摘要:

A male accessory sex organ, termed the juxtatesticular body (JTB), is located in the posterior part of the trunk, outside the coelomic cavity, lying ventral to the urinary ducts and dorsal to the urinary bladder and testes in jawfishes. Its microscopic structure is unusual for an accessory sex organ because it is highly vascularized, organized in small follicles, and ductless. The embryological origin of the JTB and the development of the urogenital apparatus was studied in juveniles ofOpistognathus whitehurstiiandO. maxillosus. Both sexes possess a structure located outside the coelomic cavity in the posterior part of the trunk. In females this structure showed the same histological organization as the kidney, however in males it was different and recognized as the JTB. The degree of development of the JTB followed that of the testes, being represented in youngest recognizable males only by a small mass of mesenchymal cells while it was fully developed in males with spermatogenic testes. In most immature males renal structures, such as tubules and glomeruli, were found in the dorsal part of this structure. On the basis of anatomical and cytological features a nephrogenic origin for the JTB is proposed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01144.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Food consumption and growth rates of 7–28‐day‐oldMenidia beryllinawere measured in response to natural ranges of temperature and prey availability. Feeding level, temperature and age all had significant effects on growth rate, although the effect of feeding level explained most of the variance. Feeding level also had a significant effect on gross growth efficiency, but temperature and age did not. Absolute growth rates (mg per day) increased dramatically with temperature, feeding level, and age. Variability in growth was greatest for fish feeding at the lowest feeding level. For a given fish weight, temperature had a positive effect on consumption rate, and maximum consumption (Cmax) of any treatment combination reached 75% body weight per day. Maximum growth rate was estimated at 24.6% body weight per day, and gross growth efficiency reached an estimated maximum of 0.375 at an ingestion rate of 25% body weight per day. Starved larvae lost on average 5.4% body weight per day and larvae required 6.4% body weight food consumption per day for maintenance. Multiple regressions of feeding level, temperature, and age/size on instantaneous growth rates indicated that increases in temperature increased maintenance requirements and required that fish consume a greater proportion ofCmaxto attain maximum growth. Growth rates decreased with increases in temperature for fish eating a specific weight of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01145.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

When swimming at low speeds, steelhead trout and bluegill sunfish tilted the body at an angle to the mean swimming direction. Trout swam using continuous body/caudal fin undulation, with a positive (head‐up) tilt angle (0, degrees) that decreased with swimming speed (u, cm s−1) according to:0=(164±96).u(−1.14±0.41)(regression coefficients; mean±2s.e.). Bluegill swimming gaits were more diverse and negative (head down) tilt angles were usual. Tilt angle was −3·0 ± 0.9° in pectoral fin swimming at speeds of approximately 0.2–1.7 body length s−1(Ls−1; 3–24 cm s−1), −4.5 ±2.6° during pectoral fin plus body/caudal fin swimming at 1·2–1·7 L s−1(17–24cm s−1), and −5.0± 1.0° during continuous body/caudal fin swimming at 1.6 and 2.5 L s−1(22 and 35cm s−1). At higher speeds, bluegill used burst‐and‐coast swimming for which the tilt angle was 0.1±0.6°. These observations suggest that tilting is a general phenomenon of low speed swimming at which stabilizers lose their effectiveness. Tilting is interpreted as an active compensatory mechanism associated with increased drag and concomitant increased propulsor velocities to provide better stabilizing forces. Increased drag associated with trimming also explains the well‐known observation that the relationship between tail‐beat frequency and swimming speed does not pass through the origin.Energydissipated because of the drag increases at low swimming speeds is presumably sma

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01146.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The population ofP. filamentosusaround the periphery of the Mahe Plateau was studied using data derived from commercial handline fishing operations between November 1989 and December 1990. Sex ratio was close to one. Fork length was in the range 25.6–79.8 cm: at first sexual maturity, 36–38 cm for females and 40–42 cm for males. Spawning occurred from October to April peaking between February and April and in November.The length (f.l., cm)–weight (kg) relationship wasW=0.00005353 ×f.l.2.7004. The von Bertalanffy growth parameters, estimated from length frequency data, wereK=0.2875 andLinf=81.7 cm. Mortality rates, estimated from length converted catch curve analysis, wereZ=0.811,F=0.277 withM=0.534 derived from Pauly's empirical formula. Jones' length cohort analysis gave an estimate ofF=0.294 for the fully exploited part of the stock, and a density of 2.59 t km−2for the periphery of the plateau from 75 to 150 m depth. The Lesley constant catchability model, applied to the results of intensive fishing around isolated banks, derived a mean density estimate of 2.99t km−2. The sustainable yield was estimated to be 233–268 tonnes per annum and the catch in 1990

