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

Changes in volume, biomass, and fatty acids of developing eggs in Nauticaris magellanica (Decapoda : Caridea): A latitudinal comparison

The hippolytid shrimp Nauticaris magellanica, with a known geographical distribution covering approximately 35 degrees of latitude, was selected to conduct a latitudinal comparison regarding volume, biomass, and fatty acid changes during embryogenesis. Ovigerous females were collected from populations in northern (Guanaqueros) and central-southern Chile (Metri and Putemun). Recently produced eggs from the 3 populations sampled wen: similar in size (ranging from 0.031-0.038 min(3)). Embryos close to hatching, however, were considerably larger in central-southern Chile (Metri: 0.072 mm(3); Putemun: 0.091 mm(3)) compared with those from Guanaqueros (0.054 mml). Egg volume increase during the incubation period varied between 74% (Guanaqueros) and 160% (Putemun). Wet mass and water content of embryos increased, while dry and ash mass decreased during embryogenesis. Analyses of fatty acids revealed similar results for eggs from the 3 study sites and different developmental stages. The overall utilization of fatty acids, however, was elevated in embryos from the most southern location (Putemun) compared with that found in embryos from the other sampling sites. Main fatty acids of eggs and newly hatched larvae were the polyunsaturates 20:5 (n-3) and 22:6 (n-3), and the saturate 16:0, comprising 21, 16, and 15%, respectively, of the total. The pattern of fatty acid utilization during embryogenesis is characterized by a sharp decline of the 16:1 (n-7) fatty acid. Our results confirm a latitudinal dine in egg volume in N. magellanica. The differences observed among populations may be attributed, however, to differences in the ambient conditions (e.g., temperature, salinity, feeding) of the habitats rather than simply to its northern and southern location. In addition, the lipid biochemistry of developing eggs seems to be unaffected by latitude

The implications of temperature-mediated plasticity in larval instar number for development within a marine invertebrate, the shrimp Palaemonetes varians

Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30°C to assess their thermal scope for development. Larvae developed at 17, 25, and 30°C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as ‘repeat’ instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25°C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20°C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of importance for life-history ecology in response to environmental change, as well as for aquaculture applications

Reproductive features of the deep water hermit crab Sympagurus dimorphus

Figure 2. Sympagurus dimorphus. Relationship of the size (larger diameters) of gonopores by sexes and the shield length.Published as part of Schejter, L., Scelzo, M. A. & Mantelatto, F. L., 2017, Reproductive features of the deep water hermit crab Sympagurus dimorphus (Anomura: Parapaguridae) inhabiting pseudoshells in the SW Atlantic Ocean, pp. 2779-2792 in Journal of Natural History 51 (47-48) on page 2783, DOI: 10.1080/00222933.2017.1395094, http://zenodo.org/record/518397

Seasonal variations in larval biomass and biochemical composition of brown shrimp, Crangon crangon (Decapoda, Caridea), at hatching

The “brown shrimp”, Crangon crangon (Linnaeus 1758), is a benthic key species in the North Sea ecosystem, supporting an intense commercial fishery. Its reproductive pattern is characterized by a continuous spawning season from mid-winter to early autumn. During this extended period, C. crangon shows significant seasonal variations in egg size and embryonic biomass, which may influence larval quality at hatching. In the present study, we quantified seasonal changes in dry weight (W) and chemical composition (CHN, protein and lipid) of newly hatched larvae of C. crangon. Our data revealed significant variations, with maximum biomass values at the beginning of the hatching season (February–March), a decrease throughout spring (April–May) and a minimum in summer (June–September). While all absolute values of biomass and biochemical constituents per larva showed highly significant differences between months (P < 0.001), CHN, protein and lipid concentrations (expressed as percentage values of dry weight) showed only marginally significant differences (P < 0.05). According to generalized additive models (GAM), key variables of embryonic development exerted significant effects on larval condition at hatching: The larval carbon content (C) was positively correlated with embryonic carbon content shortly after egg-laying (r 2 = 0.60; P < 0.001) and negatively with the average incubation temperature during the period of embryonic development (r 2 = 0.35; P < 0.001). Additionally, water temperature (r 2 = 0.57; P < 0.001) and food availability (phytoplankton C; r 2 = 0.39; P < 0.001) at the time of hatching were negatively correlated with larval C content at hatching. In conclusion, “winter larvae” hatching from larger “winter eggs” showed higher initial values of biomass compared to “summer larvae” originating from smaller “summer eggs”. This indicates carry-over effects persisting from the embryonic to the larval phase. Since “winter larvae” are more likely exposed to poor nutritional conditions, intraspecific variability in larval biomass at hatching is interpreted as part of an adaptive reproductive strategy compensating for strong seasonality in plankton production and transitory periods of larval food limitation