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The effect of climate change on ocean circulation and environmental conditions will likely impact important fisheries species which have a limited habitat range and a prolonged larval dispersal phase. Based on projections from a regional scale ice‐ocean model (RCP 8.5 scenario), we investigated the spatial distribution variability of the bentho‐pelagic northern shrimp (Pandalus borealis) preferred depth and thermal habitat and larval settlement patterns in the Newfoundland and Labrador waters for the next 70 years. Our projections of ocean temperature revealed the persistence of major shelf‐scale temperature features, but a gradual increase of bottom water temperatures by more than 4°C by 2090. Such warming led to an expansion of the potentially suitable habitat for northern shrimp from 2010 to 2050 prior to a decline and shift towards more coastal and southern areas from 2060 to 2090. The modification of the northern shrimp suitable habitat distribution, associated with changes in the ocean circulation features, affected the settlement patterns from larval dispersal simulations and the temperatures encountered by larvae. During the projection period, historically important areas were mostly negatively impacted in terms of suitable habitat and settlement potential, whereas areas that had been less important in the past (e.g., the north and the shallow area to the south) were projected to receive more settlers in comparison with the historical period. Our study demonstrated the important role of shelf‐scale processes in determining larval connectivity and suggests that regional scale ocean models are needed to assess potential impacts of climate change on fisheries and ecosystems. [ABSTRACT FROM AUTHOR]

Mismatches between assessment and ecological processes can increase the likelihood of resource mismanagement, lead to the misinterpretation of population dynamics, and impact decision making. Striped shrimp (Pandalus montagui) are an important part of Canada's subarctic marine ecosystems but have little historical research or assessment focus. Off northern Canada, striped shrimp are currently assessed separately within three assessment areas, despite these areas forming an open, dynamic system with population mixing throughout. Although assessed using data from a common survey, the differing time series of available data within each area have hampered efforts to consider the dynamics of the stock as one population and create a single biomass index for the area. Consequently, there is a spatial-scale mismatch between the biological resource and the assessment and management scales. To address causes of this scale mismatch, we developed a spatiotemporal model that can accommodate inconsistent survey coverage and can be used to estimate annual biomass of fishable striped shrimp throughout the study area over the entire time series (2005–2022). Meanwhile, to address deficiencies in biological knowledge, we concomitantly explored potential environmental and ecosystem covariates (i.e., bottom temperature, bottom salinity, and predicted potential predator densities) to further scientific understanding of striped shrimp's relationships with their ecosystem. Our results build a cohesive population-level biomass time series and found fishable striped shrimp densities were related to depth, bottom temperature, and lagged predicted redfish density. [ABSTRACT FROM AUTHOR]

The Eastern Canadian northern shrimp population, representing one of the most important fisheries in the region, decreased dramatically since the mid‐2000s to a historical low in 2017, but changes were not spatially uniform. Applying a biophysical model within Newfoundland and Labrador (NL) management areas, we investigated connectivity processes during the long pelagic larval phase (2–3 months) of Pandalus borealis and key drivers of larval dispersal in different environmental conditions. We selected 3 years representative of contrasting North Atlantic Oscillation (NAO) phases to assess potential larval dispersal patterns of the northern shrimp population in NL, and hierarchically assessed the impact of the timing of release (yearly and daily), release location, and vertical migration behaviour on shrimp larval dispersal. Overall, we found that populations located on the northern Newfoundland and Labrador shelf supplied potential settlers to southern populations because of the dominant Labrador Current. Ocean circulation and current velocities during the NAO positive year differed from other years, generating contrasting settlement spatial patterns. Larval release location and vertical migration behaviour were the two most important influences on the strength of larval supply and settlement patterns. Inclusion of diel and ontogenic swimming behaviour increased settlement success of larvae released from inshore areas, regardless of study years. Our study improves understanding of northern shrimp stock‐recruitment relationships, their sensitivity to changing environmental conditions, and spatially non‐homogeneous population decline for bentho‐pelagic species with a long larval phase, which could potentially help improve management strategies. [ABSTRACT FROM AUTHOR]

We investigated the genetic structure of six populations of Pandalus latirostris Rathbun, 1902 inhabiting seagrass beds along the coast of eastern Hokkaido, Japan, using two molecular markers: a partial sequence of the mitochondrial DNA control region (CR), and the length polymorphism in seven microsatellite loci in the nuclear genome. Both markers revealed significant genetic differentiation between local populations. Analysis of molecular variance (AMOVA) suggested a hierarchical population structure consisting of regional population groups in the study area. Genetic and spatial distances correlated significantly (P = 0.048) when CR sequences were used but did not correlate (P = 0.26) when microsatellite markers were used. These results show that local populations of P. latirostris are genetically different, although the level of difference was low and did not completely correlate to the geographic distance. Gene flow between local populations was probably restricted, mainly due to particular features of this species, such as the absence of planktonic larval stages and the fact that it lives exclusively in patchy seagrass beds. Our results provide basic information of population genetics in this species, which is important for its conservation and management. [ABSTRACT FROM AUTHOR]

Pandalus species display the following features that make it difficult to apply traditional age-based stock assessment models: ( i) difficulty of determining age in the absence of hard parts retained through the molt; ( ii) sex change in which individuals mature first as males and then transform to females; and ( iii) potentially strong influence of environmental conditions on recruitment population dynamics. In this context, we propose a seasonal, size-structured assessment model dedicated to stock assessment of hermaphroditic Pandalidae. The modeling framework incorporates a submodel for changes of length at sex transformation and functions to incorporate environmental effects on recruitment dynamics. The model can be directly fitted to length-structured data, overcoming the length to age conversion problem. The model has a seasonal time step that allows it to account for seasonal variations in biological processes and fishing patterns. The model provides stock assessment outputs, such as fishing mortality and stock biomass estimates, and sex-specific abundance-at-length. The model is applied to the exploited shrimp stock of Pandalus borealis in the Gulf of Maine as an example of its utility. The model proposed in this study is flexible and generic and can be applied to many other exploited stocks. [ABSTRACT FROM AUTHOR]

Integrated, size-structured stock assessment models are now being used widely for assessment and management of hard-to-age species. However, few studies have attempted to evaluate their performance. A seasonal, size-structured assessment model with environmental covariates has been developed for hermaphroditic Pandalidae. We conducted simulations to evaluate its sensitivity to model configuration and performance with various misspecifications. Ignoring the seasonal fishing pattern (half-year closure) led to risk-prone assessment results of overestimating spawning stock biomass (SSB) and recruitment ( R) and underestimating fishing mortality ( F). Failure to incorporate environmental signals when the recruitment dynamics was environmentally driven led to bias in recent estimates of SSB, R, and F in the simulation. Ignoring annual variability in growth resulted in large estimation bias. Failing to account for time-varying natural mortality ( M) led to strong biases; however, misspecifying size-specific M produced even stronger estimation bias. This result may depend on the variation of M among size classes. Under no model misspecifications, an unbiased estimate of M could be obtained by taking advantage of the seasonal fishery closure. Annual growth parameters were also estimable, but the large number of parameters with annual growth made it difficult for the model to converge. [ABSTRACT FROM AUTHOR]

Expansion of oxygen deficient waters (hypoxia) in the northeast Pacific Ocean (NEP) will have marked impacts on marine life. The response of the resident communities will be a function of their ecophysiological constraints in low oxygen, although this remains untested in the NEP due to a lack of integrative studies. Here, we combine in situ surveys and lab-based respirometry experiments were conducted on three indicator species (spot prawn Pandalus platyceros, slender sole Lyopsetta exilis, squat lobster Munida quadrispina) of seasonally hypoxic systems in the NEP to test if metabolic constraints determine distributions and energy sequestration in a hypoxic setting. These experiments were integrated with a global review of critical oxygen levels ( [ABSTRACT FROM AUTHOR]

This investigation reports mechanical properties of the exoskeleton of deep sea shrimp, Rimicaris exoculata, at temperatures ranging from 25 to 80 °C measured using nanoindentation experiments. The measured properties are compared with the corresponding shallow water shrimp (Pandalus platyceros) exoskeleton properties. Scanning electron microscopy suggests that both types of shrimp exoskeletons have the twisted plywood, Bouligand structure. However, they differ in the volume fraction and distribution of mineral content. The variations in the nanoindentation measured hardness values of the examined shrimp exoskeletons are found to be strongly correlated with the corresponding compositional difference between the two exoskeleton types. Nanoindentation creep strain rate measurements are performed to provide an assessment of the two types of exoskeleton for the role of proteins and minerals to cause difference in behavior and properties between the two shrimp species. The measured creep load–depth data are fitted with a viscoelastic creep function to find the creep compliance as a function of experimentally varying temperature and in the context of natural variations in mineral content. [ABSTRACT FROM PUBLISHER]

Population structuring in the northern shrimp (Pandalus borealis) in the North Sea area (including Fladen and Skagerrak) was studied by micro-satellite DNA analyses. Screening 20 sample locations in the open ocean and Skagerrak fjords for nine loci revealed low, but significant genetic heterogeneity. The spatial genetic structure among oceanic samples of Skagerrak and the eastern North Sea was weak and non-significant, consistent with the current management regime of one single stock. However, Skagerrak fjord samples generally displayed elevated levels of genetic differentiation, and significantly so in several pairwise comparisons with other fjords and oceanic samples. Although the Skagerrak fjord populations are of less economic value, some of them are regulated separately (e.g. the Gullmarsfjord) and local stocks may prove important to uphold genetic variability and biocomplexity in a changing environment. [ABSTRACT FROM AUTHOR]

Based on the assumption that depleted stocks would have recovered during a six-year layoff from fishing, trapping for deep-water spiny lobster Palinurus delagoae and slipper lobster Scyllarides elisabethae off eastern South Africa resumed in 2004 until 2007. A generalised linear modelling approach was used to investigate the effects of year, sampling area, depth, month and trap soak-time on catch and lobster size, and to construct standardised abundance indices. The renewed trapping rapidly reversed partially restored nominal catch rates. Fishing strategy changed from targeting spiny lobsters during the first months of each fishing season to targeting slipper lobsters during later months. Small spiny lobsters were abundant in the southern area, identified as a recruitment hotspot. Spiny lobster abundance and size in this area increased over four years of fishing, but conversely, large adult spiny lobsters predominated in the central and northern areas, where trapping depleted their abundance over time. The adult populations in the central and northern areas are upstream from the recruitment hotspot, and are presumably a source of larvae. Slipper lobster abundance peaked in 2005, remained relatively constant across areas, and increased with depth. Trapping for deep-water lobster is unlikely to be sustainable in its present form. However, the clear gradients in spiny lobster size and abundance by sampling area and depth provide a good framework for spatial management planning. [ABSTRACT FROM AUTHOR]

Abstract: Evaluating vitality and predicting mortality in commercially exploited crustaceans is increasingly important for reducing discard mortality and for improving handling and shipping for live markets. A suite of 10 reflex actions were identified in spot prawns (Pandalus platyceros) that vary in sensitivity to injury and type of stressor. After establishing a baseline for stereotypic reflexes, prawns were subjected to physiological stress (emersion up to 60min) and physical trauma (dropping). The prawns were tolerant of air exposure up to 40min, but susceptible to injuries from dropping and the results within treatments were variable. However, mortality of individuals over a 30-day recovery period was closely related to a simple reflex impairment score calculated as the sum of reflexes lost (range=0–10) and the effects of different injuries were additive. Logistic regression indicated that reflex impairment was an excellent predictor of delayed mortality (87.5% correct predictions) across prawn size (35–48mm carapace length) and treatment types. A sigmoid curve describing the relationship between impairment and mortality was termed a Reflex Action Mortality Predictor. This RAMP approach should be a valuable tool in practical experiments related to both discard mortality and handling live crustaceans without the need for tagging or long-term holding. [Copyright &y& Elsevier]

Despite the economic importance of shrimp fisheries, few analytical tools have been developed to assess their stocks, and traditional stock assessment models are not appropriate because of biological specificities of Pandalus species. In this context, we propose SPAM (Sex-Structured Pandalus Assessment Model), a model dedicated to protandric hermaphrodite pandalids stock assessment. Pandalids are difficult to assess because the cues affecting sex change, size at recruitment, and mortality variability are not well understood or characterized. The novel structure of the model makes it possible to adequately describe variability in natural mortality by stage and in time, as well as variability in size at sex change and recruitment. The model provides traditional stock assessment outputs, such as fishing mortality estimates and numbers of individuals, and provides in addition yearly natural mortality estimates. The model is applied to the exploited shrimp stock of in Sept-Îles (Québec, Canada) as an illustrative example of the utility of the approach. [ABSTRACT FROM AUTHOR]

