Postsettlement growth of two estuarine crab species, Chasmagnathus granulata and Cyrtograpsus angulatus (Crustacea, Decapoda, Grapsidae): laboratory and field observations

The estuarine grapsid crabs Chasmagnathus granulata and Cyrtograpsus angulatus belong to the most typical and dominant inhabitants of brackish coastal lagoons in southeastern South America. In a combined laboratory and field investigation of juvenile growth, we measured the increase in body size in these species under controlled conditions as well as in field experiments (in Mar Chiquita lagoon, Argentina), seasonal changes in size frequency distribution of a natural population, and growth related changes in selected morphometric traits of male and female juveniles (relations between carapace width, carapace length, propodus height and length of the cheliped, and pleon width). At 24°C, Cy. angulatus grew faster than Ch. granulata; it reached the crab-9 instar (C9; 13 mm carapace width) after 92 days, while Ch. granulata required 107 days to reach the C8 instar (7.4 mm). At 12°C, growth ceased in both species. The pleon begins to show sexual differences in the C5 (Cy. angulatus) and C8 instar (Ch. granulata), respectively, while the chelae differentiate earlier in Ch. granulata than in Cy. angulatus (in C4 vs C6). In the field, growth was maximal in summer, and was generally faster than in laboratory cultures. However, there is great individual variability in size (about 25% even in the first crab instar) and in size increments at ecdysis, increasing throughout juvenile growth. Our data indicate that, in the field, small-scale and short-term variations in feeding conditions, temperature, and salinity account for an extremely high degree of variability in the absolute and relative rates of growth as well as in the time to sexual differentiation

Dipurena spongicola sp. n. (Hydrozoa, Corynidae), ein in Schwämmen lebender Hydroidpolyp aus dem Kattegat und der nördlichen Kieler Bucht

Der Polyp einer neuen Art der Gattung Dipurena wird ausführlich beschrieben. Für das zugehörige Medusenstadium wird eine vorläufige Beschreibung gegeben. D. spongicola ist die erste bekanntgewordene Hydrozoenart, die ihr gesamtes Polypenstadium im Innern eines Schwammes (Halichondria panicea PALLAS) vollendet und die erste Dipurena-Art, die im Kattegat und der nördlichen Kieler Bucht nachgewiesen wird. Die wesentlichsten Unterscheidungsmerkmale zu drei ähnlichen Arten werden diskutiert. Es werden erste Angaben zur Ökologie und Biologie des beschriebenen Hydroiden gemacht. A detailed description of the hydroid and a preliminary one of the medusa stage of a new Dipurena-species is given. Dijmrena spongicola is the first Hydrozoan known to spend its whole hydroid stage inside sponges (Halichondria panicea PALLAS). lt is the first species of the genus Dipurena recorded from the Kattegat and the northern Kiel Bay. The most important characters distinguishing it from three other species are discussed. Preliminary observations concerning the ecology and biology of the new species are reported

Cambios bioquímicos relacionados con el ciclo de muda y desarrollo en las larvas del cangrejo, Maja brachydactyla (Brachyura: Majidae).

Ontogenetic changes in dry weight, elemental composition (CHN), and digestive enzyme activities (total protease, amylase) were studied during the moulting cycle of all larval instars (zoea I-II, megalopa; ZI, ZII, M) of the spider crab Maja brachydactyla Balss, 1922 reared in the laboratory. A gradual but significant increase in biomass was observed throughout the zoeal instars, followed by steeper growth in the megalopa. Maximum values were reached in moult stage D2. Digestive enzyme activities also increased significantly throughout larval development. The ZI showed a continuous increase in total protease activity during its moult cycle, suggesting that newly hatched larvae have a gradually increasing need to take up proteins to provide amino acids, which are prime materials for growth and development, and possibly to use them as a metabolic energy source. The largest variations in digestive enzyme activites in relation to the moult cycle were observed in the megalopa instar. After an initial increase in postmoult, enzyme activities decreased to low levels similar to those measured in the zoeal instars at intermoult, followed by another increase to a maximum level in premoult. Metamorphosis involves great physiological and behavioural changes, which could explain the large variations in the megalopa moult cycle. We therefore suggest that the moult cycle stages should be taken into account when nutritional condition indices are used to estimate the physiological performance of decapod crustacean larvae.Se han estudiado los cambios ontogénicos en peso seco, composición elemental (CHN), y actividad enzimática (proteasas totales, amilasas) durante el ciclo de muda en todos los estadios larvarios (zoea I-II, megalopa; ZI, ZII, M) del centollo Maja brachydactyla Balss, 1922 cultivados en el laboratorio. Se ha observado un incremento gradual y significativo en la biomasa durante los estadios de zoea, seguido de un crecimiento brusco en la megalopa alcanzando valores máximos en el estado de muda D2. La actividad enzimática también aumentó significativamente durante el desarrollo larvario. Las ZI presentaron un continuo incremento de la actividad de las proteasas totales durante el ciclo de muda, sugiriendo que las larvas recién eclosionadas tienen una necesidad inmediata y creciente de utilizar las proteínas como fuente de aminoácidos para el crecimiento y el desarrollo, y posiblemente, como fuente de energía. Las mayores variaciones durante el ciclo de muda en las actividades enzimáticas digestivas se observaron en el estado de megalopa. Después de un incremento inicial en postmuda, las actividades enzimáticas decrecieron a valores bajos comparados con aquellos medidos en los estados de zoea en intermuda y, a continuación, se alcanzaron los niveles máximos en premuda. La metamorfosis implica cambios fisiológicos, los cuales podrían explicar las fuertes variaciones observadas en el ciclo de muda de la megalopa. De ahí que sugiramos que los estadios del ciclo de muda deberían tenerse en cuenta en determinados estadios larvarios cuando se usen índices de condición nutricional para estimar el estado fisiológico de las larvas de crustáceos decápodos

Developmental and moult cycle related biochemical changes in larvae of the spider crab, Maja brachydactyla (Brachyura: Majidae)

Ontogenetic changes in dry weight, elemental composition (CHN), and digestive enzyme activities (total protease, amylase) were studied during the moulting cycle of all larval instars (zoea I-II, megalopa; ZI, ZII, M) of the spider crab Maja brachydactyla Balss, 1922 reared in the laboratory. A gradual but significant increase in biomass was observed throughout the zoeal instars, followed by steeper growth in the megalopa. Maximum values were reached in moult stage D2. Digestive enzyme activities also increased significantly throughout larval development. The ZI showed a continuous increase in total protease activity during its moult cycle, suggesting that newly hatched larvae have a gradually increasing need to take up proteins to provide amino acids, which are prime materials for growth and development, and possibly to use them as a metabolic energy source. The largest variations in digestive enzyme activites in relation to the moult cycle were observed in the megalopa instar. After an initial increase in postmoult, enzyme activities decreased to low levels similar to those measured in the zoeal instars at intermoult, followed by another increase to a maximum level in premoult. Metamorphosis involves great physiological and behavioural changes, which could explain the large variations in the megalopa moult cycle. We therefore suggest that the moult cycle stages should be taken into account when nutritional condition indices are used to estimate the physiological performance of decapod crustacean larvae.Bench fees were funded by INIA (RTA2008- 00003-00-00 project) to GR. Financial support was provided by the Ministry of Science and Research to GG (post-doctoral fellowship; INIA). The authors would like to thank Glòria Macià and Sandra Molas for their support as hatchery and laboratory technicians at IRTA, Sant Carles de la Ràpita, and Julia Haafke at AWI, Helgoland, for the CHN analysesinfo:eu-repo/semantics/publishedVersio

Las centollas colonizan la Antartida

Es conocido que en Antartida no viven cangrejos. El hallazgo en los ultimo años de centolla podria estar anunciando la futura conquista de la Antartida por los cangrejos

Experimente über Substratpräferenzen von Capitella capitata (Fabricius)

Attraction of the polychaete Capitella capitata to different types of substrates has been investigated in the laboratory. Some observations on the reprcduction, development, and breeding behaviour, as well as on the reaction of the species to the factors sewage concentration, light, and current are reported