Characterization of swim bladder non‐inflation (SBN) in angelfish, Pterophyllum scalare (Schultz), and the effect of exposure to methylene blue

Abstract

Failure to inflate the swim bladder is regarded a major obstacle in the rearing of many fish species. We present a study of swim bladder non-inflation (SBN) in angelfish, Pterophyllum scalare. A normal developing primordial swim bladder was first discernable at the end of the first day post-hatch (p.h.) as a cluster of epithelial cells with a central lumen, surrounded by presumably mesenchymal cells. Initial inflation occurred on the fourth day p.h. Prior to inflation the swim bladder epithelium consisted of an outer squamous and inner columnar layer. Cells of the inner layer were filled at their basal region with an amorphous material, which disappeared upon inflation. A pneumatic duct was absent, and larvae presented no need to reach the water surface for inflation, suggesting that angelfish are pure physoclists. A model for the role of the amorphous material in normal initial inflation is proposed. Abnormal swim bladders were apparent from the fourth day p.h., and methylene blue (MB) at a concentration of 5 ppm significantly increased the prevalence of SBN. Histologically, abnormal swim bladders in larvae hatched in 5 ppm MB could not be distinguished from those in fish raised under routine conditions (0.5 ppm MB). We suggest that MB may have a teratogenic effect in angelfish.

Comparative Transcriptome Analyses Indicate Molecular Homology of Zebrafish Swimbladder and Mammalian Lung

“…It has been shown by transmitted electron microscopy that the swimbladder epithelial cells are polarized even prior to inflation [36]. Tight junctions serve to form seals between epithelial cells, creating a selectively permeable barrier to intercellular diffusion.…”

Ahr2-dependence of PCB126 effects on the swim bladder in relation to expression of CYP1 and cox-2 genes in developing zebrafish

“…It will be interesting to determine whether there are similar effects of TCDD on swimbladder inflation and histology in physoclistous fish, in which the pneumatic duct is resorbed or absent, and in which inflation can occur by a different path. Problems with swimbladder inflation have been noted in physoclist fish (Perlberg et al , 2008) and further defining mechanisms of dioxin effect in zebrafish could yield insights that may be tested in those fish. The swimbladder in developing zebrafish may model the pathological changes and molecular basis for those changes occurring in lung, as well as in swimbladder of other fish.…”

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“…One of the most critical stages of larval development is considered to the first swelling of swim bladder (Blaxter 1992;Pelberg et al, 2008). Majority of larvae swell their swim bladders in developmental stage corresponding to the time of absorption of yolk sacs and onset of exogenous feeding (Doroshev and Cornacchia 1979;Battaglene and Talbot 1990).…”

“…The female of P. scalare generally lays up to 1000 eggs (Frank, 1984;Sieniawski, 2004;Cacho et al, 2006).Since this species was generally used for behavioral studies, behavior types are described in detail (Saxby et al, 2010). Previous studies on freshwater angelfish mainly concentrated on reproductive behavior (Degani et al, 1997;Cacho et al, 2006), spawning strategies (Cacho et al, 2007;Ortega-Salas et al, 2009), parental care (Degani et al, 1997;Cacho et al, 2006), growth performance (García-Ulloa and Gómez-Romero, 2005; Kasiri et al, 2011a), species-specific diseases (Perlberg et al, 2008;Murphyet al, 2009) and morphology (Groppelli et al, 2003).The literature on reproduction of freshwater angelfish is scare and limited to general descriptions.…”