bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning cytophotometry of carp, Cyprinm carpio L., erythrocyte populations: the influence of short‐term hypoxic environment and the recovery period following severe bleeding
Authors: Schindler J. F. , de Vries U.
Published: January 2006

Scanning stage absorbance cytophotometry was used to examine haemoglobin contents in individual cells or carp erythrocyte populations. Changes in frequency distributional profiles in response to respiratory stress caused experimentally by hypoxia and/or bleeding were studied at intervals.

Histograms were drawn of haemoglobin contents of individual red blood cells in populations obtained from the same carp on four consecutive days after the fish was temporarily exposed to hypoxic environment. The modes and means of the haemoglobin values increased during the 3 days following to the stimulus, whereas a decline was measured on the 4th day. Erythrocyte counts showed the total number of red blood cells to be approximately constant during the period of investigation. On the basis of these findings, it is concluded that the mature, nucleated red blood cells of carp are capable of resuming haemoglobin synthesis after stimuli such as reducing ambient oxygen concentration.

Frequency distributional profiles covering a period of 4 weeks following severe loss of blood showed that it took 10–12 days after bleeding until masses of immature erythrocytes appeared in the peripheral blood and that there were then two distinct populations of red blood cells. In the course of about 2 weeks the precursor cells developed into mature erythrocytes.
An electron microscopic examination of the gastrointestinal epithelium in Dover sole, Solea solea (L.)
Authors: Macdonald N. L.
Published: January 2006

The gastrointestinal tracts of adult and juvenile Dover sole, Solea solea (L.), were examined using scanning (SEM) and transmission electron microscopy (TEM). SEM showed little differentiation of the internal morphology of the gastrointestinal tract in adult fish, with longitudinally arranged mucosal folds present in all gut regions. Mucosal folds had a similar arrangement to that in the goldfish. Goblet cells were identified in the mucosal epithelium in all regions of the gut while microscopic ducts/pores of possible pancreatic origin were observed in the foregut region. SEM of juvenile gut samples showed a similar arrangement of longitudinal mucosal folds to that found in the adult fish. There was no visible evidence of goblet cells or secretory ducts/pores in any region of the juvenile gastrointestinal tract.

In TEM it was observed that apical microvilli were a feature of epithelial cells from all regions of the gastrointestinal tract in adult and juvenile Dover sole. Cells from the distal regions of the adult and juvenile gut showed invaginations and vacuolation of the apical cytoplasm. A high degree of vacuolation in cells from the juvenile hindgut‐rectum indicated the possible occurrence of intracellular digestion of absorbed nutrients in this gut region.
A histophysiological study of muscle differentiation and growth in the common carp, Cyprinus carpio Var. communis
Authors: Talesara C. L. , Urfi A. J.
Published: January 2006

From an histochemical and biochemical study on the fibre differentiation and muscle growth in common carp, Cyprinus carpio Var. communis, growth and development processes have been characterized on the basis of differences in fibre size, fibre number, lipid content, succinic dehydrogenase (SDH) and myofibrillar adenosine triphosphatase (m‐ATPase). A very early differentiation and zonal segregation of principal fibre types (red and white) and subsequent increase in muscle by their hypertrophy and hyperplasia was observed. These changes become pronounced after yolk sac absorption. The special character of the red muscle, as it develops from a superficial monolayered lateral sheet to a compact multicellular cone, was also investigated.
Experimental evidence for juvenile Chinook salmon, Oncorhynchus tschawytscha Walbaum, orientation at night and in sunlight after a 7° change in latitude
Authors: Taylor P. B.
Published: January 2006

A group of eighteen young chinook salmon, Oncorhynchus tschawytscha Walbaum, trained to orientate in the direction 270°, showed a unimodal orientation of 264° and a mean bimodal axis of orientation of 258°/078° (magnetic) within confidence limits of 218°←→285°: 038°←→105° when tested under controlled conditions in Auckland. Two years later 12 of these fish were transferred to a new test arena in Christchurch, south (7° latitude) of the original location, for individual re‐testing at night in a light‐proof room and also in sunlight; in the absence of ‘local’ Auckland cues/clues. These fish had been kept in artificial light but six fish were exposed to sunlight in Auckland 2 weeks before moving to Christchurch.

At night each fish showed consistent non‐random orientation and nine out of 10 fish showed a mean bimodal orientation that fell within the confidence limit established in Auckland; the mean of means axis of orientation for 10 fish was 270°/090°. In sunlight each individual fish showed a consistent, non‐random mean bimodal orientation that fell outside the confidence limits established in Auckland and, at night, in Christchurch. The mean of means axis of orientation was 001°/181° (magnetic); the map direction from Christchurch to Auckland is 15°. The principal findings in this study were:

(a) ‘Local’ Auckland cues were not essential for location of the learnt direction. (b) A non‐visual ‘universal’ cue was used as a reference for location of direction at night. (c) Daylight orientation was influenced by anisotropic radiance, even though the sun image was obscured by the test arena cover. (d) The concentration of data at midday and sunset in artificial light and perhaps at midnight, may indicate the presence of a non‐visual zeitgeber. (e) A correlation between time and direction, in light and in darkness, which by implication involves a co‐ordination process. (f) The fish under test apparently imprinted on some aspect of the sun (in Auckland) within a 2‐day period at the age of 2 years. (g) Displacement, by 7° in latitude, may have been detected by both visual and non‐visual means.

