Age and growth of yellow eels, Anguilla anguilla, in the estuary of the Guadalquivir river (south-west Spain)

A total of 1068 eels were examined from a population located in the Guadalquivir river estuary (37°N, 6°25'W). Maximum ages recorded were 4 + (males) and 7+ (females), and maximum lengths were 39-1 cm (males) and 54.1 cm (females). No growth was recorded between November and April, most occurring in May and, to a lesser extent, in June-October. Females grew to be larger than males. A classification analysis, based on 17 different European eel populations revealed that populations in brackish waters grew faster than those in fresh waters, but latitude also had an influence. Length-weight relationships obtained for three eel categories (males, females and undifferentiated) were used to estimate relative condition: condition cycles were similar between sexes, with increases in autumn and decreases in winter. There were monthly fluctuations in the sex ratio, and females dominated significantly in the combined catch (234 males/276 females).     

Seasonal reproduction of a tropical bat, Anoura geoffroyi, in relation to photoperiod.

Anoura geoffroyi (Chiroptera, Phyllostomidae, Glossophaginae), Geoffroy's hairy-legged long-tongued bat, were collected from September 1984 to August 1985, and these bats were found to breed seasonally in the wild on Trinidad, West Indies, at 10 degrees N latitude. Histological examination of these samples indicated that females became pregnant in July or August, and young were born in late November or early December. The testes and epididymides were small from September to mid-April, increased threefold in weight between mid-April and late May, reached a peak weight in July, and decreased in weight in August. Spermatogenesis occurred throughout the testes of males captured from May to August. In 1990, the timing of parturition in females that gave birth in the laboratory to young conceived in the wild was similar to the timing in the field in 1984-1985. Groups of 10-13 males were subjected in the laboratory to (i) a gradually changing, civil twilight photoperiod that mimicked the natural cycle of annual change at 10 degrees N latitude, (ii) the same gradually changing cycle of photoperiod accelerated to a six-month period, or (iii) a constant photoperiod (light 12:54 h: dark 11:06 h). These treatments began in mid-December, four months before the initiation of testicular recrudescence in the wild. In all three groups, testicular volume remained low until April, and then increased two- to threefold between late April and late June, rising to a peak in July, as occurred in the wild.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characteristics of the spawning migrations of brown trout, Salmo trutta L., and rainbow trout, S. gairdneri Richardson, in Great Lake, Tasmania

Upstream spawning migrations of mature brown trout, S. trutta , and rainbow trout, S. gairdneri , were studied in Liawenee Canal, Great Lake from 1949 to 1985. Brown trout migrations normally occurred from early April to mid-May and rainbow trout from late August to early November. In 1983, 16 425 brown trout and 1338 rainbow trout passed through a fixed upstream diversion trap. Brown trout spawning migrations occurred predominantly over the temperature range 6–10° C, while rainbow trout migrated predominantly over the range 5–11° C. Migrations peaked at water temperatures of 7.6°C (males) and 7.8°C (females) for brown trout, and 8.3°C (males) and 9.6°C (females) for rainbow trout. Rainbow trout migrations occurred at high flow conditions and were positively correlated with canal flow increases, while brown trout migrated under low canal flow. Mean length, weight and condition of rainbow trout of both sexes decreased significantly during migrations. Female brown trout decreased in weight and condition but not in length; male brown trout did not change in condition despite decreases in both length and weight during migrations. Overall sex ratio was 2:1 (female:male) for both species, with the relative proportion of male fish decreasing as migrations progressed. Age composition changed during migrations; dominant age classes were 3 < 4 < 5 + years for both species. Comparison of length, weight, condition and age revealed minor changes during the 37-year period 1949–1985.     

Morphological and reproductive characteristics of musk shrews (Suncus murinus) collected in Bangladesh, and development of the laboratory line (BAN line) derived from them

To establish a unique laboratory line of the musk shrew with different genetic properties from previously developed laboratory lines, 49 male and 49 female shrews were captured in the campus of Bangladesh Agricultural University from October through November in 1983 and from December in 1985 to January in 1986. The shrews collected were of various ages. They had light gray coats, with slight variations in color. Except for the 12 shrews introduced into our laboratory, the total length and body weight of the shrews ranged from 17.2 to 31.9 cm and 32.5 to 147.0 g in males, and 21.1 to 26.6 cm and 40.8 to 110.0 g in females, respectively. Pregnant females were found throughout the trapping period, and the average fetal litter size was 3.54 (11 cases). Five males and 7 females of the shrews captured in 1983 were transported to our laboratory. After more than 100 days of laboratory rearing, their total length and body weight averaged 27.6 cm and 147.3 g in males, and 24.6 cm and 81.7 g in females. Their body weight was more than double that of Japanese shrews. The shrews introduced (except for one male) produced a total of 59 offspring, which were regarded as the first generation of the laboratory line (BAN Line). Gestation period and average litter size were between 28 and 30 days (10 cases) and 3.47 (17 cases), respectively. The BAN line has consisted of about 60 individuals at each generation and has been maintained as a closed breeding colony.     

Life history and distribution of the small south-western Atlantic octopus, Octopus tehuelchus

Although this species has been reported from shallow waters down to 90 m depth, knowledge is almost entirely based on intertidal samples. In this study both intertidal and subtidal samples were taken during 1982–1987, in northern San Matias Gulf (41° S, 63° 30' W). This is a large-egged (eggs: 9–12 mm long ×–5 mm wide, stack of 4–6 mm long) and small-sized (up to 150 g) octopus. Egg laying occurs between autumn and winter. Embryonic development takes about four months (water temperature:–19°C). Large hatchlings (DML: 5·64 mm, TL: 14·23 mm, TW: 0·139 g) emerge over spring and early summer, and development is direct. Maximum size is reached after 17–18 months; mating takes place in summer. Females reduce their feeding activity when they reach maturity, and cease eating while brooding. Mean life-span is two years, but some individuals (mostly females) may live up to three years. Females approaching the beginning of the brooding period move to the subtidal zone, where males outnumber females until the end of summer and females (mostly brooders) then outnumber males. In the intertidal zone sex ratio was 1:1 from December to late March, but in April males outnumber females.
These life-history traits are compared with those of other large-egged octopuses and are discussed in relation to environmental conditions prevailing in the San Matias Gulf.     

池塘中斑索蟾的种群结构、个体生长与存活率

在澳大利亚新南威尔士南部沿海,作者搜集了一个池塘繁殖的斑索蟾(Crinia signifera)的种群统计资料。通过捕捉进出池塘的1 612只个体,获得种群大小、结构、生长率、性成熟时的大小和年龄、死亡率及寿命资料。迁移高峰从6月持续到11月,蛙的最高、最低遇见数量分别出现在春季和秋季。但第2年,该池塘蛙的数量明显减少,可能是由于补充到种群中的幼体数量很少的缘故。6个月后个体的重捕率很低;但距第一次捕获18个月以后,仍有个别个体再次被捕获。性成熟时,雌性比雄性的身体大一些。生长曲线显示,雌性比雄性的生长更快,所以更早地达到性成熟。研究种群的数量、结构和死亡率趋势等与已知的其它Crinia signifera种群基本一致。但研究种群迁移活动的高峰出现较晚,并且夏季的活动水平明显很高。这种长的活动时间可能会导致存活率的下降,同时有利于选择迅速性成熟的雌性[动物学报51 (3) : 393 -400 , 2005]。     

Reproduction of the long-tongued nectar bat Macroglossus minimus (Pteropodidae) in Brunei, Borneo

The long‐tongued nectar bat Macroglossus minimus lagochilus (Megachiroptera, Pteropodidae) is a small fruit bat inhabiting South‐east Asia. Its reproduction was studied in Brunei, Borneo, where individuals were usually captured in rainforest (Ulu Temburong). Adult females (n = 23) had body masses of 13.0–19.0 g, with forelimbs 3.83–4.33 cm in length. All adult females were pregnant, with pregnancies observed during every month except May, September and November when no adult females were captured. Female M. minimus in Brunei have a reproductive cycle that is consistent with a pattern of seasonal bimodal polyoestry. Most births appear to occur from November to May, during which time females experience two births: the first centred around November and December, and the second centred around April and May. These two birth seasons appear correlated to the two seasons of greater rainfall in Brunei: October to December, and April to July. Oestrous and mating apparently occur soon after each birth; however, there appears to be a 2‐ to 3‐month period of delayed embryonic development following the births centred around April and May. The data are consistent with embryonic development commencing around July and August (after a delay) for the births centred around November and December, and around December and January for the births centred around April and May. The data suggest that all adult females participate in each breeding season. Adult males (n = 20) had body masses of 12.5–18.0 g, with forelimbs 3.91–4.26 cm in length.     

Embryonic duration and post-embryonic growth rates of the tropical freshwater shrimp Caridina nilotica (Decapoda:Atyidae) under laboratory and experimental field conditions

SUMMARY. Embryonic durations and post embryonic growth rates of Caridina nilotica were determined under laboratory conditions at constant temperatures near 18, 24 and 30°C. Embryonic durations and intermoult intervals were negative curvilinear functions of temperature. At a given temperature moulting frequency varied inversely with shrimp size and slight sexual differences were apparent. Moulting frequency of berried females was governed by the temperature-specific embryonic durations. Growth rates were determined from changes in carapace length (CL) of individual shrimps (laboratory) or batches of shrimps (field enclosures) over 1 month and these data were used to calculate temperature-specific life-long growth curves for males and females. Growth in body mass was estimated indirectly from the carapace length-mass relationship of C. nilotica. On average, males grew marginally faster than females during the first 2 months of life, but growth of males larger than CL= 4 mm was considerably depressed relative to that of females. Inflexions in growth rate, apparently related to the onset of sexual maturity, were apparent in both sexes. Under laboratory conditions, the growth rate of males increased with temperature, but temperature-related differences were not as marked in females. Notwithstanding the more rapid moulting rate at 30°C the growth rate of females was slightly slower at 30 than at 24°C as a result of marginally but significantly smaller per moult growth increments observed at 30°C in animals up to CL= 5.5 mm. Possible reasons for this depressed growth are discussed. Growth rates of animals in field enclosures in Lake Sibaya over 1 month in winter (20 ± 3°C) were generally comparable to those estimated for the 18°C laboratory experiments. Growth rates in enclosures containing tripled standing stocks were almost identical to those containing the naturally occurring biomass of animals, suggesting a non-limited environment at least during the time of the experiment.     

Size-related and seasonal patterns of egg collar production in Polinices pulchellus (Gastropoda: Naticidae) Risso 1826

Polinices pulchellus held in the laboratory produced egg collars all year round. Egg collar production was greatest during July and August and only occurred in females >8-10 mm shell length. The largest individuals (14-16 mm shell length) had the highest fecundity and ceased egg-laying in late September, whilst 8-14 mm individuals laid egg collars until November. Small females (4-6 mm) grew rapidly during the warmer, summer months (April to August), became sexually mature and began laying egg collars in mid-September. Both the range of egg collar wet weights and the maximum wet weight of an individual egg collar increased with female size class. Temperature strongly affected the length of time between the laying of egg collars and the hatching of larvae (9-10 days at 19-20 °C and 14-15 days at 13-14 °C). A close relationship was also found between egg collar wet weight and the number of veliger larvae released.     

Observations on the biology of the perch, Perca fluviatilis, in the River Stour, Dorset

SUMMARY. Opercular bones from 323 perch from the River Stour were used for age and back-calculated growth determinations. Annuli were formed during May at the beginning of the growth period. Growth was minimal from October to April. Female perch grew faster than males, and the growth rates of both sexes were higher than those observed in most other European waters. Spawning occurred during late April and early May; male gonads began development in August and had attained their maximum weight in September, but the ovaries developed gradually from August until April. Immature perch had an annual cycle of condition with a maximum in June-July and a minimum in December-January. The condition of mature males and females was affected by the gonad cycle. The fecundity of Stour perch is expressed by the formula: log egg number = 2.40 log length (mm) - 1.34.
Approximately 25% of males were mature at age I and all were mature at age II, whereas most females did not spawn until age III. Ephemeroptera nymphs and minnow fry constituted the bulk of the diet of 0-group perch; Ephemeroptera nymphs, minnow fry and Corixidae were the most numerous items in I group perch, whereas older perch contained Corixidae and a wider range of fish prey species, although minnows were the most numerous of these.     

Biological Aspects of Medorippe lanata (Linnaeus, 1767) (Brachyura: Dorippidae) from the Eastern Ligurian Sea (Western Mediterranean)

The aim of the present study is to investigate the demographic structure and to identify some aspects of the biology of an exploited population of Medorippe lanata (Brachyura: Dorippidae) in the eastern Ligurian Sea, western Mediterranean. 1364 specimens (639 males and 725 females) of M. lanata were collected on a monthly basis from January to December 2001, in a wide area of the eastern Ligurian Sea usually exploited by the Viareggio ‘rapido’ trawl fleet. M. lanata represented an important fraction of the discard, both in weight and in number of individuals. Maximum abundance of this species occurred in late summer-early autumn (up to 3369 ind. km⁻² and 50.6 kg km⁻² in August). The overall females:males sex-ratio was 1.13:1, while the monthly sex-ratio did not differ statistically from 1:1 in all months, except in September and October, when females significantly outnumbered males. The sampled population was composed of two cohorts from November to April. Sizes ranged from 10 to 29 mm carapace length (CL) for females and from 9 to 29 mm CL for males. The von Bertalanffy growth curve, computed for both sexes, gave a higher growth rate in males than in females. Recently moulted males and females were observed throughout the year, except in summer, when the highest number of ovigerous females was present. Females with external eggs were collected from March to November, with peaks in August and September. The monthly evolution of the ovarian maturity stages showed no clear temporal trend. At 21 mm CL, 50% of females were ovigerous or showed macroscopically mature ovaries. According to the dimorphism in chelae size, the presence of adult males (post-puberty stage) was observed all year round, from 18 to 29 mm CL, without evident temporal trends.     

The growth rates of the estuarine mollusc Musculista arcuatula Yamamoto and Habe (Bivalvia: Mytilidae)

The pattern of growth of the total population of Musculista arcuatula over a period of thirteen months was built up plotting length-percentage frequency histograms each month. From the shifting of the modes it was noticed that the increase in size from November to December was 2 mm, the growth during December to January 3 mm. In February the growth was nil. In March the size increasing by 6 mm and in April by 1 mm, when mortality of the largest size groups started to get completed in May. In June a conspicuous mode appeared at 9 mm, grew 1 mm in July, 2 mm in August and 3 mm in September. Growth remained stationary in October and November. The rate of increase in length was found to follow exponential law. The growth rate of this bivalve goes on increasing at a steady pace, the rate being 1.086 mm per month. The mean size of the females was found to be significantly larger than that of the males. The proportion of the males in the size group 3 mm to 10 mm was found to be significantly larger than in the entire population. But in the larger size groups there was no difference in the number of males and females and the proportion was almost 1:1. Throughout the year only one age class was recognizable in the natural population. There appears to be an excessive post reproductive mortality of adults rendering the population during most of the year of a single age class recruited through the various months of spawning. The maximum longevity was found to be at the most 18 months.     

