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Amphioctopus fangsiao is an important fishery resource in northern coastal China, and there is an interest to develop its commercial cultivation under controlled conditions. In this study, we describe the embryonic development of A. fangsiao from eggs to hatchlings, focusing on the formation of the mantle, eyes and arms. Results indicate that this species has several favorable characteristics for aquaculture, such as a short incubation period and a large body size of hatchlings. During the organogenesis, the primordia of organs, including the optic sac and arm crown, first appeared at stage VIII; then the mantle primordium, eye primordia and arm crown become visible at stage IX-X, and the rudiment of embryo (mantle, eyes and arms) was completely outlined at stage XI. The retinal pigment appeared yellowish at stage X-XI and gradually deepens in pigmentation in the subsequent stages, turning from yellowish to yellow, red, dark-red and eventually black. At stage XV, the primary lid fold, with only a circular opening remaining, covered the eye, and the dorsal ocular edge did not reach the ventral side until hatching (day 1-7). Afterwards, about 24 days after hatching, both the dorsal and ventral sides of eyelid could contract freely, with an oval and elongate slit remaining that was a miniature version of the adult morphology. The chromatophores and ink sac appeared at stage XIV. These observations provide a foundation for the reproductive biology and aquaculture of A. fangsiao and also offer an important reference for the research of embryonic development in related species.

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Parasitic diseases and other abnormalities play critical roles in causing morbidity in the majority of Cephalopoda. However, to date, reports of cephalopod diseases from Asia are scarce and lack detailed information on the description of specific characters. This paper presents a brief overview of various pathogens and produced diseases in Asian cephalopods, including coccidiosis by Aggregata, Anisakiasis, infection by the copepods Octopicola, and other abnormalities such as edema and broken skin. The coccidian Aggregata sp. that infects the definitive host Amphioctopus fangsiao is a heteroxenous parasite transmitted through the food web. Anisakids play an important role in Asia as parasitic disease for cephalopods and it is even transmitted to humans. Concerning the infection by copepods, Octopicola sp. is the only species of the family Octopicolidae reported from North Pacific waters. Other abnormalities like edema or broken skin may have been the result of bacterial infections, so that abnormalities could cause the degeneration and death observed in A. fangsiao.