Seasonal Variation In Number Research Articles

Annual cycle of the Sertoli cell population in adult stallions.

Stereological methods were employed in two experiments with adult stallions: to confirm seasonal variation in number of Sertoli cells and to characterize the annual cycle of the Sertoli cell population. In the first experiment, testes from 28 adult (4-20 years old) horses obtained in the non-breeding season (December-January) were compared to testes from 28 adult horses in the breeding season (June-July). Sertoli cell numbers were calculated from the nuclear volume density, parenchymal volume, and volume of an individual Sertoli cell nucleus determined by reconstruction of serial sections or from average height and width measurements. The number of Sertoli cells per testis was significantly greater in the breeding season. In a second experiment involving 43-48 adult horses in each 3-month period, the Sertoli cell population was higher (P less than 0.05) in May-July than other periods and higher (P less than 0.01) than in November-January. These combined studies confirm seasonal differences in the Sertoli cell numbers per testis and define the annual cycle of the Sertoli cell population in adult stallions.

Prevalence of helminth parasites in three species of cichlids from a man-made lake in Zambia

A study of certain aspects of two man-made lakes at the University of Zambia Lusaka Campus was carried out. The three species of cichlids with which the lakes were stocked: Tilapia rendalli (Boulenger, 1896); Oreochromis (formerly Tilapia) macrochir (Boulenger, 1910) and O. (formerly T.) andersonii (Castelnau, 1896) were examined for helminth parasites. The most numerous was Cichlidogyrus Paperna, 1960; followed by Acanthogyrus (Acanthosentis) tilapiae Baylis, 1948. A few metacercarial cysts of Clinostoman Leidy, 1856; a few cysticercoids of Paradilepis delachauxi Fuhrm, 1909 and a single specimen of a probable new genus of Monogenea (near Diplozoon Nordmann, 1832) were also found. The prevalence and seasonal variation in numbers of the two most common parasites are discussed in relation to parasite loads in different ages and sexes of the host fish.

A new type of histamine-forming bacteria - III. Seasonal variations in numbers of psychrophilic and halophilic histamine-forming bacteria (N-group bacteria) in seawater and on marine fishes.

In the previous papers, the authors repored that a new type of histamine-forming bacteria (tentatively named N-group bacteria) was isolated from a common a mackerel, and that this group of bacteria were also found in Pacific saury and sardine, and gew well at 2.5 storage of thee fish samples. The present study was undertaken to obtain more information as to seasonal variation in the mumber of N-group bacteria in seawater and on the fisher skins and intesines. N-group bacteria werre found most abundantly in the sewater during the late autumn and winter, and it is considered that this group of bacteria strikingly decreased in number when the water temperature rose above 22°C. The majouity of the fresh fish samples had less than 100 organisms of organisms of N-group bacteria per cm2 of skin; and especially in the summer samples, they were below 10 orgainisms. The number of this group of bacteria increased at 2.5storage of the fish samples and eached to 107-108 level in a few samples. This group of bacteria were found in all of the intesine amples, where their number ranged from 103 to 108 per gram. A selective enrichment medium with PH 4.5 was devised for detection and isolation of N-group bacteria.

A modified drop‐net method for sampling mobile epifauna on marine shallow sandy bottoms

The seasonal variations in numbers and biomass of the mobile epifauna of a shallow, sandy bay in Gullmar Fjord (Sweden) was investigated during 1976–1977 using the drop‐net technique. Juvenile plaice, Pleuronectes platessa L., sand goby, Pomatoschistus minutus (Pallas), and brown shrimp Crangon crangon L. are the dominant epifaunal species. A net enclosing an area of 100 m2 was used, and the organisms captured were collected with a small trawl. Three stations with a water depth≤ 1 m were regularly sampled with a total number of 73 drops. Maximum abundance was for plaice in June (6 ind m‐2), for the shrimp in July‐August (61 ind m‐2), and for sand goby in September (2 ind m‐2). Standing stocks (dry wt) were 0.2, 1.5 and 0.2 g m‐2 respectively. Production estimates were based on seasonal changes in size frequency and information on specific growth rates. The production rate was for plaice (0‐group) 0.3 g m‐2 yr‐1, for the shrimp 1.5, and for sand goby 0.2 g m‐2 yr‐1. Reliable estimates of the absolute abundance can be derived from the mean catch per unit area only when the efficiency of the fishing gear is known. After 6 hauls with the trawl in the drop‐net enclosure more than 85% of the shrimps were caught and after the fifteenth haul less than 1% were still left. The fishing efficiency of a push‐net in relation to the drop‐net was for the shrimp 50%, for plaice 35% and for sand goby 17%.