It is proposed that directional information from the geomagnetic field and the anisotropic radiance of sunlight provides a complementary cross reference which would be sufficient for positional orientation, in relation to some fixed landmark, within coastal waters; but would not suffice for spatial orientation in mid‐ocean.
Metabolic adjustments of an air‐breathing teleost, Channa maculata, to acute and prolonged exposure to hypoxic water
Authors: Yu K. L. , Woo N. Y. S.
Published: January 2006

Plasma and tissue metabolite levels were measured in the air‐breathing Channa maculata during acute and prolonged exposure to normoxic and hypoxic water. Exposure of the fish to hypoxic water (water oxygen partial pressure, PwO2= 50 mmHg) for 1 h caused increases in plasma glucose and lactate, liver and brain lactate, liver a‐amino acid, heart and brain alanine and brain succinate levels. The metabolic changes in heart, brain and muscle could only be detected when PwO2 was 30 or 10 mmHg. Heart glycogen and liver lipid decreased during acute exposure. Prolonged exposure to hypoxic water (PwO2= 30 mmHg) for 3 days caused an increase in plasma glycerol and liver lactate dehydrogenase activity, and a depletion of glycogen store in all tissues investigated. However, metabolite levels which had been elevated during acute hypoxic exposure were observed to return to their normoxic values after prolonged exposure. It was concluded that anaerobic metabolism was triggered by acute exposure to hypoxic water. Prolonged exposure to hypoxic water induced a metabolic readjustment involving mobilisation of lipid and glycogen stores, which is probably a reflection of the high metabolic load of aerial respiration imposed on the fish during exposure to hypoxic water.
Utilization of algal cell fractions by the marine herbivore the luderick, Girella tricuspidata (Quoy and Gaimard)
Authors: Anderson T. A.
Published: January 2006

Absorption of 14C from the marine alga Enteromorpha by an herbivorous marine fish, the luderick, Girella tricuspidata, was used to demonstrate the capability of this species to utilize an herbivorous diet. Absorption of 14C from protoplasts and cell walls clearly demonstrated a capability of the luderick to utilize cell walls. Two patterns of absorption of algal fractions were seen, but in all cases isotope absorption by the fish was highest from protoplasts over a 16‐h digestion period. The first pattern, demonstrated by the absorptive tissues of the gut, showed greater absorption of the radioactive label from cell walls over 5 days than over 16 h. The second, occurring in the anterior regions of the gut and in the liver and spleen, showed greater absorption of 14C from cell walls over 16 h than over 5 days. It is suggested that the marker found in this second group of tissues derives from absorption in the pyloric caeca, the only absorptive region showing significant absorption of carbon label from cell walls over 16 h. Absorption of 14C from cell walls is greater over 5 days than over 16 h.
Characteristics of the spawning migrations of brown trout, Salmo trutta L., and rainbow trout, S. gairdneri Richardson, in Great Lake, Tasmania
Authors: Davies P. E. , Sloane R. D.
Published: January 2006

Upstream spawning migrations of mature brown trout, S. trutta, and rainbow trout, S. gairdneri, were studied in Liawenee Canal, Great Lake from 1949 to 1985. Brown trout migrations normally occurred from early April to mid‐May and rainbow trout from late August to early November. In 1983, 16 425 brown trout and 1338 rainbow trout passed through a fixed upstream diversion trap. Brown trout spawning migrations occurred predominantly over the temperature range 6–10° C, while rainbow trout migrated predominantly over the range 5–11° C. Migrations peaked at water temperatures of 7.6°C (males) and 7.8°C (females) for brown trout, and 8.3°C (males) and 9.6°C (females) for rainbow trout. Rainbow trout migrations occurred at high flow conditions and were positively correlated with canal flow increases, while brown trout migrated under low canal flow. Mean length, weight and condition of rainbow trout of both sexes decreased significantly during migrations. Female brown trout decreased in weight and condition but not in length; male brown trout did not change in condition despite decreases in both length and weight during migrations. Overall sex ratio was 2:1 (female:male) for both species, with the relative proportion of male fish decreasing as migrations progressed. Age composition changed during migrations; dominant age classes were 3 < 4 < 5 + years for both species. Comparison of length, weight, condition and age revealed minor changes during the 37‐year period 1949–1985.
Epizootic characteristics of hepatic and renal lesions in English sole, Parophrys vetulus, from Puget Sound
Authors: Rhodes L. D. , Myers M. S. , Gronlund W. D. , Mccain B. B.
Published: January 2006

