摘要:

Two recently developed morphometric methodologies, multiple group principal components analysis (MGPCA) and the box truss method of body form transformation are used to re‐address whetherAtherina boyeriRisso, 1810 andA. presbyterCuvier, 1829 are morphometrically distinct. The results revealed that morphometric differences are present betweenA. boyeriandA. presbyter, consistent with expectations of the existence of two species.Females of the two species were clearly discriminated into two separate groups because the within‐group covariances of several characters within populations of each species were different between species i.e., the covariances were heteroscedastic. The occurrence of heteroscedasticity within the data, although statistically invalidating the results of canonical variates anslysis, indicated there to be a large amount of morphological variation between females of the two species. Males were differentiated as a result of differences in body ‘shape’, particularly the relationship between head ‘shape’ and body ‘shape’.Several probable reasons are given for the failure of a previous study to differentiate the two species. The data rejects the synonymy of the two species in support of the continued use of the taxaA. boyeriRisso, 1810 andA. presby

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02663.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Squamation and scale morphology provide interesting characters for phyletic analysis within the Cichlidae. It is not known, however, to what extent these characters are genetically fixed or determined by environmental parameters. To clarify this point, a study onSarotherodon galilaeuswas conducted. This species has an extensive distribution and lives in markedly different environments. Most scale characters were found to be remarkably stable within the species. The only large variations occur in scale counts, extent of caudal fin Squamation, number of circuli and radii, and the extent of scale granulation. The Squamation pattern, the form of the circuli and radii, the shape of interradial rostrad projecting tongues, the denticles on the circuli in the rostral field, and especially the kind of granulation in the caudal field is similar in all specimens examined and is also retained in fish bred in aquaria for several generations. Thus it seems justified to assume that these characters are strongly determined by genetic factors and that their analysis can be useful in the determination of phyletic relationships.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02664.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Myxobolus artusinfection of carp is reported for the first time from Japan. In most cases, it took the form of interfibrillar pseudocysts in the skeletal muscle, some showing abnormal growth, imperfect encapsulation of the parasite by the host connective tissue and irregular development of the ectoplasm. Such atypical pseudocysts probably ruptured before the completion of sporogenesis, causing lysis of adjacent muscle fibres. Intrafibrillar pseudocysts were also present. After spore formation was complete or atypical pseudocytes were ruptured host reaction was initiated. Spores were phagocytosed and transported to the melanomacrophage centres in the kidney, liver, spleen etc. Phagocytosed spores were also observed in the capillaries and epithelial tissues of various organs, suggesting that the spores were transported there from the skeletal muscle through the host vascular system. They are thought to be discharged from the host through the skin and intestine.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02665.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The routine metabolism of the guapote tigre,Cichlasoma managuense, was measured for a weight range between 6 mg and 800 g and at three different temperatures: 22, 27 and 32° C. Equations describing the routine metabolism of the guapote in relation to fish weight and temperature were calculated. The results are compared with those of other stenothermal tropical species

