''Hiatodoris'' is a

monotypic genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

sea slugs 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 (marine gastropod mollusks) that, over evolutionary t ...

, specifically

dorid ''Doridacea'' is a taxonomic grouping of dorid nudibranchs, shell-less marine gastropod mollusks.Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005''Classification and nomenclator of gastropod familie ...

nudibranchs. They are 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 ...

molluscs 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

Discodorididae Discodorididae is a Taxonomy (biology), taxonomic family (biology), family of sea slugs, specifically dorid nudibranchs, marine (ocean), marine gastropod mollusks in the superfamily Doridoidea.Bouchet, P. (2011). Discodorididae. Accessed through: ...

. The only species is ''Hiatodoris fellowsi'' commonly known as the Snowball Sea Slug or Fellow's Nudibranch. It was previously known as ''Peltodoris fellowsi''.

Description & Anatomy

''Hiatodoris fellowsi'' has an oval-like firm and white body, black

rhinophores 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 hare ...

and

gills A gill () is a respiratory organ that many 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 respiration on land provided they are ...

, and white egg masses. It is a small species with a maximum size of about 51 mm. As most nudibranchs, this species is a

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

. The ejaculatory and vaginal ducts have their own

orifices A body orifice is any opening in the body of an animal. External In a typical mammalian body such as the human body, the external body orifices are: * The nostrils, for breathing and the associated sense of smell * The mouth, for eating, drinki ...

. It has a straight ejaculatory duct with a tight and convoluted

vas deferens The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male reproductive system of many vertebrates. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididyma ...

. Its

prostate gland The prostate is an male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemica ...

has no

prostatic duct The prostatic ducts (or prostatic ductules) open into the floor of the prostatic portion of the urethra, and are lined by two layers of epithelium, the inner layer consisting of columnar and the outer of small cubical cells. Small colloid masses, ...

, but is large and finely lobulate. The spermatocyst and

spermatheca The spermatheca (pronounced : spermathecae ), also called ''receptaculum seminis'' (: ''receptacula seminis''), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, Oligochaeta worms and certain other in ...

are arranged semiserically, where the spermatheca is a little bigger than the spermatocyst and both are

ovate Ovate may refer to: * Ovate (egg-shaped) leaves, tepals, or other botanical parts *Ovate, a type of prehistoric stone hand axe * Ovates, one of three ranks of membership in the Welsh Gorsedd * Vates or ovate, a term for ancient Celtic bards ...

. ''Hiatodoris fellowsi'' has a long vaginal duct with a lose and convolute opening into the spermatocyst. Its uterine duct is passes from the spermatocyst to a junction where the ampullary duct, prostate, and

mucous gland Mucous glands, also known as muciparous glands, are found in several different parts of the body, and they typically stain lighter than serous glands during standard histological preparation. Most are multicellular, but goblet cells are single-c ...

are. ''Hiatodoris fellowsi'' also has a

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

that is simply

hamate The hamate bone (from Latin language, Latin wiktionary:hamatus, hamatus, "hooked"), or unciform bone (from Latin language, Latin ''wikt:uncus, uncus'', "hook"), Latin os hamatum and occasionally abbreviated as just hamatum, is a bone in the huma ...

, and measures between 75 and 450

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

long. The teeth curve at a wide angle resembling
makau
with a small outer

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

Distribution and habitat

''Hiatodoris fellowsi'' can be found throughout the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

including the

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

, Henderson Island, Hachijo Island,

Lifou Lifou () is a communes of France, commune of France in the Loyalty Islands Province of New Caledonia, Pacific Ocean. Geography Lifou is made up of Lifou Island, the largest and most heavily populated of the Loyalty Islands, its smaller neighbou ...

. It can be found under shaded cliffs and ledges at depths between 3 and 24 meters, feeding on

sponges Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and ar ...

Links to Photos

* https://seaslugsofhawaii.com/species/Hiatodoris-fellowsi-e.html * https://www.marinelifephotography.com/marine/mollusks/slugs/peltodoris-fellowsi.htm

References

Discodorididae Monotypic gastropod genera {{Discodorididae-stub