Larvae of female Caecognathia sp. (Isopoda: Gnathiidae) are attracted to male adults and prolong their larval phase in the absence of males

2019 ◽  
Vol 40 (2) ◽  
pp. 156-161
Author(s):  
Chiaki Hayashi ◽  
Katsuhiko Tanaka ◽  
Euichi Hirose
Keyword(s):  
Sex Ratio ◽  
Adult Female ◽  
Light Trap ◽  
Experimental Chamber ◽  
Adult Males ◽  
Larval Phase ◽  
The Third ◽  
Third Stage ◽  
Males And Females ◽  
Induction Of Metamorphosis

Abstract The interaction between males and females (adults and/or larvae) of Caecognathia sp., a parasite of fishes, was studied in the laboratory to investigate the attraction of the opposite sexes and the induction of metamorphosis to adults. We reared the third-stage larvae collected by a light trap to develop them into adults. Their sex ratio was 104 males to 100 females, suggesting that females and males have similar fitness. The attraction experiments using an experimental chamber demonstrate that adult males attract female larvae that were also attracted by the dichloromethane extract of males but not the female extract. The males also induce the praniza females to develop into adults. When there are no males present, females can prolong the larval phase and moreover can spontaneously start to develop into adults after the prolonged larval phase. As in other isopods, the gnathiid female is supposed to be able to copulate immediately after metamorphosis, and the timing of metamorphosis is therefore crucial. The prolongable larval phase in the gnathiid female could be an adaptation to a polygynous, semelparous system and brief copulatory phase after the metamorphosis into adult female.

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.

Resistance by cattle to cattle tick, Boophilus microplus. III. The development of resistance to experimental infestations by purebred Sahiwal and Australian Illawarra Shorthorn cattle

1971 ◽  
Vol 22 (2) ◽  
pp. 331 ◽  
Author(s):  
RW Hewetson
Keyword(s):  
Adult Female ◽  
Acquired Resistance ◽  
Boophilus Microplus ◽  
Cattle Tick ◽  
Control Group ◽  
The Third ◽  
Development Of Resistance ◽  
Significant Difference ◽  
Sahiwal Cattle ◽  
Males And Females

Purebred Sahiwal cattle acquired resistance to Boophilus microplus in a similar manner to crossbred Sahiwal cattle as previously reported. The purebred entire males and females were more resistant than a control group of crossbred steers because they dropped significantly fewer replete ticks than the crossbreds at the third and fourth, but not at the first and second infestations. Adult female ticks dropped by purebred animals were significantly lighter than those dropped by crossbred animals at the fourth infestation only. There was no significant difference in the numbers of eggs laid and hatched from ticks dropped by purebred and crossbred animals. Australian Illawarra Shorthorn steers developed resistance at a second and third infestation which waned at a fourth infestation, but individual steers displayed developing resistance throughout the four infestations. Day of modal drop of replete female ticks appeared to be affected by breed, and developing resistance or season.

Demography of Eurotestudo hermanni in a mesic area of Central Italy

2007 ◽  
Vol 28 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Valeria Ramacciato ◽  
Massimo Capula ◽  
Anna Loy ◽  
Federica Gentilotti
Keyword(s):  
Sex Ratio ◽  
Central Italy ◽  
Average Density ◽  
High Density ◽  
Environmental Constraints ◽  
Adult Males ◽  
Males And Females ◽  
European Populations

AbstractHermann's tortoise (Eurotestudo hermanni) from a mesic area of Central Italy (Isernia, Molise) was investigated during a two-year period (2003-2004). The population is characterized by a fairly high density when compared to other Italian and European populations, with density ranging from 16.16 individuals/ha in 2003 to 25.08 individuals/ha in 2004 (average density 20.84/ha). The sex ratio was 1:1 both in 2003 and 2004. Females were captured in higher percentages from May to July in both years, while males were most abundant from August to October. These differences can be related to the different needs and behaviour of males and females in the two periods, and to the environmental constraints of the study area. All the marked tortoises were found aged between 10 and 21 years. Adult males and females from the study area were small-sized when compared to those from other Italian and European populations.

