Abstract Two new species of Hyalella S.I. Smith, 1874 are described from state of Jalisco, Mexico. Hyalella marysolae sp. nov. can be identified by the presence of small projections or carinae on pleonites 1−2, with the first antenna being composed of 12 articles and the second antenna being composed of 15 articles. The first maxilla bearing 2−3 distal pappose setae, and the propodus in male first gnathopod is hammer-shaped. Conversely, in H. morronei sp. nov., dorsal projections or carinae are absent on pleonites 1−2, with the first antenna being composed of 10 articles and the second antenna of 14 articles. The first maxilla always bears two distal pappose setae, and the propodus in male first gnathopod is hatchet-shaped. Both species are distinguishable from other Hyalella species found in Mexico by the second antenna. In these two species, the second antenna is approximately half as long as the total body length, and the peduncle comprises 14 −15 articles; whereas, in other Mexican species, it is shorter and composed of maximum 12 articles. Here, we add two species to the four previously described in Mexico as it is necessary to increase the knowledge of the alpha taxonomy of this group of crustaceans and compensate for the biodiversity of the genus being underestimated.

Resumen Cambarellus chapalanus es una especie endémica de la zona del Lago de Chapala en México y el conocimiento sobre su biología y ecología es escaso. Se evaluó su dinámica poblacional con base en el crecimiento individual, mortalidad, producción y productividad. Para ello, se colectaron individuos entre noviembre 2011 y octubre 2012, en charcas localizadas en la Sierra San Juan Cosalá, Jalisco, México. Las variables abióticas de las charcas (profundidad, temperatura, pH, precipitación y evaporación) presentaron variaciones significativas durante el estudio. La abundancia fue similar a lo largo del año, pero se relacionó con el incremento de la temperatura y evaporación de las charcas. Además, los machos fueron más abundantes que las hembras. El crecimiento fue rápido y oscilatorio con fases lentas en periodos de lluvias. La mortalidad fue alta e inició en tallas medianas; sin embargo, su alta producción somática también generó una alta productividad poblacional. En general, los parámetros de C. chapalanus mostraron patrones normales para una poblacional natural; sin embargo, estuvieron fuertemente influenciados por la temperatura y el volumen de las charcas, probablemente debido a que es una población aislada en la Sierra San Juan Cosalá.

Abstract Cambarellus chapalanus is an endemic species of the area around Lake Chapala in Mexico and knowledge about its biology and ecology is scarce. Its population dynamics were evaluated based on individual growth, mortality, production, and productivity. For this, individuals were collected between November 2011 and October 2012, in ponds located in the Sierra San Juan Cosalá, Jalisco, Mexico. The abiotic variables of ponds (depth, temperature, pH, precipitation, and evaporation) presented significant variations during the study. Abundance was similar throughout the year but was related to an increase in temperature and evaporation of ponds. Furthermore, males were more abundant than females. Growth was fast and oscillatory with slow phases in rainy periods. Mortality was high and started at medium sizes; however, high somatic production also generated high population productivity. In general, the parameters of C. chapalanus showed normal patterns for a natural population; however, were strongly influenced by temperature and pond volume, probably because it is an isolated population in Sierra San Juan Cosalá.

Abstract A new species of the pinnotherid crab genus Austinixa from La Cruz de Huanacaxtle, Nayarit, Mexico is described. The new species is closely related to Austinixa roblesi Palacios Theil and Felder, 2020, however these can be distinguished mainly by the shape of the male pleon and telson, gonopod and chelae. In addition, four new records of distribution of Austinixa felipensis Glassell, 1935 are added. The species is known previously from the type locality to the north of the Gulf of California and the Pacific coast of El Salvador and Nicaragua. The new collection sites are located on the eastern coast of the Gulf of California and the states of Nayarit and Jalisco, Mexico.

Abstract: A number of specimens of the Californian lancelet, Branchiostoma californiense Andrews, 1893 were found in Isla Melendres, Sinaloa and Bahía Chamela, Jalisco, in the Mexican Pacific. The specimens were collected with a biological dredge on sandy bottoms. Some morphometric and meristic characters of the collected specimens are described and discussed herein. This is the first record of the species for the Bahía Chamela in the central Mexican Pacific and second for the Sinaloa state in the Gulf of California, confirming their distribution along the Eastern Pacific from the coast of California coast, USA to Panama. However, an extensive area of the southern Mexican Pacific (~1,500 km from Colima to Chiapas) have scarce records of this species, this possibly due to the lack of sampling effort on this group in the area.

Resumen: Algunos especímenes de la lanceta de California Branchiostoma californiense Andrews, 1893 fueron encontrados en la isla Melendres (Sinaloa) y en la bahía Chamela (Jalisco), en el Pacífico mexicano. Los ejemplares fueron recolectados con una draga biológica en fondos arenosos. Algunos caracteres morfométricos y merísticos de los especímenes encontrados son descritos y discutidos en este trabajo. Este es el primer registro de la especie para la bahía Chamela en el Pacífico central mexicano y el segundo para el estado de Sinaloa, dentro del golfo de California, lo que permite confirmar su distribución a lo largo del Pacífico oriental desde la costa de California (EUA) hasta Panamá. Sin embargo, en una extensa área del sur del Pacífico mexicano (~1,500 km desde Colima hasta Chiapas) se encuentran escasos registros de esta especie, posiblemente por la falta de esfuerzo de muestreo sobre este grupo en esta área.

Abstract: During a faunistic survey of the islands and islets of Bahía Chamela, Jalisco, Mexico, 40 species of caridean shrimps belonging to 5 families were collected; the Alpheidae with 3 genera and 20 species was the best represented, followed by the Palaemonidae with 10 genera and 12 species. Other families found were: Hippolytidae (3 genera, 5 species), Gnathophyllidae (1 genus, 1 species), and Processidae (1 genus, 2 species). Compared with the rest of the Mexican Pacific, the number of species found represents 44% of the genera and 45% of the benthic species of caridean shrimps reported to date. Ninety percent of the species collected correspond to new records for Bahía Chamela. Two species, Neopontonides henrivronprahli from Costa Rica and Colombia, and Thor cocoensis from Costa Rica and the Galápagos Islands, are recorded for the first time since their original description, extending their distribution range by ca 16 and 14 degrees of latitude to the north, respectively.

Resumen: Como resultado de un estudio faunístico realizado en la bahía Chamela, Jalisco, se recolectó un total de 40 especies de carideos pertenecientes a 5 familias; los Alpheidae con 3 géneros y 20 especies fueron los mejor representados, seguidos por los Palaemonidae con 10 géneros y 12 especies. Otras familias fueron: Hippolytidae (3 géneros y 5 especies), Gnathophyllidae (1 género, 1 especie) y Processidae (1 género, 2 especies). Comparado con el resto del Pacífico mexicano, el número de especies encontradas representan el 44% de los géneros y el 45% de las especies de camarones carideos bentónicos registrados hasta la fecha. El 90% de las especies recolectadas corresponde a nuevos registros para la bahía Chamela. Dos especies, Neopontonides henrivronprahli de Costa Rica y Colombia, y Thor cocoensis de Costa Rica y las islas Galápagos, se registran por primera vez desde su descripción original, extendiendo su distribución aproximadamente 16 y 14 grados de latitud al norte, respectivamente.

Analysis of wild phyllosoma of Panulirus inflatus (Bouvier, 1895) and P. gracilis Streets, 1871 determined the morphological structures having taxonomic value for differentiation of the two species, in addition to the structures described previously. Of 54 phyllosoma, species identity was confirmed by PCR-restriction fragment length polymorphism (RFLP) on 42 P. inflatus and 4 P. gracilis, for which morphology and morphometric measurements were taken. Morphological analysis found subexopodal spines, spines at the base of pereopods 1 and 2, and the mandibles are structures of taxonomic value for differentiating the two species. Morphometric data did not allow differentiation.

Twelve species of hermit crabs were identified from material recollected in Chamela Bay, Jalisco. The family Diogenidae was the best represented with 7 species. Nine species represent new records for Chamela Bay and 2 species of the genus Paguristes were found to be undescribed. We found an association of hermit crabs with shells used as home in 29 gastropods; the commonest shells used were Cantharus sanguinolentus (Duclos, 1833) and Mancinella speciosa (Valenciennes, 1832).

Se identificaron 12 especies de cangrejos ermitaños del material recolectado en la bahía Chamela, Jalisco. La familia Diogenidae fue la mejor representada con 7 especies. Nueve especies representan registros nuevos para la bahía y 2 pertenecientes al género Paguristes se descubrió que no han sido descritas. Se encontró asociación de los cangrejos ermitaños con conchas de 29 especies de gasterópodos que utilizaban como habitáculo; las conchas más comunes fueron Cantharus sanguinolentus (Duclos, 1833) y Mancinella speciosa (Valenciennes, 1832).

Material belonging to the genus Processa, held in the Regional Marine Invertebrates Collection in Mazatlán, Mexico, is revised including specimens of the widely distributed P. peruviana, and the scarcely collected P. hawaiensis. For comparative purposes with the specimens from Hawaii and other localities, a detailed description of a male of P. hawaiensis collected in continental Mexico is provided, including illustrations of all appendages. Small differences are noted with previous description and partial redescriptions of this species, including proportion between propodus and dactylus of the fourth pereopod, and between merus and carpus of the right cheliped. In addition, the shape and setation of the first pair of pleopods in the Mexican material differs from the description of P. hawaiensis based on African material.

Specimens of galatheids Janetogalathea californiensis (Benedict, 1902) were collected in the northern portion of the Central Gulf of California and represent the third record for this species in the area. Illustrations of the material collected in the Gulf of California are provided and some differences are noted when compared to the description of the paralec-totypes. Depth range of the species is discussed and set at 87-786 m. The presence of a wide and deep Oxygen Minimum Zone in the area is believed to limit the dispersion of J. californiensis to the south and to deeper water of the gulf.

Especímenes del galateido Janetogalathea californiensis (Benedict, 1902) fueron recolectados en la porción norte del golfo de California central, y representan el tercer registro de esta especie en el área. En base a ilustraciones de material recolectado en el Golfo de California, se indican algunas diferencias con respecto a la redescripción de los paralectotipos. Se discute la distribución batimétrica de la especie de la que se define un intervalo que va de 87 a 786 m de profundidad. Los resultados sugieren que la presencia de una amplia y profunda capa de oxígeno mínimo en el área podría ser la causa que limita la dispersión de J. californiensis hacia el sur y en aguas más profundas del golfo.