The pathogenesis of the first and second branchial arch
Cohen Jr., "Variability versus "incidental findings" in the first and second branchial arch
syndrome: unilateral variants with anophthalmia," Birth Defects Original Article Series, vol.
Distinguished from all other congeners by the combination of the following features: anterior portion of trunk wider than deep, jaws short, snout blunt, tip of anal fin rounded in male, caudal fin elliptical to acuminate in male, pelvic-fin tip not reaching to urogenital papilla in male, dorsal-fin origin posterior to anal-fin base, dorsal-fin rays 5-6, anal-fin rays 8-10, frontal squamation S-patterned, frontal scales arranged circularly, canal preopercular short and opened, contact organs absent, longitudinal series of scales 32-34, gill rakers of first branchial arch
1 + 7, dark brown oblique bars on flank, transverse black bar through the chin, and no black spot on dorsal portion of caudal fin.
A combined third and fourth branchial arch
anomaly: Clinical and embryological implications.
(37) By the 4th week of embryonic life, 4-paired mesodermal arches are apparent externally, with smaller 5th and 6th branchial arches
not well visualized.
Diagnosis: Astyanax minor is distinguished from Iguacu Astyanax by combination of following characters: infraorbital 3 deep but not in contact with preopercle, leaving a narrow naked area between its border and preopercle; premaxillary external series with 4-6, usually 5 or 6 pentacuspid or heptacuspid teeth; first branchial arch
9-12, usually 10 rakers in upper branch and 13-16, usually 14 or 15 rakers in lower branch; a narrow and elongated vertical humeral bar.
Five new species of genus Astyanax Baird & Girard, 1854 from Rio Iguacu, Parana, Brazil (Ostariophysi, Characiformes, Characidae)/ Cinco novas especies do genero Astyanax Baird & Girard, 1854 do Rio Iguacu, Parana, Brasil (Ostariophysi, Characiformes, Characidae)
Similarly, there is an apparent modal difference in the total number of gill rakers on the first branchial arch
In our present findings, of the additional slip in the clavicular origin of sternocleidomastoid muscle may be due to abnormal splitting in the mesoderm of post-sixth branchial arch
. However, the relevance of our findings whether it is associated with the condition of wry neck and other congenital deformities of the neck needs to be evaluated by further studies.
There is also a possible difference in the number of gill rakers on the first branchial arch
. Randall and Masuda (1991) indicated a range of 14-17 gill rakers for six specimens of C.
peruvianus and III-7 for Eucinostomus and Gerres sp.) and by the branchial spines in the inferior branch of the first branchial arch
(13 to 14 for D.
The first and second branchial arches
and the first pouch contribute to the development of the middle ear.
Postulated factors include disturbance of the interactions of growth factors,2 teratogenic drugs like meclizine,7 trauma late in pregnancy and local ischaemia and amniotic bands causing pressure on the first branchial arch
.8 The maternal history did not reveal any such cause in this case.