EFFECT OF SEX AND AGE AT GONADECTOMY ON THE SEBACEOUS RESPONSE TO PROGESTERONE

1977 ◽  
Vol 73 (1) ◽  
pp. 67-70 ◽  
Author(s):  
SAM SHUSTER ◽  
WENDY M. HINKS ◽  
A. J. THODY
Keyword(s):  
Adult Female ◽  
Adult Male ◽  
Female Rats ◽  
Male Rats ◽  
Adult Males ◽  
Adult Rat ◽  
Sebum Production ◽  
Males And Females ◽  
Sebum Secretion

SUMMARY The effect of progesterone on the rate of sebum secretion was examined in intact and gonadectomized rats. In intact, adult, male rats, progesterone administered for 3 weeks decreased sebum secretion; after castration of adult males, progesterone increased sebum secretion and an even greater response occurred in males castrated at 21 days of age. In intact, adult, female rats progesterone slightly increased sebum production. As in the male, the response was affected by the time of gonadectomy, a greater response occurring after spaying at 21 days compared with 10 weeks of age. Thus, the response to progesterone in the adult rat differs in intact males and females and is affected by changes in the endocrine environment induced by gonadectomy, especially near the time of puberty.

scholarly journals Population of Proboscis Monkey (Nasalis lavatus) in Manggar River, Balikpapan City, Indonesia

2021 ◽  
Vol 886 (1) ◽  
pp. 012068
Author(s):  
Ike Mediawati ◽  
Teguh Muslim ◽  
Amir Ma’ruf ◽  
Mukhlisi ◽  
Hery Seputro ◽  
...  
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Anthropogenic Activities ◽  
Proboscis Monkey ◽  
Adult Males ◽  
Conservation Area ◽  
Nasalis Larvatus ◽  
Survey Technique ◽  
Males And Females ◽  
Proboscis Monkeys

Abstract A population estimation of proboscis monkeys (Nasalis larvatus) has been conducted in Manggar River, Balikpapan. In this non-conservation area, the anthropogenic activities threaten the proboscis monkey habitat. Boat survey technique was applied along ± 17 km of the river in the morning and evening. The number of proboscis monkeys in the surveyed area was estimated to range from 57 to 69 individuals with estimated population density of 4.75 individuals/Km2. Moreover, the population of this primates was divided into 4 groups and the sex ratio between adult males and females was 1:2.33. The proboscis monkeys were distributed in the middle of the river to the upstream. The highest population was found in the upstream area with less human activities. Conservation efforts in the Manggar River need to be carried out considering the proboscis monkey habitat in the area has been fragmented and isolated. These efforts could involve local economic communities.

The larva of Hydropsyche doehleri Tobias 1972, based on Swiss material (Hydropsychidae, Trichoptera)

Zootaxa ◽  
2020 ◽  
Vol 4786 (4) ◽  
pp. 535-545
Author(s):  
HEINRICH VICENTINI ◽  
SOFIA WYLER ◽  
JOHANN WARINGER
Keyword(s):  
Abdominal Segment ◽  
Sequence Data ◽  
Light Trap ◽  
Distribution Patterns ◽  
Adult Males ◽  
Diagnostic Features ◽  
Species Association ◽  
Dna Sequence Data ◽  
Males And Females ◽  
Region Information

This paper describes the previously unknown larva of Hydropsyche doehleri Tobias 1972. Species association was enabled by the fact that both larval and adult specimens were collected at the same location and that H. doehleri was the only Hydropsychidae collected at this site, based on light-trap samples of adults. In addition, association of larvae with adult males and females were performed using DNA sequence data from the mitochondrial cytochrome c oxidase region. Information on the morphology of the larva is given, and the most important diagnostic features separating H. doehleri from its sister taxon H. siltalai Döhler 1963 are discussed. In both species, gills are lacking on abdominal segment VII. In the context of the Hydropsychidae key of Waringer & Graf (2011), the two species can be separated by the morphology and coloration of the frontoclypeal apotome, and by their distribution patterns: whereas H. siltalai is widespread in Europe, H. doehleri has been reported from only France, Italy, and southern Switzerland (Tessin).                #We dedicate this paper to Univ. Prof. Dr Hans Malicky on the occasion of his 85th birthday. 

