摘要:

Certain herbivorous fishes are well known for morphological specializations enabling trituration; such as scarids with a pharyngeal mill and mullets with a gizzard‐like stomach. However, utilization of plant foods by fishes is limited by these animal's digestive capabilities, most notably the apparent lack of cellulose digesting enzymes. Fishes possessing a grinding mechanism are able to break open plant cells for digestion. But how fishes without grinding mechanisms make plant cell contents accessible to digestion is unknown. These fishes include many acanthurid and pomacentrid species which are among the most abundant on reefs.Another mechanism for rupturing plant cell walls has been recently proposed, namely lysis by gastric acidity. This study surveyed stomach and intestinal pH for 17 herbivorous species at Fanning Atoll, Central Pacific and two species from St Croix, Caribbean with additional data for seven selected carnivorous species. The herbivorous fishes included acanthurids (surgeonfishes), mugilids (mullets), pomacanthids (angelfishes), pomacentrids (damselfishes) and a scarid (parrotfish). The effect of different pH concentrations and trituration was examined experimentally for eight common Pacific marine algae including two reds, two blue‐greens, two greens, one brown, and the algal mat complex from inside damselfish territories.Fishes, possessing morphological adaptations for trituration, ingested quantities of calcium carbonate material and did not contain gastric acidity low enough to lyse algal cell wells. However, fishes without grinding mechanisms but with defined stomachs have gastric pH values from 2.4 to 4.25 which can be as effective as trituration in releasing algal cell contents of certain algae. These results are considered in a review of previous studies of herbivory in fishes. The trophic relationship between fishes and algae of specified morphologies are predicted by extrapolation from the experimental results on algae vulnerable to acid lysis or triturat

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05842.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A comparison of mean bottom trawl stock densities (kg ha‐1) from 19 UNDP 1969/70 tows, 69 EAFFRO 1975 tows and 167 fourth quarter FFRI 1977 tows in the inner Kavirondo Gulf of Lake Victoria showed the following changes from 1969/70 to 1977.1A reduction in mean stock densities forBagrus docmac, Clarias mossambicus, Haplochromisspp.,Protopterus aethiopicus, Schilbe mystusandSynodontisspp.2An increase in mean stock densities forLates niloticus, Tilapia niloticaandT. variabilis.3No change in mean stock density forLabeo victorianus.4NoT. esculenta or Mormyrus kannumecollected in 197

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05843.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A functional T cell population matures rapidly in the carp,Cyprinus carpioL. At 22 ± 1° C, the thymus first appears at two days post‐hatch and becomes actively lymphopoietic by day 5. The kidney, which contains haemopoietic tissue at day 2, shows differentiating lymphoid cells by day 6–8. The spleen first appears at day 5 but develops more slowly than the kidney.Lymphocytes are capable of effecting allograft rejection as early as day 16 post‐hatch but the number of cells invading a skin allograft is low if the graft is applied in the first month of life. Thereafter the numbers increase rapidly, possibly correlated with the large increase in lymphocytes in the pronephric and mesonephric kidneys at th

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05844.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Triploid male plaice,Pleuronectes platessa, and plaice x flounder,Platichthys flesus, hybrids produced from cold‐shocked eggs were reared to maturity at three years of age. The testes of triploid hybrids were similar in macroscopic appearance and size to those from control fish but in histological section spermatocyte and spermatid cell formation was grossly abnormal. In two fish the majority of cells appeared to be aborted spermatids and spermatocytes although there were some spermatozoa with enlarged heads and thick bent flagellae.The testes of mature triploid plaice were similar to controls both in shape and size and in histological section. Spermatocyte and spermatid cell formation was normal, apart from an increase in cell and nuclear size, and fully motile spermatozoa were produced from several fish. Plaice eggs fertilized with semen from triploids showed a slight reduction in fertility compared with controls but developed normally to gastrulation with little mortality. Beyond gastrulation there was increasing mortality associated with abnormalities in the appearance of embryos. Few hatched and none of these survived longer than 48 h. The value of triploidy in fish farming is briefly discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05845.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The structure of the glandular pseudobranch of the air‐breathing fishAnabas testudineusis described on the basis of light and electron microscopy. It is shown that the pseudobranch has the same basic structure as a typical gill, although in this case it is not freely exposed to the water.Individual secondary lamellae can be recognized in which well‐defined, but narrow, blood channels are present between typical pillar cells. The epithelial layer is mainly represented by enlarged mitochondria‐rich cells which constitute a large proportion of the whole organ. Mitochondria‐rich cells contain an abundant endoplasmic reticulum which is in close contact with the mitochondria and becomes concentrated near the vascular borders of the cell and opens directly into the basement lamina.The presence of numerous pinocytotic vesicles in the enlarged pillar cell flanges may transfer material to the blood channels. The precise nature and role of any materials released in this way remains to be inves

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05846.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The relationship between the temperature requirements of some fish species, using published data for growth optima, final preferences and lethal limits were examined. A good correlation was found and it is suggested that the data established gives a good estimate of the temperature promoting maximum growth. Determinations of final preferenda are easily conducted in the laboratory and could therefore be used to give rapid assessments of optimum growth temperatures of potential culture species. The practical application of such measurements is discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05847.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Hybrid carp and grass carp from the zygote to the prolarval stage and adults were compared to establish distinguishing characteristics. Zygote diameter, yolk sac and embryo length were not different between the fishes. Body pigmentation patterns showed distinct separation among the prolarvae of the hybrids and grass carp. Total and preanal myomeres were higher in grass carp larvae than in the hybrids. The grass carp and hybrid larvae also differed in 38% of the proportional morphometric characters.Average meristic counts of adults were significantly higher in hybrids compared with grass carp. Adults of the two fishes showed significant differences in 63% of the proportional morphometric measurements. Gill raker counts showed no overlap and lateral line scales were smaller and more numerous in the hybrid adults.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05848.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The seasonal distribution ofEchinorhynchus salmonisMüller, 1784 among rainbow smelt,Osmerus mordaxMitchell, in Lake Michigan was studied.Echinorhynchus salmonisshowed no pronounced seasonal periodicity in infection prevalence and intensity or development and maturation in rainbow smelt. Worms were predominantly overdispersed with the negative binomial distribution being the best descriptive model. It is suggested that the observed monthly distributions were primarily determined by climatic and other ecological conditions affecting the heterogeneity in the temporal and spatial distribution of infection sources, i.e.Pontoporeia affinis(Lindstrom) (Amphipoda) and alewife,Alosa pseudoharengus(Wilson), and in the feeding behaviour of rainbow smelt

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05849.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Age and growth patterns of luderick,Girella tricuspidata(Quoy and Gaimard), taken in the Moreton Bay net fishery are described. Scales have prominent annuli which are formed during the period May‐July. The mean body length is similar for males and females, except for age class III where female fish are significantly larger. This probably results from the early movement of faster growing females onto the fishing ground. The scale method and length‐frequency analysis both indicate that the variation in body lengths in each age class is large. The length‐weight relationship was obtained and relative condition factor was found to be highest in July which corresponded with the peak in gonosomatic

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb05850.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY