Desarrollo larvario de Pilumnoides hassleri (Decapoda: Brachyura: Pilumnoididae) cultivado en laboratorio, con una revisión de la sistematica de Pilumnoididae utilizando caracteres larvarios

The genus Pilumnoides is an interesting taxon because its systematic position, based on adult characters, remains unclear. These xanthoid crabs have been related to the Carpiliidae, Goneplacidae and Eriphioidea. P. hassleri A. Milne Edwards, 1880 lives in Brazilian, Uruguayan and Argentinian coasts as far south as the Magellan Strait (southwestern Atlantic). Larvae of P. hassleri from females collected in the harbour of Mar del Plata were reared in the laboratory from zoea I to megalopa and the first larval stage, and described. The species passed through 5 zoeal stages and a megalopa. Larval characters were compared with the previous description of larvae from the southeastern Pacific species P. perlatus and with species of Carpilius, Goneplax and Eriphia in order to review the relationships between these taxa.El género Pilumnoides es un taxón interesante dado que su posición sistemática, basada en caracteres adultos, permanece poco clara. Estos cangrejos xantoideos han sido relacionados con las familias Carpiliidae, Goneplacidae y Eriphioidea. P. hassleri A. Milne Edwards, 1880 vive en las costas de Brasil, Uruguay y Argentina hasta el Estrecho de Magallanes (Atlántico Sudoccidental). Se cultivaron larvas de P. hassleri, provenientes de hembras colectadas en el puerto de Mar del Plata, desde la zoea Ihasta la megalopa y el primer estadio de cangrejo, y posteriormente se describieron. La especie pasa por 5 estadios de zoea y una megalopa. Las características larvarias se compararon con descripciones previas de larvas de P. perlatus del Pacífico Suroriental, y con especies de Carpilius, Goneplax y Eriphia con el objetivo de rever las relaciones entre estos taxa

Diferencias interpoblacionales en el ciclo reproductivo femenino del cangrejo estuárico Chasmagnathus granulatus Dana, 1851 (Brachyura: Grapsoidea: Varunidae) del Atlántico sudoccidental

The female reproductive biology of Chasmagnathus granulatus Dana, a semiterrestrial burrowing crab endemic to the southwestern Atlantic, was compared in two contrasting coastal habitats: San Antonio (SA, marine) and Mar Chiquita (MC, estuarial). Mature females were collected monthly for 1.5 years and the ovarian cycle was described using a qualitative scale. Gonadosomatic (GSI) and hepatosomatic (HSI) indexes were calculated. The highest GSI and HSI occurred early in the reproductive season in SA and during the non-reproductive season in MC. The beginning and duration of the reproductive season also differed between populations: it started later and was shorter in SA. In MC, secondary vitellogenesis continued when the reproductive season had finished, and the ovaries remained fully developed throughout the non-reproductive season (winter). Therefore, females of MC were ready to lay eggs as soon as spring environmental conditions appeared. However, SA females did not attain a fully developed ovary during winter. A limited food supply would restrict the available energy to complete secondary vitellogenesis at the end of the reproductive season in SA, after the last spawning. Thus, the vitellogenic cycle should be completed in the following spring, causing a delay in the beginning of the reproductive period. In addition, the higher temperature amplitude may cause the reproductive period in SA to end early.La biología reproductiva de las hembras de Chasmagnathus granulatus Dana, un cangrejo semiterrestre y excavador endémico del Atlántico Sudoccidental, fue comparada entre dos localidades costeras con regímenes ambientales contrastantes: San Antonio (SA, marino) y Mar Chiquita (MC, estuarial). Hembras maduras fueron recolectadas mensualmente por 1.5 años y el ciclo ovárico fue descrito usando una escala cualitativa. Los índices gonadosomático (GSI) y hepatosomático (HSI) fueron calculados. Los mayores valores de GSI y HSI tuvieron lugar al inicio de la estación reproductiva en SA, y durante la estación no reproductiva en MC. El inicio y duración de la estación reproductiva también difirieron entre las poblaciones: ésta comenzó más tarde y fue más corta en SA. En MC, la vitelogénesis secundaria continuó cuando la estación reproductiva había finalizado, y el ovario permaneció desarrollado durante la estación no reproductiva (invierno). En consecuencia, las hembras de MC estaban listas para poner sus huevos tan pronto como aparecieron las condiciones ambientales de primavera. Por el contrario, las hembras de SA no alcanzaron un completo desarrollo del ovario durante el invierno. Un suministro limitado de alimento restringiría la energía disponible para completar la vitelogénesis secundaria al final de la estación reproductiva en SA, después de la última puesta. De ese modo, el ciclo vitelogénico debió completarse en la primavera siguiente, provocando un retraso en el comienzo de la estación reproductiva. Adicionalmente, la mayor amplitud térmica provocaría que la estación reproductiva finalice más temprano en SA

Desarrollo postembrionario de Pyromaia tuberculata (Lockington, 1877): Revisión de la morfología larval y postlarval

