RESUMEN Objetivo. Se analizó la proporción de sexos, hembras ovígeras, talla de primera madurez sexual y fecundidad del cangrejo roca Grapsus grapsus en islas Lobos, Venados y Pájaros (sureste del Golfo de California). Material y métodos. Los muestreos fueron mensuales entre marzo 2011 y febrero 2012, las colectas fueron nocturnas durante la bajamar, se obtuvieron en un cuadrante (25 m2) por isla 30 organismos al azar, se les determinó el AN (mm) y PT (g). Se estimó la proporción de sexos y talla de primera madurez sexual (AN50%), se analizaron en hembras grávidas, las fases embrionarias y la fecundidad (método gravimétrico). Resultados. La proporción de M:H fue 1:1.3. La talla media de primera madurez fue AN50% 34.9 mm. Es evidente la presencia de hembras ovígeras (71.3%) y todas las fases embrionarias, la fase rojo-naranja fue la mayor representada en 48%. La variación del diámetro del huevo fue 1.1 a 5 µm y el promedio de 3.05 µm. La fecundidad media fue 24339.3 cigotos. El máximo y mínimo peso de hembras ovígeras fue 69.9 y 15.2 g, respectivamente. Conclusiones. Con base a las características biológicas del recurso tales como la proporción de sexos, hembras ovígeras, talla de primera madurez sexual y fecundidad en la población de G. grapsus, representa un efecto favorable en su posterior administración y manejo de este recurso en esta zona.

ABSTRACT Objective. The sex ratio, proportion of ovigerous females, length at sexual maturity and fecundity of Grapsus grapsus crabs in the Lobos, Venados and Pajaros islands (southeastern Gulf of California) were analyzed. Materials and methods. Sampling was conducted monthly between March 2011 and February 2012, during the night at low tide. Thirty crabs were collected in a quadrant (25 m2) at each sampling site on each island. cw (mm) and w (g) were determined. The sex ratio and size at sexual maturity (cw50%) were estimated, and for ovigerous females, embryonic stages and fecundity (gravimetric method) were determined. Results. The sex ratio (M:F) was 1:1.3. The average size at sexual maturity (cw50%) was 34.9 mm. The majority of females were ovigerous (71.3%), and 48% of the embryos of ovigerous females were at the red-orange phase. Egg diameter ranged from 1.1 to 5 µm, with an average of 2.05 µm. The mean fecundity was 24339.3 eggs. The maximum and minimum weight of ovigerous females was 69.9 and 15.2 g. Conclusions. The studied characteristics of sex ratio, proportion of ovigerous females, length at sexual maturity and fecundity of G. grapsus, indicate the effective administration and management of this resource in this area.

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: There are abundant reports of symbiosis wherein crustaceans live inside or on mollusks; however, there are few published records of gastropods hosting decapods. This study examines the biological association between fifteen snails (124.86 ± 19.01) from the species Pacific crown conch Melongena patula and the porcelain crab Euceramus transversilineatus. Morphometric relationships of both invertebrates, as well as some sexual characteristics of the crab were conducted. These invertebrates were sampled in the Navachiste Lagoon, in the south eastern Gulf of California, Sinaloa, Mexico. It was found 86.6% of the snails housed at least a female or a male porcelain crab (17.82 ± 3.27 mm total body length) or a pair of them (heterosexual and same sex) with a sexual proportion of 2M:1F. There were no correlations between any of the crab and snail based on their analyzed morphometric relationships. For the crab males, the measurements of both chelae presented relationships with total body length, carapace length, and abdomen width however, no significant differences were observed between the mean width and chelae length of males, females or between sexes. Of the six females collected, four were gravid. Preliminary observations indicated that the porcelain crab E. transversilineatus is a commensal endosymbiont that coexist in short-term association with M. patula. Their population distribution suggests that E. transversilineatus are polygamous with a promiscuous mating pattern.

Resumen: Existen abundantes informes de simbiosis en los que los crustáceos viven dentro o encima de moluscos, sin embargo, hay pocos registros publicados de gasterópodos que alberguen decápodos. Se examinó la asociación biológica entre el caracol corona del Pacífico, Melongena patula, y el cangrejo porcelánido, Euceramus transversilineatus, describiendo las relaciones morfométricas de ambos invertebrados, así como algunas características sexuales del cangrejo. Se muestrearon 15 caracoles (124,86 ± 19,01 mm de altura de concha) en la laguna Navachiste, en el sureste del Golfo de California, Sinaloa, México. El 86,6% de ellos albergaba al menos un cangrejo de porcelana hembra o macho (17,82 ± 3,27 mm de longitud total del cuerpo) o un par (heterosexual y mismo sexo) con una proporción sexual de 2M:1H. No hubo correlaciones entre ninguna de las relaciones morfométricas analizadas entre el cangrejo y caracol. Para los cangrejos, las mediciones de ambas quelas presentaron relaciones con la longitud corporal total, longitud del caparazón y ancho del abdomen en los machos; sin embargo, no se observaron diferencias significativas entre el ancho medio y la longitud de quelas de machos, hembras o entre sexos. De las seis hembras recolectadas, cuatro eran grávidas. Las observaciones preliminares indican que el cangrejo porcelánido E. transversilineatus es un endosimbionte comensal que coexiste en asociación a corto plazo con M. patula. Su distribución poblacional sugiere que E. transversilineatus es polígamo con un patrón de apareamiento promiscuo.

ABSTRACT There have been no published studies of the genus Donax in the eastern tropical Pacific. This work describes the morphometric relationships, growth and mortality of the bean clam Donax punctatostriatus Hanley, 1843 in the sandy beach of Isla de la Piedra, south of Mazatlán Bay, Mexico. Direct collections by hand were performed during 20 monthly sample periods (November 2008 to June 2010) in the intertidal zone of the beach. A total of 2,324 clams of different sizes were removed from the sand, then measured and weighed in the laboratory. The length range of the shells was 2.78-25.64 mm (mean = 12.61 ± 4.04 mm). The length-weight relationship of the total sample indicated isometric growth (a = 0.0002 g; b = 3.0 g mm−1, R2 = 0.97); there was positive allometric growth in the recruits (<6.99 mm) (b = 3.4) and in juveniles (b = 3.2); in adults there was negative allometric growth (b = 2.6). Negative allometry of the length/width (log Wd = −0.239 + 0.922 log L) and height/width (log Wd = −0.054 + 0.900 log H) ratio of adults is consistent with a more compressed form of their shell, which assists rapid burying behavior in the sand. The maximum-recorded size of an empty shell (39 mm) was used to set the value of L∞ and to estimate K with the Shepherd (SLCA) method. The average growth rate during the life cycle was 0.43 mm yr−1. Values of L∞ between 29.16 and 34.22 mm were estimated with the Powell-Wetherall method using different class intervals. The mortality coefficient estimated with various methods was variable (0.84-1.15 yr−1). The growth of the clam is rapid and the mortality high, probably because of the characteristics of the habitat, in a subtropical region with high hydrodynamics and sediment transport.

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.

A new pinnotherid crab, Pinnixa hendrickxi n. sp., is described from Isla de la Piedra, Mazatlán, Sinaloa, Mexico. The new species can be distinguished from most species of Pinnixa of the Eastern Pacific because males have an abdomen narrowed medially and widened distally. However, due to this characteristic, P. hendrickxi resembles P. darwiniGarth, 1960, P. plectrophorosGlassell, 1935, P. transversalisMilne-Edwards & Lucas, 1842, and P. bahamondeiGarth, 1957 from the eastern Pacific and P. faxoniRathbun, 1918, from the western Atlantic. Pinnixa hendrickxi can easily be distinguished from P. plectrophoros and P. transversalis by the absence of spines on third and fourth legs. On the other hand, the new species can be separated from P. transversalis , P. bahamondei , and P. faxoni by the absence of dorsal ridges on the carapace. It can be distinguished from P. darwini by the fingers of the chelae (which, when closed, leave a gap in P. darwini , but close almost completely in the new species), the exopod of the third maxiliped with a non-segmented flagellum in the new species, and first pleopod with slender terminal process and without bulbous subterminal swelling in the new species.

Se describe a Pinnixa hendrickxi (P. hendrickxi) , una nueva especie de cangrejo pinotérido de Isla de la Piedra, Mazatlán, Sinaloa, México. La nueva especie puede distinguirse de la mayoría de las especies de Pinnixa del Pacífico oriental porque los machos poseen un abdomen angosto en su parte media y ensanchado distalmente. Por esta característica, P. hendrickxi tiene mayor similitud con P. darwiniGarth, 1960, P. plectrophorosGlassell, 1935, P. transversalisMilne-Edwards y Lucas, 1842 y P. bahamondeiGarth, 1957 del Pacífico oriental y con P. faxoniRathbun, 1918, del Atlántico occidental. Pinnixa hendrickxi puede distinguirse fácilmente de P. plectrophoros y P. transversalis por carecer de espinas en las patas 3 y 4, y se diferencia de P. transversalis , P. bahamondei y P. faxoni por no presentar crestas o hileras de gránulos en el dorso del caparazón. La nueva especie también puede distinguirse de P. darwini porque los dedos de las quelas no forman una abertura interna amplia, el flagelo del exopodito del tercer maxilípedo es más corto y simple en lugar de esbelto y bisegmentado y porque los machos tienen un primer pleópodo con la porción terminal más esbelta y no bulboso en la porción subterminal.

A total of 202 species (122 genera in 62 families) and 4 979 specimens of mollusks was collected in 24 bottom trawls on the continental shelf off the coast of Sinaloa, in the SE Gulf of California, Mexico. The trawls were made between 27 and 117 m depth during the SIPCO I, II and III cruises aboard the research vessel "El Puma" of the Universidad Nacional Autónoma de México in April and August 1981, and in January 1982. The material obtained belongs to five classes of mollusks: Pelecypoda, 55 species, Gastropoda, 140; Cephalopoda, 3; Polyplacophora, 3; Scaphopoda, 1 species. Some species (2 Bivalvia; 4 Gastropoda; 1 Cephalopoda) could not be identified but were recognized as distinct. The check list presented includes the material examined and the geographic distribution of all species. In addition, an illustration of each collected species is provided.

Un total de 202 especies (122 géneros entre 62 familias) y 4 979 ejemplares de moluscos se recolectó en 24 arrastres de fondo que se realizaron en la plataforma continental frente a las costas de Sinaloa, en el SE del golfo de California, México. Los arrastres se efectuaron entre 27 y 117 m de profundidad, durante las Campañas SIPCO I, II y III, a bordo del buque oceanográfico "El Puma", de la Universidad Nacional Autónoma de México, en abril y agosto de 1981 y en enero de 1982. El material obtenido se reparte entre las diversas clases de moluscos como sigue: Pelecypoda, 55 especies; Gastropoda, 140; Cephalopoda, 3; Polyplacophora, 3; Scaphopoda, 1 especie. Algunas especies no pudieron ser identificadas (2 Bivalvia; 4 Gastropoda; 1 Cephalopoda), pero se reconocieron como distintas a las demás. El listado presentado incluye la lista del material examinado, así como la distribución geográfica de cada especie. Además, se incluye una ilustración de cada una de las especies recolectadas.

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).

The 53 species and subspecies of stomatopods known to date for the eastern Pacific belong to 5 superfamilies, 11 families and 22 genera. Several species are known only from the original description, including only one or a few specimens. In these cases, the lack of voucher specimens to complete the study of other species and the absence of samples from throughout the range of each species, which will allow to have a general idea of their distribution along the Pacific, have made their study complicated. Consequently, correct identifications of specimens are not always achieved. An illustrated key to superfamilies, families, genera and species of all species recorded for the American Pacific is presented, with the objective of facilitating species identification to increase the amount of reliable information available on the group in the region.

Las 53 especies y subespecies de estomatópodos del Pacífico oriental conocidas hasta la fecha pertenecen a 5 superfamilias, 11 familias y 22 géneros. Varias de estas especies solamente se conocen a partir de un ejemplar o una pequeña serie de ejemplares que sirvieron para la descripción original. En estos casos, la falta de material adicional para completar el estudio de las especies, así como la ausencia de muestras procedentes de otras localidades que permitirían tener una visión global de la distribución del grupo a lo largo del Pacífico americano han complicado considerablemente su estudio; consecuentemente, no siempre se logran identificaciones correctas de las especies. Con la finalidad de facilitar su identificación y coadyuvar a incrementar su conocimiento en todos los aspectos posibles, se presenta una clave taxonómica ilustrada de las superfamilias, familias, géneros y especies de estomatópodos registrados en aguas del Pacífico americano.