Peninsula Of Mexico Research Articles

Nonselective Diatom Grazing By Juveniles of Red Abalone (Haliotis rufescensSwainson, 1822) Under Experimental Culture Conditions

In abalone farms and laboratories of the Baja California peninsula in Mexico, young and postlarval abalone feed on benthic diatoms that grow on the artificial surfaces of the culture tanks, or on epiphytic diatoms growing on kelp (Macrocystis pyrifera) blades provided when a change in their diet is estimated. It is not known whether grazing selectivity occurs by postlarvae and young abalones at this time. Thus, experiments were conducted to determine whether discrimination by juveniles of red abalone (Haliotis rufescens) occurs while grazing on diatoms that grow on the rocks and kelp blades extracted from their habitat, and to determine whether the ingested diatoms are, indeed, digested. Our hypothesis was that juveniles of H. rufescens would feed nonselectively on the diatom films; thus, the characteristics of the diatom assemblages (species composition, diversity) from their gut contents should be similar to those upon which they feed. We also expected that the smaller forms of diatoms would pass through the digestive tract intact. Overall, 171 diatom taxa were identified: 123 in the tank walls, 35 on the rocks, 143 in the gut contents, and 38 in the feces. Only Amphora pediculus appeared in all the gut contents examined; however, 12 taxa accounted for 80% of the relative abundance (n = 500). Highest diversity ( = 4.46) was measured in the walls of a tank where M. pyrifera was included, but abalone specimens from this tank showed the lowest H' value in their gut contents. The hypothesis that grazing by young H. rufescens is nonselective is supported, as well as the importance of the structure of the diatom assemblage grazed upon (as in H. fulgens), which is reflected in their gut contents. Moreover, feces analysis showed that many small diatoms that are ingested are not digested, and are able to reproduce and grow after passing through the digestive tract.

Higher Seroprevalence ofTrypanosoma cruziInfection in Dogs Than in Humans in an Urban Area of Campeche, Mexico

The reservoir capacity of dogs for Trypanosoma cruzi infection was analyzed in the city of Campeche, an urban town located in the Yucatan peninsula in Mexico. The city is inhabited by ~96,000 dogs and ~168,000 humans; Triatoma dimidiata is the only recognized vector. In the present study, we sampled 262 dogs (148 stray dogs and 114 pet dogs) and 2800 young people (ranging in age between 15 and 20 years old) and tested for T. cruzi antibodies by enzyme-linked immunosorbent assay, Indirect Immunofluorescence, and Western blotting serological assays. Seroprevalence in stray dogs was twice higher than in pet dogs (9.5% vs. 5.3%) with general seroprevalence of 7.6%. In humans, the observed seroprevalence was 76 times lower than in dogs (0.1% vs. 7.6%, respectively). Western blotting analysis showed that dogs' antibodies recognized different T. cruzi antigenic patterns than those for humans. In conclusion, T. cruzi infection in Campeche, Mexico, represents a low potential risk to inhabitants but deserves vigilance.

Characterization of limestones for building in the Yucatan Peninsula, Mexico

The environmental degradation of red and white limestone exposed to a rural tropical atmosphere of the Yucatan Peninsula in Mexico was characterized during seven years using gravimetric measurements, SEM, EDX and X-ray diffraction techniques. The results showed that the red limestone dissolves faster than the white. However, they do not change significantly their bulk chemical composition, suggesting that the degradation occurs mainly by disaggregation of the calcite grains and alveolarization. Minor traces of crystalline phases of several iron oxides in the limestone might promote the decay process. Mathematical relationships are proposed to describe the kinetics of degradation, giving insight in the rate of degradation in future time.

Morfometría en la cuenca hidrológica de San José del Cabo, Baja California Sur, México

La cuenca hidrológica-forestal de San José del Cabo, localizada al sur de la península de Baja California, México, es la de mayor extensión en el estado de Baja California Sur y es considerada como una de las principales fuentes de recursos hídricos. Los acuíferos que suministran agua a las áreas turísticas y urbanas están en las partes bajas (planicies aluviales) de la cuenca. Un complejo cristalino constituido por rocas ígneas y metamórficas caracteriza la región montañosa de la cuenca. Análisis de imagen Landsat ETM, fotografías aéreas y modelo digital de elevación fueron usados para cartografiar la geomorfología, geología y desarrollar un análisis morfométrico en la margen occidental de la cuenca. Rasgos estructurales tales como alineamientos rectos o curvilíneos y diques fueron obtenidos del modelo digital de elevación. Parámetros morfométricos y análisis estructural de siete subcuencas se derivaron para determinar áreas potenciales de captura hacia la Cuenca Hidrológica de San José del Cabo (CHSJC). Del análisis se identificó que la captura toma lugar en la parte serrana de la cuenca, dentro del basamento cristalino a través de un sistema de fracturamiento interconectado. Se proponen dos subcuencas como las principales áreas de recarga hacia la CHSJC. Los resultados muestran que la investigación con imagen Landsat y el modelo digital de elevación proporcionan, una fuente acertada de datos e información para la identificación de áreas de recarga y descarga a una escala regional.

Application of Lu–Hf garnet dating to unravel the relationships between deformation, metamorphism and plutonism: An example from the Prince Rupert area, British Columbia

The tectonic history of the Prince Rupert area is marked by profound crustal thickening from thrusting that produced inverted metamorphic field gradients and transpression in crustal-scale shear zones. Syn-tectonic garnet in the Prince Rupert area has Lu–Hf ages of 102.6 ± 3.7 Ma and 108.3 ± 4.1 Ma (2 σ). Porphyroblast–matrix relationships in these samples, and samples from the same outcrops, indicate syn-tectonic garnet growth. These relationships imply that the garnet ages directly date the development of the metamorphic foliations. A third sample of migmatitic garnet amphibolite from the contact aureole of the 94–90 Ma Ecstall pluton had complex isotope systematics interpreted to indicate a garnet growth episode ∼ 105 Ma, similar to the ages obtained from the other samples and a growth or equilibration event at ∼ 94 Ma during pluton emplacement. The data show that the older Lu–Hf garnet ages date prograde metamorphism during foliation development and modification during pluton emplacement. The Ecstall pluton was emplaced 10 to 15 m.y. after regional metamorphism and thrust stacking in the Prince Rupert area. In order to place our samples in a regional tectonic context we compare our results to patterns of regional deformation, metamorphism and plutonism throughout the North American Cordillera in the time period between 110 and 85 Ma. Contractional and transpressional deformation occurred throughout much of the North American Cordillera at this time, from southeastern Alaska to the Baja Peninsula in Mexico. Left-lateral transpression dominated the Canadian Cordillera, whereas, right-lateral transpression affected areas south of the Idaho–Salmon River suture zone, including the Sierra Nevada batholith. This reversal in kinematics in the northern and southern cordillera within coeval magmatic belts appears to be a first-order feature of the geology of the North American Cordillera during the Cretaceous.

Monoamine fluctuations during the reproductive cycle of the Pacific lion's paw scallop Nodipecten subnodosus

The Pacific lion's paw scallop Nodipecten subnodosus has been one of the most important commercial species of mollusc in the Baja California peninsula in Mexico since 1990. This species is a functional hermaphrodite with tropical and sub-tropical distributions and experiences wide annual temperature oscillations influencing its physiological functions. We determined norepinephrine (NE), dopamine (DA), and serotonin (5-HT) concentrations in different organs (female and male gonads, digestive gland, adductor muscle, gill, mantle, and foot) of N. subnodosus, at 6 reproductive stages (resting, initial, maturing, mature, partially spent and fully spent). Monoamine concentrations were determined by HPLC fitted with an electrochemical detector. Results indicated that monoamine concentrations increased during maturing stage, peaked at mature stage and declined after spawning. NE concentrations were higher than the rest of monoamines followed by DA, and 5-HT. NE was present in all organs at all reproductive stages. DA concentrations were higher in the gill and digestive gland during all stages. 5-HT was only detectable in the male gonadic portion at all stages except at spent stage. NE was the most abundant neurotransmitter found in the female gonad of N. subnodosus, while 5-HT was the most abundant neurotransmitter found in the male gonad. Furthermore, these two neurotransmitters accumulated in the respective gonad tissues during the initial reproductive stages I to IV and then declined after spawning (stages V and VI). This suggests that this species utilized different neurotransmitters specific for each gender and that this utilization was related to the reproductive cycle.

