New Myloplus from Essequibo River basin, Guyana, with discussion on the taxonomic status of Myleus pacu (Characiformes: Serrasalmidae)

A new species in the serrasalmid genus Myloplus is described from the middle Mazaruni River, Essequibo River basin, Guyana. The new species is similar to Myleus pacu and Myloplus planquettei in its silver to purplish black coloration and its overall morphology, and has a putative syntopic distribution with those species. The new species is, however, readily distinguishable from the other two by meristic counts of the unpaired fins and by differences in color pattern, primarily in males. Additionally, we provide comments on Myleus pacu and other species that have been confounded under that name.(AU)

Uma nova espécie de serrasalmídeo do gênero Myloplus é descrita do médio rio Mazaruni, bacia do rio Essequibo, Guyana. A nova espécie é similar a Myleus pacu e Myloplus planquettei pela sua coloração prateada a preto arroxeado e pela morfologia geral do corpo, e por ter suposta distribuição sintópica com essas espécies. No entanto, a nova espécie é prontamente distinguida dessas duas últimas espécies por contagens das nadadeiras não pares, e por diferenças no padrão de coloração, principalmente nos machos. Adicionalmente, fornecemos comentários sobre Myleus pacu e outras espécies que têm sido confundidas sob esse nome.(AU)

DNA barcoding reveals the diversity of sharks in Guyana coastal markets

A fundamental challenge for both sustainable fisheries and biodiversity protection in the Neotropics is the accurate determination of species identity. The biodiversity of the coastal sharks of Guyana is poorly understood, but these species are subject to both artisanal fishing as well as harvesting by industrialized offshore fleets. To determine what species of sharks are frequently caught and consumed along the coastline of Guyana, we used DNA barcoding to identify market specimens. We sequenced the mitochondrial co1 gene for 132 samples collected from six markets, and compared our sequences to those available in the Barcode of Life Database (BOLD) and GenBank. Nearly 30% of the total sample diversity was represented by two species of Hammerhead Sharks (Sphyrna mokarran and S. lewini), both listed as Endangered by the International Union for Conservation of Nature (IUCN). Other significant portions of the samples included Sharpnose Sharks (23% - Rhizoprionodon spp.), considered Vulnerable in Brazilian waters due to unregulated gillnet fisheries, and the Smalltail Shark (17% - Carcharhinus porosus). We found that barcoding provides efficient and accurate identification of market specimens in Guyana, making this study the first in over thirty years to address Guyana's coastal shark biodiversity.(AU)

Um desafio fundamental para a pesca sustentável e a proteção da biodiversidade nos neotrópicos é a identificação precisa das espécies. A biodiversidade dos tubarões costeiros da Guiana é pouco compreendida, porém essas espécies estão sujeitas tanto à pesca artesanal quanto à pesca industrializada não costeira. Para determinar quais espécies de tubarões são frequentemente capturadas e consumidas ao longo do litoral da Guiana, utilizamos DNA barcoding para identificar espécimes comumente encontrados e adquiridos em mercados. Nós sequenciamos o gene mitocondrial coI para 132 espécimes adquiridos de seis mercados e comparamos estas sequências com as disponíveis no Barcode of Life Database (BOLD) e GenBank. Quase 30% da diversidade total amostrada foi constituída por duas espécies de tubarões martelo (Sphyrna mokarran e S. lewini), ambas listadas como espécies ameaçadas pela UICN. Outras porções significativas da amostragem incluem Cações-Frango (23% - Rhizoprionodon spp.), considerados vulneráveis em águas brasileiras, devido a pesca de arrasto não regulamentada, e o Cação-azeiteiro (17% - Carcharhinus porosus). Descobrimos que o barcoding é uma forma identificação eficiente e precisa para espécimes de mercado na Guiana, tornando este estudo o pioneiro na documentação da biodiversidade dos tubarões costeiros da Guiana.(AU)

Phylogenetic diagnosis and expanded description of the genus Mazarunia Kullander, 1990 (Teleostei: Cichlidae) from the upper Mazaruni River, Guyana, with description of two new species

We expand the description of the genus Mazarunia Kullander, 1990, explore morphological diagnostic characters for the genus and for its sister-group relationship with Guianacara Kullander & Nijssen, 1989 in a phylogenetic context, expand the description of M. mazarunii and describe two new species. Mazarunia can be diagnosed by the combination of numerous anatomical traits, including the unique loss of infraorbital 6, the configuration of the first epibranchial in two of the species, a well-developed posteroventral lateral expansion of the palatine that is largely contiguous with the ectopterygoid, the absence of a suture between the hyomandibular and the metapterygoid, the absence of an interarcual cartilage, fourth ceratobranchial with 2 or 3 tooth plates, a caudally scaled interoperculum, equal-sized scales in the ventral and lateral chest regions, a simple, disjunct pattern of lateral line squamation, and smooth preopercle, supracleithrum and extrascapula. Species of Mazarunia can be further distinguished from species of their sister-genus Guianacara by their distinct color patterns. Mazarunia charadrica, new species, can be distinguished from other species of Mazarunia, among other characters, by approximately equal uncinate process and anterior arm and reduced anteroventral expansion of epibranchial 1 (vs. uncinate process narrower and complete anteroventral expansion in the other two species), a dorso-ventrally flattened maxillary process of the palatine (vs. cylindrical in the other two species), cycloid (vs. ctenoid) scales in the opercular, postorbital, lateral chest and anal-genital regions, the absence of a mid-lateral spot, and a diffuse dark area covering the dorsal portion of the head giving the impression of a "black cap". Mazarunia charadrica has a unique juvenile pattern of seven vertical dark bars partially preserved in adults. Bars 3-6 in antero-caudal direction are most visible in juveniles and medium-sized specimens but become fainter and almost disappear in adults. Many specimens show only bar number 3 (midlateral bar). Mazarunia mazarunii can be distinguished from all other species of Mazarunia by the presence of two foramina (vs. one) on the lateral face of the ascending process of the premaxilla, a lachrymal bone that is longer than deep (vs. deeper than long), an infraorbital 3 that is contiguous but not overlapping with the lachrymal (vs. overlapping), ctenoid scales (vs. cycloid) on the subopercle, interopercle and chest, and by its unique coloration, including complete suborbital and supraorbital stripes, and being the only species of Mazarunia with a discernible lateral band formed by the mid-line blotching pattern associated with lateral bars. In large adults, M. mazarunii has a black or dark bar behind the head that produces the impression of a collar. Mazarunia pala, new species, can be distinguished from its congeners by the absence of a parhypurapophysis, the presence of a dorsal-fin scaly pad with ctenoid scales (vs. no scaly pad in M. charadrica and M. mazarunii), a small suborbital stripe limited to the preopercle, the absence of clearly discernible lateral bars on the body, and by its general pinkish coloration with midlateral spot as the only melanic marking. All known species of Mazarunia are restricted to the upper reaches of the Mazaruni River basin in Guyana.(AU)

Expandimos la descripción del género Mazarunia, exploramos caracteres diagnósticos morfológicos para el género y su relación de grupo hermano con Guianacara en un contexto filogenético, expandimos la descripción de M. mazarunii y describimos dos nuevas especies. Mazarunia se puede diagnosticar por la combinación de numerosos atributos anatómicos, incluyendo la pérdida del infraorbital 6, la configuración del primer epibranquial en dos de las especies, una expansión posteroventral lateral del palatino bien desarrollada y mayormente continua con el ectopterigoide, la ausencia de sutura entre la hiomandíbula y el metapterigoide, la ausencia del cartílago interarcual, 2 a 3 placas dentadas en el cuarto ceratobranquial, la porción caudal del interopérculo escamada, escamas de igual tamaño en el flanco y la región lateral del pecho, un patrón simple y disjunto de escamación en la línea lateral, y preopérculo, supracleitro y extra escápula lisos. Además, todas las especies de Mazarunia se pueden distinguir de especies en su género hermano Guianacara por diferencias de coloración. Mazarunia charadrica, especie nueva, puede distinguirse de otras especies de Mazarunia, entre otros caracteres, por tener un proceso uncinado aproximadamente igual al brazo posterior y expansión anteroventral reducida en el epibranquial 1 (contra proceso uncinado más angosto y expansión anteroventral completa en las otras dos especies), el proceso maxilar del palatino aplanado dorsoventralmente (contra cilíndrico en las otras dos especies), escamas cicloides (contra ctenoides) en las regiones opercular, postorbital, pectoral lateral y génito-anal, la ausencia de mancha mediolateral, y un área oscura difusa cubriendo la porción dorsal de la cabeza dando la impresión de un "sombrero negro". Mazarunia charadrica tiene un patrón único de coloración juvenil con siete barras verticales conservadas parcialmente en los adultos. Las barras 3-6 en dirección anterocaudal son más ...(AU)