The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet-and-Dry Climatic Zone: I. Physical and Chemical Causes and Biological Effects in the Pantanal of Mato Grosso,Brazil

The tropical wet-and-dry climatic zone is characterized by aquatic environments that cover extensive areas during part of the year and shrink to small standing water bodies or rivers with minimal water levels during the dry seasons. Even in the small permanent water bodies, the conditions fluctuate radically during each annual cycle. While there are often strong currents in the water courses during the high water periods, most aquatic habitats are strictly lentic during the dry seasons. Studies conducted in the Pantanal of Mato Grosso, one of the largest wetlands of the world, revealed major features of changes in physical and chemical parameters during the annual cycle. The general features of the climate include a hot, rainy period usually lasting from late October through late April, a cool, dry period from late April through late August, and a hot, dry period from late August through late October. Considerable year to year variations are encountered in the dates of onset and end of the various seasons, however. Four annual periods are recognized according to the water level in the Pantanal. Generally, the concentrations of dissolved inorganic substances are very low and stable during the high water period and variable and usually high in the remaining standing water bodies when much of the region has dried out. The amount of mineral nutrients increases as the water level rises during the early rainy season but decreases again as the aquatic macrophyte populations develop. Some of the reasons for the many short-term changes in mineral nutrient concentrations and the roles of the various aquatic communities are discussed. The results presented will serve as a basis for subsequent studies on the seasonal succession of the flora and fauna.     

Characterization of riparian species and stream detritus using multiple stable isotopes

Multiple stable isotopes were used to determine the effectiveness of distinguishing among several dominant riparian species and aquatic macrophytes both spatially (three sites) and temporally (three seasons) along an 8-km reach of a blackwater stream. The differences in isotopic composition were used to assess contributions of various organic matter sources to the detrital pool of the stream. Samples of riparian and aquatic macrophyte vegetation and detritus were collected at three times to represent early leaf-out (April), mid-summer (August), and just prior to abscission (October). Each sample was analyzed for stable isotopes of carbon ¹³C, nitrogen ¹⁵N, and sulfur ³⁴S Within a site and sampling date, ¹³C-values were significantly different among certain riparian species and detritus samples. Species differences persisted between seasons. ³⁴S values were the most variable of the three elements examined although they remained fairly constant through time within each species and site. The results suggest that temporal changes in isotopic compositions of riparian species and aquatic macrophytes are site-specific. Discriminant analysis dissimilarity plots (based on all three isotopes) demonstrated that the contribution of species to the detrital pool depended on the site and season. At the upper site, detritus was isotopically most similar to Quercus laurifolia and Sparganium americanum in April, and the aquatic macrophytes (S. americanum and Potamogeton spp.) in August and October. At the middle site, detritus was most similar to Carpinus caroliniana and Q. nigra in April but no single source was similar to detritus in August or October. At the lower site, detritus was most similar to Taxodium distichum for all three seasons.     

Long-term seasonal variation in the biological traits of benthic-macroinvertebrates in two Mediterranean-climate streams in California, U.S.A.

1. We investigated the seasonal variation of biological traits and the influence of interannual rainfall variability on this pattern. Using long‐term survey data (6–19 years) from an intermittent and a perennial stream in the Mediterranean‐climate region of northern California, we examined 16 fuzzy‐coded biological traits (e.g. maximum size, life cycle duration, and mode of respiration). 2. Seasonal habitat variability is higher in the intermittent stream than in the perennial stream. During the winter and spring wet‐season both streams flood; however, during the summer dry‐season, the intermittent stream forms isolated pools in (occasionally drying completely). 3. Seasonal habitat variability influenced both taxonomic and biological trait composition. Distinct taxonomic communities were present in each season, particularly in the intermittent stream. The intermittent stream also exhibited more seasonal variation in biological traits than the perennial stream. 4. Despite statistically significant seasonal variation, trait composition was relatively stable among seasons in comparison with taxonomic composition and abundance. Taxonomic composition varied considerably between seasons, because of high seasonal and interannual replacement of taxa resulting from seasonal habitat changes. 5. The seasonality of taxonomic composition and abundance was sensitive to interannual rainfall variability. In dry years, the taxonomic composition of communities was more similar between seasons than in wet years, while trait composition was relatively insensitive to rainfall variability. 6. Despite high seasonal variation in abundance and taxonomic composition, biological traits of aquatic macroinvertebrates varied less and exhibited seasonal stability, which may be a result of the unpredictability and harshness of stream environments.     

