AN ABNORMAL THORNBACK RAY RAJA CLAVATA WITH ADDITIONAL PECTORAL FINS

AN ABNORMAL THORNBACK RAY RAJA CLAVATA

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AN ABNORMAL THORNBACK RAY RAJA CLAVATA WITH ADDITIONAL PECTORAL FINS J. R. ELLIS An abnormal thornback ray Raja clavata Linnaeus, 1758 was caught by long line on 9 March 2005 near the Shipwash Bank (south-east of Orford, at approximately 52º 01’N, 01º 39’E). The specimen was an immature male of 54 cm total length (36·5 cm disc width and 27 cm disc length), and weighed approximately 850 g. Two additional fins were present on the dorsal surface, each originating from the mid-line and lying on the right hand side of the fish (Figure 1a). The anterior additional fin was relatively large, and the more posterior additional fin smaller.

The distance between the tip of the snout and the origin of the base of the anterior additional fin was 12 cm, and the origin of the base was 27 mm behind the spiracles. The maximum length and width of the anterior additional

Figure 1a

Figure 1b

Figure 1: Abnormal thornback ray Raja clavata showing (a) the dorsal surface with the anterior additional fin (A1), posterior additional fin (A2), and (b) xray of the specimen showing the upper jaw or palatoquadrate (Pal), lower jaw or Meckel’s cartilage (Mec), pectoral radials (p.r.), branchial arches (Bra), pectoral girdle (Pec), vertebral column (Ver), proterygium (Pro), mesopterygium (Mes) and metapterygium (Met), and with the approximate position of the additional fins marked.

Trans. Suffolk Nat. Soc. 41 (2005)

Species

Three additional fins (6, 9 and Dipturus batis 13 cm in length) on dorsal surface, slightly to the right of the mid-line Additional pectoral fin (9 cm Dipturus batis long) on mid-line, lying to the right Additional pair of fins Leucoraja circularis associated with the branchial arches and pectoral girdle on the ventral surface Additional pair of fins Leucoraja circularis associated with the branchial arches on the ventral surface Additional fin on the dorsal Leucoraja naevus surface, lying to the right An additional fin (11 cm high) Raja clavata on the left wing, close to the scapula Additional fin associated with Raja clavata the scapula and lying on the right hand side of the dorsal surface

Deformity

-

M

Trans. Suffolk Nat. Soc. 41 (2005) 46 cm

-

-

75 cm

91 cm

-

-

F

-

M

47路5 cm M

-

-

-

Width Sex

84 cm

Length

-

1845

-

-

-

-

-

Date

Harper (1933)

Rennie (1906)

Rennie (1906)

Reference

Celtic Sea

Normandy

Celtic Sea

Du Buit (1978)

Deslongchamps (1853)

Du Buit (1978)

NE Shetland Du Buit (1978) Isles

North Sea

Aberdeen

Aberdeen

Location

Table 1: Details of skates (Rajidae) recorded in North-west European seas with additional fins present

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Additional fin arising from the midline on the dorsal surface, associated with the scapula, and lying to the right Additional fin (7·5 cm high) lying to the right of the midline Additional fin on the dorsal midline posterior to the head and lying to the left Additional fin (2·2 cm high) on the dorsal surface lying to the left Additional fins lying to the right of the mid-line on the dorsal surface Small (5–6 cm) additional pectoral fin projecting from the right side of the pectoral girdle on the ventral surface

Deformity

Table 1. Continued

F

F

42 cm

-

16·5 cm 11·1 cm 54 cm

-

Raja clavata

Raja clavata

Raja clavata

Raja montagui

Anglesey

Co Kerry

-

Location

Apr 1994 Swansea

-

-

-

Date

24 cm

-

Jan 1917 Great Orme

36·5 cm M Mar 2005 Southern North Sea

-

35 cm

49 cm

Raja clavata

-

-

Width Sex

-

Length

Raja clavata

Species

Johnstone (1920)

This study

Ellis (unpublished)

Grove and Roberts (1982)

Hillis (1966)

Schnakenbeck (1942)

Reference

AN ABNORMAL THORNBACK RAY RAJA CLAVATA

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Trans. Suffolk Nat. Soc. 41 (2005)

Length

Width

Trans. Suffolk Nat. Soc. 41 (2005) Nov 1958 Sep 1909 Nov 1886 Apr 1934 1943 Sep 1905 Feb 1930 Aug 1963 Jan 1928 Mar 1975

F M

Date

M M F M M F F M M -

Sex

* Either L. naevus or L. fullonica

Off Plymouth Gulf of Tunis

Newfoundland Aberdeen Concarneau La Rochelle Blackpool Off Plymouth Concarneau Concarneau

