Paralepididae
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Barracudinas are any member of the marine
mesopelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs. ...
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 ...
Paralepididae: 50 or so extant species are found almost worldwide in deep waters. Several genera, including ''
Holosteus ''Holosteus'' (meaning "complete skeleton") is a genus of prehistoric barracudina found in Eocene and Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 mi ...
'' and ''
Drimys ''Drimys'' is a genus of seven species of woody evergreen flowering plants, in the family Winteraceae. The species are native to the Neotropics, ranging from southern Mexico to the southern tip of South America.Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...
epoch. The
generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...
name ''Paralepis'' (for which the family is named) is from
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
- ''para'' meaning "somewhat", ' meaning "scaled".


Description

Barracudinas are elongated, slender fish with large eyes, and a pointed snout containing fang-like teeth. This gives them some superficial resemblance to
barracuda A barracuda is a large, predatory, ray-finned, saltwater fish of the genus ''Sphyraena'', the only genus in the family Sphyraenidae, which was named by Constantine Samuel Rafinesque in 1815. It is found in tropical and subtropical oceans worldw ...
s (family
Sphyraenidae A barracuda is a large, predatory, ray-finned, saltwater fish of the genus ''Sphyraena'', the only genus in the family Sphyraenidae, which was named by Constantine Samuel Rafinesque in 1815. It is found in tropical and subtropical oceans worldwi ...
), although the two groups are not closely related. Barracudinas are actually related to lizardfish (order
Aulopiformes Aulopiformes is a diverse order (biology), order of Marine (ocean), marine ray-finned fish consisting of some 15 Extant taxon, extant and several prehistoric family (biology), families with about 45 genera and over 230 species. The common names ...
; suborder Alepisauroidei) and are most closely aligned with lancetfish (family
Alepisauridae Lancetfishes are large oceanic predatory ray-finned fishes in the genus ''Alepisaurus'' ("scaleless lizard") in the monotypic taxon, monogeneric family Alepisauridae. Lancetfishes grow up to in length. Very little is known about their biology, ...
), hammerjaws (family Omosudidae) and daggertooths (family
Anotopteridae The daggertooths (genus ''Anotopterus'') are a genus of marine mesopelagic fish in the order Aulopiformes, the sole genus of the family Anotopteridae. They are found in oceans worldwide, but prefer cooler waters. Description Daggertooths are sim ...
). Like their close relatives, barracudinas lack
swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ (anatomy), organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift ...
s and are simultaneous
hermaphrodites 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 ...
, a reproductive mode which is rare among vertebrates. The largest species of barracudina grow up to in length. Barracudinas have some unique adaptations to life in the deep
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 ...
that are thought to help with camouflage: most barracudina species have a subdermal layer of
guanine Guanine () (symbol G or Gua) is one of the four main nucleotide bases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside ...
that imparts a kaleidoscopic color to their appearance in life and it is thought this refracts the dim light of mesophotic waters around their bodies. The smaller, more derived species of barracudinas in the genera ''Lestidiops'', ''Lestidium'', ''Lestrolepis'' and ''Stemonosudis'' possess very few scales and their skin is almost completely transparent, making it difficult for them to be seen underwater. Barracudinas, like many other deep-sea fishes, have darkly pigmented gut linings which are thought to help conceal
bioluminescent Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...
prey such as lanternfish (family Myctophidae). Species in the genus ''Lestrolepis'' have a bioluminescent organ located ventrally along their stomachs which likely helps in
countershading Countershading, or Thayer's law, is a method of camouflage in which animal coloration, an animal's coloration is darker on the top or upper side and lighter on the underside of the body. This pattern is found in many species of mammals, reptile ...
against downwelling light, camouflaging their silhouettes to would be predators below. Other species have a bioluminescent organ which have evolved from liver tissue.The first report of luminescent liver tissue in fishes: evolution and structure of bioluminescent organs in the deep-sea naked barracudinas (Aulopiformes: Lestidiidae)
/ref>


Ecology and life history

Barracudinas are known to inhabit
mesopelagic The mesopelagic zone (Greek language, Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light ...
depths throughout the world's oceans, and are predators of fish, shrimps, and squids. While many barracudina species can be found at depths of 2000 m, their highest abundances tend to occur between 200 and 1000 m. Barracudinas are not thought to participate in
diel vertical migration Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The adjective "diel" ( IPA: , ) comes from , and refers to a 24-hour ...
. While they are rarely caught by fisheries, they are frequently documented in the guts of pelagic predators such as
tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...
,
swordfish The swordfish (''Xiphias gladius''), also known as the broadbill in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are the sole member of the Family (biology), family Xiphiidae. They ...
,
lancetfish Lancetfishes are large oceanic predatory ray-finned fishes in the genus ''Alepisaurus'' ("scaleless lizard") in the monogeneric family Alepisauridae. Lancetfishes grow up to in length. Very little is known about their biology, though they are ...
,
Cuvier's beaked whale Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Beaked whale, Ziphiidae. It is smaller than most baleen whales—and indeed the larger Toothed whal ...
s, and
blue shark The blue shark (''Prionace glauca''), also known as the great blue shark, is a species of requiem shark, in the family Carcharhinidae and the only member of its genus which inhabits deep waters in the world's temperate and tropical oceans. Ave ...
s. First-hand accounts from the ''
Bathyscaphe Trieste ''Trieste'' is a Swiss-designed, Italian-built deep-diving research bathyscaphe. In 1960, it became the first crewed vessel to reach the bottom of Challenger Deep in the Mariana Trench, the deepest point in Earth's seabed. The mission was the fi ...
'' reported behavioral observations of ''Lestrolepis intermedia'' rapidly swimming vertically through the water column like "silvery javelins" glowing "a brilliant yellow" from their bioluminescent organs. They were also observed hovering in the water and rapidly reorienting themselves from facing upwards to facing downwards as if scanning for predators and/or prey. If this behavior is common to all species of barracudina is not known, as it has not been observed since. Very little is known of the
spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
habits of these fish. While both sperm and eggs are present in
gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...
s, spawning has never been observed. Planktonic disposition and transmission of their early larva indicate that the eggs are fertilized and dispersed in the plankton. While specific life histories differ among species and genera, postlarval barracudina size classes are found more frequently within proximity to
continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...
escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Due to the similarity, the term '' scarp'' may mistakenly be incorrectly used inte ...
s at certain times of the year. However, this could also be a sampling artifact, since barracudina are only rarely caught by fisheries-independent sampling.


References


External links

* * {{Taxonbar, from=Q582420 Paralepididae