Seasonal flow variation allows 'time-sharing' by disparate aquatic insect communities in montane desert streams

1. Flow variation can drive major abiotic changes in stream environments between seasons. Theoretically, disparate biotic communities could be maintained during different seasons at a single site if suitable refuges and colonist sources were available. Using isolated montane desert streams in south‐east Arizona as a model system, we hypothesised that two disparate aquatic insect faunas (montane temperate and neotropical) could be maintained at the same sites through strong seasonal variation in abiotic conditions. 2. We collected aquatic insects representing 59 families from seven streams during high‐flow (March–April) and low‐flow (June) sampling periods across two years. We assessed changes in aquatic insect community and functional feeding group composition by habitat (riffle, pool) and season (high flow, low flow). 3. Within sites, wetted stream area decreased by an average of 97% between high‐flow (predominately riffles) and low‐flow (predominately pools) seasons. Community composition likewise showed strong seasonal patterns; the montane temperate fauna was strongly associated with the high‐flow season while neotropical hemipterans and coleopterans were associated with the low‐flow season. Increased water temperature was significantly associated with this shift from temperate to neotropical assemblages. 4. Functional feeding group composition shifted dramatically by season. The proportion of predators increased from 24.5% (high flow) to 75.2% (low flow) while collector–filterers and shredders declined from 38.4% (high flow) to 1.7% (low flow). 5. We suggest that habitat ‘time‐sharing’ by disparate communities is facilitated via strong seasonal variation in temperature and flow and the presence of high elevation refuges or diapause stages for temperate montane taxa to survive the dry season.     

中华秋沙鸭繁殖习性初报

2005年和2006年的4～5月在黑龙江省伊春市带岭碧水自然保护区对中华秋沙鸭(Mergussquamatus)的繁殖习性进行了初步研究,采用直接观察法观测了4个鸭巢.记录了巢的特征值、巢周围的环境因子以及中华秋沙鸭繁殖期的活动情况.结果表明,中华秋沙鸭每年的3月下旬至4月上旬陆续到达永翠河流域,9月末至10月下旬陆续迁离,居留时间210 d左右.其对栖息环境要求较高,行为方式独特,营巢树种皆为老龄榆树(Ulmus propinqua)或杨树(Populus ussuriensis),一般距河流和道路较近,两巢相距最近距离大于1.6 km.最大距离10 km,各巢洞口方向视野皆很开阔,巢址附近的植被相对稀疏.孵化期雌鸭用于孵化的时间占85.3%,取食仅占14.7%,雄鸭不参与孵化和育雏,用于觅食和取食的时间占24.4%.     

Desmids from Southern Bays of the Donghu Lake,Wuhan, China

A total of 48 algae samples were collected from southern bays of the Donghu Lake from September in 1963 to December in 1964．The desmids were very plentiful,164 species,75 varieties and 13 forms belonging to 20 genera were identified．Among these,two species,seven varieties and two forms are new to science**,and 12 species,25 varieties and five forms are recorded for the first time in China．The dominant species with frequent occurrence were 11 species and one variety in four seasons． The result of counting and analysing the samples collected in different seasons (six times for each) shows that the number of the taxa of Desmids in summer (June and August)was the highest,that in autumn and winter (September,October and December) the next,and that in spring (April) is the lowest．Fourty five of 252 desmids taxa are tropical and subtropical,among which 19 are either endemic to or common in S and SE Asia． The desmid flora of Wuhan district is therefore subtropical in nature and closely related to the S and     

武汉东湖南部湖汊的鼓藻类

从1963年9月到1964年12月,作者在武汉东湖南部的湖汊定点采得48号藻类标本,其鼓藻类十分丰富,经鉴定共有20个属,164个种,75个变种和13个变型。其中有2个新种、7个新变种和2个新变型,12个种、25个变种和5个变型是中国的新记录;在四季中出现频率较高的优势种类有11个种和1个变种。在不同季节共6次所采得的鼓藻种类的统计结果得出,在夏季(6月、8月)的种类最多,秋季和冬季(9月、10月、12月)次之,春季(4月)最少。在东湖252个鼓藻类的分类单位中,热带、亚热带类群共有45个,其中的19个是南亚和东南亚地区特有或普遍分布的类群,13个是以广西为模式产地的类群,从而反映武汉地区鼓藻类区系具有亚热带类型的特点,并与南亚和东南亚的鼓藻类区系关系密切。     

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.     

Influence of seasonal variation on bioassessment of streams using macroinvertebrates

The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates. One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores obtained from macroinvertebrate indices vary naturally between seasons, confounding the detection of anthropogenic environmental change. We investigated this problem in a 4th order calcareous stream in the western Carpathian Mountains of central Europe, the Stupavsky potok brook. We divided our 100 m study site into two stretches and took two replicate samples every other month alternately from each stretch for a period of 1 year, sampling in the months of February, April, June, August, October and December. Multivariate analysis of the macroinvertebrate communities (PCA) clearly separated the samples into three groups: (1) April samples (2) June and August samples (3) October, December and February samples. Metric scores were classified into two groups those that were stable with respect to sampling month, and those that varied. Of the metrics whose values increase with amount of allochthonous organic material (ALPHA_MESO, hyporhithral, littoral, PASF, GSI new, DSI, CSI), the highest scores occurred in February, April, October and December, while for metrics whose values decrease with content of organic material (DSII, DIS, GFI D05, PORI, RETI, hypocrenal, metarhithral, RP, AKA, LITHAL, SHRED, HAI) the highest values occurred in February, April, June and December. We conclude that sampling twice a year, in early spring and late autumn, is appropriate for this type of metarhithral mountain stream. Sampling in summer is less reliable due to strong seasonal influences on many of the metrics examined while sampling in winter is inappropriate for logistical reasons. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

山地河流潜流层大型无脊椎动物群落组成及分布

潜流层大型无脊椎动物是河流生态系统重要的组成部分.2013年8月(夏季)、12月(冬季)和2014年4月(春季),在黑水滩河上游河段,采用人工基质法调查潜流层大型无脊椎动物.结果表明: 3个季节共采集大型无脊椎动物27种,其中夏季22种、冬季和春季各16种,各季节水生昆虫种类所占比例均较高,分别为81.8%、75.0%和62.5%;夏季群落密度显著低于冬季和春季,春季最高;冬季群落生物量显著高于夏季和春季,夏季最低;3个季节群落的物种丰富度指数、Shannon多样性指数和Pielou均匀度指数均没有显著性差异.空间分布上,大型无脊椎动物的密度和丰富度均随潜流层深度增加而呈现降低的趋势,大多数个体均分布在0～20 cm深度.群落以滤食者和收集者组成的集食者为绝对优势功能群.动物的相互作用、生活史策略和潜流层的理化条件影响着潜流层大型无脊椎动物的群落结构和时空分布.     

