Laevigatus Research Articles

Slow and steady hurts the crab: Effects of chronic and acute microplastic exposures on a filter feeder crab.

Microplastics are a widespread environmental contaminant. Although detrimental effects on aquatic organisms are well documented, little is known about the long-term effects of microplastic exposure to filter-feeding organisms at ecologically realistic levels. This study investigates the effects of environmentally relevant concentrations of polyethylene micro beads ranging in size from 3 to 30 μm, on the physiology and energetics of a coastal filter-feeding crab Petrolisthes laevigatus. We evaluated the impact of microplastics by exposing P. laevigatus to two different concentrations and exposure times: i) a chronic exposure for five months at 250 particles L-1, and ii) an acute exposure for 48 h at 20,800 particles L-1, ~80 times higher than the chronic exposure. The results showed that only chronic exposures elicited negative effects on the coastal crab in both, metabolic and physiological parameters. Our findings demonstrate a strong correlation between the ingestion rate and weight loss, even at low concentrations, the crabs exhibited severe nutritional damage as a result of long-term microplastic exposure. By contrast, acute exposure revealed no significant effects to the crabs, a possible explanation for this being short-term compensatory responses. These results suggest that environmentally relevant concentrations of microplastics are harmful to marine organisms, and they should be evaluated during realistic temporal scales, as their effects strongly dependent on the exposure time. Our results also suggest that the effects of microplastics have been likely underestimated to date, due to the dominance of short-term exposures (acute) reported in the current literature.

How does emersion time affect embryos of coastal marine invertebrate species? Biochemical responses of three porcelain crabs from the Southeastern Pacific

AbstractPorcelain crabs that inhabit contrasting environments along the Southeastern Pacific coast have developed physiological adaptive responses to the harsh environmental conditions. However, it is not yet known if these responses are already present in early life stages, in embryos, for example, which are more vulnerable to environmental fluctuations than adults. In this study, we subjected ovigerous female crabs of three crab species (Allopetrolisthes punctatus, Petrolisthes laevigatus, and Petrolisthes violaceus) to different periods of emersion (0, 1, 3, and 5 hr) to measure the weight and biochemical parameters (i.e., glucose and lactate) in their embryos after a period of stress induction through emersion. The results indicate that after five hours of emersion, P. laevigatus' embryos had the highest dry weight. This same trend was observed in the embryos of P. violaceus. Allopetrolisthes punctatus' embryos had the lowest weight. The embryos' glucose content in P. laevigatus and P. violaceus was consumed during the emersion time, while in embryos of A. punctatus it remained relatively constant. The highest glucose content was reported in P. laevigatus, followed by P. violaceus and A. punctatus. The lactate content showed an opposite trend and was gradually accumulated with increasing emersion time. Petrolisthes laevigatus had the highest lactate content. This study reveals that the early ontogeny of these porcelain crabs is well adapted to long periods of emersion, showing biochemical adaptive responses linked to aerobic metabolism. These adaptations could reflect a distinctive physiological trait, explaining why porcelain crabs are able to survive in contrasting conditions.

The cascade of effects caused by emersion during early ontogeny in porcelain crabs of the Southeast Pacific coast: Biochemical responses of offspring

Petrolisthes crabs inhabit a wide range of coastal environments, from the upper intertidal to the subtidal, experiencing regular changes in pH, salinity, and temperature. Hence, such subtidal and intertidal invertebrates are likely to show physiological and biochemical adaptive responses in order to successfully develop during early ontogenetic stages and thus reach reproduction. We herein evaluated the biochemical responses to contrasting environmental conditions of the early ontogenetic stages of two coastal crabs from the Southeast Pacific coast: Petrolisthes laevigatus and Allopetrolisthes punctatus. For this purpose, stage I embryos of both species were subjected to two treatments: (1) emersion (i.e., a daily 3 h aerial exposure until the zoeas hatched) and (2) immersion (i.e., uninterrupted underwater submersion until the zoeas hatched); the total contents of glucose, proteins, lipids, and fatty acids of the organisms were measured in stage I embryos and recently hatched zoeas in order to assess the biochemical constitution of the two species. Both species showed changes in their energetic reserves when treatments within species were compared. Our results found that A. punctatus was negatively affected by stressful periods of emersion, while P. laevigatus showed the opposite tendency and was affected by periods of immersion. The sensitivity of the response and the contrasting outcomes for these two crabs underpin the fact that changes in environmental conditions along the Chilean coast due to climate change (e.g., increased anoxic coastal waters) may have significantly negative consequences on the populations of these ecologically important species and the associated taxa within their ecosystems.

Age dependent physiological tolerances explain population dynamics and distribution in the intertidal zone: A study with porcelain crabs

Population dynamics and their response to environmental stressors have been widely studied in intertidal organisms. However, how these dynamics and responses change with animal age have been largely ignored to date. Traditionally, it is assumed that younger organisms are more sensitive than adults to environmental stressors; under this perspective it could be predicted that fully grown organisms should be able to occupy the harsh upper limit of their intertidal habitat. However, in some intertidal Porcelain crabs the opposite distribution has been observed. Using Petrolisthes laevigatus, we tested the physiological tolerance of crabs of different sizes (i.e. age) and evaluated how this trait shapes population dynamics (distribution and small-scale migrations under different weather conditions). We determined the abundance and size distribution of P. laevigatus at the middle and upper intertidal levels during sunny and rainy days, finding that abundances decreased drastically and size distribution shifted to smaller individuals on rainy days. In the laboratory, survival and behavioural responses of individuals in water at 5, 10, 15 and 33 PSU salinities were evaluated. Young crabs were found in higher proportion in the upper intertidal while fully grown crabs (i.e. adults) mainly occupied the middle intertidal zone. Young crabs had a higher osmoregulatory capacity than adults, as they were better at regulating passive water uptake when challenged with diluted seawater. This was also correlated with a lower lethal salinity LC50 in young crabs compared to adults. Behavioural trials showed that young crabs performed better escaping in both water and air, at intermediate and reduced salinities than adults. Therefore, weather influences small scale migrations from the upper to the lower intertidal zone, and this migration is also age-dependent, with younger crabs being more tolerant to low salinities and therefore allowing them to remain in the upper intertidal zone during raniny days.

Variation in consumer pressure along 2500 km in a major upwelling system: crab predators are more important at higher latitudes

Consumer pressure in benthic communities is predicted to be higher at low than at high latitudes, but support for this pattern has been ambiguous, especially for herbivory. To understand large-scale variation in biotic interactions, we quantify consumption (predation and herbivory) along 2500 km of the Chilean coast (19°S–42°S). We deployed tethering assays at ten sites with three different baits: the crab Petrolisthes laevigatus as living prey for predators, dried squid as dead prey for predators/scavengers, and the kelp Lessonia spp. for herbivores. Underwater videos were used to characterize the consumer community and identify those species consuming baits. The species composition of consumers, frequency of occurrence, and maximum abundance (MaxN) of crustaceans and the blenniid fish Scartichthys spp. varied across sites. Consumption of P. laevigatus and kelp did not vary with latitude, while squid baits were consumed more quickly at mid and high latitudes. This is likely explained by the increased occurrence of predatory crabs, which was positively correlated with consumption of squidpops after 2 h. Crabs, rather than fish, were the principal consumers of squid baits (91% of all recorded predation events) at sites south of 30°S. Fish and crustaceans preyed in similar proportion on P. laevigatus, with most fish predation events at northern sites. The absence of any strong latitudinal patterns in consumption rate of tethered prey is likely due to redundancy among consumers across the latitudinal range, with crustaceans gaining in importance with increasing latitude, possibly replacing fish as key predators.

Coastal fish assemblages and predation pressure in northern-central Chilean Lessonia trabeculata kelp forests and barren grounds.

Kelp forests are declining in many parts of the globe, which can lead to the spreading of barren grounds. Increased abundances of grazers, mainly due to reduction of their predators, are among the causes of this development. Here, we compared the species richness (SR), frequency of occurrence (FO), and maximum abundance (MaxN) of predatory fish and their predation pressure between kelp forest and barren ground habitats of northern-central Chile. Sampling was done using baited underwater cameras with vertical and horizontal orientation. Two prey organisms were used as tethered baits, the black sea urchin Tetrapygus niger and the porcelanid crab Petrolisthes laevigatus. SR did not show major differences between habitats, while FO and MaxN were higher on barren grounds in vertical videos, with no major differences between habitats in horizontal videos. Predation pressure did not differ between habitats, but after 24 h consumption of porcelanid crabs was significantly higher than that of sea urchins. Scartichthys viridis/gigas was the main predator, accounting for 82% of the observed predation events on Petrolisthes laevigatus. Most of these attacks occurred on barren grounds. Scartichthys viridis/gigas was the only fish observed attacking (but not consuming) tethered sea urchins. High abundances of opportunistic predators (Scartichthys viridis/gigas) are probably related to low abundances of large predatory fishes. These results suggest that intense fishing activity on large predators, and their resulting low abundances, could result in low predation pressure on sea urchins, thereby contributing to the increase of T. niger abundances in subtidal rocky habitats.

Differences in the respiratory response to temperature and hypoxia across four life-stages of the intertidal porcelain crab Petrolisthes laevigatus

For aquatic breathers, hypoxia and warming can act synergistically causing a mismatch between oxygen supply (reduced by hypoxia) and oxygen demand (increased by warming). The vulnerability of these species to such interactive effects may differ during ontogeny due to differing gas exchange systems. This study examines respiratory responses to temperature and hypoxia across four life-stages of the intertidal porcelain crab Petrolisthes laevigatus. Eggs, megalopae, juveniles and adults were exposed to combinations of temperatures from 6 to 18 °C and oxygen tensions from 2 to 21 kPa. Metabolic rates differed strongly across life-stages which could be partly attributed to differences in body mass. However, eggs exhibited significantly lower metabolic rates than predicted for their body mass. For the other three stages, metabolic rates scaled with a mass exponent of 0.89. Mass scaling exponents were similar across all temperatures, but were significantly influenced by oxygen tension (the highest at 9 and 14 kPa, and the lowest at 2 kPa). Respiratory responses across gradients of oxygen tension were used to calculate the response to hypoxia, whereby eggs, megalopae and juveniles responded as oxyconformers and adults as oxyregulators. The thermal sensitivity of the metabolic rates (Q10) were dependent on the oxygen tension in megalopae, and also on the interaction between oxygen tension and temperature intervals in adults. Our results thus provide evidence on how the oxygen tension can modulate the mass dependence of metabolic rates and demonstrate changes in respiratory control from eggs to adults. In light of our results indicating that adults show a good capacity for maintaining metabolism independent of oxygen tension, our study highlights the importance of assessing responses to multiple stressors across different life-stages to determine how vulnerability to warming and hypoxia changes during development.

Interspecific variation in the physiological and reproductive parameters of porcelain crabs from the Southeastern Pacific coast: potential adaptation in contrasting marine environments

Porcelain crabs inhabit from upper intertidal to subtidal habitats. These environments are characterized by highly variable environmental conditions, which subject species found in these habitats to stress. In this study, we compared reproductive traits of mothers [i.e. fecundity, reproductive output (RO), dry weight, organic matter] and physiological parameters of their offspring (i.e. wet weight, water content, dry weight, organic matter, lactate content of embryos) of three species of porcelain crabs that inhabit the Southeastern Pacific: Petrolisthes laevigatus (upper intertidal); P. violaceus (low intertidal); Allopetrolisthes punctatus (subtidal). Overall, female P. laevigatus had lower fecundity (802 ± 115 vs. 4181 ± 1097 embryos) and amount of organic matter in their embryo masses (0.053 ± 0.006 vs. 0.27 ± 0.025 g) but higher RO values (1.34 ± 0.34 vs. 0.20 ± 0.07) than Allopetrolisthes punctatus. In addition, P. laevigatus embryos had higher organic matter content (81.09 ± 28.8 vs. 64.54 ± 6.1 μg), higher water content (188.6 ± 91.9 vs. 152.4 ± 30.8 μL) and higher lactate content (0.26 ± 0.04% vs. 0.07 ± 0.01% dry weight) than that found in A. punctatus embryos. Furthermore, females and embryos of P. violaceus showed low values and similar to those observed in P. laevigatus. As a potential strategy to increase survival of the offspring, P. laevigatus seems to invest a large portion of its energy in production of high quality embryos, despite costs to fecundity. This study reveals that porcelain crabs have physiological adaptations during their ontogeny that allow them to survive in fluctuating environments.

Toxicities of 26 pesticides against 10 biological control species

To determine selective effectiveness for specific pesticides on biological control species we evaluated the contact toxicity of 16 insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides. Targeted species included 3 predatory mites (Phytoseiulus persimilis Athias-Henriot, Amblyseius swirskii Athias-Henriot, and Neoseiulus californicus McGregor), 5 hymenopteran parasitoids (Diglyphus isaea Walker, Aphidius colemani Viereck, Encarsia formosa Gahan, Eretmocerus eremicus Rose and Zolnerowich and E. mundus Mercet), and 2 hemipteran predators (Orius laevigatus Fieber and Nesidiocoris tenuis Reuter) in laboratory condition. In addition, residual toxicity was evaluated on P. persimilis, E. formosa, and O. laevigatus. For contact toxicity, five insecticides (spinetoram, spinosad, lepimectin, chlorfenapyr, and dinotefuran+spinetoram) showed high toxicity to predatory mites. Most pesticides tested were highly toxic to all hymenopteran species except for D. isaea which showed low susceptibility to 11 pesticides. Bistrifluron+flubendiamide and B. valismortis were less toxic to A. colemani, and only B. valismortis was safe to both E. mundus and E. eremicus. Insect growth regulators (methoxyfenozide and bistrifluron), chlorantraniliprole, and bistrifuron+flubendiamide were not toxic to hemipteran predators. Fungicides and biopesticides were safe to hemipteran predators except for two biopesticides (B. subtilis and P. fluorescens). Most pesticides had low residual toxicity to P. persimilis, with the exception of chlorfenapyr whose toxicity persisted over 7days. One insecticide (cyantraniliprole), 2 acaricides (spiromesifen and fenpyroximate), 1 fungicide (metrafenone), and 4 biopesticides (B. subtilis, P. polymyxa, P. fluorescens, and B. valismortis) showed a much lower residual toxicity to E. formosa. Eight insecticides, 2 acaricides, 3 fungicides, and 5 biopesticides showed low residual toxicity to O. laevigatus.

Seasonal variation in dry weight and elemental composition of the early developmental stages of Petrolisthes laevigatus (Guérin, 1835) (Decapoda: Porcellanidae) in the Seno de Reloncaví, southern Chile

In the Seno de Reloncavi, southern Chile, seasonal changes in dry weight (DW) and elemental composition (CHN) were studied in embryo (initial embryonic stage), newly hatched zoeae, and newly settled megalopae of a porcelain crab, Petrolisthes laevigatus. Samples were taken throughout the seasons of egg laying (March-December), hatching (August-February), and settlement (October–February). Values of DW and CHN per embryo or larva, respectively, were consistently minimum in the middle of each season and maximum near its beginning and end. Patterns of seasonal variation in early embryonic biomass may thus be carried over to larvae at hatching and, possibly, to the settlement stage. Such carry-over effects may be selectively advantageous, as zoeae released at the beginning or near the end of the hatching season face conditions of poor planktonic food availability in combination with low winter temperatures or decreasing temperatures at the end of summer (enforcing long development duration). Hence, an enhanced female energy allocation into egg production may subsequently translate to enhanced yolk reserves remaining at hatching, allowing for a larval development under unfavourable winter conditions. In summer, by contrast, plankton productivity and temperatures are generally high, allowing for fast larval growth and development. This coincides with minimal biomass and energy contents both at hatching and settlement. In conclusion, our data suggest that seasonal patterns in the biomass of early developmental stages of P. laevigatus may reflect phenotypic variability as an adaptive response to predictable variations in environmental conditions, allowing this species to reproduce in temperate regions with marked seasonality in water temperature and plankton productivity.