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.

scholarly journals Sex ratio of breeding Common toads (Bufo bufo) – influence of survival and skipped breeding

2010 ◽  
Vol 31 (4) ◽  
pp. 509-524 ◽  
Author(s):  
Thomas Madsen ◽  
Jon Loman
Keyword(s):  
Sex Ratio ◽  
Deterministic Model ◽  
Breeding Site ◽  
Breeding Population ◽  
Bufo Bufo ◽  
Adult Males ◽  
Breeding Sites ◽  
Lower Survival Rate ◽  
Biased Sex Ratio ◽  
Males And Females

AbstractAnuran sex ratio at breeding sites is typically male biased. Such sex ratios may be due to poor female survival, to females not breeding as frequently as males and/or to males becoming sexually mature earlier than females. In the present study, the first two factors are analyzed in a common toad (Bufo bufo) population in southern Sweden. Toads were captured, marked and recaptured at the breeding site during 5 years. Within season capture patterns were analyzed using the Jolly-Seber model and among-year captures using the Closed robust design model. Population estimates of males and females yielded an among year variation in breeding population sex ratio, ranging from 16% to 34% females. On average, 41% (proportion adult alive but not breeding) of the females skipped breeding seasons, whereas the corresponding estimate for males was less than 5%. Yearly survival averaged 42% for adult female and 63% for adult male toads. First year adult males and females had a lower survival rate than older toads. Our results demonstrate that both a female biased mortality rate and a higher proportion of skipped breeding in females contribute to the observed male biased sex ratio. However, a deterministic model suggests other factors may also be involved to obtain this degree of male biased sex ratio, the most likely being that females mature at a later age than male toads.

Antennoseius (Vitzthumia) janus n.sp. (Acari: Ascidae), a mesostigmatic mite exhibiting adult female dimorphism

1989 ◽  
Vol 67 (5) ◽  
pp. 1291-1310 ◽  
Author(s):  
Evert E. Lindquist ◽  
David Evans Walter
Keyword(s):  
Sex Ratio ◽  
Adult Female ◽  
Generation Time ◽  
Egg Production ◽  
Low Density ◽  
Adult Males ◽  
Adult Females ◽  
As Species ◽  
Single Animal ◽  
The Impact

All instars of Antennoseius janus n.sp are described. Adult females occur as two distinct morphs, a nondispersing female with granular soft integument, barbed dorsal setae, emarginated opisthonotal shield, and fully developed sternal shield, and a dispersing female with smooth soft integument, nearly smooth dorsal setae, entire opisthonotal shield, and reduced sternal shield. Granular morph females begin egg production within 3 days of mating; however, smooth morph females delay reproduction for many weeks, apparently to disperse. Adult males and immatures have a granular soft integument and barbed setae similar to the granular morph females. Females produced in single animal or low density cultures (less than six individuals per culture) with excess food are granular morphs, whereas in more crowded cultures 5–100% of the maturing females are smooth morphs. This is the first example of adult female dimorphism confirmed experimentally for any family of mites in the entire order Mesostigmata of the Acari. The impact of this phenomenon on taxonomic concepts in the genus Antennoseius is discussed. A key is included, which distinguishes between the genera Anystipalpus Berlese, 1911 and Antennoseius Berlese, 1916, between the subgenera Antennoseius s.str. and Vitzthumia Thor, 1930, and between the seven forms of Vitzthumia currently regarded as species. All instars of A. janus are voracious predators of nematodes and small arthropods. Development from egg to adult takes 9–11 days on a diet of rhabditid nematodes at 23 °C. Generation time for granular morph females is about 14 days. Females require insemination before eggs can be laid, and the sex ratio is about 1 male: 1.3 females.

scholarly journals Demography of the enigmatic low phase in a cyclic lemming population

2021 ◽  
Author(s):  
Dominique Fauteux ◽  
Gilles Gauthier
Keyword(s):  
Sex Ratio ◽  
Reproductive Potential ◽  
Indirect Evidence ◽  
Adult Males ◽  
Density Dependent ◽  
Live Trapping ◽  
Biased Sex Ratio ◽  
Males And Females ◽  
Cyclic Populations

Abstract Deciphering the mechanism behind the lack of growth during the prolonged low abundance phase of cyclic populations represents a major challenge due to the lack of data. However, long-term capture-mark-recapture datasets can help resolve this question through demographic analyses. We analysed the demography and movements of cyclic brown lemmings on Bylot Island, Canada, with a 16-yr (2004-2019) live-trapping program and looked for inversely density-dependent factors that could contribute to a prolonged low phase. We found that the proportion of females in the population was inversely density-dependent with a strong male-biased sex ratio at low densities but not at high densities. In contrast, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density-dependent, and proportion of females in reproductive condition was weakly density-dependent. Individual body condition, measured as monthly change in body mass, was not density-dependent. Overall, the strong malebiased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sexbias in the first place is still unclear, but indirect evidence suggests that this may be due to a higher vulnerability of nesting females to predation in winter than males.

Sign in / Sign up

Export Citation Format

Share Document