On three new species of Cypretta Vávra, 1895 (Crustacea: Ostracoda) from the Yucatan Peninsula, Mexico.

Three new species of the genus Cypretta Vivra, 1985 are described from Southern Mexico, representing the first record of the genus in the country. Cypretta campechensis n. sp. is closely related to Florida and North Carolina species such as C. nigra Furtos, 1936, C. brevisaepta Furtos, 1934 and C. bilicis Furtos, 1936. Cypretta spinosa n. sp. is related to the North and South American species C. intonsa Furtos, 1936 and C. vivacis Würdig & Pinto, 1993, but also to some Australian and South-East Asian Islands ones, such as C. obfuscata Victor & Fernando, 1981 and C. raciborskii (Grochmalicki, 1915). The last species described herein, Cypretta maya n. sp., is closely related to the South-East Asia islands, Australian and north Indian species, in particular to C. hirsuta Henry, 1923, C. longidactyla Victor & Fernando, 1981, and C. patialensis Battish, 1982.

Mastigodiaptomus galapagoensis n. sp. (Crustacea: Copepoda: Diaptomidae), a possibly extinct copepod from a crater lake of the Galápagos archipelago.

Background: A new species of a Neotropical diaptomid copepod is described based on individuals recovered from a small, almost forgotten collection of unique plankton samples from El Junco, a crater lake in San Cristóbal island, Galápagos archipelago. This copepod was regularly reported (1966-2004) as an abundant zooplankter in the lake, but it was not found in subsequent plankton surveys (2007-2018), and its specific identity remained unknown. In 2020, it was declared extinct because of introduced fish predation, rotenone treatment, and other major disturbances. The taxonomic examination of these invaluable specimens allowed us to recognize them as representing an undescribed species of the freshwater diaptomid genus Mastigodiaptomus Light, 1939. Methods: Here, we describe the new species from El Junco crater lake, located in the San Cristóbal island a part of the Galápagos archipelago, collected with plankton nets. The description is based on detailed morphology, based on SEM and light microscopy. Results: The taxonomic examination of these invaluable specimens allowed us to recognize them as representing an undescribed species of the freshwater diaptomid genus Mastigodiaptomus Light, 1939. The new species was readily assigned to this genus and is distinguished from its known congeners by details of (1) the male right fifth leg terminal claw and aculeus, (2) spiniform processes pattern of the right geniculate antennule segments 10-16, (3) length and structure of the spiniform process of the antepenultimate segment of the male right antennule, and (4) details of the dorsal process on the female fourth pediger. This finding represents the first report of this Neotropical copepod genus outside its original biogeographic region, the third species of a diaptomid copepod reported from insular freshwater systems, the southernmost record of Mastigodiaptomus, and the only freshwater calanoid in the Galápagos. The intriguing presence of this chiefly Neotropical copepod genus here could be related either to (1) human agency linked to pirate activities, commercial travelling by Spaniard ships, whaling activities, and intense tortoise hunting in San Cristóbal island. In the past, El Junco was the only freshwater source 600 nautical miles around, or (2) zoochory of resistant dormant stages passively transported by more than 65 migrating bird species known to settle in San Cristóbal. These two hypotheses cannot be properly tested at this time, so the explanation of the presence of this copepod will remain as a new open question in the fascinating natural history of the Galápagos.

Cohabitation with aggressive hosts: description of a new microhisterid species in nests of a ponerine ant with ecological notes.

A new clown beetle species, Bacanius neoponerae, is described from Mexican nests of the arboreal ponerine ant Neoponera villosa found in the tank bromeliad Aechmea bracteata. Adult beetles were found in brood chambers or inner refuse piles, but also outside the ant nests, in decaying organic matter between the bromeliad leaves. No direct interactions between ants and microhisterid beetles could be observed. Several lines of evidence suggest a close relationship either with the ants, specific microhabitats within the ant nests or the bromeliads. Sample site elevation, colony size, monthly rainfall and collecting site were the main variables predicting the association. Almost half of the N. villosa colonies were associated with the microhisterids, and larger colonies favored their presence, especially during the driest months of the year. Two specimens were found in a nest of another ant species, Camponotus atriceps, also inhabiting A. bracteata. The new species is the seventh of the genus Bacanius reported from Mexico. This is the second time a species of this genus is associated with ants, and the fourth record of a histerid beetle cohabiting with ponerine ants. The small size of these beetles and their very protective body structure may facilitate their cohabitation with such aggressive hosts.

