Effects of environment and population density on the sea anemone Actinia tenebrosa

1984 ◽  
Vol 35 (6) ◽  
pp. 735 ◽  
Author(s):  
DJ Ayre
Keyword(s):  
Population Density ◽  
Intraspecific Competition ◽  
Sexual Maturity ◽  
Sex Ratios ◽  
Simple Relationship ◽  
Adult Size ◽  
The Mean ◽  
Breeding Seasons ◽  
Autumn And Winter ◽  
Western Australian

Within each of four Western Australian colonies of A. tenebrosa, adults developed gonads and brooded asexually produced juveniles during the summer months. The brooded juveniles were released throughout the year but most settlement occurred in autumn and winter. Dispersal of brooded juveniles was highly localized and they typically settled within 2 m of adults. Adults were sedentary and long- lived and recruitment rates were extremely low (about 1% per annum during the study period). Adult size and asexual fecundity differed markedly between colonies over three breeding seasons, but between-colony comparisons revealed no simple relationship between those characteristics. The mean number of juveniles per adult varied up to ninefold between colonies. Sex ratios deviated significantly from a ratio of 1 : 1 in samples from three colonies, and males predominated in two of these. Density-manipulation experiments revealed that intraspecific competition affected adult size, sexual maturity, asexual fecundity and rates of settlement and recruitment.

Variation within and between Rivers in Adult Size and Sea Age at Maturity of Anadromous Brown Trout, Salmo trutta

1991 ◽  
Vol 48 (6) ◽  
pp. 1015-1021 ◽  
Author(s):  
Jan Henning L'Abée-Lund
Keyword(s):  
Brown Trout ◽  
Sexual Maturity ◽  
Salmo Trutta ◽  
Adult Size ◽  
Age At Maturity ◽  
Migration Distance ◽  
Spawning Area ◽  
Brown Trout Salmo Trutta ◽  
Males And Females ◽  
The Mean

I compared adult size and sea age at sexual maturity among nine populations of anadromous brown trout, Salmo trutta, in two Norwegian rivers to determine the extent of inter- and intrariverine variations. Variation in the mean length of spawners and in the mean sea age at sexual maturity were mainly dependent on the variations found within rather than between rivers. Mean lengths and mean age at maturity of males increased significantly with increasing altitude of the spawning area and with migration distance in freshwater. In females, positive significant correlations were found with mean lengths and altitude of the spawning area and with mean sea age at maturity and both spawning site altitude and migration distance. Mean lengths and ages of males and females were not significantly correlated with the rate of water discharge in the streams during spawning. The size of gravel substrate for spawning was of minor importance in explaining interpopulation variation in mean female size. The increase noted in mean length and in mean sea age at maturity of both males and females is probably an adaptation to greater energy expenditure to reach the uppermost natal spawning areas.

Puberty, Physical Maturity, and Relative Growth of the Female Humpback Whale, Megaptera nodosa (Bonnaterre), on the Western Australian Coast

1955 ◽  
Vol 6 (3) ◽  
pp. 315 ◽  
Author(s):  
RG Chittleborough
Keyword(s):  
Body Length ◽  
Sexual Maturity ◽  
Humpback Whale ◽  
Humpback Whales ◽  
Relative Growth ◽  
Male And Female ◽  
The Mean ◽  
Sexually Mature ◽  
Western Australian

At puberty the mean body length of the female humpback whales on the Western Australian coast is 38.60 � 0.18 ft. It is demonstrated that this length gives a reliable means of calculating the proportion of sexually immature females in a series where the lengths are known. Sexual maturity (based upon the first pregnancy) may either follow immediately upon puberty or be delayed for a further year. At the approach of physical maturity (when epiphysial fusion begins) the mean body length is 45.08 � 0.29 ft. At this stage an average of 19 ovulations have occurred. On the available material, physical maturity is reached at a mean length of 44.34 � 0.72 ft, when close to 30 ovulations have occurred. Growth in body length of sexually mature females becomes very slow even before epiphysial fusion begins. The significance of the high number of ovulations before the attainment of physical maturity is discussed. The proportion of physically mature individuals amongst the females in recent catches off the Western Australian coast is extremely low (1.8 per cent. of 457 females examined). The lengths of male and female humpback whales at puberty, at the approach of physical maturity, and at physical maturity are compared.

