摘要:

A new histozoic species of myxosporidian,Myxosoma microsporan.sp., infecting the gill filaments ofMugil cephalusis described. Cysts measuring 0.5–1.0 mm in diameter were found attached to the gill filaments. Spherical or slightly oval, spores 4.8–5.2 μm in diameter, were present and possessed a thin outer mucous envelope which appeared as small conical protuberances at the ends of the equatorial axis. Polar capsules were pyriform in shape, equal in size and measured 1.6–2.0 × 1.0–1.2 μm; the polar filaments were 22–28 μm in length. There was a bean‐shaped sporoplasm measuring 3.5 × 1.5 μm. No iodine vacuole was detected when the parasite was stained wi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03711.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

In freshwater‐acclimated rainbow trout a single intraperitoneal injection of ovine TSH significantly elevated plasma thyroxine (T4) levels within 1 h after the injection. In seawater adapted trout the increase in T4after TSH‐treatment was not evident until 6 h after the injection. TSH caused a transient fall in plasma Na+and Cl‐between 3 h and 9 h after the injection in seawater‐adapted fish and plasma Na+was lowered in freshwater‐adapted trout 24 h after the injection. Although there were clear histological changes in the thyroid gland of freshwater‐adapted trout after TSH‐injection, no such changes were evident in seawater‐adapted fish.Plasma thyroid hormone levels and thyroid histology in freshwater‐adapted rainbow trout and coho salmon transferred to sea water, and seawater‐adapted trout transferred to fresh water showed no consistent changes compared with controls.The data are interpreted to indicate that although ambient salinity may have indirect effects on thyroid activity there is no direct involvement in ionic or osmotic regulation

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03712.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Five years after inundation, two varieties ofCyprinus carpio—the common carp and the mirror carp, have appeared in the commercial fishery in Lake Kamburu. Species of Tilapia continue to remain the most abundant fish in the lake and their numbers are on the increase. The second most numerous species is Barbus whileLabeosp. seems to be declining. The numbers of Mormyrus have declined drastically. Species of the genera Tilapia, Barbus and Cyprinus are widely distributed within the lake; Labeo prefers the confluence of the rivers entering into the lake and Mormyrus has moved uprive

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03713.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abnormalities in the gonads of carp,Cyprinus carpioL., were present in a relatively high proportion of hybrids derived from the Chinese and European strains. The aberrations involved were the absence or marked reduction of the gonads in mature fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03714.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Mirogrex terrae‐sanctaeis a commercial, sardine‐like cyprinid fish in the Sea of Galilee. The fish spawns from December to the end of March. Females collected at the quiescent phase of the cycle (June) were exposed to four combinations of photoperiod and temperature for 3 months. The highest GSI (2.44 ± 0.22) was found in females exposed to simulated winter conditions (16°C, 9L) while the lowest GSI (0.65 ± 0.04) was found in fish exposed to simulated summer conditions (27°C, 14L). The GSI of fish maintained at the unnatural combination of 16°C, 14L (1.30 ± 0.09) did not differ from that of fish maintained at the other unnatural combination of 27°C, 9L (1.07 ± 0.11). However, histological examinations revealed that vitellogenic oocytes were present only in fish maintained at low temperature regimes, which implies that the growth of the ovarian mass in the 27°C, 9L group was due mainly to oogonial proliferation and that vitellogenesis was inhibited inMirogrexat a high temperature.Both protein and calcium concentrations increased in the serum of fish following injections of oestradiol‐17β. The increase of calcium was evident only in the non‐filtrable (bound) fraction, suggesting that the total serum calcium above 13 mg% could be used as an indirect parameter for circulating vitelloprotein.Fish collected at the quiescent phase were injected with oestradiol (50 μg/fish c. 15 g body weight) and subsequently transferred to tanks maintained at either 12°, 20° or 27°C. The total serum calcium increased to 23.0 ± 1.75 mg% in the fish maintained for 8 days at 20°C. This was significantly higher than the concentration of calcium in the serum of fish maintained at either 12°C (7.8 ± 0.52) or 27°C(l1.8 ± 0.77). This implies that the temperature may affect ovarian recrudescence by modulating the response of the liver to oestrogen, allowing the oestrogen‐induced vitellogenesis to be relatively high in the c

