Cellular responses to increasing Cd concentrations in the freshwater crab,<Emphasis Type="Italic"> Potamonautes warreni</Emphasis>, harbouring microbial gill infestations

We investigated the uptake, transport, storage and defence mechanisms in the freshwater crab, Potamonautes warreni, harbouring microbial gill infestations and exposed to increasing chronic (0.2, 0.5, 1.0 mg l^–1) and acute (2.0 mg l^–1) cadmium (Cd) concentrations under controlled laboratory conditions over a period of 21 days. Transmission electron microscopy and X-ray microanalysis revealed that the microbial gill fauna was eliminated on exposure to 0.2 mg Cd²⁺ l^–1 and that Cd became increasingly adsorbed and incorporated into lamellar crystal deposits and permeated the cuticle of the gills of P. warreni. Degeneration of the apical membrane infoldings and vacuolation of epithelial cells occurred concurrently with pinocytosis, endocytosis and pronounced phagocytotic activity in the epithelia and haemal canal of the gills. Elevated Cd exposures (0.5 or 1.0 mg l^–1) resulted in the swelling and dissociation of mitochondrial outer membranes together with an increase in transport of Cu, Cl and S by haemocytes in the haemal canal to epithelial tissues depleted in these elements. Cd also accumulated in tightly coiled concentric membrane whorls in the haemal canal, whereas the highest concentrations of Cd were found within aggregates of lysosome-like bodies in cuticulin-secreting cells of the gill stem. Chronic exposure to Cd induced increased fatigue and mild uncoordinated motor activity. In contrast, at an acute exposure of 2.0 mg l^–1 over 48 h, P. warreni showed a time-specific rapid loss of motor function, although only mild cellular lesions occurred in the gill tissues. The significance of cellular changes in the gill epithelia and altered motor activity of P. warreni with increased waterborne Cd are discussed as potential biomarker responses in monitoring aquatic pollution.     

SOME ASPECTS OF THE ECOLOGY OF THE FRESHWATER CRAB (POTAMONAUTES PERLATUS MILNE EDWARDS) IN THE UPPER REACHES OF THE BUFFALO RIVER,EASTERN CAPE PROVINCE,SOUTH AFRICA.

Summary

Freshwater crabs (Potamonautes perlatus) are the largest naturally occurring invertebrates in southern African rivers. The ecology of these animals in South African riverine ecosystems is little understood. This study investigates some aspects of the population and feeding ecology of P. perlatus in the upper reaches of the Buffalo River. The densities of crabs (carapace width larger than 25 mm) at two sites in the river ranged between 1.72 and 5.25 crabs m², higher than previously recorded for freshwater crabs in rivers in southern Africa and southern Italy. Twenty-four hour observations revealed that P. perlatus has a nocturnal habit. The diet of P. perlatus was established by examination of the contents of the fore-gut. Crabs with a carapace width smaller than 40 mm fed predominantly on aquatic invertebrates while larger crabs fed on allochthanous material (leaf litter), detritus and algae. Through feeding, crabs reduced the surface area of leaves in the stream by 99.95%.     

Interspecific differences in Zn,Cd and Pb accumulation by freshwater algae and bryophytes

The relationships between the concentrations of zinc, cadmium and lead in aquatic plants and the concentrations of these metals in the ambient water have been compared for three algae (Lemanea fluviatilis, Cladophora glomerata, Stigeoclonium tenue), one liverwort (Scapania undulata) and three mosses (Amblystegium riparium, Fontinalis antipyretica, Rhynchostegium riparioides). The data to establish these relationships are all based on our own studies, some published already, some here for the first time. They come from a wide range of streams and rivers in Belgium, France, Germany, Ireland, Italy and the U.K. There were significant bivariate positive relationships between concentrations of Zn, Cd and Pb in water and plant for all species except Cd and Pb in Stigeoclonium tenue. When relationships were compared using datasets with total or filtrable metals in water, most differences were slight. However there were marked differences both between species and between metals. Comparison for the seven species of Zn in the plant when aqueous Zn is 0.01 mg l^–1, a concentration at which all seven were found, shows that the four bryophytes had the highest concentrations; however the two green algae had steeper slopes (representing change in concentration in plant in response to change in aqueous concentration). Lemanea fluviatilis had a slope closer to that of the bryophytes, but the concentration was about one order of magnitude lower. All seven species were found at a concentration of 0.01 mg l^–1 Pb, and at this concentration there were almost two orders of magnitude difference between the species which accumulated the most (Scapania undulata) and the one which accumulated the least (Cladophora glomerata). The steepest slope was however shown by C. glomerata.When multiple stepwise regression was applied, the aqueous metal under consideration was the first variable extracted in only nine of the 21 regressions. However one of the other heavy metals (aqueous or accumulated) was extracted first in all but one of the other regressions, presumably because the occurrences of Zn, Cd and Pb were strongly cross-correlated. The principal non-heavy metal factor extracted for Zn and Cd, but not Pb, was aqueous Ca. The relevance of these results to the use of aquatic plants for monitoring heavy metals is discussed.     

Evaluation of the sample size used for the rapid bioassessment of rivers using macroinvertebrates

Experiments were designed to investigate selective predation by medium (40–55 mm carapace width: CW) and large (55–70 mm CW) Carcinus maenas when feeding on four bivalves of contrasting shell morphology. Size-selection was examined by presenting individual crabs with a wide size range of Mytilus edulis, Ostrea edulis, Crassostrea gigas and Cerastoderma edule. Medium-sized crabs preferred mussels 5–15 mm shell length (maximum shell dimension: SL) and cockles 5–10 mm SL, whereas large crabs preferred mussels 15–25 mm and cockles 10–20 mm SL. Crabs generally showed no preference for any particular size of either oyster species. Species-selection was examined by presenting individual crabs with paired combinations of the four bivalves in various proportions. When offered mussels and oysters simultaneously, both size categories of crabs consistently selected mussels, and food choice was independent of prey relative abundance. By contrast, C. maenas selected mussels and cockles as expected by the frequency in which each size category of crab encountered the preferred size ranges of prey. Crab preference clearly paralleled the rank order of prey profitability, which in turn was mainly determined by prey biomass, suggesting that active selection takes place at some point of the predation cycle. Experiments with epoxy resin models showed that initial reluctance of crabs to attack oysters was not associated with the ultimate energy reward. Moreover, they suggest that foraging decisions are partly based on evaluations of overall prey shape and volume, and that the minimum dimension of the shell constitutes an important feature which crabs recognise and associate with prey value.     

Heavy metal concentrations in common freshwater snails of Azraq Oasis,Jordan

Heavy metal concentrations in three freshwater snails, an aquatic plant, sediment, and water from Azraq Oasis pools in the Jordanian desert were measured by atomic absorption spectrophotometry. There were significant differences in metal accumulation among snail species. These snails are ranked according to their metal accumulation capacity in the order: Melanoides tuberculata > Melanopsis praemorsa > Theodoxus jordani. Although there were no significant differences among the size classes of these snails in metal concentrations, larger snails contained generally higher levels of metals than the smaller ones. The concentration factors for the selected snails exceeded 10³, while it ranged from 0.1–10.2 × 10³ for Typha angustata plants. Among sampling sites, metal concentrations in M. praemorsa, T. angustata, sediment, and water were not significantly different, except for Fe in M. praemorsa which was highest at station 3, and Cd and Cr which were highest in water and sediment of station 4. The seasonal variation in metal content was found to be species and metal-dependent.     

Presence of itaconic acid in the hemolymph and tissues of the freshwater crab, Potamonautes warreni Calman

Itaconic acid was detected in hemolymph, hepatopancreas, gill and muscle tissue of the freshwater crab, Potamonautes warreni. This metabolite has previously only been found in unicellular organisms and fungi. The measured itaconic acid is either being manufactured by the crab itself or present due to infestation by unicellular organisms or fungi.     

Burrow Architecture of the Ghost Crab Ocypode ceratophthalma on a Sandy Shore in Hong Kong

The ghost crab Ocypode ceratophthalma (Pallas) creates burrows of variety shapes at different ages. Juveniles (mean carapace length 11 mm) produced shallow J-shaped burrows, which incline vertically into the substratum (mean depth 160 mm). Larger crabs (17–25 mm carapace length) have Y-shaped and spiral burrows (mean depth 361 mm). These Y-shaped burrows have a primary arm, which extends to the surface forming the opening, and a secondary arm which terminates in a blind spherical ending. The two arms join in a single shaft and end with a chamber at the base. The secondary arms and chambers are believed to be used for mating or as a refuge from predation. The spiral burrows have spiral single channel ending in a chamber. Older crabs (mean carapace length 32.6 mm) had simple, straight single tube burrows, which inclined into the substratum at mean of 73° and had a mean depth of 320 mm. During summer daytime periods, the burrows shelter the crabs from heat and desiccation stress. The sand surface temperature at the burrow opening was ~48 °C but temperatures inside the burrows can drop to 32 °C at a depth of 250 mm. Variation in the burrow architecture with crab age appears to be related to the crab’s behaviour. Juvenile crabs have smaller gill areas and move out of the burrows regularly to renew their respiratory water and, as a result, they do not need a deep burrow. Larger crabs, in contrast, can tolerate prolonged periods without renewing their respiratory water and therefore create deeper and more complex burrows for mating and refuges.     

An experimental study of 226Ra and 45Ca accumulation from the aquatic medium by freshwater turtles (fam. Chelidae) under varying Ca and Mg water concentrations

Snapping turtles Elseya dentata (Gray) from Magela Creek, Northern Territory, were exposed under laboratory conditions for up to 30 days to waters resembling the inorganic composition of Magela Creek water during the Wet season, with background and elevated Ca and Mg concentrations, that were labelled with ²²⁶Ra and ⁴⁵Ca. The resulting concentrations of ⁴⁵Ca in muscle, skin, gut, liver, shell bone and leg bone of E. dentata equilibrated or approached equilibrium by 12–18 days. Among the experiments, the concentrations of ⁴⁵Ca in all six tissues were inversely related to turtle mass. An increase in the Ca water concentration by a factor of 15 increased the ⁴⁵Ca concentration in all six tissues. The arithmetic factors of increase in the concentration in each tissue were proportional or more than proportional to the factor of increase in Ca water concentration; this factor was highest for muscle tissue (26.6). An increase in the Mg water concentration by a factor of 48 reduced the ⁴⁵Ca concentration in all tissues except skin where it increased. The concentration of ²²⁶Ra in each tissue (except the gut) was positively related to its ⁴⁵Ca concentration and inversely related to turtle mass in muscle, skin and liver. With the exception of the skin, the increased Ca water concentration did not reduce the ²²⁶Ra in the tissues but increased the ²²⁶Ra concentration in bone and muscle. The increased Mg water concentration had an inverse effect on the ²²⁶Ra concentrations in all tissues except shell. With the exception of the skin the effects of increased Ca and Mg water concentrations and turtle size on ²²⁶Ra concentrations in the tissues of E. dentata were similar to their effects on ⁴⁵Ca tissue concentrations, indicating the similar metabolic behaviour of ²²⁶Ra and ⁴⁵Ca in E. dentata.Exposures of the species Elseya latisternum (Gray), Emydura signata (Ahl) and Chelodina longicollis (Shaw), which are the same or closely related to species reported to occur in Magela Creek, to ⁴⁵Ca-labelled Sydney tap water for 7 days demonstrated their ability to also accumulate ⁴⁵Ca from their aquatic medium. The patterns of ⁴⁵Ca concentrations in the tissues of these species indicated that they were inversely related to turtle mass, as demonstrated in E. dentata. The concentrations of ⁴⁵Ca accumulated in the tissues were also comparable to those found in single specimens of E. dentata and E. victoriae (Gray) that were exposed for 7 days to simulated Magela Creek water. The data also indicated the larger long-necked C. longicollis accumulated less ⁴⁵Ca per gram of tissue than similar-sized, short-necked species E. signata and E. latisternum, suggesting that long-necked turtles from Magela Creek would accumulate less ²²⁶Ra from their aquatic medium than similar-sized short-necked species.The capacity of E. dentata to accumulate ²²⁶Ra from the aquatic medium is about two orders of magnitude less than that of the tissue of the freshwater mussel Velesunio angasi (Sowerby) exposed under similar experimental conditions.     