The spider crab Pyromaia tuberculata (Lockington, 1877) (Decapoda, Majidae) has been recorded from eastern Pacific coasts (México to Colombia), the western Pacific (Japan and New Zealand) and the western Atlantic (southern Brazil, near Rio de la Plata estuary and Argentine). Larvae of P. tuberculata from one female collected on beds of oysters and mussels at 50 m depth on the Argentine continental shelf (38°21´S; 57°38´W) hatched in the laboratory and were successfully reared until the first crab stage. This paper redescribes the zoea and megalopa phases and describes the juvenil crab morphology.El cangrejo araña Pyromaia tuberculata (Lockington, 1877) (Decapoda, Majidae) ha sido reportado en la costa este del Pacífico (desde México hasta Colombia), costa oeste del Pacífico (Japón y Nueva Zelanda) y en la costa oeste del Atlántico (sur de Brasil, cerca del Río de la Plata y Argentina). Larvas de P. tuberculata provenientes de una hembra colectada en un banco de ostras y mejillones a 50 metros de profundidad en la plataforma Argentina (38°21’S; 57°38’W) y que eclosionó en laboratorio, fueron cultivadas con éxito hasta el primer estadio de cangrejo. Este trabajo redescribe la morfología de las fases de zoea y de megalopa y describe la morfología del primer estadío de cangrejo

Great unexpected differences between two populations of the intertidal crab Neohelice granulata inhabiting close but contrasting habitats (Crustacea: Decapoda: Brachyura)

ABSTRACT Two populations of the Southwestern Atlantic burrowing crab, Neohelice granulata (Dana, 1851), are separated by only 190 km. They inhabit bays that drain into a Patagonian gulf in the southernmost limit of the geographical distribution of the species: San Antonio Bay (SAO) and San José Gulf (RSJ). The population from SAO has been extensively studied, whereas that of RSJ has not. The main goal of this study is to compare the ecological and habitat characteristics of the two populations, based on samples collected on successive days during the middle of the reproductive season of the crab. The substrate of SAO is composed of a high proportion of gravel and scarce organic matter, whereas the substrate of RSJ presents twice as much silt and clay, and greater organic matter content. Crabs of both sexes were larger at RSJ. Fecundity and reproductive output were greater at RSJ. The size of females at maturity was smaller and their range was shorter at RSJ. Burrows were longer and wider at RSJ. Our results indicate that there are strong differences between the two populations, which might be correlated with local environmental differences, mainly substrate granulometry and food availability

Ciclo reproductivo de hembras del Cangrejo estuarial del Atlántico sudoccidental Chasmagnathus granulata (Brachyura: Grapsoidea: Varunidae)

The female reproductive biology of a Chasmagnathus granulatus population inhabiting the area near the mouth of Mar Chiquita coastal lagoon, Argentina, was studied. An increase in air temperature during the spring is related to the start of the breeding period, when well defined egg-laying and hatching pulses were observed. Hatching is synchronic during the whole summer but the egg production was not, probably due to the gradual incorporation of young females to the reproductive population. Neither egg-laying nor larval release showed a clear relation to moon phase or tidal cycles, suggesting that reproduction is not rigidly programmed in this unpredictable habitat. Females moult at the beginning of autumn, after releasing the last larvae. However, a new cohort of ovocytes, which was in primary vitellogenesis before moulting, completed the secondary ovogenesis after moulting. Consequently, ovaries remained fully developed throughout the winter.Fue estudiada la biología reproductiva de hembras de una población de Chasmagnathus granulatus en la boca de la laguna Mar Chiquita, Argentina. El incremento de la temperatura del aire en la primavera está relacionado con el inicio del periodo de cría, momento en el cual se observan pulsos de extrusión de huevos y eclosión de larvas bien definidos. La eclosión de larvas es sincrónica durante todo el verano, pero no así la producción de huevos, probablemente debido a la gradual incorporación de hembras jóvenes a la población reproductiva. Ni la extrusión de huevos ni la eclosión de larvas muestran una clara relación con las fases de la luna o los ciclos de marea, sugiriendo que la reproducción no está sujeta a un programa inflexible en un hábitat impredecible. Las hembras mudan a principios del otoño, después de las últimas eclosiones larvales. Sin embargo, una nueva cohorte de ovocitos, que estaban en vitelogénesis primaria antes de la muda, completan la vitelogénesis secundaria después de mudar. Consecuentemente, los ovarios están completamente desarrollados durante todo el invierno

Great unexpected differences between two populations of the intertidal crab Neohelice granulata inhabiting close but contrasting habitats (Crustacea: Decapoda: Brachyura)

ABSTRACT Two populations of the Southwestern Atlantic burrowing crab, Neohelice granulata (Dana, 1851), are separated by only 190 km. They inhabit bays that drain into a Patagonian gulf in the southernmost limit of the geographical distribution of the species: San Antonio Bay (SAO) and San José Gulf (RSJ). The population from SAO has been extensively studied, whereas that of RSJ has not. The main goal of this study is to compare the ecological and habitat characteristics of the two populations, based on samples collected on successive days during the middle of the reproductive season of the crab. The substrate of SAO is composed of a high proportion of gravel and scarce organic matter, whereas the substrate of RSJ presents twice as much silt and clay, and greater organic matter content. Crabs of both sexes were larger at RSJ. Fecundity and reproductive output were greater at RSJ. The size of females at maturity was smaller and their range was shorter at RSJ. Burrows were longer and wider at RSJ. Our results indicate that there are strong differences between the two populations, which might be correlated with local environmental differences, mainly substrate granulometry and food availability