Environmental stress and parasitism as drivers of population dynamics of Mesodesma donacium at its northern biogeographic range

Abstract Riascos, J. M., Heilmayer, O., Oliva, M. E., and Laudien, J. 2011. Environmental stress and parasitism as drivers of population dynamics of Mesodesma donacium at its northern biogeographic range. – ICES Journal of Marine Science, 68: 823–833. Mesodesma donacium is a commercially important bivalve in Chile and Peru. During strong El Niño events, populations at the northern end of its geographic distribution are wiped out, so to understand its threshold responses to biotic and abiotic factors, the population dynamics of one of the northernmost population remnants was analysed between 2005 and 2007. Strong interannual differences were found in abundance, body mass, growth rate, somatic production, and the prevalence of the parasite Polydora bioccipitalis. A Spearman rank correlation analysis showed that changes in beach slope, seemingly linked to repeated storm surges, negatively affected the clam's abundance and seemingly also affected growth, mortality, body mass somatic production, and parasite prevalence. Infestation by P. bioccipitalis was restricted to adult clams. Juvenile clams suffered high mortality because they inhabit the intertidal zone, where wave action is strong. Larger clams also showed high mortality, which seemed best explained by a synergistic effect of parasite load and environmental stress. This parasite-climate-driven mortality of larger clams had a strong impact on somatic production and implied a dramatic loss of fecundity (82%), which may significantly affect the ability of the species to recover its former abundance and distribution.</jats:p

Physiological capacity of Cancer setosus larvae — Adaptation to El Niño Southern Oscillation conditions

Temperature changes during ENSO challenge the fauna of the Pacific South American coast. In many ectotherm benthic species pelagic larvae are the most important dispersal stage, which may, however, be particularly vulnerable to such environmental stress. Thermal limitation in aquatic ecotherms is hypothesized to be reflected first in the aerobic scope of an animal. Here we present results on whole animal oxygen consumption and on the activities of two metabolic key enzymes, citrate synthase (CS) and pyruvate kinase (PK)) of Cancer setosus zoeal larvae, acclimated to different temperatures. Larvae acclimated to cooler temperatures (12 and 16 °C) were able to compensate for the temperature effect as reflected in elevated mass specific respiration rates (MSR) and enzyme activities. In contrast, warm acclimated larvae (20 and 22 °C) seem to have reached their upper thermal limits, which is reflected in MSR decoupling from temperature and low Q10 values (Zoea I: 1.4; Zoea III: 1.02). Thermal deactivation of CS in vitro occurred close to habitat temperature (between 20 and 24 °C), indicating instability of the enzyme close to in vivo thermal limits. The capacity of anaerobic metabolism, reflected by PK, was not influenced by temperature, but increased with instar, reflecting behavioral changes in larval life style. Functioning of the metabolic key enzyme CS was identified to be one possible key for larval limitation in temperature tolerance

Metabolic rate and growth in the temperate bivalve Mercenaria mercenaria at a biogeographic limit, from the English Channel

Metabolism and growth rate of the hard clam, Mercenaria mercenaria, were investigated in a population invasive to Southampton Water, southern England. An individual metabolic model expressed as a function of soft tissue dry mass was fitted to data of 18 individuals (log (VO2) = −1.952 + 0.543 • log (DM); F1,16 = 201.18, P &lt; 0.001, r2 = 0.926). A von Bertalanffy growth function was fitted to 227 size-at-age data pairs of 18 individuals (Ht = 80.13 • (1 − e−0.149 • (t−0.542)); r2 = 0.927). Individual age-specific somatic production was calculated, demonstrating increase with age to a maximum of 3.88 kJ y−1 at ten years old followed by decrease, and individual age-specific annual respiration was calculated, demonstrating asymptotic increase with age to 231.37 kJ y−1 at 30 years old. Results found here lie within the physiological tolerances reported across the biogeographical range, suggesting that the species' biogeographical limitation in the UK to Southampton Water results from ecological rather than physiological factors

Temperature effects on zoeal morphometric traits and intraspecific variability in the hairy crab Cancer setosus across latitude

