Changes in reproductive physiology of mangrove rivulus <i>Kryptolebias marmoratus</i> following exposure to environmentally relevant doses of ethinyl oestradiol

To maximize reproductive success, many animal species have evolved functional sex change. Theory predicts that transitions between sexes should occur when the fitness payoff of the current sex is exceeded by the fitness payoff of the opposite sex. We examined phenotypic differences between the sexes in a sexchanging vertebrate, the mangrove rivulus fish (Kryptolebias marmoratus), to elucidate potential factors that might drive the 'decision' to switch sex. Rivulus populations consist of self-fertilizing hermaphrodites and males. Hermaphrodites transition into males under certain environmental conditions, affording us the opportunity to generate 40 hermaphrodite-male pairs where, within a pair, individuals possessed identical genotypes despite being different sexes. We quantified steroid hormone levels, behavior (aggression and risk taking), metabolism and morphology (organ masses). We found that hermaphrodites were more aggressive and risk averse, and had higher maximum metabolic rates and larger gonadosomatic indices. Males had higher steroid hormone levels and showed correlations among hormones that hermaphrodites lacked. Males also had greater total mass and somatic body mass and possessed considerable fat stores. Our findings suggest that there are major differences between the sexes in energy allocation, with hermaphrodites exhibiting elevated maximum metabolic rates, and showing evidence of favoring investments in reproductive tissues over somatic growth. Our study serves as the foundation for future research investigating how environmental challenges affect both physiology and reproductive investment and, ultimately, how these changes dictate the transition between sexes.

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“…Johnson et al (2015), however, showed that hermaphrodites have higher E2 than males when aged 330-550 days.…”

Section: Discussionmentioning

confidence: 99%

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

Garcia

Ferro

Mattox

et al. 2016

Journal of Experimental Biology

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“…The coastal habitats of mangrove rivulus, which are being developed at an extraordinary rate, are subject to significant anthropogenic disturbance, particularly with respect to the influx of environmental pollutants (e.g., endocrine disruptors) from urban run-off and wastewater treatment plants. Research into the effects of such pollutants has demonstrated staggering, often sex-specific, effects on gene expression, endocrine function, reproduction, and survival ( Lee et al 2006 , 2007 ; Rhee et al 2008 , 2010, 2011 ; Rhee, Lee, et al 2009 ; Rhee, Kang, et al 2009 ; Farmer and Orlando 2012 ; Johnson et al 2016 ), leading to rivulus being promoted as an important model system for ecotoxicology ( Davis 1986 ; Lee et al 2008 ). Most studies on rivulus’ physiological and locomotory adaptations to extreme environments and on their responses to environmental pollutants use one or very few lineages, which limits our ability to understand the full scope of variation on which selection can act to drive genetic and phenotypic divergence among populations.…”

Section: Introductionmentioning

confidence: 99%

The Genome of the Self-Fertilizing Mangrove Rivulus Fish,Kryptolebias marmoratus: A Model for Studying Phenotypic Plasticity and Adaptations to Extreme Environments

et al. 2016

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The mangrove rivulus (Kryptolebias marmoratus) is one of two preferentially self-fertilizing hermaphroditic vertebrates. This mode of reproduction makes mangrove rivulus an important model for evolutionary and biomedical studies because long periods of self-fertilization result in naturally homozygous genotypes that can produce isogenic lineages without significant limitations associated with inbreeding depression. Over 400 isogenic lineages currently held in laboratories across the globe show considerable among-lineage variation in physiology, behavior, and life history traits that is maintained under common garden conditions. Temperature mediates the development of primary males and also sex change between hermaphrodites and secondary males, which makes the system ideal for the study of sex determination and sexual plasticity. Mangrove rivulus also exhibit remarkable adaptations to living in extreme environments, and the system has great promise to shed light on the evolution of terrestrial locomotion, aerial respiration, and broad tolerances to hypoxia, salinity, temperature, and environmental pollutants. Genome assembly of the mangrove rivulus allows the study of genes and gene families associated with the traits described above. Here we present a de novo assembled reference genome for the mangrove rivulus, with an approximately 900 Mb genome, including 27,328 annotated, predicted, protein-coding genes. Moreover, we are able to place more than 50% of the assembled genome onto a recently published linkage map. The genome provides an important addition to the linkage map and transcriptomic tools recently developed for this species that together provide critical resources for epigenetic, transcriptomic, and proteomic analyses. Moreover, the genome will serve as the foundation for addressing key questions in behavior, physiology, toxicology, and evolutionary biology.

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“…It is possible that we might also observe a life history ‘trade‐off’ between reproduction and terrestrial jumping performance in the mangrove rivulus. In this species, reproduction can occur year‐round (Lomax, Carlson, Wells, Crawford, & Earley, ), and the gonad can make up 12% of their body mass (Johnson, Weinersmith, & Earley, ). Likewise, because hermaphrodites tend to lay single to several embryos on a regular basis (Lomax et al., ), high reproductive investment may place a continual burden on jumping performance in sexually mature individuals.…”

Section: Discussionmentioning

confidence: 99%

Ontogeny of the morphology‐performance axis in an amphibious fish (Kryptolebias marmoratus)

et al. 2017

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Establishing links between morphology and performance is important for understanding the functional, ecological, and evolutionary implications of morphological diversity. Relationships between morphology and performance are expected to be age dependent if, at different points during ontogeny, animals must perform in different capacities to achieve high fitness returns. Few studies have examined how the relationship between form and function changes across ontogeny. Here, we assess this relationship in the amphibious mangrove rivulus (Kryptolebias marmoratus) fish, a species that is both capable of and reliant on "tail-flip jumping" for terrestrial locomotion. Tail-flip jumping entails an individual transferring its weight to the caudal region of the body, launching itself from the substrate to navigate to new aquatic or semi-aquatic habitats. By combining repeated trials of jumping performance in 237 individuals from distinct age classes with a clearing and staining procedure to visualize bones in the caudal region, we test the hypotheses that as age increases (i) average jumping performance (body lengths jumped) will increase, (ii) the amount of variation for each trait will change, and (iii) the patterns of covariation/correlation among traits, which tell us about the integration of form with function, will also change. We find a significant increase in size-adjusted jumping performance with age, and modification to the correlation structure among traits across ontogeny. However, we also find that significant links between form and function evident in young animals disappear at later ontogenetic stages. Our study suggests that different functional mechanisms may be associated with high performance at different stages of development.

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Changes in reproductive physiology of mangrove rivulus Kryptolebias marmoratus following exposure to environmentally relevant doses of ethinyl oestradiol

Cited by 6 publications

References 62 publications

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

The Genome of the Self-Fertilizing Mangrove Rivulus Fish,Kryptolebias marmoratus: A Model for Studying Phenotypic Plasticity and Adaptations to Extreme Environments

Ontogeny of the morphology‐performance axis in an amphibious fish (Kryptolebias marmoratus)

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