This study, the first extensive study on a species from the Mexican Atlantic slope, is part of a national project focused on the systematics of the amphidromous species of Macrobrachium Spence Bate, 1868, which occur in coastal drainage basins of Mexico. Five amphidromous species of Macrobrachium have been found to occur in this region: M. acanthurus (Wiegmann, 1836), M. carcinus (Linnaeus, 1758), M. heterochirus (Wiegmann, 1836), M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodr & iacute;guez, 1990, and M. olfersii (Wiegmann, 1836). We studied specimens of the putative M. acanthurus (type locality: coast of Brazil) from basins of the states of Tamaulipas, San Luis Potos & iacute;, Veracruz, Tabasco, Chiapas, and Campeche. Comparison of their COI haplotypes with M. acanthurus sequences from Costa Rica, Panama, and Brazil deposited in the GenBank revealed high genetic distance (9.3 to 10.4%) between them. Maximum likelihood and Bayesian inference analyses performed by using concatenated 16S-COI sequences to investigate the evolutionary relationship of our haplotypes and other Macrobrachium species in the GenBank showed the Mexican haplotypes in a separate clade from its closest entity the M. acanthurus clade from regions south of Mexico. The wide COI genetic distance and the phylogenetic inference of the 16S-COI haplotypes show that our specimens correspond to M. mexicanum (De Saussure, 1857), a cryptic species previously considered a junior synonym of M. acanthurus. We studied photographs of four syntypes of M. mexicanum and conclude that their morphological characteristics fit well with our studied individuals.

As part of a research project on the taxonomy of the woodlice (Oniscidea) of northern Mexico, isopod collections of Mexican academic institutions were examined. For the first time, the main diagnostic morphological traits of 4 native species are documented using SEM micrographs: Alloniscus mirabilis (Stuxberg, 1875) (Alloniscidae) and Littorophiloscia richardsonae (Holmes & Gay, 1909) (Halophilosciidae) from the northern Pacific coast of Baja California, Venezillo apacheus (Mulaik in Mulaik & Mulaik, 1942) (Armadillidae) from northern central Durango, which is also the first record of this species in Mexico, and Porcellio virgatus (Budde-Lund, 1885) (Porcellionidae) from the northeastern states of Nuevo León and Tamaulipas. The first 2 COI haplotypes (mtDNA) for P. virgatus are reported. Bayesian phylogenetic analysis of COI haplotypes placed P. virgatus in a clade with a Porcellio dilatatus haplotype with high support, forming a group with Porcellio scaber.

Abstract We had previously revised the systematics of four species of MacrobrachiumSpence Bate, 1868 from the Pacific coast of Mexico, including the Baja California Peninsula (BCP): M. americanumSpence Bate, 1868, M. digueti (Bouvier, 1895), M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodríguez, 1990, and M. occidentale Holthuis, 1950. Genetic analyses of the mitochondrial markers 16S ribosomal RNA (16S) and cytochrome oxidase I (COI) of individuals of these morphological species from BCP have shown that, even facing the Gulf of California (Sea of Cortés) as an apparent marine ecological barrier, they are conspecific to their respective genetic lineages (species) found from the Pacific slope of mainland Mexico. We discuss the systematics of the fifth species of Macrobrachium from the Mexican Pacific slope, M. tenellum (Smith, 1871) to test the hypothesis that individuals of the putative M. tenellum from BCP belong to the same species from the Pacific slope of mainland Mexico. We revised the morphological characters of taxonomic importance using material obtained in the field and voucher material deposited in Mexican scientific collections, and performed molecular genetic analyses with newly generated fragments of the mitochondrial markers 16S and COI. We conclude, as in our previous studies on Macrobrachium species of the region, that the examined specimens of the putative M. tenellum from BCP belong to the same species found on the Pacific slope of mainland Mexico, and that oceanic dispersal is responsible for the distribution of the species of Macrobrachium in the peninsula rather than by vicariant events.

We document the morphology, morphometric variations among the morphotypes of the brine shrimp, Artemia franciscana. From the samples collected at four different locations in South India, Tamil Nadu viz. Kelambakkam, Vedaranyam, Tuticorin and Nagarcoil we identified six morphotypes: M1, M3, M4 in males and F1, F2, F3 in females. The Scanning electron micrographs of male morphotypes show distinct variation in the basal width, shape and number of cuticular cones on the second antennae. Similarly, the female morphotypes show various shape and sizes of the ovisac with or without spines. However, the cyst surface topography is smooth without any specific variation/ ornamentation in all three female morphotypes. Multivariate analysis of eighteen morphological traits measured in males and fifteen in females to elucidate the intraspecific variations among morphotypes indicate significant dissimilarity between males and females. Furthermore, relative length measurements showed distinct morphometric variation of traits between the morphotypes encountered at different sampling sites.

We had previously revised the systematics of four species of Macrobrachium from the Pacific coast of Mexico, including the Baja California Peninsula (BCP): M. americanum, M. digueti (), M. hobbsi Nates & Villalobos in , and M. occidentale Holthuis, 1950. Genetic analyses of the mitochondrial markers 16S ribosomal RNA (16S) and cytochrome oxidase I (COI) of individuals of these morphological species from BCP have shown that, even facing the Gulf of California (Sea of Cortes) as an apparent marine ecological barrier, they are conspecific to their respective genetic lineages (species) found from the Pacific slope of mainland Mexico. We discuss the systematics of the fifth species of Macrobrachium from the Mexican Pacific slope, M. tenellum () to test the hypothesis that individuals of the putative M. tenellum from BCP belong to the same species from the Pacific slope of mainland Mexico. We revised the morphological characters of taxonomic importance using material obtained in the field and voucher material deposited in Mexican scientific collections, and performed molecular genetic analyses with newly generated fragments of the mitochondrial markers 16S and COI. We conclude, as in our previous studies on Macrobrachium species of the region, that the examined specimens of the putative M. tenellum from BCP belong to the same species found on the Pacific slope of mainland Mexico, and that oceanic dispersal is responsible for the distribution of the species of Macrobrachium in the peninsula rather than by vicariant events.

We had previously revised the systematics of four species of MacrobrachiumSpence Bate, 1868 from the Pacific coast of Mexico, including the Baja California Peninsula (BCP): M. americanumSpence Bate, 1868, M. digueti (Bouvier, 1895), M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodríguez, 1990, and M. occidentale Holthuis, 1950. Genetic analyses of the mitochondrial markers 16S ribosomal RNA (16S) and cytochrome oxidase I (COI) of individuals of these morphological species from BCP have shown that, even facing the Gulf of California (Sea of Cortés) as an apparent marine ecological barrier, they are conspecific to their respective genetic lineages (species) found from the Pacific slope of mainland Mexico. We discuss the systematics of the fifth species of Macrobrachium from the Mexican Pacific slope, M. tenellum (Smith, 1871) to test the hypothesis that individuals of the putative M. tenellum from BCP belong to the same species from the Pacific slope of mainland Mexico. We revised the morphological characters of taxonomic importance using material obtained in the field and voucher material deposited in Mexican scientific collections, and performed molecular genetic analyses with newly generated fragments of the mitochondrial markers 16S and COI. We conclude, as in our previous studies on Macrobrachium species of the region, that the examined specimens of the putative M. tenellum from BCP belong to the same species found on the Pacific slope of mainland Mexico, and that oceanic dispersal is responsible for the distribution of the species of Macrobrachium in the peninsula rather than by vicariant events.

For the Mexican oniscideans of the family Armadillidae, 6 species of the genus Cubaris Brandt, 1833 and 18 species of the genus Venezillo Verhoeff, 1928 have been recorded. Of them, only Venezillo stuckchensis (Mulaik, 1960) has been registered for the Baja California Peninsula (BCP). This species was described upon a single male and no biological studies exist on this taxonomic entity since its original description in 1960. In this work, we redescribe V. stuckchensisincluding the designation of a neotype and paratopotypes using specimens from the type locality. We report this species from 5 additional wetlands of southern BCP in the state of Baja California Sur. The type locality is corrected in its formal name and its geographical location. The morphological identity of V. stuckchensis is documented using SEM micrographs, and data on its molecular identity with 16S ribosomal RNA mitochondrial gene fragments are given.

The amphidromous species of Macrobrachium Spence Bate, 1868 occurring on the Mexican Pacific slope (M. americanum Spence Bate, 1868, M. digueti (Bouvier, 1895), M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodríguez, 1990, M. occidentale Holthuis, 1950 (Holthuis, 1950b), and M. tenellum (Smith, 1871)) show a disjunct distribution, with the abscence of records along about 2000 km of the coastal margins in the northern Gulf of California. Recent morphological and genetic studies using the mitochondrial genes 16S rRNA (16S) and cytochrome oxidase I (COI) show that individuals of the putative M. digueti, M. hobbsi, and M. occidentale from the Baja California Peninsula are conspecific to their respective taxonomic entities found along the Pacific slope of mainland Mexico. We review the systematics of M. americanum from the Mexican Pacific slope and found that individuals of putative M. americanum from the Baja California Peninsula belong to the same lineage of individuals from the Pacific slope of mainland Mexico based on newly generated fragments of the mitochondrial genes 16S (491 bp) and COI (548 bp). We present a systematic account for M. americanum, including a taxonomic treatment of the studied populations with a report of their genetic identity and phylogenetic relationships.

In diatoms the use of molecular tools to corroborate traditional (morphological) identification offers a new perspective in the field of biogeography. This manuscript reports the first record of the raphid pennate diatom Nitzschia volvendirostrata along the coast of Mexico, which in turn represents an expansion of the geographic range along the American continent. The cells were isolated from benthic samples taken from Balandra lagoon, La Paz, Baja California Sur, Mexico and cultured as a monoclonal culture. Morphology and morphometry of the diatom obtained from light and electron microscopy reveal that they correspond to the original description of N. volvendirostrata and also its chloroplast sequences, rbcL and psbC, showed 98.7 to 100 % similarity and a close phylogenetic relationship with N. volvendirostrata. The reported places for this taxon show that it has a tropical-temperate biogeographical affinity.

To date 86 species of 33 genera and 16 families of Oniscidea have been recorded in Mexico. Collections of 4 academic institutions and recent field materials were revised. From 1,820 specimens, 1,417 (77.6%) were determined to belong to 6 exotic forms. A taxonomic account and a species identification key with SEM plates of these exotic entities are presented. For morphological analysis we used light and SEM microscopy. The molecular identity of 5 of the 6 forms was examined through cytochrome oxidase 1 gene (mtDNA) analyses. The exotic species determined are: Armadillidae, Cubaris murina; Armadillidiidae, Armadillidium vulgare; Porcellionidae, Agabiformius lentus, Porcellio laevis, P. scaber, and Porcellionides pruinosus. The exotic oniscideans were recorded from urban, rural and natural (riparian) zones in 15 states of northern Mexico, including the first formal records in Aguascalientes,Chihuahua, Durango, and Zacatecas. Armadillidium vulgare, P. laevis, and P. pruinosus often co-occurred and are the most widely distributed species in this region. Although most of the material examined was recorded from urban zones(> 50% of studied sites), A. vulgare and P. laevis were also found in riparian areas (natural zones), yet P. pruinosus was recorded mainly from riparian areas (60% of 45 lots examined).

Halamphora siqueirosii sp. nov. is a marine benthic diatom isolated as a monoclonal culture from a hypersaline evaporation pond at the Guerrero Negro Saltworks, Baja. California Sur, Mexico. Analysis of the valve ultrastructure of this taxon using light and electron microscopy indicated that its uniseriate striae and the density of its dorsal striae are useful characteristics for discriminating H. siqueirosii from other species with similar morphological patterns. The phylogenetic analyses performed with nuclear ribosomal genes, the small (18S) and large subunits (28S), and chloroplast gene ribulose-bisphosphate carboxylase (rbcL) fragments showed that H. siqueirosii is closely related to H. americana, H. calidilacuna and H. incelebrata. Morphological differences between this new species and similar ones are discussed.

Brachionus plicatilis is one of the most important rotifers used in aquaculture worldwide. We found a strain of B. plicatilis in Lake Patzcuaro, a shallow water body in Central Mexico, which also supports several species of endemic fish. Here we present an investigation of the life-table demography and population growth of B. plicatilis at salinities of 5, 10, 15, 20, and 25 g L-1, and the molecular identity of this rotifer, comparing its genetic relation with other related taxa. The experiments were conducted using standard cohorts in five replicates. We found that this strain of B. plicatilis was better adapted to low (5 and 10 g L-1) rather than high salinities, with the survivorship ranging from 15 to 18 days, but 50 % mortality of the population occurred by day 6. The population-growth rate varied from 0.2 to 0.35 d(-1). We discuss the results with reference to similar studies conducted on several strains and species of the Brachionus plicatilis complex and the importance of our findings for aquaculture of endemic fish from this ancient shallow lake.

Six amphidromous species of Macrobrachium Spence Bate, 1868 have been recorded on the Pacific slope of Mexico, including the two morphologically related M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodriguez, 1990 and the Atlantic species M. olfersii (Wiegmann, 1836). The hypothesis that the formation of the Isthmus of Panama in the Late Pliocene produced a vicariant event leading to the formation of two groups of Macrobrachium species, one on the Atlantic slope and the other on the Pacific slope, has raised doubts about the amphiamerican occurrence of M. hobbsi and M. olfersii. Recent molecular studies have supported that hypothesis that there are no amphiamerican species of Macrobrachium, but rather amphiamerican species groups. In a previous publication, we proposed that one of the groups occurring along the Mexican slopes is the olfersii group, comprising the digueti subgroup, and the olfersii subgroup represented by M. hobbsi in the Pacific and M. olfersii in the Atlantic. We reviewed the systematics of the olfersii subgroup from the Pacific slope by analyzing individuals obtained from 104 sites in 44 drainage basins in nine Mexican states. Morphological and molecular genetic analyses with newly generated fragments of the mitochondrial genes 16S (470 bp) and COI (542 bp) confirm that, in the olfersii subgroup, only one morphologically plastic species, M. hobbsi, occurs on the Mexican Pacific slope. It is the most common species of Macrobrachium on this slope and is genetically different from the M. olfersii Atlantic populations. The results also indicate that disjunct populations of the Baja California Peninsula and the mainland belong to the same genetic lineage.

Macrobrachium digueti (Bouvier, 1895), an amphidromous shrimp with unequal chelae, was described from Mulegé River in Baja California Peninsula, Mexico. A controversy on the morphological identity of M. digueti started six decades ago. Some authors point out that the redescription given in 1952 by L. Holthuis in his important revision of the Palaemonidae of the American continent does not correspond to Bouvier’s species. A controversy also exists on the taxonomy of the species because morphological and molecular studies have indicated great similarity of M. acanthochirusVillalobos, 1967 and M. michoacanus Nates and Villalobos in Villalobos Hiriart & Nates Rodríguez, 1990 with M. digueti (sensu Bouvier), suggesting their synonymy with the last species. We review the systematics of the Mexican populations of the putative M. digueti (Bouvier, 1895) consisting by individuals with unequal chelae, a carpus shorter than the merus and scarce pubescence on the palm and cutting edges of the fingers of the larger male second pereiopod. Extensive field surveys of the species of MacrobrachiumSpence Bate, 1868 were made along the Pacific slope of Mexico, from the Baja California Peninsula in the north to Guerrero state in the south, an area that covered the type localities of the three nominal species. Results of the morphological revision and molecular genetic analyses with fragments of the mitochondrial genes 16S and COI confirmed the morphological identity of M. digueti as described by Bouvier and indicate that this entity is a morphologically plastic genetic species with a disjunct distribution along the peninsula and the Pacific mainland. Our study also confirms that M. acanthochirus and M. michoacanus are junior synonyms of M. digueti. Implication of present findings on the amphiamerican species groups of Macrobrachium is discussed.

Four new genera of funnel-web spiders of the family Agelenidae C.L. Koch, 1837 from the Baja California Peninsula, Mexico are described and illustrated. Bajacalilena gen. nov. is represented by B. bolzerni sp. nov. and B. clarki sp. nov. Cabolena gen. nov. is represented by C. huiztocatl sp. nov., C. kosatli sp. nov., and C. sotol sp. nov. Callidalena gen. nov. is represented by C. quintin sp. nov. and C. tijuana sp. nov. Lagunella gen. nov. is represented by L. guaycura sp. nov. Additionally, the males of Calilena angelena Chamberlin & Ivie, 1941, Hololena septata Chamberlin & Ivie, 1942, and Rothilena sudcaliforniensis Maya-Morales & Jimenez, 2013 are described for the first time. New records for C. angelena, H. septata, R. cochimi Maya-Morales & Jimenez, 2013, R. pilar Maya-Morales & Jimenez, 2013, and R. sudcaliforniensis are also provided. Molecular analysis of a fragment of cytochrome c oxidase subunit I (COI) provides support for the monophyly of the new genera and facilitated sorting of conspecific males and females. Finally, an identification key to native Nearctic and Neotropical genera of the subfamily Ageleninae is provided.

