Showing papers on "Gill published in 1996"

Gill Damage in the Freshwater Fish Gnathonemus Petersii (Family: Mormyridae) Exposed to Selected Pollutants: An Ultrastructural Study

Abstract: The histopathological effects of three heavy metals, cyanide and atrazine on the gill tissues of the mormyrid fish, Gnathonemus petersii, were determined primarily by electron microscopy. Replicate...

Accumulation of HSP70 in juvenile and adult rainbow trout gill exposed to metal-contaminated water and/or diet

Abstract: The accumulation of heat shock cognate (hsc)/heat shock protein (hsp) 70 was measured in gill and liver from juvenile and adult rainbow trout (Oncorhynchus mykiss) exposed to waterborne metals and/or fed a metal-contaminated diet. These experiments are part of a larger study in which physiological responses were documented in adult and juvenile rainbow trout after exposure to food-borne and/or waterborne metals for 21 d. Western blot analyses were used to measure the accumulation of hsp70 and hsc70. Hsc/hsp70 levels were significantly increased in gills of juveniles exposed to metals, in both water and food. The importance of metals in the diet as well as the water was confirmed for the juveniles. Significant increases in hsp/hsc70 could not be demonstrated in the adults.

Induction of micronuclei in haemocytes and gill cells of zebra mussels, Dreissena polymorpha, exposed to clastogens

Abstract: Zebra mussels, Dreissena polymorpha, were exposed to four directly acting reference clastogens (mitomycin C, bleomycin, dimethylarsinic acid and potassium chromate) under laboratory conditions. The aim was to examine the inducibility of micronuclei (MN) in haemocytes and gill cells. Positive responses were observed in both tissues for all four substances used under the given test conditions. The mean MN frequencies in treated mussels ranged between 3.2 and 6.9/1000 in haemocytes and between 5.4 and 6.7/1000 in gill cells. The spontaneous MN levels averaged 1.2 and 2.8/1000 in haemocytes and gill cells, respectively. The MN induction capacity of the different chemicals was equivalent in both tissues, except for the treatment with dimethylarsinic acid which generated a significantly higher MN rate in gill cells than in haemocytes. Several characteristics suggest that haemolymph is the more appropriate test tissue for environmental genotoxicity assessment: (1) a shorter preparation time of slides, (2) a more accurate identification of unambiguous MN, (3) a lower baseline MN frequency and a higher induction factor.

An outbreak of amoebic gill disease in ireland

Abstract: Ultrasonography of portosystemic shunts

Environmental transmission of a sulfur-oxidizing bacterial gill endosymbiont in the tropical lucinid bivalve Codakia orbicularis

Abstract: Codakia orbicularis is a large tropical member of the bivalve mollusk family Lucinidae which inhabits shallow-water sea-grass beds (Thalassia testudinum environment) and harbors sulfur-oxidixing endosymbiotic bacteria within bacteriocytes of its gill filaments. When a C. orbicularis-specific 16S rDNA (DNA encoding rRNA) primer is used with a bacterium-specific 16S rDNA reverse primer in amplifications by PCR, the primer set was unsuccessful in amplifying symbiont DNA targets from ovaries, eggs, veligers, and metamorphosed juveniles (600 microns to 1 mm in shell length) cultivated in sterile sand, whereas successful amplifications were obtained from gill tissue of adult specimens and from metamorphosed juveniles (600 microns to 1 mm in shell length) cultivated in unsterilized sea-grass bed sand. To ascertain the presence of the symbiont target in juveniles, restriction fragment length polymorphism analysis, Southern blotting, and transmission electron microscopy were used. Specific hybridizations and observation of endosymbiotic bacteria in the gills of numerous juveniles cultivated in unsterilized sea-grass bed sand showed that the sulfur-oxidizing endosymbionts of C. orbicularis are environmentally transmitted to the new generation after larval metamorphosis.

The respiratory development of Atlantic salmon. I. Morphometry of gills, yolk sac and body surface

Abstract: During development from larva to juvenile in Atlantic salmon, Salmo salar, there is a change in the anatomical potential for gas exchange among gills, body skin and yolk sac as the larvae resorb yolk, grow and develop gills. Newly hatched Atlantic salmon have poorly developed gills but do have a high skin area to mass ratio and a large well-vascularized yolk sac. Cutaneous surfaces accounted for over 95 % of the total area available for respiration in newly hatched Atlantic salmon (body mass 0.032s0.060 g). The branchial contribution to total area increased rapidly, however, so that by the end of yolk absorption (body mass 0.19s0.23 g) it constituted 22 % of the total area and overtook cutaneous surface area between 5 and 6 g wet body mass. Harmonic mean diffusion distance across the skin increased through development from 20 mm at hatch (14 mm across the yolk sac) to 70 mm in an 11 g fish. Diffusion distances across both the filaments and lamellae of the gills decreased through development, from 3.7 to 2.4 mm for lamellae and from 14.5 to 10.8 mm for filaments. The total anatomical diffusion factor (ADF, mass-specific surface area per unit diffusion distance) remained constant over early development and appeared to be higher than in adult fish. The distribution of ADF changed over early development from 50 % yolk sac, 42 % body surface and 8 % branchial in newly hatched fish to 68 % branchial and 32 % cutaneous at the end of yolk resorption. Generally, early post-hatch development of gills, ADF and some cutaneous surfaces showed high mass exponents. After yolk resorption (body mass 0.2 g), however, these coefficients were lower and closer to unity. The change in scaling at the end of yolk resorption in this study may reflect the completion of larva to juvenile metamorphosis in Atlantic salmon. Comparison between our data and values in the literature suggests that the timing of gill development is related more to developmental stage than to body size.

Effects of temperature on morphological landmarks critical to growth and survival in larval Atlantic cod ( Gadus morhua )

Abstract: The morphology and function of structures important to energy acquisition were studied from spawning to the stage of transformation of larva to pelagic juvenile in Atlantic cod, Gadus morhua L., from December 1991 to July 1992. Fertilized eggs produced by adult fish from two genetically discrete populations (Newfoundland and Scotian Shelf) were raised under similar conditions in the laboratory at temperatures of 5 and 10°C. Subsamples of larvae were removed from cultures daily for 10 d, and then less frequently, and fixed for light microscopy and scanning electron microscopy. Nine functional morphological “landmarks” important to feeding, respiration and locomotion were chosen from observation of 280 ind. These landmarks defined 12 major developmental stages, from hatching to the pelagic juvenile stage. One of the feeding landmarks, intestinal stage, varied as a function of age and size and the variance in development was higher at 10°C than at 5°C; Newfoundland larvae developed more complex intestines than did Scotian Shelf larvae. In addition, Newfoundland larvae had significantly higher growth rates than those of Scotian Shelf larvae. Despite the higher growth rates and greater structural complexity of the intestine in Newfoundland larvae, the rate of yolk utilization was not significantly different between Newfoundland and Scotian Shelf larvae. Staging of respiratory landmarks showed that the gill arches were probably used preferentially in feeding while respiration was cutaneous. The gills, operculum and gill rakers developed late in larval life and accompanied the transition from cutaneous to branchial respiration. In the yolk-sac period, development of feeding and respiratory structures may be largely genetically controlled. During exogenous feeding, extrinsic factors also become important, as shown by the size and age-independent variation in intestinal development of larval cod raised at different temperatures.

Interaction of environmental xenobiotics with a multixenobiotic defense mechanism in the bay mussel Mytilus galloprovincialis from the coast of California

Abstract: A multixenobiotic defense mechanism similar to a P-glycoprotein multidrug transporter was characterized in the gills of the mussel Mytilus galloprovincialis from Monterey, California. Using a fluorescent dye assay, we measured multixenobiotic transport activity in individual gill cells and assessed the effects of inhibitors or competitive substrates on activity. Natural products that inhibit the mammalian transporter also affected dye transport in the mussel gill. Four moderately hydrophobic pesticides (dacthal, chlorbenside, sulfallate, and pentachlorophenol) and four highly hydrophobic xenobiotics (p,p′-DDT, p,p′-DDD, p,p′-DDE, and Aroclor 1254) all inhibited the efflux of dye from the gills, indicating their interaction with a multixenobiotic transport mechanism in this organism. The reactivity with these highly hydrophobic compounds seen in M. galloprovincialis differs from related transporters found in other organisms. A protein in the gill cross-reacts with antibodies directed against the mammalian multidrug transport protein. The level of protein can be assessed easily by dot blot procedures and may facilitate quantitation of protein levels in field situations.

Response of cell volume in Mytilus gill to acute salinity change.

Abstract: The response of gill cell volume in Mytilus californianus and Mytilus trossolus (=edulis) to acute changes in salinity was assessed using three independent indicators: optical measurement of lateral cell height, measurement of intracellular water content using radiolabeled tracers and measurement of the contents of the major osmolytes of the gills. Optical measurements indicated significant variation in the response of individual lateral cells of M. californianus to acute low-salinity shock. Lateral cell height increased by approximately 20% shortly after abrupt exposure to 60% artificial sea water (ASW). Following this initial swelling, we estimate that a substantial regulatory volume decrease (RVD) was present in 25% of the trials. More commonly, however, an RVD was either absent or minimal: cell height remained elevated for at least 1 h, then returned to the control height when gills were re-exposed to 100% ASW. Changes in the combined water space of all cells in the gill, measured as the difference between total water space and extracellular space ([14C]polyethylene glycol space), indicated that cell volume regulation in the gill as an organ was also absent or minimal. Cell water space was 2.16 ml g-1 dry mass in isolated gills of M. californianus acclimated to 100% sea water in the laboratory and increased to 2.83 ml g-1 dry mass after a 6 min exposure to 60% ASW. Cell water space was still 2.81 ml g-1 dry mass after 1 h in 60% ASW and returned to 2.06 ml g-1 dry mass upon re-exposure to 100% ASW. Consistent with these observations, the gill contents of the principal cytoplasmic osmolytes (taurine, betaine and K+) were unchanged (approximately 450, 250 and 230 mu mol g-1 dry mass, respectively) following exposure of gills from 100% ASW-acclimated mussels to 60% ASW. A decrease in cell water space to 2.66 ml g-1 dry mass after 4 weeks of acclimation to 60% ASW corresponded with a 37% decrease in betaine content; taurine and K+ contents were unchanged. The changes in water space and solute content of gills from freshly collected M. californianus and M. trossolus were also consistent with the absence of volume regulation; cell water space remained elevated for at least 1 h after low-salinity exposure, and solute contents were unchanged after this period. We calculated the potential energetic cost of cell volume regulation for mussels exposed to 12 h of sinusoidal fluctuations between 100% and 50% sea water; solute uptake for full volume regulation in all tissues would cost a minimum of approximately 30% of the standard metabolic rate during the period of salinity increase. The routine absence of substantial cell volume regulation in Mytilus gill may reflect the potentially high energetic cost of volume regulation in the face of the large and frequent salinity fluctuations that are regularly encountered by estuarine bivalves.

Multipurpose Gills: Effect of Larval Brooding on the Feeding Physiology of Freshwater Unionid Mussels

Abstract: During reproduction, the lateral (outer) demibranchs of the unionid mussel Pyganodon cataracta function in brooding females as marsupia in addition to serving in gas exchange, feeding, and ion transport. Recent studies indicate that glochidial brooding reduces clearance rates and particle retention efficiencies, but the opaque shell prevents direct observations of suspension feeding structures and makes it difficult to identify the underlying causes of the changes in feeding dynamics. In this study, video endoscopic techniques were used to describe and compare, in vivo, the feeding structures and dynamics of brooding and non-brooding females. Although circulation within the mantle cavity was slightly altered by the enlarged lateral (gravid) gills of brooding females, both medial and lateral gills continued to retain and process particles. During brooding, circulation through medial gills was maintained by the construction of secondary water tubes near the medial and lateral ends of the brood chambers. In vivo monitoring of particles retained by the frontal surface of the gill indicated that transport rates for particles processed by gravid gills of brooders were significantly slower than on lateral gills of non-brooders or on medial gills. Similarly, gravid gills were less efficient at retaining small particles (<6 ptm) than medial or non-gravid lateral gills. These findings are consistent with the hypothesis that observed reductions in particle clearance rates and retention efficiencies in brooding female mussels are the result of functional changes in the ciliature and flow dynamics of the marsupial gills. Moreover, similar mechanisms mediating particle capture and processing on medial demibranchs appear to be unaffected by the presence of developing glochidia in the water tubes of the lateral gills. Additional key words: glochidia, endoscopy, suspension feeding, filtration Though the gills of suspension feeding bivalves are typically identified as structures for feeding, gas exchange, and ion transport, the ctenidia of many marine and freshwater species also incubate larvae during reproductive periods. Brooding mechanisms vary considerably among species. Most freshwater bivalves, including members of the Corbiculidae and Unionidae, lack planktonic larval stages and incubate developing embryos within internal spaces between gill lamellae (Ortmann 1911; Britton & Morton 1982; Kat 1984; Mackie 1984). In other freshwater and marine bivalve molluscs, developing young are attached to pallial structures or restricted to specialized brood masses, papillae, or sacs (Heard 1977; Bartlett 1979; Richardson 1979; Mackie 1984; Kabat 1985). Conversely, some species, including oysters of the genus Ostrea, brood within the infrabranchial cavity but the young are not confined or physically attached to the mother and move about freely in the inter-demibranchial spaces (Chaparro et al. 1993). Although numerous studies have examined the mechanics of the bivalve pump and filter (for review see J0rgensen 1990), the effect of larval incubation on the gills' customary roles as feeding and respiratory structures has been ignored, except for the observation of Walne (1972) that clearance rates of the oyster Ostrea edulis are lower during brooding periods. In the Unionidae, modifications of ctenidia for brooding, including the location and arrangement of larvae (glochidia) within brood chambers, the degree of swelling of the lamellae, and the duration of larval incubation, vary among species and often serve as important taxonomic characters (Ortmann 1911; Heard & Guckert 1971). In most species, the water tubes of either the lateral (outer) demibranchs or all four demibranchs serve as ovisacs. In others, the marsupium is restricted to a portion of the lateral gills, often forming bulges or sulci along the ventral aspect of the demiThis content downloaded from 207.46.13.21 on Tue, 27 Sep 2016 04:23:58 UTC All use subject to http://about.jstor.org/terms

Experimental study on the influence of paper and pulp mill effluent on the gill parasite communities of roach (Rutilus rutilus)

Abstract: Roach (n = 81) caught on 23 May, 1992 from oligotrophic, unpolluted Lake Peurunka were kept in cages over a 2-week period before moving half of the fish to nearby Lake Vatia, which is influenced by pulp mill effluents. Before moving the fish gill parasites were examined from 9 fish; 5 Dactylogyrus species, Gyrodactylus sp. and Paradiplozoon homoion were found, the main components of the infracommunities being dactylogyrids. Afterwards, 5 fish from each lake were studied weekly between 1 July and 17 August. Metazoan parasites were recorded from gill arches divided into 4 sections along the dorso-ventral axis. D. crucifer, D. nanus, D. micracanthus and D. suecicus occurred in both lakes throughout the study. Gyrodactylus sp., Ergasilus briani and P. homoion occurred in low numbers in both lakes. Differences between the lakes were seen in the prevalence of D. micracanthus which was higher in Lake Vatia and significantly increased abundances of D. crucifer, D. nanus and D. micracanthus in Lake Vatia. Abundances of other Dactylogyrus species remained, on average, at the same level in both lakes. No change during the experiment was recorded in the location of the two most common species, D. crucifer and D. nanus, on the host gills in either of the lakes, both species favouring the 2nd and 3rd gill arches and especially the inner parts of the gills. The apparent lack of competition between the 2 most common Dactylogyrus species indicates that no limitation of resources on roach gills occurred. This was also confirmed by the increased overlapping indices with increasing abundances between the two most common species in Lake Vatia.

Differences in protein patterns of gill epithelial cells of the fish Gillichthys mirabilis after osmotic and thermal acclimation

Abstract: Different protein patterns in gill epithelium of a euryhaline and eurythermal teleost fish (Gillichthys mirabilis, Family Gobiidae) in response to long-term (2 months) osmotic and thermal acclimation were found for the first time. Gill epithelial cells were isolated to remove extracellular proteins and quantify specialized cell types. Chloride cells were identified on the basis of size (>10 μm) and bright appearance after [2-(p-dimethylaminostyryl)-1-methyl-pyridinium-iodine] staining. Small mitochondria-rich cells were 85% of cells). Thus, they represented the major protein source in gill epithelium. Differences in protein patterns were detectable using two-dimensional but not one-dimensional electrophoresis. Of 602 proteins identified by charge and molecular weight properties, only two were induced by high temperature (25°C) and three in response to cold acclimation (10°C). Nine proteins were induced in diluted seawater-acclimated fish, whereas no seawater-induced proteins were found. We hypothesize that proteins induced under dilute seawater conditions are important for the function of pavement cells in gills of hyper-osmoregulating G. mirabilis.

Communications: Entry of 35S-Labeled Edwardsiella ictaluri into Channel Catfish

Abstract: Channel catfish Ictalurus punctatus fingerlings were bathed for 1 h in water containing 5.6 × 106 Edwardsiella ictaluri/mL labeled with [35S]methionine. Eight organs or tissues were collected from fish at varied intervals from 2 to 72 h after exposure; tissues were digested and radioactive disintegrations were measured in a liquid scintillation counter. A parallel study was conducted by using heat-killed E. ictaluri from the same radiolabeled culture, Bacteria rapidly became associated with the gills (2 h) and persisted in or on the gill and liver (2–72 h). Fewer bacteria were detected in the trunk kidney, gut, and brain, Heat-killed radiolabeled bacteria could not be detected in the fish, Our results suggest that E. ictaluri accumulates on and enters through the gill and that the gill should be considered as a route of entry. The absence of detectable heat-killed bacteria indicates a need to reexamine strategies for fish vaccination with killed bacterins.

Early gill development in the rainbow trout, Oncorhynchus mykiss.

Abstract: The morphology of the gills of rainbow trout (Oncorhynchus mykiss) embryos was studied by light and electron microscopy at four different developmental stages. Embryos were examined during gill arch formation (stages 22-24, Vernier, '69), development of the gill filaments (hatching stage), and formation of gill lamellae (stage 36). Our observations showed that the gill arches are covered by endoderm of the pharyngeal pouches and ectoderm of the gill furrows, which meet to form a closing plate. Ultrastructural evidence indicates that secretion of mature hatching gland cells around the closing plates is the mechanism responsible for their perforation and is consistent with the hypothesis of Miller et al. ('93) that cellular reorganization is a major mechanism of initial perforation of closing plates. Epithelia of the gill filaments and gill lamellae are composed of undifferentiated basal epithelial cells, outer pavement cells, and specialized chloride cells and goblet cells. The appearance of these cells and their ultrastructural features during embryonic development are correlated with gill function. It is not until stage 36 that gill epithelia exhibit adultlike ultrastructural features. © 1996 Wiley-Liss, Inc.

Cadmium influx across isolated Carcinus gill epithelium interaction of lanthanum and calcium with cadmium influxes

Abstract: The effects of Ca and La on Cd transport across apical and basolateral gill surfaces were examined in isolated perfused Carcinus gills. In the gills exposed to diluted sea water enriched with calcium by addition of CaCl2 to 11.9 and 15.9 mmol·l-1 the Cd influxes decreased by 55% and 85%, respectively, compared to those observed in diluted sea water (6.9 mmol Ca·l-1). When Ca was added to the perfusate to increase its concentration at the basolaterally oriented gill surfaces, Cd influx inhibition was less pronounced than when Ca was added apically. The effect of Ca on 109Cd influxes appears, therefore, to be exerted at the apical gill surface. Additionally, the effects of various concentrations of the non-specific Ca channel blocker La (added to diluted sea water) on 109Cd influxes in isolated perfused Carcinus gills were studied. 109Cd influxes are shown to be lanthanum concentration dependent. The half-maximum inhibition of cadmium influxes by La occurred at 1.4·10-6 mol·l-1. Cadmium transport is discussed in terms of non-specific influx utilizing Ca channels.

Hemorrhagic Anemia of Carp Associated with Spore Discharge of Myxobolus artus (Myxozoa : Myxosporea)

Abstract: Seasonal occurrence of Myxobolus artus infection in common carp Cyprinus carpio was monitored in a fry pond (Tokyo Metropolis) for one and a half year. Formation of pseudocysts in the skeletal muscle was detected from August, and the prevalence of infection reached a maximum of 10% in September. After maturation of pseudocysts, diseased fish released spores into the water at a maximum level of about 3t106 spores/ day/fish in October. Spore release decreased in late autumn and winter, increased in spring and exhausted in the following summer in 1-year old recovered fish. Mortality of diseased fish was negligible in September. However, chronic mortality with a typical sign of anemic gills was found during the spore releasing period. During a high level period of spore discharge, hematological indices (Ht, Hb, and RBC) in diseased fish significantly decreased, and the percentage of immature erythrocytes increased. Histopathological examination showed that numerous phagocytosed spores caused local occlusion and destruction of gill capillaries and exfoliation of gill epithelium, suggesting blood loss from the damaged gills. It was suggested that chronic hemorrhagic anemia was associated with spore discharge from carp heavily infected with M. artus.

Toxicology of Aquatic Pollution: Water chemistry at the gill surfaces of fish and the uptake of xenobiotics

Abstract: Introduction There is a massive production of chemicals synthesized to meet the demands of industry. Most of these chemicals are foreign to the body (xenobiotics). They enter the environment where they are available for uptake by organisms. Most animals possess enzymes (multi-function oxidases) which reduce the toxicity of the xenobiotics and facilitate their excretion. Many xenobiotics, however, are resistant to metabolic degradation, are accumulated in the body and can be extremely toxic. Most organic chemicals must enter the body before they can exert their toxic effect(s). Uptake can occur through the food chain or by direct uptake from the environment across the respiratory surface and skin. The uptake of xenobiotics from water by fish is determined by numerous factors, the most important of which are the transfer capacity of the gills and the physio-chemical properties of the compound. Exchange at the gills In adult fish, the gills comprise the major surface area of the body, and constitute a thin but continuous barrier between the environment and the blood. Water flows over the gills counter to blood flow ensuring a constant partial pressure gradient of O 2 and CO 2 over the duration of blood transit through the gills. Conditions for diffusion of O 2 are further maximized by the presence of haemoglobin which binds molecular oxygen keeping the PO 2 in the blood low. The gills in fish are hyperventilated with water relative to blood to ensure adequate rates of oxygen uptake from the environment.

Morphological Studies of Gill and Mitochondria-rich Cells in the Stenohaline Cyprinid Teleosts, Cyprinus carpio and Carassius auratus, Adapted to Various Hypotonic Environments

Abstract: The structure of the gills and the epithelial mitochondria-rich (MR) cells of the carp, Cyprinus carpio, and goldfish, Carassius auratus, adapted to various hypotonic media was studied by scanning electron microscopy. The gills consist of arches, rakers, filaments, lamellae, and the septum. The epithelium of the filament could be identified as having an afferent region, interlamellar region, and efferent region. According to the morphology of the apical surfaces, branchial MR cells which are responsible for ionoregulation were found to exhibit different types. With apical membranes larger than 2 μm in maximum dimensions, type A MR cells displayed broad and shallow apical surfaces. Type B MR cells measuring 1 to 2 μm were small and had deep openings. Distribution and densities of MR cells differed in the cyprinid teleosts acclimated to various hypotonic media. In 5 per mille salt water, type A MR cells were found to decrease significantly in size and number. In deionized water, proliferation of MR cells was found in lamellae. The results revealed different morphologies of MR cells in stenohaline freshwater teleosts which suggests a possible correlation between morphology and function of MR cells.

