Abstract The Gulf of California is known for its high productivity, diversity, and unique oceanography. Based on old and recent contributions, we estimate a richness of 160 copepod species in this province. This work seeks to identify latitudinal and seasonal patterns of the copepod composition, abundance, and diversity in the Gulf of California during 1985. Differences between four zones of the gulf (NGC, CGC, SGC, EGC) and between the cold and warm seasons were hypothesized, based on taxonomic and ecological data. Samples were collected during the CORTES cruises (1985), which also measured salinity, temperature, and dissolved oxygen at each station. We analyzed the latitudinal and seasonal variation of the copepod community with multivariate analyses (NMDS-PCA) and correlated these with the environmental data (CCA). Seventy-nine copepod species were identified, averaging 265,649 and 98,885 ind/10 m3 in the cold and warm seasons, respectively. Only 53 of these occurred in both seasons, indicating seasonal change in species composition. Composition and diversity varied latitudinally in the cold season (P < 0.05 in all comparisons but CGC vs. SGC), but not in the warm season (except NGC vs. the rest of the gulf). There was seasonal change in the composition and the abundance (P < 0.005 cold vs. warm season). Richness and diversity were negatively correlated with salinity (decreasing from the north of the gulf); the abundance and composition were mainly affected by the shift in temperature. These patterns also match the phytoplankton abundance and size structure in the gulf, probably the main factors affecting copepod distribution.

Abstract After a study of the type specimens, as well as supplementary materials of the eastern Pacific hermit crab Pagurus gladius (Benedict, 1892), this taxon is transferred to the genus Spathapagurus Lemaitre and Felder, 2011, and a full redescription and illustrations are presented. Morphological similarities of Benedict’s taxon with three other eastern Pacific species (Pagurus albus (Benedict, 1892), Pagurus perlatus H. Milne Edwards, 1848, and Pagurus pseudoalbus Ayón-Parente and Wehrtmann, 2019) are summarized. While examining museum specimens during this study, one female specimen representing a new species of Pagurus Fabricius, 1775, was discovered. This new species, named Pagurus marysolae sp. nov., is fully described and illustrated, and is assigned to Group II (“exilis”) of Pagurus.

Abstract The offshore mysid Neobirsteiniamysis inermis (Willemoes-Suhm, 1874) is reported for the first time in western Mexico. A large series of specimens (168 specimens: 44 males, 124 females) was obtained from samples taken with a large benthic sled in as many as 28 localities distributed off the west coast of the Baja California Peninsula (15), in the Gulf of California (11), and off SW Mexico (2). Only one ovigerous female was collected. A complete description of the material, based on a mature specimen, is provided, including SEM images of the mandibles, which are described in detail, and of the eyes.

Abstract A new genus of Mysidae, Neobirsteiniamysis, was proposed in early 2020 for the nomen nudum Birsteiniamysis Tchindonova. This new genus, however, was not available for being published online only. The new genus is hereby officially registered in Zoobank and validated.

Abstract A large number of specimens (2765) of the acorn barnacle Balanus trigonus Darwin, 1854, were observed on the spiny lobster Panulirus gracilis Streets, 1871, in western Mexico, including recently settled cypris (1019 individuals or 37%) and encrusted specimens (1746) of different sizes: <1.99 mm, 88%; 1.99 to 2.82 mm, 8%; >2.82 mm, 4%). Cypris settled predominantly on the carapace (67%), mostly on the gastric area (40%), on the left or right orbital areas (35%), on the head appendages, and on the pereiopods 103. Encrusting individuals were mostly small (84%); medium0sized specimens accounted for 11% and large for 5%. On the cephalothorax, most were observed in branchial (661) and orbital areas (240). Only 40-41 individuals were found on gastric and cardiac areas. Some individuals (246), mostly small (95%), were observed on the dorsal portion of somites. Of the encrusting individuals, 18% were dead with no clear pattern in localization, but less common (7%) on dorsal than on lateral portions (right, 18%; left, 32%). Larger specimens (up to 11 mm) were observed in other lobsters from different catches. Previous presence of Cirripedia in decapod crustaceans, size range in the material examined, settlement patterns, and growth of the barnacles are discussed.

Abstract A series of specimens of Malacoplax californiensis (Lockington, 1877) is reported from the Gulf of California, significantly increasing the known localities for the otherwise rarely reported species from 3 to 12. Depth range is increased to 110‒114 m on the continental shelf. Environmental conditions associated with the crabs were: 12.4‒27.0°C; 1.9‒5.0 ml/l O2; 58‒98% sandy sediments. Males and females were sexually distinct even at small sizes (4.2 mm and 3.5 mm CW, respectively). Two small specimens were infested with a rhizocephalan, a condition not reported previously for this species of panopeid.