Sex ratio and life history traits at reaching sexual maturity in the dioecious shrub Fuchsia parviflora: field and common garden experiments

2021 ◽  
pp. 1-6
Author(s):  
Jessica S. Ambriz ◽  
Clementina González ◽  
Eduardo Cuevas
Keyword(s):  
Natural Population ◽  
Sexual Maturity ◽  
Sex Ratios ◽  
Natural Populations ◽  
Common Garden ◽  
Common Garden Experiment ◽  
Trade Offs ◽  
Reproductive Biomass ◽  
Common Garden Experiments ◽  
Growth And Reproduction

Abstract Fuchsia parviflora is a dioecious shrub that depends on biotic pollination for reproduction. Previous studies suggest that the male plants produce more flowers, and male-biased sex ratios have been found in some natural populations. To assess whether the biased sex ratios found between genders in natural populations are present at the point at which plants reach sexual maturity, and to identify possible trade-offs between growth and reproduction, we performed a common garden experiment. Finally, to complement the information of the common garden experiment, we estimated the reproductive biomass allocation between genders in one natural population. Sex ratios at reaching sexual maturity in F. parviflora did not differ from 0.5, except in one population, which was the smallest seedling population. We found no differences between genders in terms of the probability of germination or flowering. When flowering began, female plants were taller than males and the tallest plants of both genders required more time to reach sexual maturity. Males produced significantly more flowers than females, and the number of flowers increased with plant height in both genders. Finally, in the natural population studied, the investment in reproductive biomass was seven-fold greater in female plants than in male plants. Our results showed no evidence of possible trade-offs between growth and reproduction. Despite the fact that female plants invest more in reproductive biomass, they were taller than the males after flowering, possibly at the expense of herbivory defence.

scholarly journals Population density of helminths in ducks: effects of host’s age, sex, breed and season

1970 ◽  
Vol 6 (1) ◽  
pp. 45-51 ◽  
Author(s):  
T Farjana ◽  
KR Islam ◽  
MMH Mondal
Keyword(s):  
Population Density ◽  
Key Words ◽  
Parasitic Infection ◽  
Winter Season ◽  
Helminth Parasites ◽  
Domestic Ducks ◽  
The Mean

 A study was conducted to investigate the population density of helminth parasites in domestic ducks (Anas boschas domesticus) in relation to host's age, sex, breed and seasons of the year from March 2002 to May 2003. A total of 300 ducks were collected from different villages of Netrokona and Mymensingh districts of Bangladesh and autopsied to collect the parasites and counted to determine the population density of parasites. Off 300 ducks examined, 290 (96.66%) were infected with 17 species of helminth parasites in which 11 species were trematodes, 4 were cestodes and 2 nematodes. Among the parasites, density of cestodes was the highest (33.15±5.26), followed by trematodes (5.98±1.32); and nematodes (2.95±0.68). Mean density of parasites increased with the increase of age (young: 21.23±1.09, adult: 26.18±2.14 and old: 27.87±2.98) while the mean density of most of the helminth parasites was higher in female ducks (31.35±4.72) than in males (27.52±3.32). Indigenous ducks (33.72±3.61) were infected with the highest load of helminths than Khaki Campbell breed (29.61±4.32) of ducks. Mean density of most trematodes (5.42±0.80) were highest in winter season whereas mean density of all cestodes (48.43±4.85) and nematodes (4.13±1.76) were highest in summer.  The present study suggests that age, sex, breed of ducks and seasons of the year influence the parasitic infection to a greater extend. Key words: Population density, helminths, duck, Bangladesh DOI = 10.3329/bjvm.v6i1.1338 Bangl. J. Vet. Med. (2008). 6 (1): 45-51

Life cycle of the western school prawn, Metapenaeus dalli Racek, in a Western Australian estuary

1986 ◽  
Vol 37 (1) ◽  
pp. 95 ◽  
Author(s):  
IC Potter ◽  
JW Penn ◽  
KS Brooker
Keyword(s):  
Life Cycle ◽  
Western Australia ◽  
Sexual Maturity ◽  
Second Year Of Life ◽  
Second Year ◽  
Australian Estuary ◽  
Western Australian

The absence of marine records for M. dalli below latitude 31�S., together with data on gonadal stages and spermatophore deposition on females of this species in the Swan estuary, provide very strong indications that the western school prawn typically breeds in estuarine environments in south-western Australia. The 0 + recruits, which first appeared in samples in February, remained in the estuary during the following months and by November had reached a size suitable for exploitation. At this time they were approaching sexual maturity and were starting to move from the shallows to the deeper waters of the estuary where they remained for their second year of life. In contrast to Australian Penaeus species, M. dalli mates during the intermoult period when the shell is hard rather than immediately after moulting.

scholarly journals Stochastic models for interference between searching insect parasites

1989 ◽  
Vol 30 (3) ◽  
pp. 268-277 ◽  
Author(s):  
Phil Diamond
Keyword(s):  
Stationary Distribution ◽  
Intraspecific Competition ◽  
Death Process ◽  
Confluent Hypergeometric Functions ◽  
Large Populations ◽  
The Mean ◽  
The One ◽  
Globally Stable ◽  
Insect Parasites ◽  
Birth Death

AbstractCompetition between a finite number of searching insect parasites is modelled by differential equations and birth-death processes. In the one species case of intraspecific competition, the deterministic equilibrium is globally stable and, for large populations, approximates the mean of the stationary distribution of the process. For two species, both inter- and intraspecific competition occurs and the deterministic equilibrium is globally stable. When the birth-death process is reversible, it is shown that the mean of the stationary distribution is approximated by the equilibrium. Confluent hypergeometric functions of two variables are important to the theory.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

scholarly journals Reproductive Biology of Round Sardinella (Sardinella Aurita) (Valenciennes, 1847) in Senegalese Coastal Waters