Evaluation of the Wind Shear at a Site in the North-West of the Yucatan Peninsula, Mexico

Extrapolations from 10m above the ground up to the wind turbine hub height are frequently made to the data available for wind power assessments. Because of its simplicity, the power law profile has been one of the most popular mathematical formulations to predict the vertical wind shear. This paper presents an analysis of wind speed and wind shear in terms of the directional, diurnal and seasonal patterns for a site at the Autonomous University of Yucatan which experiences the tropical conditions of the Yucatan Peninsula in Mexico. This analysis takes a detailed look at frequency distributions to facilitate a comprehensive understanding of the local climatic conditions. Diurnal wind speed variations are shown to be affected in particular by the differing wind conditions associated with fetches over two distinct offshore regions. Seasonal behaviour suggests some departure from the oscillations expected from temperature variation. In addition, the use of rate of change of temperature at one height is proposed as an alternative to vertical temperature gradient inferred from two heights as an indicator of atmospheric stability which will affect the wind shear. The work presented is part of a regionally funded research program to evaluate the onshore and offshore wind potential in the north of the Yucatan Peninsula.

The historical record in the Scaglia limestone at Gubbio: magnetic reversals and the Cretaceous‐Tertiary mass extinction

AbstractThe Scaglia limestone in the Umbria‐Marche Apennines, well‐exposed in the Gubbio area, offered an unusual opportunity to stratigraphers. It is a deep‐water limestone carrying an unparalleled historical record of the Late Cretaceous and Palaeogene, undisturbed by erosional gaps. The Scaglia is a pelagic sediment largely composed of calcareous plankton (calcareous nannofossils and planktonic foraminifera), the best available tool for dating and long‐distance correlation. In the 1970s it was recognized that these pelagic limestones carry a record of the reversals of the magnetic field. Abundant planktonic foraminifera made it possible to date the reversals from 80 to 50 Ma, and subsequent studies of related pelagic limestones allowed the micropalaeontological calibration of more than 100 Myr of geomagnetic polarity stratigraphy, from ca 137 to ca 23 Ma. Some parts of the section also contain datable volcanic ash layers, allowing numerical age calibration of the reversal and micropalaeontological time scales. The reversal sequence determined from the Italian pelagic limestones was used to date the marine magnetic anomaly sequence, thus putting ages on the reconstructed maps of continental positions since the breakup of Pangaea. The Gubbio Scaglia also contains an apparently continuous record across the Cretaceous–Tertiary boundary, which was thought in the 1970s to be marked everywhere in the world by a hiatus. A geochemical study of the Gubbio Cretaceous–Tertiary boundary accidentally uncovered an unexpectedly large concentration of iridium in the boundary clay, providing the first evidence for a large comet or asteroid impact at the time of the Cretaceous–Tertiary mass extinction. The sudden foraminiferal extinction in the essentially complete Gubbio Scaglia showed that the Cretaceous–Tertiary extinction was a catastrophic event. After publication of the Gubbio Cretaceous–Tertiary iridium anomaly in 1980, a decade followed in which more and more evidence for a catastrophic impact challenged the traditional uniformitarian viewpoint of geologists. In 1991, the impact site was discovered at Chicxulub, in the Yucatán Peninsula of Mexico. The Gubbio area has thus emerged as a classical geological locality. It has been critical in the development of geomagnetic reversal stratigraphy, a third system for dating Earth history, complementing biostratigraphy and radiometric age dating. Gubbio was also central to the recognition that occasional catastrophic events like great impacts require a rejection of strict uniformitarianism.

Metal distribution in coral reef complex Cayo Arcas in the Gulf of Mexico

This study evaluated the spatial and temporal distribution of metals in the coral reef system Cayos Arcas and Triangulos in the Campeche Bank region, off the Yucatan peninsula in Mexico. No information has been generated before for the incorporation of natural and non-natural occurring metals, some of which are possibly endowed by the oil marine station Cayo Arcas. The multivariate exploratory study of the metals on the coral skeletons, showed the formation of two distinct groups. The metals that have the highest influence on the differentiation of the groups are the metals that are natural constituents of the coral skeletons, in particular Sr can explain much of the differences between the groups, and to a much lesser extent are the metals that could be indicators of pollution. This differentiation suggests that, in our case, the environment around the corals has a higher impact than the non-naturally occurring metals (and possible indicators of pollution). The two groups formed corresponded to: the coral cores influenced by open sea variables and the coral cores in the inner part of the keys which is less exposed to open sea variables. A chronological study was made to two samples that had the longest coral section and were situated in two clearly distinctive zones: an exposed surface subjected to high wave forces and another that was less exposed. Ni and Zn show an accumulation trend in both coral samples, while Ba showed an increase in incorporation around 1980 when the Cayo Arcas oil marine station was constructed.

