Chlamydogobius Eremius Research Articles

Aggressive desert goby males also court more, independent of the physiological demands of salinity

Both between- and within-individual variation in behaviour can be important in determining mating opportunities and reproductive outcomes. Such behavioural variability can be induced by environmental conditions, especially if individuals vary in their tolerance levels or resource allocation patterns. We tested the effects of exposure to different salinity levels on male investment into two important components of mating success–intrasexual aggression and intersexual courtship–in a fish with a resource defence mating system, the desert goby, Chlamydogobius eremius. We found that males that were more aggressive to rivals also exhibited higher rates of courtship displays towards females. Contrary to predictions, this positive relationship, and the consistency of the two behaviours, were not affected by the salinity treatment, despite the physiological costs that high salinity imposes on the species. Moreover, over the entire data-set, there was only a marginally non-significant tendency for males to show higher levels of aggression and courtship in low, than high, salinity. The positive correlation between male aggression and courtship, independent of the physiological demands of the environment, suggests that males are not inclined to make contrasting resource investments into these two key reproductive behaviours. Instead, in this relatively euryhaline freshwater species, typical investment into current reproductive behaviours can occur under a range of different salinity conditions.

Rapid divergence of animal personality and syndrome structure across an arid-aquatic habitat matrix.

Intraspecific trait variation, including animal personalities and behavioural syndromes, affects how individual animals and populations interact with their environment. Within-species behavioural variation is widespread across animal taxa, which has substantial and unexplored implications for the ecological and evolutionary processes of animals. Accordingly, we sought to investigate individual behavioural characteristics in several populations of a desert-dwelling fish, the Australian desert goby (Chlamydogobius eremius). We reared first generation offspring in a common garden to compare non-ontogenic divergence in behavioural phenotypes between genetically interconnected populations from contrasting habitats (isolated groundwater springs versus hydrologically variable river waterholes). Despite the genetic connectedness of populations, fish had divergent bold-exploratory traits associated with their source habitat. This demonstrates divergence in risk-taking traits as a rapid phenotypic response to ecological pressures in arid aquatic habitats: neophilia may be suppressed by increased predation pressure and elevated by high intraspecific competition. Correlations between personality traits also differed between spring and river fish. River populations showed correlations between dispersal and novel environment behaviours, revealing an adaptive behavioural syndrome (related to dispersal and exploration) that was not found in spring populations. This illustrates the adaptive significance of heritable behavioural variation within and between populations, and their importance to animals persisting across contrasting habitats.

Boldness in extreme environments: temperament divergence in a desert-dwelling fish

Investigating how environmental factors influence within-species trait variability is critical to understanding the evolution and maintenance of individual behavioural differences (i.e. temperament or personality), and their integration into wider ecological theory. Populations of Australian desert gobies, Chlamydogobius eremius , from starkly contrasting aquatic environments in arid Australia were used to investigate how environmental differences influence temperament traits. Focusing on boldness and exploration, fish were assessed using novel environment, dispersal and novel food item assays under laboratory conditions. The results of these experiments were analysed for repeatability and for patterns of divergence within and between populations. We found consistent within-species differences in novel environment and novel food item assays, with refuge emergence and inspection latency of a novel food item both strongly repeatable behavioural axes. Although both traits can be considered measures of boldness, refuge emergence significantly diverged according to sex, while inspection latency was predicted by habitat differences. This suggests that multiple measures of boldness are diverging independently according to different ecological drivers. Specifically, we found that fish caught from environments without predators and with probable intense intraspecific competition are less active and bolder in a novel food item context. Further analysis demonstrated how extreme habitat differences are driving behavioural divergence on multiple axes, relating to boldness and dispersal behaviours. This provides valuable insights into how the environment and behaviour interact and how we define temperament traits, as well as highlighting the importance of studying temperament within a community ecology context.

The influence of recent social experience and physical environment on courtship and male aggression.

BackgroundSocial and environmental factors can profoundly impact an individual’s investment of resources into different components of reproduction. Such allocation trade-offs are expected to be amplified under challenging environmental conditions. To test these predictions, we used a desert-dwelling fish, the desert goby, Chlamydogobius eremius, to experimentally investigate the effects of prior social experience (with either a male or a female) on male investment in courtship and aggression under physiologically benign and challenging conditions (i.e., low versus high salinity).ResultsWe found that males maintained a higher level of aggression towards a rival after a recent encounter with a female, compared to an encounter with a male, under low (but not high) salinity. In contrast, male investment in courtship behaviour was unaffected by either salinity or social experience.ConclusionTogether, our results suggest that male investment in aggression and courtship displays can differ in their sensitivity to environmental conditions and that not all reproductive behaviours are similarly influenced by the same environmental context.

Dispersal in the desert: ephemeral water drives connectivity and phylogeography of an arid‐adapted fish

AbstractAimWe examine landscape processes shaping the range‐wide phylogeography of a dispersal‐limited, desert‐dwelling fish (the desert goby, Chlamydogobius eremius) in arid Australia.LocationSouth‐western Lake Eyre Basin, central Australia.MethodsWe obtained sequence data for the mitochondrial cytochrome b gene (n = 513 individuals) and nuclear genetic markers (51 allozyme loci; n ≥ 128 individuals) to investigate the phylogeographic relationships among 51 populations. Sampling spanned multiple habitat types (permanent desert springs, ephemeral rivers) and sub‐catchments, and the entire distribution of C. eremius and representatives of its sister species, Chlamydogobius japalpa. Phylogeographic analyses (genetic diversity, AMOVA, Tajima's D, WST, mismatch distribution) were used to explore the distribution and partitioning of mtDNA variation; principal coordinates analysis and neighbour‐joining tree networks were used to explore allozyme variation.ResultsThree main genetic groups exist across C. eremius/C. japalpa populations. The geographical distributions of these groups reflected the historical and current confluence point of major rivers in the region. Surprisingly, permanent desert springs did not contain higher genetic diversity than ephemeral rivers.Main conclusionsGenetic structuring of Chlamydogobius populations revealed unanticipated levels of connectivity, indicating that the ephemeral waters of Lake Eyre have allowed gene flow across drainage boundaries and large distances. Phylogeographic breaks reveal that connectivity relies on temporary surface water, while rapid temporal changes in diversity highlight flood‐driven dispersal as the main means of gene flow between localities and habitats. Dispersal pathways reveal that ecological context (life history and tolerance of extreme conditions) has played a key role in shaping observed patterns.

Habitat alteration influences male signalling effort in the Australian desert goby

Male sexual signals provide vital information about the quality of the signaller and can have important consequences for male repro -ductive success. Habitat changes, however, are expected to affect male sexual displays. An important question, therefore, is to deter -mine if and how such sexual displays are adjusted to changes in the signalling environment, especially in highly dynamic syst ems or those affected by human-induced environmental change. Desert, rivers, and springs are among the worldOs most threatened habitats. Many of these fragile water bodies are being overwhelmed by invasive weeds and excess primary productivity as an indirect res ult of human agricultural demand for freshwater. Here, we investigated the effects of altered habitat on the courtship effort of male des -ert gobies, Chlamydogobius eremius. Male courtship effort was observed in an environment that was either dominated by bulrush (Typha sp. ) or modiÞed by increased algal turbidity ( Scendesmus sp. ). We found that males that were exposed to an environment domi -nated by bulrush spent more time courting in these environments compared with environments that were unaltered. In contrast, males that were exposed to environments modiÞed by increased algal turbidity not only took longer to initiate courtship but also s pent less time courting females. These results suggest that different habitat alterations can have important consequences for the repr oductive behavior of affected organisms and, ultimately, the direction of sexual selection.

A recent predatory encounter influences male courtship in a desert-dwelling fish

Increased predation risk is one of the greatest costs associated with sexual signaling. Studies have shown that individuals often adjust their signaling behavior in the presence of predators with consequences for current reproductive opportunities. Predation risk, however, can vary over time and is rarely (if ever) constant. Despite this, surprisingly little is known about how recent exposure to a predator might influence an individual’s subsequent signaling behavior. Here, we set out to determine how a previous encounter with a piscivorous predator affected courtship behavior in a freshwater fish, the desert goby, Chlamydogobius eremius. We tested male courtship before and after manipulating their perception of risk. We found that male gobies previously exposed to a predatory fish, the spangled perch, Leiopotherapon unicolor, took longer to initiate courtship and subsequently spent less time courting females. Such males, instead, spent more time taking refuge in their nests. In contrast, unexposed control male gobies and males that were exposed to a nonpredatory fish, the Lake Eyre Hardyhead, Craterocephalus eyresii, did not alter their courtship behavior. Our results suggest that male courtship behavior is not only sensitive to the immediate presence of a predator but can persist even after the predatory threat has abated.