Contributions to the Biology of freshwater planarians (Turbellaria) from the Victorian Alps, Australia

The ten species of freshwater planarians known from Victoria, including one new species, are briefly reviewed. Detailed field and laboratory studies of six of these have been made and a close correlation between seasonal variation in numbers and viability at different laboratory temperatures is demonstrated. Thus Spathula camara and Reynoldsonia reynoldsoni inhabit temporary habitats that experience wide temperature fluctuations and these two species survive equally well in the laboratory at a wide range of temperatures. In contrast Spathula tryssa appears stenothermal in habitat and in the laboratory cannot tolerate even a small temperature increase. Cura pinguis and Dugesia (Girardia) sp. also show wide temperature tolerance both in terms of abundance in the field and viability studies in the laboratory. Spathula agelaea sp. nov. is unusual in that it shows two annual peaks in abundance and also exhibits aggregatory and cannibalistic behaviour that may be involved in population regulation. Aspects of the distribution, abundance, and life cycle, of all the species are discussed in relation to what is known generally of planarian ecology.

Seasonal variations in number of acidophilic iron-oxidizing bacteria and iron oxidation in the river contaminated with acid mine water

Abstract Number of acidophilic iron-oxidizing bacteria, soluble iron, pH, and water temperature were measured seasonally at five sampling stations in the Akagawa River which is highly polluted by strongly acid mine water discharged from the abandoned Matsuo sulfur and iron-sulfide mine area. Other environmental variables of the river water were also determined (titratable acidity. dissolved oxygen, electrical conductivity, sulfate, aluminum, ammonia and nitrate-nitrogen, and phosphate). Distinct seasonal variations in the number of iron-oxidizing bacteria and ferric iron concentration were observed of the river water during the flow and were correlated with seasonal change in water temperature. Hydrogen ion concentration, dissolved oxygen, nutrients for microorganisms, such as, nitrogen and phosphate in the water of the main stream were judged to be not limited to iron oxidation or bacterial growth. Thus, water temperature was found to be a major environmental factor influencing on the activity of iron ox...

Seasonal Variation in Numbers of Chlamydospores in Victorian Forest Soils Infected With Phytophthora cinnamomi

Chlamydospore numbers were counted for 2 years on replicated soil samples from three different types of naturally infected Victorian native forest. Soil temperatures and soil water potentials were recorded concurrently. A highly significant seasonal variation in chlamydospore numbers was observed with maxima from summer to autumn and minima from winter to spring. There was little variation either between replicates or between different forest soils in winter and spring counts, but there was highly significant variation between different forest sites during the large summer and autumn counts. At this period sandy soil contained five to 12 times the number of chlamydo- spores found in other soils. For example, in autumn 1977,286 chlamydospores were recorded per 50 g sample from deep sandy soils compared with 31 for krasnozem and 17 for shallow duplex soils. At this period soil temperatures were similar but the soil water potential for the duplex soil was very low (-82 bars).