Zooplankton Communities in the Shallow Lake Guiers (Senegal,West Africa)

Seasonal variations of zooplankton communities and their interactions with phytoplankton and environmental parameters were studied over a twelve‐month period in Lake Guiers (Senegal, West Africa). Zooplankton was most abundant during the warm and rainy season corresponding to the flood event (July to October) with peaks for rotifers and cyclopoid copepods in July–August and September–October, respectively. Filamentous cyanobacteria were the dominant phytoplankton during the warm season (August to November), while diatoms were dominant during the cool season (December to April). Temperature increase and river flooding both played an important role in these successions, favoring intense development of cyanobacteria and cyclopoid copepods. Trophic interactions also seem to be an important factor in structuring of the plankton community. Overall, the plankton composition displayed a trend toward a eutrophication state. Our study confirms the existence of seasonality in zooplankton communities and the importance of using biological indicators such as phyto‐ and zooplankton to monitor water quality, in particular in tropical freshwater ecosystems. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spatial and temporal patterns of invertebrate drift in streams draining a Neotropical landscape

1. Invertebrate drift in streams draining a tropical landscape in Costa Rica was studied to assess differences in assemblage composition above and below a major gradient break in geomorphic landform and to assess temporal patterns of drift in lowland reaches below the gradient break. The gradient break (～50 m a.s.l.) is the point at which the foothills of the Costa Rican Cordillera Central (piedmont) merge with the Caribbean coastal plain (lowlands).
2. Spatial patterns were assessed along two streams by sampling drift over 24 h once a month for 3 months in both the piedmont (90 m a.s.l.) and lowlands (30 m a.s.l.). Temporal patterns of drift were assessed through monthly diel sampling of three lowland sites over 8–10 months, encompassing both ‘dry’ (<400 mm precipitation per month, November to May) and wet (July to October) seasons.
3. Drift composition was insect dominated in piedmont sites and larval shrimp dominated in the lowlands. Percent similarity of assemblages between piedmont and lowland sites was low (range 26–43%) because of high larval shrimp densities in lowland versus piedmont sites.
4. Drift densities were higher during night than day, with peaks at sunset on all dates and at all sites. Diel patterns in drift agree with previous observations for the study area and support the ‘risk of predation’ hypothesis.
5. Analysis of monthly patterns in lowland sites showed high variability in drift densities; however, all major taxa were found every month. Overall, there was a trend for high invertebrate densities during the ‘dry’ season, but these trends were not significant.
6. Observed changes in drift composition support the concept of river zonation, which predicts a change in community composition along the stream continuum due to geomorphic features. Drift at lowland sites below the gradient break was dominated by shrimps, which are linked to marine environments via their migratory behaviour.     

Effect of Temperature Variations on Vermicomposting of Household Solid Waste and Fecundity of Eisenia fetida

Experiments were conducted in winter (October to January) and summer (May to August) seasons to study the effect of seasonal temperature variations on the vermicomposting of household waste using Eisenia fetida earthworms. The prevailing temperatures during experiments were in the range of ?2.7°C to 35.0°C during winter season and 18.0°C to 44.4°C during summer season. Organic matter degradation was higher during winter than summer season. The electrical conductivity (EC) of vermicomposts was increased in the range of 2.3–7.8% in winter season; however, the increase in EC was 0.9–1.8% during summer season for different waste mixtures. There was about 56.2–80% increase in total Kjeldahl nitrogen (TKN) content during winter season, whereas the TKN increase was 23.9–44% during summers. The C:N ratio also decreased remarkably in all the waste mixtures during vermicomposting in both the seasons. However, the C:N ratio reduction was more significant during winter (47–60%) than in summer (31–44%). After the observation period, the net worm biomass achieved was higher during winter than summer season. The temperature variations during winter supported the life activities of earthworms more favourably than in summer. The results indicated that growth and reproductive potential of the earthworms were affected not only by the quality and quantity of the feed but also by ambient temperature.     

