Life history, gonad state, and changes in functional sex ratio in the salt-marsh waterboatman, Trichocorixa verticalis (Fieber) (Heteroptera: Corixidae)

1995 ◽  
Vol 73 (3) ◽  
pp. 552-556 ◽  
Author(s):  
R. B. Aiken ◽  
N. Malatestinic
Keyword(s):  
Life History ◽  
Salt Marsh ◽  
Sex Ratio ◽  
Sexual Development ◽  
Mate Competition ◽  
Summer Generation ◽  
First Instar ◽  
Males And Females ◽  
Marsh Pools ◽  
Sexually Mature

The life history and sexual development of Trichocorixa verticalis were studied in salt-marsh pools in New Brunswick, Canada. Trichocorixa verticalis overwinters as an egg and the adults of the first summer generation appear in late June. The second summer generation appears as first-instar nymphs in mid-July. Males and females mature sexually about 1 month after eclosion, the first sexually mature females appearing 1 week before males. For most of the season, the numerical sex ratio is male-biased. The functional sex ratio (ratio of sexually mature males and females) is even more strongly male-biased. These results indicate that mate competition among males may be more severe than was initially apparent.

Population parameters of ringed seals (Phoca hispida Schreber, 1775) in the Svalbard area

1987 ◽  
Vol 65 (4) ◽  
pp. 1021-1027 ◽  
Author(s):  
Christian Lydersen ◽  
Ian Gjertz
Keyword(s):  
Sex Ratio ◽  
Ringed Seal ◽  
Adult Males ◽  
Population Parameters ◽  
Phoca Hispida ◽  
Age Class ◽  
Ringed Seals ◽  
Males And Females ◽  
The Mean ◽  
Sexually Mature

Samples were taken from 284 ringed seals (Phoca hispida) in the Svalbard area during April–July 1981 and March–April 1982. The age of 283 seals was determined by reading annuli in the cementum of the canine teeth. The mean age of the males was 11.3 years, and of the females, 14.9 years. Females were found to be significantly older than males. The mean length of sexually mature ringed seals was 128.9 cm for both sexes. The mean weight of adult males and females was 53.5 and 61.4 kg, respectively. Females were found to be significantly heavier than males. The sex ratio was 47.8% males and 52.2% females. Studies of microscopic sections of testis and epididymis from ringed seal males showed that 63, 75, and 80% of 5-, 6-, and 7-year-old animals, respectively, were sexually mature. The weights of testis and epididymis, diameters of tubuli, and the size of testis all showed a marked increase in the 5-year age-class. Macroscopic sections of ovaries from ringed seal females showed that 20, 60, and 80% of 3-, 4-, and 5-year-old animals, respectively, were sexually mature. The size of the ovaries showed a marked increase in the 5-year age-class. The ovulation rate of ringed seals from Svalbard was calculated to be 0.91.

Life History and Abundance of Mysis relicta in Lake Michigan

1978 ◽  
Vol 35 (9) ◽  
pp. 1165-1170 ◽  
Author(s):  
Mark D. Morgan ◽  
Alfred M. Beeton
Keyword(s):  
Life History ◽  
Key Words ◽  
Lake Michigan ◽  
Fourth Instar ◽  
Mysis Relicta ◽  
First Instar ◽  
Males And Females

Mysis relicta was sampled in Lake Michigan approximately monthly with an epibenthic sled, August 1975–July 1976. Total numbers ranged from a low of 23 m−2 in February to a high of 337 m−2 in May and averaged 188 m−2. It was possible to partition the population into five instars. Major peaks in proportions of first instar individuals occurred in March, July, and November. It took about 1 yr for first instar individuals to reach the fourth instar. Growth averaged a little less than 1 mm/mo. Males and females reached maturity and bred in the fourth instar, so females produced their first brood at 1 yr of age. Males died at this time, but females were found to molt to the fifth instar, mate, and produce a second brood approximately 4 mo later. Key words: Mysis relicta, Lake Michigan, life history, abundance

scholarly journals Gametogenesis of the gall-fly, Neuroterus lenticularis .—Part II

1911 ◽  
Vol 83 (566) ◽  
pp. 476-489 ◽  
Keyword(s):  
Nervous System ◽  
Life History ◽  
Nuclear Body ◽  
Summer Generation ◽  
Spring Generation ◽  
Complete Study ◽  
Males And Females ◽  
Sperm Nuclei ◽  
Developing Nervous System ◽  
Made In

