The ''Hydromylidae'' are monotypic

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of small

sea slug 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 ...

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 * ...

opisthobranch 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. Euopisth ...

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 ...

s in the suborder

Gymnosomata Sea angels ( clade Gymnosomata) are a large group of small free-swimming sea slugs, not to be confused with Cnidarians (Jellyfish and other similar creatures), classified into six different families. They are pelagic opisthobranchs in the clade ...

, the

sea angel Sea angels (clade Gymnosomata) are a large group of small free-swimming sea slugs, not to be confused with Cnidarians (Jellyfish and other similar creatures), classified into six different families. They are pelagic opisthobranchs in the clade G ...

s. ''Hydromyles'' species are

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

and

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

Description

The small pelagic snails lack shells (except in their early

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

nic stage). They are carnivores, equipped with swimming parapoda (fleshy, wing-like outgrowths), strong jaws and grasping tentacles, often with suckers resembling those of

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

Genera and species

Genera and species within the family Hydromylidae include: Genus ''

Hydromyles ''Hydromyles'' is a monotypic genus of small sea slugs, marine opisthobranch gastropod molluscs in the family Hydromylidae. ''Hydromyles'' species are pelagic, carnivorous and viviparous. They are found in waters around Japan, South Korea, eastern ...

'' Gistl, 1848 * ''

Hydromyles globulosus ''Hydromyles globulosus'' is the only species of sea slug in the family Hydromylidae. It is commonly found in the Indo-Pacific Ocean. The species is pelagic, carnivorous and viviparous. They are unique among sea angels in that they brood their y ...

'' (Rang, 1825) ** Distribution: East

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

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, western

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

. ** Description: This pteropod seizes its prey with its

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs 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 ...

. Contrary to most gymnosomatiids, this pteropod has no proboscis and no hooks. It is also unique by having, close to the anal aperture, a sac for hatching its eggs. The

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e develop in this sac and are born as fully developed snails. In other words, this species is

References and external links

* Martoja, M., 1965. Sur l'incubation et l'existence possible d'une glande endocrine, chez Hydromyles globulosa Rang (Halopsyche Gaudichaudi Keferstein), gastéropode gymnosome. -- C.R. hebd. Séanc. Acad. Sci. Paris, 260: 2907-2909.
photo of ''Hydromyles globulosus''
{{Taxonbar, from=Q17122127 Taxa named by Alice Pruvot-Fol