Distribution and reproductive biology of the blackchin guitarfish, Rhinobatos cemiculus (Pisces: Rhinobatidae), in Tunisian waters (central Mediterranean)

1994 ◽  
Vol 45 (4) ◽  
pp. 551 ◽  
Author(s):  
C Capape ◽  
J Zaouali
Keyword(s):  
Reproductive Biology ◽  
Gravid Female ◽  
Total Sample ◽  
High Rate ◽  
Adult Males ◽  
Central Mediterranean ◽  
Chemical Balance ◽  
Adult Females ◽  
Males And Females ◽  
The Mean

Aspects of the reproductive biology of Rhinobatos cemiculus are described from specimens collected in Tunisian waters. Sizes at first sexual maturity of males and females are 1000 mm and 1100 mm total length (TL), respectively. Adult females are generally larger than adult males, the maximum TL for males and females being 1920 mm and 2300 mm, respectively. The smallest gravid female observed was 1220 mm TL. R. cemiculus is an aplacental viviparous species, with each female having two ovaries and two uteri, both functional. Ripe oocytes in the ovaries, ova, embryos and fully developed fetuses in the uteri are symmetrically distributed. The gestation period could last for a maximum of eight months. Vitellogenesis proceeds in parallel with gestation, and at the time of parturition a crop of ripe oocytes is ready to be ovulated. Ovulation and parturition occur during winter and summer, respectively. There is probably one litter per year. The mean TL and mean weight of fully developed fetuses are 39.6 mm and 115.1 g, respectively. A computed chemical balance of development, based on the mean dry weights of fully developed fetuses and ripe oocytes, is 1.01. This low value is due to the fact that R. cemiculus is purely a lecithotrophic species. Fecundity ranges from 5 to 12 young per litter. Ovarian fecundity and uterine fecundity are slightly correlated with the size of females. Females are more numerous than males in the total sample, as well as in utero and at the juvenile stage; however, this is not the case for subadults and adults. This phenomenon is probably due to segregation of the sexes at different depths during certain stages of the reproductive cycle rather than to a high rate of mortality among subadult and adult females.

scholarly journals MAINTENANCE OF A "PARASITIC" B CHROMOSOME IN THE GRASSHOPPER MELANOPLUS FEMUR-RUBRUM

Genetics ◽  
1977 ◽  
Vol 87 (3) ◽  
pp. 499-512
Author(s):  
Uzi Nur
Keyword(s):  
New York ◽  
Transmission Rate ◽  
B Chromosome ◽  
B Chromosomes ◽  
High Rate ◽  
Adult Males ◽  
High Transmission ◽  
In The Wild ◽  
Males And Females ◽  
The Mean

ABSTRACT About 10-15% of the males and females of the grasshopper Melanoplus femur-rubrum collected near Rochester, New York, possessed a supernumerary B chromosome. The frequency of the B chromosome remained fairly constant during the years 1971-1974. The B chromosome was shown previously to be transmitted at a rate of about 0.5 and 0.8 by 1B males and females, respectively. This study was designed to determine the forces preventing the B chromosome from increasing in frequency due to the high rate of transmission by the females. Eighty inseminated females collected in the wild were analyzed cytologically together with their embryos (10-20 per female). Ten of the 80 females had a B chromosome, and they transmitted it at a rate of about 0.75. Among the 983 embryos analyzed, 0.141 had one B, 0.007 had two, and the mean number of B chromosomes per embryo was 0.155. The frequency of the B chromosome in the sperm pool (0.061) was consistent with a 0.5 rate of transmission. Individuals with two B chromosomes apparently have low viability, because about six were expected, but none was found among 851 adult males and females examined. The data suggest that the viability of the 1B individuals was only about 0.86 that of the OB individuals. There was no evidence that the B chromosome increased the fecundity of either the 1B males or females. It was concluded, therefore, that the B chromosome reduced the fitness of all the individuals carrying it and was thus "parasitic," and that it was maintained in the population only because of its high transmission rate. The maintenance of other B chromosomes with high transmission rates is reviewed.

scholarly journals Sighting heterogeneity of right whales in the western North Atlantic: 1980-1992

2020 ◽  
pp. 245-250
Author(s):  
Moira W. Brown ◽  
Solange Brault ◽  
Philip K. Hamilton ◽  
Robert D. Kenney ◽  
Amy R. Knowlton ◽  
...  
Keyword(s):  
North Atlantic ◽  
Eubalaena Glacialis ◽  
Adult Males ◽  
Adult Females ◽  
Right Whales ◽  
North Atlantic Right Whales ◽  
Males And Females ◽  
The Mean ◽  
Lower Variability ◽  
Juvenile Males

The population of western North Atlantic right whales (Eubalaena glacialis) is distributed primarily between Florida, USA and NovaScotia, Canada, aggregating seasonally in five geographically distinct, high-use areas. To test the effectiveness of monitoring alldemographic classes (juvenile and adult males and females) of the population in these five habitat areas, an evaluation was carried out ofthe identification records of catalogued right whales collected between 1980 and 1992, for which the age, sex and reproductive status (foradult females) were known. The mean annual identification frequency of adult females was significantly lower than that of adult males,juvenile females and juvenile males. Among adult females, reproductively active females were seen significantly more often than expectedwhen lactating (with a calf) than during their pregnancy or resting years. These data suggest that, while research efforts in the five high-usehabitat areas have had relatively equal success at monitoring juvenile males and females and adult males, many adult females are segregatedat times from the rest of the population. Lower variability in annual identification frequencies of adult females indicates that they may bemore site specific in their distribution than males, particularly during the years when they are pregnant or resting from a previous pregnancy.Re-running these analyses using sighting records updated through 2000 will help determine if the trends continue to be documentedregardless of changes in survey effort and patterns of habitat use of some animals.

New data on the reproductive biology of the common guitarfish of the Gulf of Gabès (southern Tunisia, central Mediterranean)

2008 ◽  
Vol 88 (5) ◽  
pp. 1063-1068 ◽  
Author(s):  
Samira Enajjar ◽  
Mohamed Nejmeddine Bradai ◽  
Abderrahmen Bouain
Keyword(s):  
Sexual Maturity ◽  
Gravid Female ◽  
Central Mediterranean ◽  
Gulf Of Gabes ◽  
Chemical Balance ◽  
Gulf Of Gabès ◽  
Southern Tunisia ◽  
The Common ◽  
Males And Females ◽  
Size At Birth

The common guitarfish Rhinobatos rhinobatos is abundanly captured along the coast of the Gulf of Gabès (southern Tunisia). The sizes at the first sexual maturity of females and males are 790 and 700 mm total length (TL) respectively. Females are larger than males; the maximum TL for males and females is 1000 and 1200 mm respectively. The smallest gravid female observed is 750 mm TL. Rhinobatos rhinobatos is an aplacental viviparous species. The two ovaries and the two uteri are functional. Mature oocytes and foetuses are symmetrically distributed respectively in ovaries and uteri. Vitellogenesis and gestation occur simultaneously. Gestation lasts 10 to 12 months; parturition occurs from the end of summer to the beginning of autumn. Mating and ovulation take place after parturition. Ovarian fecundity is higher than uterine fecundity; means of 8.95 and 5.34 young per year are respectively calculated. There is a positive relationship between the two categories of fecundity and size of females. The size at birth ranges from 250 to 290 mm TL. The common guitarfish is purely a lecithotrophic species. The chemical balance of development is estimated at 1.02.

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.

Checks in the statolith microstructure of the short-finned squid, Illex coindetii from the Strait of Sicily (central Mediterranean)

1999 ◽  
Vol 79 (6) ◽  
pp. 1091-1096 ◽  
Author(s):  
Alexander Arkhipkin ◽  
Patrizia Jereb ◽  
Sergio Ragonese
Keyword(s):  
Peripheral Zone ◽  
Mantle Length ◽  
Central Mediterranean ◽  
Strait Of Sicily ◽  
Younger Age ◽  
Males And Females ◽  
The Mean ◽  
Age Range

Microstructural prominent discontinuities (checks) were observed within the statoliths of the short-finned squid Illex coindetii from the Strait of Sicily. Two hundred and forty-two pairs of statoliths were extracted from specimens (52–175 mm of mantle length, ML) sampled during autumn 1995 and analysed. Beside the check delimiting the postnuclear zone, up to four peripheral checks were detected in the peripheral zone. The occurrence of peripheral checks in the statoliths of immature squid was low (5–15%), whereas 80–95% of mature squid had peripheral checks. The mean number of peripheral checks within statoliths of mature males and females did not differ significantly (1.53–1.68 peripheral checks per squid). In mature and spawning females, the number of peripheral checks corresponded well with the number of spermatophoric bundles inside the mantles. Age at peripheral check formation was estimated for each sex, indicating that the first peripheral check formed at a significantly younger age in males than in females. Formation of the first peripheral check coincided with the start of maturation in both sexes, at a wide age range. The number of increments between peripheral checks subsequent to the first one declined sharply and remained similar in the two sexes, with a predominant mode between three and seven increments. A possible relationship between the number of peripheral checks and mating events in I. coindetii is discussed.

Sex Ratios and Lengths of Adult Sea Lampreys (Petromyzon marinus) from a Lake Ontario Tributary

1974 ◽  
Vol 31 (1) ◽  
pp. 122-124 ◽  
Author(s):  
I. C. Potter ◽  
F. W. H. Beamish ◽  
B. G. H. Johnson
Keyword(s):  
Narrow Range ◽  
Sex Ratios ◽  
Petromyzon Marinus ◽  
Lake Ontario ◽  
Sea Lamprey ◽  
Adult Males ◽  
Sea Lampreys ◽  
Males And Females ◽  
The Mean ◽  
Humber River

The mean lengths of adult males and females of the sea lamprey (Petromyzon marinus) migrating into the Humber River from Lake Ontario in each of the years 1968–1972 varied little, and were similar to those found by other workers in recently established populations in the upper lakes. In contrast, the ratio of males to females, which lay within the narrow range of 1:1 to 1.26:1, was similar to those reported for long-established populations.

scholarly journals The Diet and Sexual Differences of the Caspian Bent-Toed Gecko,Tenuidactylus caspius(Squamata: Gekkonidae), in Northern Iran

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Vida Hojati ◽  
Reza Babaei Savasari
Keyword(s):  
Sexual Dimorphism ◽  
Culex Pipiens ◽  
Tail Length ◽  
Adult Males ◽  
Northern Iran ◽  
Widespread Distribution ◽  
Adult Females ◽  
Significant Difference ◽  
Males And Females ◽  
Prey Items

The Caspian bent-toed gecko,Tenuidactylus caspius, is one of the most common nocturnal lizards of Iran with widespread distribution especially in the northern provinces. This research was done in order to study the diet and sexual dimorphism of this species in Sari County from 5 May to 20 October. During this research, 40 specimens of them including 20 males and 20 females were studied for diet and 140 specimens including 70 adult males and 70 adult females were studied for sexual dimorphism. Prey items identified were insects that belong to 15 species of 8 families and 6 orders. The most common prey items wereCulex pipiensandMusca domestica. There is no significant difference between diets of males and females. Results show that the adult males in addition of having the apparent femoral and preanal pores are heavier than females and have larger body, head, and tail length.

