Ingo S. Wehrtmann

Latitudinal variation in the reproductive biology of Betaeus truncatus (Decapoda: Alpheidae) along the Chilean coast

Abstract The extensive coast of Chile with its relatively homogeneous water masses favors a wide distribution of marine invertebrates, including the snapping shrimp Betaeus truncatus. We selected one sampling site in northern (Guanaqueros) and two sites in southern Chile (Metri and Putemün) to study latitudinal variation in the reproductive biology of B. truncatus. Monthly samples were collected over a one-year period (1994–95). The smallest ovigerous female was collected in northern Chile, but large-sized females with eggs were obtained principally in southern Chile. Females produced up to 1067 eggs per clutch (Guanaqueros), and average clutch size ranged from 234 (Putemún) to 399 eggs (Guanaqueros). The relationship between fecundity and female size differed significantly between Guanaqueros and the other two southern populations studied. Recently laid eggs in Metri and Putemún were significantly larger than those extruded in northern Chile, and egg volume increased during embryogenesis between 80.8% (Putem ú n) and 184.9% (Metri). Brood mortality was significantly higher in Metri (41.4%) compared to Guanaqueros (20.8%) and Putemün (19.1%). Eggs produced in northern Chile contained the highest percentage of water. Egg dry mass as well as reproductive output increased from north to south. We compare our data with those published for other decapod species, and discuss the observed latitudinal clines.

Lipid composition and utilization in developing eggs of two tropical marine caridean shrimps (Decapoda: Caridea: Alpheidae, Palaemonidae"

Abstract Changes in biomass and lipid biochemistry during egg development were studied in the tropical shrimps, Alpheus saxidomus and Palaemonetes schmitti , from Pacific Costa Rica. Freshly-laid eggs of P . schmitti were substantially smaller than those of A . saxidomus ; dry mass decreased during embryogenesis in the former species but remained almost constant in the latter one. Water content of eggs close to hatching were similar among both species (roughly 75%). Newly-produced eggs of the two species contained ≈20% fatty acids per egg dry mass; a comparison with data concerning decapods inhabiting tropical and temperate waters revealed that eggs produced by shrimps inhabiting tropical waters tend to have a higher lipid egg content per dry mass than those from temperate regions. Major lipid classes in the eggs of both species were phospholipids and triacylglycerols which increased and decreased during the incubation period, respectively. The predominant fatty acids of P . schmitti eggs were 16:0, 20:5(n-3) and 22:6(n-3) whereas eggs of A . saxidomus showed high amounts of 16:0, 20:5(n-3) and 16:1(n-7), and remarkably low values of 22:6(n-3) fatty acid. Lipid utilization was more pronounced in P . schmitti ; in A . saxidomus , eggs close to hatching still contained 70% of the initially deposited fatty acid content which may indicate an enhanced independence of the newly-hatched larvae on external energy resources. The observed differences may partially be related to different habitat preferences, however, the role of adaptation and phylogeny as determinants of egg lipid biochemistry in caridean shrimps remains to be clarified.

Egg production in Betaeus emarginatus (H. Milne Edwards, 1837) (Decapoda: Alpheidae): fecundily, reproductive output and chemical composition of eggs

Abstract The major variables concerning clutch size, reproductive output and chemical composition of developing eggs were analyzed in the snapping shrimp Betaeus emarginatus from central-southern Chile. Betaeus emarginatus produced numerous (x=285) and relatively large eggs (x =0.209 mm3, recently-produced embryos), which more than double (116.2%) in volume during embryogenesis. Egg loss was fairly low (11.6%). Water constituted the predominant component of the eggs and increased gradually from 56.5% to 76.1%. Brood masses comprised an average of 8.5% of the female body dry weight, and the reproductive output (RO) was 0.09 (based on dry weight). Due to the apparent lack of information regarding the reproductive biology of snapping shrimps from temperate waters, we compare our data with those of other Alpheidae from tropical and subtropical zones. Our results corroborate the tendency of decreasing RO with increasing latitude.

Interannual variations of lipids and fatty acids during larval development of Crangon spp. in the German Bight, North Sea

Abstract Eggs and larval stages of the caridean shrimps Crangon crangon and C. allmanni were collected to determine their lipid and fatty acid compositions. Specimens were sampled after the extremely mild winter of 1989/1990 and during the following year, 1991. The fatty acid composition of the zoeal stages of both C. crangon and C. allmanni from 1991 were predominated by the polyunsaturated fatty acids which are typical for marine organisms. In contrast, unsaturated fatty acids were absent in the early larval stages of C. crangon collected in 1990; however, advanced larval stages showed a similar fatty acid composition compared to larvae from 1991. The major phospholipid of eggs and larvae was phosphatidylethanolamine. Eggs contained also phosphatidylcholine and phosphatidylserine, which are probably utilized during embryonic development until hatching because in the early larval stages, only phosphatidylethanolamine was found. In stage VII, again phosphatidylcholine and phosphatidylserine occurred. The lipid and fatty acid composition seems to be an indicator for the survival chances of the planktonic stages. The absence of unsaturated fatty acids may be interpreted as a consequence of unfavorable nutritional conditions during the early developmental phase of the shrimps.

