''Aplysia gigantea'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of sea

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

, a shell-less

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Aplysiidae 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 sh ...

. 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.

Distribution

''Aplysia gigantea'' are commonly found near the southwestern corner of Western Australia, in soft sediment or reef environments. They are found in shallow water, ranging from 0-20m in depth. ''A. gigantea'' are most commonly witnessed from January to March, where beach strandings of this species can number in the hundreds. ''A. gigantea'' are found most often in waters that range from 13.1-23.2 °C. The species has not yet been assessed by the IUCN, and thus its conservation status remains unknown.

Description

''A. gigantea'' are known to be able to grow up to 60 cm long, making it one of the largest species of sea hare in Australia. They are usually a dark brown or black color. Additionally, they are distinguished by large paradopia on their backs, which function as limbs allowing the sea hare to swim for short periods of time. The species also has scent and taste receptors known as rhinophores, located on the upper side of its head. These organs resemble a hare's ears and are responsible for its more colloquial name of sea hare. The sea hare's eyes are also located beneath the rhinosphores, and are able to sense light and shadow. Its gills, as well as an internal, calcified shell are located near the organism's heart. The shell itself is particularly fragile, and the paradopia serve a secondary function in both enclosing and protecting it. The adults of this species are also herbivorous in nature, with a diet that primarily consists of algae.

Defense

''A. gigantea'' is able to produce ink and secretions from two main secretory glands that render it hidden or toxic to predators. When ingested by domestic dogs, several symptoms have been recorded, including respiratory issues, ptyalism, emesis, ataxia, and hyperaesthesia. It is suggested the diet of ''A. gigantea'', consisting of organisms such as red algae, provides the molecules needed to create toxins.

Reproduction

''A. gigantea'' mate during summer and early autumn. ''A. gigantea'' are hermaphrodites and often mate in numbers ranging from 2 to approximately 20, producing orange colored spawn. In these mating groups, one individual will utilize only female or male reproductive organs respectively, while other participants use both. The eggs produced by ''A. gigantea'' are in long and stringy clumps, and hatch into planktonic larvae which feed on microscopic algae.

References

{{Taxonbar, from=Q13386097 gigantea Gastropods described in 1986