Michele G. Wheatly

PHYSIOLOGICAL EFFECTS OF AN ECTOCOMMENSAL GILL BARNACLE, OCTOLASMIS MUELLERI, ON GAS EXCHANGE IN THE BLUE CRAB CALLINECTES SAPIDUS

A 3-year histological study of disease prevalence in 657 blue crabs, Callinectes sapidus, dredged from 31 sites within Maryland portions of Chesapeake Bay during autumn and winter revealed the presence of many diverse parasites and symbionts. A large number of crabs exhibited hemocytic infiltration and encapsulation. Parasites and symbionts identified included viruses (Baculo-B and RLV-RhVA), a rickettsia-like microorganism (RLM), an unusual strandlike organism, unidentified microsporidians and gregarines, both parasitic (Mesanophrys chesapeakensis) and symbiotic (Lagenophrys callinectes and Epistylis sp.) cilates, the nemertean Carcinonemertes carcinophila, and trematode metacercariae, some hyperparasitized by the haplosporidian Urosporidium crescens. Significant differences in disease and parasite frequencies were observed among survey periods. The prevalence of some tissue responses and parasites exhibited seasonal patterns of infection and infestation. Blue crabs, Callinectes sapidus Rathbun, are one of the most valuable commercial fisheries in Chesapeake Bay. The 1996 Maryland landings were 38 million pounds, valued at

Scaling of Calcium, Inorganic Contents, and Organic Contents to Body Mass During the Molting Cycle of the Fresh-Water Crayfish Procambarus Clarkii (Girard)