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01147.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Lectin histochemical study was performed on the distal intestinal mucosa of the rainbow trout. A panel of 25 biotinylated leetins for detection of sugar residues and oligosaccharide sequences of glycoconjugates on Bouin's solution‐fixed paraffin embedded sections were used as probes. The avidin‐biotin‐peroxidase complex (ABC) was used to visualize the binding sites of lectins. A rich supply of carbohydrates was detected in this gut mucosal region. Marked differences in lectin labelling of goblet cells and enterocytes (absorptive cells) probably reflect various functional activities. The results are compared with those (scarce) obtained from other teleosts. Species differences in carbohydrate residue composition may be related to various feeding habits. The roles of posterior intestinal glycoconjugates in host‐parasite interaction, macromolecular ingestion and immunological implications are di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01148.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Horizontal starch gel electrophoresis was employed to analyse genetic variation, at 19 isozyme loci, in six putatively related species of gobies (Brachygobius aggregatus, B. doriae, Pandaka lidwilli, Pseudogobius olorum, Pseudogobiussp. andRedigobiussp.), using seven other gobiine species as an outgroup. Allozyme data was analysed both cladistically and phenetically, all treatments confirming the monophyly of the group.Pandakais confirmed as the sister genus toBrachygobius, these genera forming a crown group, withRedigobiusandPseudogobiusforming successive sister groups. This scenario is in agreement with morphological hypotheses of phylogeny. However, this lineage appears to be relatively unrelated to other groups within theGobiinae

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01149.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Incidences of gross morphological disorders in barbel (Barbus barbus) wereinvestigatedin three rivers in southern England. The water quality at the sites chosen for study on the Rivers Teme, Kennet and Lee were classified (according to the criteria of the National Water Council, 1978) as 1A, IB and 2, respectively. Generally, low levels of gross morphological abnormalities were seen in fish caught in the Teme and Kennet, although there were incidences of ocular disorders and extra barbules in 10 and 7%, respectively, of the Kennet fish. No tumours were found in barbel from the River Teme whereas there was a 2% incidence in the Kennet fish. In contrast barbel from the River Lee showed high levels of all the gross morphological disorders, especially haemorrhagic patches on the ventral surface (36%) and ocular disorders (72%). Tumours were seen in 25% of the barbel caught in the River Lee. The incidences of most of these gross morphological disorders did not appear to be age related. The possibility that these disorders were related to water quality is discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01150.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The diel rhythms in metabolic rate (MR) and activity level (AL) were measured for single post‐hatching dogfish (weight range, 2.76–10.61 g) at 15° C by the indirect calorimetric method of rate of oxygen consumption (VO2) and by video‐observation respectively, over a period of 72 b. The meanVO2increased from 62.0 (s.e. 2.9) mg O2kg−1h−1in the daylight hours to 85.5 (s.e. 3.1) mg O2kg−1h−1during the dark (light regíme, 12 h L: 12 h D). The simultaneous measurement ofALalso showed mean night elevation from 0.6 (s.e. 0.2) min h−1in the light phase to 14.5 (s.e. 1.6) min h−1during the darkness. Bimodal nocturnal activity (BNA) was exhibited by the post‐hatching dogfish within the 12 h dark period, withVO2increasing from 71.4 (s.e. 2.8) mg O2kg−1h−1before 01.00 hours to 99.5 (s.e. 4.2) mg O2kg−1h−1after 01.00 hours. Similarly,ALalso increased from 8.9 (s.e. I.7)min h−1before 01.00 hours to 21.1 (s.e. 2.8) min h−1after 01.00 hours. The importance of the results presented to the natural behavioural ecology of t

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01151.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The diel rhythm of emergence from the gravel and displacement downstream has been studied in three salmonoid species: brown trout (Salmo truttaL.), Atlantic salmon (S. saiarL.) and grayling (Thymallus thymallusL.). Grayling emerged in the morning but delayed downstream displacement until the night, while theSalmospecies emerged just before downstream displacement chiefly at night.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01152.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Parameters of shelters utilized by GobiuscruentatusandThorogobius ephippiatuswere measured,in situ, using SCUBA. Both species exhibited non‐random use of shelters, withT. ephippiatus, the smaller of the two species, utilizing significantly larger shelters thanG. cruentatus. Interspecific size differences and competitive exclusion are not considered to be of major importance in the observed differential utilization of shelters. The size of shelters utilized by both species is suggested to be influenced by current velocitie

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01153.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY