Spatial distribution patterns of the gorgonians <Emphasis Type="Italic">Eunicella singularis</Emphasis>, <Emphasis Type="Italic">Paramuricea clavata</Emphasis>, and <Emphasis Type="Italic">Leptogorgia sarmentosa</Emphasis> (Cape of Creus,Northwestern Mediterranean Sea)

Most of the current knowledge on Mediterranean gorgonians is restricted to investigations of those populations found within shallow sublittoral waters, and only limited data are available for populations located below scuba depth. To overcome this lack of information, the occurrence and abundance of the gorgonians Eunicella singularis, Paramuricea clavata, and Leptogorgia sarmentosa were investigated in northwestern Mediterranean benthic communities over a wide geographical (60 km of coastline) and bathymetrical (0–70 m deep) extent using a remotely operated vehicle (ROV). The greatest occurrence and abundances of E. singularis and P. clavata were concentrated in areas that are directly exposed to strong near-bottom currents. E. singularis was the most common and abundant species and displayed great plasticity and amplitude in its environmental preferences. Conversely, P. clavata showed a very patchy distribution that was associated with vertical rocky walls. Only isolated colonies of L. sarmentosa were observed in the study area. Hot spots of abundance of E. singularis and P. clavata were identified below a depth of 40 m, which demonstrates the importance of studying the distribution of benthic species over a wide geographical and bathymetrical extent.     

Genetic evidence for the cryptic species pair, <Emphasis Type="Italic">Lottia digitalis </Emphasis>and <Emphasis Type="Italic">Lottia austrodigitalis</Emphasis> and microhabitat partitioning in sympatry

It has been proposed that the common West Coast limpet, Lottia digitalis, is actually the northern counterpart of a cryptic species duo including, Lottia austrodigitalis. Allele frequency differences between southern and northern populations at two polymorphic enzyme loci provided the basis for this claim. Due to lack of further evidence, L. austrodigitalis is still largely unrecognized in the literature. Seven additional enzyme loci were examined from populations in proposed zones of allopatry and sympatry to determine the existence of L. austrodigitalis as a sibling species to L. digitalis. Significant allele frequency differences were found at five enzyme loci between populations in Laguna Beach, southern California, and Bodega Bay, northern California; strongly supporting the existence of separate species. Both species exhibit two microhabitat morphotypes, a gooseneck barnacle morph in the mid-intertidal zone and a rock morph in the high-intertidal zone. In sympatry, L. austrodigitalis was more abundant higher in the intertidal on rocks, whereas L. digitalis was more abundant lower in the intertidal on barnacles. This finding supports earlier claims of microhabitat partitioning in this sibling species pair. In addition to this finding, the transition zone between the species was found to have shifted substantially northward in only two decades, from Monterey Peninsula, CA to near Pigeon Point, CA, where L. digitalis previously dominated.     

Temporal and spatial variation in protein,carbohydrate, and lipid levels in <Emphasis Type="Italic">Corallium rubrum</Emphasis> (Anthozoa,Octocorallia)

Red coral (Corallium rubrum) is an important component of the Mediterranean coralligenous habitat. The present study analyzes the relationship between energy storage molecule concentration (i.e. tissue balance of protein–carbohydrate–lipid levels) and the gonadal output in two populations located at different depths (16–18 m and 40–45 m depth) through a seasonal cycle (2002–2003). In June 2003, another six populations have been sampled to compare medium-scale geographical variation. The colonies sampled were less than 6 cm high, thus representing the majority of the population in the studied area. There was no clear relationship between energy storage (i.e. carbohydrate and lipid levels) and gonadal output, nor in the seasonal cycle or the spatial variation. A clear-cut seasonal trend of energy storage was detected only in the shallower population. The water temperature was warmer at 20 m depth and the water transparency (Secchi disk) was also higher (lower seston concentration) in 2003 when the same periods in 2002 and 2003 were compared (May–August). Carbohydrates seemed to be more sensitive to food constraints than lipids. The partial mortality detected in summer 2003 in the sampling area appeared to be recorded in the carbohydrate and lipid levels of this species, especially in the shallow population. The biochemical levels prove to be a useful tool to detect unusual environmental conditions that may cause partial or total mortality in benthic suspension feeders.     