Abstract Bathybembix bairdii, the Baird's top shell, is reported for the first time from off the Baja California Peninsula west coast and the southwestern coast of Mexico, at depths of 710-2,093 m. Environmental conditions measured near bottom were: 2.10 to 5.81 °C, 34.40 to 34.63 (salinity), and <0.12-0.90 ml L-1 O2. The species was found mostly in muddy sediments dominated by silt (56.5-87.0%) (Baja California) or in sediments with a significant proportion of sand (63.5 to 88.5%) (southwestern Mexico). Shell height varied from 10.0 to 53.7 mm, with high proportion of large specimens in shallower water off Baja California. Densities varied from 1.75 to 207.45 org. ha-1 off Baja California and from 5.25 to 50.72 org. ha-1 in southwestern Mexico. Estimated maximum biomass occurred off southwestern Mexico (2.2 kg ha-1). Relationship between height and total weight (shell plus soft part) and between height and soft part weight were both highly correlated (R2: 0.933 and 0.928, respectively). Soft part weight varied from 29 to 62% of total weight and proportion increased with size. Mega invertebrate species associated with B. bairdii included 47% of decapod crustaceans, 35% of echinoderms, and 18% of mollusks. As a by-catch species regularly found in deep-water trawls, B. bairdii could represent a valuable resource for human consumption.

Resumen Bathybembix bairdii es reportado por primera vez para la costa oeste de la península de Baja California y la costa suroeste de México, a una profundidad de 710 a 2.093 m. Las condiciones ambientales medidas cerca del fondo fueron: 2,10 a 5,81 °C, 34,40 a 34,63 (salinidad) y <0,12-0,90 ml L-1 de O2. La especie se encontró principalmente en sedimentos fangosos dominados por limo (56,5-87,0%) (Baja California) o en sedimentos con una proporción significativa de arena (63,5 a 88,5%) (suroeste de México). Las tallas de las conchas variaron de 10,0 a 53,7 mm, con alta proporción de especímenes grandes en aguas menos profundas de Baja California. Las densidades variaron de 1,75 a 207,45 org. ha-1 en Baja California y de 5,25 a 50,72 org. ha-1 en el Suroeste de México. La biomasa máxima estimada se produjo en el suroeste de México (2,2 kg ha-1). La relación entre la altura y el peso total (concha más parte blanda) y entre la altura y el peso de la parte blanda estuvieron altamente relacionadas (R2: 0,933 y 0,928, respectivamente). El peso de la parte blanda varió de 29 a 62% del peso total y la proporción aumentó con el tamaño. Las especies de mega invertebrados asociadas con B. bairdii incluían el 47% de crustáceos decápodos, 35% de equinodermos y 18% de moluscos. Como especie de captura secundaria encontrada regularmente en las redes de arrastre en aguas profundas, B. bairdii podría representar un valioso recurso para el consumo humano.

Abstract Two species of isopods of the family Idoteidae were collected in the same sample, among sea grasses, in the northern Gulf of California, Mexico. The first species, Synidotea harfordi Benedict, 1897, was more abundant (46 specimens) than the second species, Eusymmerus antennatus Richardson, 1899 (eight specimens). Synidotea harfordi has previously been considered uncommon in the Gulf of California, and more like a component of warm-temperate to colder-water fauna. The male of E. antennatus has not been illustrated but SEM photographs are provided and show angular margins of the first three pereonites and a sharply bent lateral margin of the telson. Females also have angular first pereonites. All previous illustrations show rounded pereonites margins. Buccal appendages of E. antennatus are illustrated and compared with previous descriptions.

Abstract A series of specimens of the fish external parasite Rocinella murilloi Brusca and Iverson, 1985, is reported from 12 localities off western Mexico. These records are the first for southwestern Mexico (four) and add six new localities off the west coast of the Baja California Peninsula where the species was known from a single record. The specimens were recovered from bottom-operated nets, between 700 and 1235 m, slightly shallower than previous records. Environmental conditions confirm the presence of R. murilloi below the core of the Oxygen Minimum Zone, and this species appears to be highly tolerant to moderate to severe hypoxic conditions. General distribution of the species in the eastern Pacific is presented.

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.

A small series of specimens of Chorilia turgida Rathbun, 1924 is reported from off the west coast of the Baja California Peninsula, Mexico, in depth of 734 to 1,433 m. It was previously known from Monterey Bay to off San Diego, California, USA, and from one isolated record from the Cortés Bank, Mexico. The material was collected in cold water (3.16-5.48 °C) with mild to severe hypoxic conditions (0.25-0.90 ml/l O₂).

Se señala la captura de una pequeña serie de ejemplares de Chorilia turgida Rathbun, 1924 recolectados frente a la costa oeste de la península de Baja California, México, a profundidades entre 734 y 1,433 m. Se conocía previamente desde la bahía de Monterrey hasta la altura de San Diego, California, EE.UU., y con un solo registro cerca del banco de Cortés, México. El material se recolectó en aguas frías (3.16-5.48 °C) en condiciones de hipoxia de leves a severas (0.25-0.90 ml/l O₂).

This paper presents details regarding the collections and records of H. strigillata in the Bay of Mazatlán, SE Gulf of California, Mexico. Samples of H. strigillata were obtained in this bay and suroundings area during different periods and deposited in the collection of UNAM, Mazatlán. Morphometric data, distribution, biological and ecological data were furnished.

A total of six species of pelagic shrimps were collected during the TALUD XIV cruise aboard the R/V "El Puma", in the northern Gulf of California, in April 2011, including two species of Dendrobranchiata [Eusergestes similis (Hansen, 1903) and Sergia phorca (Burkenroad, 1940)], and three species of Caridea [Pasiphaea americana Faxon, 1893, P. emarginata Rathbun 1902, and P. pacifica Rathbun, 1902]. Additional specimens of the previously reported Maryprocessa pippinae (Wicksten & Méndez, 1985) were also found among the samples. Most frequently collected species were P. americana (50% of total) and P. pacifica (36.6%). Most numerous species in the samples were P. pacifica, P. americana and E. similis. Some minor morphological differences not previously recorded in specimens of Pasiphaea pacifica collected elsewhere were detected. These differences might correspond to an intraspecific variation.

A brief synopsis on the characteristics of decapod crustaceans and on recent classification proposals is presented. Through an exhaustive compilation of decapod crustacean records from Mexico, a species list was built for the continental, Caribbean, Gulf of Mexico and Pacific regions. A total of 1 775 species was obtained in 537 genera and 115 families. The Mexican decapod fauna represents 11.9% of the world's total. The most species rich families are Alpheidae (7.4%) and Palaemonidae (5.5%), while a total of 23 families have only one known species in Mexico. Out of the total number of species, 1 597 (89.9%) are marine and 178 freshwater (10.1%); in turn, 46.7% of the marine species occur in the Pacific , 31.4% in the Gulf of Mexico and 21.8% in the Caribbean, with an important proportion of species occurring in more than one of these regions. Due to the fact that the marine decapod fauna of Mexico is, in general, shared with neighboring countries levels of endemism are low. In contrast, there is a very high level of endemism in the freshwater fauna, considering for example freshwater crabs and crayfishes. Based on projections proposed by other authors it is estimated that we now know only half of the species of decapods that occur in Mexico.

Se presenta una breve sinopsis sobre las características de los crustáceos decápodos y sobre las propuestas recientes de su clasificación. Sobre la base de una compilación exhaustiva de los registros de crustáceos decápodos en México, se estableció un listado de estas especies para las regiones continental, del Caribe, del golfo de México y del Pacífico mexicano. En total se contabilizaron 1 775 especies distribuidas en 537 géneros y 115 familias. Se estima que la fauna de decápodos de México representa el 11.9% del total mundial. Las familias con mayor riqueza son Alpheidae (7.4%) y Palaemonidae (5.5%), mientras que un total de 23 familias cuentan con una sola especie conocida en México. Del total, 1 597 especies (89.9%) son marinas y 178 dulceacuícolas (10.1%); de las especies marinas 46.7% se encuentran en el Pacífico, 31.4% en el golfo de México y 21.8% en el Caribe, habiendo un número importante que se distribuye en más de una de estas regiones. Debido al hecho de que la fauna marina de crustáceos decápodos de México es, en general, compartida con algunos otros países vecinos, el nivel de endemismo es relativamente bajo. Por el contrario, en el caso de la fauna de aguas dulces, se observa un nivel de endemismo muy alto; por ejemplo, en los cangrejos de agua dulce y acociles. Basados en proyecciones de otros autores se estima que se conocen actualmente sólo la mitad de las especies de crustáceos decápodos que hay en México.

In fulfillment of the International Code of Zoological Nomenclature recommendation 72F.4 (ICZN, 1999), an initial list of type material included in the Marine Invertebrates Regional Collection in the Unidad Academica Mazatlán, ICML, UNAM, in Mazatlán, Mexico, was published in 2003. A complementary list of all types that have been added since 2003 is presented. In addition, some type specimens not included in the 2003 list are also presented. This second list includes 52 lots of type material (15 of holotypes, 35 of paratypes and 2 of allotypes) totaling 82 specimens. The types correspond to species described from 1983 to 2012. In addition, a list of the 19 paratypes that have been deposited in other museums is also presented.

En cumplimiento con la recomendación 72F.4 del Código Internacional de Nomenclatura Zoológica (ICZN), se presenta una lista de los tipos resguardados en la Colección Regional de Invertebrados Marinos de la Unidad Académica Mazatlán, ICML, UNAM, en Mazatlán, México. La lista contiene 52 lotes de material tipo (15 holotipos, 35 paratipos y 2 alotipos) con un total de 82 ejemplares. Los tipos corresponden a especies descritas entre 1983 y 2012. Adicionalmente, se presenta una lista de los 19 paratipos depositados en otros museos.