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1.
J Exp Biol ; 221(Pt 8)2018 04 13.
Article in English | MEDLINE | ID: mdl-29511069

ABSTRACT

Fishes acclimated to hypoxic environments often increase gill surface area to improve O2 uptake. In some species, surface area is increased via reduction of an interlamellar cell mass (ILCM) that fills water channels between gill lamellae. Amphibious fishes, however, may not increase gill surface area in hypoxic water because these species can, instead, leave water and breathe air. To differentiate between these possibilities, we compared wild amphibious mangrove rivulus Kryptolebias marmoratus from two habitats that varied in O2 availability - a hypoxic freshwater pool versus nearly anoxic crab burrows. Fish captured from crab burrows had less gill surface area (as ILCMs were enlarged by ∼32%), increased rates of normoxic O2 consumption and increased critical O2 tension compared with fish from the freshwater pool. Thus, wild mangrove rivulus do not respond to near-anoxic water by decreasing metabolism or increasing O2 extraction. Instead, fish from the crab burrow habitat spent three times longer out of water, which probably caused the observed changes in gill morphology and respiratory phenotype. We also tested whether critical O2 tension is influenced by genetic heterozygosity, as K. marmoratus is one of only two hermaphroditic vertebrate species that can produce both self-fertilized (inbred) or out-crossed (more heterozygous) offspring. We found no evidence for inbreeding depression, suggesting that self-fertilization does not impair respiratory function. Overall, our results demonstrate that amphibious fishes that inhabit hypoxic aquatic habitats can use a fundamentally different strategy from that used by fully aquatic water-breathing fishes, relying on escape behaviour rather than metabolic depression or increased O2 extraction ability.


Subject(s)
Cyprinodontiformes/anatomy & histology , Cyprinodontiformes/physiology , Gills/anatomy & histology , Gills/physiology , Oxygen/analysis , Animals , Cyprinodontiformes/genetics , Ecosystem , Fresh Water/chemistry , Hermaphroditic Organisms , Inbreeding Depression , Oxygen Consumption
2.
J Fish Biol ; 87(3): 519-38, 2015 Sep.
Article in English | MEDLINE | ID: mdl-26223378

ABSTRACT

The mangrove rivulus, Kryptolebias marmoratus (Rivulidae, Cyprinodontiformes), is phylogenetically embedded within a large clade of oviparous (egg laying) and otherwise mostly gonochoristic (separate sex) killifish species in the circumtropical suborder Aplocheiloidei. It is unique in its reproductive mode: K. marmoratus is essentially the world's only vertebrate species known to engage routinely in self-fertilization as part of a mixed-mating strategy of selfing plus occasional outcrossing with gonochoristic males. This unique form of procreation has profound population-genetic and evolutionary-genetic consequences that are the subject of this review.


Subject(s)
Genetics, Population , Hermaphroditic Organisms/genetics , Killifishes/genetics , Self-Fertilization , Animals , Biological Evolution , Male , Phylogeny , Phylogeography
3.
J Fish Biol ; 79(7): 2095-105, 2011 Dec.
Article in English | MEDLINE | ID: mdl-22141910

ABSTRACT

This study documents unexpectedly low levels of intra and interpopulation genetic diversity in Kryptolebias ocellatus, an androdioecious and predominantly self-fertilizing killifish from south-eastern Brazil. This finding generally is inconsistent with the established opinion that the K. ocellatus and K. marmoratus clade originated in this geographic region and later dispersed northward into the Caribbean.


Subject(s)
Cyprinodontiformes/genetics , Genetic Variation , Animals , Brazil , Cyprinodontiformes/classification , Phylogeny
4.
Mol Ecol ; 19(2): 257-68, 2010 Jan.
Article in English | MEDLINE | ID: mdl-20015140

ABSTRACT

Swordtails (Xiphophorus; Poeciliidae) have figured prominently in research on fish mating behaviours, sexual selection, and carcinogenesis, but their population structures and dispersal patterns have been relatively neglected. Using nine microsatellite loci, we estimated genetic differentiation in Xiphophorus helleri within and between adjacent streams in Belize. The genetic data were complemented by a tagging study of movement within one stream. In the absence of physical dispersal barriers (waterfalls), population structure followed an isolation by distance (IBD) pattern. Genetic differentiation (F(ST) up to 0.07) was significant between and within creeks, despite high dispersal in the latter as judged by the tagging data. Such heterogeneity apparently was a result of genetic drift in local demes, due to small population sizes and highly skewed paternity. The IBD pattern was interrupted by waterfalls, boosting F(ST) above 0.30 between adjacent samples across these barriers. Overall, our results are helpful in understanding the interplay of evolutionary forces and population dynamics in a small fish living in a changeable habitat.


Subject(s)
Animal Migration , Cyprinodontiformes/genetics , Genetic Drift , Genetics, Population , Animals , Belize , Evolution, Molecular , Female , Genetic Variation , Geography , Linkage Disequilibrium , Male , Microsatellite Repeats , Models, Genetic , Models, Statistical , Population Dynamics , Rivers
5.
Mol Ecol ; 14(2): 647-51, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15660953

ABSTRACT

Reproduction of attached large brown algae is known to occur only by sexual zygotes. Using microsatellites we show evolution of asexual reproduction in the bladder wrack promoting population persistence in the brackish water Baltic Sea (< 6 psu). Here a dwarf morph of Fucus vesiculosus is dominated by a single clone but clonal reproduction is also present in the common form of the species. We describe a possible mechanism for vegetative reproduction of attached algae, and conclude that clonality plays an important role in persistence and dispersal of these marginal populations, in which sexual reproduction is impaired by low salinity.


Subject(s)
Biological Evolution , Fucus/physiology , Genetics, Population , Reproduction, Asexual/physiology , Cluster Analysis , Fucus/genetics , Gene Frequency , Microsatellite Repeats/genetics , North Sea , Population Dynamics , Seawater/analysis
8.
Gene ; 231(1-2): 111-20, 1999 Apr 29.
Article in English | MEDLINE | ID: mdl-10231575

ABSTRACT

Cs, a gene with unknown function, and amd and Ddc, which encode decarboxylases, are among the most closely spaced genes in D. melanogaster. Untranslated 3' ends of the convergently transcribed genes Cs and Ddc are known to overlap by 88bp. A number of questions arise about the organization of this tightly-packed gene region and about the evolution and function of the Cs gene. We have now investigated this three-gene cluster in Scaptodrosophila lebanonensis (which diverged from D. melanogaster 60-65 MYA), as well as in D. melanogaster and D. simulans. Gene order and direction of transcription is the same in all three species. The Cs gene codes, in Scaptodrosophila, for a polypeptide of 544 amino acids; in D. melanogaster, it consists of 504 amino acids, which is twice as long as previously suggested, which makes the gene density even more spectacular. The Cs sequences exhibit higher number of non-synonymous substitutions between species, higher ratios of non-synonymous to synonymous substitutions, and lower codon usage bias than other genes, suggesting that Cs is less functionally constrained than the other genes. This is consistent with the failure of inducing phenotypic mutations in D. melanogaster. The function of Cs remains to be identified, but a high degree of similarity indicates that it is homologous to genes coding for a corticosteroid-binding protein in yeast and a polyamine oxidase in maize.


Subject(s)
Drosophila/genetics , Gene Duplication , Insect Proteins/genetics , Multigene Family , Amino Acid Sequence , Animals , Base Sequence , DNA Primers , Female , Molecular Sequence Data , Sequence Homology, Amino Acid
9.
J Mol Evol ; 48(4): 445-62, 1999 Apr.
Article in English | MEDLINE | ID: mdl-10079283

ABSTRACT

We have sequenced most of the coding region of the gene Dopa decarboxylase (Ddc) in 24 fruitfly species. The Ddc gene is quite informative about Drosophila phylogeny. Several outstanding issues in Drosophila phylogeny are resolved by analysis of the Ddc sequences alone or in combination with three other genes, Sod, Adh, and Gpdh. The three species groups, melanogaster, obscura, and willistoni, are each monophyletic and all three combined form a monophyletic group, which corresponds to the subgenus Sophophora. The Sophophora subgenus is the sister group to all other Drosophila subgenera (including some named genera, previously considered outside the Drosophila genus, namely, Scaptomyza and Zaprionus, which are therefore downgraded to the category of subgenus). The Hawaiian Drosophila and Scaptomyza are a monophyletic group, which is the sister clade to the virilis and repleta groups of the subgenus Drosophila. The subgenus Drosophila appears to be paraphyletic, although this is not definitely resolved. The two genera Scaptodrosophila and Chymomyza are older than the genus Drosophila. The data favor the hypothesis that Chymomyza is older than Scaptodrosophila, although this issue is not definitely resolved. Molecular evolution is erratic. The rates of nucleotide substitution in 3rd codon position relative to positions 1 + 2 vary from one species lineage to another and from gene to gene.


Subject(s)
Dopa Decarboxylase/genetics , Drosophila/genetics , Evolution, Molecular , Animals , Base Sequence , DNA , Molecular Sequence Data , Sequence Homology, Nucleic Acid , Species Specificity
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