Holothuriophilus trapeziformis Nauck, 1880 (Decapoda: Pinnotheridae) from the Pacific coast of Mexico: taxonomic revision based on integrative taxonomy.

BACKGROUND: Holothuriophilus trapeziformis Nauck, 1880 is a holothurian-dweller pinnotherid crab representing one of the two species of the genus distributed along the Pacific coast of Mexico and Chile, respectively. While the parasitic ecological interaction with its host is well established, the morphology of the male remains unknown, and DNA information for the species is not available. Furthermore, the only morphological trait separating both species of the genus is subjective and corresponds to the presence or absence of a gap between the fingers of the chelae. Our goal is to complete and clarify the taxonomic status of H. trapeziformis and describe the male morphology with the use of the integrative taxonomy, providing additional characters to differentiate this species. METHODS: We collected new biological material in the Pacific coast of Mexico including the topotypes. We also reviewed material from national collections to integrate morphology (based on a complete and detailed description and illustration of the species using light microscopy), ecological data (based on the identification of the host and the place where it was located within the host), and the mtCOI gene information (commonly known as DNA barcode) to differentiate Holothuriophilus trapeziformis from other related crabs. RESULTS: This species presents marked sexual dimorphism only in the primary sexual characters. For the first time we describe morphological variability of traditionally stable characters. In addition to the gap between the fingers of the chelae, Holothuriophilus trapeziformis differs from H. pacificus (Poeppig, 1836) by their ornamentation, the shape of the male abdomen, and the gonopod. Cytocrome Oxidase 1 gene (COI) distance divergence was >3% between both Holothuriophilus species forming a clear clade. DNA barcoding indicates only one taxon, with a maximum divergence of 2.2%. All the specimens have the same Barcode Index Number (BIN; BOLD: ADE9974). All the hosts for H. trapeziformis were identified as Holothuria (Halodeima) inornata Semper, 1868; the presence of the crab in the host's coelomic cavity was confirmed, and for the first time we found it within the intestine. The geographical distribution is the Pacific coast of Mexico. Based on the data presented here, the taxonomic status of Holothuriophilus trapeziformis is now complete.

A new species of Scapholeberis Schoedler, 1858 (Anomopoda: Daphniidae: Scapholeberinae) from the Colombian Amazon basin highlighted by DNA barcodes and morphology.

BACKGROUND: The Amazon basin is recognized as one of the most complex and species-rich freshwater environments globally. The diversity of zooplankton here remains unknown, with many species undescribed. METHODS: Here, we describe a new species of Scapholeberis Schoedler, 1858 (Cladocera: Anomopoda: Daphniidae: Scapholeberinae) from the Colombian Amazon Basin, collected with recently designed light traps. The description is based on detailed morphology (based on SEM and light microscopy) of parthenogenetic females, ephippial females, males, and molecular data based on the COI gene. RESULTS: Scapholeberis yahuarcaquensis n. sp. has a combination of characters present in Scapholeberis kingi Sars, 1888 and Scapholeberis armata freyi Dumont & Pensaert, 1983. These are a trilobate rostrum, with the middle lobe well developed with sides straight to relatively rounded, the presence of an elongated slit frontal head pore, a dorsal pore in the juncture of the cephalic shield and the valves, and a single denticulate membrane at the posterior rim of the valves, with stronger setae in the last third. The unique characters of the parthenogenetic females are ventral sucker with delicate triangles. Each has a filament-like projection in the lamellae's inner side and an external section forming convex folds with denticle-like projections in the middle zone of the sucker-plate. There is a peculiar pitted sculpture in the ephippial females and a strong projection in the front of it. The male hook on the limb I with a blunt tip, a quirky lamella-like outgrow in the proximal side, and a paddle with well-developed spines scattered on its surface. The ventral sucker-lamellae in the male is much more developed than the female. The COI gene sequences showed an interspecific mean genetic divergence of 16.4% between S. yahuarcaquensis n. sp. and the closest species S. freyi from Mexico, supporting our results. A coalescence analysis and Barcode Index Number also support the new species based on the DNA sequences. New methods of collecting and integrative biology will give important support to recognize the fauna from the Amazon Basin, one of the most important sources of fresh water in the world that remains unknown in many respects.