The objective of the study was to investigate if reproductive characteristics of Pandalus eous affect the depth distribution in the East Sea of Korea. P. eous was found at depths of 500–900 m in the East Sea of Korea, with the highest percentage occurrence (34%) at 500 m. A negative correlation was observed between the number of individuals and the depth. The overall sex ratio also turned out to be significantly correlated with depth. On average, the larger individuals (bigger than 26.37 cm), which included transitional, female, and ovigerous females, were mostly distributed at 700 m depth. The percentage of males increased by depth and ovigerous females were mainly distributed in the shallow water (300 m) during winter. Ovigerous females were not found at 900 m, which is the deepest depth range in this study. The percentage of transitional individuals was greatest at 500 m and decreased gradually with depth. All ovigerous female individuals were of the spent ovarian stage in winter. Female numbers in the ripe ovarian stage increased with depth and immature females rarely appeared. The gonadosomatic indices of the nonovigerous females and ovigerous females were highest at 700 m in depth. The mean egg size of P. eous was 0.83±0.11 mm3 in the non–eyed stage and 0.93±0.17 mm3 in the eyed stage. [ABSTRACT FROM AUTHOR]

The requirement of gross protein and energy and the optimal ratio of these in practical diets for pink shrimp (Farfantepenaeus paulensis) juveniles in different salinities were determined. Shrimp with a mean initial weight of 0.353 g were stocked in 54 plastic tanks at initial densities of 40 ind m-2. The experiment was factorial, with three levels of gross protein (24, 35, 48%), three levels of salinities (10, 20, 30 psu), and two levels of gross energy (3200, 4200 kcal kg-1); the experiment lasted 25 days and considered three replicates. The results showed that salinity and protein had a significant effect (P < 0.05) on weight gain and the specific growth rate, but did not influence on survival. The energy had no significant effect on survival, growth rate, or weight gain. The response of the shrimp to the gross energy and protein level showed different requirements according to the different salinities tested. At salinity of 10 psu, the adequate level was 35% gross protein and 4200 kcal kg-1 (83.3 mg PB kcal-1), whereas at salinities of 20 and 30 psu, levels of 24% gross protein and 3200 kcal kg-1 (75.0 mg PB kcal-1) were appropriate. [ABSTRACT FROM AUTHOR]

While the study of phenotypic variation is a central theme in evolutionary biology, the genetic approaches available to understanding this variation are usually limited because of a lack of genomic information in non-model organisms. This study explored the utility of next-generation sequencing (NGS) technologies for studying phenotypic variations between 2 populations of a non-model species, the Hokkai shrimp (Pandalus latirostris; Decapoda, Pandalidae). Before we performed transcriptome analyses using NGS, we examined the genetic and phenotypic differentiation between the populations. Analyses using microsatellite DNA markers suggested that these populations genetically differed from one another and that gene flow is restricted between them. Moreover, the results of our 4-year field observations indicated that the egg traits varied genetically between the populations. Using mRNA extracted from the ovaries of 5 females in each population of Hokkai shrimp, we then performed a transcriptome analysis of the 2 populations. A total of 13.66 gigabases (Gb) of 75-bp reads was obtained. Further, 58,804 and 33,548 contigs for the first and second population, respectively, and 47,467 contigs for both populations were produced by de novo assembly. We detected 552 sequences with the former approach and 702 sequences with the later one; both sets of sequences showed greater than twofold differences in the expression levels between the 2 populations. Twenty-nine sequences were found in both approaches and were considered to be differentially expressed genes. Among them, 9 sequences showed significant similarity to functional genes. The present study showed a de novo assembly approach for the transcriptome of a non-model species using only short-read sequence data, and provides a strategy for identifying sequences showing significantly different expression levels between populations. [ABSTRACT FROM AUTHOR]

Abstract: Methyl farnesoate (MF), a crustacean juvenile hormone (JH) analog, plays important roles in the regulation of a number of physiological processes such as molting, metamorphosis, and reproduction. Understanding its metabolic pathway is a key for various potential applications in crustacean aquaculture, including artificial seed production and enhancement of growth. Although the synthetic pathway of MF is well established, little is known about its degradation and recycling in crustaceans. In insects, juvenile hormone esterase (JHE), a carboxylesterase, is responsible for JH inactivation. Two cDNAs, encoding JHE-like carboxylesterases (CXEs) from the hepatopancreas and ovary of Pandalopsis japonica, were isolated by using a combination of in-silico data mining from an expressed sequence tag (EST) database and traditional PCR-based cloning. The full length Pj-CXE1 (2084bp) and Pj-CXE2 (1985bp) cDNAs encoded proteins composed of 584 and 581 amino acids, respectively. The active site sequence and domain organization of the Pj-CXEs were highly conserved, including the catalytic triad and other motifs, which suggested that both Pj-CXEs are biologically active carboxylesterases. Phylogenetic analysis of the deduced sequences of Pj-CXEs showed that both were most closely related to the JHEs from non-lepidopteran insects. End-point RT-PCR showed that Pj-CXE1 was expressed primarily in the gonad, whereas Pj-CXE2 was expressed in both the hepatopancreas and hindgut. Quantitative PCR showed that Pj-CXE1 was upregulated in the gonads by eyestalk ablation (ESA). In contrast, ESA had no significant effect on Pj-CXE2 expression in hepatopancreas or gonad. This is the first report of the cloning of two JHE-like CXE cDNAs in decapods and the upregulation of Pj-CXE1 by acute withdrawal of eyestalk neuropeptides. Further study is needed to understand the function of CXEs in MF metabolism and its regulation by eyestalk neuropeptides. [Copyright &y& Elsevier]

Abstract: The Northwest Atlantic marine community underwent dramatic changes during the last 30years, including the collapse of many groundfish stocks and an increase in shrimp populations. Greenland halibut Reinhardtius hippoglossoides is an important commercial species and one of the top fish predators in this system. It is a large, wide-ranging flatfish that is found at depths up to 2200m and it has an opportunistic diet which makes it a potential candidate for an ecosystem indicator. Analysis of stomach contents of Greenland halibut between 1978 and 2003 indicates that diet composition reflects the major changes in community structure. Over the entire period there was a clear increase in the importance of invertebrates, particularly after 1992. This change was associated with a higher importance of Pandalus shrimp and Gonatus squid and a protracted reliance on zooplankton by predators under 25cm length. Capelin Mallotus villosus was the dominant prey between 1978 and 1992 for predators in the 12–63cm range, but its importance dropped off drastically in the mid 1990s. Levels of main prey in the diet of Greenland halibut correlated well with fishery-independent surveys. Greenland halibut sample capelin well, compared to bottom trawl surveys and acoustic surveys. Greenland halibut consumed small shrimp which are not routinely caught by surveys and may be important in deriving information on year classes and growth of shrimp. Our results suggest that Greenland halibut''s diet is a useful tracker of ecosystem change. [Copyright &y& Elsevier]

Abstract: Endosulfan is a neurotoxic organochlorine insecticide of the cyclodiene family of pesticides that inhibits molting and reproduction in aquatic crustaceans. In order to determine the molecular mechanism of endosulfan as an endocrine disrupting chemical (EDC), differential display RT-PCR (DDRT-PCR) was used to isolate genes in the shrimp, Pandalopsis japonica, affected by endosulfan exposure. PCR screening of cDNA from the hepatopancreas from control and endosulfan-exposed animals, using 120 sets of random primers, yielded partial cDNAs encoding two vitellogenin-like proteins (Pj-Vg1 and -Vg2). Complete sequences were obtained using a combination of RT-PCR and RACE-PCR. Pj-Vg1 (7883bp) encoded a protein composed of 2533 amino acid residues (283.27kDa estimated mass), whereas Pj-Vg2 (7792bp) encoded a protein composed of 2537 amino acids residues (284.87kDa estimated mass). Alignment of the Pj-Vgs with those of other vitellogenins identified a conserved subtilisin cleavage site (RQKR) and the lipoprotein N-terminal (vitellin), DUF1081, and von Willebrand factor type D domains, indicating both genes encoded functional proteins. Phylogenetic analysis showed that Pj-Vg1 and -Vg2 were most similar to Pandalus hypsinotus Vg. Both Pj-Vg1 and -Vg2 were expressed primarily in the hepatopancreas, although the Pj-Vg2 transcript was also detected in the ovary. The effects of the 3-day endosulfan exposure (2.5µg/L and 25µg/L) on Vg expression in the hepatopancreas were determined by quantitative RT-PCR. Expression of both transcripts was significantly inhibited at 25µg/L suggesting that Pj-Vgs can be used as indicator for endosulfan exposure. [Copyright &y& Elsevier]

Background: PCR amplification of minute quantities of degraded DNA for ancient DNA research, forensic analyses, wildlife studies and ultrasensitive diagnostics is often hampered by contamination problems. The extent of these problems is inversely related to DNA concentration and target fragment size and concern (i) sample contamination, (ii) laboratory surface contamination, (iii) carry-over contamination, and (iv) contamination of reagents. Methodology/Principal Findings: Here we performed a quantitative evaluation of current decontamination methods for these last three sources of contamination, and developed a new procedure to eliminate contaminating DNA contained in PCR reagents. We observed that most current decontamination methods are either not efficient enough to degrade short contaminating DNA molecules, rendered inefficient by the reagents themselves, or interfere with the PCR when used at doses high enough to eliminate these molecules. We also show that efficient reagent decontamination can be achieved by using a combination of treatments adapted to different reagent categories. Our procedure involves γ- and UV-irradiation and treatment with a mutant recombinant heat-labile double-strand specific DNase from the Antarctic shrimp Pandalus borealis. Optimal performance of these treatments is achieved in narrow experimental conditions that have been precisely analyzed and defined herein. Conclusions/Significance: There is not a single decontamination method valid for all possible contamination sources occurring in PCR reagents and in the molecular biology laboratory and most common decontamination methods are not efficient enough to decontaminate short DNA fragments of low concentration. We developed a versatile multistrategy decontamination procedure for PCR reagents. We demonstrate that this procedure allows efficient reagent decontamination while preserving the efficiency of PCR amplification of minute quantities of DNA. [ABSTRACT FROM AUTHOR]

The population dynamics of Pandalus gracilis were investigated in the southeast coastal area of Korea, between May 1998 and April 2000. The number of females was greater than that of males and of intersexes. Based on dry weight of egg masses at the early stage, the reproductive output averaged 34% of female weight. A higher gonadosomatic index (GSI) was observed from December to June. Ovigerous females occurred from December to September. During the incubation period, the egg volume significantly increased and brood loss of eggs occurred. A significant difference in ovarian weight between females with early eggs and late egg stages was found. This indicates that ovarian maturation occurs during the incubation time, suggesting that females are potentially consecutive breeders, capable of multiple spawnings during a reproductive season. Spawning by a single female seems to occur consecutively in a single reproductive period. Female maturity was determined by the frequency of both ovigerous females and females with a maturing ovary. The size at 50% sexual maturity (CL50) was estimated as 9.2 mm. The size distribution in the population was similar in the two years of this study. [ABSTRACT FROM AUTHOR]

The present paper reports on four species of pandalid shrimp from the Yellow Sea: Pandalus gracilis Stimpson, 1860, Pandalus prensor Stimpson, 1860, Plesionika izumiae Omori, 1971, and Procletes levicarina (Bate, 1888). Pandalus prensor and Procletes levicarina are now recorded with certainty from the Yellow Sea for the first time. [ABSTRACT FROM AUTHOR]

The complete larval development of Pandalus gracilis Stimpson is described based on larvae reared in the laboratory. The species has four larval stages (stages 1-4) and one postlarval stage (stage 5). The survival rate of the postlarva stage is very high. Of the 40 larvae reared individually, 39 larvae moulted to the postlarva stage within approximately 21 days at a rearing temperature of 15°C. Larval morphological characteristics of the species are described and figured. Larval development of P. gracilis is compared with other Pandalus and Pandalopsis species. Komai (1999) divided species of Pandalus into four species groups based on adult morphology. Pandalus gracilis belongs to the P. hypsinotus group. In this study, using larval characters, the P. hypsinotus group can be divided into two groups by the appearance of the mandibular palp and the shape of the telson: the first group contains P. hypsinotus and P. danae, and the second group contains P. gracilis, P. prensor, and P. nipponensis. [ABSTRACT FROM AUTHOR]

