Cancer Antennarius Research Articles

Physiological responses of the red rocky crab Cancer antennarius exposed to different concentrations of copper sulfate

Se evaluaron en el cangrejo de roca Cancer antennarius las respuestas fisiologicas, metabolicas y hematologicas a diferentes concentraciones de sulfato de cobre (0,5, 1,0, 1,5, 2,0 mg L-1). Las respuestas a determinar fueron: dosis letal media, capacidad osmorreguladora, consumo de oxigeno, excrecion de amonio, relacion atomica O:N, glucosa, el CTH y la concentracion de hemocianina. En cuanto a la dosis letal media (LD50) se determino que la concentracion fue de 1,6 mg L-1 de sulfato de cobre. El patron observado en la mayoria de las respuestas medidas fue un aumento directamente proporcional a la concentracion de sulfato de cobre; a excepcion de la capacidad osmorreguladora, en la que el patron de osmorregulacion, de ser tipicamente isosmotico en condiciones normales, se modifico a hiposmotico. En la relacion atomica O:N se observo una disminucion en los valores debido a cambios en sustrato metabolico como un resultado del estres causado por la exposicion al sulfato de cobre.

The effects of thermal acclimation on the behavior, thermal tolerance, and respiratory metabolism in a crab inhabiting a wide range of thermal habitats (Cancer antennarius Stimpson, 1856, the red shore crab)

The preferred temperature of Cancer antennarius determined with the acute method was 15.2 °C, and with the gravitation method was 15.9 ± 1.9 in the day cycle and 13.2 ± 0.6 °C in the night cycle. The critical thermal maximum increased as the acclimation temperature was increased (p < 0.05); the thermal tolerance interval was 1.3, indicating that this species has a low tolerance indicative that it has evolved in highly stable environments. The acclimation response ratio for adults had an interval of 0.10–0.30. These values allow us to characterize this species as inhabiting cold and temperate regions. The oxygen consumption rates increased significantly (p < 0.05) from 6.57 to 9.92.0 mg O2 kg−1 h−1 wet weight as the acclimation temperature increased from 15 to 24 °C. The range of temperature coefficient (Q10) between 15 and 18 °C was the lower than 1.70 and corresponds with the intervals of preferred temperature.

Invasion resistance on rocky shores: direct and indirect effects of three native predators on an exotic and a native prey species

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 378:47-54 (2009) - DOI: https://doi.org/10.3354/meps07870 Invasion resistance on rocky shores: direct and indirect effects of three native predators on an exotic and a native prey species J. S. Shinen1,*, S. G. Morgan2, A. L. Chan2 1Estación Costera de Investigaciones Marinas, Departamento de Ecología, Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile 2Bodega Marine Laboratory, Department of Environmental Science and Policy, University of California Davis, PO Box 247, Bodega Bay, California 94923, USA *Email: jlshinen@bio.puc.cl ABSTRACT: Trophic relationships among native and exotic species produce novel direct and indirect interactions that can have wide-ranging community level effects and perhaps confer invasion resistance. We investigated whether native predators have the potential to directly limit the spread of the exotic mussel Mytilus galloprovincialis or mediate interactions among native and invasive mussels at a rocky intertidal invasion front in northern California. Lower survival of M. galloprovincialis in transplanted cultures exposed to predators indicated that the invader was more vulnerable to predators than the numerically dominant native M. californianus. Survival and per capita mortality rate in monocultures and polycultures did not vary for either M. galloprovincialis or M. californianus, suggesting that predator-mediated apparent competition and associational defense did not occur. Complementary laboratory feeding trials determined which among 3 intertidal predators preferred the exotic to 2 native species of mussel. The whelk Nucella ostrina was most selective, consuming the thinner shelled mussels (M. galloprovincialis and the native M. trossulus) rather than the thicker-shelled native species M. californianus. The crab Cancer antennarius and the sea star Pisaster ochraceus showed no preferences among mussel species. N. ostrina were commonly observed among field-transplanted mussels; thus whelk predation may be especially important in limiting the establishment of the invasive mussel. However, 15% of M. galloprovincialis remained intact in the field after 1 yr, suggesting that predation alone may not inhibit establishment of the invader. A tenuous balance between larval settlement and early post-settlement predation likely characterizes the invasion front. KEY WORDS: Invasion · Resistance · Predation · Indirect effects · Rocky intertidal · Mussel · Mytilus Full text in pdf format PreviousNextCite this article as: Shinen JS, Morgan SG, Chan AL (2009) Invasion resistance on rocky shores: direct and indirect effects of three native predators on an exotic and a native prey species. Mar Ecol Prog Ser 378:47-54. https://doi.org/10.3354/meps07870Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 378. Online publication date: March 12, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Presence of Alexandrium catenella and paralytic shellfish toxins in finfish, shellfish and rock crabs in Monterey Bay, California, USA.

The central California coast is a highly productive, biodiverse region that is frequently affected by the toxin-producing dinoflagellate Alexandrium catenella. Despite the consistent presence of A. catenella along our coast, very little is known about the movement of its toxins through local marine food webs. In the present study, we investigated 13 species of commercial finfish and rock crabs harvested in Monterey Bay, California for the presence of paralytic shellfish toxins (PSTs) and compared them to the presence of A. catenella and PSTs in sentinel shellfish over a 3-year period. Between 2003 and 2005, A. catenella was noted in 55% of surface water samples (n = 307) and reached a maximum concentration of 17,387 cells L−1 at our nearshore site in Monterey Bay. Peak cell densities occurred in the month of July and were associated with elevated shellfish toxicity in the summers of 2004 and 2005. When A. catenella was present, particulate PSTs were detected 71% of the time and reached a maximum concentration of 962 ng STXeq L−1. Of the 13 species tested, we frequently detected PSTs in Pacific sardines (Sardinops sagax; maximum 250 μg STXeq 100 g−1), northern anchovies (Engraulis mordax; maximum 23.2 μg STXeq 100 g−1), brown rock crabs (Cancer antennarius; maximum 49.3 μg STXeq 100 g−1) and red rock crabs (C. productus; 23.8 μg STXeq 100 g−1). PSTs were also present in one sample of Pacific herring (Clupea pallas; 13.3 μg STXeq 100 g−1) and one sample of English sole (Pleuronectes vetulus; 4.5 μg STXeq 100 g−1), and not detected in seven other species of flatfish tested. The presence of PSTs in several of these organisms reveals that toxins produced by A. catenella are more prevalent in California food webs than previously thought and also indicates potential routes of toxin transfer to higher trophic levels.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-008-1103-z) contains supplementary material, which is available to authorized users.

A Key to the Identification of Brachyuran Zoeae of the San Francisco Bay Estuary

San Francisco Bay and its estuary is a heavily invaded region due to organisms arriving in ballast water and on fouled ships, as well as with the intentional release of non-native species. Recent crab invasions rendered previous means to identify crab larvae unusable. We provide an illustrated dichotomous key with descriptions of stage I zoeae, and to facilitate identification use external characters that remain definitive through all zoeal stages. Crab zoeae included in this key are as follows: Cancer antennarius, Cancer gracilis, Cancer magister, Cancer productus, Carcinus maenas, Eriocheir sinensis, Hemigrapsus nudus, Hemigrapsus oregonensis, Lophopanopeus bellus, Rhithropanopeus harrisii, Pachygrapsus crassipes, Pyromaia tuberculata, and the family Pinnotheridae. This work aims to provide a tool to aid in the understanding of brachyuran zoeae of the San Francisco Bay and estuary.

Members of the crustacean hyperglycemic hormone (CHH) peptide family are differentially distributed both between and within the neuroendocrine organs ofCancercrabs: implications for differential release and pleiotropic function

The crustacean hyperglycemic hormone (CHH) family of peptides includes CHH, moult-inhibiting hormone (MIH) and mandibular organ-inhibiting hormone (MOIH). In the crab Cancer pagurus, isoforms of these peptides, as well as CHH precursor-related peptide (CPRP), have been identified in the X-organ-sinus gland (XO-SG) system. Using peptides isolated from the C. pagurus SG, antibodies to each family member and CPRP were generated. These sera were then used to map the distributions and co-localization patterns of these peptides in the neuroendocrine organs of seven Cancer species: Cancer antennarius, Cancer anthonyi, Cancer borealis, Cancer gracilis, Cancer irroratus, Cancer magister and Cancer productus. In addition to the XO-SG, the pericardial organ (PO) and two other neuroendocrine sites contained within the stomatogastric nervous system, the anterior cardiac plexus (ACP) and the anterior commissural organ (ACO), were studied. In all species, the peptides were found to be differentially distributed between the neuroendocrine sites in conserved patterns: i.e. CHH, CPRP, MIH and MOIH in the XO-SG, CHH, CPRP and MOIH in the PO, and MOIH in the ACP (no immunolabeling was found in the ACO). Moreover, in C. productus (and probably in all species), the peptides present in the XO-SG and PO were differentially distributed between the neurons within each of these neuroendocrine organs (e.g. CHH and CPRP in one set of XO somata with MIH and MOIH co-localized in a different set of cell bodies). Taken collectively, the differential distributions of CHH family members and CPRP both between and within the neuroendocrine organs of crabs of the genus Cancer suggests that each of these peptides may be released into the circulatory system in response to varied, tissue-specific cues and that the PO- and/or ACP-derived isoforms may possess functions distinct from those classically ascribed to their release from the SG.

Reproduction, diet and habitat use of leopard sharks, Triakis semifasciata (Girard), in Humboldt Bay, California, USA

A total of 312 female leopard sharks (Triakis semifasciata) was sampled in Humboldt Bay, California, USA, an important nursery ground for this species, during the spring month of May from 1983 to 1984 and 1985. Sexual segregation is strong as only three males were observed in the study area. Females ranged in size from 120 to 154 cm total length, and all examined were determined to be mature. Overall, 130 out of 153 females examined in early May contained term embryos. The number of embryos per female ranged from 1 to 37 with larger females tending to possess more embryos. Of the 159 individuals examined in late May, no females were found carrying embryos and most were ovulating. Diet analyses revealed that, overall, fish eggs (Atherinopsis californiensis) at 48.0%, had the highest percentage Index of Relative Importance (%IRI), followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Adults shift their diet after parturition: early May sharks fed almost exclusively on fish eggs, while crabs were more important in those examined in late May.

Role of food subsidies and habitat structure in influencing benthic communities of shell mounds at sites of existing and former offshore oil platforms

Mussels (Mytilus californianus, M. galloprovincialis) and other organisms sloughed from offshore oil platforms provide a food subsidy to benthic consumers and alter underlying soft bottom habitat by creating hard substrate. The removal of overlying platforms eliminates this food subsidy, but large shell mounds remain. The distribution, abundance, and population characteristics of mobile macroinvertebrates differed among shell mounds beneath existing offshore oil platforms, shell mounds at the former sites of offshore oil platforms, and soft bottom. Predatory and omnivorous echinoderm and mollusk species were more abundant and generally larger on shell mounds under platforms than on shell mounds without platforms. Omnivorous and deposit feeding echinoderms were the most abundant macroinvertebrate taxa sampled on mound-only sites. The brown rock crab (Cancer antennarius), known to have a strong preference for hard substrate, was significantly more abundant on shell mounds, with or without platforms, than adjacent soft bottom sites. Results suggest that the effects of platform removal differed among benthic species according to trophic level, degree of mobility, and substrate preference. Although the shell mound habitat persists after removal of platform structures, species abundance and the composition of the associated benthic community is altered by removal of the platform structure.

Hair-trigger autotomy in porcelain crabs is a highly effective escape strategy

The benefits of autotomy, the voluntary shedding of limbs, have been adequately demonstrated in vertebrates but are poorly studied in invertebrates. We provide strong experimental evidence for an antipredatory benefit to autotomy in two porcelain crabs (Petrolisthes cinctipes and P. manimaculis). Since the outcome of autotomy depends critically on the species of predator and prey involved, we first surveyed field populations of porcelain crabs to identify ecologically relevant predators to use in subsequent experiments. We then examined the escape tactics of the porcelain crabs in response to the four potential predators we identified, all larger predatory crabs. Cheliped autotomy was induced by three of the predator species (Cancer antennarius, Hemigrapsus nudus, Pachygrapsus crassipes); the fourth did not attack porcelain crabs. Autotomy occurred in response to 34% of all attacks, and in 67% of attacks in which the prey was held at some point by only the cheliped. Autotomy was a highly effective escape mechanism against these predators; 58 of 59 crabs that autotomized escaped, usually while the predator stopped pursuit to eat the shed cheliped. Reliance on autotomy as a primary mechanism for escaping predators may be particularly common in small crabs that cannot adequately defend themselves by other means and in suspension-feeding crabs that do not need their chelipeds for feeding. Key words: autotomy, crabs, Crustacea, escape strategy, predation. [Behav Ecol 13:481–486 (2002)]

Characterization of cDNA encoding molt-inhibiting hormone of the crab, Cancerpagurus; expression of MIH in non-X-organ tissues

Synthesis of ecdysteroids (molting hormones) by crustacean Y-organs is regulated by a neuropeptide, molt-inhibiting hormone (MIH), produced in eyestalk neural ganglia. We report here the molecular cloning of a cDNA encoding MIH of the edible crab, Cancer pagurus. Full-length MIH cDNA was obtained by using reverse transcription-polymerase chain reaction (RT-PCR) with degenerate oligonucleotides based upon the amino acid sequence of MIH, in conjunction with 5′- and 3′-RACE. Full-length clones of MIH cDNA were obtained that encoded a 35 amino acid putative signal peptide and the mature 78 amino acid peptide. Of various tissues examined by Northern blot analysis, the X-organ was the sole major site of expression of the MIH gene. However, a nested-PCR approach using non-degenerate MIH-specific primers indicated the presence of MIH transcripts in other tissues. Southern blot analysis indicated a simple gene arrangement with at least two copies of the MIH gene in the genome of C. pagurus. Additional Southern blotting experiments detected MIH-hybridizing bands in another Cancer species, Cancer antennarius and another crab species, Carcinus maenas.

Further Studies on Signaling Pathways for Ecdysteroidogenesis in Crustacean Y-Organs

The Y-organs of crustaceans secrete ecdysteroids (molting hormones) and are regulated (negatively) by a neurosecretory peptide, molt-inhibiting hormone (MIH). Signaling path(s) in Y-organs were explored that connect MIH receptors ultimately with suppression of receptor number for the uptake of cholesterol (ecdysteroid precursor) and of gene expression of steroidogenic enzymes. Experiments were conducted in vitro with Y-organs of crabs (Cancer antennarius, Menippe mercenaria) and crayfishes (Orconectes sp.). It was confirmed in all species that steroidogenesis occurs in the absence of external calcium (Ca++), but increases to a maximum as Ca++ is increased to 1 to 10 mM and is substantially inhibited at higher Ca++ concentrations. MIH does not require external Ca++ for inhibitory action, but inhibition is eliminated by high Ca++concentrations. Several experimental approaches failed to find evidence of phospholipase C activation, turnover of inositol triphosphate or diacylglycerol generation connected with steroidogenesis. Unbinding or chelation of intracellular Ca++ with thapsigargin or TMB-8, respectively both caused dose-dependent inhibition of ecdysteroid output. Blockade of Ca++ channels with verapamil, nifedipine or nicardipine also inhibited steroidogenesis; highest doses inhibited profoundly to below Ca++-free basal levels. Inhibition also was obtained with all doses of the Ca++ channel agonist/antagonist (−) BAY K 8644 in crabs, but in crayfishes lower doses were stimulatory. However, if the crayfish cells were depolarized, allowing greater Ca++ influx, the previously stimulatory doses of BAY K 8644 became inhibitory. Y-organ protein kinase C (PKC) is Ca++-sensitive. Activation of PKC was uniformly stimulatory in crabs, but inhibitory in crayfishes. Cytochalasin D, which disrupts the actin cytoskeleton, and which causes moderate Ca++ influx, stimulated hormone formation. These results are interpreted to indicate a regulatory role for Ca++ in ecdysteroidogenesis, involving a local, submembrane circulation of Ca++ through ion channels and Ca++ pumps and interaction with PKC in phosphorylating key proteins. An optimal local Ca++ environment fostering hormone synthesis is evident since too little or too much Ca++ is inhibitory. Methyl farnesoate (MF) had no effect on ecdysone production in crab or crayfish Y-organs in 24-hr incubations with MF at 100 pM to 10 μM.

Further Studies on Signaling Pathways for Ecdysteroidogenesis in Crustacean Y-Organs1

SYNOPSIS. The Y-organs of crustaceans secrete ecdysteroids (molting hormones) and are regulated (negatively) by a neurosecretory peptide, molt-inhibiting hormone (MIH). Signaling path(s) in Y-organs were explored that connect MIH receptors ultimately with suppression of receptor number for the uptake of cholesterol (ecdysteroid precursor) and of gene expression of steroidogenic enzymes. Experiments were conducted in vitro with Y-organs of crabs (Cancer antennarius, Menippe mercenaria) and crayfishes (Orconectes sp.). It was confirmed in all species that steroidogenesis occurs in the absence of external calcium (Ca 11 ), but increases

Maximum force production: why are crabs so strong?

Durophagous crabs successfully hunt hard-shelled prey by subjecting them to extremely strong biting forces using their claws. Here I show that, for a given body mass, six species of Cancer crabs (Cancer antennarius, Cancer branneri, Cancer gracilis, Cancer magister, Cancer oregonensis and Cancer productus) were able to exert mean maximum biting forces greater than the forces exerted in any other activity by most other animals. These strong biting forces were in part a result of the high stresses (740-1350 kN m(-2)) generated by the claw closer muscle. Furthermore, the maximum muscle stress increased with increasing mean resting sarcomere length (10-18 microm) for the closer muscle of the claws of these six Cancer species. A more extensive analysis incorporating published data on muscle stresses in other animal groups revealed that stress scales isometrically with the resting sarcomere length among species, as predicted by the sliding filament model of muscle contraction. Therefore, muscle or filament traits other than a very long mean sarcomere length need not be invoked in explaining the high stresses generated by crustacean claws.

Effects of an offshore oil platform on the distribution and abundance of commercially important crab species

The distribution, abundance, and population characteristics of large, highly mobile crab species (Cancer antennarius, C. anthonyi, C. productus, Loxorhynchus grandis) differed in relation to an offshore oil platform in the Santa Barbara Channel, California, USA. Only C. antennarius individuals recruited onto the platform, primarily into the attached community of Mytilus galloprovincialis and M. californianus at depths of <12 to 15 m. The higher CPUE (catch per unit effort) of C. antennarius beneath the platform, compared with nearby soft bottom stations, suggested that this species remained primarily in the vicinity of the platform. Although C. anthonyi did not recruit at the platform, adult female C. anthonyi were attracted to the platform from surrounding habitat. The higher CPUE of female C. anthonyi beneath the platform, compared with soft bottom stations, suggested that habitat selection is related to reproduction in this species. C. productus and Loxorhynchus grandis were present in low numbers at all benthic stations. The distribution and abundance of these crab species fit into 3 of 4 hypothesized scenarios that described different combinations of recruitment, distribution and abundance of mobile species around oil platforms: (1) 'recruitment/emigration', a platform provides recruitment habitat and individuals that recruit to the platform emigrate at some point to the surrounding environment, (2) 'recruitment/resident', a platform provides recruitment habitat, but individuals remain in the vicinity of the structure (C. antennarius), (3) 'attraction', individuals that recruited elsewhere are attracted to and aggregate at a platform (C. anthonyi), and (4) 'visitor', individuals that recruited elsewhere occur temporarily at the platform without aggregation (C. productus, L. grandis). Our results, in the context of these scenarios, illustrate the need to consider the responses of individual species to artificial structures.

The clearance in vivo and metabolism of ecdysone and 3-dehydroecdysone in tissues of the crabCancer antennarius

The Y-organs of Cancer antennarius secrete the hormones ecdysone (E) and much greater amounts of 3-dehydroecdysone (3DE), but the dominant derivative in the circulation is 20-hydroxyecdysone (20E). The uptake and clearance of E, 3DE, and metabolites were compared in selected tissues in vivo, and the capacity of each to generate 20E was assessed in vitro. [3H]-labeled E or 3DE, injected into intermolt crabs, rapidly cleared from hemolymph, while being taken up and then rapidly cleared from tissues (muscle, heart, epidermis, ovary) within 1 h. Labeled 20E from E or 3DE appeared in all tissues in the first hour, cleared to varying degrees from tissues, and then reaccumulated over 24 h. Among these tissues, ovary accumulated the most labeled 20E. Generally by 24 h more labeled 20E accumulated from 3DE than from E. Excising the eyestalks (inducing premolt) did not affect the outcomes except that deeyestalking caused much greater concentrations of 3DE than E to appear in all tissues initially. Tissue extracellular volumes ([14C]inulin spaces) were not altered by deeyestalking, except transiently in epidermis, and otherwise did not account for the observed ecdysteroid dynamics. A parallel study with eyestalk neural tissue from crabs receiving [3H]3DE showed extraordinary accumulation of 3DE and labeled metabolites. The normalized tissue/hemolymph ratio was 72 at 8 h, compared with 0.6–2.6 for other tissues. The apparent extracellular volume of eyes was high (80%) but did not account for the high ecdysteroid accumulation. Tissues were incubated 18 h with [3H]3DE. Activities representing 3β-reductase and 20-hydroxylase generally were present, evidenced by finding labeled E and 20E. Tissue blanks, hemolymph, and muscle were devoid of activity, hepatopancreas and epidermis were intermediate, ovary, testis, and hindgut were high, and eyestalk tissue was highest in activities. Low amounts of labeled high-polar material were usually present, and a labeled derivative tentatively identified as 3-dehydro-20-hydroxyecdysone (3D20E) also appeared in ovary, hepatopancreas, hindgut, and eyes, indicating some direct conversion of 3DE to 3D20E. In composite, these data indicate that 3DE secreted by Y-organs is converted to E, thence to 20E by several tissues, accounting for the preponderance of 20E in crustacean hemolymph. The findings support the hypotheses that 20E is the definitive molting hormone (receptor ligand) and that an ecdysteroid feedback mechanism controls release of the molt-inhibiting hormone from the eyestalks. J. Exp. Zool. 279:609–619, 1997. © 1997 Wiley-Liss, Inc.