Geographical subdivision,demographic history and gene flow in two sympatric species of intertidal snails, <Emphasis Type="Italic">Nerita scabricosta</Emphasis> and <Emphasis Type="Italic">Nerita funiculata</Emphasis>, from the tropical eastern Pacific

The patchy distribution of rocky intertidal communities in the tropical eastern Pacific (TEP) may impose severe constraints on the genetic connectivity among populations of marine invertebrates associated with this habitat. In this study, we analyzed a portion of the mitochondrial cytochrome c oxidase subunit I (COI) gene in two sympatric species of marine snails, Nerita scabricosta and Nerita funiculata, common inhabitants of the rocky intertidal from the Gulf of California (Sea of Cortez) and outer Pacific coast of the southern Baja California (Baja) peninsula to northern South America, to assess genetic connectivity among populations of each species. One of our aims was to determine whether the morphological, behavioral, and ecological differences observed among populations of both species throughout their range in the TEP corresponded to population genetic differences. In addition, we were interested in elucidating the demographic history of both species. We found no evidence of genetic structure throughout the Gulf of California and outer coast of the Baja peninsula region for either species. Comparisons between Gulf of California/Baja and Panama populations, however, showed significant genetic differentiation for N. scabricosta, but not for N. funiculata. The genetic differences between Mexican and Panamanian populations of N. scabricosta were consistent with previously reported ecological and behavioral differences for this species between these two distant regions. However, previously reported size differences between northern and central/southern Gulf of California individuals of N. scabricosta do not correspond with our findings of genetic connectivity among these populations. Results from neutrality tests (Tajima’s D and Fu’s F _S), the mismatch distribution, and Bayesian skyline analyses suggested that both species have experienced dramatic population expansions dating to the Pleistocene.     

Degree-day accumulation controlling allopatric and sympatric variations in the sociality of sweat bees, <Emphasis Type="Italic">Lasioglossum</Emphasis> (<Emphasis Type="Italic">Evylaeus</Emphasis>) <Emphasis Type="Italic">baleicum</Emphasis> (Hymenoptera: Halictidae)

Halictine bees exhibit a wide range of social behaviour that varies both inter- and intraspecifically. Although previous studies suggested that the intraspecific variation might be attributed to temperature differences, there was no direct evidence to detect the relationships between temperature and socialities. Lasioglossum (Evylaeus) baleicum exhibited solitary behaviour in a cooler locality (Kawakita) because of the shorter breeding season; in a warmer locality (Nishioka Park), however, this bee species exhibited eusociality at sunny site and solitary behaviour at shady site, whereas a molecular phylogeny confirms that all of these colonies are evidently conspecific. Therefore, we examined the effect of degree-day accumulation on the sympatric social variation of L. baleicum by rearing the bees to calculate the threshold temperature. Whereas they showed high mortality, the threshold temperature was estimated to be 10.33°C and the expected degree-day accumulation was 340 degree days. When we use this value of a degree-day accumulation to estimate the expected eclosion date, the estimated dates were always consistent with observed eclosion dates. In any sites where the bees were solitary, the degree-day accumulation was not enough for the second eclosion by the end of the bee-active season. In Nishioka Park, sex ratio of the first brood was female biased, and daughters were smaller than mothers; in Kawakita, however, there was no sex bias, and daughters were as large as their mothers indicating that the foundresses seem to produce gyne-sized females in Kawakita but worker-sized females in Nishioka though these females do not become workers at shady site.     

Population genetic structure of the stalked barnacle <Emphasis Type="Italic">Pollicipes pollicipes</Emphasis> (Gmelin, 1789) in the northeastern Atlantic: influence of coastal currents and mesoscale hydrographic structures

Within its distribution range in the northeastern Atlantic, the stalked barnacle Pollicipes pollicipes shows a well-defined pattern of genetic variation, comprising (a) a subtropical/temperate northern assemblage, made up of populations distributed between 47°N and 28°N along the French, Iberian, North African and Canary Islands coastlines, and (b) a single isolated and highly divergent tropical population in the Cape Verde Islands (16°N), at the southernmost limit of the species’ distribution. However, within the northern assemblage several populations show a level of genetic differentiation that allows rejection of the hypothesis of genetic homogeneity. The congruence observed between genetic and hydrographic patterns suggests a crucial role of hydrodynamics, and of the dispersal of the planktonic larvae, in the determination of population structure. Along the southern European Atlantic coast, the Iberian Poleward Current and mesoscale hydrographic structures are, respectively, facilitating gene flow at the regional level and genetic differentiation at the local level. On the Atlantic coast of North Africa, the homogenizing equatorward flow of the Canary Current does not extend as far as the Cape Verde Islands. A demographic expansion is dated to the late Pleistocene, preceding the Eemian interglacial, and is oldest in the case of the long-standing Cape Verde population, sustained by a stable tropical habitat. The divergence between the Cape Verde population and the remaining populations is thus ancient, and suggests that oceanic current patterns may constitute a generalized physical barrier to the dispersal of marine organisms between Cape Verde and the rest of Macaronesia.     

Genetic differentiation between morphotypes in the Antarctic limpet <Emphasis Type="Italic">Nacella concinna</Emphasis> as revealed by inter-simple sequence repeat markers

The limpet Nacella concinna (Strebel 1908) was the focus of numerous studies dealing with Antarctic benthos. One of the main characteristics of the species is the presence of two distinguishable morphotypes, one inhabiting the intertidal (during summer) and the other inhabiting the subtidal. For a long time these forms were considered as an expression of phenotypic plasticity, since previous studies did not found genetic differences between them. In the present work, we performed both a morphometric and a genetic differentiation analysis (using ISSR-PCR markers) of these two forms in three stations sampled at Potter Cove, South Shetland Islands. The results confirmed the morphological differences between intertidal and subtidal forms reported in other Antarctic localities. The genetic differences detected indicate that the two forms can be considered as genetically distinct populations maintaining low levels of gene flow. The degree of reproductive isolation of the ecotypes is discussed, as well as the possible origin of the divergence. The genetic differentiation observed can also have behavioral and physiological correlates, pointing out the importance of taking into account the potential differences in the response of both populations to different conditions in future studies in this species. M. C. de Aranzamendi and R. Sahade contributed equally to this paper.     

Molecular population structure of the kuruma shrimp <Emphasis Type="Italic">Penaeus</Emphasis><Emphasis Type="Italic"> japonicus</Emphasis> species complex in western Pacific

In a previous study on the kuruma shrimp Penaeus japonicus from the South China Sea, we detected high genetic divergence between two morphologically similar varieties (I and II) with distinct color banding patterns on the carapace, indicating the occurrence of cryptic species. In the present study, we clarify the geographical distribution of the two varieties in the western Pacific by investigating the genetic differentiation of the shrimp from ten localities. Two Mediterranean populations are also included for comparison. Based on the mitochondrial DNA sequence data, the shrimps are separated into two distinct clades representing the two varieties. Variety I comprises populations from Japan and China (including Taiwan), while variety II consists of populations from Southeast Asia (Vietnam, Singapore and the Philippines), Australia and the Mediterranean. Population differentiation is evident in variety II, as supported by restriction profiles of two mitochondrial markers and analysis of two microsatellite loci. The Australian population is genetically diverged from the others, whereas the Southeast Asian and Mediterranean populations show a close genetic relationship. Variety I does not occur in these three localities, while a small proportion of variety II is found along the northern coast of the South China Sea and Taiwan, which constitute the sympatric zone of the two varieties. The present study reveals high genetic diversity of P. japonicus. Further studies on the genetic structure of this species complex, particularly the populations in the Indian Ocean and Mediterranean, are needed not only to understand the evolutionary history of the shrimp, but also to improve the knowledge-based fishery management and aquaculture development programs of this important biological resource.     

Vocal signals,isolation and hybridization in the vinaceous dove (<Emphasis Type="Italic">Streptopelia vinacea</Emphasis>) and the ring-necked dove (<Emphasis Type="Italic">S. capicola</Emphasis>)

Two closely related dove species, Streptopelia vinacea and S. capicola, show clear interspecific divergence in one acoustic signal (perch-coo), but much less so in another (bow-coo). Both signals play a role in territorial defense and mate attraction and may thus convey information used for species recognition. In Uganda, there is a small zone of overlap where the two species most probably hybridize. With playback experiments in allopatric populations of each species we tested the potential of the two signal types for species isolation. Allopatric populations showed a stronger response to conspecific than to heterospecific perch-coos, but an equal response to bow-coos of either species. However, S. vinacea responded relatively stronger to S. capicola perch-coos than vice versa. The hybrid population showed an equal response to bow-coos of either species, but a marginally stronger response to perch-coos of S. capicola compared to perch-coos of S. vinacea. Hybrids have a variable and intermediate vocal structure compared to both parental species, which allowed for testing of behavioral coupling between production and perception of these signals. Hybrids showed no relationship between their coo structure and that of the species to which they respond most strongly, indicating a lack of behavioral coupling. Although perch-coos may differ sufficiently to allow species isolation, the similarity in bow-coos may allow interspecific interactions. We suggest that the similarity in bow-coos and the higher salience of S. capicola perch-coos may have allowed S. capicola to extend its range into that of S. vinacea, resulting in hybridization. Electronic Publication     

Molecular characterization of the zoanthid genus <Emphasis Type="Italic">Isaurus</Emphasis> (Anthozoa: Hexacorallia) and associated zooxanthellae (<Emphasis Type="Italic">Symbiodinium</Emphasis> spp.) from Japan

The zoanthid genus Isaurus (Anthozoa: Hexacorallia) is known from both the Indo-Pacific and Atlantic Oceans, but phylogenetic studies examining Isaurus using molecular markers have not yet been conducted. Here, two genes of markers [mitochondrial cytochrome oxidase subunit I (COI) and mitochondrial 16S ribosomal DNA (mt 16S rDNA)] from Isaurus specimens collected from southern Japan (n = 19) and western Australia (n = 3) were sequenced in order to investigate the molecular phylogenetic position of Isaurus within the order Zoantharia and the family Zoanthidae. Additionally, obtained sequences and morphological data (polyp size, mesentery numbers, mesogleal thickness) were utilized to examine Isaurus species diversity and morphological variation. By comparing our obtained sequences with the few previously acquired sequences of genera Isaurus as well as with Zoanthus, Acrozoanthus (both family Zoanthidae), and Palythoa spp. (family Spenophidae) sequences, the phylogenetic position of Isaurus as sister to Zoanthus within the Family Zoanthidae was suggested. Based on genetic data, Isaurus is most closely related to the genus Zoanthus. Despite considerable morphological variation (in particular, polyp length, mesentery numbers, external coloration) between collected Isaurus specimens, all specimens examined are apparently conspecific or very closely related based on molecular data and observed morphological variation within colonies. Additionally, obtained internal transcribed spacer of ribosomal DNA (ITS-rDNA) sequences from symbiotic zooxanthellae (Symbiodinium spp.) from all Isaurus specimens were shown to be subclade C1-related Symbiodinium. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mate preferences in <Emphasis Type="Italic">Drosophila</Emphasis> infected with <Emphasis Type="Italic">Wolbachia</Emphasis>?

The maternally inherited bacterium Wolbachia pipientis generates strong reproductive incompatibilities between uninfected females and infected males (cytoplasmic incompatibility), significantly reducing both female and male reproductive success. Such fitness costs are thought to place selective pressure on hosts to evolve pre-copulatory preferences for mating with compatible mates, thereby enabling them to avoid the reproductive incompatibilities associated with Wolbachia. Therefore, uninfected females are predicted to prefer mating with uninfected males, whereas infected males are predicted to prefer mating with infected females. Despite these predictions, previous investigations of pre-copulatory mate preferences in Wolbachia-manipulated Drosophila have not found evidence of female preference for uninfected or compatible males. However, none of these studies utilised a design where focal individuals are provided with a simple choice in a relatively non-competitive situation. We examined both female and male pre-copulatory mate preference based on mate infection status in Drosophila simulans and D. melanogaster using simple choice assays involving between 30–50 replicates per treatment. Although we found no evidence of female pre-copulatory mate preferences in either species, male D. simulans exhibited some preference for mating with females of the same infection status. However, this preference was not evident when we repeated the experiment to confirm this finding. Consequently, we conclude that neither male nor female D. melanogaster and D. simulans exhibit significant Wolbachia-associated pre-copulatory mate preferences.     

Genetic structuring of <Emphasis Type="Italic">Latris lineata</Emphasis> at localized and transoceanic scales

Striped trumpeter (Latris lineata) is a demersal teleost distributed around the temperate clines of all the major oceans in the southern hemisphere. Within Tasmanian waters the species is managed as a single stock, although no studies have been performed to confirm genetic panmixia. A protracted pelagic larval phase and a recent transoceanic tag recapture of an adult fish suggest significant potential for genetic mixing between widely separated populations. Phylogenetic analysis of mitochondrial DNA control region sequences suggested no genetic mixing between Tasmania, New Zealand and St Paul/Amsterdam Islands, evidence for the first time that there is population structure at a transoceanic scale for this species. In addition, an analysis of molecular variance coupled with phylogenetic analyses suggested no significant structuring of striped trumpeter from three locations around Tasmania. The information provided in this study is useful for the design of modern fisheries management techniques such as spatially implemented marine reserves. In addition, species-by-species knowledge about population structures of marine species facilitates ecologically useful generalizations concerning their population dynamics and key issues on the broader ecology of the oceans.     

Sympatry in grapsoid crabs (genera <Emphasis Type="Italic">Planes</Emphasis> and <Emphasis Type="Italic">Plagusia</Emphasis>) from olive ridley sea turtles (<Emphasis Type="Italic">Lepidochelys olivacea</Emphasis>), with descriptions of crab diets and masticatory structures

Grapsoid crabs of the genera Planes and Plagusia are commonly referred to as “rafting crabs” due to their propensity to live on flotsam and pelagic marine animals. Planes minutus and Planes major (=Planes cyaneus) are epibionts of sea turtles. Occurrences of grapsoid crabs in the genera Planes and Plagusia were evaluated on a total of 27 olive ridley sea turtles, Lepidochelys olivacea, from the eastern tropic Pacific (1998–2001) and the Hawaiian Islands (2002) captured in July–December each year. This is the first report of Planes marinus and Plagusia squamosa on sea turtles, and of P. major, P. marinus, and P. squamosa in sympatry on a confined substrate. Stomach content analyses showed P. major and P. marinus consumed a variety of neuston and marine vegetation, with the former consuming considerably more animal material. Epibiotic P. squamosa consumed mostly plant material. The three Planes species had distinctive differences in gastric mill tooth morphology. The versatile mouthparts of P. marinus are described and resemble those of their congeners. Most female P. major and P. marinus collected were ovigerous and present in all survey months.     

Monitoring acoustically tagged king prawns <Emphasis Type="Italic">Penaeus</Emphasis> (<Emphasis Type="Italic">Melicertus</Emphasis>) <Emphasis Type="Italic">plebejus</Emphasis> in an estuarine lagoon

Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use, foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April–12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged 2,654.1 ± 502.0 and 379.9 ± 103.9 m², respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different habitats.     

A spatial gradient in the potential reproductive output of the sea mussel <Emphasis Type="Italic">Mytilus californianus</Emphasis>

Spatial variation in reproductive output from different populations within a region could have important consequences for recruitment, and cascading effects on populations and communities of marine species, but is rarely examined over meso-scales (i.e., tens to hundreds of kilometers). In this study, reproduction in the dominant mid-intertidal mussel, Mytilus californianus, was examined from sites spanning Point Conception, California over a 6-month period (March–August 2000). There was a dramatic geographic pattern in the relationship between size and potential reproductive output that was qualitatively similar across all 6 months sampled. Increases in allocation to reproductive tissue with increasing body size occurred at all sites, but the slope nearly doubled at sites south of Point Conception compared to northern sites. The spatial variation in size-specific reproductive output, coupled with additional spatial gradients in mussel density and size distributions, combined to increase total reproductive output by over eightfold at southern relative to northern sites. This study highlights the need to explicitly examine spatial patterns of reproductive output at these meso-scales, in order to better understand connectivity and source–sink dynamics in marine systems.     

Cardiac output during exposure to <Emphasis Type="Italic">Chattonella</Emphasis><Emphasis Type="Italic">marina</Emphasis> and environmental hypoxia in yellowtail (<Emphasis Type="Italic">Seriola</Emphasis><Emphasis Type="Italic">quinqueradiata</Emphasis>)

The experiments were undertaken to measure, for the first time, cardiac output in yellowtail (Seriola quinqueradiata) during exposure to a harmful red tide flagellate (Chattonella marina). The responses were compared with those during exposure to environmental hypoxia to evaluate the significance of the drop of arterial oxygen partial pressure (PaO₂) in the fish-kill mechanisms by C. marina. PaO₂ immediately decreased, whereas heart rate (HR) was maintained until shortly before death during exposure to C. marina. Suffocation developing during the exposure resulted from a decrease in blood oxygen content, but not from lowered blood flow to the tissue. Although exposure to both C. marina and hypoxia immediately decreased PaO₂, arterial oxygen content (CaO₂) and pH (pHa) were significantly lower, whereas HR and cardiac output (&Qdot;) remained significantly higher, for the C. marina-exposed fish than for hypoxia-exposed fish. Although the drop in PaO₂ appears to play a pivotal role in the mechanisms of fish death by C. marina, other physiological response(s) should also be considered.     

Phylogeography of two species of <Emphasis Type="Italic">Lysidice</Emphasis> (Polychaeta,Eunicidae) associated to the seagrass <Emphasis Type="Italic">Posidonia oceanica</Emphasis> in the Mediterranean Sea

The aim of this work was to define the phylogeographic patterns of the two species of polychaete Eunicidae, Lysidice ninetta Audouin and Milne Edwards and Lysidice collaris Grube, both associated as sheath borers to the Mediterranean seagrass Posidonia oceanica, and with reference to their different origin and their actual geographic distribution. L. ninetta is distributed in the Atlantic and in the Mediterranean Sea while L. collaris is a tropical species, whose introduction into the Mediterranean Sea through the Suez Canal (lessepsian migrant) has been hypothesized in recent years. The two species have been often confused in the past, although they appear morphologically distinct. They share the same microhabitat (Posidonia sheaths) and they co-exist along a broad bathymetric range (1–30 m). Several populations for both taxa were sampled all along the coast of the Mediterranean basin. A variable no coding region of nuclear DNA (rDNA, ITS1) and a portion of a more conservative coding region of mitochondrial DNA (sub-unit one of citochrome oxidase, COI) were used as molecular markers. Both markers confirmed the separation between the two species. Low intraspecific polymorphism was present in L. collaris, together with absence of phylogeographic structure. In L. ninetta, instead, the presence of intraspecific cryptic lineages, sympatric in some sites, was recorded. Clustering of single populations in the two main clades was not always consistent between markers. The mitochondrial COI region showed more resolution at the given spatial scale. Our results suggest that Lysidice collaris could be recently introduced into the Mediterranean Sea from one or more separate events. On the other hand, for L. ninetta one could presume a re-colonization of the Mediterranean basin from the Atlantics, after the Messinian crisis (dry-out of the Mediterranean Sea, 5.5 my) with the subsequent separation of intraspecific lineages. The phylogeographic patterns of both Lysidice spp. are disjoined with respect to that of the host plant, P. oceanica. The obtained results suggest that environmental constraints and evolutionary history of these polychaetes and their host plant act in different ways to determine their actual genetic spatial structure.     

The effect of salinity on survival,bioenergetics and predation risk in the mud crabs <Emphasis Type="Italic">Panopeus simpsoni</Emphasis> and <Emphasis Type="Italic">Eurypanopeus depressus</Emphasis>

The effect of salinity on survival, bioenergetics and predation risk was studied in two common mud crabs in the Gulf of Mexico, Eurypanopeus depressus and Panopeus simpsoni. Eurypanopeus survived better at low salinities (the 28-day LC₅₀ of E. depressus was 0.19 PSU compared with 6.97 PSU for P. simpsoni). While low salinity increased energy expenditure and reduced food consumption and absorption, resulting in lower scope for growth, identical responses to salinity occurred in both species. Both species also had similar salinity-dependent patterns of hyper-osmoregulation. Because these physiological mechanisms could not explain differences between the two species in salinity tolerance, we explored the effect of salinity on competition for refugia. Eurypanopeus had higher resource holding potential for refugia, especially at low salinity. As a consequence it had lower predation risk to blue crabs in laboratory experiments. The higher tolerance by E. depressus for low salinities, and greater resource holding potential for refugia may explain why it has a more euryhaline distribution than P. simpsoni.     

Altered c-Fos expression demonstrates neuronal stress in mummichog, <Emphasis Type="Italic">Fundulus heteroclitus</Emphasis>, exposed to <Emphasis Type="Italic">Pfiesteria shumwayae</Emphasis> and <Emphasis Type="Italic">Chaetoceros concavicornis</Emphasis>

To better understand sublethal effects of harmful algal blooms (HABs) on fish, mummichog, Fundulus heteroclitus (L.), were exposed in the laboratory to varying, environmentally relevant densities of Pfiesteria shumwayae (Glasgow et Burkholder, CCMP 2089, dinoflagellate) and Chaetoceros concavicornis (Mangin, CCMP 169, diatom). Two experiments were conducted during the spring of 2003 and 2004 to quantitatively examine the effects of acute (2 h) P. shumwayae and C. concavicornis algal exposure on mummichog brain activity using c-Fos expression as a marker of altered neuronal activity. Brains from HAB-exposed fish were removed, sectioned, and stained using immunocytochemistry prior to quantifying neuronal c-Fos expression. Fish exposed to P. shumwayae and C. concavicornis showed increased c-Fos expression compared to unexposed control fish. A significant dose-response relationship was observed, with increased labeling in brains of fish exposed to higher cell densities for both HAB species tested (P ≤ 0.01). Increased labeling was found in the telencephalon, optic lobes, midbrain, and portions of the medulla. The greatest increases in expression were observed in the telencephalon of P. shumwayae-exposed fish, and in the telencephalon and optic lobes of C. concavicornis-exposed fish (P ≤ 0.01). These increases in c-Fos expression are consistent with other physical and chemical stress exposures observed in fish. Neuronal stress, evidenced by c-Fos expression, demonstrates a sublethal effect of exposure and changes in brain activity in fish exposed to HAB species.     

Lack of sequestration of host plant glucosinolates in <Emphasis Type="Italic">Pieris rapae</Emphasis> and <Emphasis Type="Italic">P. grarricae</Emphasis>

Summary. Sequestration of plant toxins in herbivores is often correlated with aposematic coloration and gregarious behaviour. Larvae of Pieris brassicae show these conspicuous morphological and behavioural characteristics and were thus suggested to sequester glucosinolates that are characteristic secondary metabolites of their host plants. P. rapaeare camouflaged and solitary, and are thus not expected to sequester. To test this hypothesis and to check the repeatabi-lity of a study that did report the presence of the glucosinolate sinigrin in P. brassicae, larvae were reared on three species of Brassicaceae (Sinapis alba, Brassica nigra and Barbarea stricta), and different leaf and insect samples were taken for glucosinolate analysis. The major host plant glucosinolates could only be found in traces or not at all in larval haemolymph, bled or starved larvae, faeces or pupae of both species or P. brassicae regurgitant. Haemolymph of both Pieris spp. was not rejected by the ant Myrmica rubra in dual-choice assays; the regurgitant of P. brassicae was rejected. This suggests the presence of compounds other than glucosinolates that might be sequestered in or produced by P. brassicae only. In faeces of both Pieris spp. a compound which yielded 4-hydroxybenzylcyanide (HBC) upon incubation with sulfatase was detected in high concentrations when larvae had been reared on S. alba. This compound may be derived from hydrolysis of sinalbin, the main glucosinolate of that plant. The unidentified HBC progenitor was apparently not sequestered in the two Pieris spp., and was not detected in faeces of larvae reared on B. nigra or B. stricta. Received 18 July 2002; accepted 11 September 2002.