Palaemonetes Varians Research Articles

Acute combined pressure and temperature exposures on a shallow-water crustacean: Novel insights into the stress response and high pressure neurological syndrome

Little is known about the ecological and physiological processes governing depth distribution limits in species. Temperature and hydrostatic pressure are considered to be two dominant factors. Research has shown that some marine ectotherms are shifting their bathymetric distributions in response to rapid anthropogenic ocean surface warming. Shallow-water species unable to undergo latitudinal range shifts may depend on bathymetric range shifts to seek refuge from warming surface waters. As a first step in constraining the molecular basis of pressure tolerance in shallow water crustaceans, we examined differential gene expression in response to acute pressure and temperature exposures in juveniles of the shallow-water shrimp Palaemonetes varians. Significant increases in the transcription of genes coding for an NMDA receptor-regulated protein, an ADP ribosylation factor, β-actin, two heat shock protein 70kDa isoforms (HSP70), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were found in response to elevated pressure. NMDA receptors have been implicated in pathways of excitotoxic damage to neurons and the onset of high pressure neurological syndrome (HPNS) in mammals. These data indicate that the sub-lethal effects of acute barotrauma are associated with transcriptional disturbances within the nervous tissue of crustaceans, and cellular macromolecular damage. Such transcriptional changes lead to the onset of symptoms similar to that described as HPNS in mammals, and may act as a limit to shallow water organisms' prolonged survival at depth.

Growth performance of the early life stages of broad-nosed pipefish, Syngnathus typhle (L.) fed different live or frozen diets

This work tested the effect of using different live and frozen feed on the growth performance of Syngnathus typhle. It was divided into two experiments. In Experiment I Artemia and Atlantic ditch shrimp (Palaemonetes varians) larvae were used as live diets, whilst in Experiment II frozen mysids Mesopodopsis slabberi and frozen P. varians were used. At the end of the first experiment juvenile pipefish grew significantly more when fed P. varians (P 0.05). In Experiment II juveniles were weaned with frozen diets but no significant differences were found between the two tested diets in all parameters tested. Final WG was 516.5 ± 63.3% and 566 ± 17.6%, and Feed Conversion Ratio (FCR) was 30 ± 1.5% and 28.2 ± 1.2% for animals fed P. varians and M. slabberi respectively. Results indicate that P. varians is an adequate diet to use during initial stages of the S. typhle life cycle and should be considered as a frozen diet for subsequent life stages of this species as an alternative to currently known natural diets.

Flow regime in a restored wetland determines trophic links and species composition in the aquatic macroinvertebrate community

In a restored wetland (South of Spain), where different flow regimes control water exchange with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic counterpart species Palaemon macrodactylus. This controlled m\\acrocosm offers an excellent opportunity to investigate how the effects of water management, through different flow regimes, and the presence of a non-native species affect the aquatic community and the trophic niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. We found that increased water exchange rate (5% day−1 in mixed ponds vs. 0.1% day−1 in extensive ponds) modified the aquatic community of this wetland; while extensive ponds are dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine origin of nutrients and primary production might explain seasonal and spatial differences found among ponds of this wetland. A combined analysis of gut contents and isotopic composition of the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap occurred when both species coexist at mixed ponds where a higher water exchange and high abundance of mysids and copepods diversifies the native species' diet. Thus differences in the trophic ecology of both species are clearly explained by water management. This experimental study is a valuable tool for integrated management between river basin and wetlands since it allows quantification of wetland community changes in response to the flow regime.

The influence of per offspring investment (POI) and starvation on larval developmental plasticity within the palaemonid shrimp, Palaemonetes varians

At the inter-specific level, per offspring investment (POI), degree of abbreviated development, and lecithotrophic potential all increase with increasing latitude and freshwater penetration among crustaceans. These traits are considered adaptations to conditions of decreasing growth potential. We hypothesise that this relationship between POI and abbreviated development also occurs at the intra-specific level. We studied the caridean shrimp, Palaemonetes varians, to investigate the hypothesis that under food-limited conditions, higher POI enables development through fewer larval instars. Under starvation stress, larvae from broods of greater POI (measured as hatchling brood average dry weight, DW) generally developed through fewer larval instars. With increasing starvation period, larval development time increased, whilst larval growth rate, juvenile DW, juvenile carbon mass, and juvenile carbon:nitrogen (C:N) ratio all decreased. Larval development time generally decreased with increasing brood average dry weight. In contrast, larval growth rate, juvenile DW, juvenile carbon mass, and juvenile C:N ratio all increased with increasing larval brood average DW. The relationship between POI and larval instar number (abbreviation of development) reported here is consistent with that at the inter-specific level and supports the concept that macro-ecological trends in development modes at the inter-specific level may be driven by selection occurring on POI at the intra-specific level.

Bioconcentration of the anionic surfactant linear alkylbenzene sulfonate (LAS) in the marine shrimp Palaemonetes varians: A radiotracer study

Uptake and depuration kinetics of dissolved [14C]C12-6-linear alkylbenzene sulfonate (LAS) were determined in the shrimp Palaemonetes varians using environmentally relevant exposure concentration. The shrimp concentrated LAS from seawater with a mean BCF value of 120Lkg−1 after a 7-day exposure. Uptake biokinetics were best described by a saturation model, with an estimated BCFss, of 159±34Lkg−1, reached after 11.5days. Shrimp weight influenced significantly BCF value with smaller individuals presenting higher affinity to LAS. To the light of a whole body autoradiography, major accumulation of LAS occurred in the cephalothorax circulatory system (gills, heart, hepatopancreas) and ocular peduncle, but not in the flesh, limiting potential transfer to human consumers. LAS depuration rate constant value of the shrimp was 1.18±0.08d−1 leading to less than 1% of remaining LAS in its tissues after 8days of depuration.

Energetic adaptations to larval export within the brackish-water palaemonine shrimp, Palaemonetes varians

Decapod crustaceans have repeatedly colonised brackish, freshwater, and terrestrial environments. Many decapods, which inhabit brackish and freshwater habitats, export larvae into estuarine and coastal areas where conditions for larval development may be better. In this study, we assess the starvation resistance, biochemical composition and respiration rate during larval development, and the effects of temperature on these factors within the brackish living palaemonine shrimp, Palaemonetes varians. Our results demonstrate that P. varians is highly resistant to starvation and may be considered facultative lecithotrophic in its first and second larval instars and planktotrophic from its third instar. This high starvation resistance is associated with a relatively large size, high carbon content (~45%) and C:N ratio (~4.2), and visible yolk reserves at hatching. These energy reserves are interpreted as an adaptation to the exportation of larvae from peripheral adult environments into mid and lower estuarine waters. Respiration rates varied with the moult cycle and were similar between fed and unfed larvae, suggesting that starved larvae do not suppress their metabolism as an energy saving strategy. Despite higher respiration rates at higher temperatures, energy loss throughout development (estimated from respiration rates) increased with decreasing temperature, whilst larval growth and development rates decreased with increasing temperature. High energy reserves at hatching, as within Palaemonetes varians, is an important life history adaptation in the colonisation of brackish and freshwaters, initially enabling the exportation of larvae from adult environments and eventually enabling lecithotrophy and direct development.

Correction: The Implications of Temperature-Mediated Plasticity in Larval Instar Number for Development within a Marine Invertebrate, the Shrimp Palaemonetes varians

Correction: The Implications of Temperature-Mediated Plasticity in Larval Instar Number for Development within a Marine Invertebrate, the Shrimp Palaemonetes varians

Uptake and depuration of PCB-153 in edible shrimp Palaemonetes varians and human health risk assessment

A medium-term mesocosm exposure study was conducted to elucidate bioaccumulation and depuration of polychlorinated biphenyl congener 153 (PCB-153) in edible shrimp Palaemonetes varians. Over the 15-day exposure period, shrimp under different exposure concentrations exhibited a significant increase in PCB-153 concentration compared with control organisms. Distinct bioaccumulation patterns and uptake rates were observed depending on the exposure concentrations. For low PCB-153 exposure levels (0.25μgL−1), accumulation followed a saturation model, reaching an apparent steady state after fifteen days exposure. For intermediate (2.5μgL−1) and high PCB-153 levels (25μgL−1), accumulation was faster and linear. In addition, the bioaccumulation rate was not proportional to PCB-153 concentration, and the bioaccumulation was higher at intermediate exposure concentrations. Regarding the depuration phase, P. varians lost up to 30% of PCB-153 after 72h and levels continued slowly to decrease until the end of the 30-d experimental period. However, PCB-153 levels in shrimp did not reach background values, and those exposed to moderate and high PCB-153 concentrations presented contamination levels much higher than the regulatory limit for human food consumption (75ngg−1 ww for Σ6 PCB).

The effects of temperature and pressure acclimation on the temperature and pressure tolerance of the shallow-water shrimp Palaemonetes varians

Anthropogenic effects on marine ecosystems (e.g. hypoxia, warming) at and beyond continental margins are assumed to affect physiological and biochemical boundaries to species’ distributions, potentially leading to habitat contraction across depth. Whether or not shallow-water benthic invertebrates are capable of undergoing depth-related migrations in response to such perturbations remains largely unknown. The few studies available have focused solely on whether colonisation of deep waters may be ongoing and on the ability of shallow-water species to tolerate low temperatures and high hydrostatic pressures: two physical parameters, which are thought to limit the depth range of a species. Those studies did not consider the effects of acclimation to low temperature and, especially, acclimation to high hydrostatic pressure on pressure tolerance. We demonstrate that acclimation to both low temperature (5 °C) and to high hydrostatic pressure (10 MPa) increases the pressure tolerance within the shallow-water shrimp Palaemonetes varians. Previous studies have demonstrated the impressive temperature and pressure tolerance of this shallow-water shrimp. Here, we provide evidence that a shallow-water species may acclimate to low temperature and high pressure and show greater pressure tolerance, suggesting that shallow-water organisms may be able to rapidly—and potentially stepwise—acclimate to the low temperature and high pressure conditions typical of the deep sea. These findings are of importance for understanding phylogenetic development from shallow- to deep-water species and the processes behind past, present and future bathymetric range shifts in species.

Quantitative dietary requirement of juvenile Atlantic ditch shrimpPalaemonetes variansfor lysine, methionine and arginine

This study was carried out to estimate lysine, methionine and arginine dietary requirements of juvenile Atlantic ditch shrimp, Palaemonetes varians. Three series of five isoproteic and isoenergetic diets [45% crude protein (CP), 14.7 MJ digestible energy (DE)/kg] were formulated to contain increasing levels of either lysine (1.2–2.8 g/100 g of diet), methionine (0.5–1.3 g/100 g of diet + 0.8% cysteine) or arginine (1.1–2.7 g/100 g of diet) and adequate levels of all other essential nutrients. Each experimental diet was fed to three groups of postlarvae (initial weight = 17 mg each) for 45 days at 19.9 ± 0.1°C. The dietary requirements for maximizing weight gain of juvenile P. varians, estimated using broken-line analysis vs. exponential model and expressed as per cent of dry diet, were 2.42 vs. 2.63; 0.96 vs. 0.99 and 2.05 vs. 2.39 for lysine, methionine and arginine respectively. These estimates of requirements of lysine, methionine and arginine for juvenile P. varians appear to be similar to those reported for penaeid shrimp species.

