''Tritonicula hamnerorum'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of dendronotid

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs, belonging to the order Nudibranchia, that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have b ...

. It is a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Tritoniidae Tritoniidae is a taxonomic family of nudibranchs in the suborder Cladobranchia, shell-less marine gastropod molluscs.MolluscaBase (2018)Tritoniidae Lamarck, 1809.Accessed on 2021-01-01 This family includes some of the largest known nudibranch ...

. A number of Caribbean species of ''Tritonia'' were moved to a new genus ''Tritonicula'' in 2020 as a result of an integrative taxonomic study of the family Tritoniidae.

Distribution

''Tritonicula hamnerorum'' is found in the Caribbean area with its range extending from the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

Curaçao Curaçao, officially the Country of Curaçao, is a constituent island country within the Kingdom of the Netherlands, located in the southern Caribbean Sea (specifically the Dutch Caribbean region), about north of Venezuela. Curaçao includ ...

and the

Cayman Islands The Cayman Islands () is a self-governing British Overseas Territories, British Overseas Territory, and the largest by population. The territory comprises the three islands of Grand Cayman, Cayman Brac and Little Cayman, which are located so ...

.Rudman, W.B., 2002 (January 20
''Tritonia hamnerorum'' Gosliner & Ghiselin, 1987.
nSea Slug Forum. Australian Museum, Sydney.MolluscaBase eds. (2021)
MolluscaBase. ''Tritonicula hamnerorum'' (Gosliner & Ghiselin, 1987).
Accessed through: World Register of Marine Species on 2021-01-05 The distribution of ''Tritonicula hamnerorum'' includes Florida, Mexico, Belize, Bahamas, Cayman Islands and Panama.

Description

The shape of the body is elongate and narrow.

Rhinophore A rhinophore is one of a pair of Chemoreceptor, chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, Marine (ocean), marine gastropod opisthobranch mollusks suc ...

s are long with branched tips. Rhinophoral sheaths are elevated with an irregular edge. Edge of the oral veil has relatively long appendages. Background colour is translucent gray with a series of irregular, longitudinal, thin white lines that run along the length of the dorsum. Its colour, pink or pale lavender, matches the colour of its host sea fan, ''Gorgonia ventalina''. There are about twenty thin white stripes running the length of the body. There are series of nine, sparsely

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and ...

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s or

cerata :''The tortrix moth genus ''Cerata'' is considered a junior synonym of ''Cydia (genus), Cydia. Cerata, singular ceras, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine animal, marine opi ...

down each side of the body. ''Tritonicula hamnerorum'' is up to long.Welch J. J. (2010). "The “Island Rule” and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLoS ONE'' 5(1): e8776. doi:10.1371/journal.pone.0008776.

Ecology

Habitat

Found in shallow water reef habitats with its host ''Gorgonia ventalina''. Minimum recorded depth is 2 m. Maximum recorded depth is 4 m.

Feeding habits

''Tritonicula hamnerorum'' seems to feed exclusively on ''

Gorgonia ventalina ''Gorgonia ventalina'', the common sea fan and purple sea fan, is a species of sea fan, an octocoral in the family Gorgoniidae. It is found in the western Atlantic Ocean and the Caribbean Sea. Description ''G. ventalina'' is a fan-shaped c ...

'' and extensive searches failed to locate any individuals on other parts of the reef, on

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

s or in

seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...

beds. ''Gorgonia ventalina'' contains

secondary metabolite Secondary metabolites, also called ''specialised metabolites'', ''secondary products'', or ''natural products'', are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved ...

s including one, " julieannafuran", which is distasteful to predators. ''Tritonicula hamnerorum'' seems to be unaffected by this and sequesters the compound, accumulating it in its tissues. This in turn makes the nudibranch distasteful to predatory fish, such as the bluehead wrasse (''

Thalassoma bifasciatum ''Thalassoma bifasciatum'', the bluehead, bluehead wrasse or blue-headed wrasse, is a species of marine ray-finned fish, a wrasse from the family Labridae. It is native to the coral reefs of the tropical waters of the western Atlantic Ocean. In ...

''), which avoid consuming this species. This species reportedly feeds on the octocorals ''Gorgonia ventalina'' and ''

Gorgonia flabellum ''Gorgonia flabellum'', also known as the Venus fan, Venus sea fan, West Indian sea fan, purple gorgonian seafan, and common sea fan, is a species of sea fan, a sessile colonial soft coral. Description The Venus sea fan is a delicate-looking ...

''.

Life cycle

This nudibranch lays small clusters containing several hundred

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

capsules on branches of its

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

coral. The morphology of the veliger larvae that hatch from these eggs suggest that they are

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic. Juveniles feed on the soft tissue overlying the skeleton of the sea fan while adults feed on the polyps. Within its range, the distribution of ''Tritonicula hamnerorum'' is very patchy. Usually one or a few individuals are found on a single sea fan, but very occasionally, as happened in an outbreak in 1992, a large number of juveniles occur. On this occasion, 1,700 were found in a dense aggregation on one side of an area of sea fan measuring . Because these juveniles were all the same size, researchers hypothesized that they may not have become planktonic but may have remained on the host after hatching and fed on plankton, like their host, before undergoing

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

. It was found on gorgonian sea fans in dense aggregations also in Panama.

References

This article incorporates Creative Commons (CC-BY-4.0) text from the referenceGoodheart J. A., Ellingson R. A., Vital X. G., Galvão Filho H. C., McCarthy J. B., Medrano S. M., Bhave V. J., García-Méndez K., Jiménez L. M., López G. & Hoover C. A. (2016). "Identification guide to the heterobranch sea slugs (Mollusca: Gastropoda) from Bocas del Toro, Panama". ''Marine Biodiversity Records'' 9(1): 56. {{Taxonbar, from=Q7844363 Tritoniidae Gastropods described in 1987