Raja brachyura Lafont, 1873

Gordon, Cat A., Hood, Ali R. & Ellis, Jim R., 2016, Descriptions and revised key to the eggcases of the skates (Rajiformes: Rajidae) and catsharks (Carcharhiniformes: Scyliorhinidae) of the British Isles, Zootaxa 4150 (3), pp. 255-280 : 263-265

Raja brachyura Lafont, 1873

Distribution. Blonde ray ( R. brachyura ) occurs from the northern British Isles to southern Portugal, including parts of the Mediterranean Sea ( Stehmann & Bürkel, 1984; Serena et al., 2010). It has a patchy distribution but is relatively common in the inner shelf seas of the Irish Sea, St George’s Channel, Bristol Channel, English Channel and parts of the southern North Sea, with juveniles often reported from inshore waters ( Ellis et al., 2005). Verified R. brachyura eggcases recorded to the Great Eggcase Hunt were mostly from the southern and southwestern coasts of England as well as the Channel Islands, although reports were submitted from around the rest of the British coastline.

Material examined. Fifty-three eggcases were examined in total. Most specimens sampled (n = 43) were collected from beaches in southwestern England by the Great Eggcase Hunt. Other specimens were from trawl surveys (n = 6), public aquaria (n = 2) and museum collections (n = 2). Of the latter, one specimen was from western Ireland ( BMNH 94.3.29.31 as Raja ) and the other had no geographic information.

Description. The eggcase of R. brachyura ( Figure 5 a) is large, with an average eggcase length of 108.6 ± 10.1 mm (82.0–132.0 mm) and eggcase width of 32.7–86.4 mm. If the horns are intact, then total eggcase length can range from 119.5–255.0 mm. Both sides of the capsule are convex, however the dorsal side predominantly so, with both sides displaying distinct longitudinal striations. Well-defined keels extend from the narrowest point of the eggcase at the base of the anterior apron, to the point where the posterior horns join the capsule. Both the anterior and posterior aprons are distinctive and well-developed, with the anterior apron straight (but often frayed) and the posterior apron concave. Recently deposited eggcases are covered with thin fibres, which can often still be visible in strandline specimens (particularly on the aprons, where the fibres tend to be paler in colour). The anterior and posterior horns are thick, with the anterior horns longer than the posterior horns (when intact).

Remarks. R. brachyura is one of the largest commonly-occurring eggcases found around the British Isles. The two historic samples examined (BMNH 94.3.29.31 and BMNH 2013.12.7.1; the latter re-catalogued) were 105.0– 132.2 mm long without horns, with a greatest width of 68.0–74.0 mm; these were both at the upper end of the size range observed in contemporary samples. Spent specimens found on the beach are often badly damaged with broken horns, which can hamper identification to species. If damaged and dehydrated, specimens may be confused with R. clavata , although the eggcase of R. brachyura is larger. The eggcase lengths and widths recorded in the present study extended the known size range for this species.

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Species Eggcase wiđth Eggcase length Comments anđ source 62 80 Lacourt (1979; Fig. 1 ) 50 70 Bor (1998; Fig. 13) 52 (50*54) 75 (70*78) 128 (121*135) Capapé (1976; n=82) 48.0 ± 5.0 65.0 ± 5.0 Maia et al. (2015; n=57) 37.0 ± 8.2 35.1 ± 2.6 67.2 ± 10.0 122.0 ± 12.1 This stuđy

(32.7*69.0; n=52) (32.2*45.0; n=52) (32.7*83.3; n=52) (99.3*153.0; n=52)

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Figures

FIGURE 1. Generalised eggcase morphology for catsharks (Scyliorhinidae) and skates (Rajidae) indicating measurements recorded

FIGURE 5. Eggcases of (a) Raja brachyura (b) Raja clavata (typical specimen) and (c) R. clavata (aberrant specimen from museum collection; BMNH 1927.3.25.1).