Functional genomics and sexual differentiation in amphibians

To succeed on land rather than in water, crabs require a suite of physiological and morphological changes, and ultimately the ability to reproduce without access open water. Some species have modified gills to assist in gas exchange but accessory gas exchange organs, usually lungs, occur in many species. In accomplished air-breathers the lung becomes larger and more vascularised with pulmonary vessels directing oxygenated haemolymph to the heart. The relative abundance of O₂ in air promotes relative hypoventilation and thus an internal hypercapnia to drive CO₂ excretion. Land crabs have a dual circulation via either lungs or gills and shunting between the two may depend on respiratory media or exercise state. During their breeding migration on Christmas Island Gecarcoidea natalis maintained arterial Po₂ by branchial O₂ uptake, while pulmonary O₂ pressure was reduced; partly because exercise doubled relative haemolymph flow through the gills. Related species rely on elevated haemocyanin concentration and affinity for O₂ to assist uptake but this compromises unloading at the tissues and thus the aerobic scope of tissues. Aquatic crabs exchange salt and ammonia with water via the gills but in land crabs this is not possible. Birgus latro has adopted uricotelism but other species excrete ammonia in either the urine or as gas. Land crabs minimise urinary salt loss using a filtration-reabsorption system analogous to the kidney. Urine is redirected across the gills where salt reabsorption occurs in systems under hormonal control, although in G. natalis this is stimulatory and in B. latro inhibitory. While crabs occupy a range of habitats from aquatic to terrestrial, these species do not comprise a physiological continuum but across the crab taxa individual species possess appropriate and specific physiological features to survive in their individual habitat.     

Carapace movements associated with ventilation and irrigation of the branchial chambers in the semaphore crab,Heloecius cordiformis (Decapoda: Brachyura: Ocypodidae)

Summary Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water, the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial air-breathing mangrove crab, sequentially depresses and elevates its carapace relative to its thorax (0.5–1 mm excursion) in a regular pump-like manner. In quiescent crabs each carapace-pumping cycle lasts about 4 s; carapace depression takes 3 s and elevation 1 s. Carapace movements are brought about by pressures generated within the branchial chambers by the scaphognathites, probably in combination with carapace muscles. Carapace movements are associated with bilaterally synchronised scaphognathite activity. Unilateral scaphognathite activity was not observed. During normal forward recirculation of branchial water the scaphognathites beat at about 1.5 Hz (slow-forward pumping) and the lungs (epibranchial chambers) are not ventilated. In Heloecius, the lungs are not physically separated from the gills below by an anatomical barrier. Lung ventilation is accomplished during the following sequence of events: the carapace is lowered and the scaphognathites pump in a fast-forward mode at about 2.8 Hz. This activity preferentially pumps air out of the lungs and generates suction within the branchial chambers (4–10 cm H₂O below ambient) which draws water from external body surfaces into the hypobranchial space below and around the gills. At the end of the carapace's downward travel the scaphognathites switch from fast-forward to fastreverse beating at about 4 Hz. This pumps air into the lungs and the carapace elevates. As a result, during carapace elevation the water which had previously been drawn into the branchial chambers by fast-forward pumping activity is released and flows out between the legs and into the abdominosternal cavity. When the carapace reaches its original resting or up position the scaphognathites switch from fast-reverse to slowforward beating to re-establish water recirculation through the branchial chambers. This cycle is subsequently repeated. In stationary crabs, there are 2 carapace-pumping cycles per minute, increasing to 14 per minute in active crabs (walking). When water is absent, the lungs are preferentially ventilated by slow-reverse scaphognathite pumping activity. Carapace movements do not occur in the absence of branchial water. Carapace pumping is thought to provide a mechanism which permits the scaphognathites to ventilate the lungs in the presence of recirculating branchial water, without this water interfering with lung ventilation or being lost to the environment.Abbreviations FF, FR, SF, SR fast-forward, fast-reverse, slowforward, slow-reverse scaphognathite pumping - MEA Milne Edwards aperture     

Aerial and Aquatic Respiration in the River Crab Potamonautes Warreni Calman with Notes on Gill Structure

Summary

The oxygen consumption rate (?O₂) for Potamonauteus warreni Calman (= Potamon warreni (Calman) kept in 25 °C water was 34,4 μmol 1^?1 O₂ kg^?1 and after 72 hours in 98% R.H. air the rate was 31,9 μmol 1^?1 O₂ kg^?1 min^?1. The ?O₂ values for each of the two groups are not significantly different (P > 0,05). The partial oxygen tension of pre-branchial (v = venous) haemolymph (P_vCO₂) is 15,3 mm Hg in water and 13,0 mm Hg in air); partial carbon dioxide tension of pre-branchial (v) haemolymph (P_vCO₂) is 13,2 mm Hg in water and 13,0 mm Hg in air); the total carbon dioxide concentration in pre-branchial (v) haemolymph (C_vCO₂) tot. is 12,3 mmol 1^?1 in air and 13,9 mmol 1^?1 in water) are not significantly different for the two groups (P > 0,05). The haemolymph pH and the lactate concentration for crabs in water was found to be 7,51 and 0,38 mmol 1^?1 respectively. No significant differences were found in pre-branchial haemolymph oxygen tension, carbon dioxide tension, total carbon dioxide content, haemolymph pH, lactate level, chloride concentration, P₅₀ and haemocyanin-oxygen cooperativity in control crabs kept in water, and experimental crabs held in air for 72 hours. The chloride concentration, (327,0 mmol 1^?1) for crabs kept in water does not differ from that of crabs held in air for 72 hours but is at least 15% higher than the sodium concentration (255 mmol 1^?1) for crabs kept in water. The gill surface area is 520 mm² g^?1 wet body mass; on average 9,2 gill platelets (lamellae) can be found on a gill length of one millimetre. Each lamella is spaced 60–70 μm apart, each with a thickness of 30–40 μm. It is concluded that P. warreni may be described as a truly amphibious fresh-water crab.     

Concerning the problem of carcinophilia of <Emphasis Type="Italic">Careproctus</Emphasis> species (Scorpaeniformes: Liparidae) in the North Kurils

Along the east coast of North Kurils, the egg deposits of Careproctus snailfishes (Scorpaeniformes: Liparidae) were revealed in the gill cavity of 9.9% of all golden king crabs, mostly in individuals with carapace of 61–80 mm width (61.6%). The number of Careproctus eggs in the gill cavity of crabs increased with the increase of the carapace width. In fact, 97.0% of the crabs had such egg deposits only at one side of their carapaces. Most of the egg deposits, apparently, belonged to C. cypsellurus and C. furcellus. The number of crabs with egg deposits was related to the number of post-molt individuals. Evidently, egg depositing by Careproctus snailfishes out of the gill cavity of crabs is a rather widespread phenomenon.     

Ventilation of the branchial chambers in the amphibious West African freshwater crab,Sudanonautes (Convexonautes) aubryi monodi (Balss, 1929) (Brachyura,Potamonautidae)

The anatomy of the respiratory system of the savanna-zone African freshwater crab, Sudanonautes (Convexonautes) aubryi monodi [Balss, 1929], has been examined and has been found to be adapted for both aerial and aquatic gas exchange. The activities of the scaphognathites and the directions of flow of the ventilatory stream have been recorded in stressed, active and resting specimens during their exposure to a wide range of conditions from deep water to dry land.Ventilation of the branchial chambers during aquatic gas exchange in Sudanonautes kept in deep water is shown to consist of a rapid, predominantly forward water flow similar to that of fully-aquatic species. Ventilation of the branchial chambers during aerial gas exchange in Sudanonautes on land is shown to consist of a relatively slow forward air flow. This flow is continuous in post-operative crabs, pulsatile in active crabs and completely immobile in resting crabs.A second method of ventilation of the branchial chambers during aerial gas exchange is shown to consist of a pulsatile reversed air flow. This occurs (1) when Sudanonautes is kept in very shallow water and active or stressed; (2) when it has recently moved on to land; and (3) when it is completely immersed and exhibiting aerial gas exchange under water. The unusual phenomenon of aerial gas exchange under water is reported here for the first time in any species of crab.Bimodal ventilation of the branchial chambers occurs in stressed or active crabs partly immersed in shallow water. This consists of an alternation between forward water flow and reversed air flow.The morphology of the branchial chambers in Sudanonautes, and observational data on the patterns of ventilation of the branchial chambers, are discussed in relation to those described for other air-breathing decapod crustaceans.     