Reproduction and growth of the black shore skink,Leiolopisma suteri (Lacertilia: Scincidae), in north‐eastern New Zealand

Reproduction and growth of a boulder beach population of the nocturnal skink Leiolopisma suteri on Motutapu Island were studied for 19 months. Epididymes contain sperm from April to November, and copulation probably occurs in October or November (spring). Ovulation occurs in late October or early November, and three or four (mean, 3.7) eggs are laid in late December. Incubation takes 3 months. Total development time from ovulation to hatching is 5 months, one of the longest development periods recorded for Scincidae. Growth to sexual maturity is slow, most females depositing their first clutch 33 months after hatching; males mature at 29 months.     

Physiology of diapause and cold hardiness in overwintering pupae of the apple leaf miner Phyllonorycter ringoniella in Japan

Abstract The apple leaf miner Phyllonorycter ringoniella (Matsumura) (Lepidoptera: Gracillariidae) overwinters as a diapausing pupa. The diapause rate reaches 100% in early October. Diapause intensity decreases gradually from early October and diapause terminates in early February. The fresh body weight of diapausing pupae is 1.6 times that of non-diapausing pupae. The main cryoprotectant in P. ringoniella pupae is trehalose. Three stages are distinguishable as indicated by the correlations between diapause intensity, levels of cold hardiness and the trehalose content: diapause induction occurred in October, diapause development from November to December, and post-diapause quiescence from January to April. During diapause induction, the pupae accumulate low levels of trehalose and do not survive exposure to −15 °C. During diapause development, the pupae gradually accumulate more trehalose and show some ability to survive exposure to −15 °C, but not to −20 °C. During post-diapause quiescence, the pupae accumulate relatively more trehalose and cold hardiness fully develops, but decreases quickly in April. The trehalose content in pupae sampled in December is unaffected by acclimation temperatures in the range 0–30 °C, but decreases in pupae sampled in March after acclimation at temperatures from 5 to 15 °C. These results suggest that overwintering pupae of P. ringoniella have the ability to accumulate trehalose and develop a high level of cold hardiness during diapause development.     

Seasonal changes in condition, reproduction and fecundity in the wild European rabbit (Oryctolagus cuniculus)

A total of 1248 rabbits ( Oryctolagus amiculus ) were shot on farmland in Cambridgeshire, UK over a period of three years. This provided pooled estimates of changes in reproductive and body condition and of fecundity during the annual cycle. Both males and females showed a significant annual cycle in reproductive condition as indicated by changes in the size of the gonads and accessory glands of reproduction. No females were pregnant during October, November and December, but males with active spermatogenesis were found during every month of the year. The distribution of pregnancies through the year showed that the reproductive season varied greatly between individuals. Peak fecundity occurred during April, May and June. On average, each female conceived 23.9 and suckled 17.2 young per breeding season. Proportionately more young died during the early stages of the reproductive season. The body weight of adult males, but not of females, varied seasonally. Body condition (kidney fat index) in adults was maximal at the start of the breeding season and minimal at the end.     

Reproductive activity in the commercially exploited mediterranean muricid <Emphasis Type="Italic">Hexaplex trunculus</Emphasis> collected from Boughrara lagoon (Southern Tunisia)

The banded murex Hexaplex trunculus (Linnaeus, 1758) is a commercially exploited gastropod in the Mediterranean region including Tunisia where it has become an important fishery resource these last years. In the present investigation, some reproductive aspects of this species were described in the population of Boughrara lagoon based on macroscopic examination of the gonads (gonadic conditional indices) together with observation of the seasonal hypertrophy of the penis in males and capsule gland in females. This procedure of assessing reproductive activity was validated by field observations of copulation and spawning. Mature females were found during 10 months and mature males during 8 months being both frequent in January and February. Reproductive activity was slightly asynchronous between sexes with males reaching maturity before females. Gonadic release occurred earlier in males between January and March against February to April in females. These findings were in agreement with field observations of copulation in January and February and egg-capsule laying in late February and March. Hatching juveniles were observed in the field in April and May.     