English sole, Parophrys vetulus, from eight locations within Puget Sound, U.S.A. were examined for histological abnormalities of the liver and kidney. A total of 1083 fish were collected between February 1979 and June 1984 in nine separate sampling periods. Idiopathic lesions, i.e. lesions of unknown cause, were classified into eight hepatic and four renal lesion categories. The significance of certain potential risk factors associated with lesion prevalences, including age, gender, site of capture, season of capture and year of capture, were assessed by logistic regression. The odds ratios for the significant risk factors were also calculated. Site of capture and age of the examined fish were found to be the most important factors for most of the observed lesion types, e.g., hepatic neoplasms and foci of cellular alteration, whereas year and season of capture were significant influences for only a few lesion types, e.g., specific and nonspecific degenerative/necrotic lesions of the liver. Gender of examined fish was not found to be a significant factor for any of the lesion types. These results emphasize the importance of including certain potential influences, such as age and season of capture, in the analysis of field‐collected organ pathology data.
A new genus and species of the family Ipnopidae (Pisces, Teleostei) from the eastern North Atlantic, with notes on its ecology
Authors: Merrett N. R. , Nielsen J. G.
Published: January 2006

An additional and hitherto undescribed ipnopid genus and species, Discoverichthys praecox Merrett and Nielsen, is reported and described, and its relationships with the family and aspects of its biology are discussed.
A trap for catching adult lampreys (Petromyzonidae) in running water
Authors: Morris K. H. , Maitland P. S.
Published: January 2006

A trap for catching migrating lampreys in running water is described. It is based on a double‐funnel system and uses standard, readily available, plastic and brass materials. The trap is inexpensive, portable and easy to install and hide, even in shallow, fast‐flowing water. It has been found to be more successful than the other traps with which it was compared in field trials and is highly selective for lampreys.
.Chromosome sex determination and Y‐autosome fusion in Blennius tentacularis Brunnich, 1765 (Pisces, Blennidae)
Authors: Carbone P. , Vitturi R , Catalano E. , Macaluso M.
Published: January 2006

Diploid modal numbers of 2n=48 for females, and 2n=48 and 2n=47 for males of Blennius tentacularis caught in the Gulf of Palermo (Sicily) are established. Chromosome sex‐determination is proposed for this species in which a Y‐autosome fusion has been found.
Growth and mortality of the introduced Lake Tanganyika clupeid, Limnothrissa miodon, in Lake Kariba
Authors: Marshall B. E.
Published: January 2006

The growth and mortality of the small clupeid fish Limnothrissa miodon were studied in Lake Kariba, a large, man‐made lake in central Africa. Growth could be described by the von Bertalanffy equation lt= 74.2 (1—e−0.254(t+0.07)) where length (l) is expressed in millimetres and time (t) in months. The monthly rates of mortality were high and increasing under intensive fishing; in 1983 the total mortality rate Z=1.15 and natural mortality M=0.7. Limnothrissa appears to be stunted in the man‐made lakes where it occurs (Kariba and Cahora Bassa) where it grows at a faster rate but to a smaller size than it does in natural lakes (Kivu and Tanganyika). Various hypotheses to account for this are discussed and it was concluded that this is an adaptation to the relatively unstable conditions found in the man‐made lakes.
Cardio‐respiratory morphometrics of spangled perch, Leiopotherapon unicolor (Günther, 1859), (Percoidei, Teraponidae)
Authors: Gehrke P. C.
Published: January 2006

The heart of Leiopotherapon unicolor comprises 0.135±0.005% of total body weight compared to the average teleost heart size of 0.081±0.002% body weight. The respiratory surface area of 569 mm2 g−1 is also much larger than that found in most freshwater fish. The exponent b in the equation Gill Area =a. body wtb was evaluated at 1.04, whereas the theoretical value for b is only 0.75. It is therefore evident that L. unicolor has an excessively large gill area and a large heart, which facilitate oxygen uptake in hypoxic environments.
Relationships between maternal size, egg diameter, time of spawning season, temperature, and length at hatch of Atlantic silverside, Menidia menidia
Authors: Bengtson D. A. , Barkman R. C. , Berry W. J.
Published: January 2006

Eggs were stripped from gravid Atlantic silversides collected on two occasions, once during the early part and once during the late part of the natural spawning season. Unfertilized egg diameter was not correlated with length of the female, nor was it significantly larger during the early part of the season. Eggs were fertilized and incubated in the laboratory. Larval length at hatch was measured every 24 h during the hatching period after embryos were incubated at 18 or 25° C. Lower incubation temperature caused a significantly greater length at hatch for the offspring of each of the 20 females studies. In most cases (17 out of 20 at 25° C, 10 out of 20 at 18° C), there was a significant decrease in length at hatch during the hatching period for a given female's eggs incubated at a given temperature. In the natural environment, larvae hatched early in the season under cooler temperatures could average 12% longer than those hatched later under warmer temperatures, and therefore may have a greater chance of survival. The results help to explain the observation that field‐caught M. menidia that hatched early in the season are larger at any given age than those that hatched late in the season.
Microvascular organization of the pseudobranch and carotid labyrinth of two species of air‐breathing teleostean fishes
Authors: Munshi J. S. D. , Hughes G. M.
Published: January 2006

The microvasculature of the pseudobranch in Anabas testudineus and the carotid labyrinth of Heteropneustes fossilis have been studied using scanning electronmicroscopy of Mercox‐injected casts. Results confirm differences in origin and basic capillary structure. It is concluded that the pseudobranch is a glandular structure related to functioning of the eye whereas the carotid labyrinth of fishes is concerned with the regulation of fluid pressure and oxygen supply to the brain.
Mortality of perch, Perca fluviatilis L., estimated from the size and abundance of egg strands
Authors: Lang C.
Published: January 2006

Egg strands of perch in Lake Geneva, Switzerland, during the spawning seasons of 1984, 1985 and 1986 were laid by the strong 1982 cohort. The abundance of these strands decreased from 1984 to 1986, whereas their modal size increased. These trends were used to estimate the decreasing abundance of the 1982 cohort and its increasing age. According to these data, total mortality within the 1982 cohort was 99% between the egg stage and 2 years, 78% between 2 and 3 years, 82% between 3 and 4 years.
Hypersensitivity in fishes: a review
Authors: Jurd R. D.
Published: January 2006

Immune hypersensitivity reactions, whereby secondary exposure to antigen elicits a heightened, accelerated immune response of sufficient intensity to cause tissue damage, are characteristic of well‐developed immune systems. Four (or five) types of hypersensitivity are usually recognized in Mammalia. In fishes, several hypersensitivity reactions have been recorded, particularly in Teleostei, but their mechanisms may sometimes indicate analogies rather than strict homologies with mammalian hypersensitivities. Type I anaphylactic hypersensitivity reactions have been described frequently in fishes, but the involvement of antigen as an initiating factor is problematical, as are the roles of homocytotropic antibody (if any), the vasoactive amine and other humoral factors implicated, and types of leucocyte. It is often difficult to distinguish between ‘classical’ anaphylactic hypersensitivity reactions and non‐specific inflammatory responses to invasive insults. The presence of a viable complement system in fishes (including the faculty to activate both the classical and the alternative complement pathways) together with NK cell‐mediated cytotoxicity and opsonizing antibody suggest that the feasibility of Type II cytotoxic hypersensitivity reactions can be entertained. Type III complex‐mediated hypersensitivity has not been described as such, although ‘neutrophil’ presence in inflammatory reactions suggests elements in fishes similar to an Arthus reaction. There are few reports of a piscine Type IV cell‐mediated, delayed hypersensitivity reaction; the existence of Type V stimulatory hypersensitivity has not yet been described. Tissue‐damaging immune hypersensitivity phenomena are associated with immunological sophistication, the ‘cost’ of effective immunity. Delayed hypersensitivity reactions in Mammalia are linked with expression of class II region genes of the MHC. In Teleostei, the existence of immune hypersensitivities might not be unexpected and would be concomitant with other features suggesting an advanced immune system, perhaps associated with the independent evolution or uncovering in these Osteichthyes of an MHC.
Development of a simple method to optimize the conditions for producing gynogenetic offspring, using albino rainbow trout, Salmo gairdneri Richardson, females as an indicator for gynogenesis
Authors: Kaastrup P. , Hørlyck V.
Published: January 2006

Gynogenetic offspring of rainbow trout were produced by means of UV‐irradiation of the sperm from a normal male. In order to indicate the destruction of the chromosomes of the sperms, eggs of albinos were used. The gynogenetic offspring showed no pigmentation while normal progeny showed pigmentation.
Phagocytosis by catfish neutrophils
Authors: Finco‐Kent D. , Thune R. L.
Published: January 2006

Channel catfish peripheral blood leucocytes were separated on a Percoll gradient to establish the phagocytic function of the neutrophils. Four fractions of leucocytes were formed on the Percoll gradient, including a fraction that contained 50–80% neutrophils at a density of 1.08–1.09 g ml−1 and a fraction that contained 10% monocytes at a density of 1.071–1.074 g ml−1. Phagocytic assays, using 3H‐uridine, showed that the two fractions had similar phagocytic indices, although neutrophils were less phagocytic than monocytes. Neutrophils were confirmed to be phagocytic when examined with transmission electron microscopy. Staining with 3,3‐diaminobenzidine‐tetrahydrochloride demonstrated peroxidase‐positive granules in the cytoplasm of actively phagocytic cells as well as peroxidase reaction products in a number of phagosomes containing bacteria. Phagocytosis of bacteria by channel catfish neutrophils was further confirmed by differential staining of external bacteria and cell surfaces with ruthenium red during the fixation process.
Stress in rainbow trout, Salmo gairdneri: effects upon phagocyte chemiluminescence, circulating leucocytes and susceptibility to Aeromonas salmonicida
Authors: Angelidis P. , Baudin‐Laurencin F. , Youinou P.
Published: January 2006

Rainbow trout were inoculated with Aeromonas salmonicida (AS) and 24 h later the tanks were drained off and the trout were kept for 30 min in 3 cm of water on the bottom of the tanks. This manipulation was considered as handling and anoxic stress. Twenty four hours later the stressed fish showed a leucopenia, mainly a lymphopenia. The chemiluminescence (CL) response of the head kidney phagocytes was lower in stressed fish. The inoculated‐unstressed fish showed a greater CL response than the controls (non inoculated‐unstressed). The mortality rate after AS inoculation was greater in the stressed than in the unstressed fish. When the stress was repeated four times for 15 min during 2 days, the CL response was lower; no difference was observed when the fish were stressed eight times for 15 min over 4 days.
The immunomodulating effect of the microsporidan Glugea stephani on the humoral response and immunoglobulin levels in winter flounder, Pseudopleuronectes americanus
Authors: Laudan R. , Stolen J. S. , Cali A.
Published: January 2006

A quantitative study of serum immunoglobulin levels and haemagglutination titres has shown that an injection of the microsporidan Glugea stephani caused a decrease in the humoral response of the winter flounder. These examples demonstrate the effect of temperature on the decrease in total IgM levels and haemagglutination titres in winter flounder simultaneously injected with either G. stephani or horse red blood cells.

Transfer of serum from fish injected with spores 3 weeks earlier may also implicate soluble serum factors, such as prostaglandins or leukotrienes, causing the observed decrease in serum IgM levels.
The immune response of the thick‐lipped grey mullet, Chelon labrosus (Risso, 1826), to metacercarial infections of Cryptocotyle lingua (Creplin, 1825)
Authors: Wood B. P. , Matthews R. A.
Published: January 2006

Grey mullet, Chelon labrosus, (60–100 g) have been found to respond immunologically to Cryptocotyle lingua, following a single exposure to 20000 cercariae, by the production of humoral antibody, sensitized pronephric leucocytes and cytotoxic serum factors. Antibody titres measured by passive haemagglutination reached a peak at week 4 with a ‐log2 titre of 16±S.E. 1.0, and titres of 10.7±S.E. 1.0 were still recorded after 10 weeks at the termination of the experiment. Cercarial agglutination was found unreliable as a rapid test. Pronephric leucocytes, sensitive to cercarial antigen when measured by the under‐agarose migration method, were detected between weeks 1 and 6, peaking at week 2. In vitro polarization was increased when cells were incubated with the antigen, but this increase was not significantly different between control and infected fish. Heat‐labile cytotoxic factors of immune sera have been demonstrated to whole cercariae in vitro, these factors being associated with structural damage to the tegument. Pronephros cells isolated from immune fish during each week of infection showed no evidence of adherence to cercariae or metacercariae in vitro. The results are discussed in relation to both host response and course of infection of the parasite.
Seasonal reproductive cycles in three commercially exploited fishes from the slope waters off New Zealand
Authors: Pankhurst N. W. , McMillan P. J. , Tracey D. M.
Published: January 2006

Reproductive cycles were investigated in orange roughy, Hoplostethus atlanticus, smooth oreo, Pseudocyttus maculatus, and black oreo dory, Allocyttus sp., from mid‐slope waters (600–1300 m) around New Zealand from 1982 to 1985. Orange roughly displayed a mid‐winter spawning period in July and August, whereas both dory species spawned in November and December. In all three species, the timing of spawning was consistent from year to year. Ovarian development in orange roughy and black oreo dory was found to be synchronous, with a single clutch of oocytes being matured for each spawning season. In males, testes of a given macroscopic stage were dominated by a single gamete stage, supporting the existence of a brief rather than prolonged spawning period. The possible relationship of spawning period to seasonal changes in the productivity of the surface water is discussed.
Changes in in vitro heart performance in rainbow trout, Salmo gairdneri Richardson, infected with Apatemon gracilis (Digenea)
Authors: Tort L. , Watson J. J. , Priede I. G.
Published: January 2006

In vitro, perfused, isolated heart preparations were used to determine the effects of a parasitic infection on the performance of the heart. Increase in preload in the uninfected hearts produced an increase in output flow and power, resulting mainly from increase in stroke volume and little change in heart rate. The heart rate of infected hearts (14.3 beats min−1) was slightly, but not significantly, lower than in controls (17.8 beats min−1). The cardiac output of infected hearts was 20–40% of that of the healthy hearts. This reduction will, in turn, lead to reduced oxygen transport to the tissues, and so to a reduction in metabolic scope. It is therefore probable that fish carrying this infection will have low food intakes, low growth rates and low activity levels.
Presence of chloride cells in gill filaments and lamellae of the skate Torpedo marmorata
Authors: Sala R. , Crespo S. , Martin V. , Castell O.
Published: January 2006

The morphology of chloride cells in the gill of the skate Torpedo marmorata is described from a light and an electron microscopic study. Chloride cells have been regularly observed in both the gill filament (or primary epithelium) and the lamellae (or secondary epithelium). Chloride cells located in the filament usually display convex apical regions with microvilli protruding amongst microridges of neighbouring pavement cells, whereas chloride cells in the lamellae are located between the two epithelial layers, and contact with the external milieu is via a narrow apical opening. Present observations are discussed in relation to data on the presence of chloride cells in the lamellae of marine teleost fish, and it is suggested that the occurrence of chloride cells all along the lamellae might be in some way inversely related to fish activity.
Poor water quality suppresses the cortisol response of salmonid fish to handling and confinement
Authors: Pickering A. D. , Pottinger T. G.
Published: January 2006

