Biology subjects

Karatgi, R.

Publications and source records attributed to Karatgi, R..

3 recordsLinked to original sources

bioRxiv2026

Transcriptomic differences underlying fin sexual dichromatism and male color polymorphism in bluefin killifish (Lucania goodei)

Color polymorphisms offer a powerful lens for examining how selection shapes genetic and phenotypic variation. Genomic analyses of color variation provide deeper insight into how genetic differences and phenotypic plasticity contribute to trait variation. Here, we use the bluefin killifish (Lucania goodei) to study this relationship. Male fins can display either red or yellow coloration based on pigments (pterins) or blue structural coloration (iridophores) often induced in UV-depauperate environments. Female fins lack pigmentation. To characterize the molecular basis of this variation, we assembled a high-quality genome and examined gene expression in the anal fins of male and female bluefin killifish to identify the molecular mechanisms underlying color variation. Our gene expression analysis found sex differences driven by male-biased upregulation of melanin synthesis and canonical pigment pathway genes. We additionally identified that the progesterone sex receptor was upregulated in females. Among male color morphs, several genes involved in xanthophore and iridophore formation differed between blue and non-blue males, including the transcription factor tfec, and iridophore-patterning genes atic, pnp4a, and sox10. Extraocular opsins, which are involved in non-image-forming light perception, were expressed at low levels across all fins, but showed population- and morph-specific patterns; notably, rgrb (retinal G protein coupled receptor b) was upregulated in blue males. To the best of our knowledge, this is the first report of an extraocular opsin varying as a function of population and color morph. Together, these results identify the pigment pathways underlying male-limited color polymorphisms and reveal candidate genes likely involved in light-sensitive phenotypic plasticity.

evolutionary biology↗

bioRxiv2024

When Rivals Are Absent: Male Aggression Towards Females in Bluefin Killifish

The process of obtaining mates, mating, and (potentially) caring for offspring is costly. While there are inherent costs to reproduction, behavioral interactions among individuals are often the primary drivers of reproductive costs. Males frequently compete for territories and females; females may compete for food or males; males often harass females. Here, we sought to determine whether reproductive costs were primarily due to male/male competition, female/female competition, or male/female interactions in the bluefin killifish. In this species, males guard small spawning territories where females visit them daily to spawn. To manipulate the potential for male and female competition and male/female interactions, we altered the sex ratio and density of each sex across four treatments (1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3 males: 3 females). Female mortality was higher than male mortality. Surprisingly, female mortality and male aggressive behaviors towards females (i.e., chases) were highest in treatments with a single male. Male-male aggression was present, but males often resolved these disputes via signaling by flaring their fins. There was little evidence for overt aggression among females. When males lack rivals, they turn their territorial defense towards females. These costs help explain why, in nature, females promptly leave male territories following spawning and join loose shoals with conspecific females and minnows.

animal behavior and cognition↗

bioRxiv2022

Competing females strategically combine signals and physical aggression differently from males in a polygynous tropical lizard

Intrasexual competition, the intense competition between individuals of the same sex, is a strong evolutionary force that is well known to select for elaborate and spectacular traits in males. In contrast, female-female competition is poorly understood. Although historically expected to be weak, evidence for female-female competition is fast accumulating. Yet, systematic studies of such competition are rare. Here, we frame and test for a strategy of competition in females in a wild population of a classically polygynous lizard, Psammophilus dorsalis. We used models of female P. dorsalis to simulate a gradient in perceived competitor threat to individually tagged, wild females on their territories, and comprehensively measured their signalling and aggression responses. Similar experiments were performed with males. Our results clearly demonstrate a complex, threat-sensitive strategy of direct competition among females in this species with conventional sex roles. Females systematically escalate their use of diverse signals along a gradient in threat and show surprisingly high levels of physical aggression. Comparisons with the responses of males to simulated threats reveal distinct sex differences in competition strategies that match theoretical expectations derived from life history. Using these findings, we argue that female-female competition may be complex but cryptic, requiring experimental manipulations to uncover.

animal behavior and cognition↗