Raja microocellata Montagu 1818

• Main Authors: Gordon, Cat A., Hood, Ali R., Ellis, Jim R.
• Format: Text
• Language: unknown
• Published: Zenodo 2016
• Subjects: Biodiversity; Taxonomy; Animalia; Chordata; Elasmobranchii; Rajiformes; Rajidae; Raja; Raja microocellata; Montagu; Williamson; Northwest Atlantic
• Online Access: https://dx.doi.org/10.5281/zenodo.5631367; https://zenodo.org/record/5631367

Raja microocellata Montagu, 1818 Distribution. Small-eyed ray ( R. microocellata ) is found in coastal waters from the British Isles south to Morocco, and is locally abundant in certain areas, such as the Bristol Channel (Stehmann & Bürkel, 1984). Juveniles occur in shallow water, while adults occur further offshore, usually in water no deeper than 100 m (Ellis et al. , 2005). Eggcases reported to the Great Eggcase Hunt were usually from the southwestern coasts of England. Material examined. Fifty-seven eggcases were examined in total; the majority (n = 48) were found on beaches and submitted to the Great Eggcase Hunt project, and the remaining eggcases were provided by public aquaria (n = 9). Description. The eggcase of R. microocellata (Figure 6 a) is of moderate size, with a mean eggcase length of 81.2 ± 6.5 mm (70.0– 94.9 mm), and eggcase width of 35.3 ± 4.7 mm (30.7–59.2 mm). Although the eggcase capsule is biconvex, when positioned on its ventral surface the short posterior horns curve upwards, giving the eggcase an overall concave appearance. The capsule has fine, close-packed longitudinal striations on both dorsal and ventral surfaces. The eggcase is broadest across the anterior of the capsule at the base of the horns and usually tapers in width towards the base of the posterior horns, where it is narrowest. Narrow but robust lateral keels extend along the capsule, beginning at the base of the anterior horns and continuing the length of the posterior horns all the way to the tips. The anterior apron is broad and straight but often absent by the time of stranding. The posterior apron is small and concave, stretching the length of the horns. The anterior horns are elongated and narrow into long filamentous tubes which, if intact, can be equal to the capsule length; in contrast, the posterior horns are short, stocky and slightly hooked, curving upwards. Remarks. Anterior horns can be broken easily on stranded specimens as they are fine and delicate. Egg-laying activity peaks between June and September (Ryland & Ajayi, 1984) and recently hatched fish occur in very shallow water, but the exact sites of egg deposition are unknown. The reported size of the eggcase of this species appears to be much larger in early studies (Williamson 1913; Le Danois 1913; Clark 1922) than in subsequent studies including present observations (Table 1). : Published as part of 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, pp. 255-280 in Zootaxa 4150 (3) on pages 268-269, DOI: 10.11646/zootaxa.4150.3.2, http://zenodo.org/record/272101 : {"references": ["Stehmann, M. F. W. & Burkel D. L. (1984). Rajidae. In: Whitehead P. J. P., Bauchot, M. - L., Hureaun, J. - C., Nielsen, J. & Tortonese, E. (Eds) Fishes of the North-eastern Atlantic and the Mediterranean. Vol. I. pp. 163 - 196. UNESCO, Paris, 163 - 196.", "Ellis, J. R., Cruz-Martinez, A., Rackham, B. D. & Rogers, S. I. (2005) The distribution of chondrichthyan fishes around the British Isles and implications for conservation. Journal of Northwest Atlantic Fishery Science, 35, 195 - 213. http: // dx. doi. org / 10.2960 / J. v 35. m 485", "Ryland, J. S. & Ajayi, T. O. (1984) Growth and population dynamics of three Raja species in Carmarthen Bay, British Isles.", "Williamson, H. C. (1913) On the eggs of certain skates (Raia). Scientific Investigations, Fishery Board for Scotland, 1912 Part I, 3 - 6 and 5 plates.", "Le Danois, E. (1913) Contribution a l'etude systematique et biologique des poissons de la manche occidentale. Theses, Faculte des Sciences de Paris, 214 pp.", "Clark, R. S. (1922) Rays and Skates (Raiae) No. I: Egg capsules and young. Journal of the Marine Biological Association of the United Kingdom, 12, 577 - 643. http: // dx. doi. org / 10.1017 / S 002531540000967 X"]}