Southern King Crab Lithodes Santolla Research Articles

Trawl-related mortality and injuries to the southern king crab Lithodes santolla of Patagonia

The catch and discard of non-target species could have detrimental effects on bycatch, species due, among others, to the increase in mortality and prevalence of injuries. In Argentina, the southern king crab (SKC), Lithodes santolla, supports a profitable trap fishery but is also caught as bycatch in trawl fisheries. The aims of this work were: i) to quantify the mortality and injuries in SKC caught as bycatch in the hake fishery in San Jorge Gulf (southwestern Atlantic Ocean), ii) to assess the factors that affect their mortality and injury occurrence, and iii) to estimate their postdiscard mortality.Immediate mortality (IM) and injuries in SKC were recorded in hauls of the hake fishery, and then related to operational and biological variables. SKC vitality was assessed using the reflex action mortality predictor (RAMP) test. Postdiscard mortality was analyzed in aquaria and wild (sea cages) conditions. The IM of SKC in the common hake fishery was 31%. The IM, as well as increased injuries and decreased vitality, were directly associated with the time and conditions of air exposure. Both the IM and injury occurrence were also affected by biological variables such as the sex,size and molt stage. Postdiscard mortality was lower in wild conditions than in the aquaria (1%). Our results suggest that SKC could have high resistance to handling and high recovery capacity after its return to the sea. In consequence, the quick return of SKC to the sea may have a positive effect on SKC survival.

Podocoryna tenuis (Hydrozoa) in temperate waters of the southwestern Atlantic: additional data on life cycle stages support its synonym with Podocoryna humilis

Two species of Hydractiniidae (Hydrozoa) with metagenetic life cycle have been recorded for the temperate region of the southwestern Atlantic Ocean: the medusa stage of Podocoryna tenuis and the polyp stage of P. humilis. Both the adult medusa of P. humilis and the polyp stage of P. tenuis are unknown, but it is possible that they are different stages of the same species, a hypothesis still to be tested. Colonies of P. humilis growing on the southern king crab Lithodes santolla collected at the Atlantic Patagonian coast, and two small medusae released from these hydroid colonies were analyzed. Medusa of P. humilis were kept alive for 3 days and they were morphologically compared with the medusae of P. tenuis sorted out from ~ 2,500 plankton samples along the Atlantic Patagonian coast. The study of these specimens allowed reassessing the taxonomic status of P. humilis and P. tenuis from the southwestern Atlantic Ocean. Polyp and young medusa stages of P. humilis were described, and additional information was recovered to better describe the medusa stage of P. tenuis. New morphologic and biogeographic evidences in order to propose the synonymy between P. tenuis and P. humilis were discussed.

Trophic Niche Dynamics and Diet Partitioning of King Crab Lithodes santolla in Chile’s Sub-Antarctic Water

The southern king crab Lithodes santolla is one of the most economically important fishery species in the southern waters of the Atlantic and Pacific Oceans. A combination of stomach content and stable isotope analyses was used to reveal the potential dietary characteristics, isotopic niche, overlap among maturity stages and sexes, and trophic relationships of an L. santolla population in the Nassau Bay, Cape Horn region. Stable isotope analyses indicated that L. santolla assimilated energy from a basal carbon source, the giant kelp Macrocystis pyrifera, forming the trophic baseline of the benthic food web. Moreover, the trophic position of L. santolla varied among late juveniles and adults, suggesting that the southern king crab does undergo an ontogenetic diet shift. L. santolla exhibited intraspecific isotopic niche variation, reflecting niche differentiation which allows the species to partition resources. The trophic relationships of L. santolla with the associated fauna suggested some potential interactions for food resources/habitat use when they are limited. This study is the first attempt to characterize the trophic dynamics of the southern king crab in the Cape Horn area and, by generating more data, contributes to the conservation of the king crab population and the long-term management of local fisheries that rely on this resource.

Differences in the timing of egg extrusion and reproductive investment between primiparous and multiparous females of the southern king crab Lithodes santolla

ABSTRACT This study analysed differences in the timing of egg extrusion, reproductive investment and spatial distribution between primiparous and multiparous females of the southern king crab (SKC) Lithodes santolla. Early publications had reported that, in the San Jorge Gulf (SJG; 45–47°S), Argentina, SKCs mated annually, mainly in December. In this work, in coastal areas of SJG, we found small females in postmoult with recently extruded eggs in September–October. At the same time, one SKC female fraction was in intermoult with eggs close to hatching. Evidence suggests that females with recently extruded eggs were primiparous, while females with eggs close to hatching were multiparous. Primiparous females were less fecund than multiparous females of the same size, but no differences were found in the egg dry mass between these female fractions. The size-frequency distribution observed suggests a spatial segregation between primiparous and multiparous females, with the former being concentrated in the coastal areas of SJG. Differences in reproductive traits between primiparous and multiparous females have been widely reported in crab species with determinate growth, but rarely in crabs with indeterminate growth as lithodids.

Differential reproductive investment in females of <em>Lithodes santolla</em> (Decapoda: Anomura) from different regions of southern South America

The southern king crab Lithodes santolla experiences low temperatures and unpredictable food conditions, and is under variable fishing pressure. To compare the reproductive investment of females, crabs were captured from three sites (Beagle Channel 55°S, Tierra del Fuego Atlantic coast 52-54°S and San Jorge Gulf 45-47°S). Fecundity, water and lipid contents were measured in midgut gland, ovary and muscle. To assess the maternal investment in the offspring, egg masses were analysed on lipid, protein, water and inorganic matter contents, egg volume and embryo size. Although fecundity was similar among sites, San Jorge Gulf females showed higher water and lower lipid contents in somatic and reproductive organs. The egg mass energy reserves varied among sites, showing the highest lipid values in the Beagle Channel, and the highest protein and inorganic matter content in San Jorge Gulf. Though water content was similar, egg volume and embryo size were higher in San Jorge Gulf. Moreover, maternal size did not correlate with egg volume, embryo size or lipid, protein and inorganic matter content of the eggs. This study suggests that reproductive investment of L. santolla varies among regions exposed to different environmental conditions, such as the quality of food available, denoting a female compensatory mechanism.

Transportation methods for Southern king crab: From fishing to transient storage and long-haul packaging

Live transport of crustacean species is a relatively recent practice that increases the fisheries trade’s chain of profits, without increasing the fishing effort. However, there are few biological and technological studies on developments to enhance animal welfare, reduce mortality rates and consequently avoid economic losses. We aimed to study different transportation and packaging methods to improve the live market practices for the Southern King Crab Lithodes santolla (SKC). To achieve this goal, we conducted two live transport experiments. In the first, crabs were fished and taken (under semi-dry conditions) to the shore either stacked or with free-mobility and then placed in aquaria for recovery. The second experiment consisted of a transport simulation of SKC packed with either Macrocystis pyrifera or burlap bags, as moist materials. In both experiments, we recorded crab vigor and hemolymph metabolites to assess the stress after transportation and during re-immersion. We found that the stress produced by transport to shore disappeared after 48 h of re-immersion in aquaria with seawater re-circulation. Also, burlap bags as packing moist material for long-haul transport decreased the transportation-produced stress and enhanced the recovery of SKC, compared to M. pyrifera packaging. We conclude that crab re-immersion in a stocking center immediately after fishing is essential for the live market, especially to allow survival during further transportation. Additionally, improvements in packing materials not only increase future market earnings, but also improve animal welfare and environmental safety.

Effects of starvation and stocking density on the physiology of the male of the southern king crab Lithodes santolla

The southern king crab (SKC) Lithodes santolla is an important commercial species in southern South America. There is a greater need for availability of fresh and live crabs during the season of highest demand in summer (mainly December and January). Thus, this study aimed to determine the effects of starvation and stocking densities on the physiological status of male SKC to know whether SKC can be stocked after they are fished. To assess the effects of starvation, crabs were assigned to two experimental groups: the Laboratory group (in which crabs were either fed daily (controls), fed every 15 days, or starved and the Sea group (in which crabs were either fed every 15 days or starved). Starved crabs showed a very slight mass reduction (<5%), glycogen depletion from the midgut gland (when kept at sea), lipid peroxidation reduction in both the muscle and the midgut gland, and micro-structural alterations of the midgut gland. Starved crabs were then analyzed at three stocking density levels: low (35 crabs m−3), medium (69 crabs m−3), and high (115 crabs m−3) for 30 days. In this experiment, we found, at all densities, a decreased weight of the midgut gland, a low condition index, decreased lipase activity, glycogen reduction, increased protein reserves, and lipid peroxidation reduction, and decreased lipid levels at low and medium densities. The muscle showed, at all densities, an increased protein oxidation and a decrease in the RNA:DNA ratio. Our results suggest that SKC can tolerate relatively high stocking densities, have low mortality, and are able to endure 60 days of food deprivation without lowering their flesh yield. This would allow marketing crabs alive off-season.

Temperature-dependent seminal recovery in the southern king crab Lithodes santolla.

Male-biased fishery management can provoke depletion of seminal reserves, which is the primary cause of sperm limitation. Therefore, identifying factors which contribute to the vulnerability to depletion of seminal reserves is a priority. The present study aimed to determine the effect of temperature on the recovery rate of sperm and seminal reserves after their depletion in Lithodes santolla, an important fishery resource in southern Chile. Sperm and seminal reserves were not fully recovered within 30 days. Temperature significantly affected seminal recovery: after 30 days the recovery index increased to 40% and 21% at 9°C and 12°C, respectively. The twice as fast seminal recovery at 9°C may be explained by the zone of origin of the individuals in this study (northern distributional limit), and 12°C may be close to the threshold of temperature tolerance. Lithodes santolla populations subject to intense male-only fisheries may be vulnerable to depletion of seminal reserves and a climate change scenario could additionally aggravate the risk of seminal depletion in L. santolla in its northern distributional limit.

Effect of the temperature of air exposure on the oxidative stress status of commercial male southern king crab Lithodes santolla

Live transport to markets requires a baseline on the effects of temperature during air-exposure and the subsequent recovery in water. Our aim was to analyze the physiological effect of 24 h of air exposure in commercial male Lithodes santolla at different temperatures and subsequent re-immersion. Three groups of animals were air-exposed at three temperatures (4 °C, 8 °C and 12 °C) for 24 h, and then re-submersed for 12 h. The control group was kept in water at 8 °C. Samples of haemolymph were extracted after air exposure and re-immersed. We measured superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), ascorbic acid (AA), and protein oxidation (PO). Animals exposed at 12 °C died during emersion. Almost all measured parameters changed with air exposure and temperature. The total recovery of most of the analyzed oxidative stress parameters was attained only at 8 °C, where SOD, CAT and GPx, AA, glucose, and pH returned to values similar to the control group. In animals exposed at 4 °C, only SOD and AA returned to basal levels. Acclimation temperature is an important parameter to consider in the shipping-stock chain of L. santolla, since changes in temperature might be an extra factor of stress during recovery of the animal, besides the reperfusion itself.

Egg production and validation of clutch fullness indices scale of southern king crab, Lithodes santolla, in the Central Patagonian Sector, Argentina (44°–48°S)

Egg production of the southern king crab Lithodes santolla from the Central Patagonian Sector, Argentina was assessed by analyzing the size - fecundity relationships and egg quality of this species. As well, the effect of spatial variability of these parameters was studied. Furthermore, the effectiveness of the "Clutch Fullness Indices" (CFI) scale used for detects variations in egg production of this species was analyzed. Fecundity of L. santolla, during the 2015–2016 season, showed a positive relationship with female size (CL) and ranged between 1780 and 36,788 eggs for females between 64 and 123 mm CL. In the present study, fecundity did not differ among Central Patagonian Sector areas. In addition, visual assignment of CFI was associated with different size-fecundity relationship; females with low CFI scores had lower fecundities. These results suggest that the current CFI method can be used as a tool to understand spatial and temporal variability egg production for L. santolla, in particular may be useful to distinguish large differences in fecundity (e.g., >50%). L. santolla egg diameter values ranged between 1537 and 1984 μm. This variable showed no relationship with the female’s size and did not differ between CFI categories or location. On the other hand, egg dry weight (DW) ranged between 38 and 68 mg (x 50 eggs) and showed a positive relationship with female size. This result suggests that DW may be a more sensitive index to evaluate egg quality for this species. It was observed that eggs of females with 50% CFI also had a significantly lower DW than those corresponding to females with 100% CFI, which would indicate that both the number and the quality of the eggs would be affected in females with lower CFI values. Moreover, differences in egg DW between Central Patagonian Sector areas were found. These results support the "maternal effect" hypothesis in L. santolla, which proposes not only higher fecundity in larger females, but also better quality eggs. These results provide critical data that may be used in stock assessment models to establish a base line to evaluate the effects of fishing and environmental changes on reproductive potential.

Suspended mesh-bags enclosures for Southern King Crab Lithodes santolla (Molina 1782) larvae and juvenile culture in the sea

The potential for using suspended mesh-bags for larval/juvenile southern king crab (Lithodes santolla) aquaculture was assessed. Three early stages (Zoea, Megalopa and first juvenile, or C1) were confined for 45–65 days in mesh-bags near the sea-bottom. As L. santolla starts feeding when it reaches the first juvenile stage, the effect of biofouling presence was also tested in the C1 culture. Extreme vulnerability of the first larval stage was observed, as no live larvae were recovered when Z1 were used as seeds. On the other hand, survival of Megalopa and C1 reached 19.76 ± 1.08 and 30.00 ± 3.50%, respectively, and both C1 juvenile survival and growth were enhanced significantly by the presence of biofouling on the bags. These results indicate that suspended mesh-bags have potential for L. santolla juvenile culture in the sea. We suggest a 2-step culture process: indoor culturing of the three Zoea stages, and subsequently sea culture starting at the Megalopa stage. Once Megalopa molt to the C1 stage in the field, the already fouled culture system (mesh-bags) would allow newly molted crabs to feed. Further research should be directed towards sea culture optimization, including feeding requirements for bigger crabs, to implement a future stock enhancement program for king crabs in the Beagle Channel.

First record of microplastics in stomach content of the southern king crab Lithodes santolla (Anomura: Lithodidae), Nassau bay, Cape Horn, Chile

This study reports the first record of microplastics in the stomach contents of the king crab Lithodes santolla. Samples were collected in Nassau Bay during September 2017. Plastics ingested belonged to small microplastics between 3.0 and more than 20 mm long having mainly blue color. Their frequency of occurrence in stomachs was 27%. The microplastic ingestion by L. santolla may present not only a risk for the species self, also for other trophic levels in the food web.

Infestation of Pseudione tuberculata (Isopoda: Bopyridae) on juveniles of Lithodes santolla (Magellan region, Chile): a spatial mesoscale analysis

We document latitudinal patterns of infestation of the bopyrid parasite isopod Pseudione tuberculata on southern king crab Lithodes santolla juveniles (20-77 mm carapace length) recruited to fishing grounds in the southern Chilean fjord system. Seven hundred and fifty individuals were collected by semiautonomous diving in 11 of 21 sampling locations in the study area, along the western margin of the Magellan region between August and October 2013.The prevalence of P. tuberculata varied between 0 and ~22%, and displayed a spatial pattern associated with three areas: i) northern Beagle Channel (10 to ~22%; lengths between 37 and 47 mm), ii) northwestern Navarino Island without infestations (0%; 26-55 mm), and iii) Piazzi Island-Capitan Aracena Island (0-12%; 50-77 mm). Infestations were independent of host sex, while parasite prevalence decreased with host length. No parasites were observed on crabs longer than 60 mm. A comparison of slopes between linearized length-weight regressions suggests that parasitized individuals had lower weight growth than uninfested individuals. Both southern king crab juvenile density and P. tuberculata prevalence were higher in fishing areas towards Beagle Channel where previous research reported lower average surface water temperatures ( 30). The study area covers five zones relevant for the conservation and protection of sub Antarctic biodiversity, and provides opportunities for large-scale geographic studies of the host-parasite relationship

