Whenever possible, the number of myomeres
, spines, and rays of dorsal, anal, caudal, pectoral, and pelvic fins were recorded.
They have also found that the flattened eel-like creatures had skeletal muscles called myomeres
and a basic blood vessel system.
Another characteristic of chordates are myomeres
, blocks of muscle tissue often arranged in a zig-zag pattern.
The number of myomeres
distinguishes species: Indonesian leptocephali have about 10 fewer myomeres
than the 112 to 118 typical of Japanese larvae.
A small group of spots is present on the ventral body margin near the last 2 or 3 myomeres
and an additional 3 or 4 spots are located along the ventral margin of the notochord beyond the last myomere
0 mm BL) typically have three equidistant blotches on the distal margin of the dorsal fin fold, located approximately between myomeres
6-9, 16-19, and 28-33, and an additional blotch located on the dorsal margin of the body between myomeres
28 and 33.
Larvae of northern sculpin have 35-36 myomeres
, pelvic fins with one spine and two rays, a bony preopercular shelf, four preopercular spines, 3-14 irregular postanal ventral melanophores, few, if any, melanophores ventrally on the gut, and in larger specimens, two rows of ctenoid scales directly beneath the dorsal fins extending onto the caudal peduncle.
During days 17-21, the optic capsule and eye lenses formed, the head and anterior body became thick and more defined, and the notochord, myomeres
, and Kupffer's vesicle became visible (Table 1).
The larvae of both are characterized by having 24-25 myomeres
, a large triangular gut (54-67% of BL) in postflexion larvae, small spines on the preopercle and interopercle, a smooth supraocular ridge, a small to moderate gap between the anus and the origin of the anal fin, and distinctive pigment patterns.
Pseudopercis semifasciata larvae were distinguished from other larvae by the modal number of myomeres
(between 36 and 38), their elongated body, the size of their gut, and by osteological features of the neuro- and branchiocranium.
Because of the difficulty in accurately counting myomeres
in transforming clupeids (Hettler, 1984; Ditty et al.
were difficult to count reliably at either end and thus vertebral counts (which include the urostyle) of stained larvae were taken instead.