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広島大学水畜産学部紀要 16 巻 1 号
1977-08-20 発行
イボイモリ(Tylototriton andersoni) の発生
On the Development of Tylototriton andersoni
宇都宮 泰明
宇都宮 妙子
Abstract
イボイモリの発生を,イモリおよびシリケンイモリの発生と対比しながら,岡田・市川(1947)の発生段階図によって記述した。イボイモリの受精卵は径3.0mm～3.2mm。卵包は球形でゼリー質の3層からなる。動物極側は淡黄褐色,植物極側は淡黄白色。胚および幼生期の発生はシリケンイモリよりはるかに速く進行する。イモリと比べると卵割期から神経胚の初期までは発生が遅れるが,それ以後は発生が速く進む。他の2種の発生と比べて特に外観的に異なる点をあげると,(1)眼胞の輪郭および瞳の形成が遅れること,(2)平衡桿の発達が悪いこと,(3)腹部が多量の卵黄のため,尾芽期まで球形をしていること,(4)外鰓の発達が極めてよく形は櫛状であること,(5)背部の膜びれは胴部のほぼ中央から始まること,(6)後肢丘の出現が早いこと,(7)後肢2趾期頃から肋皺がみられること,(8)前肢第5指の出現が遅いこと,(9)頭部諸器官の原基の輪郭がよく目立つこと,(10)心臓部付近をおおう皮膚が大きくふくらんでいることなどである。
Abstract
The development of Tylototriton andersoni was described by comparing with those of Cynops pyrrhogaster pyrrhogaster, and C. p. ensicauda. The determination of the developmental stages was made in accordance with those of C. p. pyrrhogaster (Okada and Ichikawa, 1947).
The fertilized eggs of Tylototriton andersoni were 3.0～3.2 mm in diameter. Each of them was enveloped in a spherical jelly capsule which consisted of three concentric layers. The eggs were light yellowish-brown in the animal hemisphere, while yellowish in the vegetal one.
The eggs of Tylototriton andersoni develop more rapidly than those of Cynops pyrrhogaster ensicauda in the embryonic and larval stages while they are somewhat slower than the eggs of C. p. pyrrhogaster in developmental velocity during the period from the cleavage to the early neurula. After this period, they develop more rapidly than the latter.
The embryos and larvae of Tylototriton andersoni are especially different from those of Cynops p. pyrrhogaster and C. p. ensicauda in the following respects. (1) The outlines of an optic vesicle and the pupil appear more slowly. (2) The balancer is ill developed. (3) The belly of a tail-bud embryo is spherical, due to a large content of yolk. (4) The external gills are well developed and comblike. (5) The dorsal dermal fin arises approximately from the middle of the body (trunk). (6) The hind-limb bud appears more earlier. (7) The costal folds appear at the two-toed stage. (8) The rudiment of the fifth finger appears later. (9) The rudiments of various cephalic organs are more conspicuous in outlines. (10) A dermal swelling covering of the heart region is more conspicuous.
The fertilized eggs of Tylototriton andersoni were 3.0～3.2 mm in diameter. Each of them was enveloped in a spherical jelly capsule which consisted of three concentric layers. The eggs were light yellowish-brown in the animal hemisphere, while yellowish in the vegetal one.
The eggs of Tylototriton andersoni develop more rapidly than those of Cynops pyrrhogaster ensicauda in the embryonic and larval stages while they are somewhat slower than the eggs of C. p. pyrrhogaster in developmental velocity during the period from the cleavage to the early neurula. After this period, they develop more rapidly than the latter.
The embryos and larvae of Tylototriton andersoni are especially different from those of Cynops p. pyrrhogaster and C. p. ensicauda in the following respects. (1) The outlines of an optic vesicle and the pupil appear more slowly. (2) The balancer is ill developed. (3) The belly of a tail-bud embryo is spherical, due to a large content of yolk. (4) The external gills are well developed and comblike. (5) The dorsal dermal fin arises approximately from the middle of the body (trunk). (6) The hind-limb bud appears more earlier. (7) The costal folds appear at the two-toed stage. (8) The rudiment of the fifth finger appears later. (9) The rudiments of various cephalic organs are more conspicuous in outlines. (10) A dermal swelling covering of the heart region is more conspicuous.
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