7) The etiology of the frequently associated ossicular chain anomalies maybe traced to an error in the development of the second branchial arch
prior to the fourth month of intrauterine life.
The base is fixed to the branchial arch
by connective tissues and perforated by nutrient canals along the entire basal edge.
Management of congenital fourth branchial arch
anomalies: A review and analysis of published cases.
Description: Dorsal rays IX, 20 (18-19, see Table II); anal rays II,12 (II,13); all dorsal and anal soft rays branched except first, last dorsal and anal rays branched to base; pectoral rays 18 (17-18, see Table II); upper and lowermost pairs unbranched; pelvic rays I,5; branched caudal rays 15; scales in longitudinal series 63/64 (51-63); tubed lateral line scales 48/42 (33-46); scales below lateral line to origin of anal fin 21 (20-21); scales above lateral line to middle of dorsal fin base 5; gill rakers on first branchial arch
6 + 12 (5-6 + 11-12).
Distinguished from all other congeners by the combination of the following features: anterior portion of trunk slightly deeper than wide, jaws short, snout blunt, tip of anal fin rounded in male, caudal fin rounded in male, pelvic-fin tip not reaching anus in male, dorsal-fin origin on vertical between base of last 3rd and 4th anal-fin rays, dorsal-fin rays 7-8, anal-fin rays 12-14, frontal squamation E-patterned, frontal scales arranged circularly, canal preopercular short and opened, contact organs absent, longitudinal series of scales 37-40, gill rakers of first branchial arch
1-2 + 8, red stripes on flank, jaws not distinctively pigmented, and round black spot on dorsal portion of caudal fin in female.
Approximately 95% of these anomalies are derived from the second branchial arch
and are incomplete; they often present within the first 2 decades of life.
The upper teeth are curved towards the middle of the pharynx, but the lower teeth project at right angles to the surface of the branchial arch
, across the flow of water.
Mouth longer, upper jaw 2 reaching to below pupil; gill opening broader, extending forward to below middle or posterior part of pupil; caudal fin without enlarged black spots; tongue tip bilobed; pectoral rays 13-15; pelvic rays unbranched; second dorsal spine longest; 13-18 elongate and pointed gill rakers on outer face of lower part of first branchial arch
Gill rakers small, the longest on first branchial arch
less than half length of longest gill filaments.
Of these diverse anomalies, second branchial cleft lesions are the most common, accounting for approximately 95% of all branchial arch
1) It occurs as the result of a developmental anomaly of the first branchial arch
, and it may be associated with other branchial cleft abnormalities.