摘要:

This paper describes specimens of naturally occurring hybrids of silver bream x bronze bream and silver bream x roach from Lincolnshire and South Humberside waters.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03913.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The swimbladder‐acoustico‐lateralis system of the Atlantic menhaden,Brevoortia tyrannus, is described and compared with that of the Atlantic herring,Clupea harengus. The system develops in the larva at a much earlier stage than the herring, being functional by about 2 mm tl. The volume of the gas‐filled pro‐otic bullae is five times that of the herring, and the gas ducts to the swimbladder, instead of being short and separate, are three times the length and join to form a common duct well in front of the swimbladder. The menhaden swimbladder is baggy and totally compliant when subjected to pressure changes. There is no toughened anterior end as in the herring, but the swimbladder is steeply angled in the body cavity, causing gas to collect at the anterior end after a pressure increase, unless the fish is diving very steeply. The guanine content of the swimbladder is comparable with that of the herring and makes the wall very impervious to gas diffusion. When subjected to quick pressure increases and decreases, the pro‐otic membrane returns to its flat position with a time constant of 31‐44 s. Very large quick pressure changes of about 3 atm burst the pro‐otic membrane in adult fish but

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03914.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Female capelin,Mallotus villosus villosus, were sampled at various times of the year from the Barents Sea and preserved for histological examination. The current paper describes various stages of development of capelin oocytes. The description can be used as the basis for the preparation of a maturity scale to be used in the field, using whole oocytes and low power microscopy. The development of the oocytes is classified into 10 stages according to morphological characters. First growth phase oocytes are always present in the ovaries, showing that female capelin have a potential for several spawnings. Second growth phase oocytes grow synchronously. Oocytes of‘ Yolk vesicle stage I‘ are suggested to be the first stage of second growth phase which lasts for somewhat less than one year, and ends with spawn

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03915.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A study has been made of the dietof Scymnorhinus lichain Catalan coastal waters by means of the analysis of the stomach contents of 97 specimens caught at depths ranging from 300 to 600 metres during a 12 month survey. The annual coefficient of repletion is 80%. Bony fishes form the basic group in the diet for all seasons: they are followed by sharks, crustaceans and cephalopods, which are secondary. As the size ofG. lichaincreases, there is an increase in the frequency of crustaceans and sharks in the stomach contents and a drop in the frequency of cephalopods. Bony fishes are slightly more frequent in the larger specimens. The males have a higher coefficient of repletion and a higher average of prey per stomach and show a greater preference for sharks and bony fishes.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03916.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Bovine growth hormone (bGH), administered intramuscularly at 20 μg‐1every 2 weeks, produced faster somatic growth in rainbow trout fingerlings to approximately 30 cm than in those not receiving the hormone. Both groups were maintained at 12° C, with a photoperiod of 16 : 8 LD, and onad libitumrations daily. The faster growth was characterized by a controlled increase in input of fibres into the mosaic muscle (which dominates the body tissues by its bulk). It is not known if the enhanced input of fibres is an example of the known ability of the mosaic fibre mass to respond with flexibility and precision to widely differing somatic growth rates, or is a specific consequence of the growth hormone. In other fingerling trout receiving 4‐5% daily rations and consequently growing slowly, bGH did not stimulate growth or evidently modify fibre input dynamics. Body dry weight, and condition (K), though modified by rations and growth rate, evidently had little effect on muscle fibre g

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03917.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Aquarium observations and gut analyses of the spined loach,Cobitis taenia, suggested the use of a technique by which small items of food could be removed from an almost constant stream of substrate, taken in through the mouth and passed out through the gills. The small amount of indigestible substrate present in the gut contents indicated a very high efficiency level for the process. Photographic investigation revealed a two phased feeding cycle based on the respiratory pumps, consisting of an induction/separation phase and an expulsion/swallowing phase. A morphological study showed large concentrations of mucus secreting goblet cells on the roof of the anterior buccopharyngeal cavity. Other morphological adaptations were noted which resulted in a narrowing of the anterior buccal cavity and a widening of the posterior part along with an increase in the distance between the gill rakers. In the light of this information a method of separation based on differential densities of particles being trapped in a constant stream of mucus is postulated.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03918.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effects of acute and chronic cadmium exposures on ascorbic acid concentrations and cadmium accumulation in the tissues of juvenile mullet,Mugil cephalus, are described. Hepatic ascorbic acid reserves were maintained in untreated mullet fed a diet containing ascorbate, but decreased 60% in individuals exposed to 10 mg Cd 1‐1for six weeks. Ascorbic acid depletion was accompanied by a massive accumulation of cadmium in the liver. Similar changes were found in gill tissue. In contrast, ascorbic acid concentrations were largely unaffected in kidney tissue which had a limited capacity to accumulate the metal. There were marked fluctuations of ascorbic acid levels in the brain. Only small amounts of cadmium were accumulated by this tissue. These results indicate that in mullet liver, gill and brain ascorbic acid stores may be depleted during chronic cadmium poisonin

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03919.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A new gonostomatid species,Cyclothone parapallida, is described from the tropical Atlantic. Its affinities withC. pallidaare shown by the shared characters especially the presence of an enlarged caniniform tooth in the premaxilla and a posterior, irregular series of minute teeth on the pterygoid, but it is distinguished from this species by its lower gill raker count [21‐22 (23)v. 23–24 (22–25) first arch], its more restricted meningeal pigment, its lack of internasal pigment and its transparent dorsal and anal fin rays. Furthermore, it attains a larger maximum size, has a different geographic distribution pattern and, when sympatric, lives deeper thanC. pallida. A synopsis of characters useful in distinguishingCyclothonespp. in the Atlantic is pres

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03920.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The cytoplasm of the alarm substance cells in the epidermis of an ostariophysian fish, channel catfish, contained fine homogeneously dispersed fibrillar material. Most cyto‐plasmic organelles were concentrated perinuclearly. The mitochondria were of the tubular type and had matrix granules 30‐50 nm in diameter. The saccules of the Golgi bodies did not form a parallel array and were comparatively widely separated. The nucleus was irregular in shape and had a distinct nucleolus made up of deeply stained granules meshed with areas of less granulation. The nuclear envelope was in the form of a double membrane having a wavy appearance and occasionally it showed invaginations penetrating deeply into the nucleoplasm. Lysosomes and lipid inclusions were encountered in the vicinity of the nucleus. Proteins were demonstrated histochemically, but carbohydrates were not detected. Differences between the alarm substance cells of channel catfish and those of other ostariophysian fish were described and discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03921.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Supersaturation of surface water with atmospheric gases may result from hydroelectric or thermoelectric power generation and adversely affect aquatic biota. Although the phenomenon has been extensively studied in the northwestern United States, its occurrence is less well documented in Europe. We evaluated the tolerance of carp,Cyprinus carpio, and black bullhead,Ictalurus melas, from Italy to gas supersaturated water and compared our results to data reported in the literature for the same species from the Columbia River, U.S.A. Carp and black bullhead from Italy were more susceptible to gas supersaturation than those from the Columbia River. This may reflect greater adaptation of Columbia River fish due to their historical exposure to supersaturated water resulting from numerous hydroelectric dams.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03922.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY