Overview

Comprehensive Description

Etmopterus spinax (Linnaeus, 1758)

Aegean Sea : 1200-27 (1 spc.), 14.07.1981 , Goekova Bay , trawl , 600 m, Nezih Bilecik .

  • Nurettin Meriç, Lütfiye Eryilmaz, Müfit Özulug (2007): A catalogue of the fishes held in the Istanbul University, Science Faculty, Hydrobiology Museum. Zootaxa 1472, 29-54: 32-32, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:428F3980-C1B8-45FF-812E-0F4847AF6786
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Biology

Found on the outer continental shelves and upper slopes. Feeds on small fishes, squids, and crustaceans. Ovoviviparous, with number of young from 6 to 20 in a litter. Utilized for fishmeal and prepared dried salted for human consumption. Depth range reported at 70m-2000m in Ref. 35388.
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Distribution

Range Description

Mediterranean Sea: found in the Western Mediterranean (Spain, France, Italy, Albania, Malta, Libya, Tunisia, Algeria, Morocco).

Northeast, eastern central and southeast Atlantic: Iceland and Norway south to Senegal, Sierra Leone, Côte d'Ivoire to Nigeria, Cameroon to Gabon, Azores and Cape Verde Islands (Compagno in prep.).
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Eastern Atlantic: Iceland, Norway, and the western Mediterranean to Morocco, Senegal, Sierra Leone, Côte d'Ivoire to Nigeria, Cameroon to Gabon, Azores, Cape Verde, and Cape Province, South Africa.
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Western Baltic Sea, northern North Sea, Mediterranean Sea, eastern Atlantic: Iceland and Norway to Senegal.
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Physical Description

Size

Maximum size: 600 mm TL
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Max. size

60.0 cm TL (male/unsexed; (Ref. 247)); max. published weight: 850 g (Ref. 40637)
  • Compagno, L.J.V. 1984 FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
  • IGFA 2001 Database of IGFA angling records until 2001. IGFA, Fort Lauderdale, USA. (Ref. 40637)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Etmopterus spinax is found on the outer continental shelves and upper slopes at depths of 70–2,000 m, mostly between 200 and 500 m (Compagno in prep.). In the Mediterranean E. spinax has been recorded from 300–2,000 m depth (F. Serena pers. obs. 2007). In the Adriatic Sea it is reported down to 1,200 m depth (Ungaro et al. 2001). In the Thyrrenian Sea, Italy, Cecchi et al. (2004) found the typical depth distribution to be 322–633 m. In the Gulf of Valencia, Spain it is commonly caught by commercial bottom trawls between 300 and 675 m, and is slightly more abundant below 550 m (Guallart 1990). In the northeast Atlantic E. spinax has been caught at depths of 400–1,000 m (Merrett et al. 1991a,b; Bridger 1978). In general, smaller (<30 cm) individuals tended to occur at depths of less than 500 m whilst mature individuals were found at mid-depths (500 to 600 m) (P. Crozier pers. comm.). In Sierra Leone E. spinax is found as shallow as 200 m but is a dominant species at depths greater than 400 m (Litvinov 1993). In Morocco E. spinax is captured at depths of 400–800 m, is a resident species at 400–500 m and is dominant at 600 m and sub-dominant at 600–900 m (Litvinov 1993).

Estimated age at maturity is five to six years (Cecchi et al. 2004), although longevity is unknown for the species. Size at maturity has various estimates: females mature between >30–46 cm total length (TL); 33–36 cm (Compagno in prep); 38–40 cm (Capapè et al. 2001, Cecchi et al. 2004); 46 cm (n=76) in the northeast Atlantic (Crozier unpub. data); 31 cm in South Portugal (Coelho and Erzini 2005); and >30 cm in the Adriatic (Ungaro pers. comm.). Males mature between 25–38 cm: 33–36 cm TL (Compagno in prep.); 35 cm (Capapè et al. 2001); 38 cm (n=105) in the northeast Atlantic (Crozier unpub. data); 25 cm in South Portugal (Coelho and Erzini 2005); and 28–30 cm in the Adriatic (N. Ungaro pers. comm.). The maximum size recorded for E. spinax was a female of 60 cm TL but specimens are rarely larger than 45 cm (Compagno in prep.).

The velvet belly is ovoviviparous producing 6–20 pups per litter (Compagno in prep, Fischer et al. 1987), with a mean ovarian fecundity of 18 eggs (n=14) and a mean embryonic fecundity of 10 pups (n=15) (Crozier unpub. data). In the Thyrrenian Sea mature females were observed at 40 cm TL carrying six embryos of 6.5 cm TL in the uterus (Cecchi et al. 2004). Females produce a litter once a year (Bini 1967, Tortonese 1956) and pups are between 8 and 14 cm TL at birth (12 to 14 cm (Compagno in prep.); 10–11 cm (Fischer et al. 1987); 11 cm (n=15) (Crozier unpub. data)). Smaller pups of 8–10 cm TL have been reported for the Adriatic (Marano et al. 2000).

This species feeds on small fishes, squids, and crustaceans (Compagno in prep.). The diet of E. spinax has been analysed as follows: crustaceans 74.8%, fishes 16.9%, cephalopods 6.9%, polychaetes 0.9% others 0.5% (Bello 1998, Cecchi et al. 2004). In the Rockall Trough in the Northeast Atlantic the diet of E. spinax was reported to consist mainly of benthopelagic organisms, with fish and crustaceans of secondary importance (Mauchline and Gordon 1983). Smaller specimens (<39 cm) of this species feed on mid-water fish that were completely absent from the stomachs of larger individuals. The differences in diet were thought to be partly due to prey selection and also because larger fish live at greater depths. In South Portugal a significant ontogenic variation in feeding ecology was observed, with specimens smaller than 17 cm TL feeding mainly on euphausiids, specimens from 17–27 cm TL feeding mainly on euphausiids and natant decapods and specimens larger than 27 cm TL feeding also on teleosts and cephalopods (Neiva et al. submitted). In Angolan waters, off the west African coast, the diet of this species has been described as follows: cephalopods (63%), crustaceans (33%) and teleosts (4%) (Zaera 2005).

Systems
  • Marine
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Environment

bathydemersal; marine; depth range ? - 2490 m (Ref. 55744), usually 200 - 500 m
  • Jones, E.G., A. Tselepides, P.M. Bagley, M.A. Collins and I.G. Priede 2003 Bathymetric distribution of some benthic and benthopelagic species attracted to baited cameras and traps in the deep eastern Mediterranean. Mar. Ecol. Prog. Ser. 251:75-80. (Ref. 55744)
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Depth range based on 793 specimens in 1 taxon.
Water temperature and chemistry ranges based on 141 samples.

Environmental ranges
  Depth range (m): -9 - 1790
  Temperature range (°C): 3.792 - 17.512
  Nitrate (umol/L): 3.330 - 20.705
  Salinity (PPS): 34.939 - 38.649
  Oxygen (ml/l): 3.797 - 6.246
  Phosphate (umol/l): 0.187 - 1.180
  Silicate (umol/l): 2.765 - 12.206

Graphical representation

Depth range (m): -9 - 1790

Temperature range (°C): 3.792 - 17.512

Nitrate (umol/L): 3.330 - 20.705

Salinity (PPS): 34.939 - 38.649

Oxygen (ml/l): 3.797 - 6.246

Phosphate (umol/l): 0.187 - 1.180

Silicate (umol/l): 2.765 - 12.206
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Depth: 70 - 2000m.
From 70 to 2000 meters.

Habitat: bathydemersal.
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Trophic Strategy

Demersal piscivore (Ref. 12223).
  • Greenstreet, S.P.R. 1996 Estimation of the daily consumption of food by fish in the North Sea in each quarter of the year. Scottish Fish. Res. Rep. No. 55. (Ref. 12223)
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Life History and Behavior

Life Cycle

Distinct pairing with embrace (Ref. 205).
  • Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
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Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 7 years (wild)
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Hormones regulate light emission: velvet belly lantern shark
 

A chromatophore iris of the lantern shark reveals bioluminenscence, being triggered by hormones.

     
  "Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark’s luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment." (Claes and Mallefet 2010:685)


"...work on the velvet belly lantern shark (Etmopterus spinax) demonstrated that, unlike any other known system, their luminescence is under hormonal control (Claes & Mallefet 2009a): prolactin and melatonin [hormones] trigger the light emission using specific extrinsic and intrinsic pathways while [alpha]-MSH [hormone] inhibited these light emissions." (Claes and Mallefet 2010:685)
  Learn more about this functional adaptation.
  • Claes JM; Mallefet J. 2010. The lantern shark’s light switch: turning shallow water crypsis into midwater camouflage. Biology letters. 6(5): 685-685.
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Functional adaptation

Light used for camouflage: velvet belly lantern shark
 

Light emitting organs on the underside of velvet belly lantern sharks help camouflage them via bioluminescent counterillumination.

         
  "Many midwater animals emit ventral light to hide their silhouette in the  water column. This phenomenon known as counterillumination typically  requires fine control over light emission since it needs a luminescence  that closely matches the properties of downwelling light (intensity,  angular distribution and wavelength). Here we provide evidence that,  although lacking complex structures of counterilluminating animals, the  deepwater luminescent shark Etmopterus spinax could, in Norwegian  fjords, efficiently cloak its silhouette from downwelling ambient light  to remain hidden from predator and prey. This represents the first  experimentally tested function of luminescence in a shark and  illustrates how evolution can take different routes to converge on  identical complex behavior." (Claes et al. 2010:28)

  Learn more about this functional adaptation.
  • Claes JM; Aksnes DL; Mallefet J. 2010. Phantom hunter of the fjords: Camouflage by counterillumination in a shark (Etmopterus spinax). Journal of Experimental Marine Biology and Ecology. 388(1-2): 28-32.
  • Viegas J. 2009. Sharks can become invisible. Discovery News [Internet],
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Etmopterus spinax

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Etmopterus spinax

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 7
Specimens with Barcodes: 36
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2009

Assessor/s
Coelho, R. Blasdale, T., Mancusi, C., Serena, F., Guallart, J., Ungaro, N., Litvinov, F., Crozier, P. & Stenberg, C.

Reviewer/s
Cavanagh, R.D., Valenti, S.V., Stevens, J.D. & Fowler, S.L. (Shark Red List Authority)

Contributor/s

Justification
A common lantern shark occurring in the Eastern Atlantic and Mediterranean Sea on outer continental shelves and upper slopes at depths of 70–2,000 m, and most abundant at 200–500 m. A non-commercial species, all specimens captured as bycatch by commercial fishing vessels are discarded thus limiting the data available. Data from the Mediterranean Sea, Eastern Central and South Atlantic indicate that the species is still relatively commonly caught in scientific trawl surveys and there is no evidence that the population has declined there. A recently introduced ban on bottom trawling below 1,000 m depth in the Mediterranean Sea will afford it protection there. Deepwater fisheries also operate off the coast of western Africa, but these are relatively limited at this time. However, deepwater fisheries are intense in the Northeast Atlantic and scientific trawl surveys indicate that catch rates of this species declined by approaching 20% between the 1970s and 1998–2004. This species shows size structure segregation with depth. The deeper-occurring larger mature female sharks are probably more affected by the commercial deepwater fisheries operating in the Northeast Atlantic than the immature stages that are found in shallower waters. An assessment of Near Threatened is warranted in the Northeast Atlantic, given the apparent decline and continued, intense deepwater fishing pressure. Elsewhere and globally, the species is assessed as Least Concern because there is no evidence for population decline throughout the rest of its range and there are areas of refuge from fishing pressure. Continued monitoring is required to ensure that this species is not detrimentally affected by expanding deepwater fisheries in the future, particularly in the Eastern Central and Southeast Atlantic.
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Population

Population
Mediterranean
Data collected from 1985–2002 by the Italian national GRUND project (Gruppo Nazionale Risorse Demersali) and from 1994–2002 by the MEDITS project (Mediterranean International Trawl Survey) (Relini 1998, Bertrand et al. 2000) provided information on the abundance and bathymetric distribution of Etmopterus spinax. Analysis of trends in Biomass Index (BI kg per km²) of E. spinax from 1985–2002 indicated stable populations in the northern Tyrrhenian Sea (Relini et al. 2000, Cecchi et al. 2004). Etmopterus spinax was present at both high frequency (19% of the hauls) and high abundance (between 1 and 10 kg per km²) in the Mediterranean, with a standing stock biomass of 4% (2,248 t). The species was found to have an especially high presence in the western-central part of the Mediterranean basin (Morocco, Spain, France, Tyrrhenian, Corsica, Sardinia and Sicily coasts) (Baino et al. 2001). Data collected in the Gulf of Valencia (Spain) during 1988–1989 from a bottom trawl fishery for Red Shrimp Aristeus antennatus revealed the presence of E. spinax in 87.5% of trawls carried out between 450 and 675 m depth, with a mean abundance of 1.04 specimens per hour trawl (Guallart 1990). All sizes were represented in the captures (from juveniles to adults of both sexes) and observations made in later years did not reveal any significant change in the abundance of E. spinax in this area (J. Guallart pers. comm. 2006).

Northeast Atlantic
Catch rates in Scottish surveys from 1998–2004 were 81% of those in Ministry of Agriculture, Fisheries and Food (MAFF) surveys in the 1970s (T. Blasdale pers. comm. 2006). These surveys cannot be directly compared as they used different gear and vessels and fished different depth ranges, but they do appear to indicate that population levels have declined slightly from pre-fishery levels (Jones et al. 2005).

In southern Portugal Catch Per Unit Effort (CPUE) data for captures with deepwater longlines set from 450–780 m depth are 1.71/1,000 hooks (s.d.= 1.83) (R. Coelho unpubl. data). Deep water trawlers in the Algarve capture this species from 200–700 m depth and CPUEs are highest at 500 m depth with a capture rate of 15.74 specimens per hour (Coelho et al. 2005b). CPUE (kg per hour fished) from French deepwater trawl vessels in ICES Division VIa (West of Scotland) showed discard rates of this species to peak at 18.3 kg/hr at 500 m and then decline to 1.3 kg/hr at 700 m (ICES WD, Crozier 2003).

Eastern Central and Southeast Atlantic
This species was common off the coast of Northwestern Africa in the 1980s and was still very common in more recent surveys (Gulyugin et al. 2006).

Population Trend
Unknown
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Threats

Major Threats
Mediterranean
This species is caught as a bycatch of bottom trawl fisheries and is known to be discarded by Italian (Abella and Serena 2002) and Spanish (Guallart 1990) fleets. Most specimens discarded are either dead or in very poor condition (J. Guallart pers. comm.). This species occurs at depths of 70–2,000 m, but mostly between 200–500 m in the Mediterranean. The main depth range of this species is within the range of Mediterranean fisheries. However, the ban on bottom trawling below depths of 1,000 m in the Mediterranean, adopted by all members of The General Fisheries Commission for the Mediterranean (GFCM), will afford protection in the deeper part of its bathymetric range. This measure came into force in September 2005.

Northeast Atlantic
Etmopterus spinax is most abundant in the northeast Atlantic between 400 and 800 m and large mature female E. spinax are found in waters around 600 m. This may suggest that these mature sharks are being affected more by the commercial deep-water fisheries than other life stages of E. spinax that are found in shallower waters. Therefore it is suggested that this species may also be susceptible to heavy commercial fishing in the northeast Atlantic (Coelho 2007).

It is caught as bycatch in bottomtrawls fishing for Nephrops norvegicus and Pandalus borealis in the Skagerrak and Kattegat by Swedish fishermen. It has never been recorded in logbooks and most is probably discarded at sea. Off the south coast of Portugal (Algarve), this species is captured in high quantities as bycatch of the deep water fisheries that operate at these depths, namely the bottom trawl fishery that targets Norway Lobster (Nephrops norvegicus), Red Shrimp (Aristeus antennatus) and Deepwater Pink Shrimp (Parapenaeus longirostris), and the near bottom longline fishery that targets European Hake (Merluccius merluccius), Conger Eels (Conger conger) and Wreck Fish (Polyprion americanus). In both fisheries, all captured specimens are discarded (Coelho et al. 2005a), and even though most are still alive when returned to sea, they usually have severe injuries (due to the long trawling periods or as a result of the hooks) that are likely to impair their survival.

Eastern Central and Southeast Atlantic
In general, very little is known of the threats that affect this species off the African coast. Off the Angolan coast, E. spinax is an uncommon species, captured rarely by bottom trawlers and always discarded. Where this species is common off Morocco (western Sahara), Mauritania, and Sierra Leone it is taken in trawls. However, catches are not recorded because of species identification problems and because this bycatch is discarded.
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Least Concern (LC)
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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Management

Conservation Actions

Conservation Actions
There are no species specific management measures. The General Fisheries Commission for the Mediterranean (GFCM) banned bottom trawling below depths of 1,000 m in the Mediterranean in February 2005 and this came into force in September 2005.

In Swedish waters (e.g., Skagerrak and Kattegat) bottom-trawls are required to have a selective grid that should help to reduce bycatch of E. spinax.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: minor commercial; price category: unknown; price reliability:
  • Coppola, S.R., W. Fischer, L. Garibaldi, N. Scialabba and K.E. Carpenter 1994 SPECIESDAB: Global species database for fishery purposes. User's manual. FAO Computerized Information Series (Fisheries). No. 9. Rome, FAO. 103 p. (Ref. 171)
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Wikipedia

Velvet belly lanternshark

The velvet belly lanternshark (or simply velvet belly, Etmopterus spinax) is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 70–2,490 m (230–8,170 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. These photophores are thought to function in counter-illumination, which camouflages the shark against predators. They may also play a role in social interactions.

Young velvet bellies feed mainly on krill and small bony fish, transitioning to squid and shrimp as they grow larger. There is evidence that individuals also move into deeper water as they age. This species exhibits a number of adaptations to living in the deep sea, such as specialized T-cells and liver proteins for dealing with the higher concentrations of heavy metals found there. Velvet bellies often carry a heavy parasite load. It is ovoviviparous, giving birth to litters of six to 20 young every two to three years. This species has virtually no commercial value, but large numbers are caught as bycatch in deepwater commercial fisheries. Although it has been assessed as of Least Concern by the International Union for Conservation of Nature, the heavy fishing pressure throughout its range and its slow reproductive rate are raising conservation concerns.

Taxonomy[edit]

Profile view of a velvet belly lanternshark, from Les Poissons (1877).

The velvet belly was originally described as Squalus spinax by Swedish natural historian Carl Linnaeus, known as the "father of taxonomy", in the 1758 tenth edition of Systema Naturae. He did not designate a type specimen; the specific epithet spinax is in reference to the spiny dorsal fins. This species was later moved to the genus Etmopterus via the synonymy of Constantine Samuel Rafinesque's Etmopterus aculeatus with Squalus spinax.[1]

The velvet belly is grouped with the Caribbean lanternshark (E. hillianus), fringefin lanternshark (E. schultzi), brown lanternshark (E. unicolor), broadbanded lanternshark (E. gracilispinis), combtooth lanternshark (E. decacuspidatus), and dwarf lanternshark (E. perryi) in having irregularly arranged, needle-shaped dermal denticles.[2] Its common name comes from this shark's black ventral surface, which is sharply delineated from the rest of its body like a patch of velvet.[3]

Distribution and habitat[edit]

The range of the velvet belly is in the eastern Atlantic, extending from Iceland and Norway to Gabon, including the Mediterranean Sea, the Azores, the Canary Islands, and Cape Verde. It has also been reported off Cape Province, South Africa. This shark mainly inhabits the outer continental and insular shelves and upper slopes over mud or clay, from close to the bottom to the middle of the water column.[1][4] It is most common at a depth of 200–500 m (660–1,640 ft), though in the Rockall Trough, it is only found at a depth of 500–750 m (1,640–2,460 ft).[5][6] This species has been reported from as shallow as 70 m (230 ft), and as deep as 2,490 m (8,170 ft).[7]

Description[edit]

The black underside of the velvet belly lanternshark gives it its common name.

The velvet belly is a robustly built shark with a moderately long, broad, flattened snout. The mouth has thin, smooth lips. The upper teeth are small, with a narrow central cusp and usually fewer than three pairs of lateral cusplets. The lower teeth are much larger, with a strongly slanted, blade-like cusp at the top and interlocking bases. The five pairs of gill slits are tiny, comparable in size to the spiracles. Both dorsal fins bear stout, grooved spines at the front, with the second much longer than the first and curved. The first dorsal fin originates behind the short and rounded pectoral fins; the second dorsal fin is twice the size of the first and originates behind the pelvic fins. The anal fin is absent. The tail is slender, leading to a long caudal fin with a small lower lobe and a low upper lobe with a prominent ventral notch near the tip.[1]

The dermal denticles are thin with hooked tips, arranged without a regular pattern well-separated from one another. The coloration is brown above, abruptly transitioning to black below. There are thin black marks above and behind the pelvic fins, and along the caudal fin.[1] The velvet belly possesses numerous photophores that emit a blue-green light visible from 3–4 m (9.8–13.1 ft) away.[3] Varying densities of photophores are arranged in nine patches on the shark's sides and belly, creating a pattern unique to this species: photophores are present along the lateral line, scattered beneath the head but excluding the mouth, evenly on the belly, and concentrated around the pectoral fins and beneath the caudal peduncle.[5][8] The maximum reported length is 60 cm (24 in), although few are longer than 45 cm (18 in).[5] Females are larger than males.[9]

Biology and ecology[edit]

Velvet belly lanternshark preserved in formalin.

Along with the blackmouth catshark (Galeus melastomus) and the Portuguese dogfish (Centroscymnus coelolepis), the velvet belly is one of the most abundant deep-sea sharks in the northeastern Atlantic.[10] It is found individually or in small shoals.[11] Samplings in the Mediterranean have found females outnumbering males across all ages; this imbalance increases in the older age classes.[12] In the Rockall Trough and the Catalan Sea, large adults are found in deeper waters than juveniles, which may serve to reduce competition between the two groups.[10] However, this pattern has not been observed at other sites in the eastern Mediterranean.[7]

The velvet belly's liver accounts for 17% of its body mass, three-quarters of which is oil, making it nearly neutrally buoyant.[13] To deal with the higher concentrations of heavy metals in the deep sea, the velvet belly has T-cells in its bloodstream that can identify and mark toxic compounds for elimination. These T-cells are produced by a lymphomyeloid gland in its esophagus called a "Leydig's organ", which is also found in some other sharks and rays. In its liver, specialized proteins are also capable of detoxifying cadmium, copper, mercury, zinc, and other toxic contaminants.[5] The velvet belly's bioluminescence is thought to function in counter-illumination, which eliminates the shark's silhouette and camouflages it from upward-looking predators.[8] Its bioluminescence may also serve a social function, such as finding mates or co-ordinating groups, as the pattern is species-specific. The velvet belly is an important food of larger fishes such as other sharks; a major predator of this species is the longnosed skate (Dipturus oxyrinchus).[5][11]

Velvet bellies are often heavily parasitized; this shark has an Anelasma squalicola barnacle attached near the fin spine.

Numerous parasites are known for this species, and both juveniles and adults often carry heavy parasite loads. Known internal parasites include the monogenean Squalonchocotyle spinacis, the tapeworms Aporhynchus norvegicus, Lacistorhynchus tenuis, and Phyllobothrium squali, and the nematodes Anisakis simplex and Hysterothylacium aduncum. Some of these parasites use the velvet belly's prey as intermediate hosts and are acquired via ingestion, while others use the shark itself as an intermediate host.[11] The barnacle Anelasma squalicola, an external parasite, attaches to the shark's dorsal spine socket and penetrates deeply into the muscle, in the process often providing an attachment site for a second (and rarely a third) barnacle. Infestation by this barnacle reduces its host's fecundity by impairing the development of the reproductive organs.[9]

Feeding[edit]