WADER POPULATIONS (CHARADRII) OF THE MARINE LITTORAL OF THE CAPE PENINSULA, SOUTH AFRICA

Summary Pringle, J. S. & Cooper, J. 1977. Wader populations (Charadrii) of the marine littoral of the Cape Peninsula, South Africa. Ostrich 48: 98–105. Waders (Charadrii) were counted regularly on two stretches of coastline, totalling 5,6 km, on the Cape Peninsula from January 1975 to July 1976. Eight Palaearctic species and seven indigenous species were observed. Arrival of migrants extended from mid-August to January. Autumn departure of Curlew Sandpipers Calidris ferruginea occurred approximately six weeks before departure of Sanderlings C. albu. No overwintering populations of migrant waders were observed. Information is presented which suggests that overwintering Turnstones Arenaria interpres, but not Sanderlings, Maycongregate at a sheltered coastal wetland. Observations of marked birds suggest that individual Sanderlings regularly use particular feeding localities. Populations of indigenous waders showed little seasonal variation in numbers, Flocking was observed in winter.

A Four-year Census of Wading Birds on the Ribble Estuary, Lancashire/Merseyside

The Ribble Estuary has a key role as a moulting ground and staging post for migrant waders, while it is also internationally important for the size of its winter wader population. Seasonal variations in numbers are analysed in species accounts.

Analysis of Number of Prescriptions and Amount of Dispensing Services

In the previous report, seasonal variation in number of prescriptions and amount of dispensing services was analyzed by moving average method. Statistical analysis of the amount of dispensing services is made in the following on regression equation by the method of least inspection. Then, modified seasonal variation was compared with analyzed original data. As a result, the method of analysis of RUN on the basis of the total number of the run separated on the median line proved simple and useful. Change in regression equation was not so different between the original data and modified seasonal variation. Since the interval estimation of the amount of services showed a marked reduction, the modified seasonal variation may be very applicable in prediction. According to the statistical analysis, modified seasonal variation produced better results than original data, data on outpatints than total data, and daily average than monthly total.

Variations in the pituitary-interrenal axis and the abundance of circulating blood-cell types in juvenile coho salmon, Oncorhynchus kisutch, during stream residence.

According to histological and histometric indices, the pituitary–interrenal axis of juvenile coho salmon residing in a natural stream was inactive in postalevin fry sampled in the spring, and in summer and fall samples of fingerlings, compared with a December sample or with smolts captured the next spring. Interrenal nuclear diameters, interrenal cell size, and epsilon (adrenocorticotropin) cell nuclear diameters were highly positively correlated.The numbers of circulating small lymphocytes and thrombocytes were highest in summer samples. Numbers of circulating large lymphocytes and neutrophils (per thousand cells of all types) were small and did not differ from sample to sample.Histometric indices of pituitary–interrenal axis activity were negatively correlated with numbers of circulating small lymphocytes but were unrelated to thrombocyte counts. Water temperature during sampling was highly negatively correlated with interrenal number and cell size and epsilon-cell nuclear diameters, and positively correlated with small lymphocyte and thrombocyte counts.It was concluded that the pituitary–interrenal axis in juvenile coho salmon was activated by both cold-temperature acclimation and smoltification. Unlike thrombocytes, the seasonal variations in numbers of circulating small lymphocytes were attributed to adrenocortical secretory activity.

Status and Aspects of the Life History of the Bottlenose Dolphin, Tursiops truncatus, in Florida

Aerial censuses in waters of the Everglades National Park, Florida every 1–2 mo between September 1973 and August 1974 resulted in sightings of a minimum of five, a maximum of 79, bottlenose dolphins. Seasonal variation in numbers apparently occurs.