Hibernation in the mountain pygmy possum Burramys parvus (Marsupialia)

Mountain pygmy possums Burramys parvus (40 g) disappear from their Mt. Kosciusko boulder fields from May to October/November and it is assumed that they hibernate during this time. However, laboratory studies did not observe the characteristic hibernation pattern of placentals, which, throughout the hibernation season, show long bouts of torpor (several days to weeks) that are interrupted by short (< 1 day) normothermic periods. We investigated the pattern of hibernation in juvenile (N = 8) and adult (N = 8) male and female B. parvus in the laboratory at an air temperature that was similar to that in the field during winter. Adults commenced hibernation earlier and hibernated longer (about seven months) than juveniles (about five months). All adult individuals hibernated whereas only six of the eight juveniles did so. Hibernating animals showed distinct seasonal changes in the duration of torpor bouts. Torpor bouts were short (about five days) at the beginning, long (12–20 days) during the middle, and short again at the end of the hibernation season. Normothermic periods were usually shorter than one day. The pattern of the seasonal change of torpor bout duration differed between juveniles and adults and between sexes. Body temperature during mid-hibernation was regulated at about 2 ° c in females and 3 ° C in males and the metabolic rate was similar to that of hibernating placentals.     

Development of pea bacterial blight caused by Pseudomonas syringae pv. pisi in winter and spring cultivars of combining peas (Pisum sativum) with different sowing dates

Pea bacterial blight occurred by natural infection in a field trial on peas in 1995. Disease development in the winter cultivars Rafale, Frilene and Froidure was compared with that in the spring cultivars Baccara, Conquest and Bohatyr, each sown on six dates in October, November, December, mid-March, late March and April. Disease incidence had reached 100% plants affected in all treatments by mid-July. Disease severity was greater in winter-sown (October, November or December) than in spring-sown peas of each cultivar at each assessment. Significant (P < 0.05) differences in disease severity occurred between cultivars in the winter-sown plots in May and June and the spring cultivars were affected more severely than the winter cultivars. Comparison of areas under the disease progress curves for both disease incidence and severity also showed that the winter-sown peas were more affected by disease than spring-sown peas and that spring cultivars were more severely affected than winter cultivars. Yield was strongly correlated with disease severity. A linear regression model suggested that, for peas sown in October, November or December, a yield loss of 0.5 tha^-1 occurred for each 10% increase in canopy area affected by pea bacterial blight.     

Compensatory sea growth of male Atlantic salmon, Salmo salar L., which previously mature as parr

The proportion of mature male parr in 11 families of Atlantic salmon, Sulrno sulur, reared under similar conditions in fresh water varied from 0–43%. The mature males were smaller than their siblings in December as 1 + and in late March. After individual tagging and transfer to a sea cage in early April. the previously mature males grew faster than previously immature salmon during the next 6 months. This compensatory growth resulted in almost equal size between the two groups. The results are discussed in relation to the different life strategies of salmon.     

Observations on the age, growth, reproduction and food of the dace, Leuciscus leuciscus (L.), in two rivers in southern England

Scales of 497 dace from the river Stour and 573 from the river Frome were used for age determinations. Annuli were laid down in late May to early June at the start of the growth period. Minimal growth occurred from November to April. Male dace grew minimally faster than females; Frome dace faster than those from the Stour. Growth rates in the two rivers were similar to those published for most other European waters. Variation in growth rates in different years was not great, but there were marked differences in recruitment success. Spawning occurred in the second half of March and elaboration of the gonads between September and March. Immature dace have an annual cycle in condition with a maximum in June and a minimum during the winter months. The condition of the mature females is affected by the gonad cycle. The fecundity of Stour dace is represented by the formula:

and for Frome dace by:

Most dace were mature by age IV, but there were more mature II and III group fish in the Frome population. Molluscs and Trichoptera larvae comprised the bulk of the winter diet of Stour dace, and Ephemeroptera nymphs, Simulium and chironomid larvae were the principal constituents during the summer.