Air‐breathing Behavior of the Jeju Fish Hoplerythrinus unitaeniatus in Amazonian Streams

Abstract

The breathing behavior of the jeju fish Hoplerythrinus unitaeniatus has been the focus of several studies in recent decades. Few of these studies, however, have described how the fish's air breathing functions in natural environments. We examined changes in the behavior of H. unitaeniatus during daily variations in the dissolved-oxygen (DO) content of the water in Amazonian streams. We recorded the mean time intervals between instances when the fish breached the water surface to take in atmospheric air and the variation in the DO concentrations. We also observed the number of individual fish that breached the surface together as well as their territory-forming behavior. We recorded the individual and collective anti-predator strategies in the presence of a potential predator, experimentally testing the capacity of H. unitaeniatus to recognize the shape of a predator. The results indicated that as the DO concentration decreased, the individuals of H. unitaeniatus tended to breach the water surface at shorter time intervals, which increased their exposure to predators. To minimize the risks from this longer exposure time, the species tends to adopt anti-predator strategies individually or as a group. In well-lit locations, the fish recognized the predator's silhouette, left their territory and took a longer time to return. We provide an original contribution to the understanding of the anti-predatory tactics of the species by describing the behavior of group formation and territory definition as a tool to maximize efficiency in the defense against predators, a behavior that until now was an unknown strategy for this species.Abstract in Portuguese is available in the online version of this article.

Spatiotemporal dynamics in a seasonal metacommunity structure is predictable: the case of floodplain‐fish communities

“…For instance, both Hoplerythrinus unitaeniatus and Hoplias malabaricus (species 23 and 24 in Fig. 2; Supplementary material Appendix 2) can tolerate hypoxic conditions by diffusing atmospheric oxygen into their bloodstream through a vascularised swim bladder and also perform overland movements using lateral body undulation (Kramer et al 1978, Lima‐Filho et al 2012). Such traits may explain why these species have relatively larger distributional ranges during the initial months of the rainy season when most patches are poorly connected and shallow.…”

Effects of the interannual variations in the flood pulse mediated by hypoxia tolerance: the case of the fish assemblages in the upper Parana River floodplain

“…As the ordination was influenced by species tolerant to hypoxia, these three assemblage attributes were either calculated for the entire fish assemblage, for this subset of species (herein named STH) and for all the other species excepting the STH, which were considered species intolerant to hypoxia (herein named SIH). STH were identified on the basis of reports in the literature (Junk et al, 1983;Graham, 1997;Silva et al, 1997;Almeida-Val et al, 1999;Fernandes et al, 1999;Graham, 1999;Soares et al, 2006;Casatti et al, 2009;Lima Filho et al, 2012), excluding those that may present reversible morphological adaptations for the uptake of atmospheric air (Scarabotti et al, 2011). We adopted these criteria because we were not able to detect any morphological differentiation that could be related to aquatic surface respiration in our samples, such as development of dermal lip protuberances (e.g., Winemiller, 1989;Scarabotti et al, 2011).…”

“…= degrees of freedom; SS = sum of squares; MS = mean square; F = ratio of variance between and within groups; p = probability of Type 1 error. (Petry et al, 2003a-b;Lima Filho et al, 2012). Reduced mobility to escape from sub-lethal hypoxia has been related to the nest-guarding behavior of fish, determining that not all members of the population escape the low oxygen disturbances (Breitburg, 1992).…”

“…Explained = proportion of variance explained. Filho et al, 2012). The identification of adaptive or behavioral strategies for hypoxia still requires empirical confirmation for most species and continuous or facultative air breathing are being described for some species of Characiformes, Siluriformes, Cyprinodontiformes, and Synbranchiformes (Graham, 1997;Scarabotti et al, 2011).…”

Air‐breathing ecology of Arapaima sp.: Conservation implications for an imperilled fish

“…Among continuous, obligate air‐breathing fishes, which require surface respiration for normal function, the way surface breathing occurs can also vary (Graham, 1997). Surfacing may occur rapidly to avoid predation threats, aggressively as a defence or warning mechanism, or synchronously as a means of communication (de Lima Filho et al, 2012). Higher energy demands required for vigorous or aggressive surfacing can be expected to require higher metabolism, and thus more frequent breathing.…”