Egg loss in females of two lithodid species following different return-to-the-water protocols

Coastal waters of the southern tip of South America have sustained a mixed king crab fishery since the 1930s, with two target species: the southern king crab Lithodes santolla and the stone crab Paralomis granulosa. The fisheries are managed with the so-called 3S rule (Sex, Season, and Size) and females must be returned to the water. In king crabs, fecundity can be reduced by several mechanisms, but those related to fishing activities are only partially known. In this article, we tested experimentally whether egg loss is caused by the return of L. santolla and P. granulosa ovigerous females to the water. To do so, we performed experiments for each species with a 3×2 different return-to-the-water conditions: free fall, ramp, or a no-fall (control), with or without previous aerial exposure of females. Our experiments demonstrate that free fall impacts, similar to the normal practice in the fishery of the Beagle Channel, result in egg loss in both the species. Female L. santolla lost more eggs if females were exposed to air prior to the dropping. Also, eggs with more developed embryos were likely to be lost as a result of tumbling. In both the species, the use of a ramp for the returning of crabs to water caused an egg loss similar to those of the experimental controls. In P. granulosa fecundity from three areas with different fishing effort suggest that the return of females to the water may be a negative effect that could be detected at a population level. To our knowledge, this is the first study that demonstrates the egg loss of female crabs returned to the water in a fishery.

Feeding strategy of early juvenile stages of the southern king crab Lithodes santolla in the San Jorge Gulf, Argentina

Resumen.- Se analizo el contenido estomacal de 313 ejemplares juveniles de centolla de ambos sexos con longitudes de caparazon (CL) entre 8,40 y 49,04 mm, estudiandose la influencia del sexo, talla, estado de muda y estacion del ano. Los animales fueron capturados mediante buceo en muestreos estacionales en el infralitoral rocoso del area central del Golfo San Jorge. Se determino la frecuencia de ocurrencia (FO) y abundancia relativa (AR) de las presas halladas, estado de replecion y peso del contenido estomacal. Se registro un 14,4% de animales con el estomago vacio, un 55,1% con replecion menor del 50% y un 30,5% mayor al 50%. Los juveniles no se alimentan antes de mudar, durante la muda ni en postmuda reciente. Se identificaron 27 grupos de presas diferentes, incluidas varias especies de algas, protistas e invertebrados. Las mayores FO fueron registradas en algas coralinaceas (45,1%), ofiuroideos (34,8%), equinoideos (25,1%), isopodos (21,7%), moluscos bivalvos (19,5%), poliquetos (16,9%) y briozoos (15%). En terminos de AR, los principales componentes de la dieta fueron ofiuroideos, isopodos y coralinaceas. La composicion de la dieta es diferente en animales menores de 15 mm CL de aquellos mayores a esa talla, debido a la mayor abundancia de isopodos y briozoos en este intervalo. La gran diversidad de presas registradas indica que los juveniles son esencialmente depredadores macrofagos y omnivoros, que aprovechan los complejos habitats infralitorales rocosos y biogenicos del area estudiada para su alimentacion y refugio durante los primeros anos de vida. Palabras clave: Dieta, depredacion, Lithodes santolla, juveniles, aguas costeras, omnivoria

Experimental natural substrate preference of southern king crab Lithodes santolla larvae