BIOLOGY AND BEHAVIOUR OF FRIGATEBIRDS FREGATA SPP. ON ALDABRA ATOLL

SummaryBoth species nested in mixed colonies in mangrove trees. The tops of trees were usually occupied exclusively by minor and the lower parts by ariel, but most nests of both species were in the intermediate parts of the canopy. The main laying season for both species was July to January. A census showed about 27 000 individuals present at the height of the season (1500 breeding pairs of minor, 5350 of ariel). Seasonal variation in numbers could be accounted for almost entirely by the changes in breeding activity of a resident population. Young of both species were fed at or near the nest‐site for at least four months after fledging. A recovery near Bombay of a wing‐tagged immature ariel shows that this species, at least, undergoes a post‐fledging dispersal; it is suggested that young minor either do not disperse, or do so later than ariel.Food samples collected from chicks showed no overall difference between the species, but a seasonal analysis showed that ariel took more squid than minor in the wet season, and in the dry season the two species took different proportions of the two commonest species of flying‐fish. Chicks of ariel received smaller meals than minor chicks in the wet season, but similar‐sized meals in the dry season; ariel chicks grew more slowly than minor chicks. It is suggested that the timing of the breeding season is related to the need for adults to build up fat reserves to carry them through the courtship, nest‐building and laying periods, when they are tied to the colony and so have little opportunity to feed.The evidence for non‐annual breeding in frigatebirds is discussed. It is concluded that while successful breeders must breed at intervals of more than 12 months, they could theoretically nest in two successive seasons and that, since breeding success is low, most individuals probably do so.Existing knowledge of the biology of four of the five recognized species of frigatebirds is summarized, and shows that the family is at least as uniform as the tropicbirds and much more so than other Pelicaniformes.

Seasonal variation in numbers of the rabbit flea on the wild rabbit.

Samples of rabbits were obtained throughout each month over the 4-year period 1967-70. All fleas were removed, sexed and counted and the reproductive condition of the rabbits recorded. Rabbit fleas Spilopsyllus cuniculi (Dale) were present on both sexes of rabbit at all times of the year. In each year significantly high numbers of fleas were found on the rabbits in January, February, March and April and significantly low numbers in August, September and October. Mean flea counts were significantly higher on female rabbits than on males during April, May and June. During the rest of the year counts from each sex of host did not differ significantly. There were significant differences in flea numbers between years. More female than male fleas were found on both sexes of host throughout the year. The rabbit population sampled is shown to be typical of post-myxomatosis populations with regard to breeding performance and juvenile mortality. The relationship of the observed patterns of change in flea numbers to host and flea breeding and to host behavior, population size and structure is discussed.

Seasonal Variation in Sucker Production from Excised Roots of Populustremuloides and the Role of Endogenous Auxin

Seasonal variation in number of suckers produced from root cuttings of three clones of trembling aspen (Populustremuloides Michx.) was related, in a negative manner, to the quantity of endogenous auxin in the roots when collected. The mean number of suckers per cutting varied with the clone of origin and time of collection.

Migrant waders at Aldabra, September 1967—March 1968

Observations of palaearctic waders during the first three phases of the Royal Society Expedition to Aldabra, between 1 September 1967 and 14 March 1968 are listed and compared with those from other places in the area. Seventeen species are included in the check list, of which four are considered vagrants, and the rest more or less regular migrants. Counts made during the expedition with the intention of finding the seasonal variation in numbers of the birds have proved statistically invalid, and only a few tentative conclusions may be drawn from them. The Turnstone, Arenaria i. inter pres , may be a winter resident in fair numbers, as may the Whimbrel, Numenius p. phaeopns . Although no firm conclusion can be drawn, it is suggested that most of the other birds are passage migrants, with few staying at Aldabra for the winter. Thus the island is not an important wintering ground for any species, though it probably has some value as a resting place for the birds during their migratory flights. For the Crab Plover, Dromas ardeola , however, it may be one of the few wintering grounds where the species occurs in any numbers, and as such important. The suggestion is made that the other islands in the Indian Ocean, east of the axis of Madagascar, may function not as a destination but as a ‘safety net’ for vagrant birds or flocks.

Amphipods in the Surf Plankton

The study of diurnal vertical movements of macro-plankton (Russell, 1925) showed that many organisms, including amphipods migrated to the surface of the sea at night. Since this work there have been several papers reporting vertical movements in intertidal waters. Elmhirst (1931), demonstrated that certain species of amphipod swam in the surf zone during the night and that they showed seasonal variations in numbers, with a spring maximum. Subsequently, Watkin (1939, 1941) distinguished between those in-faunal species performing nocturnal vertical migrations into the surf and tidal immigrants carried in from sub-littoral habitats by the tide.