2018 ◽  
Vol 9 (1) ◽  
pp. 31
Author(s):  
Ismaïla NDIAYE ◽  
Alassane SARR ◽  
Alioune FAYE ◽  
Modou THIAW ◽  
Malick DIOUF ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Reproductive Biology ◽  
Coastal Waters ◽  
Sexual Maturity ◽  
Reproductive Parameters ◽  
Monthly Variation ◽  
Relative Fecundity ◽  
The Mean ◽  
Sardinella Aurita ◽  
Somatic Index

In this study, a total of 1068 specimens Sardinella aurita of which 553 females and 515 males were examined. The objectif of this study was to determine the reproductive parameters of Sardinella aurita. The sex ratio was significantly in favor of females (55%). The size at first sexual maturity was estimated at 18.9 cm for females and 18.0 cm for males. The monthly variation of sexual maturity stages and gonado-somatic index (GSI) allowed to locate the reproduction periods from February to June and from September to December. The mean absolute fecundity was estimated at 110.794 ± 7582 oocytes whereas relative fecundity was about 422 ± 26 oocytes per gram of female.

scholarly journals Sexual Maturity in Adolescents Suffering from Sickle Cell Disease: A Cross-sectional Study

2021 ◽  
Author(s):  
Vijay Shah ◽  
Akash Patel ◽  
Praful Bambharoliya ◽  
Jigisha Patadia
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Sexual Maturity ◽  
Tanner Stage ◽  
Cross Sectional Study ◽  
Reproductive Capacity ◽  
Sectional Study ◽  
Cell Disease ◽  
Cross Sectional ◽  
The Mean

Introduction: Sickle Cell Disease (SCD) is an inherited chronic haemolytic anaemia. The diseased person suffers from various complications such as anaemia, frequent infection, fever, hand-foot syndrome, stroke, etc. Puberty changes includes the appearance of the secondary sexual characteristics, increase in height, change in body composition and development of reproductive capacity. Aim: To study the sexual maturity and effect of multiple blood transfusions in adolescents suffering from SCD. Materials and Methods: It was a cross-sectional study conducted on 35 adolescents of age group 11 to 15 years, suffering from SCD. Study was conducted over a period of six months from March 2018 to September 2018 at Department of Paediatrics. SCD was diagnosed by Haemoglobin (Hb) electrophoresis. Weight and height were measured of all the participants. For assessing the sexual maturity, Tanners staging was used. Unpaired t-test was done for data analysis. Results: The mean age of the patients was 13.03±1.7 years. There were 25 males and 10 females. The mean age of male patients between Tanner stage 2(14.63±0.52 years) and Tanner stage 3 (14.75±0.5 years) was significantly higher than the Indian data for males (11.3 and 12.8 years, respectively). The mean age of female patients between Tanner stages 2 (13.5±2.12 years) and Tanner stage 3 (14.33±1.16 years) was higher than the Indian reference data for girls (10.2 and 11.6 years respectively). Conclusion: This study concluded that adolescents with SCD were significantly shorter in height and weight than the standard reference population. Sexual maturity is delayed in adolescents with sickle cell anaemia.

The breeding behaviour of the endangered regent honeyeater, Xanthomyza phrygia, near Armidale, New South Wales

1998 ◽  
Vol 46 (2) ◽  
pp. 153 ◽  
Author(s):  
Damon L. Oliver
Keyword(s):  
New South ◽  
New South Wales ◽  
Population Level ◽  
Similar Rate ◽  
Nest Construction ◽  
Aggressive Interactions ◽  
Breeding Behaviour ◽  
South Wales ◽  
The Mean ◽  
Breeding Seasons

The regent honeyea ter, Xanthomyza phrygia, is an endangered woodland bird whose range and population size have decreased in the last thirty years. Suggested reasons for this decline include abnormal breeding behaviour, poor reproductive output, and excessive inter- and intra-specific aggression. This study investigated the breeding behaviour and aggressive interactions of regent honeyeaters during the nest construction, incubation, nestling, and fledgling stages in two consecutive breeding seasons in the Bundarra–Barraba region near Armidale, New South Wales. The female was entirely responsible for nest construction and incubation, which is typical of many honeyeaters. Both parents fed the nestlings, and at a similar rate, although only the female brooded chicks on the nest. Both parents fed the fledglings. The mean frequency at which nestlings (23 times per hour) and fledglings (29 times per hour) were fed is the highest published rate of any non-cooperative honeyeater. Breeding males were involved in significantly more aggressive interactions with conspecifics and other nectarivores than were females, although the overall percentage of day-time spent in aggression for both sexes was low (2.5%). It appears that abnormal breeding behaviour, poor reproductive effort, or excessive aggression are not experienced by this species in northern New South Wales, and that other factors are likely to be responsible for its current low population level.

Sign in / Sign up

Export Citation Format

Share Document