Thelohania butleri, a microsporidian that causes mortality and commercial losses in the smooth pink shrimp Pandalus jordani, is of taxonomic interest as a species resembling the poorly studied type species, Thelohania giardi, of the large, polyphyletic genus Thelohania. We examined the ultrastructure of T. butleri to confirm its identity and reconstructed phylogenies using ribosomal DNA to find the relationship of T. butleri with other Thelohania species in crayfish and ants. Light and transmission electron microscopy from specimens collected from the type locality, the Pacific coast of Canada, confirmed the identity and demonstrated a development similar to that of T. giardi, involving a series of binary fissions without formation of a plasmodium. Phylogenetic analyses consistently showed T. butleri to be distantly related to other Thelohania species, and closely related to species from marine decapods within a larger fish-parasitic clade. Together, features such as host group and habitat, developmental morphology, and phylogeny suggest T. butleri may be a closer relative to T. giardi than any other Thelohania species represented by DNA data so far, and thus imply species from crayfish and ants may not belong in this genus. Results also confirm that genus Thelohania and family Thelohanidae are in need of revision. [ABSTRACT FROM AUTHOR]

The genetic structure of shrimp (Pandalus borealis) in the Northeast Atlantic was examined by RAPD analysis on specimens caught at eight stations in the Barents Sea, three off Svalbard, two off Jan Mayen, and in two northern Norwegian fjords (19< n >31 per station). A total of 34 polymorphic markers generated by seven 10-mer arbitrary primers was used to assess the genetic population structure using analysis of molecular variance (AMOVA). There was considerable RAPD diversity (>90%) among shrimp at all stations. The two Norwegian fjords and the Jan Mayen stations were different from all the others, and the Jan Mayen stations also differed from each other. More than 98% of the genetic variation between Barents Sea and Svalbard was ascribed to individual diversity, and there was no significant difference between the two areas, although there seemed to be a subpopulation structure in the Barents Sea. Principal component analysis on the frequency of each RAPD marker on each sampled station confirmed the presence of three populations: Barents Sea and Svalbard, northern Norwegian fjords, and Jan Mayen. We postulate that the large genetic variability found at an individual level may provide the total population with a diverse genetic pool from which traits can be selected to respond to variations in local environmental conditions, and that this local selection may be the cause of the subpopulation structure observed. [Copyright &y& Elsevier]

Northern shrimp Pandalus borealis (Krøyer) larvae hatch in the northern Gulf of St. Lawrence from early May to the end of June, and larval development occurs over a range of relatively cold water temperatures. Because of the long duration of the pelagic phase and the difficulty of sampling all successive larval stages at sea, we used laboratory experiments to assess the effects of water temperature on larval development and growth. In spring 2000, P. borealis larvae were reared from hatching to the first juvenile stages (i.e., stage VI and VII) at three temperatures (3, 5, and 8°C) representing conditions similar to those in spring in the northern Gulf of St. Lawrence. Larval development and growth were dependent on temperature, with longer duration and smaller size (cephalothorax length, CL, and dry mass, DM) at 3°C relative to the 5 and 8°C treatments. There were no significant differences in the morphological characters of the different stages among treatments, indicating that regular moults occurred at each temperature. The results suggest a negative impact of cold temperatures (lower intra-moult growth rates and smaller size) and, possibly, higher cumulative mortality due to longer development time that could affect the success of cohorts at sea. However, CL and DM for stage III and later larvae were smaller than those of larvae identified at the same developmental stage in field locations. It is possible that the diet offered to larvae in this experiment ( Artemia nauplii, either newly hatched nauplii or live adults, depending on the developmental stage) was not optimal for growth, even though it is known to support successful P. borealis larval development. In the field, there is the possibility that phytoplankton contributes to the larval diet during the first stages and stimulates development of the digestive glands. Furthermore, the nutritional quality of the natural plankton diet (e.g., high protein content, fatty acid composition) might be superior and favourable to higher growth rates even at lower temperatures. [ABSTRACT FROM AUTHOR]

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0°C to as high at 6°C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration ( VO2), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA– VO2) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8°C), developmental stage (I–V at 3°C, I–VII at 5°C and 8°C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO2 with body mass was faster at 5°C than at 3 or 8°C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5°C than at 3 and 8°C. However, MS did not limit growth in this study, since it explained only 39% of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q10 of all three metabolic variables ranged from 1.6 and 2.2 for stages I–V larvae, except for VO2 at stage I (3.9) and stage III (2.9). [ABSTRACT FROM AUTHOR]

