hare family, Aplysiidae. It is found in the Pacific Ocean, off the coast of California in the United States and northwestern Mexico.
The clade Anaspidea, commonly known as sea hares, are medium-sized to very large opisthobranch gastropod molluscs with a soft internal shell made of protein. These are marine gastropod molluscs in the superfamilies Aplysioidea and Akeroidea.
Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that over evolutionary time have either completely lost their shells, or have seemingly lost their shells due to having a greatly reduced or internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.
Opisthobranchs is now an informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping.
Aplysiidae is the only family in the superfamily Aplysioidea, within the clade Anaspidea. These animals are commonly called sea hares because, unlike most sea slugs, they are often quite large, and when they are underwater, their rounded body shape and the long rhinophores on their heads mean that their overall shape resembles that of a sitting rabbit or hare. Sea hares are however sea snails with shells reduced to a small plate hidden between the parapodia, and some species are extremely large. The Californian black sea hare, Aplysia vaccaria is arguably the largest living gastropod species, and is certainly the largest living heterobranch gastropod.
The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine gastropod mollusks within the larger clade Euopisthobranchia. Bubble shells is another common name for these families of marine gastropods, some of which have thin bubble-like shells. This clade contains more than 600 species.
Flabellinopsis iodinea, the Spanish shawl, is a species of aeolid nudibranch, a very colorful sea slug. This is a marine gastropod mollusk in the family Flabellinidae.
Elysia pusilla is a species of small sea slug, a marine gastropod mollusk in the family Plakobranchidae. It is a sacoglossan.
The spotted sea hare is a species of sea slug in the family Aplysiidae, the sea hares. It reaches a length of up to 20 cm (7.9 in) and is found in the northeast Atlantic, ranging from Greenland and Norway to the Mediterranean Sea.
Chromodoris westraliensis is a species of very colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.
The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors. Gastropods have no sense of hearing.
Aplysia vaccaria, also known as the black sea hare and California black sea hare, is a species of extremely large sea slug, a marine, opisthobranch, gastropod mollusk in the family Aplysiidae. It is the largest sea slug species.
Chromodoris orientalis is a species of colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae. Sea slugs are generally very beautifully colored organisms with intense patterns and ranging in sizes. The Chromodoris orientalis specifically is a white sea slug with black spots in no particular pattern with a yellow, orange, or brown in color ring around its whole body and on its gills. There is much discussion on where it is found, what it eats, how it defends itself without a shell, and its reproduction methods. This is all sought after information because there is not much known about these animals.
Skenea ossiansarsi is a species of sea snail, a marine gastropod mollusk in the family Skeneidae.
Berghia stephanieae is a species of sea slug, an aeolid nudibranch. It is a marine gastropod mollusc in the family Aeolidiidae. It was previously known as Aeolidiella stephanieae.
Aeolidiella alderi is a species of sea slug, an aeolid nudibranch in the family Aeolidiidae. It is native to northwestern Europe where it occurs in the intertidal zone. It is a predator and feeds on sea anemones.
Aplysia morio, the Atlantic black sea hare or sooty sea hare, is a species of sea slug, a marine gastropod mollusk in the family Aplysiidae, the sea hares. It lives in warm waters in the Caribbean Sea and off the south and southeastern coast of the United States, where it feeds on seaweed.
Aplysia gigantea is a species of sea slug, a shell-less marine gastropod mollusk in the family Aplysiidae. The species was first described in the Journal of the Malacological Society of Australia in 1869. A. gigantea is also known more commonly as the sea hare due to their posterior chemosensory tentacles resembling a hare's ear. A. gigantea is the largest known species in Australia of the opisthobranch genus. The species is known to have toxic effects on terrestrial organisms, particularly domestic dogs. Exposure to this species with dogs has been associated with the development of neurotoxicosis, with symptoms ranging from respiratory distress to tremors, muscle fasciculations, and seizures.
This article incorporates CC-BY-2.0 text (but not under GFDL) from reference. [1]