As generalist predators, velvet bellies feed on crustaceans (e.g. pasiphaeid shrimp and krill), cephalopods (e.g. ommastrephid squid and sepiolids), and bony fishes (e.g. shads, barracudinas, lanternfishes, and pouts).[5] Sharks off Italy also eat small amounts of nematodes, polychaete worms, and other cartilaginous fishes.[14] Studies of velvet bellies off Norway and Portugal, and in the Rockall Trough, have found small sharks under 27 cm (11 in) long feed mainly on the krill Meganyctiphanes norvegica and the small fish Maurolicus muelleri. As the sharks grow larger, their diets become more varied, consisting mainly of squid and the shrimp Pasiphaea tarda, as well fishes other than M. muelleri.[6][11][15] It has been speculated that smaller velvet bellies may be too slow to catch fast-moving cephalopods.[11] The cephalopod diet of adults overlaps with that of the Portuguese dogfish; the latter species may avoid competition with the velvet belly by living in deeper water.[10] The bite force exerted by the velvet belly is only around 1 N.[16]

Life history[edit]

The velvet belly is ovoviviparous, with the embryos hatching inside the uterus and being sustained by a yolk sac. The reproductive cycle may be two to three years long, with ovulation occurring in early autumn, fertilization in the summer (or possibly in the winter if females are capable of storing sperm), and parturition in late winter or early spring. The gestation period is under one year.[9][17] The litter size is six to 20, with the number of young increasing with female size. At birth, the young measure 12–14 cm (4.7–5.5 in) long.[1][17] The shark's bioluminescence develops before birth; the yolk sac is fluorescent before any photophores have formed, suggesting the mother transfers luminescent materials to her offspring. The first luminous tissue appears when the embryo is 55 mm (2.2 in) long, and the complete pattern is laid down by the time it is 95 mm (3.7 in) long. At birth, the young shark is already capable of counter-illumination with 80% of its ventral surface luminescent.[8]

The growth rate of the velvet belly is slow, though faster than some other deep-sea sharks, such as the leafscale gulper shark (Centrophorus squamosus) or the shortspine spurdog (Squalus mitsukurii). Males mature sexually at 28–33 cm (11–13 in) long and females at 34–36 cm (13–14 in) long.[5][12] The average age at maturity is 4.0 years for males and 4.7 years for females, though four-year-old mature individuals of both sexes have been caught in the wild, along with immature females over eight years old.[17] Males and females eight and 11 years old, respectively, have been caught in the wild; the potential lifespan of this species has been estimated at 18 years for males and 22 years for females.[12][17]

Human interactions[edit]

Throughout their range, substantial quantities of velvet bellies are caught as bycatch in bottom trawls meant for shrimp and lobsters, and deepwater longlines meant for other fish. Lacking commercial value, these sharks are almost always discarded with extremely high mortality, though occasionally they are dried and salted or made into fishmeal.[1][12] The IUCN has listed the velvet belly under Least Concern overall, as its population remains stable across much of its range, and it is afforded some protection in the Mediterranean from a 2005 ban on bottom trawling below 1,000 m (3,300 ft). However, in the northeastern Atlantic it has been assessed as Near Threatened, as its numbers have declined by almost 20% from 1970 to 1998–2004.[18] The slow reproductive rate of this species limits its capacity to recover from population depletion.[17]

References[edit]

