Julio H. Vinuesa

Effect of temperature and salinity on larval development of southern king crab (Lithodes antarcticus)

Larvae of Lithodes antarcticus Jacquinot were reared in October, 1981 from hatching to the glaucothoe stage at 16 temperature/salinity combinations (5.5°; 7.5°; 9.5° and 13.5°C; 26, 29, 32 and 35‰ S) to determine optimal environmental conditions for larval development. The highest survival percentage was obtained in the culture at 7.5°C and diminished according to temperature increase or decrease. High temperature cultures significantly shorten the larval life duration, but produce large mortalities. At 5.5°C mortality occurred almost exclusively during the moult to glaucothoe stage. Higher survival percentages were obtained as salinity was increased. In the lowest salinity culture (26‰ S) no zoea reached the post-larvae stage at culture temperatures. The best T/S combination was obtained at 7.5°C and 35‰ S, with a survival percentage of 29%. The shortest zoeal developments were obtained at 32‰ S in all culture temperatures. Salinity also affects larvae coloration: there is a pigment concentration on erythrophores, which causes a color decrease.

Distribución de crustáceos decápodos y estomatópodos del golfo San Jorge, Argentina

Resumen.- El golfo San Jorge es una amplia entrada de mar en el oceano Atlantico sudoccidental que se extiende entre los 45o y 47oS a los 64o40’W. Se desarrollan aqui pesquerias importantes como la de merluza comun, langostino, centolla, etc., siendo tambien zona de cria de estas y otras especies de interes comercial. El objetivo de este trabajo ha sido reconocer las especies de estos crustaceos que habitan el golfo y su distribucion en el mismo. Las muestras se han obtenido de los buques pesqueros costeros, fresqueros, de buques congeladores tangoneros y de muestreos en las costas, en intermareal y sublitoral, a partir de 1997. Se han registrado 27 especies de decapodos y 2 especies de estomatopodos en las aguas del golfo. Diez especies son tipicas de aguas templadocalidas (provincia argentina) y siete de ellas presentan el limite sur de su distribucion en el golfo. Dieciseis especies son anfioceanicas, tipicamente magallanicas y varias se distribuyen hasta las costas bonaerenses y aun Brasil. Se senala la presencia de Carcinus maenas, especie invasora con poblaciones recientemente instaladas en el area. Cinco especies ocupan el intermareal y submareal superior, asociados a sustratos duros y nueve especies se extienden en el submareal hasta los 30-40 m de profundidad, dependiendo de la existencia del sustrato apropiado. Otras ocho especies se extienden entre el submareal y las areas de mayor profundidad del golfo. Los animales se distribuyen principalmente de acuerdo a los tipos de fondo existentes. Palabras clave: Habitat, bentos, Crustacea, oceano Atlantico

REPRODUCTION OF MUNIDA GREGARIA (DECAPODA: GALATHEIDAE) IN SAN JORGE GULF, SOUTHWEST ATLANTIC OCEAN

Abstract Munida gregaria is a galatheid very abundant in coastal waters of southern South America playing an important role in the trophic webs of the subantarctic coastal ecosystem. Different reproductive aspects of this species were studied from samples obtained by coastal trawlers between September 1997 and December 2000, which allowed the analysis of a total of 10,868 crabs. The reproductive period started in June, and females with small clutches composed of non-fecundated eggs were found in many cases. The size of clutches increased during the reproductive period, and the simultaneous presence of eggs at different stages of development was observed in the same female. In part of the population, larval hatching started in September, after which females mated again. These embryos hatched between late November and mid-December. Females reached physiological maturity between 9 and 12 mm CL and males between 6 and 8 mm CL. Fecundity was initially low (less than 500 eggs/female), and clutches were completed during the reproductive season, until a maximum of 7545 eggs. During the reproductive season males migrate to shallow waters where they gather for mating.

Reproductive biology of the spider crab Leucippa pentagona (Decapoda: Epialtidae), in Bustamante Bay, Argentina

Sizes at maturity, breeding period, and fecundity of the spider crab Leucippa pentagona in Bustamante Bay, Argentina (45.11oS, 66.56oW) were analyzed. Specimens were collected monthly between May 2006 and February 2008. The size at morphometric maturity was determined based on relative changes in cheliped length for males and abdomen width for females. The presence of spermatophores in the male deferent ducts and of eggs in the female abdomens were the criteria used to determine physiological maturity. The temporal variation of the proportion of ovigerous females was analyzed. Oocyte sizes in ovigerous females were measured to evaluate the occurrence of multiple spawnings. In males, the sizes at morphometric and physiological maturity were 28.05 and 16.7 mm carapace length (CL), respectively. In females, the size at morphological maturity was 18.5 mm CL, whereas size at physiological maturity was 18.25 CL. Ovigerous females were found between June and February in both years. Ovigerous females were found to have oocytes with advanced vitellogenesis. Fecundity was similar in both years and varied between 645 and 7114 eggs. The extended breeding period and the presence of vitellogenic oocytes in ovigerous females suggest the occurrence of two or more spawnings per reproductive season. Finally, the distribution range of this species in the Atlantic Ocean was extended from 43.3° to 45.11°S.

Effects of lindane and acetone on the development of larvae of the Southern King Crab(lithodes antarcticus jaquinot)

Lithodes antarcticus (southern king crab) is a commercially important species. The present study attempts to describe the effects of an organochlorine pesticide and the most commonly used solvent (acetone) on the early development of this species. The aims of this study were: to determine the effects of lindane on survival, development and moulting during the early larval stages of L. antarcticus, and to determine an incipient lethal level, corresponding to a threshold concentration, at which acute toxicity ceases.

Infestation of Lithodes santolla (Decapoda: Lithodidae) by Pseudione tuberculata (Isopoda: Bopyridae) in San Jorge Gulf, Southwestern Atlantic Ocean.

Abstract The bopyrid isopod Pseudione tuberculata infests decapod crustacean species of the family Lithodidae. It has previously been found in Neolithodes diomedeae from Chile, in Lithodes santolla and Paralomis granulosa from the Beagle Channel and in L. santolla from the Magellan Strait. A case was detected in 1980 in San Jorge Gulf and since then no bopyrid has been found in any of the 12,300 specimens of Lithodes santolla studied from commercial captures. In the present study we collected and analysed 648 juveniles of Lithodes santolla measuring between 8.38 and 49.04 mm carapace length (CL) from shallow waters in the central area of San Jorge Gulf. Sixteen females of Pseudione tuberculata along with 12 attached males were recorded. Additionally, six exuviae showed branchial swelling but no parasites were found. An infestation of the right branchial chamber was observed only once. Ten bopyrid females were mature and six were immature. Prevalence was very low and closely related to the age and the habitat of young king crabs in open coastal waters. The infestation occurs during the first months following postlarval settlement, and the parasite reaches sexual maturity within the next year, before host juveniles leave the coastal waters. So, the entire life span of the bopyrid could occur in coastal waters.

Bycatch of the squat lobster Munida gregaria in bottom trawl fisheries in San Jorge Gulf, Argentina

Varias especies de langostillas son reconocidas como recursos pesqueros potenciales en todo el mundo. La langostilla Munida gregaria es un componente importante de las capturas incidentales en las pesquerias de arrastre en la Patagonia Argentina. Se evaluo la frecuencia de ocurrencia (FO), abundancia relativa (AR) y destino de las capturas incidentales de M. gregaria en: a) la flota congeladora tangonera (63579 lances), b) la flota fresquera de altura (5608) y c) la flota costera (584). Las mayores FO y AR fueron registradas en la flota costera. Sin embargo, dada la magnitud de la flota congeladora tangonera, el esfuerzo de pesca sugiere que las mayores capturas incidentales en terminos de biomasa son producidas por esta flota. Se observo un incremento significativo en FO y AR en los lances de la flota congeladora tangonera en los ultimos anos, siendo este mas marcado en aguas nacionales y provinciales de la provincia de Santa Cruz. La FO y AR de la especie en los lances de la flota fresquera de altura fueron bajas durante todo el periodo analizado. Los resultados confirman que la langostilla es una especie muy abundante y un recurso desaprovechado hasta el presente, y que puede representar una alternativa para la flota costera en el Golfo San Jorge.