Uptake of high-density lipoprotein by Y-organs of the crab Cancer antennarius: III. Evidence for adsorptive endocytosis and the absence of lysosomal processing.

Ecdysteroid hormones in crustaceans are synthesized from cholesterol in the Y-organs. Circulating cholesterol is bound to high-density lipoprotein (HDL). Experiments were conducted to find the mode of cholesterol uptake by Y-organ cells. The working hypothesis is as follows: Cholesterol is taken up by endocytosis of the entire HDL-cholesterol complex. HDL was doubly labeled in the apolipoprotein and cholesterol components with 125I and 3H, respectively. The time courses of uptake of the two labels by Y-organ segments in vitro were parallel throughout 24 hr of incubation. Chloroquine, an inhibitor of lysosomal function, had no effect on the uptake and degradation of HDL. Cycloheximide, an inhibitor of protein synthesis, depressed HDL uptake. Transmission electron microscopy of Y-organ tissue showed features characteristic of adsorptive endocytosis, including coated pits in the plasma membranes and their invagination and vesiculation. Visualization of HDL with immunogold binding showed profiles consistent with endocytosis. Quantitation of the distribution of HDL-gold particles indicated that about 75% were associated with cellular formed elements, but not with lysosomes, and significantly more particles overall were present in cells from de-eyestalked crabs than those from intact crabs. These data demonstrate that (a) cholesterol-carrying HDL is taken into Y-organ cells by adsorptive endocytosis, (b) its uptake is dependent on de novo protein synthesis, (c) its intracellular processing is independent of lysosomal enzymes, and (d) its uptake is depressed by the molt-inhibiting hormone secreted by the eyestalks.

Serum high-density lipoproteins in the crab Cancer antennarius—IV. Electrophoretic and immunological analyses of apolipoproteins and a question of female-specific lipoproteins

Apolipoproteins (APO) were analyzed for molecular mass and specificity of occurrence in hemolymph and eggs. Hemolymph donors were males and both ovigerous and non-ovigerous females. Total lipoprotein (LP; exclusively high-density LP) was fractionated into subclasses by density-gradient centrifugation; selected subclasses were delipidated and the APO subjected to electrophoresis under denaturing conditions. Antisera were raised against the isolated APO of both males and females and used for tests of cross-reactivity in Western biots. Principally three protein units were identified (molecular masses: 185, 100 and 84 kDa). Each occurred in the APO of each HDL subclass, in the hemolymphs of males and all females and in eggs. The antisera cross-reacted between all groups. Similar findings were obtained in a less complete study of APO in the blue crab, Callinectes sapidus. Thus, in analyses of isolated APO from two crab species, no evidence could be found for occurrence of a “female-specific protein” (FSP). FSP has been defined as a protein (vitellogenin, more accurately an LP) that is generated only by females active in production of egg yolk LP (vitellin); it is presumed to specialize in transporting yolk lipids. The crustacean literature is surveyed to compare data on APO molecular mass and critically reviewed with regard to FSP.

Uptake of high‐density lipoprotein by Y‐organs of the crab, Cancer antennarius. I. characterization in vitro and effects of stimulators and inhibitors

AbstractCholesterol is the obligate precursor for ecdysteroid hormone synthesis by the ecdysial glands (Y‐organs) in crustaceans, and all cholesterol in the hemolymph is bound to high‐density lipoprotein (HDL). The mechanism was studied of how Y‐organ cells acquire cholesterol. Y‐organ segments were incubated with HDL isolated from hemolymph and labeled with 125I. After incubation, tissue was homogenized in acid to determine radioactivity in acid‐precipitable (cell associated, intact) HDL and in acid‐soluble (degraded) HDL. Both HDL uptake and degradation showed saturation kinetics. At saturation most of the total counts represented degraded HDL; by 3 h, degradation was 80%. Rates of HDL uptake and breakdown were higher in Y‐organs from de‐eyestalked crabs (deprived thereby of molt‐inhibiting hormone, MIH) than in glands from intact crabs. Both parameters were depressed by inhibitors of glycolysis and oxidative phosphorylation dose dependently and by low temperature. HDL uptake also was depressed by cAMP added to the medium experimentally or through efflux from the tissue during incubation. These results indicate a mechanism for HDL uptake that entails receptor‐mediated, energy‐dependent endocytosis of the entire HDL‐cholesterol complex. Also the results suggest that HDL uptake and degradation are mediated by cAMP and depressed by an eyestalk factor, presumably MIH. © 1995 Wiley‐Liss, Inc.

Uptake of high‐density lipoprotein by Y‐organs of the crab, cancer antennarius. II. formal characterization of receptor‐mediation with isolated membranes

AbstractY‐organs are the ecdysial glands of crustaceans, responsible for synthesis and secretion of ecdysteroid hormones. For this purpose, the glands acquire cholesterol as obligate precursor entirely from circulating high‐density lipoprotein (HDL). A preceding study provided evidence for the mechanism of acquisition: Y‐organs take up cholesterol bound to HDL by an energy‐requiring process, receptor‐mediated absorptive endocytosis. The present study characterized the receptors involved utilizing isolated Y‐organ membranes. HDL binding was saturable and specific; a dissociation constant (Kd) of 1.08 × 10−7 M and a binding maximum at equilibrium (Bmax) of 70 μg HDL protein/mg membrane protein, were obtained. Binding was decreased by protease and was dependent upon calcium. Y‐organs are regulated negatively by a peptide hormone from the eystalks, molt‐inhibiting hormone (MIH). Y‐organ membranes from de‐eyestalked crabs (MIH absent) exhibited the same Kd value as membranes from intact crabs, but a Bmax 17% higher. Thus, MIH activity apparently does not change the binding affinity of HDL, but decreases the number of binding sites. These results agree with our previous findings that MIH depresses ecdysteroid synthesis in part by inhibiting cholesterol uptake. Generally, Y‐organ cells appear to contain receptors for HDL that are of high affinity and high binding capacity, similar to the characteristics reported for the binding of insect HDL (vitellogenin) to fat bodies and oocytes. © 1995 Wiley‐Liss, Inc.

Proteins of Crustacean Exoskeletons: I. Similarities and Differences among Proteins of the Four Exoskeletal Layers of Four Brachyurans.

Most of the proteins extracted from exocuticle, endocuticle, and membranous layer of four species of anecdysial (intermolt) crabs (the Bermuda land crab Gecarcinus lateralis, the rock crab Cancer antennarius, the shield-backed kelp crab Pugettia producta, and the southern shield-backed kelp crab Taliepus nuttalli) were 31 kDa or smaller; proteins of similar Mr were common to all three layers. Proteins from the membranous layer were qualitatively indistinguishable in all four species. More proteins 31 kDa or smaller were similar in size and pI to proteins from other exoskeletal layers than were proteins larger than 31 kDa. Proteins extracted from the epicuticle of G. lateralis included a group of five ranging from 54 to 42 kDa that bound 45Ca++ in vitro. The group was not seen in other layers of the exoskeleton of G. lateralis or, with the exception of 44 and 42 kDa protein bands that were in the epicuticle of C. antennarius, in any layers of the exoskeletons of the other three species. During proecdysis, the membranous layer is completely degraded, and proteins 31 kDa or smaller are preferentially degraded from the exocuticle and endocuticle of the old exoskeleton of G. lateralis, which is cast as an exuvia at ecdysis. The relative amounts of proteins in extracts of epicuticle from (1) anecdysial exoskeletons and (2) exuviae were very similar, suggesting that there was little degradation of epicuticle during proecdysis. Some of the proteins of the three inner layers of the exoskeleton of G. lateralis have characteristics similar to those of flexible cuticles of insects; they have acidic pIs and they form "charge trains," i.e., proteins of the same size separated by differences in charge during isoelectric focusing.