Interpopulation Comparison of Reproduction of the Atlantic Shrimp Hippolyte obliquimanus (Caridea: Hippolytidae)

Abstract The genus Hippolyte is represented by typically small shrimps with intriguing mechanisms of reproduction. In order to study possible variability in reproductive aspects among different populations, we conducted an exhaustive comparative study of H. obliquimanus from South (Brazil) and Central American (Costa Rica) waters. The study focuses on fecundity and reproductive output. Mean size of ovigerous females was significantly larger, and both mean reproductive output and mean fecundity were significantly higher in specimens from Costa Rica then in those collected in Brazil. Embryo volume was significantly smaller in the Costa Rican population, and in both populations embryos doubled their volume during embryogenesis. We discuss and compare our findings with the information available regarding H. obliquimanus and other hippolytid shrimp. The reproductive traits of both populations of H. obliquimanus show some important differences which may reflect adaptations to local environmental conditions, demonstrating a high plasticity of reproductive features of the species in Brazilian and Costa Rican waters.

Reproductive Biology of the Freshwater Shrimp Macrobrachium carcinus (L.) (Decapoda: Palaemonidae) from Costa Rica, Central America

Abstract Macrobrachium carcinus, one of the largest freshwater shrimp of the east coast of the Americas, is commercially fished in certain parts of the region. We present data concerning the reproductive biology of the species, and compare findings with those published for other species of Macrobrachium. Ovigerous females were collected monthly between March 2004 and April 2005 in the San Juan River, northern Costa Rica. Egg bearing females ranged in size from 120.1 to 190.1 mm total length. Fecundity increased with female size and, up to 242,437 eggs, can be considered as high compared to other species of Macrobrachium. Average egg volume increased gradually during embryogenesis from 0.065 to 0.088 mm3, representing an overall increase of 35.4%. Eggs can be considered as small, typical for Macrobrachium species depending on brackish water to complete larval development. Reproductive output of M. carcinus varied between 4.0% and 21.0%, and was independent of female size; these values are within the range reported for other species of Macrobrachium and other marine caridean shrimp.

Effects of temperature on the embryonic development and hatchling size of Betaeus emarginatus (Decapoda: Caridea: Alpheidae)

Betaeus emarginatus is an alpheid shrimp inhabiting rock pool environments characterized by strong fluctuations of ambient factors. Here we describe the embryonic development of B. emarginatus, and analyse the effects of three different temperatures (13, 15 and 20°C) on the duration of the incubation period, egg volume, and the size and morphology of newly hatched larvae. The sequence of embryonic development followed the general patterns described for decapods. Temperature affected the duration of the incubation period, which varied between 66.8 days (13°C) and 22.7 days (20°C). Independent of the thermal regime, eye pigment appeared after completing approximately 50% of the incubation time. Despite almost an identical initial egg volume in all three treatments, there was an inverse relation between temperature and final volume: eggs incubated at 13°C were substantially bigger (471.5 mm3) than those maintained at 15 (403.3 mm3) and 20°C (387.6 mm3). The size of the hatchlings increased significantly with decreasing incubation temperature. However, morphological variability of selected larval characters was generally higher at elevated temperatures. We compare the results obtained with those reported for other decapods inhabiting temperate waters, and discuss the question of why larvae of B. emarginatus incubated at higher temperatures hatch at a smaller size compared to those incubated at lower temperatures.

The deepwater fishery along the Pacific coast of Costa Rica, Central America

Las capturas globales de los recursos marinos pesqueros disminuyeron durante las ultimas decadas. Sin embargo, se ha observado una tendencia de aumento en la explotacion de los recursos de aguas profundas, los cuales son especialmente vulnerables a la extraccion. Esta tendencia ha sido notable tambien en la pesca a lo largo del Pacifico de Latino America. En Costa Rica, la mayoria de las actividades pesqueras comerciales se concentran en la costa del Pacifico. Las especies objetivo de la pesca de aguas profundas en Costa Rica son los dos pandalidos Heterocarpus affinis y H vicarius asi como Solenocera agassizii, siendo esta ultima la mas importante respecto a las capturas anuales. Se compila la informacion disponible sobre las tres especies objetivo de Costa Rica. Ademas, se describen las actividades de investigacion relacionadas con los recursos de aguas profundas en Costa Rica y se presentan los datos disponibles sobre la fauna acompanante y el descarte en esa pesqueria. Finalmente, se describe la situacion actual de la administracion y manejo de dichos recursos en Costa Rica. Se recomienda fortalecer la colaboracion entre las agencias gubernamentales, el sector pesquero, las organizaciones no-gubernamentales y el sector academico para evitar la sobre-explotacion sin control de estos valiosos recursos de aguas profundas del Pacifico de Costa Rica.

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.

Larvas y estadíos tempranos de desarrollo de crustáceos decápodos de Chile: descripciones publicadas

Las descripciones larvarias de decapodos son esenciales para la comprension de las estrategias de la historia de vida, relaciones stock-reclutamiento y ecologia planctonica. Para facilitar tales estudios, se entrega informacion concerniente a las descripciones publicadas de los estadios tempranos de los decapodos que habitan aguas marinas y continentales chilenas. La publicacion de los estudios morfologicos sobre larvas de decapodos comenzo en Chile en 1936, y el numero de publicaciones mostro un claro aumento entre 1967 y 1973. Hasta la fecha, se ha descrito el desarrollo larvario completo de un 13,4% de los decapodos chilenos. El conocimiento concerniente a los estadios larvarios de los camarones carideos es extremadamente pobre, si se compara con la informacion disponible para las especies de anomuros (16%) y braquiuros (15%) reportados para Chile. La ausencia de descripciones larvarias para algunas especies comercialmente importantes no solamente dificulta la comprension de la biologia de estos crustaceos, sino tambien complica el desarrollo de estrategias de manejo adecuado