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03715.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Observations on haematological characteristics of albacore,Thunnus alalunga, and skipjackKatsuwonus pelamis, tunas, were made on blood samples collected from specimens immediately after they were caught and from an immobilized, restrained albacore sampled serially over a 24 h period. Results indicated eight types of blood cells in the peripheral circulation of both species. Lymphocytes were the most common leucocyte followed, in decreasing order, by neutrophils, eosinophils and monocytes in fish sampled immediately after being landed. Variations in differential and total white blood cell counts were observed in the immobilized, restrained albacore. High packed cell volumes and haemoglobin concentrations, typical for fast swimming fishes, were found in both species. Red blood cell counts were similar to those of other teleosts, and reticulocytes expressed as a percentage of mature erythrocytes were 6.1% and 5.2% for albacore and skipjack, respectively.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03716.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The general gonad morphology in the simultaneous hermaphrodite,Diplectrum bivittatumfrom the Gulf of Mexico, agrees with previously published accounts on the gonad morphology of otherDiplectrumspp. In D.bivittatumthere is a well developed accessory reproductive structure (ARS) which consists of a post‐ovarian sinus and numerous well developed villi which project into the sinus from the sinus wall. The ARS varies seasonally: the post‐ovarian sinus is reduced in February and enlarged during June, September and October when the species is reproductively active. The villi are better developed in September specimens. Two pillar‐like structures within the ARS are described for the first time. Their columnar and smooth muscle cell composition suggests several possible reproductive func

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03717.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Seven days after a 15% reduction in blood volume by bleeding, the haemoglobin system of rainbow trout showed a modification in relative abundance of two of the four haemoglobins present in the haemolyate. The least anodic non‐Root effect haemoglobin increased proportionally whereas the major component, with its Root effect properties, showed a decline. A total of 30 days of starvation did not influence the relative proportions of the fractions. However, bleeding of these starvedS. gairdneriprovoked a shift similar to that of fed trout. In this case, however, both non‐Root haemoglobins, and the minor Root fraction, increased proportionally. The major Root fraction declined. The response of the starved group was more acute since all four components were significantly affected in contrast to two fractions in fed anim

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03718.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

A study of eel catches from Lesina (444 specimens) and Varano lagoons (325 specimens), in southern Adriatic, Italy, was made. Male silver eels in Lesina ranged from 33.4–51.5 cm in length, with a mean of 42.6 cm; from 50–240 g in weight, with a mean of 141 g and were 1.5–6.5 years old with a mean of 2.5 years. The average length of male silver eels in Varano lagoon was 40.5 cm (range 31–48.5 cm); the average weight was 122 g (range 80–220 g)and a mean age of 2.6 years (range 1.5–7.5 years).The females are bigger, heavier and older than the males with, in Lesina, a mean length of 61 cm (range 50.9–74.3 cm), a mean weight of 438 g (range 240–730 g) and a mean age of 3.4 years (range 1.5–6.5). The average length of Varano female silver eels was 58 cm (range 50.8–72.5 cm), and the average weight was 383 g (range 225–840 g). They were 1.5–7.5 years old, with an average of 3.8 years. Female silver eels were only 20% of the population at Lesina and 10% at Varano.In comparison with the silver eel populations of the North Adriatic lagoons, the North Sea or the Atlantic Ocean, the silver eels of Lesina and Varano show a greater growth rate, are younger and have a sex ratio in favour of the males.The water temperature, higher than in other countries, could be an important factor affecting the differences in age and growth rates between Lesina and Varano silver eels an

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03719.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Forward motion was shown to increase the efficiency of suction feeding by causing the ingested volume to be predominantly in front of the fish, instead of being a sphere centred on the fish mouth. This increases the distance from which a prey, located in front of the predator, can be ingested by suction.A general hydrodynamic model of the external effects of the suction process is presented, showing that this is dependent upon a single non‐dimensional parameter, the ratio of a characteristic mouth dimension, divided by the forward swimming speed and the suction time. Data for large‐mouth bass,Micropterus salmoidesshow that the observed average forward velocity while feeding, of 3.1 body length/s, serves to increase the ingestion range by more than 60% over suction while not mov

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03720.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY