Maturation génitale des varans du nil mâles (Varanus niloticus) dans trois populations du Sahel

1999 ◽  
Vol 77 (2) ◽  
pp. 222-232 ◽  
Author(s):  
Vivian de Buffrénil ◽  
Jacques Castanet ◽  
Frédérique Rimblot
Keyword(s):  
Body Size ◽  
Sexual Maturity ◽  
Morphometric Study ◽  
Lake Chad ◽  
Breeding Stock ◽  
Size At Sexual Maturity ◽  
Monitor Lizards ◽  
Mature Spermatozoa ◽  
Accurate Indicator

Genital maturation of male monitor lizards, a subject poorly documented up to now in spite of the heavy exploitation of these animals, was studied on a sample of 211 Nile monitors (Varanus niloticus) from Chad (Lake Chad), Mali (central delta of the Niger), and Nigeria (Hadejia-N'Guru wetlands). Snout-vent lengths (LC) in the sample ranged from 15.6 to 85.5 cm. After a morphometric study of the monitors, their testes were sampled, weighed at ±0.01 g and fixed for histology. The age of each specimen was estimated by skeletochronology. The testes of monitors less than 36 cm LC (Malian specimens) or 40 cm LC (Chadian and Nigerian individuals) do not contain mature spermatozoa, whereas the testes of larger specimens do. Most Malian monitors aged 18 months (1.5 years) have mature spermatozoa. Conversely, in Chadian and Nigerian individuals, mature gametes appear only in specimens aged 30 months (2.5 years). These data indicate that genital maturity in the Nile monitor is reached at 36-40 cm LC and 1.5-2.5 years according to the populations. The growth in mass of the testes, compared with LC, is an accurate indicator of body size at sexual maturity, and confirms the precocity of Malian specimens. Conversely, testis growth is poorly related to age. These results are discussed with reference to the possible accommodation of Nile monitor populations to heavy exploitation by means of precocious recruitment of the male breeding stock.

Comparative life history features of the western spotted frog, Rana pretiosa, from low- and high-elevation populations

1975 ◽  
Vol 53 (9) ◽  
pp. 1254-1257 ◽  
Author(s):  
Lawrence E. Licht
Keyword(s):  
British Columbia ◽  
Life History ◽  
Body Size ◽  
Sexual Maturity ◽  
High Elevation ◽  
The Body ◽  
Female Fecundity ◽  
Size At Sexual Maturity ◽  
Rana Pretiosa

Comparisons are made of life history features of the western spotted frog, Rana pretiosa pretiosa, living at 70 m in southwestern British Columbia, and 2600 m in Yellowstone Park, Wyoming.Lowland tadpoles remain longer as larvae and transform at twice the body size as highland tadpoles.Growth rates of juveniles and adults are rapid in the lowland population and the same amount of growth achieved by them in 2–3 years takes 8–10 years for highland frogs.Body size at sexual maturity is the same for frogs from both populations, but B.C. frogs breed at half the age of Wyoming frogs. Female fecundity, the number of eggs at spawning, is the same, but lowland females breed annually, while high-elevation females breed only every 2 or 3 years.Various explanations are put forth to account for observed differences.

Importance of reproductive biology of a harvest lizard, Tupinambis merianae, for the management of commercial harvesting

2015 ◽  
Vol 42 (8) ◽  
pp. 697 ◽  
Author(s):  
Sergio Naretto ◽  
Gabriela Cardozo ◽  
Cecilia S. Blengini ◽  
Margarita Chiaraviglio
Keyword(s):  
Body Size ◽  
Clutch Size ◽  
Sexual Maturity ◽  
Biological Information ◽  
Specific Information ◽  
Central Argentina ◽  
Management Plans ◽  
Size At Sexual Maturity ◽  
Tupinambis Merianae ◽  
The Relationship

Context Management of the exploitation of resources requires biological information on exploited species. The skins of large reptiles have a commercial value as luxury leather items and Tupinambis lizards from southern South America have historically been exploited for this purpose. Argentina implemented management plans for Tupinambis lizards since 1988 that established a minimum capture size based on the width of dried skins, but this prescription has not been linked to local reproductive attributes of species. Aim In this study, we aim to determine the reproductive parameters of Tupinambis merianae and evaluate which class sizes of individuals are susceptible to commercial trade in central Argentina to generate local and species-specific information to improve available management tools. Methods We determined the relationship between the width of dried skins and live body sizes. We identified size at sexual maturity in males and females. Moreover, we determined status of reproductive individuals by body size and characterised gonadal development and seasonal reproductive events in central Argentina. We evaluated the relationship between female body size and clutch size. Key results Reproduction of T. merianae in central Argentina is markedly seasonal, with both sexes concentrating their reproductive activities between October and December. Size at sexual maturity was smaller for males than females, and the percentage of reproductive females was lower than males. In both sexes, the frequency of reproductive individuals was low in smaller lizards, and bigger females had bigger clutch size. The width of dried skins was positively related to body size. Conclusions Size at sexual maturity, and reproductive period, should be taken into account when management plans are designed to minimise any negative impacts of harvesting. Implications In central Argentina, the breeding season coincides with hunting periods set by national legislation. The results of our study have prompted local authorities to impose hunting closures for part of December and to raise the minimum catch size. Further, we offer an equation that can be used as a monitoring tool for estimating snout to vent length of live animals from skins. Studies like ours should be replicated in different areas and extrapolated to other models.