A comparative allometric study of the morphometry of the gills of an alkalinity adapted cichlid fish,Oreochromis alcalicus grahami, of Lake Magadi, Kenya

Abstract: A morphometric analysis of the gills ofOreochromis alcalicus grahami has been carried out on specimens from ecologically distinct lagoons and a water-holding tank of Lake Magadi, a highly alkaline salt lake situated in a volcanically active region of the southern part of the Great Rift Valley in Kenya. The data were compared with those fromOreochromis niloticus, a close relative that lives in fresh water and with data from other fresh water and marine fish. Our primary goal was to identify the possible adaptive features which enable the fish to survive in an environment characterized by severely fluctuating levels of oxygen, a condition exacerbated by factors such as high temperature, alkalinity and osmolarity. The specimens ofO. a. grahami from the south-western lagoons of the lake had gills better adapted for gas exchange with a body mass specific diffusing capacity for oxygen which was about 2 times greater than that of the gills of the specimens from the fish spring lagoons and 2.5 times that of those from the water-holding tanks. Some parameters of the gills ofO. a. grahami, e.g. the gill filament length and number of gill filaments are significantly greater than those ofO. niloticus but the number of secondary lamellae, area of secondary lamellae and the diffusing capacity of the gills are similar in the two species. Compared with most other fish, the gills ofO. a. grahami appear to be particularly well adapted for gas exchange especially by having a thin water-blood barrier. Perhaps in no other extant fish have the gills had to be so exquisitely designed to meet environmental extremes and regulate complex and at times conflicting functions such as gas exchange, iono-regulation, acid-base balance and nitrogenous waste excretion as inO. a. grahami

Eosinophilic granulocytes in the epidermis of Oreochromis mossambicus gill filaments studied in situ

Abstract: Granular cells were observed in the epidermis of isolated gill filaments using Normaski microscopy at×400 magnification. Granulocytes were motile and chemotactic to histamine (introduced via a micropipette into the filament) and to the products of degranulation of neighbouring granulocytes within the epidermis. The abundance of visible granulocytes within the epidermis of gill filaments was increased in the period following net capture, confirming their migratory ability. Cells isolated from gill tissue are poorly glass adherent. They are also eosinophilic and more dense than macrophages and lymphocytes on a discontinuous percoll gradient. They are identified as eosinophils on the basis of these characteristics.

Sphingomyelin metabolism is linked to salt transport in the gills of euryhaline fish.

Abstract: By in vivo and in vitro studies of L-(3-3H)serine and [9,10(n)-3H]palmitic acid incorporation into phospholipids, we show a change in the renewal of the ceramide moiety of sphingomyelin in the gills of euryhaline fish (sea bass and eels) when the animals were subjected to abrupt alterations in environmental salinity. In vivo, decrease of the salinity from sea water (salinity 3.7%) to diluted sea water (salinity 1%) induced an increase of label incorporation into gill sphingomyelin. The same was true when gills from sea water-adapted sea bass or sea water-adapted eels were incubated in diluted sea water. A decrease in free ceramides synthesis was also observed in the gills of sea water-adapted sea bass when the salinity of the incubation medium was reduced. Direct inhibition of Na+/K(+)-ATPase activity with ouabain decreased the sphingomyelin synthesis in the gills of sea bass during in vitro incubation in diluted sea water, whereas treatment with furosemide stimulated sphingomyelin synthesis in the same gills incubated in sea water. These findings indicate that changes in Na+ fluxes modify the sphingomyelin turnover and control the production of free ceramides and sphingosine in gill cells of euryhaline fish. In view of the well-known effects of these sphingomyelin degradation products on isolated tumor cell differentiation, we suggest that they play a very important role in modulating chloride cell distribution and metabolism of fish gills during abrupt changes in environmental salinity.

