Figure 1.
Buccal pumping of 58.6 mm TL embryo of the cloudy catshark (Scyliorhinus torazame) in ventral view.
A. Digitized points for quantifying the movement of mouth and pharyngeal regions. Descriptions of each measurement point (a, a′, b, and b′) are shown in Material and method section. Scale bar = 2 mm. B. Changes of amount of mouth opening (above) and head width at the first gill slit (below) over time. Gray areas in above figure indicate the duration of mouth closing that represents the compression phase of oro-pharyngeal cavity. Arrows in below figure indicate the timing of the opening of the first gill slit.
Figure 2.
Morphological change of head and pharyngeal regions through ontogeny.
A. 19.2 mm TL. B. 21.9 mm TL. C. 27.2 mm TL. D. 43.6 mm TL. E. 53.3 mm TL. F. 75.1 mm TL. Scale bars = 2 mm. eg = external gill filaments, sg = spiracular gill filaments.
Figure 3.
Length (±standard deviation) of the external gill filaments on the first gill slit for 35 embryos.
The above figures represent the ventral view of the head and pharyngeal region. 1st eg = external gill filaments on the first gill slit.
Figure 4.
Development of pharyngeal skeletal and muscular elements in the pharyngeal region.
A. Schematic diagram of the pharyngeal skeletal and muscular elements of the adult cloudy catshark. B. 3-dimensional reconstructions of pharyngeal skeletal and muscular elements made from histological thin sections. Ventral view of the jaw and pharyngeal skeletal elements (blue) and the hyoid retraction muscle (coracohyoideus; red) in 27.2 mm TL (i), 29.2 mm TL (ii), 32.8 mm TL (iii), and 39.8 mm TL (iv) embryos. Scale bars = 500 µm.
Figure 5.
Development of anterior-side gill lamellae.
A. Lateral view of the head region of a cloudy catshark embryo (left), and schematic diagram of the embryonic gill structure (right). Posterior-side gill lamellae (external gill filaments) are elongated and extend out of the gill slit, whereas lamellae on the anterior side develop and remain inside the gill slit. B. Histological thin sections of the anterior-side gill lamellae on the first gill arches of 23.2 mm TL (i), 27.2 mm TL (ii), 32.8 mm TL (iii), 39.8 mm TL (iv), and 53.5 mm TL (v) embryos. Sections were made along the dotted line (x–x′) in figure of A, right side. Black triangles represent efferent lamellar arteries; white triangle, afferent lamellar arteries. BM represents basal membrane. Asterisks (*) in the efferent and afferent lamellar arteries represent red blood cells. The images in (iii), (iv) and (v) are horizontally flipped to allow for easier comparison. Scale bar = 50 µm. C. Close-up view of the anterior-side gill lamellas of 25.8 mm TL (i), 32.8 mm TL (ii), 39.8 mm TL (iii), and 53.5 mm TL (iv) embryos. Basement membrane (bm) was stained in purple with PAS staining in narrow space beneath the single- or double-layered epithelium cells (i). Secondary gill lamellas (arrows) and blood cells (*) in the blood vessels present within the gill lamella in (iii) and (iv). Scale bars = 10 µm.
Figure 6.
Development of the oral valve (OV).
Ventral views of the mouth region of 16.7 mm TL (A), 23.2 mm TL (B), 26.0 mm TL (C), 38.4 mm TL (D), 46.9 mm TL (E), and 53.3 mm TL (F) embryos. Scale bars = 0.5 mm in (A) and (B). Scale bars = 1.0 mm in (C), (D), (E), and (F).