THE WINTERING AND MOULT OF RUFFS PHILOMACHUS PUGNAX IN THE KENYAN RIFT VALLEY

Some 5700 Ruffs were ringed in the southern Kenyan rift valley during 1967–79, mainly at Lakes Nakuru and Magadi. These have produced 15 recoveries outside East Africa, 14 in Siberia between 73° and 154°E and one in India. Adult males returned to Kenya mainly during August, and females during late August and early September. Females greatly outnumbered males at all times. Most wintering males departed late in March and early in April, but females not until about a month later. First-year birds appeared from the end of August, but remained in low numbers until late October or November. Most departed during April and May, but a few females oversummered. First-year birds typically accounted for about 25% of the wintering Nakuru females, but about 50% of those at Magadi. At both sites they accounted for a higher proportion of male birds than females. Most of the birds at Nakuru throughout late August to May appeared to be local winterers, and many individuals remained in the area for many months each year. Retrapping indicated that approximately 60% of each season's birds returned the following season. Adult males and most adult females commenced pre-winter wing moult before arrival, but completed most of it in Kenya. Males moulted 3–4 weeks ahead of females, and most had finished before December. Females typically finished during December and early January. Most second year birds timed their pre-winter moult similarly to older adults. Suspension was recorded in over 15% of all moulting birds examined. Adult pre-summer moult involved most or all of the tertials, some or all of the tail feathers, most of the inner wing coverts and the body and head plumage. It occurred mainly during January to March (males) or February to April (females), although tertial renewal commonly began a month earlier. Males showed no sign in Kenya of the supplementary prenuptial moult. First-year birds moulted from juvenile into first winter body plumage during late September to November. They underwent a pre-summer moult similar in extent and timing to that of adults, and again about a month earlier in males than females. Spring feathers acquired were often as brightly coloured as those of adults. About 15% of first-year birds renewed their outer 2–4 pairs of large primaries during January to April. Adult and first-year birds fattened before spring departure, commonly reaching weights 30–60% above winter mean. Weights of adult males peaked early in April, those of adult females early in May, and those of first-winter females later in May. Weights were relatively high also during August and September. This was due to the arrival of wintering birds carrying ‘spare’ reserves, and also apparently to the presence of a late moulting fattening passage contingent. The wing length of newly moulted adults was about 3 mm longer than that of newly arrived first-year birds, but there was no evidence of an increase in the wing kngth of adults with successive moults. Adult wing length decreased by 4–5 mm between the completion of one moult and the middle stages of the next. The migrations and annual timetable of Kenyan wintering Ruffs are discussed, and their moult strategy is compared with that of other Holarctic waders.     

Drift and upstream movement in Yuccabine Creek,an Australian tropical stream

Drift and upstream movement were monitored over 14 months in a seasonal upland tropical stream in northeastern Australia. There were distinct seasonal pulses in the drift with variable peak levels in the summer wet season and low more stable levels during the dry season. Drift density ranged from 0.36 to 3.98 animals per m³ (monthly mean = 1.26). There was no correlation between drift density and either benthic density or stream discharge. In the absence of catastrophic drift, drift was dispersive, not depletive in the wet season. A total of 121 taxa were caught in the 14 drift samples. Most taxa had nocturnal maximum drift levels with a peak immediately after sunset, a pattern apparently related to level of light and not temperature. Compensation for drift by upstream-moving nymphs and larvae was least during the wet season and increased during the dry season to a peak of 27% by numbers. Mean compensation was 8.2%. It is suggested that apart from in the wet season when an animal may drift substantial distances, most riffle animals will spend their larval lives in one small stretch of stream.     

Observations on parasitic gastroenteritis and bronchitis in grazing calves: effect of low level feed incorporation of morantel in early season.