International audiencePhenotypic plasticity is an important but often ignored ability that enables organisms, within species-specific physiological limits, to respond to gradual or sudden extrinsic changes in their environment. In the marine realm, the early ontogeny of decapod crustaceans is among the best known examples to demonstrate a temperature-dependent phenotypic response. Here, we present morphometric results of larvae of the hairy crab , the embryonic development of which took place at different temperatures at two different sites (Antofagasta, 23°45′ S; Puerto Montt, 41°44′ S) along the Chilean Coast. Zoea I larvae from Puerto Montt were significantly larger than those from Antofagasta, when considering embryonic development at the same temperature. Larvae from Puerto Montt reared at 12 and 16°C did not differ morphometrically, but sizes of larvae from Antofagasta kept at 16 and 20°C did, being larger at the colder temperature. Zoea II larvae reared in Antofagasta at three temperatures (16, 20, and 24°C) showed the same pattern, with larger larvae at colder temperatures. Furthermore, larvae reared at 24°C, showed deformations, suggesting that 24°C, which coincides with temperatures found during strong EL Niño events, is indicative of the upper larval thermal tolerance limit.   is exposed to a wide temperature range across its distribution range of about 40° of latitude. Phenotypic plasticity in larval offspring does furthermore enable this species to locally respond to the inter-decadal warming induced by El Niño. Morphological plasticity in this species does support previously reported energetic trade-offs with temperature throughout early ontogeny of this species, indicating that plasticity may be a key to a species' success to occupy a wide distribution range and/or to thrive under highly variable habitat conditions

Environment, adaptation and evolution: Scallop ecology across the latitudinal gradient

Marine biota show latitudinal gradients in distribution, composition and diversity. Most studies of latitudinal gradients in organism biology and ecology are based on between-species comparisons and hence are hampered by taxon-related variability in the parameters under investigation. To reduce taxonomic noise and to minimize the risk of otherwise misleading generalisations I used species from one single bivalve family (Pectinidae, scallops.Ecological (e.g. age, growth, productivity) and physiological (standard metabolic rate, enzyme kinetics) parameters of three scallop species (Adamussium colbecki, Aequipecten opercularis and Zygochlamys patagonica) were measured and combined with data extracted from literature. The resulting database comprised 226 studies of 26 species living over a temperature range of 28°C. The overall growth performance of scallops increases with decreasing latitude, i.e. it is strongly coupled to annual solar energy input but weakly coupled to average annual water temperature. Mean annual water temperatures and annual solar energy input by themselves can explain only a small part of the variability observed in growth performance. An analysis of 82 published studies on standard metabolism provided no evidence for metabolic cold adaptation at the organism level. In contrast, mitochondrial proliferation caused a rise in oxygen demand in the Antarctic scallop indicating that metabolic cold adaptation does occur on the cellular level. It must be assumed that energy savings occur to counterbalance the cost of cellular MCA. At which organisational level such savings may occur remains unanswered so far.The present study indicates that many scallop species have developed strong life-history adaptations to the particular conditions of both alimentation and temperature they experience. In addition, the established pectinid database (ScallopBASE) provides a good basis for the evaluation of evolutionary adaptations and constraints

Umwelt, Anpassung und Evolution: Ökologie der Jakobsmuscheln im latitudinalen Gradienten

Marine biota show latitudinal gradients in distribution, composition and diversity. Most studies of latitudinal gradients in organism biology and ecology are based on between-species comparisons and hence are hampered by taxon-related variability in the parameters under investigation. To reduce taxonomic noise and to minimize the risk of otherwise misleading generalisations I used species from one single bivalve family (Pectinidae, scallops.Ecological (e.g. age, growth, productivity) and physiological (standard metabolic rate, enzyme kinetics) parameters of three scallop species (Adamussium colbecki, Aequipecten opercularis and Zygochlamys patagonica) were measured and combined with data extracted from literature. The resulting database comprised 226 studies of 26 species living over a temperature range of 28°C. The overall growth performance of scallops increases with decreasing latitude, i.e. it is strongly coupled to annual solar energy input but weakly coupled to average annual water temperature. Mean annual water temperatures and annual solar energy input by themselves can explain only a small part of the variability observed in growth performance. An analysis of 82 published studies on standard metabolism provided no evidence for metabolic cold adaptation at the organism level. In contrast, mitochondrial proliferation caused a rise in oxygen demand in the Antarctic scallop indicating that metabolic cold adaptation does occur on the cellular level. It must be assumed that energy savings occur to counterbalance the cost of cellular MCA. At which organisational level such savings may occur remains unanswered so far.The present study indicates that many scallop species have developed strong life-history adaptations to the particular conditions of both alimentation and temperature they experience. In addition, the established pectinid database (ScallopBASE) provides a good basis for the evaluation of evolutionary adaptations and constraints