Gastropteridae, the bat-winged slugs, is a

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 ...

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 ...

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 ...

mollusc 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 esti ...

s in the

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Philinoidea Philinoidea is a taxonomic superfamily of sea slugs, specifically headshield slugs, marine gastropod mollusks in the order Cephalaspidea. MolluscaBase eds. (2021). MolluscaBase. Philinoidea Gray, 1850 (1815). Accessed through: World Register of M ...

of the clade

Cephalaspidea 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.Jörger K. M., Stöger I., Kano Y., Fukuda H., ...

, the headshield slugs and bubble snails. The greatest diversity of these colourful small slugs is in the tropical and sub-tropical Indo-Pacific region.

Description

Gastropteridae is a fairly diverse family containing four genera and thirty-three described species. Adults have an internal reduced shell or no shell at all. The body is fairly short, usually under in length, but exceptionally up to . Compared to the closely related philinids and the aglajids, the mantle cavity is small, and the gills are located further forward, in an exposed position. In most species, the hind end of the headshield is narrowed, raised and curved forward, sometimes being further forward than the front edge of the head. A

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 ...

is present, but no jaws. These slugs are mostly brightly coloured and distinctively patterned. Gastropterids have

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; plural: parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed ...

(large outgrowths from the mantle wall) and can swim by flapping these, which has led to them being referred to as "bat-winged slugs". The nervous system has a well-developed brain and these slugs exhibit various elaborate behavioural traits.

Distribution and habitat

Most gastropterids are found in the tropical and sub-tropical parts of the Indo-Pacific region. Most species have been described since the middle of the twentieth century and there are many undescribed species. '' Gastropteron'' is the only genus with a presence in the Atlantic Ocean.

Ecology

The ecology of gastropterids has been little studied, but most '' Sagaminopteron'' species have been observed to feed on sponges that do not contain

spicules Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

. At least some '' Siphopteron'' species are found on

macroalgae Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as k ...

and

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

es. Gastroperids are

simultaneous hermaphrodite Simultaneous hermaphroditism is one of the two types of hermaphroditism, the other type being sequential hermaphroditism. In this form of hermaphroditism an individual has sex organs of both sexes and can produce both gamete types even in the sam ...

s. ''Siphopteron'' species have a complex mating behaviour, with each of two slugs attempting to use spines for hypodermic insemination of the other one. This is the case in '' Siphopteron quadrispinosum'', where each slug attempts to inject prostate fluid into the other having stabbed it with a stylet, part of a two-pronged

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...

. The two slugs circle clockwise around each other, each probing and attempting to pierce the underside of the other with the stylet while avoiding getting pierced itself. When one or both is successful, the penis is thrust into the other slug's

gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female it is the ...

, where further spines hold it in place, and mating takes place. Copulation may be reciprocal or only one slug may be successful.

Genera

The following genera are recognised by the

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialist ...

: * '' Enotepteron'' Minichev, 1967 * '' Gastropteron'' Kosse, 1813 - synonym: ''Sarcopterus'' Rafinesque, 1814 * '' Sagaminopteron'' Tokioka & Baba, 1964 * '' Siphopteron'' Gosliner, 1989

References

External links