Raja undulata Lacepede, 1802

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 : 269-270

Raja undulata Lacepede, 1802

Distribution. Undulate ray ( R. undulata ) has a patchy distribution in the Northeast Atlantic and Mediterranean Sea (Ellis et al., 2012), although it can be locally abundant in some areas, such as the English Channel. The majority of verified records submitted to the Great Eggcase Hunt were from the south coast of England (in particular the eastern English Channel) with some records from southwestern coasts.

Material examined. Fifty-two eggcases were examined in detail, most of which were collected by the Great Eggcase Hunt (n = 50), while the other specimens (n = 2) were from public aquaria. An additional aberrant specimen collected in January 2015 from Brighton (English Channel) was also supplied to the Great Eggcase Hunt for examination (see below).

Description. The eggcase of R. undulata ( Figure 7 b) is moderately large and elongated, with an eggcase length of 80.4 ± 4.4 mm (71.9–89.4 mm) and eggcase width of 34.5 ± 0.9 mm (32.7–36.7 mm). The eggcase is biconvex with longitudinal striations on the ventral surface. The dorsal surface is often covered with a thin fibrous layer, although striations are present underneath. The eggcase is without keels, although the capsule margin has a rough edge, often with additional detritus laden fibres attached (presumably as a remnant of the mucus ‘mat’ that is associated with newly laid eggcases). The anterior apron is broad and straight, while the posterior apron is negligible. The anterior horns are marginally longer than the posterior horns, and often splay outwards.

Remarks. The eggcase of R. undulata is similar in appearance to that of R. montagui (see remarks for R. montagui ) although the eggcase of R. undulata is generally larger and more robust. In this study, whilst the mean eggcase length was within the range of previously reported values, the mean eggcase width actually appeared to be reduced slightly.

One aberrant specimen ( Figure 7 c) was also examined. The capsule was intact, however the anterior apron extended far beyond the typical length, with the anterior horns encompassed by, and extending beyond, this unusually large apron. The eggcase length was 107.0 mm, and despite the posterior horns being slightly damaged, the total eggcase length was approximately 221.0 mm with the eggcase width ranging from 40.0 mm (anterior) to 41.0 mm (posterior). The two surfaces of the apron were fused shut, however there was a tear in the ventral surface at the anterior end of the capsule proper, making it unclear whether or not it had contained an embryo.

Figures

FIGURE 7. Eggcases of (a) Raja montagui, (b) Raja undulata (typical specimen), and (c) R. undulata (aberrant specimen with extended eggcase from Brighton, English Channel).