3 1 million (Maryland Department of Natural Resources, 1996). Blue crab landings fluctuate yearly (Holliday and OBannon, 1990) due to factors such as winds and currents, which influence larval transport and recruitment from the Atlantic Ocean back into Chesapeake Bay (Boicourt, 1982; Sulkin and Epifanio, 1986). Recent indications of decreased crab landings and increased fishing pressure in Chesapeake Bay have prompted legislation of conservation measures for the fishery since 1994 (Abbe and Stagg, 1996). Other factors, such as predation, food availability (Van Heukelem, 1991), and disease (Sprague, 1965; Johnson, 1983) may also affect fluctuations in crab abundance. Reduced catches or mortalities associated with diseases or parasites have been documented in several commercial crustacean fishery populations including Chesapeake Bay (Sprague and Beckett, 1966), other blue crab fisheries (Overstreet, 1978), king crabs (Paralithodes camtschatica (Tilesius)) (Kuris et al., 199 I), Tanner crabs (Chionoecetes bairdi Rathbun) (Meyers et al., 1987), and the Norway lobster Nephrops norvegicus (Linnaeus) (see Field et al., 1992), and the velvet swimming crab NeCora puber (Linnaeus) (see Wilhem and Mialhe, 1996). This study examines the prevalences of diseases and parasites in blue crabs within Chesapeake Bay in order to better understand the impact that diseases may have on blue crab populations. Numerous publications have described the diseases, parasites, and symbionts of blue crabs (Sprague, 1970; Johnson, 1978, 1983; Overstreet, 1978; Couch, 1983; Millikin and Williams, 1984; Messick and Sindermann, 1992), but most reports lack information on the prevalence of infections. I report prevalences of several diseases, parasites, and symbiont~ in blue crabs and suggest relationships with temperature and salinity. Crabs were sampled from the Maryland portion of Chesapeake Bay (Fig. 1). Crabs sampled in the winter were obtained in cooperation with the Maryland Department of Natural Resources (MDNR) annual winter dredge survey (WDS) of overwintering blue crab population densities. Crabs sampled in the autumn (ADS) were obtained as bycatch from MDNRs oyster-bar surveys. Stations sampled during the winter were chosen randomly using longitude and latitude and water depth of 1.8 m (6 ft) as required for the research vessel. Crabs were caught by dragging a 1.8-m (6-ft) dredge, lined with 13mm (0.5-in) hardware cloth, for 1 min. Crabs sampled during autumn months were a bycatch of oyster dredge tows with a 91-cm (3-ft) wide dredge (Smith and Jordan, 1993). Crabs were transported to the Cooperative Oxford Laboratory, Maryland, and placed in tanks with flowing estuarine water from the Tred Avon River for up to 24 h before dissection. MDNRs Resource Assessment Service provided mean salinity and temperature data taken for 3 water quality monitoring stations from the main stem of the bay (Fig. 1). Carapace width (CW, greatest width between the epi534 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. IX, NO. 3. IYYX Fig. 1. Maryland portion of Chesapeake Bay showing various sites where blue crabs were sampled during the autumn and winter from 1990-1992. A = sites where crabs infected with Mesanophrys chesapeakensis were found. MCB3.2, MCB4.2C, and MCB5.3 are reference salinity and temperature stations. branchial spines), sex, and maturity were assayed by morphology of the abdomen and telson (male crabs under 90mm CW were considered immature) (Millikin and Williams, 1984). Crabs from each river system were dissected, with gill, gut, hepatopancreas, epidermis, heart, hemopoietic tissue, brain, antenna1 gland, thoracic ganglion, and muscle tissues removed for histological processing (Messick, 1995). Tissues were placed either in Hellys or Bouins fixative for 18 h, embedded in paraffin, cut at 5 Fm, and stained with Mayers hematoxylin and eosin (Luna, 1968) or alcian blue (Howard and Smith, 1983). Gram (Brown and Hops, 1973), periodic acidSchiff, PAS (Howard and Smith, 19831, and acid-fast bacteria, AFB (Howard and Smith, 1983) staining techniques were also utilized. Since histological preparations included only a small portion of the whole animal, false negatives may have been recorded during this survey. Slides were examined for pathology. presence of parasites, or any abnormal histological characteristics (Johnson, 1980; Messick, 1995). Diagnoses of diseases and identification of parasites were based on light microscopy, electron microscopy (EM), and literature descriptions. Although only a presumptive diagnosis of viral infections can be made without EM analysis. light microscopy demonstration of previously published histological characteristics of viral infections which were assayed using EM (Johnson, 1984) were used to assign the type of viral infection. No biochemical analyses were performed on crab tissues from this survey. A chi-square contingency table with a = 0.05 and 56 degrees of freedom was used to determine if frequencies of the various diseases and parasites varied statistically from one survey period to the other (Steele and Torrie. 1980, p. 498). Data were further evaluated using confidence limits for percentages (Sokal and Rohlf, 1973) to determine the degree to which overall prevalence of a diease or parasite varied between survey periods. Confidence limits for zero prevalence indicated the probability that the disease or parasite may have been present in the population, but was missed due to sampling error. such as low sample numbers in relation to a large population or the small portion of tissue assayed. A total of 657 crabs were sampled from 31 sites within the Maryland portion of Chesapeake Bay (Fig. 1). The random sampling method prevented repetitive sampling, although certain river systems were sampled several times. Numbers of crabs collected. mean salinity, and temperature for three reference stations varied for each sampling period (Table l ) . Generally, northern stations had lower salinity and temperature than southern stations. In all samples combined, 60% of the crabs were male and 40% were female (Table 2); 40% of male crabs were imTable 1. Number of blue crabs dredged from Maryland portions of Chesapeake Bay and mean salinity and temperature for three reference stations during the autumn and winter from 1990-1992. WDS = winter dredge survey. ADS = autumn dredge survey. Stallon WDS 911 WDS 91 4DS 91 WDS 9 1 ADS 9 1 Number sampled 113 224 60 188 72 MCB3.2 Salinity 15.8 14.7 17.2 17.9 17.8 Temperature 1.7 6.3 17.9 4.7 16.0 MCB4.2C Salinity 21.5 17.9 23.2 21.2 17.5 Temperature 1.6 6.6 20.3 5.1 22.1 MCB5.3 Salinity 22.8 22.2 24.9 24.8 16.4 Temperature 2.8 7.2 19.5 5.6 22.8 535 MESSICK: PREVALENCE OF DISEASES, PARASITES, AND SYMBIONTS OF BLUE CRABS Table 2. Number of Callinectes sapidus collected and percentage with diseases and parasites by sex and maturity. Crabs dredged from Maryland portions of Chesapeake Bay during the winter and autumn from 1990-1992. Cond~t~on Reference number Female Male Immature Mature Number collected 257 393 381 269 Infiltration 31 3 1 27 38 Nodules 13 11 11.5 12 Gill necrosis 0 1.5 0 2 Baculo-B virus USNM 47929 3 2 3 2 RLV-RhVA USNM 47925 1 0.2 1 0 RLM USNM 47920 0 0.2 0 0.4 Strandlike USNM 47923 4 4 6 1.5 Microsporidians USNM 47914, USNM 4791 5 4 4 5 3 Mesanophrys chesapeakensis USNM 478 16 ATCC 50563 0 0 0.8 0.4 Lagenophrys callinectes USNM 47919 3 5 3 4 Episiylis sp. USNM 47919 4 7 4 8.5 Unidentified gregarine USNM 47916 17 19 17 21 Metacercariae USNM 479 18 3 7 4.5 7 Urosporidium crescens USNPC 87468, USNPC 87469 3 1.5 1 4 Carcinonemertes carcinophila USNM 177942 12 9 8 14.5 Reference number = Accession number for type slides depos~ted at either USNM = National Museum of Natural History, Smithsonian Institution, Washington. D.C.. U.S.A.: USNPC = U.S. Department of Aericulture, National Anlmal Paraslte Collection, Beltsvllle, Maryland, U.S.A.; ATCC = American Type Culture Collection, Rockv~lle, ~ a r y l i d , U S A mature, and 72% of female crabs were imtween survey periods as determined by a chimature. Insufficient numbers of infected crabs square contingency table test (x~,,,,,,, from maturity and sex categories, and indi203.529, P <0.05). Confidence limits for pervidual collection sites prevented statistical centages showed that hemocytic infiltration, analysis to determine whether significant variencapsulation, the strandlike organism, miations occurred between disease conditions crosporidians, and the nemertean Carcinoneand these groups. mertes carcinophila (Kolliker) exhibited sigThree tissue responses, two presumptive nificant differences in prevalence between at viruses, two bacterial agents, six protozoans, least two survey periods (Figs. 2-4). Focal unidentified metacercariae of digenetic tremagill lesions, RLV-RhVA, Baculovirus, RLMs, todes, and one ne

Standard Rate of O2 Uptake and Body Size in the Crayfish Pacifastacus Leniusculus (Dana, 1852) (Decapoda: Astacidae): Intra- Versus Interspecific Relations in Crustaceans

ABSTRACT Allometric relationships were derived for calcium, inorganic contents, and organic contents of the crayfish Procambarus clarkii (0.012-33 g) at various stages in the molting cycle. Whole body parameters were measured at intermolt, ecdysis, and postmolt (1 week); determinations were also made on shed exuviae and gastroliths. Significant linear relationships on log-transformed data were obtained for all parameters. Scaling exponents for mineral content varied from 0.93-1.27, agreeing closely with scaling of supportive tissue mass in a range of species possessing both exo- and endoskeletons. Regression relationships were interpolated for hypothetical 1-and 30-g crayfish. Larger crayfish demineralize their cuticle more effectively prior to ecdysis; even so, exuviae constitute an avenue for significant mineral loss (30 cf. 50%). They also store less mineral between molts, excreting increasing amounts into the external water. Gastroliths are the major form of mineral storage especially in small crayfish (74 cf. 57%). Large postmolt crayfish are more mineral deplete (15%) than small crayfish (35%). Within 1 week of postmolt, 1-g crayfish have surpassed intermolt mineral content, by branchial uptake from external water. Their rapid rate of remineralization is commensurate with their increased molting frequency. In the same time period, larger crayfish have recovered only 30% of their intermolt mineral content. Continued branchial uptake, together with ingestion of shed exuviae or other food sources, would restore mineral balance. Irrespective of size, crayfish lose 15% organic matter in the exuviae at ecdysis. In the absence of food, postmolt crayfish draw on organic reserves for energy.

THE EFFECTS OF TEMPERATURE AND WATER AVAILABILITY ON ION AND ACID-BASE BALANCE IN HEMOLYMPH OF THE LAND HERMIT CRAB COENOBITA CLYPEATUS

ABSTRACT The allometric relation for standard O2 uptake rate (MO,) was investigated in the crayfish P. leniusculus ranging from 0.0334-69.40 g at 12°C. When converted to watts the relationship had a mass exponent of 0.789 and a mass coefficient of 0.282 (intercept at 1 kg). Another intraspecific study on kelp crabs (Weymouth et al., 1944) had an identical mass exponent, but different mass coefficient which may be species specific. Interspecific analysis of published data for aquatic decapods produced a significantly higher mass exponent (0.877) and a lower intercept (0.128). The value of intra- versus interspecific allometric analysis is discussed in the context of a prospectus for future investigations.

Related Changes in Hemolymph Acid-Base Status, Electrolytes, and Ecdysone in Intermolt Crayfish (Procambarus clarkii) at 23 degrees C during Extracellular Acidosis Induced by Exposure to Air, Hyperoxia, or Acid

Temperature acclimation (18-30°C) and dehydration (to 86% of initial mass) are two problems frequently encountered by the land hermit crab, Coenobita clypeatus. Their individual and combined effects on hemolymph ion and acid-base status were assessed. With free access to 10% SW, crabs maintained a constant degree of hydration, with hemolymph marginally hypo-osmotic to full strength SW. Increased acclimation temperature produced a reduction in pH, characteristic of ectotherms and consistent with maintenance of relative alkalinity which was accomplished by an elevation of CO2 tension (P,CO2). Hyperactivity resulted in some spillage of shell water and affected Cl- balance. Under water deprivation, evaporative loss declined approximately exponentially and was negatively correlated with body mass. Hemolymph osmolality and electrolyte levels were significantly increased, ionic imbalance contributing largely to the hemolymph acidosis. Hemoconcentration was less marked when combined with temperature acclimation. ...

