Adverse effects of cypermethrin on golden apple snails (Pomacea canaliculata) and their eggs, and application of Acetylcholinesterase (AChE) as biomarker

This study aimed to evaluate the effects of cypermethrin on hatching rate of golden apple snail eggs, mortality rate of the golden apple snails, and acetylcholinesterase (AChE) expression applied as a bio-indicator. The results showed that cypermethrin concentration did not affect hatching rate or development of the eggs and larvae in comparison with the control. The mortality rate depended on the exposure concentration. Median lethal concentration (LC50) (95% confidence) at 96 h was approximately 8.99 (8.93-9.06). The concentration of cypermethrin had an effect on AChE expression in both the snails and their eggs. The molecular weight of AChE found was 71 kDa, as studied by SDS-PAGE and Western blot techniques. The ELISA technique revealed that AChE contents in both the snails and their eggs were significantly different from the control (p <0.05). Based on our results, AChE could be applied to assess cypermethrin exposure in the snails and their eggs, in order to plan contamination management of such pesticides in the snails and reduce the risks to consumers

Growth and competitions of the Australian red-claw crayfish, Cherax quadricarinatus (von Martens, 1868) in Thailand: the experimental approaches

The Australian red-claw crayfish (RCC) Cherax quadricarinatus (von Martens 1868) (Crustacea: Decapoda: Parastacidae) has been introduced and promoted for freshwater aquaculture in many countries including Thailand. This study i) evaluates the growth performance of RCC in near-natural conditions relative to captive conditions and ii) investigates how successfully RCC can compete with a trophically and functionally analogous native species. Growth of RCC was compared among two aquaculture systems (concrete tank and earthen pond) and a treatment with simulated natural conditions. After 12 months of rearing, total length and weight were greatest in the earthen pond and poorest in the near-natural treatment, with significant differences in total length between the near-natural treatment and the two culture systems. Length-weight relationships showed that the RCC had positive allometry in the culture systems but negative allometry in the near-natural treatment. Competition was evaluated by means of a biotic resistance test and an additive–substitutive experiment between RCC and the native freshwater crab Esanthelphusa dugasti (Rathbun, 1902) (Crustacea: Decapoda: Gecarcinucidae). Specific growth rates after 90 days of the experiments suggest that the crab inhibited growth of RCC. This implies that the invasion of RCC in Thai waters could be limited by competition from resident freshwater crabs