Remarks on Mastigodiaptomus (Calanoida: Diaptomidae) from Mexico using integrative taxonomy, with a key of identification and three new species.

BACKGROUND: In Mexico, species of four families of free-living calanoid copepods have been recorded as inhabitants of several freshwater systems. These families are Centropagidae, Temoridae, Pseudodiaptomidae and Diaptomidae. The genera Leptodiaptomus and Mastigodiaptomus are the most speciose diaptomid genera in Mexico, and they inhabit natural and artificial lakes, ephemeral ponds, springs, and caverns. Leptodiaptomus is considered as an endemic Nearctic genus, whereas Mastigodiaptomus is a widely distributed Neotropical genus in the southern USA, Mexico, the Caribbean Islands and Central America. Based on new and recent evidence, Mastigodiaptomus diversity has been underestimated: six species of the genus were known before 2000. In this work three new Mastigodiaptomus species have been described from different regions of Mexico by using integrative taxonomy. We also gave amended diagnosis of M. nesus Bowman (1986) and M. patzcuarensis s. str. (Kiefer, 1938). METHODS: In this work, the taxonomic status of the species was clarified using modern, integrative method based on the COI gene as a DNA marker, plus micro-structural analysis (based on SEM and ligth microscopy). RESULTS: Three new species of Mastigodiaptomus were described based on genetic and morphological analyses: M. alexei sp. n., M. ha sp. n. and M. cihuatlan sp. n. Also amended description of M. nesus, morphological variation of M. patzcuarensis s. str., and a comparison of them with all known sequences within the genus are provided. These new findings show that in Mastigodiaptomus differences in several cuticular microstructures of several appendages (such as the antennules, the fifth legs, or the urosomites of these copepods) agree with the interspecific genetic divergence >3% observed in sequences of the COI gene, and the integration of this information is a powerful tool in species delineation.

DNA Barcoding as a Diagnostic Tool of a Rare Human Parasitosis: The First Case of Lagochilascaris minor in Quintana Roo, Mexico.

Recently, DNA barcoding based on the mitochondrial gene cytochrome c oxidase subunit 1 (COI) has become a widespread tool to identify animals. Its use with parasites of humans has been limited with some groups of nematodes where the amplification of this gene has been difficult. In this study, we present the first COI barcode sequence of a rare parasite from tropical regions, Lagochilascaris minor, which parasitized a human host from Quintana Roo, southern Yucatán Peninsula, Mexico. Destruction of the mastoid apophysis in the lateral sinus and cerebellar involvement were observed at the site of infection. After a radical mastoidectomy and a treatment with 200 mg oral albendazole for 63 days, the patient completely recovered. Lagochilascaris minor was identified based on the ratio between length of spicules and ejaculatory duct, shape of eggs, and host, as well as comparison with its congeners. The mode of infection is unknown, although it could be after direct exposure to eggs or consumption of uncooked wild meat. Morphology of adults is demonstrated using scanning electron microscopy, and high-quality sequences of COI barcode are presented from amplifications using semi-degenerate primers designed for micro-crustaceans. DNA barcoding proved to be a reliable identification method for L. minor. A comparison of the sequences for this species with 81 ascaridoids obtained from the Barcode of Life Database places it in a unique clade most closely related to Baylisascaris procyonis. Future diagnosis of larval and adult stages of L. minor using DNA barcoding will allow the recognition of its infection parameters, transmission, and precise epidemiology. Reports of lagochilascarosis in the Yucatán Peninsula have been occurred over the last decade, suggesting it is an emerging zoonotic disease in the region.

Using eDNA to biomonitor the fish community in a tropical oligotrophic lake.