Role of Life History Strategy in the Colonisation of Western Australian Aquatic Systems by the Introduced Crayfish <Emphasis Type="Italic">Cherax destructor</Emphasis> Clark, 1936

The presence of the yabbie Cherax destructor in a number of wild aquatic systems in the Pilbara and Southwest Coast Drainage Divisions of Western Australia is documented. This is of great concern as all native freshwater crayfishes in Western Australia are endemic and restricted to the southwest, while the Pilbara Division has no native species. An introduced population of C. destructor was sampled monthly from the Hutt River (Pilbara Drainage Division) for determination of life-history and reproductive biology in a wild aquatic system in Western Australia for the first time. Proliferation in that system was attributed to specific traits including: attaining first maturity at the end of its first year of life; a protracted spawning period (July–January); relatively high mean ovarian fecundity of 210.2 (±9.24 S.E.); and a rapid growth rate (curvature parameter K = 0.78 and asymptotic orbital carapace length OCL_∞ = 51.25 mm ascertained from a seasonal von Bertalanffy growth curve) that was comparable to the larger sympatric marron Cherax cainii in this system. The life-history characteristics of C. destructor in the Hutt River were typical of many other invasive crayfish species and it has the potential to impact the unique aquatic ecosystems and the endemic freshwater crayfish species of the region.     

Carapace movements aid air breathing in the semaphore crab,Heloecius cordiformis (Decapoda: Brachyura: Ocypodidae)

Summary While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial airbreathing mangrove crab, sequentially depresses and elevates its carapace in a regular pump-like manner. The functional role of these carapace movements in aerial oxygen consumption is investigated. Carapace immobilisation (reversible and non-injurious) did not appear to affect branchial water circulation. In dry crabs (branchial water removed) carapace immobilisation had no effect on the rate of oxygen consumption (VO₂), heart rate or whole-body lactate (WBL) levels. In wet crabs (with branchial water) carapace immobilisation caused VO₂ to drop by 38% from 81 to 46 l O₂ · g^-1 · h^-1, heart rate to decline by 32%, from 2.5 to 1.7 Hz, and WBL levels to increase over 2.5-fold, from 0.27 to 0.67 mg · g^-1, after 3 h of carapace immobilisation. The (VO₂) of carapace-immobilised crabs with branchial water was similar to lung-occluded crabs with branchial water. Severe hypoxia induced physiological responses similar to those of carapace-immobilised crabs with branchial water. After 3 h of severe hypoxia, heart rate had declined by 80%, from 2.2 to 0.43 Hz, and the incidence of carapace pumping slowed by 85%, from 2.4 to 0.37 cycles · min^-1. It is concluded that in the absence of carapace movements branchial water in some way inteferes with lung ventilation. Under normal circumstances water circulation and lung ventilation are mutually exclusive processes (due to their singular dependence on the scaphognathites), yet in Heloecius these processes must be carried out simultaneously. Carapace movements may alleviate this conflict.Abbreviations FF, FR, SF, SR fast-forward, fast-reverse, slow-forward, slow-reverse scaphognathite pumping - MEA Milne Edwards aperture - VO₂ rate of oxygen consumption - WBL whole-body lactate     

Concentrations of zinc in Barbus marequensis from the lower Olifants River, Mpumalanga, South Africa

Zinc was detected in all the tissues examined, but in variable concentrations. The highest zinc concentrations were detected in the skin and ovaries. These zinc concentrations also differed significantly from the concentrations in the other tissues. The bioaccumulation pattern of zinc in the fish was determined as: skin >ovaries>liver>gills>vertebrae>testes>hindgut>foregut contents >kidney=foregut>hindgut contents>muscle>blood>fat>bile.Although significant differences (P<0.05) between localities were detected no clear trend as to where the highest bioaccumulation had occurred, could be established. Significant seasonal differences were detected, but it was not always the same tissue that indicates these seasonal differences. The zinc concentrations detected in the fish suggest no serious zinc pollution in the lower Olifants River. Zinc levels detected in some of the tissues might indicate chronic exposure, causing possible sub-lethal effects. However, this should be investigated before final conclusions can be made.     

Heavy metals in relation to the biology of the mummichog, Fundulus heteroclitus

Heavy metal levels of cadmium, copper, mercury, manganese, and zinc were examined in the mummichog, Fundulus heteroditus from industrialized and non-industrialized environments. With one exception, the environment with the highest trace metal in its waters, had the fishes with the highest metal concentration. Except for mercury, the concentration factor varied inversely with the metal concentrations of the fish and water, suggesting a possible regulatory mechanism for metals in the tissues of mummichogs from environments with high metal concentrations. There was an inverse relationship between standard length and concentrations of zinc, manganese, copper and cadmium in whole male and female fishes. The viscera contained significantly greater concentrations of these metals than somatic muscle tissue. There were also significant differences between males and females with respect to whole-body zinc and copper concentrations, but no sex differences for manganese and cadmium.     

