The initial anatomical regions with osteological development were mandible, pectoral fin (cleithrum), ceratobranchial and
gill arches at 3 DPH in crimson snapper.
The same result was obtained when comparing segments at the
gill arch level (Table 4).
In the branchial region these fishes all have paired symmetrical
gill arch bones that support pharyngeal tooth plates, gill rakers and gill filaments (e.g., studied by Frame et al.
The lower jaw, teeth, and Meckel's cartilage develop when cells of the cranial neural crest (CNC), which give rise to the dorsal neural tube, migrate into the
gill arches (1-3).
The semilunar base of each gill raker is attached to the mucous membrane of the
gill arch. The longest gill takers occur near the center of the arc and are about 9 cm long in the LACM specimen.
There was also staining in the endothelium of vessels in the
gill arches of the DR fish.
The two structures of primary importance in the transition from agnathan (jawless) fish to gnathostomes were the mandibular arch (
gill arch 2) and the hyoid arch (
gill arch 3).
a) Trichodinids in a fresh-mounted smear from the
gill arches, b) differential interference contrast microscope, c) an adhesive disc of Trichodina in silver nitrate impregnation, d) T.
Each
gill arch is divided into a long ceratobranchial part and short epibranchial part.
The degeneration and necrosis were also observed within the gill filaments along with a dilation of the
gill arch in which it expands as compared to its normal condition as shown in Figure 1C.
These indexes are calculated as follows: H'= - Pi [s.summation over (i=1)] [log.sub.2] Pi and E = H'/[log.sub.2]S where for a given
gill arch, Pi represents the relative abundance of parasite species i and S corresponds to the specific richness.