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Research articles

ScienceAsia 48 (2022): 393-398 |doi: 10.2306/scienceasia1513-1874.2022.057

Embryonic development and external morphology of Amphioctopus aegina (Gray, 1849) (Cephalopoda: Octopodidae) in Thailand

Pawida Prasopsook, Charuay Sukhsangchan*, Napakhwan Whanphetch

ABSTRACT:     The embryonic development, morphology of the eggs, and newly hatched paralarvae of the sandbird octopuses (Amphioctopus aegina) were described using laboratory-reared specimens. Mature octopuses were collected from an artisanal fishery at Baan Salakeaw, Baan Phe District, Rayong Province, Thailand. The spawned eggs were examined. The non-adhesive eggs were attached to a string to form a cluster, and the average egg size was 2.64?0.13 mm in length and 0.94?0.06 mm in width. Females brooded the eggs in their arms until hatching. The embryonic development period was divided into 27 stages. The first embryo inversion occurred at stage 11, and primordia of major body parts, such as the arms, head, and mantle, also appeared. Eyespots appeared at stage 12, chromatophores appeared on the ventral side at stage 18 and on the dorsal side at stage 19, and the external yolk sac decreased in size until it disappeared at stage 27 (hatching stage). The paralarvae hatched after 18?22 days at 28.0 ?C and swam to the surface. The average total length of paralarvae was 3.40?0.24 mm. The paralarvae had a stubby oval shape mantle. Their arms were subequal in length with 5 suckers arranged in a single row per arm, and the eyes became conspicuous. The dorsal side of the head had 2?3 rows of large reddish brown chromatophores with 4 chromatophores in each row. On the funnel, there were 5 chromatophores in two rows each with three and two chromatophores. A single row of chromatophores occurred on the ventral mantle margin.

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a Department of Marine Science, Faculty of Fisheries, Kasetsart University, Bangkok 10900 Thailand

* Corresponding author, E-mail: ffiscrs@ku.ac.th

Received 12 Jul 2021, Accepted 28 Dec 2021