III. On the structure and development of the skull in sturgeons (Acipenser ruthenus and A. sturio)

Abstract

S e v e r a l years ago the late Mr. W i l l i a m L l o y d procured for me from Hamburgh seventeen young Sturgeons (A cipensersturio); these were from 7 to 8 inches in length. Valuable as these specimens were, they were far too much developed for embryological purposes; and no pains were spared by me to obtain, if possible, newlyhatched embryos and small " fry" of this type. More lately it was suggested to me by Mr. B a l f o u r that I should write to Professor W. S a l e n s k y , of Kasan, who had been working at the development from the egg of Acipenser r u t h e n u s , the small Sturgeon or " Sterlet. "t My. application to him was promptly and most kindly responded to, and in a short time I received a considerable number of newly-hatched and very small young of that species, ranging from 5^ to 14^ millims. in length. Half these were for Mr. B a l f o u r , and the rest for me. His researches are embodied in that inestimable work, the second volume of his * Comparative E m bryologym ine are here offered to the Society in the accustomed form. I purposely refrain at present from working out the structure and development of the trunk and limbs (I have laboured at these regions, and shall be ready to resume that part of my work when this is done); but other workers are from time to time taking up those parts, and when once the cephalic skeleton is mastered what remains will be a comparatively easy task. I am more anxious to be prepared for my own limited work by acquiring a thoroughly clear conception of the embryology of each ty p e ; in this my best helper is Mr. F. M. B a l f o u r. Professor H u x l e y is, and always has been, my most valued critic and counsellor in all that relates to broad and philosophical views of animal life generally, and of the life of the Vertebrata in particular. * The skull described in my last paper as that of (Phil. Trans., 1881, Plate 20, figs. 7-11, p. 112) was prepared from a badly-preserved, half-grown Hana esculenta. I am indebted for this correction, and for a genuine Discoglossue, to M. B oulenger. t This species rarely exceeds the length of 3 feet (G unther, ' Study of Fishes,' p. 3 6 1). T 3 * These do not correspond precisely to the specimens worked out by me, and of which I also have given figures illustrating the outward form. My first Stage includes larvae from 5^ millims. to 6^ millims. in total length; Stage two, 8^ millims. to 9 | m illim s.; and Stage three, 1 3 | millims. to 14^ millims. The largest larva of this species in those sent to me was 1 4 | millims. (-j^-ths of an inch) in total length, * I am glad to be able to give, and the reader will not be sorry to have, an account of these early larvse m Mr. B alfour's own words. Of course I have been over the same ground, but my work has been made much easier by my friend's kindness in sending me his proofs as soon as they were in type. * Through want of proper food these larvre soon began to starve. Moreover, the spirit in which they were preserved contracted their tissues; the figures purposely show this co...

What is missing from the sturgeon jaw: Developmental morphology of the upper jaw in Acipenser

“…The morphology of the sturgeon's upper jaw has been discussed and illustrated in a large number of papers (Arratia & Schultze, 1991; De Beer, 1937; Bridge, 1878; Grande & Bemis, 1991; Hilton et al, 2011, 2020; Holmgren & Stensiö, 1936; Jollie, 1980; Marinelli & Strenger, 1973; Parker, 1882; Pehrson, 1944; Sewertzoff, 1926, 1928; Stensio, 1925, 1932; Traquair, 1887; Van Wijhe, 1880; Warth et al, 2017; Watson, 1925), yet certain specific features have remained undocumented and deserve mentioning in the present discussion.…”

“…The upper jaw complex of the sturgeon (Figures 1a and 2a–d) is composed of the left and the right jaw rami and a broad unpaired cartilaginous plate (Figure 1a, Ppl) attached by connective tissue to their dorsal margins. This plate consists of a variable number of separate cartilages which are all set in one common web of connective tissue (see Bugajew, 1930; Findeis, 1993; Hilton et al, 2011; Parker, 1882; Warth et al, 2017). Referred under various names (Hilton et al, 2011) and of uncertain homology (Holmgren, 1943: 66), this plate is beyond the scope of the present account.…”

“…There are not too many works that describe the mandibular arch development in sturgeons. Most of them deal with advanced developmental stages when the skeletal elements were already in a prochondrial or chondral state (De Beer, 1925, 1937; Findeis, 1993; Jollie, 1980; Parker, 1882; Warth et al, 2017). The earlier (mesenchymous) stages were studied by Sewertzoff (1928), Holmgren (1943) and partly by Edgeworth (1928), Neumayer (1932) and Bertmar (1959).…”

“…Each pair develops from single anlagen, which later divides into the inner and the outer tentacles (Holmgren, 1943; Savatsky, 1911). As described long ago by Parker (1882), each tentacle is supported by an inner cartilaginous rod, the tentacular cartilage, which histologically resembles the elastic cartilage (Saadatfar & Shahsavani, 2007; Weisel, 1979). The tentacular cartilages differentiate from the mesenchyme, which detaches from the anterior end of the mandibular arch mesenchyme (see Figures 5 and 6), and move forward in parallel with the elongation of the ethmoidal and rostral regions.…”