On two Jenynsia taxa (Cyprinodontiformes: Anablepidae) from Argentina, originally placed in the poeciliid genus Xiphophorus
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Abstract:
The type material of Xiphophorus heckelii Weyenbergh, 1874 and X. obscurus Weyenbergh, 1877 has apparently been re-examined for the first time. Xiphophorus heckelii is confirmed as a junior synonym of Jenynsia multidentata (Jenyns, 1842). Xiphophorus obscurus is recognized as a senior synonym of Jenynsia pygogramma Boulenger, 1902, which is placed in synonymy. A lectotype and paralectotypes are designated for Jenynsia obscura (Weyenbergh, 1877).Keywords:
Xiphophorus
Cyprinodontiformes
Synonym (taxonomy)
Poeciliidae
Killifish
FERNANDEZ, ANDRE A., Ph.D., August 2008, Biological Sciences SELECTION FOR THE XMRK ONCOGENE IN XIPHOPHORUS CORTEZI (142 pp.) Director of Dissertation: Molly R. Morris This dissertation examines sexual selection as a mechanism underlying the continued evolutionary maintenance of the Xmrk (Xiphophorus melanoma receptor kinase) cancer gene within the Xiphophorus melanoma model. Additionally, I expand this animal model to include Xiphophorus nezahualcoyotl (Order: Cyprinodontiformes, Family: Poeciliidae) as a species capable of non-hybrid melanoma formation. I use the well-studied Northern swordtail, Xiphophorus cortezi, collected from six localities throughout its geographic distribution to address whether the pigment pattern from which melanomas form (spotted caudal, Sc) and/or the Xmrk oncogene responsible for melanomas within Xiphophorus are advantageous in the acquisition of mates. Specifically, I address the following questions: 1) Is there a relationship between male aggression levels and the Sc phenotype and/or Xmrk genotype within individual males; 2) Does male aggressive response differ based upon the presence of the Sc phenotype; 3) Do females preferentially associate with Sc patterned males over non-Sc males or with larger Sc patterned males to size-matched males with smaller Sc patterns; and 4) Does the frequency of the Sc phenotype or the Xmrk genotype across the six populations influence male aggression levels or female mate choice decisions? 4 The results of mirror image trials found that the Sc macromelanophore pattern as well as the Xmrk oncogene (regardless of the presence of Sc) is correlated with increased aggression. In addition, Sc appears to function as a visual signal in male agonistic encounters because male aggressive response decreases when viewing their Sc image as compared with their non-Sc image. The frequency of Xmrk in males across populations ranged 0% to 87%. However, there was no difference in the aggression levels of males with Sc and/or Xmrk from each population thus the frequency of Xmrk within a population does not directly influence individual levels of male aggression. X. cortezi females from three populations, located in separate drainages that are genetically divergent, prefer to associate with Sc patterned males to non-Sc males. Moreover, X. cortezi females prefer males with an enhanced Sc pattern, which would occur during melanoma formation, to males with a reduced Sc pattern. However, unlike male aggression, there was variation in female preference for Sc males and it appeared to be influenced by the frequency of Xmrk in the population. Females from one population, which had the highest frequencies of Sc and Xmrk in females, discriminated against Sc patterned males and preferred to associate with non-Sc males. These results suggest there is a negative relationship between the strength of female preference for Sc and the frequency of Xmrk in females across populations. Because offspring with two copies of Xmrk have reduced fitness, and these offspring are more likely to occur in populations in which the frequency of Xmrk in females is high, females can increase their reproductive fitness by avoiding males with Sc (and therefore Xmrk) in these populations. 5 The findings of this dissertation have several important implications for the Xiphophorus melanoma model. First, non-hybrid melanomas occur in more Xiphophorus species than initially realized and may be more biologically relevant within Xiphophorus than melanomas formed via interspecific hybridization. Second, the Xmrk oncogene is associated with increased male aggression and thereby provides a competitive advantage for individuals in male-male competition. In addition, the macromelanophore patterns associated with the Xmrk oncogene can serve as signals in these male agonistic encounters. Third, female mate choice for the Xmrk associated melanin patterns plays an important role in the evolutionary maintenance of this oncogene. Finally, the relative frequency of Xmrk within each sex of a population does influence female mating decisions and is likely responsible for the continued polymorphism of Xmrk in all Xiphophorus that have retained this cancer gene. Collectively, the research presented in this dissertation demonstrates that sexual selection is important in explaining the persistence of Xmrk within this system. Approved: ____________________________________________________________
Xiphophorus
Poeciliidae
Cyprinodontiformes
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Poecilia
Cyprinodontiformes
Xiphophorus
Poeciliidae
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A positive size-fecundity relationship in female Heterandria formosa is the result of an increase, with increasing size of female, in number of young per brood, not of a decrease in interbrood intervals. The lack of shorter interbrood intervals in smaller females is not consistent with one of the hypotheses on the evolution of superfetation. Larger females produce heavier individual offspring. After maintenance in the laboratory with excess food, both the size-fecundity relationship and the correlation between female size and average offspring weight disappeared. We suggest that Heterandria is food limited in natural populations and that larger females are better able to compete for food and nourish their developing embryos.