Seasonal Abundance and Distribution of Benthic Fauna within a Pond

A Tennessee pond was sampled weekly from June 18 to August 20, 1968, to determine quantitative differences among benthic organisms in sampling depths and dates. Annelids (Oligochaeta), Chironomidae larvae, and Chaoboridae larvae were the dominant organisms collected. Preferred depths existed for each group of organisms. Chaoboridae and Chironomidae exhibited distinct seasonal variations in numbers, with the population decreasing throughout the summer. Chaoboridae were the most and Chironomidae the least numerous of the 3 groups.

Movement and Distribution of Smallmouth Bass in the Middle Snake River

The movement and distribution of smallmouth bass, Micropterus dolomieui, were studied in the Snake River, a large western river, prior to impoundment. A tag and recovery program was designed to assess interpool movement. Smallmouth bass were collected by angling and electrofishing. Primacord, a detonating fuse, was used to assess distribution during late fall and winter. Underwater observations were made with SCUBA apparatus. Bass behavior was studied in the laboratory and dealt principally with temperature effects, light intensity and substrate. Only 8% of the tagged fish recaptured were taken by anglers; the remaining 92% were taken by electrofishing. Ninety-nine (76%) of the recovered fish free at least 7 days were found in the same pool or defined location in which they were tagged, while 22 of the 31 fish recovered outside the pool in which they were marked had moved less than 1200 m (1,312 yds). A few moved several kilometers upstream or downstream from the release point. There was no significant seasonal variation in numbers of fish moving in different seasons, although there seemed to be slightly more movement in spring and less in summer than the mean movement. The distances moved at various seasons were not significantly different, nor was the seasonal direction of movement. A preference for broken rock substrate was indicated in the river by high fish densities over this type of substrate. Few smallmouth bass were found over a solid rock substrate, and none was observed over sand. In late fall, as water temperatures dropped below 15.5 C (60 F), smallmouth bass could not be located by electrofishing in water less than 2.3 m (8 ft) deep, but were found in still rocky pools at least 3.6 m (13 ft) deep by detonating primacord on the pool bottoms. The distribution of smallmouth bass within a pool changed during the 24-hour day. Smallmouth bass observed in early morning were all near the edge of the current. When the location of the edge of the current changed due to fluctuating water level, the bass shifted to the new position of current edge. In early morning no bass were observed more than a few meters from the edge of the current. Nocturnal positions of smallmouth bass were on or beneath a broken rock substrate in still water. When beneath the substrate bass faced toward an exit. No movement by smallmouth bass was observed in the river at night. In the laboratory smallmouth bass fed during the day and went on or beneath the substrate during darkness. This change in position took place at dusk. Some individuals appeared to defend night locations and rock substrate appeared preferable to sand. Fish came out from beneath the substrate at low light intensities in the morning. Activity decreased with temperature. Most of the fish remained beneath the substrate while temperatures were less than 6.7 C (44 F) and came from beneath the substrate when the water temperature reached 7.8 C (46 F).

The spatial and seasonal distribution of microscopic fungi in Arable soils

The results from comprehensive, regularly repeated analyses of soil fungi in two wheat-field soils were examined for information about preferential colonization of microhabitats and for seasonal variation in numbers of fungi. Using a soil washing technique, a limited number of species was found with significant preference for organic particles. The majority of species, however, were equally well or better represented on mineral particles. In some cases, where a slightly higher percentage of isolations was found on organic particles, the results for a series of analyses were nevertheless more constant for mineral particles. The latter are, therefore, to be preferred for soil fungus analyses. An exception must be made, however, for Fusarium spp., Mucor hiemalis, and Gaeumarmomyces graminis, which showed a more pronounced predilection for organic particles. Seasonal variation could not be demonstrated for most species, since the variation within a plot was almost as high as that between different sampling dates. Slight increases in the summer months were observed for Verticillium nigrescens and some of the most common species in these soils, but only in V. nigrescens was the seasonal effect statistically significant.