A series of normal stages for development of Scyliorhinus canicula, the lesser spotted dogfish (Chondrichthyes: Scyliorhinidae)

Abstract

By observing numerous living eggs from the lesser spotted dogfish Scyliorhinus canicula (L.) caught near Roscoff (France) and reared at recorded temperatures as they developed from first cleavage to hatching, the first reasonably complete developmental table was worked out for this classical material in vertebrate embryology. The successive stages, described and numbered from 1 to 34, correct and replace the incomplete stages A-Q proposed by Balfour (J. Anat. Physiol., 10:555-576,1876) and other even less complete series later published, and is unique in the inclusion of a timetable at 16°C. The stages can be identified, usually through the cleared eggshell wall, with naked eye or low magnification. Normal-series stages have been published for most of the animal species widely used in experimental embryology? as an aid to others in confirmation of results. An attempt is usually made to mark each stage by the first appearance of some easily recognized structure or event; the usefulness of a series depends on the closeness and obviousness of the steps, and upon a timetable of their appearance under defined conditions such as temperature. For example, landmark series in continued use are those for Ambystoma (essentially finished by Harrison in 1927 and widely distributed privately before publication in 19691, for the chick (Hamburger and Hamilton, ,511, Xenopus (Nieuwkoop and Faber, ,561, Pleurodeles (Gallien and Durocher, '57), the sturgeon (Dettlaff and Ginsburg, '54), and Salmo (Vernier, '69). Others have been published as necessary adjuncts to particular researches on less commonly used species with narrower focus, e.g., Ballard ('86) on A m i a calua, following earlier studies on several teleost species. Such normal development series for a large number of both invertebrate and vertebrate species has been brought together by Dettlaff and Vassetzky (originally in Russian, later translated to English, '90) but still not including any elasmobranch species.Earlier such collections usually included wider gaps and lacked timetables, though serving well the consolidation of comparative descriptive embry-ology. In the first of several volumes edited by Oskar Hertwig and intended to summarize vertebrate embryology, Franz Keibel('O6) re-issued the illustrations of already published normal series of representatives of all classes from cyclostomes to mammals, whose descriptive embryology was being synthesized by the other authors.At that time the single major study of elasmobranch development was that of Balfour (1876). Despite the high reputation of that author, the defects of his normal series were well recognized. Earliest and latest stages of development were inadequately covered, his Stage E was admittedly abnormal, and he had had to fill gaps in what was otherwise a series for "Scyllium" (now Scyliorhinus) with specimens of the shark "Pristiurus" (now Galeus melastomus) and the electric ray Torpedo. No time sequence could be offered for any of his haphazard collections.In spite of this, the Balfour Stages A-Q...

Noncanonical role of Hox14 revealed by its expression patterns in lamprey and shark

“…Embryonic stagings of S. torazame and L. japonicum were based on Ballard et al (28) and Tahara (29), respectively. Total RNA of S. torazame was extracted from a whole embryo at stage 12.…”

Early Palaeozoic dentine and patterned scales in the embryonic catshark tail

“…Staged embryos (Ballard et al 1993) were removed from egg cases, anaesthetized (MS222) and tails anterior to the caudal fin were removed. These were processed in 4% PFA for in situ hybridization with a probe for Scshh (S. canicula sonic hedgehog gene), SEM or histological examination.…”

Expression of FoxC, FoxF, FoxL1, and FoxQ1 genes in the dogfish Scyliorhinus canicula defines ancient and derived roles for fox genes in vertebrate development

“…The results are depicted in Figures 2-7, and embryo staging is as previously described (Ballard et al, 1993). S. canicula gene expression relative to other gnathostomes is summarized in Table 1. S. canicula foxc1 expression in paraxial mesoderm derivatives.…”

“…S. canicula foxq1 marks the pharyngeal endoderm and gill buds. The later start to form at stage 24, presumably to increase the respiratory surface until the onset of pharyngeal respiration at stage 32 when they start to regress (Ballard et al, 1993). However, the function of the gill buds may not be restricted to respiration, and it has been shown that the gill buds of S. canicula are related to the parathyroid of tetrapods and are involved in regulating extracellular calcium levels (Okabe and Graham, 2004).…”