Confinement of brown trout in small troughs of static water for 1 h at a density of six fish 251−1 stimulated the hypothalamic‐pituitary‐interrenal axis and resulted in an elevation of plasma cortisol from basal levels (less than 2 ng m1−1) to about 100 ng m1−1, the degree of stimulation being dependent upon water temperature. Confinement at a density of 30 fish 251−1 resulted in a 50% suppression of this response. It is demonstrated that this effect is mediated by changes in water chemistry and not by crowding per se. Experimental manipulation of the water chemistry showed that reduced pH (7.1 → 6.3), elevated free CO2 (63 → 520 μmoll−1) or elevated ammonia (8 → 1300 μg 1−1 as total ammonia nitrogen) had no individual effects on the interrenal response to acute confinement. Elevated ammonia in combination with reduced pH significantly increased the plasma cortisol levels in response to acute confinement, whereas a combination of reduced oxygen (100 → 20% saturation), elevated free CO2 and elevated ammonia markedly suppressed (∼ 50%) the cortisol response of both brown trout and rainbow trout to acute confinement in a manner similar to that observed with trout at high densities. A compensatory increase in plasma cortisol levels was observed during the subsequent recovery of fish which had been confined for 1 h in water of poor quality. These findings are discussed in relation to the exposure of fish to multiple stresses and to the role of corticosteroids in the stress response.
The enzyme cytochemistry and composition of elasmobranch granulocytes
Authors: Hine P. M. , Wain J. M.
Published: January 2006

Peroxidase, alkaline phosphatase, acid phosphatase, β‐glucuronidase, α‐naphthyl acetate esterase (ANAE), α‐naphthyl butyrate esterase, naphthol AS‐D chloroacetate esterase, acetyl‐L‐tyrosine‐α‐naphthyl esterase (ATNE), tosyl‐L‐lysine‐α‐naphthyl esterase (TLNE) and periodic acid‐Schiff (PAS) were studied in 17 species of elasmobranchs in which granulocytes had previously been identified at the ultrastructural level.

Eosinophils, eosinophilic and neutrophilic granulocytes contained variable acid phosphatase, esterases and PAS, but they were strongest in neutrophilic granulocytes; particularly ANAE. Esterases were released into surrounding plasma and therefore probably function as ectoenzymes. In eosinophils and some neutrophilic granulocytes there were indications of weak peroxidase, but this could not be conclusively demonstrated. Alkaline phosphatase was diffuse between granules in some eosinophils of Pavoraja, and (β‐glucuronidase was diffuse in neutrophilic granulocytes of Etmopterus baxteri, otherwise granulocytes lacked these enzymes. Neutrophilic granulocytes stained moderately to strongly for ATNE and weakly and inconsistently for TLNE in Squalus acanthias and Dalatias licha. with a similar reaction in granular lymphocytoid and thrombocytoid cells of Galeorhinus ausiralis and Raja nasuta. The enzyme composition of these granulocytes is discussed.
The levels of liver metallothionein and zinc in plaice, Pleuronectes platessa L., during the breeding season, and the effect of oestradiol injection
Authors: Overnell J. , McIntosh R. , Fletcher T. C.
Published: January 2006

Wild plaice from two locations were examined for liver metallothionein and liver and serum zinc content, before, during and after the breeding season. During the early stages a number of females had very high liver metallothionein and zinc levels. Egg formation and ripening were accompanied by a reduction in serum zinc. In males, the metallothionein levels did not reach such high values and were not correlated with gonad development.

There was a correlation between the zinc concentration of the liver and the metallothionein concentration of the liver. Above the threshold value for metallothionein formation, approximately half the additional zinc was found in the metallothionein and half in non‐metallothionein pool(s).

Intramuscular injection of oestradiol 3‐benzoate into immature females caused a significant increase in liver weight but a depression in metallothionein concentration relative to the controls.
Quantitative histology of the seasonal changes in the gonads of summer whiting, Sillago ciliata
Authors: Goodall J. A. , Capra M. F. , Blackshaw A. W.
Published: January 2006

The histology of the gonads of free and captive summer whiting, Sillago ciliata, were compared to assess the potential of this fish for aquaculture. There were no qualitative differences between the free and captive males: both completed spermatogenesis through to spermiation. The captive females were non‐reproductive, reaching only the vitellogenic stage before the eggs were resorbed by atresia.

A reproductive score was devised to assess reproductive potential in the comparison of the two populations. The females in the captive population had lower reproductive potentials, as shown by the score, and started development a month later than the normal free population. The captive males had higher reproductive scores than the free fish but they were also not spawning and, therefore, the higher score indicated that this potential was not realized. The score provides a standard against which experimental results can be compared and subsequently assessed.
A comparison of the behavioural responses of parasitized and non‐parasitized three‐spined sticklebacks, Gasterosteus aculeatus L., to progressive hypoxia
Authors: Giles N.
Published: January 2006

Eighty sticklebacks (32 parasitized, 48 uninfected) were subjected to a serial reduction in dissolved oxygen (DO) concentration until they showed continuous aquatic surface respiration for longer than 10s (> 10s ASR). An analysis of results showed that (1) parasitized adult male and female sticklebacks reacted to low DO significantly earlier than non‐parasitized controls; (2) severity of parasite infection was significantly correlated with DO at which > 10s ASR occurred; (3) gravid, non‐parasitized females show ASR at a relatively high DO, with a threshold response similar to that of parasitized fish.