A High Aggression Strategy for Smaller Males

Male-male conflict is common among animals, but questions remain as to when, how and by whom aggression should be initiated. Factors that affect agonistic strategies include residency, the value of the contested resource and the fighting ability of the two contestants. We quantified initiation of aggression in a fish, the desert goby, Chlamydogobius eremius, by exposing nest-holding males to a male intruder. The perceived value of the resource (the nest) was manipulated by exposing half of the residents to sexually receptive females for two days before the trial. Resident male aggression, however, was unaffected by perceived mating opportunities. It was also unaffected by the absolute and relative size of the intruder. Instead resident aggression was negatively related to resident male size. In particular, smaller residents attacked sooner and with greater intensity compared to larger residents. These results suggest that resident desert goby males used set, rather than conditional, strategies for initiating aggression. If intruders are more likely to flee than retaliate, small males may benefit from attacking intruders before these have had an opportunity to assess the resident and/or the resource.

Both male and female identity influence variation in male signalling effort

BackgroundMale sexual displays play an important role in sexual selection by affecting reproductive success. However, for such displays to be useful for female mate choice, courtship should vary more among than within individual males. In this regard, a potentially important source of within male variation is adjustment of male courtship effort in response to female traits. Accordingly, we set out to dissect sources of variation in male courtship effort in a fish, the desert goby (Chlamydogobius eremius). We did so by designing an experiment that allowed simultaneous estimation of within and between male variation in courtship, while also assessing the importance of the males and females as sources of courtship variation.ResultsAlthough males adjusted their courtship depending on the identity of the female (a potentially important source of within-male variation), among-male differences were considerably greater. In addition, male courtship effort towards a pair of females was highly repeatable over a short time frame.ConclusionDespite the plasticity in male courtship effort, courtship displays had the potential to reliably convey information about the male to mate-searching females. Our experiment therefore underscores the importance of addressing the different sources contributing to variation in the expression of sexually-selected traits.

Do Male Desert Gobies Compromise Offspring Care to Attract Additional Mating Opportunities?

Males often play a critical role in offspring care but the time and energy invested in looking after young can potentially limit their ability to seek out additional mating opportunities. Recent studies, however, suggest that a conflict between male parental effort and mating effort may not always be inevitable, especially if breeding occurs near the nest, or if parental behaviours are under sexual selection. Accordingly, we set out to experimentally investigate male care and courtship in the desert goby Chlamydogobius eremius, a nest-guarding fish with exclusive paternal care. Despite courtship occurring near the nest, we found that when egg-tending males were given the opportunity to attract additional females, they fanned their eggs less often, engaged in shorter fanning bouts, and spent more of their time outside their nests courting. Our findings highlight the importance of understanding the circumstances under which reproductive tradeoffs are expected to occur and how these, in turn, operate to influence male reproductive decisions.

The interval between sexual encounters affects male courtship tactics in a desert-dwelling fish

Courtship displays are often important in determining male mating success but can also be costly. Thus, instead of courting females indiscriminately, males might be expected to adjust their signalling effort strategically. Theory, however, predicts that such adjustments should depend on the rate with which males encounter females, a prediction that has been subject to very little empirical testing. Here, we investigate the effects of female encounter rate on male courtship intensity by manipulating the time interval between sequential presentations of large (high quality) and small (low quality) females in a fish, the Australian desert goby Chlamydogobius eremius. Males that were presented with a small female immediately after a large female reduced their courtship intensity significantly. However, males courted large and small females with equal intensity if the interval between the sequential presentations was longer. Our results suggest that mate encounter rate is an important factor shaping male reproductive decisions and, consequently, the evolutionary potential of sexual selection.

Strategic male signalling effort in a desert-dwelling fish

Males often use elaborate courtship displays to attract females for mating. Much attention, in this regard, has been focused on trying to understand the causes and consequences of signal variation among males. Far less, by contrast, is known about within-individual variation in signal expression and, in particular, the extent to which males may be able to strategically adjust their signalling output to try to maximise their reproductive returns. Here, we experimentally investigated male courtship effort in a fish, the Australian desert goby, Chlamydogobius eremius. When offered a simultaneous choice between a large and a small female, male gobies spent significantly more time associating with, and courting, the former, probably because larger females are also more fecund. Male signalling patterns were also investigated under a sequential choice scenario, with females presented one at a time. When first offered a female, male courtship was not affected by female size. However, males adjusted their courtship effort towards a second female depending on the size of the female encountered previously. In particular, males that were first offered a large female significantly reduced their courtship effort when presented with a subsequent, smaller, female. Our findings suggest that males may be able to respond adaptively to differences in female quality, and strategically adjust their signalling effort accordingly.

Aerial and aquatic respiration of the Australian desert goby, Chlamydogobius eremius

Physiological, anatomical and behavioural adaptations enable the Australian desert goby, Chlamydogobius eremius, to live in mound springs and temporary aquatic habitats surrounding the south-eastern rim of the Lake Eyre drainage basin in the harsh inland of Australia. This study describes the desert goby's respiratory and metabolic responses to hypoxic conditions and its use of buccal air bubbles for gas exchange at the water surface. Oxygen consumption for C. eremius is significantly higher in water than in air under normoxic and hypoxic conditions. In water, total oxygen consumption ( V ̇ O 2 ) increases from normoxic conditions (253 μl g −1 h −1) to 8% ambient O 2 concentration (377 μl g −1 h −1), then decreases with increasing hypoxia of 4% O 2 (226 μl g −1 h −1) and at 2% O 2 (123 μl g −1 h −1). In air (fish were moist but out of water), V ̇ O 2 progressively decreases from normoxic conditions to hypoxic conditions (21% O 2, V ̇ O 2 is 169 μl g −1 h −1 to 39 μl g −1 h −1 at 2% O 2). These data indicate oxygen-conforming patterns with increasing hypoxia both in air and in water below 8% O 2. In water, opercular movement rates remain unchanged with increasing hypoxia (139 min −1 at 21% O 2, 154 min −1 at 8%, 156 min −1 at 4% and 167 min −1 at 2%) but in air, opercular movement rates are significantly lower than in water, corresponding with the lower metabolic rate (71 min −1 at 21% O 2, 53 min −1 at 8%, 96 min −1 at 4% and 64 min −1 at 2%). Chlamydogobius eremius can use a buccal air bubble for aerial O 2 uptake, most probably in response to increased aquatic hypoxia. In air, C. eremius relies more on the buccal bubble as an oxygen source with increasing hypoxia up to an ambient O 2 of 4% (7.1% of V ̇ O 2 at 21% O 2; 14.5% at 8% O 2; and 27.1% at 4% O 2), then when the available supply of O 2 is further reduced, it decreases (15% of V ̇ O 2 at 2% O 2) and respiration across the skin again makes a higher relative contribution. The Australian desert goby has a higher metabolic rate in higher salinities (336 μl g −1 h −1 in 35 ppt, 426 μl g −1 h −1 in 70 ppt) than in freshwater (235 μl O 2 g −1 h −1), presumably because of the increased metabolic cost of osmoregulation. There was no significant difference in V ̇ O 2 for fish in air that had come from varying salinities.

Affinities, origin and adaptive features of the Australian Desert GobyChlamydogobius eremius(Zietz, 1896) (Teleostei: Gobiidae)

The Desert Goby Chlamydogobius eremius (Zietz, 1896) is a gobiid teleost fish endemic to the Central Australian Basin, occurring mostly in artesian springs. Generic features for Chlamydogobius Whitley are supplied with emphasis on the modified head lateral-line system and on osteology. Comparisons with other Indo-Pacific genera suggest closest affinity with Mugilogobius Smitt, within a monophyletic grouping which also includes Weberogobius Koumans, Redigobius Herre, Pseudogobius Aurich, Brachygobius Bleeker, Hemigobius Bleeker, and Pandaka Herre. The origin of Ch. eremius is considered in the light of the Tertiary and Quaternary climatic history of the Central Australian Basin. The adaptiveness of certain morphological and life-history features found in Ch. eremius, such as elongate gut, black peritoneum, short pelvic disc, and large egg-size, is also discussed in relation to present habitat.