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Event Title

Posterior swim bladder inflation, Reduced

Key Event Overview

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AOPs Including This Key Event

AOP Name Event Type Essentiality
Deiodinase 2 inhibition leading to reduced young of year survival via posterior swim bladder inflation KE
Deiodinase 1 inhibition leading to reduced young of year survival via posterior swim bladder inflation KE

Taxonomic Applicability

Name Scientific Name Evidence Links
zebrafish Danio rerio NCBI
fathead minnow Pimephales promelas NCBI

Level of Biological Organization

Biological Organization

How this Key Event works

The swim bladder of bony fish is evolutionary homologous to the lung (Zheng et al., 2011). The teleost swim bladder is a gas-filled structure that consists of two chambers, the posterior and anterior chamber. In zebrafish, the posterior chamber inflates around 96 h post fertilization (hpf) which is 2 days post hatch, and the anterior chamber inflates around 21 dpf. In fathead minnow, the posterior and anterior chamber inflate around 6 and 14 dpf respectively.

The posterior chamber is formed from a bud originating from the foregut endoderm (Winata et al., 2009). The posterior chamber operates as a hydrostatic organ. The volume of gas in the adult swim bladder is continuously adjusted to regulate body density and buoyancy.

Many amphibians and frogs go through an embryo-larval transition phase marking the switch from endogenous feeding (from the yolk) to exogenous feeding. In zebrafish, embryonic-to-larval transition takes place around 96 hours post fertilization (hpf). As in amphibians, the transition between the different developmental phases includes maturation and inflation of the swim bladder (Liu and Chan, 2002).

Reduced inflation of the posterior chamber may manifest itself as either a complete failure to inflate the chamber or a reduced size of the chamber.

How it is Measured or Detected

In several fish species, inflation of the posterior chamber can easily be observed using a stereomicroscope because the larvae are still transparent during those early developmental stages. This is for example true for zebrafish and fathead minnow. Posterior chamber size can then be measured based on photographs with a calibrator.

Evidence Supporting Taxonomic Applicability

The evidence for impaired posterior chamber of the swim bladder currently comes from work on zebrafish and fathead minnow.


Zheng, W., Wang, Z., Collins, J.E., Andrews, R.M., Stemple, D., Gong, Z., 2011.Comparative transcriptome analyses indicate molecular homology of zebrafishswimbladder and mammalian lung. PLoS One 6, http://dx.doi.org/10.1371/journal.pone.0024019.

Winata, C.L., Korzh, S., Kondrychyn, I., Zheng, W., Korzh, V., Gong, Z., 2009.Development of zebrafish swimbladder: the requirement of Hedgehogsignaling in specification and organization of the three tissue layers. Dev. Biol.331, 222–236, http://dx.doi.org/10.1016/j.ydbio.2009.04.035.

Liu, Y.W., Chan, W.K., 2002. Thyroid hormones are important for embryonic tolarval transitory phase in zebrafish. Differentiation 70, 36–45, http://dx.doi.org/10.1046/j.1432-0436.2002.700104.x.