scholarly journals Population structure of Macrobrachium amazonicum (Heller, 1862) (Decapoda: Palaemonidae) in Miranda Hydroelectric Plant Reservoir, Araguari river, Minas Gerais, Brazil

2019 ◽  
Vol 31 ◽  
Author(s):  
Raquel Costa e Silva ◽  
Marina Calixto Cunha ◽  
Emerson Contreira Mossolin ◽  
Giuliano Buzá Jacobucci
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Carapace Length ◽  
Hydroelectric Plant ◽  
Size Variation ◽  
Minas Gerais ◽  
Size Class ◽  
Size Frequency Distribution ◽  
Reproduction Strategy ◽  
Continuous Reproduction

Abstract Aim The present study aimed to analyze a M. amazonicum population structure in a reservoir of the “Triângulo Mineiro”, Brazil. Methods Monthly surveys were carried out from April/2012 to May/2013 at the Miranda Hydroelectric Plant Reservoir located in Araguari river, state of Minas Gerais. A sampling section of 100 m long, 5 m wide and depth not exceeding 1 m was defined on the banks of the reservoir. Sampling consisted on two persons quickly passing a 2 mm sieves in partially submerged marginal vegetation, for one hour. The sampled specimens were identified, sexed and measured. Results A total of 2,584 specimens were analyzed, of which 64.62% were females (3.93% ovigerous, 5.94% non-ovigerous and 54.75% juveniles), 29.16% males (21.41% adults and 7.76% juveniles) and 6.22% juveniles of undetermined sex. The sex ratio (1:2.21) indicated a clear deviation for females, for the whole sampling period, monthly and for each size class. Males had an average carapace length (CL = 4.50 ± 0.71 mm) significantly lower than females (CL = 4.64 ± 1.47 mm) and the size frequency distribution revealed a unimodal pattern, with peaks occurring in 4.0 - 4.9 mm size class for males and in 3.0 - 3.9 mm size class for females. The relation between total and carapace length was significant, indicating a negative allometric growth. No males’ morphotypes were found. The population presented a continuous reproduction with a gradual increase between April and June/2012. Female sexual maturity was determined for 6.3 mm of CL, while for males was estimated for 4.0 mm. Conclusion The Miranda reservoir population had a body size variation similar to the continental populations of Pantanal. The sexual dimorphism observed may be related to the absence of male morphotypes and to the “pure search” reproduction strategy. The deviated sex ratio for females may increase the chance of fertilization and the reproductive success. The presence of juveniles and ovigerous females throughout the year indicates a continuous reproduction pattern of the population.

Population structure of Emys orbicularis in the Bardello (Po Delta, Northern Italy)

1995 ◽  
Vol 16 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Stefano Mazzotti
Keyword(s):  
Population Structure ◽  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Population Size ◽  
Carapace Length ◽  
Shell Height ◽  
Northern Italy ◽  
Emys Orbicularis ◽  
Frequency Distributions ◽  
Po Delta

AbstractA population of Emys orbicularis in the Bardello (Po Delta, Northern Italy) was studied for 3 years using capture-mark-recapture methods, 23.6% of which were male, 57,5% female and 18.9% were juvenile specimens. The sex ratio of 127 specimens was 1:2. Certain morphometric variables such as the carapace length and shell height were examined in order to establish their sexual dimorphism. The population structure was defined by means of frequency distributions of carapace length. Using the Lincoln-Petersen and Jolly-Seber indices it was possible to estimate the population size as an average of 7.2 specimens per hectare.

scholarly journals Population structure and growth of the hermit crab Pagurus brevidactylus (Anomura: Paguridae) from the northern coast of São Paulo, Brazil

2005 ◽  
Vol 85 (1) ◽  
pp. 127-128 ◽  
Author(s):  
F.L. Mantelatto ◽  
R.A. Christofoletti ◽  
W.C. Valenti
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Hermit Crab ◽  
Sexual Maturity ◽  
Scuba Diving ◽  
Northern Coast ◽  
Short Life ◽  
Continuous Reproduction ◽  
Shield Length ◽  
Number Of Males

