Developmental biology of medaka fish (Oryzias latipes) exposed to alkalinity stress

Abstract

Alkalinity stress is common in cultured aquatic animals and considered to be one of the major stress factors for fishes when they are transferred to saline-alkali waters. To evaluate potential effects of alkalinity on the developmental biology of Oryzias latipes, fertilized eggs, larvae and breeding fish were exposed to different carbonate alkalinity concentrations of 1.5-64.5 meq l )1 , for 9, 120, and 60 days, respectively. The mortality of embryos significantly increased when exposed to the high concentrations (16.5-64.5 meq l )1 ). Although more than 50% of survived embryos hatched in 16.5 and 31.4 meq l )1 concentrations of carbonate alkalinity, most were not able to swim up after hatching. Morphological abnormalities such as coagulated embryos, halted embryo development, and hatching failure were observed at stages 15, 29-33 and 38 in high concentrations (31.4, 64.5 meq l )1 ). Almost all larvae in 16.5 and 31.4 meq l )1 treatments died 70 d post-hatch. Growth of juveniles exposed to carbonate alkalinity of 5.3 and 8.8 meq l )1 was not significantly different at 70 d and 120 d post-hatch. The number of eggs released by breeders, the fertilization rate and the hatching rate of eggs were significantly lower in the 31.4 meq l )1 treatment than in other treatments. Although medaka are capable of surviving in high alkalinities (31.4, 64.5 meq l )1 ) for an extended period of time, these conditions are stressful to the fish, especially at the embryonic and reproductive stages.

Acute Exposure to Key Aquaculture Environmental Stressors Impaired the Aerobic Metabolism of Carassius auratus gibelio

“…The relative increase in peak post-prandial MO 2 for C. auratus gibelio exposed to high pH reached a maximum of 2.2 times higher than SMR, along with extremely narrow AS, which may result in difficulty getting food and a low ingestion rate. This is consistent with our findings about the growth performance of fish in alkaline water [31]. These findings give us some hint that extra oxygen should be provided when farming the fish in high pH water, especially during the feeding and ingestion period.…”

Carbonic anhydrase 2-like and Na+-K+-ATPase α gene expression in medaka (Oryzias latipes) under carbonate alkalinity stress

“…Our present and former studies (Yao et al 2010(Yao et al , 2012 have revealed that medaka is an ideal model organism for studying the effects of saline-alkaline stress in fish and have led to establishment of developmental biology and gene expression protocols for continuing this line of research. Additionally, medaka is aboriginal in some saline-alkaline lakes in China (Zhao 2010) presenting an opportunity for additional comparative studies utilizing medaka and other native species living in these special water bodies, which should aid in revealing the underlying saline-alkaline adaptation mechanisms.…”

“…Six carbonate alkalinity concentrations were tested as shown in Table 1. The selection of alkalinity concentrations was based on a former study by Yao et al (2010). In order to maximize our opportunity for elucidating the key components involved in mechanistic responses for regulating alkalinity stress, the maximum alkaline concentration (30.4 mM) that medaka could survival for a long period time was set as the acute exposure concentration and highest chronic exposure concentration.…”

“…Despite our basic understanding of the developmental responses of fish to alkaline stress (Yao et al 2010), the cellular and molecular mechanisms for coping with alkaline stress in the gill and kidney remain uncertain. Our previous genome-wide study on medaka showed a potential acid-base regulatory function of CA in response to carbonate alkalinity stress (Yao et al 2012).…”

Comparative transcriptome analysis of Nile tilapia (Oreochromis niloticus) in response to alkalinity stress

“…In contrast, alkalinity causes several abnormal behavioral, physiological, and biochemical reactions and even quick death in freshwater teleosts exposed to alkaline water (Yao et al, 2010). Freshwater fishes can endure alkalinity up to a certain extent (pH close to 8) depending on the species or individuals (Lei et al, 1985).…”