WEIGHT AT MENARCHE: SIMILARITY FOR WELL-NOURISHED AND UNDERNOURISHED GIRLS AT DIFFERING AGES, AND EVIDENCE FOR HISTORICAL CONSTANCY

PEDIATRICS ◽  
1972 ◽  
Vol 50 (3) ◽  
pp. 445-450
Author(s):  
Rose E. Frisch
Keyword(s):  
Genetic Variation ◽  
Body Size ◽  
Causal Relationship ◽  
Sexual Maturation ◽  
Sexual Maturity ◽  
Historical Evidence ◽  
Critical Weight ◽  
Size At Sexual Maturity ◽  
The Mean

The mean weight at menarche of 30 undernourished Alabama girls did not differ from that of 30 well-nourished controls, although the undernourished girls attained menarche two years later than controls and at a significantly greater height. This supports the hypothesis that a critical weight triggers menarche. The weight-dependency of menarche, irrespective of a causal relationship, reduces variation in body size at sexual maturity by delaying or advancing the age of sexual maturation as a compensation for environmental or genetic variation. Recent and historical evidence indicates that the mean weight at menarche of Caucasian girls has been about 46 kg. for over a century.

scholarly journals Use of otoliths to estimate size at sexual maturity in fish

2000 ◽  
Vol 43 (4) ◽  
pp. 437-440 ◽  
Author(s):  
Carlos Sérgio Agostinho
Keyword(s):  
Sexual Maturity ◽  
Line Segments ◽  
Alternative Method ◽  
Straight Line ◽  
Size At Sexual Maturity

The viability of an alternative method for estimating the size at sexual maturity of females of Plagioscion squamosissimus (Perciformes, Sciaenidae) was analyzed. This methodology was used to evaluate the size at sexual maturity in crabs, but has not yet been used for this purpose in fishes. Separation of young and adult fishes by this method is accomplished by iterative adjustment of straight-line segments to the data for length of the otolith and length of the fish. The agreement with the estimate previously obtained by another technique and the possibility of calculating the variance indicates that in some cases, the method analyzed can be used successfully to estimate size at sexual maturity in fish. However, additional studies are necessary to detect possible biases in the method.

scholarly journals A comparison of the allometric growth in Uca leptodactyla (Crustacea: Brachyura: Ocypodidae) from two subtropical estuaries

2004 ◽  
Vol 84 (4) ◽  
pp. 733-735 ◽  
Author(s):  
Rosana Carina Flores Cardoso ◽  
Maria Lucia Negreiros-Fransozo
Keyword(s):  
Growth Pattern ◽  
Sexual Maturity ◽  
Carapace Length ◽  
Brazilian Coast ◽  
Allometric Growth ◽  
Size At Sexual Maturity ◽  
Subtropical Estuaries ◽  
Habitat Similarity

The allometric growth of Uca leptodactyla from two distinct subtropical estuaries on the Brazilian coast was evaluated concerning its growth pattern and size at onset of sexual maturity. Females attained maturity at similar sizes in both sites (4·1 mm of carapace length in Indaiá and 4·2 mm in Ubatumirim), while males differed slightly. They reached the size at sexual maturity of 5·3 mm of carapace length in Indaiá and 4·6 mm in Ubatumirim. Growth pattern is usually similar among crabs from distinct sites while size at sexual maturity is frequently different. However, in the case of U. leptodactyla it did not occur, probably due to the strong habitat similarity and intrinsic features of this species.

scholarly journals Seasonal variations in the population biology of Salmostoma bacaila (Cyprinidae) from a tributary of the Payra River, Bangladesh

2019 ◽  
pp. 113-119
Author(s):  
Ahamed Ahamed ◽  
Faruque Ahmed Zoarder ◽  
Jun Ohtomi
Keyword(s):  
Sex Ratio ◽  
Seasonal Variations ◽  
Population Biology ◽  
Sexual Maturity ◽  
Condition Factor ◽  
Gonadosomatic Index ◽  
Spawning Season ◽  
Frequency Distributions ◽  
Size At Sexual Maturity ◽  
Management And Conservation

Some biological parameters of Salmostoma bacaila – including sex ratio, length-frequency distributions (LFDs), size at sexual maturity, spawning season, length-weight relationships (LWRs) and condition factor – were studied. Samples were collected seasonally during June 2017 to May 2018 from a tributary of the Payra River. The overall sex ratio was significantly different from the expected value of 1:1 (p < 0.001), in favour of male specimens. Females were significantly larger than males. Size at sexual maturity was estimated at 7.6~7.7 cm total length. Seasonal variations in the gonadosomatic index (GSI) indicate that the main spawning season is from spring to summer. The LWRs showed negative allometric growth in both sexes, but with clear seasonal variation. Fulton’s condition factor varied in both sexes and was attributed to variations in GSI with maturity. The fin¬dings of this study will be helpful for management and conservation of S. bacaila populations.

