SEDAO 1:57-73 (2014)  -  DOI: https://doi.org/10.3354/sedao00007

Eyestalk ablation affects larval morphogenesis in the swimming crab Portunus trituberculatus during metamorphosis into megalopae

Shigeki Dan1, Takaaki Kaneko2, Satoshi Takeshima3, Masakazu Ashidate1, Katsuyuki Hamasaki2,*

1Tamano Laboratory, National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Tamano, Okayama 706-0002, Japan
2Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Konan, Minato, Tokyo 108-8477, Japan
3Hakatajima Laboratory, National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Imabari, Ehime 794-2305, Japan
*Corresponding author:

ABSTRACT: To understand the role of the eyestalk neurosecretory system in regulation of larval morphogenesis, we performed eyestalk ablation on swimming crab Portunus trituberculatus larvae at various times during zoeal development. We measured the length of the chelae and pleopods, which become enlarged during development, and the dorsal spine and telson furcae, which are resorbed during metamorphosis in the final (fourth) stage zoeae and subsequent larval stages, including a supernumerary fifth stage zoeae and megalopae (fifth-instar larvae). The length of the chela and pleopod of fourth stage zoeae decreased when the bilateral eyestalks were ablated earlier during development. Eyestalk ablation had little effect on the zoeal dorsal spine and furcae. In fifth-instar larvae, the effects of eyestalk ablation changed radically depending on the time when the ablation was performed, and a critical period during the premoult of the third zoeal stage was identified. Ablation before this period caused retention of a large dorsal spine and furcae and resulted in moult to the supernumerary fifth zoeal stage. Ablation after this period allowed larvae to metamorphose into normal megalopae. Ablation during this period resulted in megalopae with immature morphology, whereby the larvae retained small dorsal spines and telson furcae. The results demonstrated that the eyestalk neurosecretory system most likely regulates larval morphogenesis during metamorphosis in 2 ways: the morphogenesis of body parts that are enlarged are continuously controlled throughout the zoeal stages, whereas the resorption of body parts is controlled instantaneously at a critical point during the premoult of the third zoeal stage.


KEY WORDS: Larval morphogenesis · Larval metamorphosis · Morphological abnormality · Mass mortality in seed production · Moult-death syndrome


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Cite this article as: Dan S, Kaneko T, Takeshima S, Ashidate M, Hamasaki K (2014) Eyestalk ablation affects larval morphogenesis in the swimming crab Portunus trituberculatus during metamorphosis into megalopae. Sex Early Dev Aquat Org 1:57-73. https://doi.org/10.3354/sedao00007

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