  1. ^ a b c d e f Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. p. 85. ISBN 92-5-101384-5. 
  2. ^ Springer, S. and G.H. Burgess (August 5, 1985). "Two New Dwarf Dogsharks (Etmopterus, Squalidae), Found off the Caribbean Coast of Colombia". Copeia (American Society of Ichthyologists and Herpetologists) 1985 (3): 584–591. doi:10.2307/1444748. JSTOR 1444748. 
  3. ^ a b Ellis, R. (1996). Deep Atlantic: Life, Death, and Exploration in the Abyss. The Lyons Press. pp. 195–196. ISBN 1-55821-663-4. 
  4. ^ Sion, L., Bozzano, A., D’Onghia, G., Capezzuto, F. and Panza, M. (2004). "Chondrichthyes species in deep waters of the Mediterranean Sea". Scientia Marina 68 (S3): 153–162. doi:10.3989/scimar.2004.68s3153. 
  5. ^ a b c d e f g Martin, R.A. Deep Sea: Velvetbelly Lanternshark. ReefQuest Centre for Shark Research. Retrieved on June 24, 2009.
  6. ^ a b Mauchline, J. and Gordon, J.D.M. (1983). "Diets of the sharks and chimaeroids of the Rockall Trough, northeastern Atlantic Ocean". Marine Biology 75 (2-3): 269–278. doi:10.1007/BF00406012. 
  7. ^ a b Jones, E.G., Tselepides, E., Bagley, P.M., Collins, M.A. and Priede, I.G. (2003). "Bathymetric distribution of some benthic and benthopelagic species attracted to baited cameras and traps in the deep eastern Mediterranean". Marine Ecology Progress Series 251: 75–86. doi:10.3354/meps251075. 
  8. ^ a b c Claes, J.M. and Mallefet, J. (2008). "Early development of bioluminescence suggests camouflage by counter-illumination in the velvet belly lantern shark Etmopterus spinax (Squaloidea: Etmopteridae)". Journal of Fish Biology 73 (6): 1337–1350. doi:10.1111/j.1095-8649.2008.02006.x. 
  9. ^ a b c Hickling, C.F. (1963). "On the small deep-sea shark Etmopterus spinax L., and its cirripede parasite Anelasma squalicola (Lovén)". Journal of the Linnean Society of London, Zoology 45 (303): 17–24. doi:10.1111/j.1096-3642.1963.tb00484.x. 
  10. ^ a b c Carrassón, M., Stefanescu, C. and Cartes, J.E. (1992). "Diets and bathymetric distributions of two bathyal sharks of the Catalan deep sea (western Mediterranean)". Marine Ecology Progress Series 82 (1): 21–30. doi:10.3354/meps082021. 
  11. ^ a b c d e Klimpel, S., Palm, H.W. and Seehagen, A. (2003). "Metazoan parasites and food composition of juvenile Etmopterus spinax (L., 1758) (Dalatiidae, Squaliformes) from the Norwegian Deep". Parasitology Research 89 (4): 245–251. doi:10.1007/s00436-002-0741-1. PMID 12632160. 
  12. ^ a b c d Gennari, E. and Scacco, U. (2007). "First age and growth estimates in the deep water shark, Etmopterus Spinax (Linnaeus, 1758), by deep coned vertebral analysis". Marine Biology 152 (5): 1207–1214. doi:10.1007/s00227-007-0769-y. 
  13. ^ Schmidt-Nielsen, S., Flood, A. and Stene, J. (1934). "On the size of the liver of some gristly fishes, their content of fat and vitamin A". Kongeleige Norske Videnskabers Selskab Forhandlinger 7: 47–50. 
  14. ^ Serena, F., Cecchi, E., Mancusi, C. and Pajetta, R. (2006). "Contribution to the knowledge of the biology of Etmopterus spinax (Linnaeus 1758) (Chondrichthyes, Etmopteridae)". In FAO. Deep Sea 2003: Conference on the Governance and Management of Deep-sea Fisheries. Food and Agricultural Organization. pp. 388–394. ISBN 92-5-105457-6. 
  15. ^ Neiva, J., Coelho, R. and Erzini, K. (2006). "Feeding habits of the velvet belly lanternshark Etmopterus spinax (Chondrichthyes: Etmopteridae) off the Algarve, southern Portugal". Journal of the Marine Biological Association of the United Kingdom 86 (4): 835–841. doi:10.1017/S0025315406013762. 
  16. ^ Huber, D.R., Claes, J.M., Mallefet, J. and Herrel, A. (2009). "Is Extreme Bite Performance Associated with Extreme Morphologies in Sharks?". Physiological and Biochemical Zoology 82 (1): 20–28. doi:10.1086/588177. PMID 19006469. 
  17. ^ a b c d e Coelho, R. and Erzini, K. (2008). "Life history of a wide-ranging deepwater lantern shark in the north-east Atlantic, Etmopterus spinax (Chondrichthyes: Etmopteridae), with implications for conservation". Journal of Fish Biology 73 (6): 1419–1443. doi:10.1111/j.1095-8649.2008.02021.x. 
  18. ^ Coelho, R., T. Blasdale, C. Mancusi, F. Serena, J. Guallart, N. Ungaro, F. Litvinov, P. Crozier and C. Stenberg (2008). "Etmopterus spinax". IUCN Red List of Threatened Species. Version 2010.1. International Union for Conservation of Nature. Retrieved April 25, 2010. 
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