Environmental DNA (eDNA) is an effective approach for detecting vertebrates and plants, especially in aquatic ecosystems, but prior studies have largely examined eDNA in cool temperate settings. By contrast, this study employs eDNA to survey the fish fauna in tropical Lake Bacalar (Mexico) with the additional goal of assessing the possible presence of invasive fishes, such as Amazon sailfin catfish and tilapia. Sediment and water samples were collected from eight stations in Lake Bacalar on three occasions over a 4-month interval. Each sample was stored in the presence or absence of lysis buffer to compare eDNA recovery. Short fragments (184-187 bp) of the cytochrome c oxidase I (COI) gene were amplified using fusion primers and then sequenced on Ion Torrent PGM or S5 before their source species were determined using a custom reference sequence database constructed on BOLD. In total, eDNA sequences were recovered from 75 species of vertebrates including 47 fishes, 15 birds, 7 mammals, 5 reptiles, and 1 amphibian. Although all species are known from this region, six fish species represent new records for the study area, while two require verification. Sequences for five species (2 birds, 2 mammals, 1 reptile) were only detected from sediments, while sequences from 52 species were only recovered from water. Because DNA from the Amazon sailfin catfish was not detected, we used a mock eDNA experiment to confirm our methods would enable its detection. In summary, we developed protocols that recovered eDNA from tropical oligotrophic aquatic ecosystems and confirmed their effectiveness in detecting fishes and diverse species of vertebrates.

Brachionus paranguensis sp. nov. (Rotifera, Monogononta), a member of the L group of the Brachionus plicatilis complex.

The Brachionus plicatilis complex represents the most studied group of rotifers, although the systematics of the species complex has not been completely clarified. Many studies have been conducted trying to explore the diversity within the complex, leading to the recognition of three major morphotypes: large (L), small-medium (SM), and small (SS). Currently six species have been described and classified under these types and another nine taxa have been identified but not formally described. Within the L group, three species have been officially described [B. plicatilis s.s. (L1), B. manjavacas (L2), and B. asplanchnoidis (L3)], while a formal description of L4, unofficially known as B. 'Nevada', is still lacking. In the present study, a new species, Brachionus paranguensis sp. nov., is formally described and presented as a representative of the L4 clade. The species has been named after a high altitude saline crater lake from Central Mexico, where the specimens were collected. An integrated approach using DNA taxonomy through COI and ITS1 markers, morphology, and ecology was used to confirm the identity of the new species.

Improved protocols to accelerate the assembly of DNA barcode reference libraries for freshwater zooplankton.

Currently, freshwater zooplankton sampling and identification methodologies have remained virtually unchanged since they were first established in the beginning of the XX century. One major contributing factor to this slow progress is the limited success of modern genetic methodologies, such as DNA barcoding, in several of the main groups. This study demonstrates improved protocols which enable the rapid assessment of most animal taxa inhabiting any freshwater system by combining the use of light traps, careful fixation at low temperatures using ethanol, and zooplankton-specific primers. We DNA-barcoded 2,136 specimens from a diverse array of taxonomic assemblages (rotifers, mollusks, mites, crustaceans, insects, and fishes) from several Canadian and Mexican lakes with an average sequence success rate of 85.3%. In total, 325 Barcode Index Numbers (BINs) were detected with only three BINs (two cladocerans and one copepod) shared between Canada and Mexico, suggesting a much narrower distribution range of freshwater zooplankton than previously thought. This study is the first to broadly explore the metazoan biodiversity of freshwater systems with DNA barcodes to construct a reference library that represents the first step for future programs which aim to monitor ecosystem health, track invasive species, or improve knowledge of the ecology and distribution of freshwater zooplankton.

The Rotifer fauna of Guatemala and Belize: survey and biogeographical affinities.

Rotifer samples were obtained from 29 localities in northern Guatemala and central-southern Belize during March 2000 and June 2001. A total of 119 species were identified. Ten selected taxa are illustrated and commented: Euchlanis semicarinata, Lepadella apsicora, L. cryphaea, Lecane curvicornis f. lofuana, L. whitfordi, Monommata maculata, Scaridium bostjani, Trichocerca elongata f. braziliensis, and Z. hollaerti. The species Lepadella rhomboidula is a first record for the American Continent. The species are 71% cosmopolitan, 6 % tropicopolitan, and 4.2 % restricted to the subtropics. The Guatemala species number range was Petén-Itza lake (53 taxa), and Raxruja pool (three). La Democracia pool (49 taxa), and the Blue Hole sink-hole (six species) were the extremes in Belize. In total, 68 of the recorded taxa are new for Guatemala and 91 for Belize. Additionally, 47 species are registered by the first time in Central America. A comparison between these two countries and Mexico revealed that the south part of the latter conform a cluster with them, emphasizing the transitional character of this region between the Nearctics and the Neotropics. Furthermore, Guatemala and Belize have differences in species assemblages, as a response to the nature of their particular environments and topographical accidents.