Physiological effects of a gill barnacle on host blue crabs during short‐term exercise and recovery

ABSTRACT The relationships between hemolymph acidic-basic equivalents (pH, PCO2, and [HCO3, + C032-]), electrolytes (Na, K, Ca, Mg, and Cl), and ecdysone concentration were investigated in the crayfish Procambarus clarkii at 23°C during extracellular acidosis resulting from: (1) 24-h aerial exposure, (2) 96-h hyperoxic exposure (PO2 > 550 mm Hg), or (3) 96-h acid exposure (pH 4.0). A control series failed to reveal any significant effects of repetitive hemolymph sampling. In air, crayfish developed an initial (3-h) respiratory acidosis that was completely compensated within 24 h by metabolic base [HCO3 + CO32 ] accumulation. Circulating Ca and Cl both decreased at 24 h, while K increased. In this case, there was evidence that acid-base balance was corrected by ion exchange with the intracellular compartment. Hyperoxia was characterized by an initial (3-h) respiratory acidosis followed by a metabolic acidosis. The combined acidosis remained uncompensated, and circulating ecdysone decreased after 24 h. Acid exposure produced a purely metabolic acidosis that was partially corrected by a respiratory alkalosis between 48 and 72 h and was accompanied by an increase in circulating ecdysone. Ca and K decreased. Collectively, the experiments established a relationship between extracellular ecdysone and pH. Meanwhile, Ca remained relatively constant in all 3 treatments.

Physiological Adaptations in Decapodan Crustaceans for Life in Fresh Water

The effects of infestation by an ectocommensal gill barnacle, Octolasmis muelleri, on the blue crab, Callinectes sapidus, were assessed by measuring respiratory and hemolymph parameters in barnacle‐infested and uninfested crabs during short‐term exercise and recovery. At rest, uninfested crabs had lower heart rates (78 beats min‐1) and ventilation rates (74 beats min‐1) than moderately infested crabs (93 beats min‐1 and 92 beats min‐1 respectively) and heavily infested crabs (104 beats min‐1 and 123 beats min‐1 respectively). During exercise and recovery these differences disappeared as all groups of crabs elevated both rates to near maximal levels. Hemolymph O2 concentrations, O2 tensions, pH and [lactate] were not different for the three groups of crabs, but, heavily infested crabs had a greater a‐v difference in Po2 than the other groups of crabs during exercise, as well as a significant a‐v difference in pH and [lactate] during exercise. The overall minimal disturbance to the crabss hemolymph caused ...

Some behavioural and physiological responses of the ascidian Styela plicata (lesueur) during acclimation to low salinity

In recent years, there have been several excellent review articles on aspects of decapod crustacean physiology including ventilation and circulation (Taylor 1982; Cameron and Mangum 1983; McMahon and Wilkens 1983; McMahon and Burggren 1988), acid-base balance (Truchot 1983; Cameron 1986), gas transport (McMahon 1981; Mangum 1983), and osmoregulation (Mantel and Farmer 1983). These have focused predominantly on the marine decapods that constitute the majority (90%) of crustacean species. While research has steadily continued on freshwater (FW) decapods such as the crayfish, this information is typically “lost” among the wealth of information on marine species. This is regrettable because FW species exhibit some of the most sophisticated physiological mechanisms among crustaceans. To name but a few, they have well-developed branchial ion uptake mechanisms, a kidney with the unique ability to produce dilute urine, and adaptations for molting and postmolt calcification in an inhospitable environment. Furthermore, the physicochemical properties of FW dictate that environmental challenges such as hypoxia, hyperoxia, hypercapnia, and aerial exposure, as well as man-made problems such as acidification, are experienced more routinely by FW as opposed to marine species. In summary, therefore, it would appear that FW decapods deserve separate recognition.

Extracellular and intracellular acid‐base regulation in crustaceans

The sessile ascidian, Styela plicata (Lesueur, 1823), commonly inhabits areas of fluctuating salinity; consequently, it must either tolerate or compensate for perturbations in body volume caused by environmental salinity changes. This study examines siphon closure as an avoidance response, and net effluxes of total ammonia and ninhydrin positive substances (NPS) during the first 48 h of acclimation of S. plicata to 20‰ sea water. Experimental animals in 20 ‰ were compared with a control group in full strength sea water (35‰). Typically, siphons of experimental tunicates remained closed until 6–8 h, isolating the animals from the environment. Water content in experimental tunicates was elevated 2–5% above control levels after 8 h and remained elevated in the soft tissue. Experimental NPS net efflux increased by 12 h and remained elevated. After 24 h, experimental net efflux of ammonia increased. The increase in experimental NPS net efflux is probably due to the excretion of intracellular organic osmolytes,...