Flocculation of Artemia induced by East Asian common Octopus octopus sinensis paralarvae under culture conditions

Shigeki Dan,Arata Takasugi,Hiraku Iwasaki,Shodai Shibasaki,Kazuhiro Yamashita,Katsuyuki Hamasaki

doi:10.1016/j.aqrep.2020.100330

Shigeki Dan, Arata Takasugi + Show 4 more

Open Access

https://doi.org/10.1016/j.aqrep.2020.100330

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Abstract

Artemia are potential food organisms for the mass culture of common octopus paralarvae but cause poor paralarval growth and mortality. To understand problems arising from Artemia use, we focused on Artemia flocculation in paralarval culture tanks; Artemia get caught up with each other, exhibit disrupted swimming, are deposited on the tank bottom and eventually die. To clarify whether paralarvae induce the flocculation of food organisms or not, we cultured newly hatched Artemia nauplii, 3-day-old metanauplii and decapod crustacean zoeae with or without paralarvae at different growth stages (weight). Flocculation occurred only when Artemia were cultured with paralarvae; metanauplii had a higher susceptibility for flocculation than nauplii. Flocculated Artemia proportion increased with increasing paralarval weight. Scanning electron microscopy revealed that flocculated metanauplii had deformed setules on their setae, with hook-shaped tips and adhesion of neighbouring tips, suggesting that flocculation may occur via a mechanism similar to the ‘hook-and-loop fastener’. As octopus paralarvae exhibit external digestion, digestive enzymes secreted by paralarvae may deform Artemia setules and result in flocculation. As flocculation did not occur when metanauplii were cultured in water in which paralarvae were cultured and then removed, causative enzymes were probably rapidly inactivated after secretion.

Highlights

The East Asian common octopus Octopus sinensis is distributed throughout the temperate western Pacific Ocean, primarily in the coastal waters of Japan, Korea and China (Amor et al, 2017; Gleadall, 2016)
To understand problems arising from Artemia use, we focused on Artemia flocculation in paralarval culture tanks; Artemia get caught up with each other, exhibit disrupted swimming, are deposited on the tank bottom and eventually die
In the groups in which food organisms were cultured with paralarvae, number of food consumption by a paralarva ranged from 12.9–23.6 individuals for natural decapod crustacean zoeae, from 18.3–31.4 individuals for newly hatched Artemia nauplii and 10.3–21.2 individuals for 3d-old Artemia metanauplii (Fig. 1a)

Summary

Introduction

The East Asian common octopus Octopus sinensis is distributed throughout the temperate western Pacific Ocean, primarily in the coastal waters of Japan, Korea and China (Amor et al, 2017; Gleadall, 2016). This species is an important fishery resource and has a high commercial value and high growth rate; it has been selected for aquaculture along with the Atlantic and Mediterranean common octopus Octopus vulgaris (Iglesias et al, 2007; Vaz-Pires et al, 2004). In terms of mass production of juveniles for aquaculture in an industrial scenario, securing a large number of crab zoeae is still a bottleneck because it is estimated that approximately 18 million zoeae are needed to produce 10,000 benthic juvenile octopuses (Dan et al, 2019)

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