The hermit crab Pagurus brevidactylus (Crustacea: Anomura: Paguridea) from the infralittoral area of Anchieta Island, Ubatuba, was characterized by population structure (size, sex ratio, reproduction and recruitment) and growth. Animals were collected monthly during 1999 by SCUBA diving. A total of 1525 individuals was collected (633 males and 892 females), 695 of them were ovigerous females. Overall sex ratio was 0·7:1 in favour of females. The crabs showed a unimodal distribution with males significantly larger than females. Ovigerous females were collected during all months and in high percentages from 1·0 mm of shield length, demonstrating intense and continuous reproduction. The longevity was approximately 24 months for males and 18 for females, which showed larger growth rate and reached sexual maturity earlier (two months) than males. The low number of males in this population may be due to the longer life span. Moreover, the sexual dimorphism favours males during the intra- and interspecific fights by shell, food, reproduction and territory. Females demonstrated a short life cycle and intense reproduction.

Population structure, fecundity and embryo loss of the sea grass shrimp Latreutes pymoeus (Decapoda: Hippolytidae) at Inhaca Island, Mozambique

2007 ◽  
Vol 87 (4) ◽  
pp. 879-884 ◽  
Author(s):  
Gil Penha-Lopes ◽  
Paulo Torres ◽  
Adriano Macia ◽  
José Paula
Keyword(s):  
Population Structure ◽  
Brood Size ◽  
Carapace Length ◽  
Grass Shrimp ◽  
Stage Iv ◽  
Development Stage ◽  
Size Class ◽  
Morphometric Measurements ◽  
Sea Grass ◽  
Males And Females

Latreutes pymoeus is a poorly studied tropical and sub-tropical shrimp species that mainly lives on sea grass beds. Samples were collected from sea grass beds of Inhaca Island, Mozambique, during August 2005 at neap/spring and low/high tides. Specimens were identified, sexed, counted and morphometric measurements were made. Ovigerous females were classified as small (carapace length (CL): 2.7–3.2 mm), medium (CL: 3.3–3.8 mm) and large (CL: 3.9–4.4 mm). Embryo masses were carefully removed from the pleopods with forceps, eggs staged and counted. On average, about 20% more males were found than females (0.64 ±0.25 and 0.56 ±0.28 ind m-2, respectively), but males were significantly smaller (2.25 ±0.32 and 2.60 ±0.47 mm CL for males and females, respectively). At 3.1 mm CL at least 50% of the females found carried embryos in the pleopods. Average (±SD) brood size increased significantly with female length (76 ±18, 133 ±64 and 205 ±61, for small, medium and large ovigerous females). The number of embryos decreased significantly over the incubation period for each size-class of the shrimp. Brood loss from embryonic Stage I to Stage IV for small, medium and large shrimp were 19.8%, 36.5% and 41.8%, respectively. Although an increase in brood loss was observed with increasing shrimp size, senescence did not seem to occur since larger shrimps carried a higher number of embryos and negative allometry was not recorded. Mean embryo volume, in the same development stage, was not significantly different among the small, medium and large shrimp, increasing significantly from 0.014 mm3 to 0.029 mm3 from the first to last embryonic stages.

Population structure and reproduction of the seagrass shrimp Hippolyte zostericola (Decapoda: Hippolytidae) at Laguna de Términos, Campeche, Mexico

2012 ◽  
Vol 93 (3) ◽  
pp. 675-682
Author(s):  
J. Romero-Rodríguez ◽  
R. Román-Contreras
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Carapace Length ◽  
Female Size ◽  
Size At Maturity ◽  
Seagrass Meadows ◽  
The Mean ◽  
Laguna De Terminos ◽  
The Relationship ◽  
Internal Margin

The aim of this paper is to describe the population structure and some reproductive aspects of Hippolyte zostericola during an annual cycle. Samples were taken bimonthly, from June 2009 to April 2010, with a Colman–Seagrove sledge net on seagrass meadows located in the internal margin of Isla del Carmen, Campeche, Mexico. The population structure of H. zostericola was similar throughout the cycle analysed. The males, significantly smaller than females (0.57–1.8 and 0.55–3.52 mm carapace length (CL), respectively), were more frequent between 0.8 and 1.54 mm CL, whereas in larger size-classes (1.8–3.52 mm CL) only females were registered, ovigerous principally. The sex-ratio was always in favour of males, mean of 1.3 males per female. Size at maturity (CL50) was 2.28 ± 0.1 mm CL. Based on the presence of ovigerous females throughout the year it is considered that the reproduction of H. zostericola is continuous. The main breeding season and recruitment occurs during the first third of the year. The mean fecundity of the species was 144 ± 69 eggs and varies with female size. The higher egg loss occurred in larger females (37.3%) and the relationship between fecundity and female size was estimated as negative allometric, which suggests that age influences the fecundity of the species.