In the first part of this paper I described the life-history, spermatogenesis, maturation of the fertilised egg, fertilisation and segmentation divisions of the summer generation of the gall-fly Neuroterus lenticularis ( Spathegaster baccarum ), and gave some observations on the maturation of the eggs of the spring generation, and on the somatic mitoses in males and females. These latter observations were admittedly incomplete owing to lack of material, and this second part of the paper attempts to complete the account of what was left uncertain in the first communication. Before proceeding to describe my fresh observations it may be well shortly to summarise the results arrived at in the fist part. The spring generation of N. lenticularis consists of females which lay parthenogenetic eggs; those laid by some females develop into sexual females, both of which hatch in June. The eggs of the summer females undergo a double maturation division, leaving 10 chromosomes in the nucleus of the mature egg. The spermatogonia of the males in the same generation have 10 chromosomes; the first spermatocyte division is suppressed; in the second spermatocyte division the chromosomes divide, 10 entering each spermatid. A small staining extra-nuclear body found in the spermatocytes does not divide, and is included in only half of the spermatids. In fertilisation, the egg and sperm nuclei each contain 10 chromosomes, and the segmentation divisions of the fertilised egg show 20. For a complete study of the maturation and segmentation of the parthenogenetic spring eggs my material was insufficient, but it suggested that the eggs laid by some females underwent maturation and showed 10 chromosomes in the segmentation divisions, and that others had no polar divisions and showed 20. Since somatic and oogonial mitoses of the summer female have 20 chromosomes, but the spermatogonial mitoses and those of the developing nervous system in the male only 10, it was suggested that the eggs which undergo maturation produce males, the others females. An attempt was made, in conclusion, to connect these phenomena with what is know of sex-determination in other animals.

LIFE HISTORY OF CRICOTOPUS MYRIOPHYLLI OLIVER (DIPTERA: CHIRONOMIDAE) IN THE OKANAGAN VALLEY, BRITISH COLUMBIA

1993 ◽  
Vol 125 (6) ◽  
pp. 979-985 ◽  
Author(s):  
Ian V. MacRae ◽  
Richard A. Ring
Keyword(s):  
British Columbia ◽  
Life History ◽  
Sex Ratio ◽  
Larval Instar ◽  
Field Observations ◽  
Laboratory Rearing ◽  
The Third ◽  
First Instar ◽  
History Of ◽  
Rate Of Emergence

AbstractThe life history of Cricotopus myriophylli Oliver is described from both field observations and laboratory rearing of field-collected larvae. The species appears to be univoltine with four larval instars and has a sex ratio of ca. 2:1, males to females. Emergence begins in late May in British Columbia and continues until mid-September, with first-instar larvae present in the field from mid-June to mid-August. Water temperature does not appear to influence the rate of emergence. In the laboratory at 21 °C, larvae complete each of the third and fourth instars in 10–14 days. Cricotopus myriophylli overwinters primarily in the third larval instar, although second and fourth instars were also recovered in field-collected samples. First-instar larvae and eggs were not recovered from winter samples. This species does not appear to undergo a true diapause.

Pineus pineoides (Cholodkovsky) (Homoptera: Adelgidae) on Red Spruce in New Brunswick and Nova Scotia

1963 ◽  
Vol 95 (7) ◽  
pp. 720-724 ◽  
Author(s):  
G. R. Underwood
Keyword(s):  
Life History ◽  
Life Cycle ◽  
North America ◽  
New Brunswick ◽  
Instar Nymph ◽  
Picea Rubens ◽  
Red Spruce ◽  
Summer Generation ◽  
First Instar ◽  
First Time

AbstractPineus pineoides was found for the first time in North America in New Brunswick in 1948, on red spruce, Picea rubens Sarg. It is the first known species of Adelgidae in North America to complete its life cycle on spruce without producing galls or winged forms. The life history is compared with that in Europe. The first-instar nymph and the adult of the summer generation are described and compared with those from Europe.

scholarly journals Sex ratio and parental investment in Trypoxylon (Trypargilum) agamemnon Richards (Hymenoptera, Crabronidae)

2014 ◽  
Vol 74 (1) ◽  
pp. 231-237 ◽  
Author(s):  
MLT Buschini ◽  
ACB Bergamaschi
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Conflict Of Interest ◽  
Life Histories ◽  
Overlapping Generations ◽  
Mate Competition ◽  
Southern Brazil ◽  
Trap Nests ◽  
Ratio Data ◽  
Local Mate

The life history and sex ratio data of the solitary wasp Trypoxylon agamemnon nesting in trap-nests in southern Brazil was recorded from January 2002 to December 2007. Its sex ratio is strongly female-biased, being bivoltine or multivoltine with until three generations per year. It has two alternative life histories (diapause and direct development) and overlapping generations. In addition to the conflict of interest between the sexes, it is possible that local mate competition occurs between males and may cause a greater investment in the production of females.

Age and growth of a newly described barb, Capoeta coadi (Cyprinidae), in Beheshtabad River, Tigris basin

2020 ◽  
Vol 56 ◽  
pp. 26
Author(s):  
Yazdan Keivany ◽  
Masoud Siami
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Sex Ratio ◽  
Age Groups ◽  
Fork Length ◽  
Age And Growth ◽  
Von Bertalanffy ◽  
Males And Females ◽  
Endemic Fish ◽  
Von Bertalanffy Growth Model

The Coad barb, Capoeta coadi Alwan, Zareian and Esmaeili, 2016, is a newly described endemic fish in Beheshtabad River, Tigris basin of Iran and little is known about its life-history. Life history characteristics were examined in 426 specimens collected monthly from Beheshtabad River (central Iran) during May 2013 to May 2014. The sex ratio was 1M:0.7F. Based on scale and opercular readings, the maximum ages of the population were 8+ years for females and 7+ for males. The most frequent age groups were 3+ and 4+ in males and females, respectively. Size varied from 8.94 to 42.95 cm in fork length and weight between 10.3 and 1255.5 g. Length–weight relationship implied that the growth was negatively allometric for both sexes. The von Bertalanffy growth model was estimated as Lt =35.97[1‑e‑0.205( t+0.586)] and Lt = 49.31[1‑e ‑0.162( t‑0.208)] for males and females, respectively. The growth performance index was estimated as 5.58 and 5.97 for males and females, respectively, indicating a faster growth rate for females.

Life History Traits in a Population of Pelobates syriacus (Boettger, 1889) from Turkey

2020 ◽  
Vol 27 (4) ◽  
pp. 195-200
Author(s):  
Ufuk Bülbül ◽  
Halime Koç ◽  
Yasemin Odabaş ◽  
Ali İhsan Eroğlu ◽  
Muammer Kurnaz ◽  
...  
Keyword(s):  
Life History ◽  
Age Structure ◽  
Life History Traits ◽  
Spadefoot Toad ◽  
Males And Females

Age structure of the eastern spadefoot toad, Pelobates syriacus from the Kızılırmak Delta (Turkey) were assessed using phalangeal skeletochronology. Snout-vent length (SVL) ranged from 42.05 to 86.63 mm in males and 34.03 to 53.27 mm in females. Age of adults ranged from 2 to 8 years in males and 3 to 5 years in females. For both sexes, SVL was significantly correlated with age. Males and females of the toads reached maturity at 2 years of age.

scholarly journals The impact of sex ratio and economic status on local birth rates

2013 ◽  
Vol 9 (2) ◽  
pp. 20130027 ◽  
Author(s):  
A. Chipman ◽  
E. Morrison
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Economic Status ◽  
Life History Strategy ◽  
Reproductive Behaviour ◽  
Female Competition ◽  
Birth Rates ◽  
Economically Deprived ◽  
Human Mating ◽  
The Impact

Human mating and reproductive behaviour can vary depending on various mechanisms, including the local sex ratio. Previous research shows that as sex ratios become female-biased, women from economically deprived areas are less likely to delay reproductive opportunities to wait for a high-investing mate but instead begin their reproductive careers sooner. Here, we show that the local sex ratio also has an impact on female fertility schedules. At young ages, a female-biased ratio is associated with higher birth rates in the poorest areas, whereas the opposite is true for the richest areas. At older ages, a female-biased ratio is associated with higher birth rates in the richest, but not the poorest areas. These patterns suggest that female–female competition encourages poorer women to adopt a fast life-history strategy and give birth early, and richer women to adopt a slow life-history strategy and delay reproduction.

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