Promotion of initial swim bladder inflation and effect of initial inflation failure on skeletal malformation in cultured seven-band grouperHyporthodus septemfasciatus(Thunberg)

Abstract

The effects of the removal of the oily surface film on initial swim bladder inflation and survival in cultured seven‐band grouper Hyporthodus septemfasciatus were investigated during the larval stage. Additionally, the relationship between swim bladder inflation failure and malformations in later stages was examined. To explore promotion conditions for inflation, duplicate experiments were conducted under three different water surface conditions: removal of the oily surface film (ROF group), covering the water surface with an oil film (COF group), and sealing the water surface with liquid paraffin (SLP group). Larval swim bladder inflation was first observed 14 days after hatching (DAH) in the ROF group; thereafter, swim bladder inflation rates increased to 11.1% and 38.7% until the end of the experiments. This indicates that initial swim bladder inflation occurs at the pre‐flexion stage in larval development. Conversely, bladder inflation was rarely observed in the COF or SLP groups, indicating the promotional effect of surface film removal on larval swim bladder inflation and suggesting that gulping atmospheric air is necessary for initial inflation. Although larval water surface death occurred frequently in the ROF group, no significant difference existed in any group between the survival rates at 10 DAH and at the end of the experiment. The incidence rate of spinal curvature and deformation of the centra was significantly higher in individuals without initial swim bladder inflation, and these malformations mainly occurred in the caudal vertebra. Therefore, the removal of the oily surface film promotes initial swim bladder inflation and reduces larval malformations.

Osteological development and deformities in hatchery-reared longtooth grouper (Epinephelus bruneus ): Vertebral column, dorsal-fin supports and caudal-fin skeleton

“…Previous studies on various species, including longtooth grouper, have correlated lordosis with lack of a functional swim bladder (Chatain, ; Hayashida et al, ; Jacquemond, ; Kitajima, ; Kitajima et al, ; Nagano et al, ; Tsuji et al, ; Uji, ), as observed in the present study. In those reports, the position of lordosis was mostly allocated to two regions: (a) at positions between the prehaemal and haemal vertebrae (such as found in red seabream (Kitajima, ; Kitajima, Iwamoto, & Matsukiyo, ), European seabass ( Dicentrarchus labrax ) and gilthead bream (Chatain, ) or (b) on the haemal vertebrae [such as found in black seabream ( Acanthopagrus schlegelii ; Kitajima, ), Japanese seabass ( Lateolabrax japonicus ; Hayashida et al, ) and Eurasian perch ( Perca fluviatilis ; Jacquemond, )].…”

“…In those reports, the position of lordosis was mostly allocated to two regions: (a) at positions between the prehaemal and haemal vertebrae (such as found in red seabream (Kitajima, ; Kitajima, Iwamoto, & Matsukiyo, ), European seabass ( Dicentrarchus labrax ) and gilthead bream (Chatain, ) or (b) on the haemal vertebrae [such as found in black seabream ( Acanthopagrus schlegelii ; Kitajima, ), Japanese seabass ( Lateolabrax japonicus ; Hayashida et al, ) and Eurasian perch ( Perca fluviatilis ; Jacquemond, )]. However, two studies of sevenband grouper ( E. septemfasciatus ) differed in the reported position of lordosis: Nagano et al () found the condition at V8–11 (between the prehaemal and haemal vertebrae), whereas Tsuji et al () reported the condition at V15–18 (at the haemal vertebrae). This suggests that the position of lordosis may be influenced by various factors, including rearing conditions and swim bladder inflation.…”

“…This suggests that the position of lordosis may be influenced by various factors, including rearing conditions and swim bladder inflation. Some reports suggest that lordosis is discriminated as haemal and prehaemal lordosis and that the former is induced by active muscular activity from intensive swimming effort whether or not the swim bladder is inflated (Chatain, ; Kihara, Ogata, Kawano, Kubota, & Yamaguchi, ; Sfakianakis et al, ; Tsuji et al, ). In contrast, in the present study, lordosis in longtooth grouper with a noninflated swim bladder was mostly observed at V1–4 (the prehaemal vertebrae nearest the cranium) instead of the mid‐part or posterior part of the body.…”

“…Some information is available on the skeletal development of the dorsal‐ and pelvic‐fin spines of longtooth grouper (Sawada et al, ), but there is no published information on the osteological development of the vertebral column, caudal‐fin skeleton or dorsal‐fin supports. Furthermore, it is well known that swim bladder inflation can strongly influence the occurrence of deformities such as spinal curvature (i.e., lordosis or kyphosis) and saddleback‐like syndrome in many fish species, including groupers (Boglione et al, ; Chatain, ; Grotmol, Kryvi, & Totland, ; Hayashida, Tsukashima, Matsukiyo, & Kitajima, ; Iwasaki, Teruya, Mizuta, & Hamasaki, ; Jacquemond, ; Kitajima, ; Kitajima, Tsukashima, Fujita, Watanabe, & Yone, ; Nagano et al, ; Tsuji et al, ; Uji, ). Hence, the influence of swim bladder inflation on deformities in longtooth grouper should be studied.…”

Teratogenic effects of isolated and combined short-term hypercapnia and hypoxia on red sea bream (Pagrus major) embryos

“…Malformations decrease production efficiency in finfish aquaculture due to delayed growth, poor survival, disposal of malformed fish unsuitable for sale and a decline in the price of harvest. Vertebral anomalies are the major malformations in fish (Boglione et al, ; Fjelldal, Hansen, & Berg, ; Lewis‐McCrea & Lall, ; Tsuji et al, , etc. ), and it is beneficial to elucidate their causes and to establish preventive methods.…”