scholarly journals Abundance and population structure of Plesionika narval (Fabricius, 1787) in the Northeastern Atlantic

2019 ◽  
Vol 79 (1) ◽  
pp. 111-119 ◽  
Author(s):  
R. Sousa ◽  
M. R. Pinho ◽  
J. Delgado ◽  
A. R. Pinto ◽  
M. Biscoito ◽  
...  
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Carapace Length ◽  
Late Summer ◽  
Shallow Waters ◽  
Female Size ◽  
Depth Range ◽  
Madeira Archipelago ◽  
Seasonal Migrations ◽  
Northeastern Atlantic

Abstract Analysis of abundance and population structure of Plesionika narval was performed on data concerning 5,255 specimens obtained from 62 fishing sets carried out off the Madeira archipelago (Northeastern Atlantic) between 2004 and 2008 in a depth range from 101 to 350 m. Abundance ranged from 0.01 to 19.74 specimens-per-trap and significant differences were found between seasons, probably as a result of an increment of population in the spring during the recruitment season. The analysis of size distribution revealed that the carapace length (CL) ranged from 2.45 to 28.61 mm and that mean female size consistently exceeded that of males. Differences in mean CL were statistically significant between depth strata and seasons. Of the specimens sampled, 57.00% were males, 41.88% females and 1.42% undetermined. Sex ratio also differed significantly between seasons according to depth strata, consolidating the hypothesis of the existence of seasonal migrations related with the reproductive cycle of this species. Ovigerous females showed larger sizes and occurred all year around and remain in shallow waters in winter, summer and autumn and move to deeper waters in spring. The highest frequency of ovigerous females was recorded in summer, between 151 and 200 m deep supporting the hypothesis that spawning of this species occurs in shallow waters, especially in late summer.

Annual cycle of growth and population structure of the estuarine crab Hemigrapsus crenulatus (Brachyura: Varunidae) off central Chile

2021 ◽  
pp. 1-15
Author(s):  
Ramiro A. Riquelme-Bugueño ◽  
Tomás Luppi ◽  
Gonzalo S. Saldías ◽  
Marcelo E. Lagos ◽  
Mauricio A. Urbina ◽  
...  
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Size Distribution ◽  
Annual Cycle ◽  
Linear Models ◽  
Environmental Variability ◽  
Growth Parameters ◽  
Austral Summer ◽  
Size Frequency Distribution ◽  
Central Chile

Abstract Estuaries and saltmarshes play a fundamental role in the life cycle of many crab species. Diverse studies show that temperature and salinity modulate abundance, size frequency distribution (SFD), sex ratio and growth in crustaceans. These population parameters are usually challenging to estimate due to the high environmental variability of estuaries. Monthly samples of the estuarine crab Hemigrapsus crenulatus were taken from October 2003 to October 2004 (except July 2004) in the Tubul estuary, central Chile. We quantified temporal changes in abundance, size distribution, sex ratio and monthly growth through the annual cycle. A total of 1025 individuals were collected. Sizes ranged from 7.72–33.51 mm carapace length (CL) with a growth rate ranging between 2.13–30.5% mm CL mo−1. Size and growth rates were greater in spring-summer, suggesting a faster growth of younger crabs correlated with increasing sea temperatures in the austral summer. Overall, sex ratio was 1.75:1 in favour of males. Modal analysis identified at least seven cohorts cohabiting throughout the annual cycle. Growth parameters for males and females were the following, respectively: L∞ = 33.6 and 29.6, k = 0.69 and 0.91, t0 = –0.39 and −0.28. Changes in size distribution suggested a recruitment period during autumn and winter seasons when there are lower salinities and temperature fluctuations stresses. Generalized linear models indicated that sea temperature, salinity and chlorophyll were the environmental variables that better predicted the annual patterns in the population structure.

scholarly journals Population structure of the deep sea hermit-crab Catapaguroides microps (Paguroidea, Anomura) in the Campos Basin, RJ, Brazil

2010 ◽  
Vol 58 (spe4) ◽  
pp. 19-23
Author(s):  
Luana S. F. Lins ◽  
Tarso Costa
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Deep Sea ◽  
Size Class ◽  
Hermit Crabs ◽  
Size Class Distribution ◽  
The North ◽  
Deep Waters ◽  
Campos Basin

The population of Catapaguroides microps A. Milne-Edwards and Bouvier, 1892 in the Campos Basin was studied with an emphasis on its composition in the Northern and Southern parts of the Basin, the different gender sizes, sex ratio, and size class distribution. Specimens were collected under the "Program for the Environmental Characterization of the deep waters of the Campos Basin" ("Programa de Caracterização Ambiental das Águas Profundas da Bacia de Campos") in February and August 2003. A total of 339 hermit crabs were analyzed. Individual abundance was higher in the North. C. microps shows sexual dimorphism for body size, the males being larger than the females. The sex ratio is skewed in the female's favor (1:0.7), as shown by previous studies on shallow-water populations.

Modulating reproduction of Penaeidae shrimps: ecological responses of two sympatric species (Decapoda: Dendrobranchiata) on south-eastern Brazilian coast

2012 ◽  
Vol 93 (3) ◽  
pp. 733-740 ◽  
Author(s):  
Ana Paula Pereira Gomes ◽  
Karina Annes Keunecke ◽  
Demarques Ribeiro da Silva ◽  
Marcelo Vianna
Keyword(s):  
Sex Ratio ◽  
Carapace Length ◽  
Sympatric Species ◽  
Brazilian Coast ◽  
Guanabara Bay ◽  
Pink Shrimp ◽  
South Eastern ◽  
Eastern Brazil ◽  
Farfantepenaeus Paulensis ◽  
Continuous Reproduction

The present study investigated the reproductive biology of the pink shrimp Farfantepenaeus brasiliensis and Farfantepenaeus paulensis captured offshore and at two important fishing grounds, Guanabara Bay and Araruama Lagoon both on the south-eastern Brazil coast. The females’ size at first maturation was 37.90 mm of carapace length (CL) for F. brasiliensis and 41.95 mm of CL for F. paulensis. Both species presented continuous reproduction with two spawning peaks. For F. brasiliensis these peaks occurred during summer and winter and for F. paulensis during summer and autumn. The sex-ratio of the pink shrimp was favourable to the number of females which can be a strategy to guarantee the reproduction.

scholarly journals A Quantitative Genetic Analysis of Nuclear-Cytoplasmic Male Sterility in Structured Populations of Silene vulgaris

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 833-841 ◽  
Author(s):  
Douglas R Taylor ◽  
Matthew S Olson ◽  
David E McCauley
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Genetic Analysis ◽  
Cytoplasmic Male Sterility ◽  
Male Sterility ◽  
Sex Expression ◽  
Silene Vulgaris ◽  
Population Variance ◽  
Quantitative Genetic ◽  
Quantitative Genetic Analysis

Abstract Gynodioecy, the coexistence of functionally female and hermaphroditic morphs within plant populations, often has a complicated genetic basis involving several cytoplasmic male-sterility factors and nuclear restorers. This complexity has made it difficult to study the genetics and evolution of gynodioecy in natural populations. We use a quantitative genetic analysis of crosses within and among populations of Silene vulgaris to partition genetic variance for sex expression into nuclear and cytoplasmic components. We also use mitochondrial markers to determine whether cytoplasmic effects on sex expression can be traced to mitochondrial variance. Cytoplasmic variation and epistatic interactions between nuclear and cytoplasmic loci accounted for a significant portion of the variation in sex expression among the crosses. Source population also accounted for a significant portion of the sex ratio variation. Crosses among populations greatly enhanced the dam (cytoplasmic) effect, indicating that most among-population variance was at cytoplasmic loci. This is supported by the large among-population variance in the frequency of mitochondrial haplotypes, which also accounted for a significant portion of the sex ratio variance in our data. We discuss the similarities between the population structure we observed at loci that influence sex expression and previous work on putatively neutral loci, as well as the implications this has for what mechanisms may create and maintain population structure at loci that are influenced by natural selection.

Sign in / Sign up

Export Citation Format

Share Document