Co-occurrence and microhabitat of Ancyrocephalus mogurndae (Monogenea) and Henneguya weishanensis (Myxosporea) on gills of the mandarin fish, Siniperca chuatsi

Abstract: Seasonal variations in a population of the monogenean Ancyrocephalus mogurndae Gussev, 1955 were investigated on gills of cage-cultured mandarin fish, Siniperca chuatsi (Basilewsky), during the period from April 1994 to April 1995. The abundance of A. mogurndae peaked in late spring and summer. Prevalence was high (75-100 %) throughout the study period, and did not vary significantly between months. More than 50 % of all monogeneans were found on the first and second gill arches, except one occasion when the fourth gill arch had the majority in April 1995. The niche breadths were significantly correlated with the population abundance. A coexistent parasitic myxosporean, Henneguya weishanensis Hu, 1965, on the gills of the fish was found to have little influence on the gill-arch preference of the monogenean, although the monogenean abundance was higher in those fish infected with the myxosporean.

Gill filaments of Liza ramada, a biotope for ectoparasites : surface area acquisition using image analysis and growth models

Abstract: Ecology of plant or animal communities requires knowledge of the biotope structure of these organisms. In the case of parasitic communities, the organs of a host constitute heterogeneous biotopes. Fish gills are an example of this, but their heterogeneity is not often considered. The gills of the mullet Liza ramada are such a biotope for several ectoparasites. Parasite density is an important factor in the study of fish-parasite interactions, but cannot be determined if the colonized surface area of the gills is not known. The number of primary filaments, and therefore the surface area potentially colonized, is subject to variation with age. Assessment of the colonizable area raises specific problems of estimation. A new method taking into account surface areas of primary filaments and using image-processing techniques is proposed. Models related to the increase of filament number and colonizable gill area as functions of the fish fork length are proposed. The increase of primary lamellae number with fish length can be fitted by an exponential-type model and the accompanying increase in size of the colonizable gill area by a polynomial-type model.

Comparative study on gill morphology of gastropods from Moreton Bay, Queensland

Abstract: This paper reports the gill morphology of seven common gastropods from Moreton Bay, southeastern Queensland, to test the level of difference in gill structure between major taxa. The investigated species include representatives of the clades Patellogastropoda, Neritimorpha and Vetigastropda as well as representatives of the more ‘advanced’ Caenogastropoda. Examination by SEM and LM revealed that the external gill structure of the investigated caenogastropods (including Planaxis sulcatus, Littoraria articulata, Bembicium auratum and Morula marginalba) shows basic uniformity. The gill filaments are composed of a clearly defined ridge and an extended sheet of non-ciliated cells. The gill filaments of these species differ in the shape of the filaments (corrugated, triangular or rounded) and the presence of secretory cells. The gills of the limpet Patelloida mimula and neritid Nerita chameleon, representatives of the clades Patellogastropoda and Neritimorpha respectively, are both triangularly shaped, but differ by the presence of paddle shaped cilia in the former species and secretory cells in the latter. The gill morphology of the vetigastropod trochid Austrocochlea constricta, characterized by blade shaped filaments covered with nodules and a striped pattern of ciliated cells, showed the least similarities with the other investigated species.

Importance of a Siderophore in the Pathogenesis and Virulence of Photobacterium Damsela Subsp. Piscicida in Hybrid Striped Bass (Morone Saxatili X Morone Chrysops).

Abstract: Photobacterium damsela subsp. piscicida, formerly Pasteurella piscicida, is an important new pathogen of hybrid striped bass cultured in brackish water on Louisiana mariculture farms. Louisiana isolates compared with strains of P. damsela subsp. piscicida from Greece, Japan, Israel and Chesapeake Bay, USA and were found to be identical in biochemical phenotype and enzymic activity. Small plasmids of 8 and 5 kb were unique to Louisiana strains. Sequential daily bacteriology and histopathology on hybrid striped bass experimentally infected by immersion revealed that following high doses (13,000 CFU/ml) the gills and spleen are colonized first as early as 24 hours PI, followed by the blood at 48 hours and the liver at 72 hours. Bacteria reached levels as high as 5.7 X 109 CFU/gram in the spleen and 8.6 X 10® in the blood of moribund fish. The spleen contained a significantly higher number of cells than any other organ at all sampling time periods. Histological examination of the gills using semithin sections showed high numbers of bacteria invading and colonizing the the gill lamellae at 24 hours PI. Death of the fish appeared to result from respiratory failure due to necrosis of the gill lamellae and blockage of blood flow to the gills by masses of bacteria in the capillaries.