Pott J. M., Jones R. M. and Cornwell R. I. 1979. Observations on parasitic gastroenteritis and bronchitis in grazing calves: effect of low level feed incorporation of morantel in early season. International Journal for Parasitology9: 153–157. Twenty-four castrated Friesian calves were divided into two equal groups on a body weight basis and grazed separate halves of an infected pasture. One group was given 1.5 mg/kg per day morantel tartrate in the feed over a period extending from 2 weeks before turning out in early May to early July. The other group of calves received an equivalent amount of unmedicated food as controls. Pasture larval counts showed a similar pattern and level of infection from February to July on both pastures. This consisted of a fall from moderate winter levels to very low levels in April/July. The control pasture then showed a typical sharp rise in August to high levels extending through September and falling to moderate levels in October. The pasture being grazed by treated calves showed only a small rise in larval counts in August. The total pasture contamination was reduced by 85% compared with controls during August/October. Faecal egg and larval counts showed similar differences between treated and control calves. Mild clinical signs of parasitic gastroenteritis and bronchitis were seen in controls but not in the treated group. The latter had a weight gain advantage of 20.5 kg the difference becoming marked in the last month of the trial.     

Gonadic cycle of the American oyster Crassostrea virginica (Lamellibranchia: Ostreidae) in Mecoacán, Tabasco, México

The American oyster Crassostrea virginica is exploited along Gulf of Mexico. This resource represents a job source and incomes for fishermen. In Mexico the production is supported by Tabasco state, the first producer. However, the mexican landings of this bivalve had been dropped about 40% last ten years. By 1999, Tabasco presents a unique ban season fishery of oysters. This season was based in evaluation of gonadal development by visual observations of color and texture, larvae and seeds abundance. In 2000, the government set up two ban seasons in terms of evaluation of populations every year, without gonadal analysis. In general, exists different spawning seasons for American oyster, in accordance with the environmental conditions. It is necessary to establish a ban season according to reproductive cycle. This study presents the gonadic cycle for an oyster population of Mecoacin lagoon along a year. It was defined five phases of the gonad development: resting, gametogenesis, mature or ripe, spawn and post spawn. Gametogenesis is present all the year, except December. The spawning activity was detected all year, except July and August. The ripe phase presented maximum values in August and December. It was proposed a modification of the ban seasons from April 15 - May 30, and September 15 - October 30 to March 15 - May 15 and September 1 - October 30, respectively, according to gonadic cycle obtained in this work. This modification would to avoid capture mature organisms (ready to spawn).     

Effect of seasonal climatic changes on biomass yield and terpenoid composition of rose-scented geranium (Pelargonium species)

Variations in biomass yield, essential oil yield and terpenoid composition in rose-scented geranium (Pelargonium species) in response to seasonal climatic changes were investigated under semiarid tropical climatic conditions. A large number of essential oil samples were collected during different seasonal months (once a month) and daily during the peak summer season months of May and June. They were analysed for terpenoid composition by GC and GC-MS. The crop yielded the lowest values for biomass yield, essential oil yield and essential oil concentration in the summer months of April to June. Evaluation of terpenoid compositions showed minimum concentrations (% of essential oil) of linalool, geraniol and its esters and maximum concentrations of citronellol and its esters during summer months. The percentages of geraniol and its esters were highest during cool winter season months of December and January followed by rainy and autumn season months. Isomenthone, 10-epi-gamma-eudesmol and other minor terpenoid compounds (present in <1% amounts in the essential oil) did not exhibit any definite seasonal trends. Rainy/monsoon (August and September) and autumn (October and November) season months were characterised by high rainfall, cloudy days and short photoperiods. These favourable environmental conditions encouraged crop growth and produced highest biomass yields, essential oil yields and maximum concentration of essential oil in rose-scented geranium plants.     