Movements and cumulative range size of the platypus (Ornithorhynchus anatinus) inferred from mark–recapture studies

2012 ◽  
Vol 60 (5) ◽  
pp. 352 ◽  
Author(s):  
M. Serena ◽  
G. A. Williams
Keyword(s):  
Range Size ◽  
River Catchment ◽  
Young Males ◽  
Adult Females ◽  
Ornithorhynchus Anatinus ◽  
Males And Females ◽  
The Mean ◽  
Western Victoria ◽  
Fyke Nets ◽  
Age And Sex

The extent of mammalian movements often varies with size, sex and/or reproductive status. Fyke nets were set along streams and rivers near Melbourne (southern Victoria) from the mid-1990s to 2007, and in the Wimmera River catchment (western Victoria) from 1997 to 2005, to assess how far platypus of different age and sex classes travelled between captures and over longer periods. The mean distance between consecutive captures of adults did not vary significantly as intervals increased from 1–3 months to >3 years, suggesting that most individuals occupied stable ranges. However, adult females travelled, on average, only 35% as far between captures as males in southern Victoria, and 29% as far in the Wimmera. Up to half of this difference may be explained by variation in size-related metabolic requirements. Immature males and females respectively moved 61% and 53% as far, on average, as their adult equivalents, although two young males dispersed >40 km. Adults incrementally occupied up to 13.9 km of channel in the case of a male (based on six captures over 67 months) and 4.4 km of channel in the case of a female (based on five captures over 127 months).

The effect of non-immune stresses on the development of Strongyloides ratti

Parasitology ◽  
2005 ◽  
Vol 131 (3) ◽  
pp. 383-392 ◽  
Author(s):  
M. CROOK ◽  
M. E. VINEY
Keyword(s):  
Immune Response ◽  
Parasitic Nematode ◽  
Host Immune Response ◽  
Natural Host ◽  
Adult Males ◽  
Free Living ◽  
Developmental Effects ◽  
Adult Females ◽  
Males And Females ◽  
Living Adult

Strongyloides ratti is a parasitic nematode of rats. The host immune response against S. ratti affects the development of its free-living generation, favouring the development of free-living adult males and females at the expense of directly developing, infective 3rd-stage larvae. However, how the host immune response brings about these developmental effects is not clear. To begin to investigate this, we have determined the effect of non-immune stresses on the development of S. ratti. These non-immune stresses were subcurative doses of the anthelmintic drugs Ivermectin, Dithiazanine iodide and Thiabendazole, and infection of a non-natural host, the mouse. These treatments produced the opposite developmental outcome to that of the host immune response. Thus, in infections treated with subcurative doses of Ivermectin, Dithiazanine iodide and in infections of a non-natural host, the sex ratio of developing larvae became more female-biased and the proportion of female larvae that developed into free-living adult females decreased. This suggests that the mechanism by which the host immune response and these non-immune stresses affect S. ratti development differs.

scholarly journals Rheotaxis Response Based on Sexual Dimorphism in the Green Swordtail Fish, Xiphophorus hellerii

Biota ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 128-139
Author(s):  
Muhammad Irsyad Abiyusfi Ghafari ◽  
Vita Fitrianti
Keyword(s):  
Sexual Dimorphism ◽  
Gravid Female ◽  
Adult Males ◽  
Dioecious Species ◽  
Swordtail Fish ◽  
Xiphophorus Hellerii ◽  
Males And Females ◽  
Morphological Differences ◽  
Gravid Females ◽  
The Individual

Morphological distinctions between males and females of a species are referred to by sexual dimorphism. It may result from various selection pressures affecting either sex or both and may occur in any dioecious species, including Green Swordtail fish, which are sexually reproductive. This study examined the different rheotaxis responses of Xiphophorus hellerii based on different sexes and morphological features. We analyzed ten adult males, ten gravid females, and ten non-gravid females of Xiphophorus helleri collected down the river and transferred into the column. We counted the number of the individual that performed positive rheotaxis (+), negative rheotaxis (-), and indifference response (0). The result showed different rheotaxis responses shown by male, non-gravid female, and gravid female X. hellerii. The highest percentage of positive rheotaxis response (movement against the current) was shown by non-gravid female X. hellerii, reaching up to 89%. Morphological differences between male, non-gravid female, and gravid female X. hellerii appear to affect the orientation and ability of X. hellerii in giving response against current and certainly has an impact on their survival in nature.

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