Microhabitat segregation and physiological differences in two species of intertidal porcellanid crabs (Genus <i>Petrolisthes</i>) on the southern coast of Chile

Intertidal crustaceans have a high degree of physiological plasticity, which allows them to withstand periods of water emersion. In this study we examine the physiological constraints that determine the distribution and abundance of the intertidal porcellanid crabs Petrolisthes laevigatus and Petrolisthes violaceus . This study evaluates the distribution and abundance of the two species at different tidal heights, in relation to haemocyanin concentration and LDH activity, resistance to air desiccation, thermal tolerance, and resistance to hypoxic water. The results showed that Petrolisthes laevigatus was more abundant at the high tide level than Petrolisthes violaceus , which was more abundant at the low tide level. Petrolisthes laevigatus showed greater tolerance to high temperatures and lower tolerance to desiccation when exposed to air than P. violaceus , which was also more tolerant to hypoxia during prolonged exposure. No differences were found in haemocyanin concentration and LDH activity. These findings support the idea of an evolutionary gradient towards terrestrial adaptations. Of the two species, Petrolisthes laevigatus showed the most advanced physiological features for semi-terrestrial specialization.

UJI ANTIBAKTERI Lasianthus (RUBIACEAE) SEBAGAI TUMBUHAN BERKHASIAT OBAT DAN UPAYA PERBANYAKANNYA

Lasianthus, a member of the family Rubiaceae has potential for medicinal plants. The aims of the research were to find out the potential antibacterial activity of Lasianthus leaf extract and to investigate the effectiveness of plant propagation by stems cutting. The species tested were Lasianthus laevigatus Blume, L furcatus (Miq.) Bremek and L. cf. obscurus Blume. The extracted leaves in n-hexana, ethyl acetate and methanol were tested in vitro against Staphylococcus aureus and Escherichia coil activities that grown on medium of Mueller-Hinton agar. The methanol extracts of each plant material showed significant antibacterial activities on S. aureus and E. coll. Antibacterial activity increased with increasing concentration of the extracts. Plant propagation by stems cutting were done as a first step of conservation effort for respective species. Stems cutting of L. laevigatus, L. purpureus, L. furcatus, L. acuminatus, L rhinocerotis. and L. cf. obscurus with length of 10 cm were applied with Rotoon F to stimulate root growth. The result of plant propagation research showed that only the stems cutting of L. cf. obscurus grew well although roots did not grow until 4 months.

Seasonal variation in the nutritional vulnerability of first-stage larval porcelain crab, Petrolisthes laevigatus (Anomura: Porcellanidae) in southern Chile

In temperate marine environments, meroplanktonic larvae face seasonal variations in temperature and food availability. In a laboratory study conducted under seasonally varying temperature conditions, we evaluated the nutritional vulnerability in different cohorts (August, September, October, November, December, and January) of first-stage larvae of a porcellanid crab, Petrolisthes laevigatus. Besides continuously fed and starved control groups (FC, SC), the experimental treatments comprised: (1) differential periods of initial starvation and subsequent feeding (point-of-no-return, PNR: minimum time of initial starvation preventing recovery after later feeding); (2) initial feeding and subsequent starvation (point-of-reserve-saturation, PRS: minimum time of initial feeding allowing for food-independent development through the rest of the moulting cycle); (3) limited daily access to prey (feeding pulses, 4 and 6 h/day). The development time of FC larvae ranged from 10.6 ± 0.4 days (January) to 21.9 ± 2.6 days (August), without significant variation in mortality among cohorts. Under continuous absence of food (SC), first-stage larvae never survived to the zoea II. Short-term feeding pulses had significantly different effects on development time of different cohorts, but not on survival. The PNR was lowest in larvae produced near the end of spring (November). However, when the PNR was expressed as a percentage of the development time in FC larvae, no significant differences were found among cohorts (relative PNR: 32.8–42.5%). The relative PRS was reached after 60.6–73.5% of the development time in FC larvae. In spite of strong seasonal (presumably temperature-induced) differences in the absolute PNR and PRS values of different cohorts, the relative values were generally similar. This suggests that successive cohorts of early larvae can develop with similar success, unless severe winter conditions or oceanographic fluctuations cause a significant decline in short-term prey availability or plankton productivity. Due to long development duration at low temperatures, the larvae produced in winter and early spring have greater potential for dispersal, favoring a genetic exchange between distant populations and colonization of new habitats. Summer larvae, by contrast, may be more important for maintaining local populations. An index of nutritional vulnerability (NVI = PRS 50/PNR 50) is proposed in this paper to compare larvae with differential developmental times. In most larvae studied so far, the NVI is < 1, indicating some degree of independence of food. In larvae of P. laevigatus an index > 1 reflects a relatively high degree of dependence on planktonic food, especially in winter larvae.

