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Located in the Basin of Mexico, the eastern shore of former Lake Texcoco sustained a variety of human occupations throughout the Holocene, including preceramic hunter‐gatherers, incipient agriculturalists, and a variety of settlements in the ceramic periods. Nonetheless, the environmental dynamics of occupations on the lakeshore have not been fully addressed. The Archaic preagricultural Texcoco Man site (>5000 B.C.E.) and the Late Formative TX‐LF‐14 site (c. 550‐200 B.C.E.), among others, occupy this fluvio‐lacustrine transitional environment. Few stratigraphic works in and around the sites have been performed. Consequently, it is difficult to understand the dynamics of the sedimentary system in space and time. This work highlights and describes the fluvio‐lacustrine sedimentary dynamics and the resulting landscape that past societies inhabited on the eastern shore of Texcoco Lake. Because the study area has been altered by historic and modern draining, our work employs Lake Santiaguillo and its main tributary, the Tejamen River in the Durango state, as a modern analog to study their sedimentary dynamics. The analyses of surface geomorphology in the Texcoco study area were employed to corroborate the modern analog interpretation. To achieve these goals, we conducted a GIS‐based morphometric analysis and LANDSAT‐8 imagery to study the variations in landforms through wet and dry events. The results indicate an increase in the lake volume, low bifurcation in the active fluvial channels, few inundated surfaces, and the presence of bird‐foot deltaic channels during high precipitation events. In contrast, low precipitation events are characterized by reduced lake volume, increased fluvial channel bifurcation, and expanded floodplains. This heterogeneous landscape thus provided a rich source of diverse natural resources of saline and freshwater aquatic habitats. Simultaneously, constant or recurring flooding events generated a challenging landscape for prehistoric settlers who implemented diverse technologies, such as the construction of tlateles, on the levees of deltaic channels to reduce the risk and impact of flooding events. [ABSTRACT FROM AUTHOR]

Myxozoans are a unique group of microscopic parasites that infect mainly fishes. These extremely reduced cnidarians are highly diverse and globally distributed in freshwater and marine habitats. Myxozoan diversity dimension is unknown in Mexico, a territory of an extraordinary biological diversity. This study aimed to explore, for the first time, myxozoan parasite diversity from fishes of the Neotropical region of Mexico. We performed a large morphological and molecular screening using host tissues of 22 ornamental and food fish species captured from different localities of Veracruz, Oaxaca and Chiapas. Myxozoan infections were detected in 90% of the fish species, 65% of them had 1 or 2 and 35% had 3 and up to 8 myxozoan species. Forty-one putative new species were identified using SSU rDNA phylogenetic analyses, belonging to two main lineages: polychaete-infecting (5 species) and oligochaete-infecting (36 species) myxozoans; from those we describe 4 new species: Myxidium zapotecus sp. n., Zschokkella guelaguetza sp. n., Ellipsomyxa papantla sp. n. and Myxobolus zoqueus sp. n. Myxozoan detection increased up to 6 × using molecular screening, which represents 3.7 × more species detected than by microscopy. This study demonstrated that Neotropical fishes from Mexico are hosts of a multitude of myxozoans, representing a source of emerging diseases with large implications for economic and conservation reasons. [ABSTRACT FROM AUTHOR]

Planarian flatworms are best known for their impressive regenerative capacity, yet this trait varies across species. In addition, planarians have other features that share morphology and function with the tissues of many other animals, including an outer mucociliary epithelium that drives planarian locomotion and is very similar to the epithelial linings of the human lung and oviduct. Planarians occupy a broad range of ecological habitats and are known to be sensitive to changes in their environment. Yet, despite their potential to provide valuable insight to many different fields, very few planarian species have been developed as laboratory models for mechanism-based research. Here we describe a previously undocumented planarian isolate, Girardia sp. (Guanajuato). After collecting this isolate from a freshwater habitat in central Mexico, we characterized it at the morphological, cellular, and molecular level. We show that Girardia sp. (Guanajuato) not only shares features with animals in the Girardia genus but also possesses traits that appear unique to this isolate. By thoroughly characterizing this new planarian isolate, our work facilitates future comparisons to other flatworms and further molecular dissection of the unique and physiologically-relevant traits observed in this Girardia sp. (Guanajuato) isolate. [Display omitted] • G. sp (Guanajuato) is a new planarian isolate collected in Mexico. • G. sp (Guanajuato) is largely asexual and highly regenerative. • G. sp (Guanajuato) displays a unique mode of locomotion. • Head regeneration in G. sp (Guanajuato) is less robust than in S.mediterranea. • G. sp (Guanajuato) animals and their piwi-1+ stem cells exhibit increased radiation tolerance compared to S.mediterranea. [ABSTRACT FROM AUTHOR]

