cytogenetics of bisexual/unisexual species of poecilia. ii. analysis of heterochromatin and nucleolar organizer regions in poecilia mexicana mexicana by c-banding and dapi, quinacrine, chromomycin a3, and silver staining.chromosomes of poecilia mexicana mexicana, one of the bisexual species involved in the hybrid origin of the unisexual teleost fish species p. formosa, were analyzed by several staining techniques. sex-specific, differential heterochromatin, found in other congeneric species, was not observed in p. m. mexicana. nucleolar organizer regions were polymorphic among individual specimens within a given population sample. a single specimen exhibiting intraindividual variability of chromosome pair 1 and ...19921380417
host specificity and population structure of two exotic helminths, camallanus cotti (nematoda) and bothriocephalus acheilognathi (cestoda), parasitizing exotic fishes in waianu stream, o'ahu, hawai'i.introduction of exotic fishes into hawai'ian streams has resulted in the simultaneous introduction of exotic parasites. camallanus corti (nematoda) and bothricephalus acheilognathi (cestoda) are the most prevalent and abundant fish helminths in hawai'ian streams. the population structure and host specificity of c. cotti and b. acheilognathi in exotic poeciliids were examined during may and june 1995 in waianu stream, o'ahu, hawai'i. prevalence and mean abundance of c. cotti were significantly di ...200312880255
male mate choice and sperm allocation in a sexual/asexual mating complex of poecilia (poeciliidae, teleostei).male mate choice is critical for understanding the evolution and maintenance of sexual/asexual mating complexes involving sperm-dependent, gynogenetic species. amazon mollies (poecilia formosa) require sperm to trigger embryogenesis, but the males (e.g. poecilia mexicana) do not contribute genes. males benefit from mating with amazon mollies, because such matings make males more attractive to conspecific females, but they might control the cost of such matings by providing less sperm to amazon m ...200517148157
an index of biotic integrity for shallow streams of the hondo river basin, yucatan index of biotic integrity (ibi) is proposed, based on the fish communities and populations in streams of the hondo river basin, mexico-belize. freshwater environments in this area are threatened by exotic fishes, eutrophication, and pesticide pollution, among other problems. this ibi should allow to identify the most vulnerable sites and eventually guide rehabilitation efforts. data on composition, structure, and function of fish communities were evaluated. twenty-three sites in the mexican p ...201021146199
does a predatory insect contribute to the divergence between cave- and surface-adapted fish populations?immigrant inviability, where individuals from foreign, ecologically divergent habitats are less likely to survive, can restrict gene flow among diverging populations and result in speciation. i investigated whether a predatory aquatic insect (belostoma sp.) selects against migrants between cave and surface populations of a fish (poecilia mexicana). cavefish were more susceptible to attacks in the light, whereas surface fish were more susceptible in darkness. environmentally dependent susceptibil ...200919443506
dietary niche overlap in sympatric asexual and sexual livebearing fishes poecilia spp.the present study investigated the spatiotemporal patterns in trophic resource use in a system of a gynogenetic poeciliid fish, the amazon molly poecilia formosa, and its sexual congeners the sailfin molly poecilia latipinna and the atlantic molly poecilia mexicana using gut contents analysis. no statistically significant differences in trophic resource use were found between sexual and gynogenetic species, but gut contents varied significantly across sites and over time. in addition, variation ...201122141886
morphological and molecular description of eight new species of gyrodactylus von nordmann, 1832 (platyhelminthes: monogenea) from poeciliid fishes, collected in their natural distribution range in the gulf of mexico slope, mexico.eight new species of gyrodactylus are described from poecilia mexicana, poeciliopsis gracilis, pseudoxiphophorus bimaculatus [syn. = heterandria bimaculata], and xiphophorus hellerii collected in the nautla and la antigua river basins in veracruz, and in the tecolutla river basin in puebla, mexico. analyzing the morphology of the marginal hooks, gyrodactylus pseudobullatarudis n. sp. and gyrodactylus xtachuna n. sp. are both very similar to gyrodactylus bullatarudis; gyrodactylus takoke n. sp. r ...201526091759
convergent life-history shifts: toxic environments result in big babies in two clades of poeciliids.the majority of studies on ecological speciation in animals have investigated the divergence caused by biotic factors like divergent food sources or predatory regimes. here, we examined a system where ecological speciation can clearly be ascribed to abiotic environmental gradients of naturally occurring toxic hydrogen sulfide (h(2)s). in southern mexico, two genera of livebearing fishes (poeciliidae: poecilia and gambusia) thrive in various watercourses with different concentrations of h(2)s. pr ...201019826772
male-biased predation of a cave fish by a giant water bug.male-biased predation has been described from several epigean species, and in many cases, intrinsic differences between the sexes (such as male ornaments) have been suggested as an explanation. here we report on male-biased predation of a cave fish (poecilia mexicana) by an aquatic insect (belostoma sp.) in a mexican sulfur cave. p. mexicana use aquatic surface respiration (asr) to survive in their sulfidic, hypoxic habitat. we found that males typically exhibit more asr activity than females, w ...200818437336
