Overview

Comprehensive Description

[[ Genus Squatina Dumeril ZBK ]]

Squatina Dumeril, 1806 ZBK is a monotypic genus within the family Squatinidae (Bonaparte, 1838). Although morphologically similar to batoids, squatinids are distinct from true batoids in that the squatinids have lateral gill openings, pectoral fin lobes that are free lateral to the gills, and possess a lower caudal fin lobe that is longer than the upper caudal lobe. Within the genus these sharks can be difficult to distinguish due to the lack of well defined characteristics. Adding to the confusion in the literature are the inadequate original descriptions of many species.

Sixteen valid species are recognized worldwide, with four reported to occur in the western North Pacific (WNP; Compagno et al., 2005). These four species include Squatina formosa Shen and Ting, 1972 ZBK , S. japonica Bleeker, 1858 ZBK , S. nebulosa Regan, 1906 ZBK , and S. tergocellatoides Chen, 1963 ZBK . Distinctions among these four WNP species hinge upon the nasal barbel shape, interorbital and interspiracle distances, ocellus patterns, number of dermal folds about the mouth, and the presence of midback thorns (Lindberg & Legeza, 1967; Shen & Ting, 1972; Nakabo, 2002). However, specific identification is hard to assign to individuals because many of these characters are difficult to distinguish, and many characters currently used are susceptible to damage during collection or from preservation. Additionally, inadequate original descriptions for some species and confusion within the subsequent literature have further obscured definitive characters among the WNP species. Because members of this genus are frequently targeted in fisheries in an area that has sparsely recorded catch information, and congeners are particularly sensitive to fishing pressure (Gaida, 1997; Stevens et al, 2000), it is imperative that adequate descriptions are available to identify individual species.

During two field expeditions to Taiwan, one of us (DAE) observed at least four species of Squatina ZBK that were frequently landed at fish markets around Taiwan. Attempts to identify the various species were often hampered by a lack of adequate fish keys and descriptive characters for the various Squatina ZBK species observed. Furthermore, we had the opportunity to examine the holotype and three paratypes of S. formosa ZBK as well as collect additional material.

Using this information, we provide a detailed redescription of three of the species, S. formosa ZBK , S. japonica ZBK , and S. nebulosa ZBK , with new material from Japanese and Taiwanese waters. In addition, we supply a list of important key characters for distinguishing all known WNP squatinids, especially to facilitate identification of the two most similar species, S. formosa ZBK and S. nebulosa ZBK .

  • Jonathan H. Walsh, David A. Ebert (2007): A review of the systematics of western North Pacific angel sharks, genus Squatina, with redescriptions of Squatina formosa, S. japonica, and S. nebulosa (Chondrichthyes: Squatiniformes, Squatinidae). Zootaxa 1551, 31-47: 31-32, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:DD00E8E3-2C28-41A8-A401-E0D00DA325B9
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Genus Squatina Dumeril , 1806 ZBK

Squatina Dumeril , 1806 ZBK : 102, 342. Type Squalus squatina Linneaus 1758 ZBK , by subsequent designation.

Rhina Rafinesque 1810 ZBK : 4. Type Squalus squatina Linneaus 1758 ZBK , type by monotypy.

Definition. Broad, flattened body with large bat-like pectoral fins. Mouth terminal, broadly arched with ornate nasal flaps and highly protrusible jaws. Spiracles large, without valves. Pectoral fins not fused to head, origin opposite gill openings. Anterior extent of pectorals triangular and covering gill openings. Five pairs of gill openings positioned between pectoral origin and base of the head. Trunk compressed dorsal-ventrally. Two dorsal fins, spineless, originating behind pelvic fin insertion on the precaudal. Anal fin absent. Furrow on ventral from dorsal origin to caudal peduncle. Caudal fin hypocercal. Total length, depending on species, generally between 1-2 m.

  • Jonathan H. Walsh, David A. Ebert (2007): A review of the systematics of western North Pacific angel sharks, genus Squatina, with redescriptions of Squatina formosa, S. japonica, and S. nebulosa (Chondrichthyes: Squatiniformes, Squatinidae). Zootaxa 1551, 31-47: 35-35, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:DD00E8E3-2C28-41A8-A401-E0D00DA325B9
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[[ Genus Squatina Dumeril ZBK ]]