Do invaders always perform better? Comparing the response of native and invasive shrimps to temperature and salinity gradients in south-west Spain

Invasive species are often thought to benefit from climate change, outcompeting native species as temperatures increase. However, the physiological tolerance has been little explored as a potential mechanism explaining biological invasion success. In this study, we used empirical data from both invasive and native estuarine species as a case study to address the hypotheses that (1) invasive species show a better resistance to acute thermal stress, (2) invasive species present lower oxygen consumption rates owing to greater resistance to environmental stressors, and (3) native species have lower survival rates under chronic temperature and salinity stress. We conducted various comparative experiments on three sympatric and syntopic closely related shrimp species (one invasive Palaemon macrodactylus, and two natives Palaemon longirostris and Palaemonetes varians). We evaluated their critical temperature maxima, their oxygen consumption rates under different salinities and temperatures, and their survival rates under chronic salinity and temperature. We found that the invasive species was the most tolerant to rapid increase in temperature, and consistently consumed less oxygen over a broad range of temperatures and salinities. Palaemon macrodactylus also had lower mortality rates at high temperatures than P. longirostris. These results support previously reported differences in physiological tolerance between native and invasive species, with the invasive species always performing better. The consistently higher tolerance of the non-indigenous species to temperature variation suggests that climate change will increase the success of invaders.

Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:207-217 (2013) - DOI: https://doi.org/10.3354/meps10496 Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development Andrew Oliphant*, Sven Thatje Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, UK *Email: andrew.oliphant@noc.soton.ac.uk ABSTRACT: At the inter-specific level, per offspring investment (POI) is associated with larval development mode and follows a macro-ecological trend within the marine environment; higher POI and its associated greater degree of endotrophy and abbreviated development is found in cooler, high latitude regions. Here, the implications of between-brood-variation in hatchling energy content (measured as carbon mass) on larval starvation resistance and developmental plasticity within the caridean shrimp Palaemonetes varians were assessed. Results demonstrate that greater POI provides increased endotrophy and the potential for abbreviated development. In the absence of food, P. varians larvae from broods of higher hatchling energy content developed to more advanced larval stages and survived for longer before succumbing to starvation. In the presence of food, P. varians larvae from broods of higher hatchling energy content developed through fewer larval instars, showed higher growth rates, and had shorter development times. Also, for larvae developing through the same number of larval instars, larvae from broods of higher hatchling energy content developed to greater juvenile dry weight. These data support the hypothesis that macro-ecological trends in development mode are driven by inter-specific variations in POI. At the intra-specific level, phenotypic plasticity allows for environmentally mediated variations in POI. Under differential selection pressures, this flexibility may, thus, eventually permit the evolution of the diverse and complex life cycles observed in the marine environment. KEY WORDS: Carry-over effects · Evolution of lecithotrophy · Larval ecology · Palaemonidae · Palaemonetes varians · POI Full text in pdf format PreviousNextCite this article as: Oliphant A, Thatje S (2013) Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development. Mar Ecol Prog Ser 493:207-217. https://doi.org/10.3354/meps10496 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Accumulation and detoxification of copper and zinc by the decapod crustacean Palaemonetes varians from diets of field-contaminated polychaetes Nereis diversicolor

In an investigation of the trophic transfer of ecotoxicologically significant amounts of trace metals from prey to predator, Palaemonetes varians were fed with diets of Nereis diversicolor from two metal-contaminated estuaries, the Tavy and Restronguet Creek in SW England, and a control estuary, the Blackwater in SE England. The decapods accumulated increased concentrations of copper (but not zinc) from the metal-contaminated worms above an initial apparently regulated body copper concentration, in response to a high dietary copper input over a period up to 30days. High dietary challenges of copper caused the induction of MTLP (metallothionein-like proteins) in the hepatopancreas of the feeding decapods as a detoxification response, although the non-detoxified subcellular component of hepatopancreas accumulated copper also increased over time, probably in association with sublethal toxic effects.

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.

Respiratory responses to salinity, temperature and hypoxia of six caridean shrimps from different aquatic habitats

The respiratory response of six caridean shrimp species under different salinity and dissolved oxygen concentrations (DO) has been carried out at 20 and 25°C. The lowest mean specific oxygen consumption rates (MO2) were found for the less active benthic crangonids Crangon crangon and Philocheras monacanthus; whereas the highest ones corresponded to the two more mobile native palaemonids Palaemon longirostris and Palaemonetes varians. The level of oxygen regulation displayed by the different native species was mainly related with environmental characteristics of their common habitats: species with temporal (C. crangon) or permanent (P. varians) estuarine habitats tended to be more tolerant of salinity changes and/or hypoxia, than are fully marine (P. monacanthus) or freshwater (Atyaephyra desmarestii) species. The estuarine P. longirostris showed moderate oxygen independence, but rather independent of salinity and temperature fluctuations. The exotic shrimp P. macrodactylus seemed to have higher tolerance to hypoxia that its native counterpart P. longirostris at brackish waters, but only under moderate temperature (at 20°C). Results of this study suggest that a simultaneous evaluation of respiration rates and their dependence on DO could be an integrative way of determining the potential effects of increased salinity, temperature and hypoxia on aquatic species with different mobility and/or from different habitats.

Cloning and expression analysis of Cathepsin L cDNA of Exopalaemon carinicauda

Based on the EST sequence from a hemocyte cDNA library, the cathepsin L cDNA of Exopalaemon carinicauda (EcCatL) was cloned by rapid amplification of cDNA ends (RACE). The EcCatL cDNA was 1136 bp in length, which contains an open reading frame (ORF) of 960 bp, encoding a 319 amino-acid polypeptide. Homology analysis revealed that the amino acid sequence of EcCatL was highly conserved with its homologs in other crustaceans. The similarities of EcCatL with the CatL of Palaemonetes varians and Pandalus borealis were 92% and 76%, respectively. Phylogenetic analysis showed that EcCatL was in the same branch as that of Palaemonetes varians. The expression levels of EcCatL in different tissues were analyzed by quantitative real-time PCR. Expression of EcCatL was detected in all tested tissues of E. carinicauda, including hemocytes, gill, hepatopancreas, muscle, ovary, intestine, stomach and eyestalk, with the highest expression level in hepatopancreas. After challenged with Vibrio anguillarum or white spot syndrome virus, the expression of EcCatL were up-regulated in the hemocytes and hepatopancreas of E. carinicauda. Our results implied that EcCatL might play an important role in the prawn immune response.

Thermal adaptations in deep-sea hydrothermal vent and shallow-water shrimp

The hydrothermal vent shrimp Mirocaris fortunata is commonly exposed to acute thermal gradients and rapid fluctuations in water temperature. The shallow-water shrimp Palaemonetes varians experiences less acute but similar magnitude fluctuations in its thermal regime. Acute respiratory response to temperature shock, and temperature preference was assessed for both species. Oxygen consumption rates were assessed across the natural temperature range reported for M. fortunata. Rates increased with temperature for both species. P. varians had a significantly higher rate of oxygen consumption than M. fortunata at all temperatures except 4°C. The rate of increase in oxygen consumption with increasing temperature was also significantly greater for P. varians. M. fortunata selected a significantly higher temperature than P. varians. Mirocaris fortunata maintains its metabolism at a more stable rate, which is likely an adaptation to acute changes in temperatures occurring at hydrothermal vents.

Growth, Reproductive Performances, and Brood Quality of Long Snout Seahorse, Hippocampus guttulatus, Fed Enriched Shrimp Diets

This investigation examined the effect of using enriched shrimp (Atlantic ditch shrimp, Palaemonetes varians) diets on growth of long snout seahorse, Hippocampus guttulatus, and its effect on the reproduction rate and brood quality. Three diets were (1) natural wild‐caught shrimp (natural shrimp diet‐control diet), (2) wild‐caught shrimp fed an artificial feed for 10 d (enriched shrimp diet), and (3) wild‐caught shrimp fed one large meal of artificial diet and immediately frozen (ingested artificial feed shrimp diet). These diets were fed to seahorses during a 12‐wk growth trial. At the end, significant differences on the final wet weight were found between seahorses fed the three different treatments (P < 0.009). Seahorses fed ingested artificial feed shrimp diet had more broods (9), generated more juveniles per brood (299 ± 87), and significantly bigger juveniles (12.4 ± 1 mm) than seahorses fed natural shrimp diet and enriched shrimp diet. Significant differences in the morphometry of juveniles hatched from parents fed the three different dietary treatments (Wilk's λ = 0.2, F(6,460) = 47.41, P < 0.0001) were also found. Results indicate that the combined use of a natural diet (shrimp) and an artificial diet benefit growth and feed utilization by seahorses and have a direct impact on the reproductive rate and brood quality of H. guttulatus.