Detrital zircon geochronology of Jurassic sandstones of western Cuba (San Cayetano Formation): Implications for the Jurassic paleogeography of the NW Proto-Caribbean

Clastic sediments of the early (?) to late Jurassic (Oxfordian) San Cayetano Formation of western Cuba are interpreted to reflect syn-rift sedimentation coeval with the breakup of Pangaea. This sedimentary unit is the oldest known in the Guaniguanico Mountains and Cuba. U-Pb SHRIMP dating of 19 detrital zircon grains from two samples of San Cayetano micaceous sandstone provided concordant ages ranging from ∼398 to 2479 Ma. The oldest zircon population is of Paleoproterozoic age (∼2479 - 1735 Ma), but most zircons have early Mesoproterozoic and Grenvillian ages (∼1556 - 985 Ma), whereas still younger ages are Pan-African (561 Ma), Ordovician (451 Ma) and early Devonian (∼398 Ma). We discuss the possible origin of these zircons and conclude that the most likely source terrain(s) are Precambrian and early Paleozoic massifs in northern South America (Colombia and/or Venezuela) and the Yucatan Peninsula in Mexico. This is compatible with paleogeographic reconstructions of the Caribbean that imply that sediments of the San Cayetano Formation were still part of the disintegrating supercontinent Pangea in pre mid-Oxfordian time.

In vivo and In vitro Control of Leishmania mexicana due to Garlic‐induced NO Production

Leishmania mexicana is the main causal agent of cutaneous leishmaniasis in the Yucatán peninsula in Mexico. Control of this disease is associated with a Th1-type immune response and garlic extract has been reported as a Th1 immunomodulator in BALB/c mice infected with Leishmania major. In this study, we investigated the effect of garlic extracts on L. mexicana infection in vivo and in vitro. Garlic extract reduced footpad lesions in L. mexicana-infected BALB/c mice by inducing IFN-gamma production from T cells. In vitro, garlic extract reduced macrophage infection through induction of nitric oxide (NO) production. Garlic extract may thus act on both T cells and macrophages to stimulate IFN-gamma production and NO synthesis for parasite killing. A 10- to 14-kDa fraction was identified as responsible for the in vitro effect of the whole extract and may lead to the identification of novel immunomodulating drugs and therapeutic alternatives for the treatment of leishmaniasis.

Preliminary identification and coat protein gene phylogenetic relationships of begomoviruses associated with native flora and cultivated plants from the Yucatan Peninsula of Mexico

A number of native and cultivated eudicots in the Yucatan Peninsula of Mexico (YPM) exhibit symptoms associated with virus infection. Symptomatic leaves were collected and assessed for begomoviral detection using polymerase chain reaction (PCR), and universal primers that amplify a fragment of the coat protein gene (core Cp). Begomovirus were detected in nine native and seven cultivated species, representing seven eudicot families. DNA extracts from the 16 hosts were used for PCR amplification and sequencing of a fragment containing the coat protein (Cp) gene. The complete Cp sequence was used to establish provisional species identification. Results indicated that 13 distinct begomovirus species were represented. Among these, five potentially new begomovirus species were identified, for which we propose the names Anoda golden mosaic virus (AnGMV), Boerhavia yellow spot virus (BoYSV), Papaya golden mosaic virus (PaGMV), Desmodium leaf distortion virus (DeLDV), and Hibiscus variegation virus (HiVV). Five previously described begomoviral species were provisionally identified for the first time in the YPM; these include Euphorbia mosaic virus (EuMV), Melon chlorotic leaf curl virus (MCLCuV), Okra yellow mosaic Mexico virus (OkYMMV), Sida golden mosaic virus (SiGMV), and Tobacco apical stunt virus (TbASV). Additionally, viruses previously reported from this region, Bean golden yellow mosaic virus (BGYMV), Pepper golden mosaic virus (PepGMV), and Tomato mottle virus (ToMoV) were provisionally identified in cultivated hosts. Phylogenetic analysis provisionally placed all isolates from the YPM in a Western Hemisphere begomovirus clade.