The main confusion among WNP squatinids lies in differentiating S. formosa ZBK and S. nebulosa ZBK from one another. The main character used in the past to differentiate these two species was the number of dermal lobes at the corners of the mouth (Chen 1963, Nakabo 2002, Compagno 2005a). Based upon our examination, this character does not appear to be robust in separating these species. Although all S. formosa ZBK individuals studied had one dermal lobe, S. nebulosa ZBK specimens had one or two lobes, invalidating this character as a method of separating the two species. Additionally, the number of dermal lobes was often difficult to determine since differentiation between lobes is often vague and these lobes are susceptible to damage during capture and or preservation of specimens. A combination of characters should be used to identify individuals of these two species, since the differences are subtle and a great deal of overlap exists among many characters. The best characters available, based on our findings, appear to be the shape of the caudal pelvic and dorsal fins, the ratio of standardized pelvic girdle distance with the standardized head length, and the shape and height of the upper lip arch. The upper lip arch appears to be of particular value as a field character. It is a feature that is not prone to damage and is easy to assess quickly in the field. More specimens are needed to assess the utility of this character but it appears to be useful for all WNP squatinids.

Based on the key characters presented herein, we provide the following key to the WNP squatinids:

Key to Western North Pacific Squatina ZBK Species

1. Pelvic fin tips do not extend to origin of first dorsal fin..............................................................................2.

- Pelvic fin tips extend to or surpass origin of first dorsal fin........................................................................3.

2. A prominent row of thorn-like denticles extending from mid-back to caudal peduncle; no distinct ocelli on posterior lobes of the pectoral fins................................................................................................ S. japonica ZBK

- No row of thorn-like denticles extending from the mid-back to the caudal peduncle, distinct paired ocelli on the posterior lobes of the pectoral fins......................................................................... S. tergocellatoides ZBK

3. Upper lip arch semi-circular in shape (>1.5% TL in height); dorsals are lobed with a curvilinear anterior margin; pelvic girdle distance 1.4 times or less head length; caudal fin is lobed, especially dorsally, with a curvilinear postventral caudal margin........................................................................................... S. formosa ZBK

- Upper lip arch is not semi-circular in shape (<1.5% TL in height); dorsals are not lobed (angular) without a curvilinear anterior margin (straight); pelvic girdle distance greater than 1.4 times head length; caudal fin is not lobed (angular), especially dorsally, without a curvilinear postventral caudal margin (straight) ... ..................................................................................................................................................... S. nebulosa ZBK

  • Jonathan H. Walsh, David A. Ebert (2007): A review of the systematics of western North Pacific angel sharks, genus Squatina, with redescriptions of Squatina formosa, S. japonica, and S. nebulosa (Chondrichthyes: Squatiniformes, Squatinidae). Zootaxa 1551, 31-47: 46-46, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:DD00E8E3-2C28-41A8-A401-E0D00DA325B9
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Physical Description

Diagnostic Description

Squatina Duméril , 1806 : 102, 342. Type Squalus squatina Linneaus 1758 , by subsequent designation.

 

Rhina Rafinesque 1810 : 4. Type Squalus squatina Linneaus 1758 , type by monotypy.

 

Definition. Broad, flattened body with large bat-like pectoral fins. Mouth terminal, broadly arched with ornate nasal flaps and highly protrusible jaws. Spiracles large, without valves. Pectoral fins not fused to head, origin opposite gill openings. Anterior extent of pectorals triangular and covering gill openings. Five pairs of gill openings positioned between pectoral origin and base of the head. Trunk compressed dorsal-ventrally. Two dorsal fins, spineless, originating behind pelvic fin insertion on the precaudal. Anal fin absent. Furrow on ventral from dorsal origin to caudal peduncle. Caudal fin hypocercal. Total length, depending on species, generally between 1-2 m.

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Jonathan H. Walsh

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Ecology

Habitat

Depth range based on 1089 specimens in 17 taxa.
Water temperature and chemistry ranges based on 739 samples.

Environmental ranges
  Depth range (m): 0 - 1289
  Temperature range (°C): 3.798 - 26.833
  Nitrate (umol/L): 0.150 - 26.018
  Salinity (PPS): 28.899 - 36.472
  Oxygen (ml/l): 1.055 - 6.593
  Phosphate (umol/l): 0.120 - 2.035
  Silicate (umol/l): 1.009 - 38.833

Graphical representation

Depth range (m): 0 - 1289

Temperature range (°C): 3.798 - 26.833

Nitrate (umol/L): 0.150 - 26.018

Salinity (PPS): 28.899 - 36.472

Oxygen (ml/l): 1.055 - 6.593

Phosphate (umol/l): 0.120 - 2.035

Silicate (umol/l): 1.009 - 38.833
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
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Depth range based on 1089 specimens in 17 taxa.
Water temperature and chemistry ranges based on 739 samples.