Notwithstanding the commercial importance of Lithodes santolla in the southern tip of South America, little is known about settlement habitat and behavior of their larvae. Such information is relevant for understanding its life history and for management and development of fishery-stock enhancement programs. The aims of this study were to determine the natural substrata that larval stages, zoeae and megalopa select for recruitment, and the effects of megalopa density and diurnal–nocturnal phase on such selection. Different laboratory experiments with durations of 8h to 4weeks were performed in 6-L round containers with their bottoms divided in four equal portions, each filled with sand, gravel, cobble and broken shell as substrata. Containers were kept in a cold room at 7.1±0.5°C and under 12:12h light and dark photoperiod. Trials began with the release of larvae of different stages in the center of the containers. After different time periods, proportions of larvae swimming or settled on each substrate were determined. Larvae selected and settled on natural substrata immediately after being placed into the containers. Experiments showed that all larval stages (zoeae and megalopa) preferred complex substrata such as broken shell, cobble and gravel over sand which was rejected. The megalopa selects the substrate even during night period. Selection seems to be density-dependent since at the lowest density broken shell was the preferred substrate. Selection of complex substrata (i.e. mussel beds and/or shell fragments in nature) by all larval stages, even as early as the first zoea stage, provides a cryptic habitat which may reduce mortality by predation and/or cannibalism. Knowledge on habitat preference is useful for fishery management and also for assessing the different habitats in a potential stock enhancement program of southern king crab.

Cannibalism during intermolt period in early stages of the Southern King Crab Lithodes santolla (Molina 1872): Effect of stage and predator–prey proportions

The anomuran crab Lithodes santolla represents an important fishery resource in the southernmost part of the American continent, where populations are endangered by overexploitation. During first attempts of rearing, intraspecific predation was observed in early stages of L. santolla and may stand as a main source of mortality in cultures. Cannibalism (defined as the sum of injured and dead crabs) between larvae and juveniles of L. santolla was tested in five Predator–prey (P–p) stage combinations and three P–p proportions during the intermolt period. Intra-stage predation in Megalopae (M), crab stage 1 (C1) and crab stage 2 (C2) was similar between stages (~15%) and lower than inter-stage cannibalism. Difference in size of conspecifics was the main cause of cannibalism. Total consumption of prey after 3–5days was observed when 1-year-old crabs (C1yo) encountered either zoeae 1 (Z1), M or C1. Cannibalism in the combination C2–C1 occurred immediately after experiments began. Contrastingly, in the combination C1–M cannibalism started after day 9 of the experiment, suggesting that the swimming ability of M is a key factor for predator avoidance. At the end of intermolt period cannibalism was higher in C2–C1 than in C1–M stage combination and reached 75% and 60% respectively. Directionality of attacks among crabs showed that bigger animals can cause severe damage to smaller ones and not vice versa. Injured predators were only observed in C1–M stage combination and are likely the result of intra-stage cannibalism among C1 when M remain unreachable. P–p proportions had an impact on cannibalism since the more unequal the P–p proportions, the higher the cannibalism in both C1–M and C2–C1 stage combinations. Differential limb loss occurred in L. santolla since walking legs appeared more vulnerable than chelipeds. Although L. santolla showed high predation among conspecifics, cannibalism in early juvenile stages under natural conditions should be lower than in the present study, as density of cultures was high (~950indm−2) and our experimental design provides no refuge/shelter to animals. Hence, the future challenge for massive culturing crabs will be the mitigation of cannibalism.

Infestation of the squat lobster Munida gregaria (Anomura: Galatheidae) by Pseudione galacanthae (Isopoda: Bopyridae) in San Jorge Gulf, Argentina

We estimated the prevalence of the bopyrid Pseudione galacanthae parasitizing the population of the squat lobster Munida gregaria in San Jorge Gulf and analysed some aspects concerning the effect of the parasite on host reproductive potential. The relationship between the development stages of the parasite and the host size was also analysed. The squat lobsters were caught as by-catch in the coastal area of the gulf from vessels operating in the fisheries of hake Merluccius hubbsi, southern king crab Lithodes santolla and Argentine red shrimp Pleoticus muelleri. The samples were collected between October 1997 and June 2009. In the laboratory, squat lobsters were sexed and the length of their carapace was measured. In males, the length of the right cheliped was recorded and gonadal development was examined. In females, the size and number of carried eggs were determined and the length of the pleopods III, IV and V were measured. All squat lobsters parasitized exhibit a gross bulge in the right side of carapace. Prevalence ranged between 0 and 1.43% (N = 21,519). No significant differences in prevalence were found for sexes, depths and seasons. The prevalence was higher for the size interval 7–10 mm CL (0.79%) than for the rest of the intervals. Parasitism had no effect on the secondary sex characters. Parasitized males displayed gonad development. There was no difference in prevalence between ovigerous and non-ovigerous squat-lobster females. Parasitized females had smaller eggs than non-parasitized ones, but their fecundity was similar. The linear relationship between the parasite and host sizes and the presence of larvae and immature stages of P. galacanthae in small-sized squat lobsters suggest that the host is infected early in its development. The low prevalence could be related to oceanographic conditions which favour larval dispersal of the parasite and host. The infestation by P. galacanthae has little impact on the M. gregaria population, mostly due to the low prevalences of infestation and the minor impact in reproductive function.