ELECTRICITY AND PROPANE CONSUMPTION OF A SHRIMP HATCHERY IN THE STATE OF BAJA CALIFORNIA SUR, MEXICO

The consumption of electricity and propane for producing larvae and postlarvae of the whiteleg shrimp (Litopenaeus vannamei) was examined in a commercial shrimp hatchery on the Baja California Peninsula of Mexico. Between January and August 2005, 6 × 106 postlarvae (average age PL16) were produced from 1.43 × 109 nauplii. During that production period, the hatchery used 2.48 × 109 kcal of fossil fuel energy (30% for electricity, 70% for liquid propane), which was equivalent to 16% of the operating costs. Electricity was used mainly for larval and postlarval rearing (36% and 10%) and microalgae culture (27%). During this production period, 1.47 × 109 kcal of propane were consumed for heating daily more than 600 m3 seawater daily. Of that total, 33% was used for broodstock maintenance, 65% for larvae culturing, and 2% for postlarvae rearing. With increasing costs for shipping postlarvae to the mainland Mexican coastal areas (15% of operating costs) and the need to remain competitive with hatcheries in the coastal areas of Sonora and Sinaloa, alternative energy sources to reduce overall operational costs in hatcheries of Baja California Sur are discussed.

ASSESSMENT OF TRIATOMA DIMIDIATA DISPERSAL IN THE YUCATAN PENINSULA OF MEXICO BY MORPHOMETRY AND MICROSATELLITE MARKERS

In the Yucatán Peninsula of Mexico, the main vector of Chagas disease is Triatoma dimidiata. Field studies suggest that natural transmission occurs through transient and seasonal invasion of houses by sylvatic/peridomestic triatomines, rather than through persistent domiciliated bug populations. We investigated the genetic structure of T. dimidiata populations, using morphometry and microsatellite markers, to assess dispersal of individuals in this triatomine species and to understand the dynamics of domestic infestation. We observed low phenotypic and genetic differentiation among populations from different villages, with an FST of only 0.0553, which suggested a weak but significant population structure at this level. Similarly low but significant differences were observed among populations from the same village but different biotopes (sylvatic, peridomestic, and domestic), with FST values ranging from 0.0096 to 0.0455. These data suggested elevated dispersal of bugs between biotopes (Nm = 5-25), which was confirmed by likelihood and Bayesian assignment tests. A proportion of bugs collected within domiciles were significantly assigned to peridomestic and sylvatic areas. This study showed that T. dimidiata has important dispersal capabilities that can explain the seasonal pattern of domicile infestation by peridomestic and sylvatic bugs. Therefore, dispersal should be taken into account in the design of effective vector control strategies.

A theoretical framework for a ‘spatially conscious’ economic analysis of environmental issues

This paper proposes a theoretical framework for the integration of economic aspects and environmental aspects into the decision-making process for sustainable development strategies. The aim is integrate Geographic Information Systems (GIS) and environmental valuation methods in the structure of a cost–benefit analysis (CBA) in order to better evaluate spatial concerns. The conceptual approach is augmented by a modest case study of a marina development in Santa Rosaliita on the Baja California peninsula in Mexico. This marina project is part of the proposed ‘Escalera Nautica’ an ambitious regional development scheme, which has caused controversy concerning its social, economic and environmental implications. The paper outlines the necessity to develop spatially conscious methodologies for a policy relevant research regarding sustainable regional development. Additionally, the paper contributes a spatial analytic perspective based on normative economic principles to the recent discussion on environmental economic geography.

Production costs of conventional and organic honey in the Yucatán Peninsula of Mexico

Production costs of conventional and organic honey in the Yucatán Peninsula of Mexico

Introduction of Asian Soybean Rust Urediniospores into the Midwestern United States-A Case Study.

In 2005, weekly rain samples collected at 124 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites in the eastern and central United States were screened for Asian soybean rust (ASR; Phakopsora pachyrhizi) urediniospores. Application of a quantitative polymerase chain reaction method detected P. pachyrhizi DNA in the filter residue of rain samples collected during the week of 19 to 26 July 2005 in Minnesota, Missouri, and South Dakota. To determine the geographic origin of ASR urediniospores in those weekly composite samples, back air trajectories of the lifted condensation and mixed boundary layers were calculated for each rain event within the week, by sampling site. The calculations, based on the hybrid single-particle lagrangian integrated trajectory model, pointed to source areas in eastern and southern Texas. In a separate case, DNA of P. pachyrhizi was detected in a 28 June to 5 July 2005 rain sample from an eastern Texas site. Back trajectories pointed to southern Texas and the Yucatan Peninsula in Mexico as potential source areas of ASR urediniospores. Vertical motions of those back trajectories indicated a ventilation of the boundary layer in the upwind areas, suggesting the possible injection of urediniospores into the free troposphere where they can be transported for long distances before wet deposition.