Chamelea gallina reproductive biology and Minimum Conservation Reference Size: implications for fishery management in the Adriatic Sea

BMC Zoology ◽  
2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Giada Bargione ◽  
Fortunata Donato ◽  
Giulio Barone ◽  
Massimo Virgili ◽  
Pierluigi Penna ◽  
...  
Keyword(s):  
Sexual Maturity ◽  
Adriatic Sea ◽  
Seawater Temperature ◽  
Reproductive Capacity ◽  
Great Effort ◽  
Important Species ◽  
Spawning Period ◽  
The Past ◽  
Chamelea Gallina ◽  
Size At Sexual Maturity

Abstract Background The striped venus clam Chamelea gallina is an economically important species in Adriatic Sea fisheries. The use of hydraulic dredging for its catch has a long history in Italy and its management faced several stages of development in the last 40 years. A great effort has been made in the past two decades to move from poorly or weakly managed fisheries to a well-structured co-management system to improve the sustainability of this fishery. However, a prerequisite for appropriate resource management is a sound knowledge of the biology and reproductive strategy of the species. Results We investigated three major biological features– the gametogenic cycle, size at sexual maturity and partial fecundity – by microscopic, histological and video analysis techniques. We demonstrated that its breeding season is driven by rises in seawater temperature and chlorophyll-a concentration and that its spawning period lasted from March to September. Size at sexual maturity was reached very early in the life cycle. As regards partial fecundity – the number of mature oocytes potentially released by females with ripe gonads in a single release event – varied in relation to size. Nevertheless, the reduction on the Minimum Conservation Reference Size (MCRS) from 25 to 22 mm (Delegated Regulation (EU) 2020/2237) lead to a 40% reduction in the number of emitted eggs. Conclusions We suggest that the ability of Adriatic clam stocks to withstand the strong fishing pressure of the past 40 years and the present one is due to their high reproductive potential and multiple spawning events combined with the effect of management measures (closed areas/seasons, quota, MCRS) and technical constraints on the gear and the sieve on board. Moreover, since the reduced MCRS for Venus shells is still larger than the size at maturity, it will probably not be detrimental to the reproductive capacity of the stock.

Body Size and the Timing of Sexual Maturity

2017 ◽  
pp. 341-374
Author(s):  
Kim Hill ◽  
A. Magdalena Hurtado
Keyword(s):  
Body Size ◽  
Sexual Maturity

Range extension of the Bengal monitor (Varanus bengalensis) for the Trans-Himalayan Region with an altitude record for monitor lizards

Zootaxa ◽  
2020 ◽  
Vol 4732 (2) ◽  
pp. 337-340
Author(s):  
ASHUTOSH SINGH ◽  
BHUPINDER SINGH RANA ◽  
MUKESH THAKUR ◽  
BASUDEV TRIPATHY ◽  
LALIT KUMAR SHARMA ◽  
...  
Keyword(s):  
Body Size ◽  
Indian Subcontinent ◽  
Distinct Pattern ◽  
Wildlife Protection ◽  
Western Asia ◽  
Monitor Lizard ◽  
Different Types ◽  
Freshwater Habitats ◽  
Desert Areas ◽  
Monitor Lizards

The Bengal monitor lizard or Common Indian monitor lizard (Varanus bengalensis Daudin, 1802) is classified as Least Concern under the IUCN and listed under the Schedule-I of the Indian Wildlife Protection Act 1972. Further, the trade of the species is prohibited as the species is listed in Appendix I of CITES. It is widely distributed over Western Asia, the Indian Subcontinent, and Southeast Asia (Koch et al. 2013). It is reported to occupy both terrestrial as well as freshwater habitats from desert areas to floodplains, scrubland to forests, in different types of terrains at elevations below 1500m (Auffenberg 1994; Papenfuss et al. 2010). Body size of individuals varies from 61 to 175 cm from the tip of the snout to the end of the tail (Auffenberg 1994; Losos and Greene, 1998). Adults are generally grey or greenish-grey in color, with a ventral pattern of grey to black crossbars from the chin to the tail. Adult individuals are less contrasting and have a less distinct pattern than younger individuals. The species shows a sexual dimorphism, with males being heavier (around 7.18 to 10 kg) than females which are about 40% smaller in size (Papenfuss et al. 2010). 

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