Zoological Research

675−677

Authors: Li Ma, Jun-Xing Yang, Fa-Kai Lei, Meng-Zhen Xu, Ya-Hui Zhao, William R. Jeffery

 

693−697

Authors: Tao Luo, Qin Yang, Li Wu, Ya-Li Wang, Jia-Jun Zhou, Huai-Qing Deng, Ning Xiao, Jiang Zhou

 

701−711

Authors: Laurent Legendre, Julie Rode, Isabelle Germon, Marie Pavie, Carla Quiviger, Maxime Policarpo, Julien Leclercq, Stéphane Père, Julien Fumey, Carole Hyacinthe, Patricia Ornelas-García, Luis Espinasa, Sylvie Rétaux, Didier Casane

The sizes of Astyanax mexicanus blind cavefish populations of North-East Mexico are demographic parameters of great importance for investigating a variety of ecological, evolutionary, and conservation issues. However, few estimates have been obtained. For these mobile animals living in an environment difficult to explore as a whole, methods based on capture-mark-recapture are appropriate, but their feasibility and interpretation of results depend on several assumptions that must be carefully examined. Here, we provide evidence that minimally invasive genetic identification from captures at different time intervals (three days and three years) can give insights into cavefish population size dynamics as well as other important demographic parameters of interest. We also provide tools to calibrate sampling and genotyping efforts necessary to reach a given level of precision. Our results suggest that the El Pachón cave population is currently very small, of an order of magnitude of a few hundreds of individuals, and is distributed in a relatively isolated area. The probable decline in population size in the El Pachón cave since the last census in 1971 raises serious conservation issues.

725−728

Authors: Yuan-Ting Guo, Yong Shao, Xupeng Bi, Bao-Lin Zhang, Hong Wu, Yang Zhou, Ming-Li Li, Li Yu, Guojie Zhang, Dong-Dong Wu, Xiao-Guang Qi

 

732−736

Authors: Vladislav A. Gorin, Alexey V. Trofimets, Svetlana S. Gogoleva, Le Xuan Dac, Nikolay A. Poyarkov

 

739−742

Authors: Qi-Quan Wang, Xin-Qiang Lan, Xue-Song Wei, Si-Man Xu, Ling-Zhen Liu, Xian-Ling Bian, Lin Zeng, Xiao-Long Guo, Ying-Qi Guo, Wen-Hui Lee, Yang Xiang, Yun Zhang

 

747−749

Authors: Xue-You Li, Wen-Qiang Hu, Hong-Jiao Wang, Xue-Long Jiang

 

761−775

Authors: Marco A.A. Garduño-Sánchez, Vladimir de Jesus-Bonilla, Silvia Perea, Ramses Miranda-Gamboa, Andrea Herrera- García, Mauricio de la Maza Benignos, Claudia Patricia Ornelas-García

Cave-adapted animals provide a unique opportunity to study the evolutionary mechanisms underlying phenotypic, metabolic, behavioral, and genetic evolution in response to cave environments. The Mexican tetra (Astyanax mexicanus) is considered a unique model system as it shows both surface and cave-dwelling morphs. To date, at least 33 different cave populations have been identified, with phylogenetic studies suggesting an origin from at least two independent surface lineages, thereby providing a unique opportunity to study parallel evolution. In the present study, we carried out the most exhaustive phylogeographic study of A. mexicanus to date, including cave and surface localities, using two mitochondrial markers (cytochrome b (cyt b) and cytochrome c oxidase subunit I (COI)) and nuclear rhodopsin visual pigment (rho). Additionally, we inferred the molecular evolution of rho within the two contrasting environments (cave and surface) and across three geographic regions (Sierra de El Abra, Sierra de Guatemala, and Micos). In total, 267 individuals were sequenced for the two mitochondrial fragments and 268 individuals were sequenced for the rho visual pigment from 22 cave and 46 surface populations. Phylogeographic results based on the mitochondrial data supported the two-lineage hypothesis, except for the Pachón and Chica caves, whose introgression has been largely documented. The Sierra de El Abra region depicted the largest genetic diversity, followed by the Sierra de Guatemala region. Regarding the phylogeographic patterns of rho, we recovered exclusive haplogroups for the Sierra de El Abra (Haplogroup I) and Sierra de Guatemala regions (Haplogroup IV). Moreover, a 544 bp deletion in the rho gene was observed in the Escondido cave population from Sierra de Guatemala, reducing the protein from seven to three intramembrane domains. This change may produce a loss-of-function (LOF) but requires further investigation. Regarding nonsynonymous (dN) and synonymous (dS) substitution rates (omega values ω), our results revealed the prevailing influence of purifying selection upon the rho pigment for both cave and surface populations (ω<1), but relaxation at the El Abra region. Notably, in contrast to the other two regions, we observed an increase in the number of dN mutations for Sierra de El Abra. However, given that a LOF was exclusively identified in the Sierra de Guatemala region, we cannot dismiss the possibility of a pleiotropic effect on the Rho protein.