Production Costs Of Conventional And Organic Honey In The Yucatán Peninsula Of Mexico

SummaryIn the Yucatán peninsula of México, ca 16,000 beekeepers are indigenous Mayan farmers living in relatively natural, undisturbed regions and practicing traditional forms of Apis mellifera beekeeping. The economics of family survival, where large profits from honey sales are not possible, are distinct from the economics of the large market economy surrounding them. According to market economic theory, in the years 2002 and 2003 those beekeepers who did not produced more than 1,200 kg honey per year did not recover their investments, at least as regards variable costs; in other words, they paid more than they gained through sales. In addition, it is shown that organic (ecologic) honey production increases costs about 70% above that of conventional honey.

In Search of the Rain Forest

Review: In Search of the Rain Forest By Candace Slater (Ed.) Reviewed by Elery Hamilton-Smith Charles Sturt University, Australia Candace Slater (Ed.). In Search of the Rain Forest. Durham: Duke University Press, 2003. 318 pp. ISBN 0-8223-3205-1 (cloth); 0-8223-3218-3 (paper). US$79.95 cloth; $22.95 paper. This book, which grew out of a six-month seminar that included a field visit to the Yucatan Peninsula of Mexico, challenges most of the prevailing assumptions and discourses about the rain forest. The extent to which the Yucatan has come to be widely identified (not by the authors) as rain forest highlights the growing ambiguity of the very concept. The first essay focuses upon the X-Caret mega-theme park of the Yucatan. This is a spectacular nature-based amusement park with a well-integrated blend of authenticity and carefully contrived and executed romanticized falsehood. It has had many positive effects upon the conservation of various aspects of the environment, widespread awareness of environmental values, and the socio-economic development of the region. Yet it also raises a number of ethical and other problems. Its overwhelming dominance of the regional tourism industry causes some deep concerns for more humble operators, many of whom have a sincere commitment to authenticity and genuine conservation. I certainly enjoyed and appreciated my personal experience of X-Caret, but I sympathize with those who express concern. Any serious examination of it will inevitably generate ambiguity and ambivalence. Other essays deal respectively with wildfire in forested areas, apparently responsible oil extraction in Ecuador, the appropriation and industrialization of herbal medicine in the forests of Belize, a critical history of the Mayan rain forests, Indian preservation of tigers through protected areas, the generation and control of violence in the indigenous peoples of Kalimantan, and the viral forests of Africa as a horror spectacle. Interestingly, several essays develop and discuss, as a sub-theme, the way in which protected forests often provide a splendid environment for crime. The resources of the forest, both fauna and timber, are subject to poaching or other illegal harvesting; the environment also provides a haven within which such activities as distribution of illegal drugs can proceed without effective control. Regrettably, as a sub-theme, the complexities of illegality in this setting are not thoroughly explored and none of the authors appear to

Monogenean Parasites of some Elasmobranchs (Chondrichthyes) from the Yucatán Peninsula, Mexico

Forty-two individuals representing 8 species of stingray were collected from 14 localities along the coast of the Yucatan Peninsula in Mexico. Monogeneans from 2 families (Monocotylidae Lebedev, 1988 and Capsalidae Baird, 1853) were found on the gills and body surfaces. Dendromonocotyle octodiscus Hargis, 1955 was collected from Dasyatis americana Hildebrand and Schroeder, 1928 from Blanquizal, Quintana Roo, Mexico, and Urobatis jamaicensis (Cuvier 1816) McEachran and Fechhelm 1998 from Xcalak, Isla Contoy, Mexico, Cozumel, Quintana Roo, Mexico, and Ria Lagartos, Yucatan, Mexico. Decacotyle floridana (Pratt, 1910) Chisholm and Whittington, 1998 was collected from Aetobatus narinari (Euphrasen 1790) from Holbox, Quintana Roo, Mexico, and Ciudad del Carmen and Champoton, Campeche, Mexico. Benedeniella posterocolpa (Hargis, 1955) Yamaguti, 1963 was collected from Rhinoptera bonasus (Mitchell, 1815) from Champoton, Campeche, Mexico. Quintana Roo and Yucatan, Mexico, are new distribution records for D. octodiscus, and U. jamaicensis is a new host record for this species from a host collected from nature. Quintana Roo is a new locality record for D. floridana, and Campeche, Mexico, is a new locality record for B. posterocolpa. Hypotheses of biogeographical and coevolutionary patterns concerning monogeneans of elasmobranchs are premature, but B. posterocolpa seems to be strictly host specific, whereas D. floridana and D. octodiscus display a much lower level of host fidelity at lower host taxonomic levels.