Environmental modulation of the onset of air breathing and survival of Betta splendens and Trichopodus trichopterus

Abstract

The effect of hypoxia on air-breathing onset and survival was determined in larvae of the air-breathing fishes, the three spot gourami Trichopodus trichopterus and the Siamese fighting fish Betta splendens. Larvae were exposed continuously or intermittently (12 h nightly) to an oxygen partial pressure (PO2 ) of 20, 17 and 14 kPa from 1 to 40 days post-fertilization (dpf). Survival and onset of air breathing were measured daily. Continuous normoxic conditions produced a larval survival rate of 65-75% for B. splendens and 15-30% for T. trichopterus, but all larvae of both species died at 9 dpf in continuous hypoxia conditions. Larvae under intermittent (nocturnal) hypoxia showed a 15% elevated survival rate in both species. The same conditions altered the onset of air breathing, advancing onset by 4 days in B. splendens and delaying onset by 9 days in T. trichopterus. These interspecific differences were attributed to air-breathing characteristics: B. splendens was a non-obligatory air breather after 36 dpf, whereas T. trichopterus was an obligatory air breather after 32 dpf.

Hypoxia‐induced developmental plasticity of the gills and air‐breathing organ of Trichopodus trichopterus

“…trichopterus to be slightly less sensitive to chronic hypoxia in early larval life than reported for this species in an independent study. Mendez‐Sanchez & Burggren () found that larvae experienced significant mortality below c . 15% chronic hypoxia, although mortality was reduced in the intermittent hypoxia group.…”

“…15% chronic hypoxia, although mortality was reduced in the intermittent hypoxia group. Mendez‐Sanchez & Burggren () conducted experiments on survival and onset of air breathing using larvae from the same clutch, as preliminary studies had found significant intra‐clutch variation for the onset of air breathing in the larval Siamese fighting fish Betta splendens Regan 1910. In contrast, this study used larvae from several different clutches and parents.…”

Challenges and opportunities in developmental integrative physiology

“…Indeed, these investigations tend to focus on the underlying mechanisms to explain phenotypic plasticity and especially developmental phenotypic plasticity (West-Eberhard, 2003; de Jong and Leyser, 2012; Kelly et al, 2012; Snell-Rood, 2012; Forsman, 2014; Woods, 2014). Such studies almost invariably spill over into considerations of fetal programming (Symonds et al, 2007; Nijland et al, 2008; Vickers, 2011) and heterokairy (Spicer and Burggren, 2003; Spicer and Rundle, 2007; Spicer et al, 2011; Mendez-Sanchez and Burggren, 2014). Transgenerational epigenetic studies per se are more inclined to provide insights into the influence of rapid phenotypic adjustments — so-called “emergency phenotypes” (G. Claireaux, unpubl.).…”

Cardio-respiratory development in bird embryos: new insights from a venerable animal model

“…Additionally, development of rivulid annual killifish, as well as their diapause state, can reflect elements of heterokairy (Varela-Lasheras and Van Dooren, 2014). Collectively, these data on fishes show not only developmental phenotypic plasticity and heterokairy, specifically, but also show that a complex behavior that can be moved back and forth in the normal developmental timetable must be supported by equally complex morphology and physiology (Warkentin, 2011;Mendez-Sanchez and Burggren, 2014). Despite their promise as experimental models, avian embryos have rarely been examined in the context of heterokairy.…”