Environmental ranges
  Depth range (m): 0 - 1289
  Temperature range (°C): 3.798 - 26.833
  Nitrate (umol/L): 0.150 - 26.018
  Salinity (PPS): 28.899 - 36.472
  Oxygen (ml/l): 1.055 - 6.593
  Phosphate (umol/l): 0.120 - 2.035
  Silicate (umol/l): 1.009 - 38.833

Graphical representation

Depth range (m): 0 - 1289

Temperature range (°C): 3.798 - 26.833

Nitrate (umol/L): 0.150 - 26.018

Salinity (PPS): 28.899 - 36.472

Oxygen (ml/l): 1.055 - 6.593

Phosphate (umol/l): 0.120 - 2.035

Silicate (umol/l): 1.009 - 38.833
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:298
Specimens with Sequences:243
Specimens with Barcodes:196
Species:21
Species With Barcodes:19
Public Records:158
Public Species:19
Public BINs:15
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Barcode data

Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

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Wikipedia

Angel shark

This article is about the genus. For the species, see angelshark.
Squatina squatina, usually known simply as the angelshark, is the type species for all angelsharks
Ornate angelshark, S. tergocellata
Australian angelshark, S. australis

Angel sharks are sharks in the genus Squatina, which are unusual in having flattened bodies and broad pectoral fins that give them a strong resemblance to rays. Twenty-three species are known to exist in the genus, which is the only one in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate and tropical seas. Most species inhabit shallow temperate or tropical seas, but one species inhabits deeper water, down to 1,300 m (4,300 ft).[2] Angel sharks are sometimes called monkfish, although this name is also applied to members of the genus Lophius.

Appearance and biology[edit]

While the forward part of the angel shark's body is broad and flattened, the rear part retains a muscular appearance more typical of other sharks. The eyes and spiracles are on top, and the five gill slits are on its back. Both the pectorals and the pelvic fins are large and held horizontally. There are two dorsal fins, no anal fin, and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe. Most types grow to a length of 1.5 m (5 ft), with the Japanese angel shark, Squatina japonica, known to reach 2 m.[3] Angel sharks possess extensible jaws that can rapidly snap upwards to capture prey, and have long, needle-like teeth. They bury themselves in sand or mud lying in wait for prey, which includes fish, crustaceans, and various types of mollusks.[2] They are ovoviviparous, producing litters of up to 13 pups.

Behavior[edit]

Although this shark is a bottom-dweller and appears harmless, it can inflict painful lacerations if provoked, due to its powerful jaws and sharp teeth. It may bite if a diver approaches the head or grabs the tail.[4]

Commercial value[edit]

Prior to the late 1970s, the Pacific angel shark was considered a "junk fish".[5] It was a byproduct of commercial gillnetting, with no commercial appeal and was used only for crab bait. In 1977, Michael Wagner, a fish processor in Santa Barbara, California, in cooperation with local commercial fisherman, developed the market for angel sharks.[5] The annual take of angel shark in 1977 was an estimated 147 kg.[5] By 1985, the annual take of angel shark on the central California coast had increased to more than 454 metric tons or an estimated 90,000 sharks.[5] The population declined dramatically and is now regulated.

In April 2008, the UK government afforded the angel shark full protection under the Wildlife and Countryside Act. Once considered abundant in the Atlantic Ocean, the angel was classified as "critically endangered" in 2010.[6]

Species[edit]

See also[edit]

References[edit]

  1. ^ Bourdon, J. (2009). Genera from the Fossil Record: Squatina. The Life and Times of Long Dead Sharks. Retrieved on July 8, 2009.
  2. ^ a b Stevens, J. & Last, P.R. (1998). Paxton, J.R. & Eschmeyer, W.N., ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 64–65. ISBN 0-12-547665-5. 
  3. ^ Froese, Rainer, and Daniel Pauly, eds. (2009). "Squatinidae" in FishBase. January 2009 version.
  4. ^ Best, Cathleen. "Florida Museum of Natural History." Pacific Angel Shark. (Date accessed 06/23/2010) <http://www.flmnh.ufl.edu/fish/gallery/descript/pacificangelshark/pacificangelshark.html>.
  5. ^ a b c d Richards, John B. "Developing a localized fishery: the Pacific angel shark." Sharks: an inquiry into biology, behavior, fisheries, and use. S. Cook (ed.). EM 8330 (1987): 147-160.
  6. ^ Fowler, Susan (2010). "Background Document for Angel shark Squatina squatina". German Federal Agency for Nature Conservation. The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR). Retrieved 24 October 2013. 

External links[edit]

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