Location

Templeman (1965) Williamson (1911) Bureau (1889) Legendre (1935) Letaconnoux (1949) Johnstone (1906) Vaillant (1908) Williamson (1911) Williamson (1911) Ford (1930) Du Buit (1964) Du Buit (1978)

Reference

Ford (1930) Capapé and Pantoustier (1975) Pectoral fins not fused to head and fleshy lobes between anterior margins of pectoral fins and head Rostroraja alba 26 cm 18·5 cm Adriatic D’Ancona (1933)

Amblyraja radiata 63 cm Leucoraja spp.* Raja asterias Raja brachyura 12 cm 8 cm Raja brachyura 41·5 cm Raja clavata 11 cm Raja clavata 60 cm Raja clavata 47.5 cm Raja clavata 46 cm Raja clavata 51 cm Raja clavata 72·8 cm 51·4 cm Raja clavata Pectoral fins not fused to head (right side only) Raja microocellata 26 cm Raja radula 54 cm 37 cm

Pectoral fins not fused to head

Species

Table 2: Details of abnormal skates (Rajidae) with other deformities of the pectoral fins.

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AN ABNORMAL THORNBACK RAY RAJA CLAVATA

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fin were 91 mm and 60 mm respectively, and the base of this fin was 28 mm.

The posterior additional fin was approximately 10 mm behind the anterior fin.

The maximum length and width of the posterior additional fin were 39 mm and 25 mm respectively, and the base of this fin was 17 mm.

Both additional fins were pigmented on both sides, but paler towards the margins, and the skin was spinulose, although smoother nearer the margins.

The anterior additional fin had several associated thorns, including median thorns posterior and anterior to the base, a well-developed thorn on the innermost part of the fin, and three spines on the lower posterior margin. The smaller of the additional fins had a median thorn near the base.

Cartilaginous radial elements were present in both additional fins, and were well developed in the more anterior fin. The large size and structure of the anterior fin, including the presence of a well-developed thorn, suggest that this was an additional pectoral fin, and the x-ray of the specimen (Figure 1b) confirmed that this fin was associated with the pectoral girdle. The pectoral girdle on the specimen was not symmetrical, and the connection between the pectoral girdle and metapterygium on the right hand side of the fish was malformed.

There are occasional reports of additional fins in skates (Table 1), including common skate Dipturus batis (Linneus, 1758) (Rennie, 1906), sandy ray Leucoraja circularis (Couch, 1838) (Harper, 1933; Du Buit, 1978), cuckoo ray L. naevus (Müller & Henle, 1841) (Du Buit, 1978), spotted ray Raja montagui Fowler, 1910 (Johnstone, 1920) and R. clavata (Deslongchamps, 1853; Schnakenbeck, 1942; Hillis, 1966; Grove and Roberts, 1982).

Interestingly, in the majority of these reports, the additional fin lies on the right hand side of the fish.

Several other forms of abnormal development have been reported in skates and rays, though most of these reported abnormalities relate to specimens where the pectoral fins are not fully fused to the head, and these deformities have been reported in a range of batoids, including skates (summarised in Table 2), and sting and eagle rays (e.g. Chhapgar, 1964; Bennet, 1964; Easwaran, 1967). Other types of abnormality that have been observed in batoids include two-headed embryos (Lazarus, 1985), specimens with “extra snouts” (McIntosh, 1886), specimens where the rostral cartilage has not extended anteriorly, thus resulting in a blunt-snouted condition (Templeman, 1965), spinal deformities, particularly with regards the tail (Ford, 1930, Templeman, 1965; Du Buit, 1978), albinism and partial albinism (Wilson, 1951; Capapé and Pantoustier, 1975), abnormal dentition (Gudger, 1933), spinulose skin (Du Buit, 1978) and intersexuality and hermpahroditism (Quignard and Negla, 1971; Quignard and Capapé, 1972).

Though there are occasional reports of additional fins in skates, reports of additional fins in teleost fishes tend to be rare (Dawson, 1964, 1966, 1971; Venkateswarlu, 1972; Singh and Reddy, 1989; Raadik, 1993), though this is not surprising given that malformed larval stages are likely to have high mortality. In contrast, skates are oviparous and the embryo develops over a period of several months prior to hatching, with recently hatched fish relatively well developed. This may result in malformed skates having a greater chance of surviving after hatching.

Trans. Suffolk Nat. Soc. 41 (2005)

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Acknowledgements Thanks to Pete Draper (SFI, Lowestoft) for passing on information regarding the specimen, Bernard Seret (Muséum National d’Histoire Naturelle, Paris) for providing information from early references, and Wangford Veterinary Clinic for providing the X-ray.

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Jim Ellis CEFAS Lowestoft Laboratory Pakefield Road Lowestoft Suffolk NR33 0HT

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