Ageing in the marine pelagic copepod Acartia tonsa results in decreased feeding and production rates associated with an increase in the accumulation of protein oxidative damage, as predicted by the oxidative stress hypothesis. In laboratory experiments, we estimated sex-specific ageing effects on feeding and oxidative damage and on egg production rates of adult females. We also determined maternal effects on offspring by measuring egg hatching success and oxidative damage of nauplii from mothers of different ages. Males manifested more oxidative damage with age than females, providing an alternative explanation for the shorter life span in males. Older females produced fewer offspring, and nauplii with higher protein oxidative damage, than younger females. This study forms an empirical basis to link ageing, life span, sex differences and maternal fitness in animals that also reflects natural copepod population dynamics. Individual ageing processes and the resulting age structure in the population modulate mortality risk, parental effects on offspring performance, reproductive investment, and pelagic energy fluxes.KEY WORDS: Ingestion rate · Fertility pattern · Maternal effect · Oxidative damage · Acartia tonsa Resale or republication not permitted without written consent of the publisher Acartia tonsa males (left) and females (right) change in appearance, physiology and behaviour as they age.

We performed a detailed analysis of the food web structure of Laguna de Rocha, a temporally open coastal lagoon in the Southwest Atlantic, characterised by spatial gradients in salinity, nutrient levels and trophic status. Carbon and nitrogen stable isotopes of main producers, invertebrate and vertebrate consumers, and stomach contents of ichthyofauna were analysed seasonally at freshwater (north) and marine-influenced (south) sites to determine whether environmental differences induced changes in food web structure. Contribution of primary and secondary food sources and trophic linkages were assessed with the multisource-partitioning model IsoSource and an index that quantifies the contribution of each organism as food for the ecosystem. Isotopic analyses were performed for 10 primary organic matter sources (OM), 13 invertebrates and 9 fish species. Suspended and sediment OM constituted the most important primary sources, while direct consumption of macrophytes and macroalgae was marginal. The small invertebrates Neomysis americana, Nephtys fluviatilis, Pseudodiaptomus richardii and an amphipod were the most important intermediate consumers at both sites (except P. richardii, which was present only in the north). Top predators were the fish species Micropogonias furnieri, Paralichthys orbygnianus and Hoplias malabaricus, and the maximum estimated trophic level (between 3.4 and 4.8) varied seasonally, but not between sites. Fish stomach content analyses largely confirmed results from the IsoSource mixing model. Overall results indicated that, despite environmental differences between sites, the structure of the biological assemblages and general trophic patterns were similar at both sites.KEY WORDS: Food web structure · Coastal lagoon · Estuaries · Benthic-pelagic coupling · Isotopic mixing models Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 362: [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] 2008 organic matter (OM) sources, energy pathways supporting consumers, and the processes modulating their spatial and temporal variability (Chanton & Lewis 2002, Froneman 2004. Most studies in shallow estuaries have focused on identifying OM sources that sustain specific consumer groups. Traditional views of macrophyte detritus as a fuel for secondary production (Odum & Heald 1975) have received only partial support (Deegan & Garrit 1997, Kwak & Zedler 1997, Chanton & Lewis 2002, Kibirige et al. 2002, Perissinotto et al. 2003, Vizzini & Mazzola 2003, Bouillon et al. 2004. Microphytobenthic algae, phytoplankton, macrophytes and detritus can all be important sources, and relative contributions differ between systems according to environmental characteristics (Kanaya et al. 2007).Less effort has been devoted to identifying the most significant secondary-level food sources (i.e. heterotrophic OM sources for secondary and higher consumers). The structure of the assemblage of intermediate consumers that link basal OM sources and higher predators can be...

The feeding of 2 sympatric larval myctophids, Diogenichthys laternatus and Triphoturus mexicanus aff. oculeus, was analyzed in an upwelling area off northern Chile (23°S, 71°W). Diel feeding period, feeding incidence, feeding selectivity and diet overlap was estimated under different environmental conditions: coastal and oceanic areas and 2 depth strata in summer and winter 1997. Analyses were based on larval stomach contents and microplankton abundance estimates. Larval tooth morphology and relationships between larval length, mouth width and prey size were explored. Both species fed on the most abundant microplankton layer during daylight, and both preferred copepods and nauplii, although the diet of D. laternatus was more diverse. As expected, the diets of these species tended to overlap in periods and areas where food was more abundant, but diets differed under conditions of low food availability. The 50 to 100 mm size range dominated the size spectrum of ingested prey in both species. The smallest prey width was constant for the entire range of larval sizes. The largest prey width was variable both within and between species, and increased with larval size. Regression analyses of mouth size and body length showed a potential relationship in D. laternatus and a linear relationship in T. mexicanus aff. oculeus. Prey ingested by D. laternatus were wider than those ingested by T. mexicanus aff. oculeus at equal larval sizes. The species presented differences in dentition patterns (hook-like teeth and pharyngeal structures in D. laternatus, conical teeth in T. mexicanus aff. oculeus). Opportunistic feeding and the feeding characteristics of both species should favor persistence and high abundances in the upwelling area of the Humboldt Current. KEY WORDS: Diogenichthys laternatus · Triphoturus mexicanus · Triphoturus oculeus · Larval feeding · Myctophid · Upwelling · Humboldt CurrentResale or republication not permitted without written consent of the publisher

This study compares the effect of temperature on the post-embryonic development time and weight-specific growth rate in 2 populations of Acartia clausi from different biogeographic areas (northern and southern Europe). Development was followed from nauplius I to adult at 3 temperatures (10, 15 and 18°C) at saturating food conditions. The relationship between development time and temperature was established by fitting Belehradek's function. The northern population had a shorter generation time at all temperatures. At 10°C, the development time was estimated to be 33.9 and 36.4 d decreasing to 16.3 and 17.4 d at 18°C for the northern and southern populations, respectively. Prosome length decreased with temperature, and the southern population had longer individuals at all temperatures. ANCOVA revealed a significant (p < 0.001) positive effect of temperature on the growth rates, and nauplii grew faster than copepodites (except at 18°C in the southern population and 20°C in the northern population). Significant differences between populations were noted during larval growth, with nauplii from the north growing faster at high temperatures (18°C). The results indicate that the 2 A. clausi allopatric populations subjected to different temperature regimes have different temperature responses, in particular at high temperatures.KEY WORDS: Temperature · Development time · Weight-specific growth rate · Acartia clausi · Ria de Aveiro (Portugal) · Gullmarsfjord (Sweden)Resale or republication not permitted without written consent of the publisher

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Divergence between two eastern Pacific forms of Triphoturus, currently considered to belong to the same species was tested by DNA sequences of the cytochrome b gene (DNA obtained from larvae collected in northern Chile and from adults in the Southern California Bight) and examination of larval characters. The number of apparently fixed substitutions (12 among 31 variable sites, out of 1001 bases) was high and the pattern of mid-lateral trunk pigmentation in larvae also differed consistently between the two forms. The results support the separate species status for T. mexicanus