Masculinized females in a population of Leptodiaptomus minutus (Copepoda, Calanoida)

1998 ◽  
Vol 76 (3) ◽  
pp. 596-600 ◽  
Author(s):  
Kristine B Sillett ◽  
Richard S Stemberger
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Adult Males ◽  
Secondary Sexual Characteristics ◽  
Adult Females ◽  
Internal Morphology ◽  
Sexual Characteristics ◽  
The Common ◽  
Normal Males ◽  
Normal Adults

In a population of the common freshwater copepod Leptodiaptomus minutus Lilljeborg, 7.3% of adult females exhibited male secondary sexual characteristics. Although these masculinized or intersex females had the internal morphology of normal females, they possessed one or rarely two normal geniculate male antennules, and in a few instances male fifth legs. The sex ratio of normal adult males to females in the population was 1:1. No differences in body size among normal males, normal females, and masculinized females were found. Antennule lengths of males and masculinized females were not significantly different from one another; however, normal females had longer antennules than either males or masculinized females. Mating experiments indicated that masculinized females were functionally female and they were able to mate with normal males to produce offspring that were normal or masculinized. The occurrence of intersex copepods in lakes of North America may be more widespread than we now recognize because they can be easily overlooked or mistaken for normal adults.

The effects of phthalate and nonylphenol exposure on body size and secondary sexual characteristics during puberty

2015 ◽  
Vol 218 (7) ◽  
pp. 603-615 ◽  
Author(s):  
Jia-Woei Hou ◽  
Ching-Ling Lin ◽  
Yen-An Tsai ◽  
Chia-Huang Chang ◽  
Kai-Wei Liao ◽  
...  
Keyword(s):  
Body Size ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Secondary Sexual

The Hidden Costs of Sociality: Intra-Group Variation in Feeding Strategies in Sumatran Long-Tailed Macaques (Macaca Fascicularis)

Behaviour ◽  
1986 ◽  
Vol 99 (3-4) ◽  
pp. 296-314 ◽  
Author(s):  
Maria A. VAN NOORDWIJK ◽  
Carel P. VAN SCHAIK
Keyword(s):  
Body Size ◽  
Travel Time ◽  
Macaca Fascicularis ◽  
Fruit Trees ◽  
Feeding Competition ◽  
Feeding Strategies ◽  
Adult Males ◽  
Adult Females ◽  
Hidden Cost ◽  
Group Variation

AbstractGroups of long-tailed macaques (Macaca fascicularis) are often fissioned into a large main party and one or more small parties. We studied the size and composition of the main party in relation to fruit supply and the ecology of the various age-sex categories in order to establish the cause of this fissioning. The size of the main party varied not only because the size of available fruit trees varied but also because the various age-sex categories were so different in their feeding strategies that they sometimes went separate ways. Our observations suggest that body size and sex profoundly affected food requirements and the risks attached to leaving the main party. We concluded that adult females left the main party mainly to escape from feeding competition and attempted to reduce travel time when they had infants so as to minimise the costs of carrying infants. Males, by contrast, left above all because of their different food requirements; subadult males left to eat more fruit than the others, adult males mainly to eat bigger fruit than the others. This intra-group variation in feeding strategies constitutes a usually hidden cost to sociality.

scholarly journals Brood Sex Ratios are Related to Male Size but not to Attractiveness in Common Yellowthroats (Geothlypis Trichas)

The Auk ◽  
2007 ◽  
Vol 124 (1) ◽  
pp. 176-184 ◽  
Author(s):  
Betsy Abroe ◽  
Julia C. Garvin ◽  
Marc C. Pedersen ◽  
Linda A. Whittingham ◽  
Peter O. Dunn
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Reproductive Value ◽  
Male Body ◽  
Male Size ◽  
Common Yellowthroat ◽  
Geothlypis Trichas ◽  
The Common ◽  
Fitness Benefits ◽  
Male Ornament

Abstract When the reproductive value of sons differs from that of daughters, selection will favor broods biased toward the sex that can provide greater fitness benefits. In species where female choice is based on male ornamentation, females mated to highly ornamented males may experience a reproductive advantage by skewing the brood sex ratio toward sons. In the Common Yellowthroat (Geothlypis trichas), males with larger black facial masks are more likely to gain a social mate and sire extrapair young and, as a result, have increased seasonal reproductive success. Females mated to larger-masked males could benefit if they produced more sons. Given that larger- masked males are preferred as extrapair sires, females may also benefit by producing more extrapair sons. We tested these hypotheses during a five-year study of Common Yellowthroats in Wisconsin. Contrary to our predictions, females did not produce more sons when mated to males with larger masks, and extrapair young were not more likely to be male. However, sons were more likely to be sired by males with longer tarsi, which suggests that females may respond to male body size rather than to male ornament size. El Cociente de Sexos en las Nidadas Está Relacionado con el Tamaño de los Machos pero no con el Atractivo en Geothlypis trichas

A new species of the Pristimantis orestes group (Amphibia: Strabomantidae) from the high Andes of Ecuador, Reserva Mazar

Zootaxa ◽  
2013 ◽  
Vol 3616 (4) ◽  
pp. 345-356 ◽  
Author(s):  
JUAN M. GUAYASAMIN ◽  
ALEJANDRO F. ARTEAGA
Keyword(s):  
New Species ◽  
Body Size ◽  
Molecular Phylogeny ◽  
Mitochondrial Gene ◽  
Small Body ◽  
Dominant Frequency ◽  
Small Body Size ◽  
Adult Males ◽  
Adult Females ◽  
A New Species

We describe a new Pristimantis from La Libertad and Rumiloma, Reserva Mazar, Andes of Southeastern Ecuador, at elevations between 2895–3415 m. This species is assigned to the P. orestes group, from whose members it differs by its small body size (adult males ≤ 18.1 mm; adult females ≤ 23.7 mm), usually reticulated ventral pattern, and visible tympanum. The vocalization of the new species consists of a series of calls; each call is composed by a pulsed, non-modulated note in frequency, and with a dominant frequency of 3122–3171 Hz. A molecular phylogeny based on a fragment of the mitochondrial gene 12S shows that the new species is sister to Pristimantis simonbolivari.

scholarly journals Morphometric differentiation and sexual dimorphism in Limnomedusa macroglossa (Duméril & Bibron, 1841) (Anura: Alsodidae) from Uruguay

2021 ◽  
Vol 16 (1) ◽  
pp. 11-25
Author(s):  
Valeria De Olivera-López ◽  
Arley Camargo ◽  
Raúl Maneyro
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Phenotypic Plasticity ◽  
Life History Strategies ◽  
Clinal Variation ◽  
Size And Shape ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Morphological Differences

Intersexual morphological differences within a species occur in many traits, including body size and shape. Many processes that cause geographic variability in morphology have been proposed: population structure, phenotypic plasticity (environmental effects on development), and natural and/or sexual selection. Several hypotheses can explain patterns of sexual dimorphism in anurans, including natural or intra/inter-sexual selection, and differences in life history strategies between sexes. Limnomedusa macroglossa is considered a habitat specialist restricted to rocky outcrops in Brazil, Argentina, Paraguay, and Uruguay. We evaluated the extent of sexual (size and shape) dimorphism in L. macroglossa from Uruguay based on morphometrics and secondary sexual characteristics, while taking into account geographic variation. Sexual dimorphism in body size of adults was found, but multivariate analyses did not demonstrate the existence of significant differences in shape. There were also significant differences in body size and hind leg measurements among six hydrographic basins as a result from the phenotypic plasticity correlated with local temperature, representing a clinal variation along the latitudinal gradient of Uruguay. The sexual dimorphism found in body size is probably the consequence of higher growth rates and/or late sexual maturity in females, which favors larger body size for accommodating larger ovaries, and thus, higher reproductive output. 

Blackbuck Antilope cervicapra (Mammalia: Cetartiodactyla: Bovidae) estimates in human-dominated landscape in Aligarh, Uttar Pradesh, India

2021 ◽  
Vol 13 (9) ◽  
pp. 19232-19238
Author(s):  
Mujahid Ahamad ◽  
Jamal A. Khan ◽  
Satish Kumar
Keyword(s):  
Sex Ratio ◽  
Uttar Pradesh ◽  
Adult Males ◽  
Forest Patches ◽  
Female Ratio ◽  
Adult Females ◽  
Or Groups ◽  
Feral Dogs ◽  
The Status ◽  
Antilope Cervicapra

Information on the status of the Indian Blackbuck Antilope cervicapra is mostly available from protected areas (PA), although 80% of its population occurs outside PAs. We conducted surveys to assess the status, age structure, sex ratio, and conservation issues of Blackbuck in and around Aligarh between February and June 2014. A median of 672 individuals at 18 separate locations were recorded with a group size ranging 4–216 except for solitary individuals. The abundance of Blackbuck was maximum in Sikandra Rao (range: 154–216) followed by Andla (range: 47–65), and Pala-Sallu (range: 53–62). Sex ratio was skewed towards females (1:4.5) with yearling to female and fawn to female ratio of 7.8:100 and 6.7:100, respectively. The percentage of adult males of Blackbuck (12.8% adult males, 8.4% sub-adult males) as well as adult females (56.4% adult females, 11.9% sub-adult females) was higher than other age classes or groups in the population. The preliminary observations indicate that the increasing population of free-ranging feral dogs, degradation of forest patches, social forestry plantations, competition with livestock, and poaching pressure are the major conservation issues of Blackbuck in the area. The current information is expected to serve as baseline in assessing the population of Blackbuck in the future. 

scholarly journals Home range of the Tropidurid lizard Liolaemus lutzae: sexual and body size differences

1999 ◽  
Vol 59 (1) ◽  
pp. 125-130 ◽  
Author(s):  
C. F. D. ROCHA
Keyword(s):  
Body Size ◽  
Home Range ◽  
Mutual Exclusion ◽  
Home Range Size ◽  
Range Size ◽  
Home Ranges ◽  
Adult Males ◽  
Adult Females ◽  
The Mean ◽  
Janeiro State

The home range of the Tropidurid lizard Liolaemus lutzae, an endemic species of the costal sand dune habitats of Rio de Janeiro State, was studied in the beach habitat of Barra de Maricá restinga, Maricá County. Home ranges were studied using a mark-recapture technique in a delimited area at the beach habitat. I considered for estimates and analysis the home ranges of those lizards with a minimum of four positions. The size of L. lutzae home ranges varied according to the segment of the population. The mean home range size of adult males (x = 59.8 ± 33.7 m²) was significantly larger than that of adult females (x = 22.3 ± 16.1 m²). Juvenile mean home range size was significantly smaller than that of adult males, but did not differ from that of adult females (t = 1.058; p = 0.149). The overlap between male home ranges was usually low (3.6%), being in general only peripheral. Conversely, there was a considerable overlap between home ranges of adult females with those of adult males, the home range areas of two or three females being enclosed in the home range of one adult male. The small overlap between home ranges of adult males suggested mutual exclusion. The observed between-sex differences in the size of L. lutzae home range may be explained by the sexual dimorphism in body size in this species, and by the need of adult males to establish larger areas so as to include many females in their areas, during the reproductive season. The differences in home range along ontogeny probably result from differences in body size of the different segments of the population, due to trophic differences (carnivory and herbivory levels), and the dispersal of young after birth. Because L. lutzae is omnivorous, but primarily herbivorous when adult, and due to its sit-and-wait foraging behavior (mainly on arthropods), it does not need to move around over large areas to find food, which in turn reduces the area necessary for it to live.

scholarly journals Microhabitat preferences of the freshwater prawn Macrobrachium jelskii (Decapoda: Palaemonidae)

2019 ◽  
Vol 109 ◽  
Author(s):  
Jersei N. Silva ◽  
Guilherme de Oliveira ◽  
Sérgio S. da Rocha
Keyword(s):  
Sex Ratio ◽  
Water Reservoir ◽  
Habitat Choice ◽  
Freshwater Prawn ◽  
Adult Males ◽  
Adult Females ◽  
Males And Females ◽  
Microhabitat Preferences ◽  
Lower Depth ◽  
Juvenile Males

ABSTRACT We analyzed the microhabitat preferences of Macrobrachium jelskii (Miers, 1877) males and females inhabiting an urban water reservoir in Cruz das Almas, Bahia, Brazil. Prawns were collected monthly, from March 2015 to February 2016, in three microhabitats, using a sieve. Each microhabitat was dominated by one macrophyte species: Eleocharis sp. (M1), Cabomba sp. (M2), and Nymphaea sp. (M3). The prawns were measured (carapace length), and categorized as juvenile males, adult males, juvenile females, non-ovigerous adult females and ovigerous adult females. An analysis of variance (ANOVA) was used to compare the number and size of individuals. The sex ratio and frequency of ovigerous females in the three microhabitats were also calculated. The sex ratio was biased towards females in M1 and did not deviate from 1:1 in M2 and M3. When prawns were separated into five categories we observed that non-ovigerous adult females were more abundant in M1, while adult males were the most abundant demographic category in M2 and M3. Juveniles of both sexes and ovigerous females showed no microhabitat preference, although M1 and M2 appeared to be more suitable for the latter. Adult females were the largest individuals in all microhabitats. Food availability, lower depth and lower predation pressure in M1 are the main factors that make M1 more suitable for M. jelskii, particularly non-ovigerous adult females and larger adult males. Intraspecific competition for shelter in M1 might also occur and adult females win this competition due to their larger body size. Therefore, adult males are found in higher abundance in M2 and M3 and the juvenile of both sexes spread evenly across all microhabitats. Our results help to understand the ecological role and the niche used by M. jelskii. Future studies on the habitat choice and predation under laboratory conditions should help to understand the behavior of this species.

On the mating system of polar bears

1986 ◽  
Vol 64 (10) ◽  
pp. 2142-2151 ◽  
Author(s):  
Malcolm A. Ramsay ◽  
Ian Stirling
Keyword(s):  
Sex Ratio ◽  
Sea Ice ◽  
Mating System ◽  
Breeding Season ◽  
Large Body ◽  
Arctic Sea Ice ◽  
Polar Bears ◽  
Adult Males ◽  
Terrestrial Mammals ◽  
Adult Females

Polar bears are intimately associated with arctic sea ice and their distribution is approximated by its winter extent. They are the only terrestrial mammals, other than humans, to have adapted so completely to sea ice, a quite different habitat, spatially and temporally, from that occupied by other terrestrial mammals. We propose that the dynamics of sea ice and the associated variability in access to food have played a major role in the evolution of the social structure and mating system of polar bears. Adult females and males move to areas of the sea ice where the greatest success in hunting is realized. Such regions are unpredictable in location, however, both seasonally and annually. Because female distributions are unpredictable, adult males are unable to defend stable territories that will encompass the home ranges of one or more females and may instead distribute themselves among different sea-ice habitats at the same relative densities as solitary adult females. Females keep nursing cubs with them for more than 1 year; hence the mean interbirth interval is 2 or more years. This results in a functionally skewed sex ratio, with fewer females available to breed in any one year than males, and in intrasexual competition among males for access to breeding females. Consequently, established dominance hierarchies among males are unstable, and wounding, scarring, and breakage of canine teeth are common; these are evidence of direct physical confrontations during the breeding season. Large body size is advantageous in these fights and this has resulted in one of the highest degrees of sexual dimorphism among terrestrial mammals. Because of the funtionally skewed sex ratio and the shifting distribution of both females and males, however, even the largest male probably cannot be certain of locating a larger than average number of receptive females in any one breeding season.

Changes in Proximate Composition of the Crayfish Orconectes propinquus with Size, Sex, and Life Stage

1976 ◽  
Vol 33 (11) ◽  
pp. 2450-2458 ◽  
Author(s):  
Roy A. Stein ◽  
Michael L. Murphy
Keyword(s):  
Proximate Composition ◽  
Carapace Length ◽  
Inorganic Material ◽  
Life Stage ◽  
Dry Weight ◽  
Adult Males ◽  
Mineral Salts ◽  
Orconectes Propinquus ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics

We estimated percent water, inorganic material, and chitin for the crayfish Orconectes propinquus. To properly account for organic materials and mineral salts, we burned samples first at 550 C then at 650 C for estimates of the inorganic fraction. More precise estimates were obtained at 650 C; thus, to account for the conversion of CaCO3 to CaO and CO2 at 650 C, inorganic estimates were multiplied by an empirically derived factor (1.5) to convert all values to total inorganic material. For chitin, acid decalcification, followed by deproteinization with base and combustion at 650 C, provided best estimates. Proximate composition varied with size, sex, and molt stage. Percent water was inversely related to size for juveniles but was constant with size in adult males (68.4%) and females (67.4%). Percent inorganic material and chitin of dry weight increased with size in juveniles; inorganic continued to increase with size following maturity while percent chitin remained constant. For a carapace length of 25 mm, adult males had significantly more inorganic material (46.2 vs. 38.1%) and chitin (16.3 vs. 14.1%) than adult females. Differences in proximate composition appeared related to secondary sexual characteristics, with males having longer, wider chelae but narrower abdomens than females. Recent molts had more water (84.1%) and less inorganic (19.0%) and chitin (9.1%) than either male or female intermolts. Understanding how these proximates vary with life stage is necessary for adequately describing transfer of energy and biomass between populations.

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