Enhanced prey capture skills in Astyanax cavefish larvae are independent from eye loss

Enhanced food-finding efficiency is an obvious adaptive response to cave environments. Here, we have compared the food-finding abilities of Astyanax surface fish and blind cavefish young larvae in their first month of life, in the dark. Our results show that enhanced prey capture skills of cavefish are already in effect in fry soon after the yolk is depleted and the young larvae must find food for themselves. Moreover, using prey capture competition assays on surface fish fry with lensectomies, we showed that eye-dependent developmental processes are not the main determinant for enhanced prey capture skills. Finally, using F2 hybrid larvae resulting from crosses between surface fish and cavefish, we found that reduced eyes do not confer a selective advantage for prey capture by fry in the dark. We discuss these data with regards to our current developmental and genetic understanding of cavefish morphological and behavioral evolution

The First Phylogenetic Analysis of Palpigradi (Arachnida)—The Most Enigmatic Arthropod Order

Palpigradi are a poorly understood group of delicate arachnids, often found in caves or other subterranean habitats. Concomitantly, they have been neglected from a phylogenetic point of view. Here we present the first molecular phylogeny of palpigrades based on specimens collected in different subterranean habitats, both endogean (soil) and hypogean (caves), from Australia, Africa, Europe, South America and North America. Analyses of two nuclear ribosomal genes and COI under an array of methods and homology schemes found monophyly of Palpigradi, Eukoeneniidae, and a division of Eukoeneniidae into four main clades, three of which include samples from multiple continents. This supports either ancient vicariance or long-range dispersal, two alternatives we cannot distinguish with the data at hand. In addition, we show that our results are robust to homology scheme and analytical method, encouraging further use of the markers employed in this study to continue drawing a broader picture of palpigrade relationships.Organismic and Evolutionary Biolog

A Novel Role for Mc1r in the Parallel Evolution of Depigmentation in Independent Populations of the Cavefish Astyanax mexicanus

The evolution of degenerate characteristics remains a poorly understood phenomenon. Only recently has the identification of mutations underlying regressive phenotypes become accessible through the use of genetic analyses. Focusing on the Mexican cave tetra Astyanax mexicanus, we describe, here, an analysis of the brown mutation, which was first described in the literature nearly 40 years ago. This phenotype causes reduced melanin content, decreased melanophore number, and brownish eyes in convergent cave forms of A. mexicanus. Crosses demonstrate non-complementation of the brown phenotype in F2 individuals derived from two independent cave populations: Pachón and the linked Yerbaniz and Japonés caves, indicating the same locus is responsible for reduced pigmentation in these fish. While the brown mutant phenotype arose prior to the fixation of albinism in Pachón cave individuals, it is unclear whether the brown mutation arose before or after the fixation of albinism in the linked Yerbaniz/Japonés caves. Using a QTL approach combined with sequence and functional analyses, we have discovered that two distinct genetic alterations in the coding sequence of the gene Mc1r cause reduced pigmentation associated with the brown mutant phenotype in these caves. Our analysis identifies a novel role for Mc1r in the evolution of degenerative phenotypes in blind Mexican cavefish. Further, the brown phenotype has arisen independently in geographically separate caves, mediated through different mutations of the same gene. This example of parallelism indicates that certain genes are frequent targets of mutation in the repeated evolution of regressive phenotypes in cave-adapted species

Revision of genus Texoreddellia Wygodzinsky, 1973 (Hexapoda, Zygentoma, Nicoletiidae), a prominent element of the cave-adapted fauna of Texas

Espinasa, Luis, Bartolo, Nicole D., Centone, Danielle M., Haruta, Charisse S., Reddell, James R. (2016): Revision of genus Texoreddellia Wygodzinsky, 1973 (Hexapoda, Zygentoma, Nicoletiidae), a prominent element of the cave-adapted fauna of Texas. Zootaxa 4126 (2): 221-239, DOI: 10.11646/zootaxa.4126.2.

Influence of volcanic activity on spring water chemistry at Popocatepetl Volcano, Mexico

The results of the 7 years (1994-2000) of monthly monitoring of spring water before and during eruptions show response to volcanic activity. Low salinity and temperature characterize most of the springs, which are located on the flanks of Popocatepetl Volcano. The pH ranges from 5.8 to 7.8 and temperature from 3 to 36 jC. Oxygen and hydrogen isotopic data show that the water is of meteoric origin, but SO4 2 , Cl , F , HCO3 , B, and SO4 2- /Cl- variations precede main eruptive activity, which is considered linked to influx of magmatic gases and acid fluids that react with sublimates and host rock and mix with the large water system. Na +, Ca2 + , SiO2 and Mg2 + concentrations in the water also increased before eruptive activity. The computed partial pressure of CO2 in equilibrium with spring waters shows values higher than air-saturated water (ASW), with the highest values up to 0.73 bar of pCO2. Boron is detected in the water only preceding the larger eruptions. When present, boron concentration is normally under health standard limits, but in two cases the concentration was slightly above. Other components are within health standard limits, except for F- in one spring.Published207– 229partially_ope

Formation of hybrid arc andesites beneath thick continental crust

Andesite magmatism at convergent margins is essential for the differentiation of silicate Earth, but no consensus exists as to andesite petrogenesis. Models proposing origin of primary andesite melts from mantle and/or slab materials remain in deadlock with the seemingly irrefutable petrographic and chemical evidence for andesite formation through mixing of basaltic mantle melts with silicic components from the overlying crust. Here we use <sup>3</sup>He/<sup>4</sup>He ratios of high-Ni olivines to demonstrate the mantle origin of basaltic to andesitic arc magmas in the central Mexican Volcanic Belt (MVB) that is constructed on ~ 50 km thick continental crust. We propose that the central MVB arc magmas are hybrids of high-Mg# > 70 basaltic and dacitic initial mantle melts which were produced by melting of a peridotite subarc mantle interspersed with silica-deficient and silica-excess pyroxenite veins. These veins formed by infiltration of reactive silicic components from the subducting slab. Partial melts from pyroxenites, and minor component melts from peridotite, mix in variable proportions to produce high-Mg# basaltic, andesitic and dacitic magmas. Moderate fractional crystallization and recharge melt mixing in the overlying crust produces then the lower-Mg# magmas erupted. Our model accounts for the contrast between the arc-typical SiO<sub>2</sub> variability at a given Mg# and the strong correlation between major element oxides SiO<sub>2</sub>, MgO and FeO which is not reproduced by mantle–crust mixing models. Our data further indicate that viscous high-silica mantle magmas may preferentially be emplaced as intrusive silicic plutonic rocks in the crust rather than erupt. Ultimately, our results imply a stronger turnover of slab and mantle materials in subduction zones with a negligible, or lesser dilution, by materials from the overlying crust