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In this article we will discuss about the dissection, structure and salient features of frog and toad.
1. Hyoid Apparatus of Frog and Toad:
Rana sp. (Frog); Bufo sp. (Toad)
The hyoid apparatus of frog and toad are almost similar in structure. They occupy the same relative position.
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Preparation:
Remove the skin of the ventral surface of the buccal floor and the anterior portion of the thorax. The body of the hyoid is situated just dorsal to the ventral muscle of the buccal floor. Give a superficial, median longitudinal incision on the ventral muscle with a pair of fine scissors and expose the body of the hyoid.
Remove the muscles to trace anterolaterally directed anterior cornua up to their point of fusion with the auditory capsules. Separate, the cornua from the capsules. Trace the posterior cornua posterolaterally. They lie on either side of the pectoral girdle.
Remove the hyoid apparatus and put it in 10% KOH solution in a watch glass to facilitate clearing of the muscles. Wash thoroughly with water till the last trace of KOH is removed. Mount in glycerine.
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Structure:
(Figs. 29.7 & 29.8)
i. The body is a thin shield-shaped, cartilaginous plate.
ii. Anterior cornu are two curved, slender rods running anteriorly and then postero-laterally.
iii. Posterior cornu are two partly ossified diverging rods.
2. Tadpole Larva of frog and Toad:
Since the frogs and toads breed only in monsoon, live tadpole larvae are available in this period only. Tadpoles well preserved in 6% formaldehyde or 70% alcohol are, however, equally good.
Preparation:
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The larvae, with external gills even at the early stage, is quite large and pigmented, and unfit for microscopic studies in whole mount. A powerful hand lens is sufficient for the study of detailed external structures. There is no point in staining a tadpole larva. Dehydration requires quite a few days.
Salient features:
(Fig. 29.9)
i. Fish-like, with three distinct regions; an ovoid head, a short trunk and a tail.
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ii. Body oval, the laterally compressed tail long.
iii. Mouth at the anterior end.
iv. A pair of lateral eyes.
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v. The ventral sucker slightly behind the mouth.
vi. The coiled intestine visible through the ventral body wall.