Testing the abundant‐centre hypothesis using intertidal porcelain crabs along the Chilean coast: linking abundance and life‐history variation

AbstractAim The abundant‐centre hypothesis (ACH) is based on the assumption that physiological constraints limit populations at the edges of their distributional range, yet the geographical variation of physiological performance or life‐history traits has rarely been examined. Here we examine the applicability of the ACH in a marine system by testing whether physiological predictions are reflected in large‐scale variations of life‐history traits.Location The Chilean coast (18°–42° S), encompassing more than 2500 km along the Pacific coast of South America.Methods Five porcelain crab species (Petrolisthes granulosus, Petrolisthes laevigatus, Petrolisthes tuberculatus, Petrolisthes violaceus and Allopetrolisthes angulosus) were sampled on intertidal boulder beaches at 13 sampling sites. For each species and site we evaluated: (1) relative abundance (density), (2) maximum size, (3) size at maturity, (4) sex ratio, (5) proportion of ovigerous females, and (6) presence of recruits. The shape of the spatial distribution of each trait was evaluated statistically against the prediction of four hypothetical models (normal, ramped‐south, ramped‐north and abundant‐edge).Results The relative abundance and life‐history traits showed different spatial patterns among species. Relative abundance (across sites) was fitted by a normal model in only two species. No model fitted the spatial variation in body size and size at first maturity, which showed a slight but monotonic poleward increase in all species. Sex ratio showed a prominent hump‐shaped pattern, with females prevailing in the centre of the ranges and males dominating towards the range boundaries; this pattern was statistically significant in three of the five studied species. The proportion of ovigerous females showed no clear latitudinal trends, and mature individuals were observed across most of the geographical range of the species. However, recruits tended to be absent towards the southern (poleward) boundaries of the distribution.Main conclusions The ACH does not apply to all species equally. The link between abundance and life‐history traits is complex and variable among the porcelain crab species studied. Overall, the observed patterns were consistent with the idea that equatorward boundaries might be controlled by physiological restrictions mainly affecting adult survival, whereas poleward boundaries might be shaped by limitations in reproductive output and larval survival. Our results underline the importance of incorporating ecological, physiological and life‐history studies in future tests of the ACH.

Efecto del EDTA sobre la toxicidad del cromo (VI) en el desarrollo larval de Petrolisthes laevigatus (Guérin, 1835)

The larval development and growth of Petrolisthes laevigatus were analyzed in five concentrations of Cr VI, 0 (control), 0.25, 0.5, 1, and 5 mg L -1 chrome (VI) in filtered sea water and the same chrome (VI) concentrations, plus 0.7 mg L -1 EDTA. Analyses were done during 21-day period. Measurement of total length, individual wet average larvae weight and the presence or absence of deformations in P. laevigatus larvae were determined. The larvae of the control group (0 mg L -1 chrome (VI)) did not exhibit deformations and developed normally. The total length and biomass of the larvae exposed to Cr VI were significantly lower than those of the larvae subjected to Cr VI plus EDTA concentrations and the control larvae. It is hereby confirmed that the presence of EDTA in the medium mitigates the negative effects of Cr VI via a yet unknown mechanism.

Assessment of EDTA in Chromium (III–VI) Toxicity on Marine Intertidal Crab (Petrolisthes laevigatus)

Chromium poses a potential threat to coastal ecosystems. We used standard toxicity bioassays (semi-static, chronic) to evaluate EDTA as a chelating agent for reducing trivalent and hexavalent chromium toxicity on Petrolisthes laevigatus. Crab survival decreased linearly with increased chromium concentrations and dropped significantly beginning at 40 mg/L Cr (VI) and 80 mg/L Cr (III). No significant differences were observed with Cr (III) + EDTA as compared with untreated controls. Cr (VI) toxicity was greater than that of Cr (III), with low individual survival rates. The protective effect of EDTA in the medium increased crab survival by 41%-48%.

Effect of autotomy and regeneration of the chelipeds on growth and development in Petrolisthes laevigatus (Guérin, 1835) (Decapoda, Anomura, Porcellanidae)

The capacity to discard and regenerate limbs under conditions of vital risk does increase the probability of survival. Eventually, however, this can negatively influence the performance of other aspects of fitness in the organism affected. The influence of autotomy and regeneration of one or both chelipeds on body growth and intermoult period in Petrolisthes laevigatus was studied; individuals in a broad range of sizes were captured and subjected to autotomy treatments in one or both chelipeds, contrasted against a control group without autotomy. Body growth was measured as the increment of the carapace width after a moulting event. At the same time, the duration of the intermoult was considered as the period of time between two succesive moults. Significantly higher values of response in body growth, intermoult duration, and growth rate were observed in the control group with respect to the group with autotomy treatments. In the growth responses, the phenomenon of suboptimal foraging can be discarded and therefore the more probable explanation for growth decrease is related to reduction of the intermoult period or for changes in the allocation of energy from overall growth processes into the limb regeneration process.

Reproductive biology and population parameters of Petrolisthes laevigatus (Anomura: Porcellanidae) in southern Chile: consequences on recruitment

The present study describes the reproductive cycle and population structure of the intertidal crab Petrolisthes laevigatus, an abundant inhabitant of the upper rocky intertidal zone, as well as the relationship between seasonal patterns in the release of its planktonic larvae and recruiting. A total of 22900 individuals was collected along the coast of southern Chile between May 2001 and March 2003.The structure and density of the adult population (males and females) was relatively constant throughout the study period, although seasonal variations were observed in these two parameters of the benthic population (males, females, juveniles and megalopae), principally due to the incorporation of new individuals (recruitment) into the intertidal zone. Petrolisthes laevigatus presented a prolonged reproductive period. Females with initial eggs were present from the end of summer through to the middle of the following summer (11 months) and the breeding season lasted seven months (from August to February), as reflected in the six months of intertidal settlement (October–March).The interannual patterns and variations observed in the settlement along the southern Chilean coastline were related to the patterns in the abundance of potential released planktonic larvae. Petrolisthes laevigatus, unlike most temperate species, has a broad reproductive and settlement period in the south of Chile, which allows a highly stable structure and population abundance in this intertidal zone.

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.

AEROBIC RESPIRATION RATE AND ANAEROBIC ENZYMATIC ACTIVITY OF PETROLISTHES LAEVIGATUS (ANOMURA, PORCELLANIDAE) UNDER LABORATORY CONDITIONS

Abstract Petrolisthes laevigatus is commonly found in the intertidal zone from southern Peru to southern Chile. Its geographic distribution and its location in the intertidal zone suggest that this species should have ample physiological and biochemical adaptability to environmental change. Several experiments were conducted on P. laevigatus specimens collected in south-central Chile (Coliumo Bay) to determine: (i) the relationship between specific oxygen consumption rate and temperature; (ii) the presence and activity of lactate dehydrogenase (LDH), octopine dehydrogenase (OPDH), strombine dehydrogenase (STRDH), alanopine dehydrogenase (ALPDH), and alcohol dehydrogenase (ADH); and (iii) resistance to hypoxic conditions in sea water. The specific respiration rate at temperatures frequently found in Coliumo Bay was 0.054 and 0.058 ml O2h−1g−1 at 10.5°C and 13°C, respectively. LDH and OPDH activities were found in muscle tissue, heart, and visceral mass (midgut gland, gonad); OPDH presented a lower activity...