Early weaning of cuttlefish (Sepia officinalis, L.) with frozen grass shrimp (Palaemonetes varians) from the first day after hatching

AbstractThe suitability of early weaning cuttlefish usingfrozen grass shrimp, and its effects on growth andmortality was determined in a 50-day experiment.Three food groups were used. One group (C) wasfed with live prey until 25th DAH and weanedwith frozen prey until the end of the experiment.In the other two groups, weaning started at thefifth DAH (W5) and first DAH (W1), also withfrozen diet. Significant differences were foundbetween C and the remaining treatments (P <0.05) for mean wet weight (MWW), instantaneousgrowth rate (IGR), biomass (B) and mortality atthe 25th and the 50th DAH. Despite the lowergrowth (~1/3 of the achieved with live food) andhigher mortality (3% obtained by C versus 23% inthe W1 and W5 groups), C cuttlefish presented asimilar weight gain tendency to W1 and W5groups after weaning. This is the first record ofearly acceptance (at the first DAH) of frozen foodby cuttlefish hatchlings. These differences could berelated with digestive enzymes of cuttlefish andprey, changes in nutritional composition andamount of captured prey, etc. Future researchshould also address the effects of this early wean-ing on cuttlefish life cycle.Keywords: cuttlefish, Sepia officinalis, grassshrimp, Palaemonetes varians, early weaning, fro-zen foodIntroductionThe European cuttlefish (Sepia officinalis) is one ofthe most well-known cephalopods (Boletzky1983). During the last years, research on cuttle-fish has focused on its introduction as a new spe-cies for aquaculture. This is due to the biologicaland economical characteristics that this speciesdisplay, which have the potential for industrialculture. The most important are the short lifecycles and the fast growth rates which implylower production periods and associated costs. Onthe other hand, the inability to grow cephalopodson an inexpensive and storable prepared diet hasbeen identified as a bottleneck (Sykes, Domingues,Correia & Andrade 2006).Like in most finfish species, the first stage cul-ture of this species is known as the most problem-atic. This is due to the dependence on live feeds(Domingues, Sykes & Andrade 2001; Domingues,Bettencourt & Guerra 2006; Sykes, Domingues A Castro 1991; Lee, Forsy-the, DiMarco, DeRusha & Hanlon 1991; Castro,DiMarco, DeRusha & Lee 1993) demonstrated poorresults in growth, survival and promoted cannibal-ism [e.g. 67.5% and 22.5% survival rates for pel-lets and surimi respectively (Castro et al. 1993)].Domingues, Dimarco, Andrade and Lee (2005) con-firmed the possibility of rearing cuttlefish with pre-pared foods. Nevertheless, these authors reportedextremely low growth rates when compared with

Adaptation to thermally variable environments: capacity for acclimation of thermal limit and heat shock response in the shrimp Palaemonetes varians

In the context of climate change, there is a sustained interest in understanding better the functional mechanisms by which marine ectotherms maintain their physiological scope and define their ability to cope with thermal changes in their environment. Here, we present evidence that the variable shrimp Palaemonetes varians shows genuine acclimation capacities of both the thermal limit (CT(max)) and the heat shock response (hsp70 induction temperature). During cold acclimation to 10 °C, the time lag to adjust the stress gene expression to the current environmental temperature proved to exceed 1 week, thereby highlighting the importance of long-term experiments in evaluating the species' acclimation capacities. Cold and warm-acclimated specimens of P. varians can mobilise the heat shock response (HSR) at temperatures above those experienced in nature, which suggests that the species is potentially capable of expanding its upper thermal range. The shrimp also survived acute heat shock well above its thermal limit without subsequent induction of the HSR, which is discussed with regard to thermal adaptations required for life in highly variable environments.