La alimentación de Munida gregaria (Fabricius, 1793) (Crustacea: Anomura: Galatheidae) en fondos de pesca del Golfo San Jorge, Argentina

The area encompassing San Jorge gulf and surroundings is one of the most important fishing grounds in Argentina. Heavy fishing pressure affects the dynamics ...

Feeding strategy of early juvenile stages of the southern king crab Lithodes santolla in the San Jorge Gulf, Argentina

Resumen.- Se analizo el contenido estomacal de 313 ejemplares juveniles de centolla de ambos sexos con longitudes de caparazon (CL) entre 8,40 y 49,04 mm, estudiandose la influencia del sexo, talla, estado de muda y estacion del ano. Los animales fueron capturados mediante buceo en muestreos estacionales en el infralitoral rocoso del area central del Golfo San Jorge. Se determino la frecuencia de ocurrencia (FO) y abundancia relativa (AR) de las presas halladas, estado de replecion y peso del contenido estomacal. Se registro un 14,4% de animales con el estomago vacio, un 55,1% con replecion menor del 50% y un 30,5% mayor al 50%. Los juveniles no se alimentan antes de mudar, durante la muda ni en postmuda reciente. Se identificaron 27 grupos de presas diferentes, incluidas varias especies de algas, protistas e invertebrados. Las mayores FO fueron registradas en algas coralinaceas (45,1%), ofiuroideos (34,8%), equinoideos (25,1%), isopodos (21,7%), moluscos bivalvos (19,5%), poliquetos (16,9%) y briozoos (15%). En terminos de AR, los principales componentes de la dieta fueron ofiuroideos, isopodos y coralinaceas. La composicion de la dieta es diferente en animales menores de 15 mm CL de aquellos mayores a esa talla, debido a la mayor abundancia de isopodos y briozoos en este intervalo. La gran diversidad de presas registradas indica que los juveniles son esencialmente depredadores macrofagos y omnivoros, que aprovechan los complejos habitats infralitorales rocosos y biogenicos del area estudiada para su alimentacion y refugio durante los primeros anos de vida. Palabras clave: Dieta, depredacion, Lithodes santolla, juveniles, aguas costeras, omnivoria

Breeding and fecundity of the sub-Antarctic crab Halicarcinus planatus (Crustacea: Hymenosomatidae) in the Deseado River estuary, Argentina

Halicarcinus planatus is the only species of the genus occurring at the southern tip of South America, in sub-Antarctic, cold-temperate waters. Previously it has been shown that the population from the estuary of the Deseado River presents a spatial segregation by sex, a complete overlapping of sizes among adolescents and adult females. Females go through two reproductive seasons, separated by a resting period during late summer and early autumn, and 7 to 8 spawns are produced following a single mating. The aims of the present work were to evaluate the duration of the embryonic development until hatching during successive spawning, to determine the fecundity and to discuss the adaptive reproductive strategies of this population. Breeding occurs from nearly 2°C to above 16°C. The incubation period lasts nearly 100 days in winter and between 30 and 40 days in summer. The fecundity ranged from 210 to 2150 eggs, it differs between successive spawning and a positive relationship was found between fecundity and carapace width. This population has the highest fecundity compared to other populations, but also compared to other species of thegenus. The high number of successive spawns is directly linked to the increase of seawater temperature by the end of spring and during summer. This way, this species would be very well adapted to live in the more temperate waters of Patagonian coasts.