Ontogenetic changes in tolerance to acute ammonia exposure and associated gill histological alterations during early juvenile development of the blue swimmer crab, Portunus pelagicus

Romano, Nicholas, and Zeng, Chaoshu (2007) Ontogenetic changes in tolerance to acute ammonia exposure and associated gill histological alterations during early juvenile development of the blue swimmer crab, Portunus pelagicus. Aquaculture, 266 (1-4). pp. 246-254.

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The current study was performed to determine the LC50 values through early juvenile ontogeny of the blue swimmer crab Portunus pelagicus, which forms an important fisheries industry and is currently a targeted species throughout the Indo-Pacific region. Additionally, through examination of the gills we sought to investigate cause of death as well as explaining ontogenetic changes in tolerance to acute ammonia-N exposure. The juvenile stages tested were crab one (C1) stage (mean weight 0.002 g), crab three (C3) stage (mean weight 0.028 g), crab five (C5) stage (mean weight 0.187 g) and crab seven (C7) stage (mean weight 0.732 g). The C1 stage was defined as the first molt from the megalopa larvae stage to the first crab stage. The developmental duration from the C1 to C7 stage took approximately 40 days. When the desired stage was reached the crabs were randomly selected and exposed to 5, 10, 20, 40, 60, 80, 100 mg/l ammonia-N and a control (no ammonia-N added) for 96-h according to the "static renewal method". For each juvenile experiment, a total of 30 crabs, each acting as a replicate, were tested at each ammonia-N treatment and control at a salinity of 30‰, temperature of 28°C and pH of 8.1.

The results demonstrate that ammonia-N tolerance significantly (p < 0.01) increases with the juvenile ontogenetic development of P. pelagicus. The 96-h LC50 (mg/l) values of total ammonia-N were 23.10 (1.65 NH3–N mg/l), 25.23 (1.80 NH3–N mg/l), 37.43 (2.67 NH3–N mg/l) and 50.65 (3.62 NH3–N mg/l) for the C1, C3, C5 and C7 crabs respectively, showing an over two-fold increase in ammonia-N tolerance from the C1 to C7 crab stage. Furthermore, in comparison to other crustacean species, P. pelagicus early juveniles exhibit a considerably higher tolerance to ammonia-N.

The histological results show that following an ammonia-N exposure concentration of 5 mg/l, localised infiltration of haemocytes and epithelial changes of the lamellae on the anterior gills of the C1 crabs were observed. However, at the same ammonia-N concentration, no obvious gill histopathological changes were observed for the C3, C5 or C7 crabs. In general, the severity of morphological and physiological changes to the gill lamellae, including extensive infiltration of haemocytes, necrosis, epithelial changes, disrupted pillar cells and lamellae collapse, increased with increasing ammonia-N concentrations for all crab stages. However, at the same ammonia-N concentration, the severity of the changes to the gill lamellae were less with more developed crabs.

Item ID: 2468
Item Type: Article (Research - C1)
ISSN: 1873-5622
Keywords: acute ammonia toxicity; early ontogeny; gill histology; Portunus pelagicus; LC50
Date Deposited: 21 Jul 2009 01:32
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830199 Fisheries - Aquaculture not elsewhere classified @ 100%
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