Adaptive responses to high environmental ammonia in European

Adaptive responses to high environm ental am m o nia in European sea
bass acclimated to d iffe re n t salinities
Dasan A n to ny Franklin, Rindra Rasoloniriana, A m it Kumar Sinha, Ronny Blust and Gudrun De Boeck
Laboratory fo r Ecophysiology, Biochem istry and Toxicology, U niversity o f Antw erp,
Groenenborgerlaan 171, 2020 A ntw erp, Belgium
E-m ail: a d a sa n @ vu b .a c.b e
The European sea bass (D icentrarchus labrax) is increasingly the m ost im p o rta n t marine species in
European aquaculture, ow ing to increased fa rm ing o f the marine fish, especially in the
M editerranean region. European sea bass belong to the euryhaline species o f fish, which im plies
th a t they are capable o f living in environm ents o f wide range salinity. Farmers in the Mediterranean
region are rearing the fish in sea cages and land-based systems, which greatly augm ent am m onia
buildup. This e xperim ental study w ill seek to establish the a da pta b ility o f the fish to High
Environm ental A m m onia (HEA), at d iffe re n t am bient salinities.
The researchers w ill expose European sea bass acclim ated to HEA (20m g.l '), and feed at up to 2% o f
body w eight, to d iffe re n t salinities (32 °/oo, 2 0 °/oo, 10 °/00 and 2 .5 °/oo) in d iffe re n t e xperim ental tanks.
The adaptations o f the fish in the e xperim ental tanks w ill be observed after Oh (control) 1 2 h, 48h,
84h and 180h intervals. A d ditio na lly, am m onia excretion rate and am m onia q u o tie n t (AQ) w ill be
taken at each interval to help draw conclusions about the fis h ’s adaptive responses to d iffe re n t
am bient salinities. A fte r each interval, fish w ill be removed fro m the ta nk and blood drawn from
them fo r serology. A t the end o f the experim ent, the fishes w ill be dissected and liver, brain, w hite
muscle, g ili and kidney tissues obtained fo r analysis. Analysis w ill involve m easuring o f plasma and
muscle am m onia accum ulation, plasma lactate, liver and muscle glycogen, cortiso l and energy
budget, AQ and Lipid and protein content. It is expected th a t fish would suffer m arked disturbance
o f norm al fu n ctio n s fo llo w in g prolonged exposure to HEA. A d ditio na lly, it is expected th a t am m onia
excretion by the fish w ould increase in an a tte m p t to m aintain the positive am m onia gradient.
However, the levels o f am m onia in plasma and muscles, lactate accum ulation in muscles and the
am m onia q u o tie n t are expected to m arkedly increase. The e xten t to which these changes are
observed w ill depend on salinity, since feeding is universal. High sa lin ity environm ents have been
shown to augm ent am m onia to x ic ity because it facilitates increased concentration o f the NH3
m oiety, which is solely responsible fo r am m onia to x ic ity , in aqueous amm onia. As such, these
changes, and even loss o f fu n ctio n , w ill be expected to be more severe in fish exposed to higher
salinities.
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