779−781

Authors: Wan-Sheng Jiang, Jie Li, Hong-Mei Xiang, Chao Sun, Jian-Bo Chang, Jun-Xing Yang

 

793−807

Authors: Hong-Yu Chen, Chun-Qing Li, Shan-Yuan Chen, Hen Xiao

Intestinal microbes are closely related to vital host functions such as digestion and nutrient absorption, which play important roles in enhancing host adaptability. As a natural “laboratory”, caves provide an outstanding model for understanding the significance of gut microbes and feeding habits in the habitat adaptability of hosts. However, research on the relationship between gut microbes, feeding habits, and the adaptability of troglobites remains insufficient. In this study, we compared the characteristics of the intestinal microbes of Sinocyclocheilus cavefish and surface fish and further established the relationship between intestinal and habitat microbes. Furthermore, we conducted environmental DNA (eDNA) (metabarcoding) analysis of environmental samples to clarify the composition of potential food resources in the habitats of the Sinocyclocheilus cavefish and surface fish. Results showed that the structure of the Sinocyclocheilus gut microbes was more related to ecological type (habitat type) than phylogenetic relationships. While horizontal transfer of habitat microbes was a source of gut microbes, hosts also showed strong selection for inherent microbes as dominant microorganisms. Differences in the composition and structure of gut microbes, especially dominant microbes, may enhance the adaptability of the two Sinocyclocheilus fish types from the perspectives of food intake, nutrient utilization, and harmful substance metabolism, suggesting that food resources, predation patterns, intestinal flora, digestive and absorptive capacity, and feeding habits and preferences are linked to habitat adaptability. These results should facilitate our understanding of the significance of fish gut microbes to habitat adaptation and provide a new perspective for studying the adaptive mechanisms of cavefish.

821−833

Authors: Mateo Čupić, Zoran Marčić, Marko Lukić, Romana Gračan, Helena Bilandžija

Cave animals are an excellent model system for studying adaptive evolution. At present, however, little is known about the mechanisms that enable surface colonizers to survive in the challenging environment of caves. One possibility is that these species have the necessary genetic background to respond with plastic changes to the pressures of underground habitats. To gain insight into this process, we conducted a comparative study with the fish species Telestes karsticus, which occurs in a hydrological system consisting of an interconnected stream and a cave. Results showed that T. karsticus resided year-round and spawned in Sušik cave, making it the first known cavefish in the Dinaric Karst. Cave and surface populations differed in morphological and physiological characteristics, as well as in patterns of gene expression without any evidence of genetic divergence. To test whether observed trait differences were plastic or genetic, we placed adult fish from both populations under light/dark or constant dark conditions. Common laboratory conditions erased all morphometric differences between the two morphs, suggesting phenotypic plasticity is driving the divergence of shape and size in wild fish. Lighter pigmentation and increased fat deposition exhibited by cave individuals were also observed in surface fish kept in the dark in the laboratory. Our study also revealed that specialized cave traits were not solely attributed to developmental plasticity, but also arose from adult responses, including acclimatization. Thus, we conclude that T. karsticus can adapt to cave conditions, with phenotypic plasticity playing an important role in the process of cave colonization.