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.

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

http://faculty.salisbury.edu/~kxhunter/Garcia_2014_Fighting%20Experince_Metabolic_Anoles.pdf

Mechanisms of decision making during contests in green anole lizards: prior experience and assessment

Nonreversing mirrors elicit behaviour that more accurately predicts performance against live opponents

The mangrove rivulus fish (Kryptolebias marmoratus) is an emerging model for research in the biological sciences. The species is androdioecious, with populations consisting predominantly of self-fertilizing hermaphrodites and a low abundance of males, but no females. Males arise either through environmental sex determination at the embryonic stage or environmentally driven sex change from hermaphrodite at the adult stage. Marked sexual dimorphisms in external morphological characters accompany gonadal transitions, including the loss of a caudal ocellus (‘eyespot’) and the development of orange color in males. How well external morphological features predict internal gonadal morphology, however, has not been systematically examined across the geographical range of this species. Our goal was to identify reliable external morphological predictors of animals possessing an ovotestis (hermaphrodite) or a testis (male) and to see if the strength of prediction is consistent throughout rivulus’ geographical range. We demonstrate that the state of the ocellus and, to a greater extent, orange coloration are key predictors of internal gonadal state. However, the degree to which these characteristics are predictive of internal gonadal state was region-specific, with the ocellus and orange status of animals from Bahamas and Belize, respectively, having a lower probability of forecasting internal gonadal state than those from other regions. These results will help to streamline laboratory studies by allowing unambiguous assignment of sex, and will assist field studies by providing greater opportunity to determine sex ratios in wild populations.

Relationships between external sexually dimorphic characteristics and internal gonadal morphology in a sex-changing fish

Estrogenic compounds including 17β estradiol (or E2) are known to negatively affect the reproductive system of many animals, including fish, leading to feminization, altered sex ratio, reduced fecundity, and decreased gonadosomatic index. The objective of this study was to evaluate the effects of varying concentrations of water-soluble 17β estradiol exposure on the external morphology of Bluegill. An experiment was set up where fish were individually maintained in 10-g tanks and exposed to 17β estradiol concentrations of 40 and 80 ng/L or no 17β estradiol exposure (the control). Fish were exposed for 21 days, with 17β estradiol replenished each week to account for 17β estradiol half-life. Fish were photographed laterally before and after the 21-day exposure to 17β estradiol. Landmark-based geometric morphometrics were conducted in MorphoJ and canonical variate and discriminant function analysis were used to compare the morphological changes in the fish under 17β estradiol exposure. The results showed that 17β estradiol exposure caused male dimorphic characters to change in Bluegill by becoming less prevalent. Specifically, there was a narrowing of the caudal peduncle, smaller nape protrusion, reduced opercular flap and pectoral fin, and a deeper body in the exposed groups compared with control fish under both concentrations. This research highlights the widespread effects of 17β estradiol on fish health beyond the reproductive system, which could have important conservation implications by affecting mate selection and reducing reproductive success.

Exposure to 17β estradiol causes erosion of sexual dimorphism in Bluegill ( Lepomis macrochirus )

Female convict cichlids (Amatitlania siquia) exhibit bright orange ventral coloration that males lack. The behavioral implications of this color are poorly understood, particularly in naturally occurring populations where female coloration could play a role in the expression of territorial nest-guarding behaviors. In this field experiment, monogamous breeding pairs of convict cichlids were presented with 3D printed model conspecific intruders of three body sizes (small, medium, and large) exhibiting three orange patch sizes (large, small, or none) to observe how territorial aggression varied as a function of intruder size and female coloration. Individuals occupying breeding pairs that were defending hatched offspring were significantly more aggressive toward intruders with small and large amounts of orange than toward models lacking orange, indicating that color is an important context-dependent elicitor of aggression in this species. Males were significantly more aggressive toward the intruder than females, and male aggression was strongly influenced by their size relative to the intruder. When males were smaller than the intruder, they performed significantly more aggressive acts than when they were the same size or larger than the intruder; this trend persisted across three putative populations in Lake Xiloa, Nicaragua. A potential explanation for these findings is that the orange color functions as a signal of individual quality or breeding readiness and that breeding pairs increase aggression to repel intruders that pose the greatest threat to pair bond and nest maintenance. One or both sexes of many animal species possess brightly colored features that might communicate information about overall heath or reproductive status. In convict cichlid fish, males and females establish pair bonds and jointly defend their nest and offspring. Single females exhibit striking orange coloration that males and breeding females lack. Our field-based experiment provided evidence that more colorful females, which likely pose a threat to pair bond stability and nest maintenance, incite more aggression from breeding pairs than drab females. Our study suggests that color provides salient information about, perhaps, female quality or readiness to breed in natural populations, and adds to a growing body of research that seeks to understand the varied roles that colorful ornaments play in animal communication.

Seeing orange: breeding convict cichlids exhibit heightened aggression against more colorful intruders

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 sex-changing 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.

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

The additional design consideration of a plug-in hybrid electric vehicle (PHEV) caused by its recharging capability requires an optimal hybrid powertrain control strategy to fully exploit the vehicle's capability. Amongst many aspects of control algorithm development and design optimisation, the advantage of including a pure electric vehicle (EV) mode in the vehicle driving modes of a PHEV with a post-transmission electric motor was studied in this research. For this purpose, architecture of a series-parallel PHEV was determined and its simulation model was developed. Then, various simulations were conducted to evaluate technical merits of the pure EV mode in terms of fuel economy and emissions. The simulation results favourably supports inclusion of the pure EV mode as one of the driving modes in the powertrain control strategy of the studied PHEV model with a post-transmission electric motor.

Ryan Jones

Papers

Seeing orange: breeding convict cichlids exhibit heightened aggression against more colorful intruders

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

Effect of an electric vehicle mode in a plug-in hybrid electric vehicle with a post-transmission electric motor

Contest decisions are governed by own size and opponent size category in mangrove rivulus fish, Kryptolebias marmoratus

Development of a Catalytic Converter Cool-Down Model to Investigate Intermittent Engine Operation in HEVs