In our morphometric analysis of the cartilage structure, both the control and slincR morphants exposed to TCDD exhibited cartilage malformations; however, the slincR morphants showed an abnormal junction between hyosymplectic and ceratohyal cartilages in comparison with control morphants.
The position of jaw structures representing junctions between Meckel's and palatoquadrate cartilages (point A and B) and representing junctions between the hyosymplectic and ceratohyal cartilages (point C and D) was measured relative to a reference point as shown.
Miyake & McEachran (1991) have considered that the pseudohyal cartilage originally appeared to function as the
ceratohyal cartilage in sharks (Compagno, 1977), which is reduced in torpedinoids (Fechhelm & McEachran, 1984).
The interhyoideus is a broad muscle, originating at the lateral margin of the
ceratohyal extending medially to insert on the midline.
Hyobranchial apparatus: Comprising median unpaired glossohyal, basihyal, three basibranchials and urohyal; and bilaterally paired dorsal and ventral hypohyals, anterior and posterior
ceratohyals, interhyal, six branchiostegal rays, three hypobranchials, five ceratobranchials, four epibranchials and three pharyngobranchials (Fig.10).
For example, in the neurocranial cartilage of larvae exposed to 5 x [10.sup.-7] M RA as gastrulae, the ventral elements of all seven arches can be found (Meckel's cartilage in the mandibular arch, the
ceratohyal in the hyoid arch, and the ceratobranchials in the branchial arches).
Well-developed, posterodorsally pointed dorsal process of posterior
ceratohyal. [0] Not present (e.g.
(3) Reichert's cartilage is divided into a dorsal segment (Which forms stapes), tympanohyal, stylohyal, epihyal and
ceratohyal. Segments.
3); one pair of slender uroneurals; three epurals; a free parhypural; three thin supraneurals, generally straight; two supernumerary spines on first dorsal pterygiophore; no procumbent spines (spurs); thin Y-shaped basisphenoid, free from parasphenoid and prootics; neurocranium with frontal tabs similar to Vincentia Castelnau, 1872 (Fraser 1972: pl 31); supramaxilla absent; posttemporal smooth or with 1-3 small serrae on posterior margin; preopercle with 2-3 small, widely spaced serrae near angle, ridge smooth; infraorbitals smooth; infraorbital shelf present on third bone; ring of scleral cartilage, no ossification present; 7 branchiostegals;
ceratohyal notched, suture smooth with epihyal; urohyal with short anterior process.
Postero-ventrally, the angulo-articular is ligamentously connected to both the interopercle and the posterior
ceratohyal. Postero-dorsally, it presents an articulatory facet for the quadrate-symplectic.
Ceratohyal and epihyal cartilages continually expand until 9 DPH when the hyoid reaches its maximum depth and has the full complement of six branchiostegal rays.
It is L-shaped and is attached, by means of strong ligaments, to both the posterior
ceratohyal and the hyomandibulometapterygoid.