It is suggested that the metabolic respiratory demand of the parasitic tapeworm larvae causes the stickleback to modify its behaviour at lowered DO. This behavioural modification causes the fish to surface, where they are likely to be at risk from predatory birds. Field data on DO levels at the study site show that environmental conditions in the shallow lake margins approach the range required to affect the behaviour of heavily parasitized sticklebacks.
Crowding causes prolonged leucopenia in salmonid fish, despite interrenal acclimation
Authors: Pickering A. D. , Pottinger T. G.
Published: January 2006

Crowding for 3 weeks significantly reduced the coefficient of condition of both brown trout and rainbow trout. However, acclimation of the hypothalamic‐pituitary‐interrenal (HPI) axis, as assessed by changes in plasma cortisol levels, occurred within 6 days for brown trout and within 10 days for rainbow trout. Blood lactate levels were significantly reduced in the crowded fish of both species throughout the experiment. Sexual maturation of the male fish significantly elevated the number of circulating red blood cells in both species, reduced the lactate levels in brown trout and elevated cortisol levels in the rainbow trout. Despite the relatively rapid interrenal acclimation, the numbers of thrombocytes and lymphocytes in the blood of both species were significantly reduced during the period of crowding and it is concluded that changes in the composition of circulating blood cells are more reliable indicators of chronic crowding stress than are plasma cortisol levels. These findings are discussed in relation to the role of the HPI axis in suppressing the defence systems of salmonid fish during periods of chronic stress.
Migration of farmed adult Atlantic salmon with and without olfactory sense, released on the Norwegian coast
Authors: Hansen L. P. , Døsving K. B. , Jonsson B.
Published: January 2006

The dispersal and migration of farmed Atlantic salmon, Salmo salar, allowed to escape during the summer was studied. Three groups of 4–year–old fish of the River Imsa stock were released in coastal waters off south‐western Norway: one group, with functional olfactory organs, was released at a fish farm 4 km away from the R. Imsa; two other groups, one with transected olfactory nerves and the other with functional olfactory organs, were released in the sea 90 km from the R. Imsa. To compare them with the migration pattern of reared, large smolts of the Imsa stock, a group of 3 + smolts was released in the R. Imsa.

Adults of salmon released as 3–year–old smolts homed with high precision to the R. Imsa. Four– year–olds released in the sea were recaptured in the fjord and in the coastal current, the majority north of the places of release. Immatures migrated to feeding areas in the North Atlantic. Matures seemed to enter rivers at random when ready to spawn. There was no difference in migration pattern between anosmics and controls. The olfactory sense was not mandatory for entering fresh water. The results indicate that the homing behaviour of Atlantic salmon is not a direct consequence of a single imprinting of the smolts, and that there is not a direct genetic link for return to a particular river. The present results support the sequential imprinting hypothesis proposed by Harden Jones (1968).
Effects of anaesthetic MS 222 on the orientation of juvenile salmon, Oncorhynchus tschawytscha Walbaum
Authors: Taylor P. B.
Published: January 2006

Juvenile salmon, Oncorhynchus tschawytscha Walbaum, were trained to orientate in a direction (270°) and then anaesthetized with ethyl m–aminobenzoate methane sulphonate (MS 222) in a test to determine whether anaesthesia affected the learnt orientation.

Before anaesthesia the control group of twelve fish showed a mean unimodal orientation of 264° and a bimodal axis of orientation of 258°/78° with a confidence limit (second order analysis) of 218°←→285°. After administration of MS 222 nine out of ten fish showed marked changes in orientation and random behaviour, persisting in two fish for more than 14 days. The mean of means unimodal orientation, after anaesthesia, was 337° (random) and the bimodal axis of orientation was 337°/157° (random).

Eight weeks after completion of the anaesthesia trial the fish were retested. Each fish, except one, showed a mean bimodal axis of orientation that fell within the confidence limit of the control. The mean axis of orientation for ten fish over a 3–day period was 270°/90°, (r) = 0.28.

The results support the view that the reference orientation in this study (270°) was a learnt, not an innate directional preference. The effects anaesthesia may have on salmon behaviour during migration are discussed.
Oriented swimming at an angle to light in a schooling characid, Moenkhausia dichrowa Kner
Authors: Levin L. E. , Belmonte P.
Published: January 2006

Two groups each of approximately 100 Moenkhausia dichroua, a schooling characid, showed a long–lasting, constant–oriented swimming when placed in a light–centred circular channel. This apparatus consists of a 1–m diameter circular channel illuminated by either a central or a peripheral light system, so that the light angle is constant all around the channel. With the central light at a fixed angle, fish swam for several months in one direction and reversed direction at a certain date. When the light angle was increased by 10° every other day between 0° (horizontal) and 90° (vertical), swimming direction was reversed at a particular angle in each experiment. This response to artificial light suggests that this small schooling fish uses the sun as an orientation clue in its seasonal migrations.
Circuli spacing and annulus formation: is there more than meets the eye? The case for sockeye salmon, Oncorhynchus nerka
Authors: Barber W. E. , Walker R. J.
Published: January 2006

This study describes a pattern of circulus spacing on the scales of sockeye salmon, Oncorhynchus nerka, which has not been reported previously. The average distance between circuli formed during the second year of ocean growth is much less than that of first year or in subsequent years. This pattern was persistent for fishes of two river systems, six year–classes and two age groups (2.2 and 2.3) and was due to summer growth. Statistical analyses were conducted only on age 2.2 fish because of small sample sizes in four of the six years for age 2.3 fish. There were significant (p < 0.05) differences in the distance between circuli formed in the summer and in the two stocks for various years at sea. No significant variation in average spacing between circuli was explained by oceanic temperatures.