Macrobrachium digueti (Bouvier, 1895), an amphidromous shrimp with unequal chelae, was described from Mulege River in Baja California Peninsula, Mexico. A controversy on the morphological identity of M. digueti started six decades ago. Some authors point out that the redescription given in 1952 by L. Holthuis in his important revision of the Palaemonidae of the American continent does not correspond to Bouvier's species. A controversy also exists on the taxonomy of the species because morphological and molecular studies have indicated great similarity of M. acanthochirus Villalobos, 1967 and M. michoacanus Nates and Villalobos in Villalobos Hiriart & Nates Rodriguez, 1990 with M. digueti (sensu Bouvier), suggesting their synonymy with the last species. We review the systematics of the Mexican populations of the putative M. digueti (Bouvier, 1895) consisting by individuals with unequal chelae, a carpus shorter than the merus and scarce pubescence on the palm and cutting edges of the fingers of the larger male second pereiopod. Extensive field surveys of the species of Macrobrachium Spence Bate, 1868 were made along the Pacific slope of Mexico, from the Baja California Peninsula in the north to Guerrero state in the south, an area that covered the type localities of the three nominal species. Results of the morphological revision and molecular genetic analyses with fragments of the mitochondrial genes 16S and COI confirmed the morphological identity of M. digueti as described by Bouvier and indicate that this entity is a morphologically plastic genetic species with a disjunct distribution along the peninsula and the Pacific mainland. Our study also confirms that M. acanthochirus and M. michoacanus are junior synonyms of M. digueti. Implication of present findings on the amphiamerican species groups of Macrobrachium is discussed.

Branchinecta lindahli is a generalist fairy shrimp that has a widespread distribution in North America. We initiated a study to better understand the geographic structure of genetic variation within this species and to test if cryptic species are present in B. lindahli. Additionally, we examined four other species of Branchinecta to test if there were any generalities in the levels of genetic divergence within and among species. Genetic data from the mitochondrial cytochrome c oxidase I gene revealed two distinct clades within B. lindahli: one found in the Central Valley and Mojave Desert of California, USA and one found in Baja California, Mexico. The remaining haplotypes were widespread throughout the remainder of North America. Further examination of the distribution within clades revealed no additional phylogeographic structure. The amount of intraspecific divergence observed for B. lindahli and B. hiberna was high compared to B. mackini and B. sandiegonensis. However, maximal intraspecific divergences were less than what was observed among Branchinecta species. We argue that the amount of intraspecific divergence observed in B. lindahli is not consistent with the presence of cryptic species and that caution should be taken when attempting to delimit cryptic species within this group.

As a part of an ongoing research initiative on Sonoran Desert large branchiopod biodiversity, we conducted extensive field surveys along the Baja California Peninsula. We present here a taxonomic review of the genus Branchinecta on this peninsula. The results confirm the presence of B. lindahli Packard, 1883, B. mackini Dexter, 1956, and B. sandiegonensis Fugate, 1993, and provide the first Mexican records of the world's largest anostracan B. gigas Lynch, 1937. The peninsular sites of the four Branchinecta represent the southernmost extent of their distribution. The giant fairy shrimp was discovered from two shallow temporary lakes located in the Valle de los Cirios. The large branchiopod species assemblage that occurs in these lakes is unique among the temporary wetlands of Mexico. These lakes, so far, are the only known habitats in Mexico where the tadpole shrimp Lepidurus lemmoni Holmes, 1894, and B. gigas occur.

Thamnocephalus is endemic to the American continents, being recorded in the USA, Mexico, Venezuela, Aruba, and Argentina with four recognized species: T. venezuelensis Belk and Pereira, 1982 and T. salinarum Cohen, 2002 from South America, and T. mexicanus Linder, 1941 and T. platyurus Packard, 1877 from North America. A systematic review of Mexican populations of T. mexicanus and T. platyurus is presented that includes a revision of their diagnostic morphological characteristics, a molecular characterization using fragments of the mitochondrial genes 16S and COI to assess their haplotypic identity and genetic differentiation, and an update of their geographical distribution. Molecular and morphological data confirm that T. mexicanus and T. platyurus represent two biological lineages at the species level. Distance range in 16S inter-species haplotypes was 9.6 to 10.0%, whilst in COI it was 17.0 to 18.3%. The Mexican sites where the species co-occurred are updated to 11, three of them in the Sonoran Desert, and eight in the Chihuahuan Desert.