Evolution and development in cave animals: from fish to crustaceans

Cave animals are excellent models to study the general principles of evolution as well as the mechanisms of adaptation to a novel environment: the perpetual darkness of caves. In this article, two of the major model systems used to study the evolution and development (evo–devo) of cave animals are described: the teleost fish Astyanax mexicanus and the isopod crustacean Asellus aquaticus. The ways in which these animals match the major attributes expected of an evo–devo cave animal model system are described. For both species, we enumerate the regressive and constructive troglomorphic traits that have evolved during their adaptation to cave life, the developmental and genetic basis of these traits, the possible evolutionary forces responsible for them, and potential new areas in which these model systems could be used for further exploration of the evolution of cave animals. Furthermore, we compare the two model cave animals to investigate the mechanisms of troglomorphic evolution. Finally, we propose a few other cave animal systems that would be suitable for development as additional models to obtain a more comprehensive understanding of the developmental and genetic mechanisms involved in troglomorphic evolution

Influencia da densidade populacional sobre o desempenho de leitoes criados em baias ou gaiolas.

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Quando usar cama de aviário para suínos.

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Embryonic origin and genetic basis of cave associated phenotypes in the isopod crustacean Asellus aquaticus.

Characteristics common to animals living in subterranean environments include the reduction or absence of eyes, lessened pigmentation and enhanced sensory systems. How these characteristics have evolved is poorly understood for the majority of cave dwelling species. In order to understand the evolution of these changes, this study uses an invertebrate model system, the freshwater isopod crustacean, Asellus aquaticus, to examine whether adult differences between cave and surface dwelling individuals first appear during embryonic development. We hypothesized that antennal elaboration, as well as eye reduction and pigment loss, would be apparent during embryonic development. We found that differences in pigmentation, eye formation, and number of segments of antenna II were all present by the end of embryonic development. In addition, we found that cave and surface hatchlings do not significantly differ in the relative size of antenna II and the duration of embryonic development. To investigate whether the regions responsible for eye and pigment differences could be genetically linked to differences in article number, we genotyped F2 hybrids for the four previously mapped genomic regions associated with eye and pigment differences and phenotyped these F2 hybrids for antenna II article number. We found that the region previously known to be responsible for both presence versus absence of pigment and eye size also was significantly associated with article number. Future experiments will address whether pleiotropy and/or genetic linkage play a role in the evolution of cave characteristics in Asellus aquaticus

Farinha de carne e ossos bovina e suína como fonte de proteína para suínos.

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Farinha de carne e ossos bovina e suína como fonte de proteína para suínos em crescimento e terminação.

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Regressive Evolution in the Mexican Cave Tetra, Astyanax mexicanus

Cave adapted animals generally have reduced pigmentation and eyes, but the evolutionary forces driving the reductions are unknown; Darwin famously questioned the role of natural selection in eye loss in cave fishes; “As it is difficult to imagine that eyes, although useless, could be in any way injurious to animals living in darkness, I attribute their loss wholly to disuse” [1]. We studied the genetic basis of this phenomenon in the Mexican cave tetra, Astyanax mexicanus, by mapping the quantitative trait loci (QTL) determining differences in eye/lens sizes and melanophore number between cave and surface fish. In addition, we mapped QTL for the putatively constructive traits of jaw size, tooth number, and numbers of taste buds. The data suggest that eyes and pigmentation regressed through different mechanisms. Cave alleles at each eye/lens QTL we detected caused size reductions. This uniform negative polarity is consistent with evolution by natural selection and inconsistent with evolution by drift. In contrast, QTL polarities for melanophore number were mixed, consistent with evolution by genetic drift or indirect selection through pleiotropy. Past arguments against a role for selection in regression of cave fish eyes cited the insignificant cost of their development [2,3], but we argue that the energetic cost of their maintenance is sufficiently high for eyes to be detrimental in the cave environment. Regression, a ubiquitous aspect of all evolutionary change, can be caused either by selection or genetic drift/pleiotropy

Comparação de rações de custo mínimo para frangos de corte, formuladas a partir de tabela nacional e estrangeira.

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Surgical site infection among patients undergone orthopaedic surgery at Muhimbili Orthopaedic Institute, Dar es Salaam, Tanzania

Background: The aim of this study was to determine prevalence and factors associated with surgical site infection at Muhimbili Orthopedic Institute.Method: This was a cross-sectional study conducted at Muhimbili Orthopaedic Institute (MOI) in Dar es Salaam, from August, 2015 to October 2015. Convenience sampling technique was used to recruit postoperative patients for this study. Standardized questionnaires were used to obtain demographic, social, and clinical information from respondents. Determination of the relationship between outcome and exposure variables was done using chi square test. Multivariate logistic regression was used to measure the association after controlling for confounders. Odds ratio corresponding to 95% confidence interval with a p value of ≤ 0.05 was considered significant.Results: Out of 300 study participants 75(25.0%) had surgical site infection. This was highly determined by more than 2 hours length of surgical procedure (AOR= 1.4; 95%CI 1.14-6.69; P value=0.05), none prophylactic use of antibiotics (AOR= 3.4; 95%CI 1.6-7.78; P value=0.03), more than one week stay before surgery (AOR=3.3; 95%CI 2.24-3.34; P value =0.00).Conclusion: The overall prevalence of surgical site infection at Muhimbili Orthopedic Institute was high. This was associated with more than 2 hours length of surgery, lack of prophylaxis use, and pre-operative hospital stay

Developmental Transcriptomic Analysis of the Cave-Dwelling Crustacean, Asellus aquaticus

Cave animals are a fascinating group of species often demonstrating characteristics including reduced eyes and pigmentation, metabolic efficiency, and enhanced sensory systems. Asellus aquaticus, an isopod crustacean, is an emerging model for cave biology. Cave and surface forms of this species differ in many characteristics, including eye size, pigmentation, and antennal length. Existing resources for this species include a linkage map, mapped regions responsible for eye and pigmentation traits, sequenced adult transcriptomes, and comparative embryological descriptions of the surface and cave forms. Our ultimate goal is to identify genes and mutations responsible for the differences between the cave and surface forms. To advance this goal, we decided to use a transcriptomic approach. Because many of these changes first appear during embryonic development, we sequenced embryonic transcriptomes of cave, surface, and hybrid individuals at the stage when eyes and pigment become evident in the surface form. We generated a cave, a surface, a hybrid, and an integrated transcriptome to identify differentially expressed genes in the cave and surface forms. Additionally, we identified genes with allele-specific expression in hybrid individuals. These embryonic transcriptomes are an important resource to assist in our ultimate goal of determining the genetic underpinnings of the divergence between the cave and surface forms