Annuli were formed between November and January. However, oceanic temperatures were declining at this time and do not reach minima until April. Thus, annuli are formed about the time of the equinox and during a declining temperature regime. We hypothesize that the pattern of circuli spacing and annulus formation are responses to photoperiod and food availability which the fish experience during their existence at sea.
Morphometrics of gills during growth and development of the air‐breathing habit in Colisa fasciatus (Bloch and Schneider)
Authors: Prasad M. S.
Published: January 2006

Gill area and other component parameters of Colisa fasciatus during early life were measured for fish larvae divided into two groups (a) exclusively aquatic and (b) bimodal breathers. Statistical analyses of the data in relation to body size yielded two significantly different straight lines (one for aquatic and other for bimodal breathers) for each parameter. Morphological examinations of gill arches indicated that an increase in the gill area was brought about mainly by an increase in the filament length. The higher slope value (2.41) of gill area in the aquatic phase than that in the bimodal phase (b= 0.80) is suggestive of a higher weight‐specific metabolism in the younger larvae. A heterogenous growth pattern during early ontogenesis of the fish results in intraspecific variation in the gill dimensions which might have been influenced by the acquisition of the air‐breathing mechanism in the post‐larval stage, besides ecological factors.
The mechanism of wound repair in the skin of juvenile Atlantic salmon, Salmo salar L., following hydrocortisone implantation
Authors: Roubal F. R. , Bullock A. M.
Published: January 2006

Juvenile Atlantic salmon, Salmo salar L., were implanted with different amounts of the stress hormone hydrocortisone in cocoa butter and wounded with small surgical incisions on the ventral and dorsal surfaces. Hydrocortisone had no effect on epidermal migration which closed the wound by 8 h. Although low levels of hydrocortisone had little effect on wound healing after 3 months, high levels retarded dermal repair, particularly fibrosis and closure of the stratum compactum. Ultrastructural findings indicated that fibroblast activity was impaired. The implications for aquaculture are discussed.
The food of the Nile perch, Lates niloticus (L.), after the disappearance of the haplochromine cichlids in the Nyanza Gulf of Lake Victoria (Kenya)
Authors: Ogari J. , Dadzie S.
Published: January 2006

After the disappearance of the haplochromine species in the Nyanza Gulf of Lake Victoria as a result of predation by Lates niloticus, the latter has turned its attention to aquatic invertebrates and other fish. Changes in the diet of the Nile perch with increase in its size have been observed: young L. niloticus preyed mostly on invertebrates, including crustaceans and various small aquatic insects; large, immature L. niloticus supplemented the invertebrate diet with both young and small fish; adults above 80 cm total length were mainly piscivorous. L. niloticus feeds on fish prey of about one third its own length.

The tendency of L. niloticus to switch from one prey item to another, depending on availability, is reported; e.g., in the Nyanza Gulf, the prey diet has shifted from the haplochromine to Caridina nilotica and L. niloticus juveniles.
Growth, mineral uptake and skeletal calcium deposition in brown trout, Salmo trutta L., yolk‐sac fry exposed to aluminium and manganese in soft acid water
Authors: Reader J. P. , Dalziel T. R. K. , Morris R.
Published: January 2006

In 30‐day exposures in artificial soft water medium, survival of brown trout alevins was not affected by low pH (4.5,4.8, 5.4), by low calcium concentration (10.25 μmol l−1) or by manganese (≤20 μmol l−1), but was impaired by aluminium (6–8 μmol l−1) at low calcium concentration (10 μmol l−1) irrespective of pH (4.5 or 5.4). Manganese (6.6, 20 μmol l−1) impaired net calcium uptake and calcium deposition in the skeleton at low calcium concentration (25 μmol l−1) irrespective of pH. Aluminium (2–8 μmol l−1) impaired gross development, net uptake of calcium, potassium and sodium, and calcium deposition in the skeleton, and slightly increased the net loss of magnesium, some of these effects being more severe at calcium concentration 10 μmol l−1 than 50 μmol l−1, and some more severe at pH 5.4 than pH 4.5. Net uptake of calcium and sodium were impaired at low pH (4.5, 4.8), and skeletal calcium deposition was impaired at low calcium concentration (10 μmol l−1), but these effects of low pH and low calcium concentration were slight compared with those of the trace metals. The possible role of trace metals in reports of the deleterious effects on fish of low pH levels is discussed.
Corneal iridescence in fishes: light‐induced colour changes in relation to structure
Authors: Shand J.
Published: January 2006

The iridescent corneas of 31 species of teleost fish were investigated for light‐induced colour changes. Thirteen were found to shift the spectral reflection of their corneas to shorter wavelengths when dark‐adapted and to longer wavelengths when illuminated. The structures of the corneas were examined by electron microscopy and categorized according to the type of structure modified to produce the iridescence. Six previously identified structures were found and a seventh type is described here.