An example of how barcodes can clarify cryptic species: the case of the calanoid copepod Mastigodiaptomus albuquerquensis (Herrick).

BACKGROUND: The freshwater calanoid Mastigodiaptomus is a genus with high richness in the Americas and is composed of nine species, seven recorded in Mexico and four that are apparently endemic to small areas. Mastigodiaptomus albuquerquensis is a common, widely distributed species ranging from the southern USA to Central America. This species can be easily identified by a notable butterfly-like sclerotization on the basis of the right fifth leg of males. Nevertheless, morphological differences observed among populations throughout this species distributional range have led to the description of several related species or subspecies, such as M. albuquerquensis patzcuarensis from Lake Pátzcuaro in the Central Plateau of Mexico. METHODS: Genetic results based on barcodes, morphology based on scanning electron and light microscopy images, and morphometric analyses were used to describe cryptic species within the M. albuquerquensis complex. RESULTS: The morphological analyses coincided partially with the genetic markers, suggesting the existence of at least two sibling species: M. albuquerquensis s. str. and M. patzcuarensis. A third species was genetically separated but was morphologically indistinguishable from the M. patzcuarensis group. CONCLUSIONS: Hidden diversity has been a major problem in establishing real patterns of species distribution and genetic acquisition from megadiverse hotspots such as Mexico, where the Nearctic and the Neotropical regions of the Americas meet. Barcodes can help taxonomists to reveal and formally name these new species. Here, we describe two of three potential species highlighted by the use of barcodes: M. albuquerquensis s. str. in the northern semi-desert and M. patzcuarensis on the Central Plateau at more than 2000 m above sea level.

A new set of primers for COI amplification from freshwater microcrustaceans.

Despite the contribution of DNA barcoding towards understanding the biodiversity and distribution of species, the success of COI amplification has been quite variable when it comes to freshwater zooplankton (Elías-Gutiérrez & Valdez-Moreno 2008; Jeffery et al. 2011). Some genera of microcrustaceans seem to be more difficult to amplify than others. For example, Macrothrix, Scapholeberis, Diaphanosoma and cyclopoids have yielded limited results. Among several possible reasons for the inability to barcode freshwater microcrustaceans is that there does not exist a specific set of primers for COI amplification. To this end, we developed a zooplankton - specific set of primers, which significantly increased average amplification success (20% increase). With these primers, we observed an overall success of over 70% for Sididae and Chydoridae, and more than 80% for Daphniidae, Moinidae, Bosminidae, Macrothricidae, Ilyocryptidae and Diaptomidae. We also demonstrate a simple alteration to a common specimen fixation method that increases the overall recovery of barcodes from freshwater zooplankton. Collectively, we believe our results will greatly aid the recovery of barcodes from these difficult groups.

Species diversity and phylogeographical affinities of the Branchiopoda (Crustacea) of Churchill, Manitoba, Canada.

The region of Churchill, Manitoba, contains a wide variety of habitats representative of both the boreal forest and arctic tundra and has been used as a model site for biodiversity studies for nearly seven decades within Canada. Much previous work has been done in Churchill to study the Daphnia pulex species complex in particular, but no study has completed a wide-scale survey on the crustacean species that inhabit Churchill's aquatic ecosystems using molecular markers. We have employed DNA barcoding to study the diversity of the Branchiopoda (Crustacea) in a wide variety of freshwater habitats and to determine the likely origins of the Churchill fauna following the last glaciation. The standard animal barcode marker (COI) was sequenced for 327 specimens, and a 3% divergence threshold was used to delineate potential species. We found 42 provisional and valid branchiopod species from this survey alone, including several cryptic lineages, in comparison with the 25 previously recorded from previous ecological works. Using published sequence data, we explored the phylogeographic affinities of Churchill's branchiopods, finding that the Churchill fauna apparently originated from all directions from multiple glacial refugia (including southern, Beringian, and high arctic regions). Overall, these microcrustaceans are very diverse in Churchill and contain multiple species complexes. The present study introduces among the first sequences for some understudied genera, for which further work is required to delineate species boundaries and develop a more complete understanding of branchiopod diversity over a larger spatial scale.