Poeciliidae
Killifish
Cyprinodontiformes
Variation (astronomy)
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During a field expedition in 2020, we recorded specimens of an invasive platy fish, Xiphophorus maculatus , in the state of Maranhão, Brazil. This new occurrence, in the Municipality of São Luis, is only the second time that this non-native species has been found in northeastern Brazil. We provide an updated list of all invasive species recorded from the island of São Luís, highlighting the negative impacts they may confer for the native biodiversity.
Cyprinodontiformes
Xiphophorus
Poeciliidae
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Xiphophorus
Poeciliidae
Cyprinodontiformes
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Effects of adult sex ratio on larvae number and survival of fry in Xiphophorus maculatus (Cyprinodontiformes: Poeciliidae)
Poeciliidae
Cyprinodontiformes
Xiphophorus
Brachionus calyciflorus
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ABSTRACT Headwater creeks are environments susceptible to invasion by non-native fishes. We evaluated the reproduction of 22 populations of the non-native livebearers guppy Poecilia reticulata, black molly Poecilia sphenops, Yucatan molly Poecilia velifera, green swordtail Xiphophorus hellerii, southern platyfish Xiphophorus maculatus, and variable platyfish Xiphophorus variatus during an annual cycle in five headwater creeks located in the largest South American ornamental aquaculture center, Paraíba do Sul River basin, southeastern Brazil. With few exceptions, females of most species were found reproducing (stages 2, 3, 4) all year round in the creeks and gravid females of all species showed small sizes indicating stunting. Juveniles were frequent in all sites. The fecundity of the six poeciliids was always low in all periods. The sex ratio was biased for females in most species, both bimonthly as for the whole period. Water temperature, water level and rainfall were not significantly correlated with reproduction in any species. Therefore, most populations appeared well established. The pertinence of different management actions, such as devices to prevent fish escape, eradication with rotenone and research about negative effects on native species, is discussed in the light of current aquaculture practices in the region.
Xiphophorus
Poecilia
Poeciliidae
Cyprinodontiformes
Guppy
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Xiphophorus
Poeciliidae
Cyprinodontiformes
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The fish Xiphophorus helleri is a commercially important species. Here we analyze several cultivation variables. We studied them for 120 days in 10-gallon aquaria without aeration; 1 fry per liter, the temperature varied between 26,3 and 26,9 ° C. The pH ranged from 8,1 to 8,8 and the oxygen concentration from 6,2 to 6,6mg / L. Api-aba balanced fodd with 25% protein was used, three hormones were added: 1) Sten 2) Primoteston and 3) Sostenon 250. Sex reversal was 84,3%, 91,4% and 93,3% correspondingly. A fish with treatment 1 gained an average of 0,55g and total length of 5,4cm, with treatment 2: 0,59g and 5cm; and with treatment 3: 0,55g and 4,1cm. The 8th fortnight survival was 80%, 90% and 75% correspondingly; these differences are not statistically significant. The three treatments gave the expected results of sex reversal, growth and survival.KEY WORDSSexual revertion, animal feed, population density, hormone supply, aquaria without aeration
Xiphophorus
Cyprinodontiformes
Poeciliidae
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Poeciliidae
Xiphophorus
Cyprinodontiformes
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