Multi-biomarker responses after exposure to organophosphates chlorpyrifos in the freshwater mussels Unio tigridis and snails Viviparous benglensis

Effects of chlorpyrifos (CPF) on soft tissues of mollusks, Unio tigridis and Viviparous benglensis, have not been studied for biochemical and molecular traits. Therefore, the changes of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), malondialdehyde (MDA), acetylcholinesterase (AChE), and DNA damage in these mollusks were assessed during 21-day exposure to three concentrations of CPF. The results showed that SOD and CAT enzymes in the two mollusk species decreased with highest CPF concentration, while MDA significantly increased with highest CPF concentration. AChE concentrations also showed a clear reduction in soft tissues of both mollusks. DNA damage parameters showed significant differences between controls and three CPF concentrations for each parameter measured in the digestive gland of U. tigridis; and for V. bengalensis significant differences were observed between controls and highest two concentrations of CPF for comet length and tail length. CPF has the ability to prevent reproduction status for the snail V. bengalensis compared to the controls. In this study, we can conclude from the significant changes occurring in the concentrations of CAT, SOD, MDA, AChE, and DNA damage that the concentrations of these biomolecules in the soft tissues of the mussel and snail can be considered suitable biomarkers for a sublethal exposure and/or effects of CPF at the tested concentrations, and we can then use it in biomonitoring of water bodies.     

Comparative life histories and microhabitat use in three sympatric sculpins (Cottidae:Cottus) in northeastern California

Synopsis Life histories of three sculpins endemic to the Pit River system, northeastern California, are detailed.Cottus pitensis is widely distributed throughout the drainage. This species is typically found in rapidly flowing, shallow water on coarse substrate. It grows to a large size, >100 mm, and lives to 5 years. Spawning occurs annually, in early spring. Fecundity is relatively low, <320 oocytes.Cottus asperrimus is restricted to a large population in Fall River and smaller concentrations in Hat Creek and Pit River. It is a relatively small fish, <80 mm, and lives to 5 years. It occurs in deep, slow-moving, often spring-fed streams, typically on fine substrates. Spawning lasts from autumn to early spring. Males establish nests on hard substrates and guard several clutches of eggs. Fecundity ranges from 140–580 oocytes.Cottus klamathensis macrops is relatively rare in the drainage. The largest concentration is in the Hat Creek system, smaller populations exist in Fall River and Pit River. This sculpin is found on coarse substrate, often where aquatic vegetation is abundant. It is typically found in slow, relatively shallow water. It grows to >100mm and lives to 5 years. Males guard eggs during the short spawning season beginning in late winter. Fecundity in this species reaches a maximum of 650 oocytes. Life history strategies vary within the genus, yet the life histories of these sculpins are more similar to each other than they are to many of their congeners. This within-group similarity may have resulted from exposure of all three species to similar environmental pressures. This is predicted by life-history theory.     

Instream distributions and feeding habits of two species of sleeper, <Emphasis Type="Italic">Eleotris acanthopoma</Emphasis> and <Emphasis Type="Italic">Eleotris fusca</Emphasis>, in the Teima River,Okinawa Island

The instream distributions and feeding habits of two species of sleeper, Eleotris acanthopoma and E. fusca, were studied in the Teima River on Okinawa Island, southern Japan. Both adult fishes inhabited the river, but their distribution patterns were found to be different. The distribution of E. acanthopoma was from the tidally influenced area to the lower part of the freshwater area, whereas E. fusca was distributed almost entirely in the freshwater area. They were found to coexist at the upper limit of the tidally influenced area and the lower part of the freshwater area. Their feeding habits were clearly different, although both species were carnivorous. Eleotris acanthopoma fed mainly on crabs in the tidally influenced area and on aquatic snails in the freshwater area, where they coexist with E. fusca. In contrast, E. fusca fed mainly on shrimps in the freshwater area. Their coexistence may result from the difference in their feeding habits.