Ontogeny of Cheliped Laterality and Mechanisms of Reversal of Handedness in the Durophagous Gazami Crab, Portunus trituberculatus
Ontogeny of Cheliped Laterality and Mechanisms of Reversal of Handedness in the Durophagous Gazami Crab, Portunus trituberculatus
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三疣梭子蟹硬食性伽扎米蟹螯肢侧向的个体发育和利手逆转机制
DOI：
10.1086/707648
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Saigusa Masayuki
中科院分区：
文献类型：
--
作者：
Masunari Nobufumi;Sekine Kazuki;Kang Bong Jung;Takada Yoshitake;Hatakeyama Masatsugu;Saigusa Masayuki
Gazami蟹（Portunus trituberculatus）的成对爪是双侧不对称的，在第一感觉足的远端两节即指趾和拟足上的不对称是显著的。壳只通过使用右螯来破裂，代表手性。在Gazami蟹中，右螯切开术后，手性反转。本研究的重点是手性的个体发生和手性逆转的机制。在形态学上，不对称首先在巨足虫幼虫中发现，右足明显大于左足，右趾基部的犬齿也是如此。据推测，左、右螯合速率不同。有了这些形态特征，右螯就起了粉碎器的作用。破碎机施加的闭合力是铣刀的两到三倍。随着右侧破碎机的丢失，左侧螯合比再生的右侧螯合更大，并转变为破碎机。相比之下，再生后的右螯合的性能较原右粉碎机差，更活跃的左螯合抑制了完全闭合力的发挥。此外，具有两个破碎螯的螃蟹并没有明显地表现出惯用手性。再生右螯合的大小和性能下降可以用默认程序假设来解释。综上所述，螯合速率的差异导致两足的双侧不对称，然后手性是由支配这些爪子的胸神经节的神经调节产生的。由于手性在自体切开术后逆转，Gazami蟹的胸神经节不会侧化。提出了一个默认程序假设来解释双侧螯合不对称和手性反转的个体发生。
The paired claws in Gazami crabs,Portunus trituberculatus, are bilaterally asymmetrical, and asymmetry is remarkable on the distal two segments of the first pereiopod, that is, the dactylus and propodus. Shells are exclusively cracked by use of the right chela, representing handedness. In Gazami crabs, handedness is reversed after autotomy of the right chela. Our study focused on the ontogeny of handedness and the mechanism of handedness reversal. Morphologically, asymmetry was first detected in megalopa larvae where the right propodus was significantly larger than the left, as was the canine at the base of the right dactylus. Presumably, the rate of chelagenesis differed between the left and right chelae. With these morphological features, the right chela functioned as a crusher. The crusher exerted a closing force two to three times that of the cutter. With loss of the right crusher, the left chela was bigger than the regenerated right chela and was converted to the crusher. In contrast, the performance of the regenerated right chela deteriorated compared to that of the original right crusher, and exertion of full closing force was inhibited by the more active left chela. Furthermore, crabs with two crusher chelae did not clearly show handedness. A decrease in size and performance of the regenerated right chela can be explained by a default program hypothesis. In conclusion, a difference in the chelagenesis rate results in bilateral asymmetry of the two chelipeds, and then handedness is generated by neural regulation in the thoracic ganglion innervating these claws. Since handedness is reversed after autotomy, the thoracic ganglion would not be lateralized in Gazami crabs. A default program hypothesis is proposed to explain the ontogeny of bilateral chela asymmetry and handedness reversal.
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