Characterization of a γ-aminobutyrate type A receptor-associated protein gene, which is involved in the response of Portunus trituberculatus to CO₂ -induced ocean acidification

Abstract

The γ‐aminobutyrate type A receptor‐associated protein (GABARAP) is a ubiquitin‐like modifier implicated in membrane trafficking and fusion events involving the γ‐aminobutyrate type A receptor, autophagy and apoptosis. In this study, the gene encoding GABARAP was cloned from swimming crab Portunus trituberculatus (PtGABARAP) based on the expression sequence tag (EST). The full‐length cDNA of 664 bp includes a 5′ untranslated region (UTR) of 87 bp, a 3′ UTR of 223 bp with a poly(A) tail, and an open reading frame (ORF) of 354 bp encoding a polypeptide of 117 amino acids with a predicted molecular weight of 13.96 kDa. The deduced amino acid sequence shares high similarity (93%–100%) with GABARAPs from other species and includes a conserved Atg8 domain. In a phylogenetic analysis PtGABARAP clustered with GABARAPs from other species, and more widely with other GABARAP family proteins. The impact of elevated ocean acidification (OA) on P. trituberculatus behaviours was investigated, and real‐time RT‐PCR revealed that PtGABARAP expression was up‐regulated after OA exposure. Ocean acidification also caused crabs anxiety‐like behaviours, like the shoal average speed increase, preference for dark environment (scototaxis) and fast exploration. The results indicated that GABARAP might be involved in the interactions of GABAA receptors and elevated‐CO2 seawater.

Effects of Elevated pCO2 on the Survival and Growth of Portunus trituberculatus

“…Ocean acidification has comprehensive effects on the growth and development ( Long et al, 2013a ), physiology and metabolism ( Maus et al, 2018 ), morphology ( Ren et al, 2017 ), and behavior of a variety of marine crabs ( Wang et al, 2018 ). However, the effects of OA have been reported only on the carapace morphology and behavior of juvenile P. trituberculatus ( Ren et al, 2017 , 2018 ). To the best of our knowledge, this is the first study to reveal the comprehensive effects of OA exposure on P. trituberculatus .…”

“…Three experimental OA groups were designed with seawater p CO 2 at current or predicted future levels: the ambient p CO 2 was 380 μatm (designated the 380 group), 750 μatm (designated the 750 group) was used to represent the scenario at the end of this century and 1500 μatm (designated the 1500 group) was used to represent the scenario in c. 2200 ( Revi et al, 2014 ; Gattuso et al, 2015 ). To build the experimental systems, a simulated ocean acidification system (CN: ZL201520071087.1) ( Ren et al, 2018 ) and an incubation system that was partially derived from the experimental system of Wang et al (2018) were used. For each group, the incubation system per group consisted of a mixing tank (500 L) and three individual culture tanks (300 L), and seawater was recirculated and purified by using a water purification header tank connected to the culture tanks (200 L).…”

“…The swimming crab, Portunus trituberculatus (Crustacea, Decapoda, Brachyura), is a widely cultured and consumed species in China with a yield of 617,540 tons in 2017 ( China Fishery Statistical Yearbook, 2018 ). Our previous studies have shown that elevated p CO 2 (750 and 1500 μatm) has significant effects on the carapace of juvenile swimming crabs (e.g., a simplified arrangement of spinules, a reduced thickness, and an increased chitin content) ( Ren et al, 2017 ) and their behavior (e.g., an increase in shoal average speed, a preference for dark environments and fast exploration) ( Ren et al, 2018 ). Furthermore, previous studies have reported that OA can induce oxidative stress ( Wang et al, 2009 ; Menu-Courey et al, 2019 ) and suppress immunity ( Hernroth et al, 2012 ) in other crustaceans.…”

Toward a Mechanistic Understanding of Marine Invertebrate Behavior at Elevated CO2

“…A light/dark test on swimming crabs Portunus trituberculatus exposed to control (485 µatm pCO 2 ) or elevated (750 µatm and 1,500 µatm pCO 2 ) CO 2 was the first to assess the impact of elevated CO 2 on anxiety-like behavior in a marine invertebrate. Crabs exposed to elevated CO 2 levels spent significantly more time in the dark zone (Ren et al, 2018).…”

Neural effects of elevated CO2 in fish may be amplified by a vicious cycle

“…Since the first reports of behavioural disturbances in fish exposed to elevated CO 2 (hypercapnia) (Munday et al ., 2009), a steady stream of reports has shown an array of behavioural and sensory functions being altered by environmental hypercapnia in aquatic animals (Nagelkerken and Munday, 2016; Cattano et al ., 2018). These impairments, which affect olfactory preferences (by reversing them), lateralization, hearing, vision, learning, physical activity and boldness, occur at elevated CO 2 levels projected for the next 50 to 100 years and are exhibited not only in fish but also in some invertebrates, including molluscs and crustaceans (Watson et al , 2014; Jellison et al, 2016; Ren et al , 2018). However, there is also a clear intraspecific variation in the response to elevated CO 2 , as we will discuss later.…”