Effect of dissolved oxygen level on respiratory metabolism, nutritional physiology, and immune condition of southern king crab Lithodes santolla (Molina, 1782) (Decapoda, Lithodidae)

Episodes of hypoxia are common in the marine environment, and their ecological effects depend, in part, on their severity and duration. Many species of decapod crustaceans reside in areas with fluctuating oxygen regimens. Physiological mechanisms enhance the ability of these crustaceans to cope with acute episodes of hypoxia. Southern king crab, Lithodes santolla, fishery is important in the south of South America, and some data describe fishing zones with low dissolved oxygen (DO) levels (3.5 mgO2 l−1, i.e., 8.3 kPa). Our main objective was to evaluate the effect of dissolved oxygen level on respiratory metabolism, nutritional physiology, and immunological condition of L. santolla juveniles. Individual animals were exposed for 10 days to different oxygen tensions (2.1, 4.2, 8.5, 12.7, and 21.1 kPa) to quantify the oxygen consumption rate; thereafter, blood oxyhemocyanin (Hc), protein concentration, as well as hemocytes, were sampled. Freeze-dried animals were dissected, and digestive gland metabolites (glycogen, protein, glucose, cholesterol, acylglycerol, and lactate) and digestive enzyme activity (general protease, trypsin, and chymotrypsin), as well as gill lactate dehydrogenase (LDH) activity, were quantified. In the present study, Lithodes santolla showed a critical oxygen tension between 4 and 9 kPa, indicating that this crab species is more sensitive to DO than other crustacean species. Protein and Hc concentrations followed a similar pattern to that of oxygen consumption. Digestive gland glycogen and protein concentration did not change after 10 days at different oxygen exposures, but glucose, cholesterol, and acylglycerol concentrations decreased linearly and proportionally to the available oxygen in the water. As in other decapods, chymotrypsin showed over 90% of the total quantified proteases activity. Chymotrypsin activity together with total proteases and trypsin was not affected by the environmental oxygen tension. Gill LDH and digestive gland lactate followed a similar increase at lower environmental oxygen tension but dropped sharply at the lowest tension (2.1 kPa). Dissolved oxygen affected also the immune system through reduction of hemocytes. This could provide a critical window for opportunistic pathogens to become established when crabs are exposed to hypoxic conditions. L. santolla juveniles show a moderate tolerance to low oxygen availability by modifying the concentration of hemolymph proteins, mainly OxyHc, some digestive gland metabolites, and by activating the anaerobic metabolism. This allows L. santolla juveniles to inhabit temporarily low oxygen zones in the deep ocean and suggests an advantage for culture conditions.

Effects of lead and cadmium on hatching of the southern king crab Lithodes santolla (Decapoda, Anomura)

Summary Eggs of the king crab Lithodes santolla were exposed to cadmium (0.2 and 2 mg/1) and lead (0.16 and 1.6 mg/1) for 30 days. Concentrations used represented 1/10 and 1 of the respective LC50 values for zoea I of the studied species. Proportion of larvae hatching, meantime of eclosion and proportion of abnormal larvae were recorded. Abnormalities detected were hydropsy; small size; and atrophy of dorsal, rostral and telson spines, as well as atrophy of pereiopods and telson setae. The mean time of eclosion was inversely correlated to the incidence of structural abnormalities such as atrophy of spines and setae. These results suggest that both cadmium and lead caused an early eclosion of underdeveloped larvae, but while cadmium caused also a significant increase in hatching rate, lead produced a significant decrease in the proportion of larvae hatching.