Beta diversity is useful to explain community assembly across landscapes with spatial variation. Its turnover and nestedness components help explain how beta diversity is structured across environmental and spatial gradients. Assessing beta diversity in freshwater ecosystems is essential to conservation, as it reveals the mechanisms that maintain regional diversity. Nonetheless, so far, no studies have examined the beta diversity patterns of benthic macroinvertebrates in tropical lakes. We aimed to examine the beta diversity patterns and components of the deep benthic macroinvertebrate communities of tropical Lakes of Montebello, Mexico, along spatial and environmental gradients. We used presence/absence data of deep benthic macroinvertebrates from 13 lakes distributed along environmental and spatial gradients. We calculated beta diversity indices and correlated them to each lake's environmental and spatial variables. The macroinvertebrate communities of the Lakes of Montebello showed high beta diversity driven by a turnover pattern that emphasises the importance of regional-scale conservation efforts. Short distances between lakes and high environmental heterogeneity promoted species turnover, resulting in a great singularity level among lakes. We did not find significant correlations between the beta diversity components and the environmental variables, suggesting a random distribution given by the species' high dispersal capacity in a reduced spatial extent across the lake district. [ABSTRACT FROM AUTHOR]

The common snook (C. undecimalis) is a highly valuable commercial and sport fishing species in marine, estuarine, and freshwater habitats. Despite its abundance in freshwater ecosystems, the information on the reproductive biology comes mainly from studies in the marine habitat. In this work, the reproductive cycle at the gametogenic and hormonal level is addressed in specimens captured in contrasting environments interconnected by the Grijalva-Usumacinta fluvial system. Adult common snook presented a similar temporal pattern in sex steroid concentrations in both environments. Likewise, females and males were observed undergoing advanced maturity simultaneously in both environments. However, females in the freshwater environment did not reach final maturation, and no post-ovulatory follicles were found, indicating that spawn did not happen. Therefore, organisms are synchronized with gonads developing in both habitats, implying migrations of at least 300 km from the freshwater environment to the spawning grounds in the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

The Laguna Madre-Tamaulipas is the world's largest hypersaline lagoon and is equally located in south Texas, USA, and Tamaulipas, Mexico. Over 40% of its American surface area is covered by wind-tidal sand flats containing cyanobacteria as the major autotrophic component of the microbial community. A recent laboratory examination of these microbial mats revealed the presence of a boring, filamentous cyanobacterium which, in culture, 'drilled' through an agar substrate. The observed clockwise/counterclockwise rotation, gliding, and boring ability of the filaments was atypical for any known cyanobacterium. The isolate from Laguna Madre produces nine toxins that were originally described from both marine and freshwater habitats. Presence of a diverse array of bioactive metabolites in our unialgal culture agrees with earlier work demonstrating diverse toxin production by marine cyanobacteria. Initial comparison of this new taxon with its polyphasically closest genus, Oxynema, showed several morphological, physiological, and phylogenetic differences, warranting establishment of a new family Laspinemaceae, containing Perforafilum tunnelli gen. & sp. nov. [ABSTRACT FROM AUTHOR]

The article reports on the study which found barnacles on the American crocodile, Crocodylus acutus, in a population from the Central Pacific Coast of Mexico. It shows that the total length of crocodiles with barnacles ranged from 72.2 to 150 centimeters. It suggests that the low percentage of crocodiles with barnacles could be related to ontogenetic shifts in habitat use, indicating that crocodiles prefer freshwater habitats, but can survive in rackish conditions.

The population morphometric variation of the endangered freshwater killifish ( Fundulus lima) was evaluated and compared with that of its euryhaline coastal relatives ( F. parvipinnis parvipinnis and F. p. brevis) on the basis of 384 specimens from the Baja California peninsula, Mexico. Forty five standardized body distances were compared by means of discriminant function analysis (DFA). Sixteen body distances were significant to distinguish two groups of populations for F. lima: a first group represented by the Bebelamas and San Javier basins, and second group composed by the basins of San Ignacio, La Purísima, San Luis, San Pedro and Las Pocitas. When all freshwater and coastal populations were compared, the southernmost population of F. lima (Las Pocitas) showed a higher morphometric similarity with the southern coastal subspecies ( F. p. brevis), while another southern population (San Pedro) had an intermediate position between the freshwater and coastal forms. This study suggests the presence of five evolutionary units (three freshwater and two coastal) for the genus Fundulus in the Baja California peninsula. [ABSTRACT FROM AUTHOR]

The diversity of freshwater zooplankton is still little known in Mexico, particularly in reference to insular zooplankton communities. Diaptomid copepods (Crustacea: Copepoda: Calanoida) are a widespread group worldwide, and Mexico harbours high diaptomid diversity. Based on a recent sampling of freshwater zooplankton on a Caribbean Island of Mexico, we present the first record of a diaptomid copepod from an island freshwater ecosystem. It shows the well-known tendency of Neotropical diaptomids to have restricted distributional patterns and high levels of endemism. The species recorded, Mastigodiaptomus ha (Cervantes-Martínez, 2020) appears to have a restricted distribution in the Yucatan Peninsula (YP), and the island as well. In order to explore potential differences between the island and continental populations of this species, its phenetic and genetic diversity was analysed by performing morphological comparisons and also by exploring differences of the habitat conditions and genetic sequences (CO1 gene). Our analysis revealed a low (average = 0.33%) genetic divergence between both populations; likewise, both the morphology and habitat conditions closely resemble each other in these two populations. The low genetic divergence between the continental and island populations of M. ha suggests an early common origin of the species in the geological history of the YP. [ABSTRACT FROM AUTHOR]

The authors discuss aspects of aquatic habitats and the state of aquaculture in Mexico. They refer to the abundant and diverse freshwater, brackish, and marine ecosystem for the cultivation of fishes, mollusks, and crustaceans. The authors think that shrimp raising is the most important aquatic resources in the aquaculture industry of Mexico.