First description of color variations in the annual killifish Millerichthys robustus, and preliminary observations about its geographical distribution

Domínguez-Castanedo, Omar; Muñoz-Campos, Tessy M.; Valdesalici, Stefano; Valdez-Carbajal, Sharon; Passos, Carlos

doi:10.1007/s10641-021-01076-w

Cited by 3 publications

(1 citation statement)

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“…They were composed of aggressive and courtship displays characteristic of female and male behaviour. We recorded the presence of any colour component of the opposite sex phenotype in fish from compartments 2 and 3 based on the sex-specific colouration in this species described by Domínguez-Castanedo et al 36 .…”

Section: Methodsmentioning

confidence: 99%

Protogynous functional hermaphroditism in the North American annual killifish, Millerichthys robustus

Domínguez-Castanedo

Valdez-Carbajal

Muñoz-Campos

et al. 2022

Sci Rep

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Sex change (sequential hermaphroditism) has evolved repeatedly in teleost fishes when demographic conditions mediate fundamentally different sex-specific returns for individuals of particular age and size. We investigated the conditions for potential sex change in an annual killifish (Millerichthys robustus) from temporary pools in Mexico. In natural populations, we detected adults with intersex colouration and gonads. Therefore, we experimentally tested whether this apparent sex change can be generated by manipulation of ecological and social conditions, rather than being caused by environmental disturbance. We demonstrated functional protogynous (female-to-male) sex change in 60% replicates, when groups of five females interacted and had a visual and olfactory cue of a male. Only one female changed sex in any given replicate. The sex change never occurred in isolated females. Protandrous (male-to-female) hermaphroditism was not recorded. We characterized gradual changes in behaviour, colouration and gonad structure during the sex change process. The first behavioural signs of sex change were observed after 23 days. Secondary males spawned successfully after 75 days. We discuss the adaptive potential of sex change in short-lived annual fishes through the seasonal decline of males, and during colonization of new habitats. This is the first observation of functional hermaphroditism in an annual killifish.

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Section: Methodsmentioning

confidence: 99%

Protogynous functional hermaphroditism in the North American annual killifish, Millerichthys robustus

Domínguez-Castanedo

Valdez-Carbajal

Muñoz-Campos

et al. 2022

Sci Rep

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An independent origin of an annual life cycle in a North American killifish species

Domínguez-Castanedo,

Thompson,

Meredith

et al. 2024

Biological Journal of the Linnean Society

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An annual life cycle is characterized by short-lived adults that exploit seasonally productive but temporary habitats, paired with a hardy embryo stage that survives unfavourable environmental conditions, such as winter or the dry season. This life cycle is rare amongst vertebrates but has evolved independently several times in African and South American killifishes adapted to life in seasonally ephemeral aquatic pools. A single species of North American annual killifish, with a limited geographical distribution in Mexico, also exhibits this seasonal life cycle. This enigmatic species, Millerichthys robustus, is geographically separated from the nearest South American annual killifish species by >2000 km. Millerichthys robustus exhibits morphological features that have led to several competing phylogenetic hypotheses. To date, its phylogenetic relationships are unclear because no molecular data have been available. Here, we sequence the mitochondrial genome of Millerichthys robustus and generate a molecular phylogeny of killifishes that includes this species. Our results indicate that, rather than being most closely related to South American annual killifishes, this species is sister to two non-annual killifish species from Cuba (Rivulus cylindraceus and Rivulus berovidesi). Ancestral state reconstruction strongly supports an independent origin of an annual life cycle and embryonic diapause in Millerichthys robustus.

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The complete genome sequence of the protogynous hermaphrodite North American annual killifish Millerichthys robustus (Rivulidae, Cyprinodontiformes)

Domínguez-Castanedo,

Berbel-Filho,

Pirro

et al. 2024

Biodiversity Genomes

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The Mexican Rivulus, Millerichthys robustus, is an enigmatic species of seasonal killifish endemic of the Southeast Mexico that has changed paradigms on the evolution of annualism in killifishes. This species survives in ephemeral environments that experience a period of seasonal drought that causes the death of all adult fish. However, populations persist due to their drought-resistant embryos capable of arresting their development in diapause until the next the rainy season. Millerichthys evolved unique characteristics within annual killifishes as a functional sequential hermaphroditism, in which females change to males (protogynous) under perceived conditions of mate competition. Also, M. robustus express different color phenotypes in both sexes: five-color phenotypes continuously distributed in various perceptual units between yellow and red in males, and different number of ocelli disposed in caudal peduncle in females. The phylogenetic relationships of M. robustus revealed that it is a sister clade to two non-annual species found exclusively in Cuba (Rivulus cylindraceus and Rivulus berovidesi), indicating that the annual life cycle, through the acquisition of embryonic diapause, has evolved independently in this species. Here, we present the complete genome sequences for the North American annual killifish Millerichthys robustus. The raw data and assembled genome are available in GeneBank.

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First description of color variations in the annual killifish Millerichthys robustus, and preliminary observations about its geographical distribution

Cited by 3 publications

References 60 publications

Protogynous functional hermaphroditism in the North American annual killifish, Millerichthys robustus

Protogynous functional hermaphroditism in the North American annual killifish, Millerichthys robustus

An independent origin of an annual life cycle in a North American killifish species

The complete genome sequence of the protogynous hermaphrodite North American annual killifish Millerichthys robustus (Rivulidae, Cyprinodontiformes)

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