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02666.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The morphology and biometry of the gill rakers have been studied by scanning electron microscopy in juveniles and adults of four species of mullet (Liza aurata, Liza, saliens, Liza ramadaandChelon labrosus).A detailed description of the structure and orientation of gill rakers and related structures is presented for the four species and the two sizes considered, showing broad similarities between them. However a biometrical study has shown significant differences between juveniles and adults of the same species as well as between juveniles or adults of different species and sizes. The possible relationship of such differences with the capacity for gathering food is discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02667.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Three species of sticklebacks (Apeltes quadracus, Gasterosteus aculeatus, andPungitius pungitius(n= 236) were collected from five ponds on Sable Island. The nematodesPseudoterranova decipiens, Contracaecumsp.,Paracuaria adunca, andCosmucephalus obvelatus, and the cestodeDiphyllobothrium ditremumparasitized three‐spined sticklebacks (G. aculeatus) and four‐spined sticklebacks (A. quadracus) inhabiting four brackish water ponds. All the parasites exceptP. decipiensinfected nine‐spined sticklebacks (P. pungitius) from a freshwater pond. In addition, the cestodeSchistocephalus pungitii, the copepodThersitina gasterostei, and the monogeneanGyrodactylus canadensisoccurred in nine‐spined sticklebacks from the freshwater pond. The two cestodes, the copepod, and the sealworm,P. decipiens, were the most common parasites encountered. The remaining helminths were relatively rare. Most of the parasite species were larval forms which use gulls or seals as definitive hosts. These parasites probably colonized Sable Island with their definitive hosts, whereas only two species (T. gasterosteiandG. canadensis) successfully colonized the island ponds with their fish hosts. The low parasite species richness encountered is attributed to the impoverished nature of the host fauna of Sable island, and the difficulty of colonization as a result of the island's isolation with respect to the m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02668.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Protein digestibility and food conversion were determined in groups of Atlantic salmon (Salmo salarL.) and Arctic charr (Salvelinus alpinusL.) with or without the trypsin‐like isozymeTRP‐2*92. Determinations were made at two salinities, 0 and 27 ppt; at two temperatures, 6 and 10° C and on large (200 g) and small (30–90 g) fish. The overall digestibility of protein was found to be 81.4±0.2% and was unaffected by the presence of the isozyme or the other variables. The feed conversion ratio of Atlantic salmon possessingTRP‐2*92was observed to be significantly lower with significantly higher specific growth rate than in fish without thi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02669.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Anadromous whitefish [Coregonus lavaretus(L.)] yolk‐sac larvae were marked with a radioactive strontium isotope,85Sr. Before marking the method was tested in accumulation‐elimination tests using various strontium concentrations. The first‐phase effective half‐life of85Sr in yolk‐sac larvae was 4 days. The mean85Sr radioactivity was 81 Bq per larva at the day of release and the half‐life of the slow component was 51 days, so the strontium label was easily detected up to 60 days after marking. The larvae were released into the River Simojoki about 12 km upstream from the river mouth and recaptured from early May to the end of July. Marked larvae were found at the river mouth 12–13 days after release, while the last marked fish in the river were found at 16 days. It is likely that all leave the river within 2 to 3 weeks post‐hatching. Two months after marking some larvae had attained a distance of 10 km from

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02670.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Sturgeon fingerlings of 20.0 g at a water temperature of 18.20° C, fed for 130 min and consumed 6.5% of their body weight when the food concentration was 2 g m−2. At 38 g m−2the fingerlings stopped feeding after 45 min but consumed 9.0% of their body weight. As satiation approached the intervals between successive food intakes increased and feeding rate decreased. The rate of feeding was inversely proportional to the amount of food already consumed, and an equation describing this relationship is given. During the first minutes of feeding the ration size was directly proportional to food concentration but with further feeding the relationship changed. The equations of Ivlev and Rashevsky were close approximations to the relationship between ration size and food concentration. At a density of 12 individuals/m2the feeding duration and ration size was low in comparison to single fingerlings and to fish fed at higher densit

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02671.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

To establish the time required for fish to acclimate to experimental conditions, comprising holding within a spatially restrictive environment, rainbow trout were transferred from rearing tanks (1500 1) to smaller volume holding tanks (50 1). The fish were maintained singly, in pairs, in groups of five fish, and in groups of 10 fish, and selected indices of physiological stress were monitored at intervals following the onset of confinement. In all cases transfer and confinement provoked a stress response in the fish, indicated by significantly elevated plasma cortisol levels, and significantly reduced numbers of circulating lymphocytes. Recovery of these parameters to levels similar to unstressed control fish, was most rapid among the fish confined singly, requiring 2 to 4 weeks, although weight gain, indicative of feeding, was apparent within 1 to 2 weeks. Acclimation of the fish confined as pairs was severely confounded by the development of hierarchical relationships between the fish. This resulted in some individuals displaying rapid acclimation and growth, in contrast to other fish within the groups which failed to acclimate, exhibited signs of chronic stress, and ultimately succumbed to bacterial infections. Similar, though less severe, evidence of social stress was observed among the fish confined as groups of five. A decline in the coefficient of variance for weight within the fish confined as groups of 10 suggested an absence of growth inhibition due to social interaction among these fish. The implications of these results for experimental design are discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02672.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY