Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Nelsonia is a genus of rodent endemic to Mexican highlands with only two species: N. neotomodon (Western diminutive woodrat) and N. goldmani (Goldman´s diminutive woodrat).  These species are taxonomically interesting because the few internal and external morphological differences were reported between them.  Unfortunately, the scarcity of specimens and preserved internal organs available of these species limits the information to perform taxonomic studies.  Hence, the objective of this study was to describe the reproductive structures in one specimen of N. goldmani collected in the biogeographic region known as Transmexican Volcanic Belt, located in the highlands of the central Mexico.  We describe the external structures of the phallus and take nine measurements.  The baculum was measured and described after using the classical methodology to clear, stain and preserve the whole phallus.  The spermatozoa and inner testes were described using light microscopy, scanning electron microscopy, and histological techniques.  Testicular volume was 319.64 mm3 and 1.34% of gonad somatic index.  The phallus was relatively simple externally, laterally cylindrical, and dorsally resembling an elongated bottleneck.  The baculum is an osseous structure with a cartilaginous part in its distal section.  The sperm has a total mean length of 182.58 µm with an asymmetric head, a slight depression in its base and a large recurved hook.  The histological analysis of testes indicated active spermatogenesis.  We found important differences in the features and form of the phallic and baculum between N. neotomodon and N. goldmani.  In N. goldmani some phallic forms were different, and some features measurements were greater than N. neotomodon.  The external structures and the internal position of the baculum differ between the two species.  In addition, the sperm size in N. goldmani was greater than other rodents, even those of larger corporal size like some species phylogenetically close as Neotoma genus.

Shrews (Eulipotyphla: Soricidae) are amongst the most diverse and widely distributed groups of small mammals worldwide. In Mexico, more than 40 species of the genera Sorex, Cryptotis, Megasorex, and Notiosorex have been documented. There is little knowledge about epizoic arthropods of shrews, with 40 species recorded, 28 corresponding to the subclass Acari, and 12 to Insecta. Sorex oreopolus Merriam, 1892, is an endemic species of Mexico, distributed from southwest Jalisco to east Puebla and west Veracruz. This study reports the first records of epizoic arthropods of S. oreopolus. Five specimens of S. oreopolus were collected during 2016 from four sites at La Malinche National Park, state of Tlaxcala. Epizoic arthropods were removed from the pelage of shrews and processed for identification. For each species found in S. oreopolus, ecological parameters of infestation were calculated; for parasitic species, also the degree of host specificity was estimated. A total of 1,194 arthropods were found, corresponding to six mite and one insect taxa. All are new records for this host species. The mites Orycteroxenus soricis (Oudemans 1915) and Pygmephorus horridus Mahunka, 1973 are recorded for the first time in Mexico. The prevalence and abundance of O. soricis was high, while Corrodopsylla lira Traub, 1950 is less prevalent/abundant (Table 1). Epizoic arthropods comprise commensals (Myobiidae), temporary ectoparasites (Trombiculidae) and (Ctenophthalmidae), and phoretic (Glycyphagidae and Pygmephoridae). Seven taxa of epizoic arthropods recorded in this study represent the first record of association with S. oreopolus. The mites O. soricis and P. horridus had already been documented on shrews of the genus Sorex; however, they are recorded for the first time in Mexico, increasing the richness of symbionts of Mexican shrews from 40 to 42 species. Further investigations on the richness of arthropods associated with Mexican shrews are needed, as only seven of 40 species of shrews have been documented, representing 20 % of hosts.

Some rodents of the family Heteromyidae can survive without drinking water, as they obtain it from food.  All these species have in common that they eat seeds and fruits. The content of trace metals in food varies depending on the local geology and anthropogenic activities.  Baja California Sur has mineral deposits that have been exploited; thus, the metals released may be incorporated into seeds and fruits that are consumed by Heteromyidae.  Therefore, metal content in the liver is expected to reflect the presence of mining in soil where these rodents thrive.  Individuals from different species of Heteromyidae were collected at sites with mineral deposits; these were divided into two groups:  rodents captured in sites with a history of mining operations (Santa Rosalia, San Juan de la Costa, and El Triunfo), and rodents captured in areas with no mining activities (El Vizcaíno, Punta Abreojos, Magdalena Island, and Santiago).  The liver of these rodents was excised and its manganese, copper, cadmium, lead, zinc, nickel, and iron contents were determined using atomic absorption spectrophotometry.  Manganese was the element that showed the highest significant differences between species, followed by zinc and copper.  Iron and cadmium showed the lowest differences.  Nickel and lead showed no differences.  Chaetodipus arenarius showed significant differences between sites in copper and lead content; C. spinatus did not show significant differences for manganese, copper, nickel, and iron, but it did for cadmium and lead content.  Differential accumulation of metals occurs across species.  These results indicate that the same species could be used for comparative purposes in pollution monitoring.  The comparison of different heteromid species, despite their sharing similar feeding habits and belonging to the same family, can lead to misinterpretation due to the variability of the results.  This is probably due to the requirements and tolerances regarding essential elements, such as manganese and zinc, to or tolerance to non-essential elements such as cadmium and lead, which may vary across species.

Baird’s tapir is the largest Neotropical tapir species, and it is considered Endangered by the IUCN.  The Calakmul Biosphere Reserve (CBR) is the largest protected tropical forest in Mexico.  The CBR is at the heart of the Maya Forest, a tri-national forest located in Mexico, Guatemala, and Belize that is the largest tropical forest outside the Amazon River basin.  Free-standing water in the CBR occurs in only a few ephemeral ponds.  These ponds are rare in the landscape, with a mean density of one pond in every 10 km2, and with an average distance among ponds of 3 km.  Only some of these ponds have free-standing water in every year.  A decreasing trend in water availability from these ponds was detected from 2008 to 2018.  Our present objective was to document population of the tapirs during these 11 years, and reveal any relationship to the pattern of water availability.  Using the technique of photo-trapping, we monitored from 9 to 15 ponds over a period of 8 years (a total of more than 18,000 camera-days) during the 11-year period.  Results showed that although the population remained relatively stable, the index of relative abundance indicated a slight decrease in population abundance and in some sites seemed at least superficially associated with decreasing water availability.  Such long-term population studies are becoming more important for estimating the impacts of possible changes and for predicting the future of populations.  In turn, they assist the conservation of endangered and sensitive species such as Baird’s tapir.

Corrigendum

Understanding the factors shaping the niche of parasites and its expression over geographical space and through time continues to be a modern scientific challenge with the results of research in this area directly influencing both theoretical and applied biology. This is especially important for proactive management of zoonotic parasites such as Echinococcus multilocularis, the etiologic agent of alveolar echinococcosis. Echinococcus multilocularis has a Holarctic distribution; with its geographic range and prevalence increasing recently in areas of the western Palearctic, while its distribution dynamics are poorly understood in the Nearctic. In this paper, we use an ecological niche modeling (ENM) approach to: i) estimate the current spatial distribution of suitable conditions for the parasite in the Nearctic. ii) Evaluate the abiotic and biotic factors influencing the species distribution. iii) Assess the potential impact of climatic change on the distribution of this species in the Nearctic. Additionally, we report two new occurrence records of this parasite that significantly expands its known geographic range. We reviewed the occurrence records of E. multilocularis for the Nearctic. This was complemented by two new records of the species from Maryland and New Mexico identified using morphology and multivariate morphometrics of the rostellar hooks. From these data we created two ENMs using the software Maxent. The first ENM included climatic variables, while the second included the same abiotic data plus biotic information consisting of four host community-related data sets. We evaluated model performance and variable importance to explore the relation of these variables to the parasite niche. Finally, we projected the resulting niche model onto future climate change scenarios. We found that an important portion of the Nearctic has suitable conditions for E. multilocularis with adequate habitat in the West and East of the continent where the parasite has not been detected. We also found that the proposed biotic variables improve the model performance and provide unique information, while the most critical abiotic variable was related to the amount of solar radiation. Finally, under the future emission scenarios explored, the distribution of suitable habitat for the parasite is predicted to increase by 56 % to 76 %. We obtained a robust model that provides detail on the distribution of suitable areas for E. multilocularis, including areas that have not been explored for the presence of the parasite. The host community variables included in this study seem a promising way to include biotic data for ecological parasite niche modeling.

The genus Leptospira encompasses ten species of spirochetes capable of infecting mammals, particularly rodents. In Mexico, studies focused on the detection of Leptospira sp. in rodents are scarce, all of them restricted to three states of the Gulf of Mexico. For this reason, this work aimed to identify the diversity of Leptospira species associated with synanthropic rodents in Veracruz, a state where leptospirosis is endemic.  Rodents were sampled with Sherman traps placed in 10 Production Units across the Nautla region. Animals were euthanized and their kidneys removed. Subsequently, a 474-bp segment of the outer membrane protein LipL32, present in all pathogenic species, was amplified and sequenced. Sequences were compared vs. reference using the BLAST algorithm: a phylogenetic reconstruction was carried out using the Maximum Likelihood method.  In addition, the prevalence of infection in each Production Unit was estimated.  Twenty eight rodents of a single species (Mus musculus) were caught. Leptospira DNA was detected in 17 samples (62.9 %, CI95 % 42.3 to 80.6) from seven localities in the Nautla region. The sequences recovered exhibited 99-100% identity to each other and 99 % identity with Leptospira borgspetersenii sequences deposited in GenBank.  This study confirms the presence of L. borgspetersenii in rodents, particularly in M. musculus, in Mexico.  This study increases the inventory of pathogenic leptospires for the state of Veracruz to three species. 

Chewing lice (Phthiraptera: Trichodectidae) and the pocket gophers (Rodentia: Geomyidae) that they inhabit have shared an intimate historical association that has made them a textbook study for cophylogeny. Herein, we examine the chewing lice found on pocket gophers of the Cratogeomys fumosus species group using DNA sequence data from the mitochondrial cytochrome c oxidase subunit I gene to determine relationships among lice for comparison to published host phylogeny. Although matrix approaches indicate a correlation between host and parasite genetic distances, cophylogenetic reconstruction methods fail to detect a pattern of widespread cophylogeny. In conclusion, this study provides an exception to the rule of host-parasite cophylogeny that could be the result of the young age of the relationships considered herein and the complex history of the Trans-Mexican Volcanic Belt.

The knowledge of the helminth parasites of Canis latrans from Mexico is scarce.  This study 23 scats of C. latrans were collected and examined to identify alimentary items between April and September of 2018, at the rancho experimental Teseachi of the Universidad Autónoma de Chihuahua, in Namiquipa, Chihuahua, México.  Three nematode specimens of Physaloptera sp. were found and identified by morphology.  This endoparasite is reported for the first time in scats of C. latrans for the state of Chihuahua.