The Notobranchaeidae, or "naked sea butterflies", are a

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

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 ...

of floating sea

slugs 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 sma ...

, specifically under the subclass Opistobranchia, also called "

sea angels A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...

". Similar to other

Pteropods Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. Most live in the top 10 m of the ocean and are less than 1 cm long. ...

, these

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

marine

heterobranch Heterobranchia, the heterobranchs (meaning "different gill"), is a taxonomic clade of snails and slugs, which includes marine, aquatic, and terrestrial gastropod molluscs. Heterobranchia is one of the main clades of gastropods. Currently Hetero ...

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 ...

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

are holoplanktonic.

Morphology

While they are not particularly strong swimmers, the foot of these organisms is modified into wing-like structures, called

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

that they employ for locomotion. Additionally, like other Pteropods of the order

Gymnosomata Sea angels (clade Gymnosomata) are a large group of small free-swimming sea slugs, classified into six separate families. They are pelagic opisthobranchs in the clade Gymnosomata within the larger mollusc clade Heterobranchia. Sea angels were pre ...

, Notobrachaeidae lack shells entirely as adults.Pierrot-Bults, Annelies & Peijnenburg, K. (2015). Pteropods. Encyclopedia of marine geosciences. 1-10. However, they do possess a shell earlier on in their lives. They are also defined by how they possess a posterior gill, strong jaws, grasping tentacles that frequently possess suckers resembling those of

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

s, and usually buccal cones as well.

Behavior

Like other members of the clade Gymnosomata, Notobrachaeidae are highly specialized holoplanktonic carnivores.Lemus, E., Sanvicente-Añorve, L., Hermoso-Salazar, M, Flores-Coto, C. (2014). "The holoplanktonic Mollusca from the southern Gulf of Mexico Part 2: pteropods" (PDF). ''Cahiers de Biologie Marine''. 55: 241–258 – via ResearchGate. In other words, they spend their entire lives hunting in the water column and cannot swim against the column. Also like other members of this clade, Notobrachaeidae feed are very specific prey, with a species in this clade usually specializing in hunting one specific genus of thecosomes, which are also known as "sea butterflies," and form a sister clade to Gymnosomata with the primary difference being how adults of that clade possess shells into adulthood while Gymnosomata do not.

Distribution

Members of this family are found globally throughout the upper reaches of the water column, in the pelagic zone, most commonly the epipelagic zone. Following the trend of Pteropods in general, they tend to have the highest species diversity

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and subtropical

latitudes In geography, latitude is a geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at the south pole to 90° at the ...

but are less abundant under these conditions. Conversely, they are more abundant but possess less variety in terms of species closer to the

north North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and south poles. However, even in the tropics, they generally appear in high concentrations, resulting in their frequently playing important roles in

planktonic Plankton are the diverse collection of organisms that drift in water (or air) but are unable to actively propel themselves against currents (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they pro ...

food webs.

Genera and species

Genera and species in the family Notobranchaeidae include: Genus: Notobranchaea Pelseneer, 1886 * '' Notobranchaea bleekerae'' van der Spoel & Pafort-van Iersel, 1985 ** Distribution : Oceanic * '' Notobranchaea grandis'' Pruvot-Fol, 1942 ** Distribution : Oceanic ** Length : 15 mm * '' Notobranchaea hjorti'' (Bonnevie, 1913) * '' Notobranchaea inopinata'' Pelseneer, 1887 ** Distribution : Oceanic ** Length : 5 mm * '' Notobranchaea longicollis'' (Bonnevie, 1913) * '' Notobranchaea macdonaldi'' Pelseneer, 1886 ** Distribution : Bermuda, Oceanic ** Length : 5 mm * '' Notobranchaea tetrabranchiata'' Bonnevie, 1913 ** Distribution : Oceanic ** Length : 16 mm * '' Notobranchaea valdiviae'' Meisenheimer, 1905 ;Genera brought into synonymy: * ''Microdonta'' Bonnevie, 1913: synonym of ''Notobranchaea'' Pelseneer, 1886 (invalid: junior homonym of ''Microdonta'' Dejean, 1835 oleoptera ''Schleschia'' is a replacement name) * ''Prionoglossa'' Tesch, 1950: synonym of ''Notobranchaea'' Pelseneer, 1886 * ''Schleschia'' Strand, 1932: synonym of ''Notobranchaea'' Pelseneer, 1886

References

* Bouchet, P., Rocroi, J.-P. (2005). Classification and nomenclature of gastropod families. ''Malacologia.'' 47(1-2): 1-397 . *MolluscaBase (2019). MolluscaBase. Notobranchaeidae Pelseneer, 1886. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=23080 on 2019-04-16 *Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca. in: Costello, M. J. et al. (eds), European Register of Marine Species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Patrimoines Naturels. 50: 180-213

External links

*
Bonnevie K. (1913) Pteropoda from the "Michael Sars" North Atlantic Deep-Sea Expedition 1910. Report on the Scientific Results of the "Michael Sars" North Atlantic Deep Sea Expedition 1910 3(1) 1-85, pls. 1-9.
{{Taxonbar, from=Q3168852 Gastropod genera