Descriptions and revised key to the eggcases of the skates (Rajiformes: Rajidae) and catsharks (Carcharhiniformes: Scyliorhinidae) of the British Isles
Author
Gordon, Cat A.
Author
Hood, Ali R.
Author
Ellis, Jim R.
text
Zootaxa
2016
4150
3
255
280
journal article
10.11646/zootaxa.4150.3.2
8347a890-caad-4a81-8a02-8ec476083ffb
1175-5326
272101
08E63512-49DB-495C-83FC-CDF206A516CF
Leucoraja naevus
(Müller & Henle, 1841)
Distribution.
Cuckoo ray (
L. naevus
) is relatively widespread in the Northeast Atlantic, occurring from
Morocco
to
Norway
, including the Mediterranean Sea (
Stehmann & Bürkel, 1984
;
Serena
et al.,
2010
). Juveniles are found further offshore than the young of
Raja
spp. (
Ellis
et al.,
2005
). Records submitted to the Great Eggcase Hunt were collected predominantly from southwest
England
, although verified reports have been made along the southern and western coasts of
England
and
Wales
, with scattered reports from
Scotland
and the Northern Isles.
Material examined.
Ninety-four specimens were examined overall, including those recorded from the Great Eggcase Hunt (n = 52) and trawl surveys (n = 39), with three museum specimens also examined (
BMNH
1927.1.31.1–3).
Specimens
from trawl surveys were captured primarily by beam trawl in the
western English Channel
and Celtic Sea, over the area from 49.1–
50.9°N
and 3.9
–6.7°W, and in waters
84–118 m
deep.
Description.
The eggcase of
L. naevus
is small (eggcase length 50.0 ±
13.2 mm
;
31.6–65.2 mm
) but has extended horns (
Figure 2
c), and the range of total eggcase length is
156.8–197.9 mm
. The three historical specimens examined closely matched the size range recorded in contemporary samples. Both dorsal and ventral surfaces are convex, with obvious longitudinal striations on both surfaces. The eggcase is without keels and the dorsal and ventral surfaces meet seamlessly at the margin. The anterior apron is pronounced and convex whereas the posterior apron is sometimes lacking. The anterior horns are long (on average representing 48% of the entire eggcase length) and in complete specimens curve inwards and often overlap. The posterior horns are shorter than the capsule length and often terminate in hooks.
Remarks.
As the anterior horns are so long and delicate, they are often broken in strandline specimens, which can sometimes cause confusion with
Raja montagui
Fowler, 1910
when attempting identification. However, as the capsule is biconvex and has a more rounded appearance, it is still distinct from the other species found in European inshore waters. The mean eggcase width in the present study was within the range of previous reports (
Table 1
), but mean eggcase length was slightly shorter than recorded in earlier studies.
No comparative material for the related sandy ray
Leucoraja circularis
(Couch, 1838)
and shagreen ray
Leucoraja fullonica
(Linnaeus, 1758)
were available during this study. Some of the earlier descriptions of the eggcases of what was purported to be
L. circularis
should be treated with care, as cuckoo ray was sometimes referred to as
Raia circularis
in early accounts, as noted by
Clark (1922)
. Both
L. circularis
and
L. fullonica
have eggcases of similar shape to
L. naevus
, with preliminary descriptions given by
Desbrosses (1931)
. The eggcases of these two species are both larger than the cuckoo ray, ranging from
83–92 mm
long and
45–53 mm
wide in
L. circularis
and
75–89 mm
long and
45–67 mm
wide in
L. fullonica
(
Desbrosses, 1931
;
Wheeler, 1969
;
Table 1
).