Seasonal variation in fatty acid composition of silver pomfrets,Pampus argenteus (Euphrasen), in Kuwait waters

Proximate and fatty acid composition of wild silver pomfrets, Pampus argenteus, were studied in Kuwait waters for a period of 1 year (November 2007–October 2008) to see whether there were any seasonal compositional differences between males and females. Ten adults (five males, five females) were sampled each month during (i) Pre‐spawning (March–May), (ii) Spawning (June–August), (iii) Post‐spawning (September–November), and (iv) Winter (December–February). Both sexes had significantly (P < 0.05) higher whole body moisture and lower crude protein and lipid contents in winter compared to the respective males and females sampled in other seasons. However, females had significantly higher (9.1%) lipid content during the pre‐spawning season than females in other seasons (7.0–8.2%). The most abundant fatty acid in whole body lipid in both sexes was C16 followed by C18:1n‐9, which accounted for about 31–35% and 22–24% of total lipids, respectively. Males in the pre‐spawning and spawning seasons had significantly higher total monosaturated fatty acids (MUFA) than males and females in post‐spawning and winter. Males had significantly higher total polyunsaturated fatty acids (PUFA) during post‐spawning seasons than females in pre‐spawning and winter seasons. However, there were no significant differences (P > 0.05) in total saturated fatty acids (SFA), PUFA, EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) or n‐3/n‐6 ratios between respective males and females in different seasons. Livers in males had significantly (P < 0.05) higher MUFA, SFA, PUFA, EPA and DHA than respective females in all months during the spawning season. Female gonads had significantly (P < 0.05) higher MUFA and PUFA but lower SFA content than males in different months during the spawning season. In contrast to the liver, the gonad DHA content and n‐3/n‐6 ratios in females were significantly higher than in males. The gonads from both sexes contained more than double the amount of EPA present in liver; in the case of DHA this was more than three‐fold higher in female gonads, but not in males. Thus, the presence of higher proportions of PUFA, EPA and DHA in gonads, particularly in eggs of silver pomfret, indicates their need for these fatty acids, which may be used as a guideline for dietary essential n‐3 fatty acid requirements for feed formulation of this species. A higher content of DHA in eggs also indicates the higher requirement for DHA in the broodstock diet of silver pomfret.     

Effect of frontal hypothalamic deafferentation on duration of breeding season and melatonin secretion in the ewe

The objectives of this study were to determine if ewes subjected to frontal hypothalamic deafferentation (FHD) during anestrus remained anestrus or began to have estrous cycles, and if melatonin secretion was disrupted by FHD. Ovary-intact ewes in Group 1 were subjected to either FHD (n = 10) or sham FHD (n = 5) in early July 1983. Estrous cycles were monitored by measuring circulating progesterone concentrations from before FHD until September 1985. Group 2 ewes (n = 4) were subjected to FHD in October 1984. In late April 1985, blood samples were taken from all ewes at 1- to 4-h intervals from 1100 h to 0700 h of the following day to monitor diurnal changes of melatonin. Hypothalami were collected for histological evaluation of lesions. All Group 1 ewes (sham FHD and FHD) initiated normal estrous cycles in August and September 1983, and all ceased cycles by mid-February 1984. All sham FHD and 4 FHD ewes remained anestrus until August or September of 1984 and then resumed normal cycles. In contrast, 5 FHD ewes resumed cycles as early as April 1984 and then cycled intermittently or almost continuously. Two Group 2 ewes cycled continuously after FHD and 2 cycled infrequently. FHD ewes that showed prolonged breeding seasons had cuts that damaged the suprachiasmatic nucleus (SCN) and adjacent structures. Mean nocturnal (2000 h-0500 h) melatonin concentrations did not differ (p greater than 0.05) between sham FHD, FHD "normal season," and FHD "continuous cycle" ewes. In summary, damage to the SCN region by FHD during anestrus had no detectable effect on either onset or cessation of the next breeding season but greatly prolonged subsequent breeding seasons. Thus, the environmental signals that both initiated and terminated the 1983 breeding season apparently had been given before FHD was performed in midsummer. Damage to the SCN region during the breeding season caused some ewes to cycle continuously. The effects of FHD apparently were not due to disruption of melatonin secretion. FHD ewes that showed prolonged breeding seasons had normal seasonal changes of plasma prolactin concentrations. This suggests that different neural structures control seasonal patterns of gonadotropin and prolactin secretion.