automictic reproduction in interspecific hybrids of poeciliid fish.automixis, the process whereby the fusion of meiotic products restores the diploid state of the egg, is a common mode of reproduction in plants but has also been described in invertebrate animals. in vertebrates, however, automixis has so far only been discussed as one of several explanations for isolated cases of facultative parthenogenesis. analyzing oocyte formation in f1 hybrids derived from poecilia mexicana limantouri and p. latipinna crosses (the cross that led to the formation of the gyn ...200717980594
local adaptation and pronounced genetic differentiation in an extremophile fish, poecilia mexicana, inhabiting a mexican cave with toxic hydrogen sulphide.we investigated genetic differentiation and migration patterns in a small livebearing fish, poecilia mexicana, inhabiting a sulfidic mexican limestone cave (cueva del azufre). we examined fish from three different cave chambers, the sulfidic surface creek draining the cave (el azufre) and a nearby surface creek without the toxic hydrogen sulphide (arroyo cristal). using microsatellite analysis of 10 unlinked loci, we found pronounced genetic differentiation among the three major habitats: arroyo ...200717305854
life on the edge: hydrogen sulfide and the fish communities of a mexican cave and surrounding waters.most eucaryotic organisms classified as living in an extreme habitat are invertebrates. here we report of a fish living in a mexican cave (cueva del azufre) that is rich in highly toxic h(2)s. we compared the water chemistry and fish communities of the cave and several nearby surface streams. our study revealed high concentrations of h(2)s in the cave and its outflow (el azufre). the concentrations of h(2)s reach more than 300 mum inside the cave, which are acutely toxic for most fishes. in both ...200616788733
geographical variation in reproductive character displacement in mate choice by male sailfin mollies.female amazon mollies, poecilia formosa, are a unisexual species that reproduce by gynogenesis. they must coexist and mate with males of other species (usually the mollies poecilia latipinna or poecilia mexicana) to induce embryogenesis, but inheritance is strictly maternal. we examined the mating preference of the male sailfin molly, p. latipinna, for female sailfin mollies versus amazon mollies, p. formosa. we compared the mating preferences of sympatric and allopatric populations collected th ...200111375091
The role of androgens in species recognition and sperm production in Atlantic mollies (Poecilia mexicana).Much is known about the role of hormones in the regulation of vertebrate mating behavior, including receptivity, and several components of mate choice. Hormones may modulate reproductive behavior in such a way to increase or decrease the individual's motivation, and therefore hormones may be important in mediating behavior associated with reproductive isolation. The mating complex of the all female gynogenetic Amazon mollies, Poecilia formosa, and their parental species (sailfin mollies, P. lati ...201222061426
monophyletic origin of multiple clonal lineages in an asexual fish (poecilia formosa).despite the advantage of avoiding the costs of sexual reproduction, asexual vertebrates are very rare and often considered evolutionarily disadvantaged when compared to sexual species. asexual species, however, may have advantages when colonizing (new) habitats or competing with sexual counterparts. they are also evolutionary older than expected, leaving the question whether asexual vertebrates are not only rare because of their 'inferior' mode of reproduction but also because of other reasons. ...201020964758
reduced opsin gene expression in a cave-dwelling fish.regressive evolution of structures associated with vision in cave-dwelling organisms is the focus of intense research. most work has focused on differences between extreme visual phenotypes: sighted, surface animals and their completely blind, cave-dwelling counterparts. we suggest that troglodytic systems, comprising multiple populations that vary along a gradient of visual function, may prove critical in understanding the mechanisms underlying initial regression in visual pathways. gene expres ...201019740890
a haploid-diploid-triploid mosaic of the amazon molly, poecilia formosa.we report the finding of the first haploid-diploid-triploid mosaic fish from the family poeciliidae. the animal was derived from a laboratory cross of a female f1 hybrid of poecilia mexicana and p. latipinna with a male from an ornamental strain derived from p. mexicana and p. sphenops (black molly). it was identified because of its unusual pigmentation pattern and molecular methods (flow cytometry, nor staining) confirmed its mosaic genotype. the mode of mosaic formation and the possible import ...200718160792
survival in an extreme habitat: the roles of behaviour and energy limitation.extreme habitats challenge animals with highly adverse conditions, like extreme temperatures or toxic substances. in this paper, we report of a fish (poecilia mexicana) inhabiting a limestone cave in mexico. several springs inside the cave are rich in toxic h(2)s. we demonstrate that a behavioural adaptation, aquatic surface respiration (asr), allows for the survival of p. mexicana in this extreme, sulphidic habitat. without the possibility to perform asr, the survival rate of p. mexicana was lo ...200717639290
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