In most protandrous species, male size advantage is generally regarded as unimportant in determining the timing of protandrous sex change. In pandalid shrimp, the size/age of male sex change often fluctuates among years and populations, but the adaptive significance of late reversing males (LRMs) is not well understood. This study experimentally examined the adaptive significance of LRMs in the protandrous pandalid shrimp Pandalus latirostris Rathbun. Field and laboratory studies were carried out in August–September of 1998–2002 on P. latirostris in Notoro Lagoon, Japan (44°03′N; 144°10′E). Mature females that had molted (i.e. mate receptive) were tethered in the field and their mating behavior with wild males was observed. Copulations occurred with a single male at a time, although other males could sequentially mate with a tethered female. Because tethered females rejected male approaches, males had difficulty transferring their spermatophores. In the laboratory, males copulated with non-tethered, recently molted females for only 15 min after molting. Recently molted females are wary of potential predators, since their soft exoskeleton makes them particularly vulnerable. Fast access by males enhanced fertilization success in this shrimp. The effect of male size on mating success in the laboratory was examined. Both small and large males successfully inseminated females in the absence of competitors. In experiments where large, medium, and small males competed for a female, however, larger males guarded females longer than smaller males, until the female molted and became receptive. Moreover, large males were more successful at copulating once molting occurred. These results imply that male-male competition drives delayed sex change in some situations. [ABSTRACT FROM AUTHOR]

Sex change, growth, and mortality of Pandalus populations are important to stock management. To investigate the importance of these life history traits in setting management strategies, we performed a variety of simulatoins using a length-based model. We compared three populations: a Kachemak Bay, Alaska type (K_pop); a hypothetical one with the same growth but without sex change (H_pop); and a northern Barents Sea type (B_pop). The main difference between K_pop and B_pop is growth rate; K_pop has faster growth and a shorter live span, whereas B_pop lives farther north, and therefore has slower growth and greater longevity. We found that populations with sex change were more sensitive to fishing pressure. Continuous fishing was detrimental to K_pop when instantaneous fishing mortality was above 0.3, but threshold management, i.e. closing the fishery at a low population level, greatly improved the population performance. B_pop, the slower-growing, longer-lived population required larger mesh sizes than K_pop, but increasing mesh size could not prevent collapse under high fishing mortality, and fishery closure under threshold management was necessary to sustain the population. Abrupt decrease of age one and two males caused populations with sex change to fluctuate in spawning biomass. Seasonality in growth and natural mortality is also pertinent to shrimp management. Given faster growth in summer, higher natural mortality in summer means fishing after spring hatching tends to result in higher cumulative yield than fishing after fall mating, and vice versa. In addition, fishing after hatching is in general more robust to overfishing. From the simulation analyses, we concluded that both sex change and seasonality of growth and mortality of Pandalus populations should be taken into account in shrimp management. [ABSTRACT FROM PUBLISHER]

The genus Pandalus Leach, 1814, is revised based upon the abundant material from collections in various museums or institutions in the world. Altogether 20 species are recognized which appear to form five groups. Nineteen species are recognized in Pandalus, three of which are described as new: P. curvatus from southern Japan, and P. chani and P. formosanus from Taiwan. Four informal species groups are also recognized within the genus: P. montagui group (P. montagui Leach, 1814; P. borealis Kroyer, 1838; P. goniurus Stimpson, 1860; P. jordani Rathbun, 1902; P. tridens Rathbun, 1902; and P. eous Makarov, 1935); P. stenolepis group (P. stenolepis Rathbun, 1902; P. curvatus sp. nov.); P. hypsinotus group (P. hypsinotus Brandt, 1851; P. danae Stimpson, 1857; P. prensor Stimpson, 1860; P. gracilis Stimpson, 1860; P. gurneyi Stimpson, 1871; P. nipponensis Yokoya, 1933; P. teraoi Kubo, 1937; P. chani sp. nov.; and P. formosanus sp. nov.); and P. platyceros group (P. platyceros Brandt, 1851; and P. latirostris Rathbun, 1902). The P. platyceros group appears to be most closely related to the genus Pandalopsis Bate, 1888, but Pandalus is retained as a possible paraphyletic group. Protandrous hermaphroditism is known in all but two species of the genus (P. curvatus and P. formosanus), for which only specimens of either male or female have been available. Pandalus propinqvus G. O. Sars, 1870, is transferred to a new monotypic genus Atlantopandalus, because of its lack of hermaphroditism and possession of some unique morphological characters, including one indicating a close relationsip to Dichelopandalus Caullery, 1896. All species are fully described and illustrated. The affinities and important morphological variations of the species are discussed. A key for adults is presented for the identification of the species. Biogeography of the genus is briefly discussed. [ABSTRACT FROM AUTHOR]