| Summary: | 碩士 === 國立成功大學 === 生物學系 === 84 === The sexual dimorphism, osteology, histology, feeding behavior
and morphometric study of the Acrossocheilus paradoxus are
described. The existance of protuberances on the anal fin and
the epidermis around the anal fin can be used as a character to
distinguish between the male and the female Acrossocheilus
paradoxus. The branchial arches of Acrossocheilus paradoxus
contain basibranchials, hypobranchials, ceratobranchials,
epibranchials, and pharyngeobranchial, which are lacking in the
common carp, Cyprinus carpio, but are present in most of the
other cyprinid fishes. The presence of metazygapophysis between
body vertebrae can protect the spinal cord of Acrossocheilus
paradoxus from injury when the fish is swimming in fast water.
Besides, there are ligments connecting the end of the 12th ribs
and the bases of the outer most ventral fin rays in
Acrossocheilus paradoxus. This connection can increase the
maneuverability of the pelvic fins, hence, increase its moving
ability. Acrossocheilus paradoxus has three rows of canine
pharyngeal teeth on the fifth brachial arches. The external
muscle layer of the digestive tract is not well developed,
however, the mucosal layer are well developed and heavily folded
in Acrossocheilus paradoxus. The histology of digestive system
in the Acrossocheilus paradoxus is similar to that of the other
carnivorus fishes. The spermatogonia in Acrossocheilus
paradoxus distributed along the entire length of the testicular
tubules, indicating the fish can breed repetitively within one
breeding season. The number of the photoreceptors are greater
than the olfactory receptors, suggesting the optic system of the
Acrossocheilus paradoxus are better developed than the olfactory
system. This may have great help in catching prey in clear
water. There are three types of tail development, including
upward growing, symmetric growing and downward growing. These
three kinds of growing patterns are related to neither
collection sites nor sex. The causes of different growth of the
tail remain to be studied. The intestinal contents include many
chitinous exoskeleton of water insects, fiberous algae, and
diatoms, excluding snails, mussels, and other fishes. The
digestive contents and the digestive histology suggest that
Acrossocheilus paradoxus is carnivorous.
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