REPRODUCTIVE MATURITY AND SEASONALITY OF MALE SPOTTED DOLPHINS, STENELLA ATTENUATA, IN THE EASTERN TROPICAL PACIFIC

We estimated age at attainment of sexual maturity and examined reproductive seasonality for male spotted dolphins, Stenella attenuata , from the eastern tropical Pacific Ocean. Maturity was determined by histological examination of testes. Average age at sexual maturation was 14.7 yr (the mean of two readers' age estimates). Testis and epididymis weight and seminiferous tubule diameters were reliable indicators of maturity, whereas age, length and color phase were less reliable. Seasonality was determined by changes in testis and epididymis weight, relative quantity of spermatids and spermatozoa, and lumen diameter, as well as an index of testis development (weight of the right testis and epididymis divided by length of the right testis). Testis and epididymis weights and index values peaked in July and August, midway between two predicted mating seasons for the northern offshore stock, but spermatozoa levels were elevated during the predicted breeding seasons.     

Asexual propagation and reproductive strategies in aquatic Oligochaeta

A great variety of asexual reproductive modes are known among aquatic oligochaetes. The main types of these modes are shortly described. Based upon observations on natural populations, the possible genetical and ecological implications of asexual reproduction are discussed. The following points are emphasized: (1) The often expressed expectations of a strong predominance of one particularly adaptive genotype is not born out. (2) In most cases, a number of genetically distinct clones are present in each population, and they show a strong differential distribution in heterogeneous environments, indicating an effective exploitation of the available resources. (3) Most cases of asexual propagation are reproductive strategies of their own and not escape mechanisms. (4) The mechanisms underlying asexual propagation are complex and involve many aspects of the life history. The great variety of types among aquatic oligochaetes offer particularly useful models for the study of these problems.     

Effects of starvation on growth and reproductive apparatus of two immature freshwater snails Biomphalaria pfeifferi and Biomphalaria glabrata (Gastropoda: Planorbidae)

Starvation of immature snails of Biomphalaria pfeifferi and B. glabrata results in an arrest of growth and animals remain immature. Spermatogenesis is limited to spermatogonia (B.g.) or spermatocytes 1 (B.p.). The number and the size of oocytes remain inferior to that of controls. Animals show reduced genital tracts.Once feeding is restored, growth is resumed but wet weight and shell diameter do not reach the same level as in controls. Fecundity and gametogenesis do not differ from that in controls. Genital tracts weight is proportional to body weight.     

Physiology and morphology of the larval sexual pheromone-sensitive neurones in the olfactory lobe of the cockroach, Periplaneta americana

Deutocerebral neurones of larval and adult male cockroaches responding to the female pheromone and its components were recorded extracellularly. No responses to the female pheromone were found in larvae younger than about 10th instar. However, two groups of pheromone-sensitive neurones were recorded in males from 10th instar onwards as in adults. A correlation and factor analysis based on the cells' responses to the pheromone stimuli was used to test the correspondence of these larval and adult cell groups. The recorded larval pheromone-sensitive neurones were stained with cobalt and their morphology compared with that of the adult neurones.     

Breeding vervet monkeys in a closed environment

A breeding group of vervet monkeys produced 95 offspring over five years. Fetal wastage for 114 pregnancies was 16.7%. Uterine sizes were recorded for 103 pregnancies in various stages of gestation. This enabled diagnosis of pregnancy, estimation of stage of gestation, and prediction of parturition to within two weeks. Detailed observations were made on dental eruption, pelage development, and growth of 57 infants.     

Reproductive strategies of the orang-utan: New data and a reconsideration of existing sociosexual models

Recent field data indicate that MacKinnon’s model of the orang-utan’s sexual and agonistic activity needs to be revised. In this model, male reproductive activity is concentrated in an extended phase of subadulthood and in early adulthood. According to this model, the role of older adult males is primarily that of range guardian, and in that role they would ensure that the offspring they had generated earlier would have safe access to food resources. This study presents cases suggesting that subadult males, even though sexually active, may have low reproductive success. In previous studies adult males were shown to display less sexual initiative than subadult males. In this study an adult male was at times involved infrequent mating activity in response to proceptive activity of females in the course of consortship. This adult male proved to be a successful breeder, thus refuting the hypothesis of adult male sterility. The female is most likely to conceive through cooperative mating in lengthy consortships with the dominant resident adult male. We hypothesize that the extended subadult phase represents a submissive strategy, allowing subadult males to remain in the home range of adult males but with minimal reproductive success.     

Territoriality and fighting in a colonial thrips, Hoplothrips pedicularius, and sexual dimorphism in Thysanoptera

ABSTRACT.

• 1 Hoplothrips pedicularius (Haliday) (Thysanoptera: Phlaeothripidae), a tubuliferan thrips in which males possess greatly enlarged forelegs, lives in colonies on Stereum fungus.
• 2 Females oviposit onto communal egg masses, and males fight by grasping and stabbing with their forelegs in territorial defence of oviposition areas. Prolonged escalated fights occur between males who are of similar size.
• 3 Larger males usually win fights and become dominant at the oviposition area. Dominant males secure 80% of matings, and mate most frequently during oviposition periods, with an ovipositing female.
• 4 Smaller, subordinate males avoid fights and attempt to 'sneak’copulations. However, they occasionally challenge the dominant male. Challenges tend to follow copulations by the subordinate male and occur more frequently between males who are of similar size.
• 5 Subordinate males who eventually leave the oviposition area are larger than those who remain, have frequently challenged the dominant male, and have more frequently been stabbed.
• 6 Sexual dimorphism in thrips is associated with gregariousness, claustral habitats, female-biased sex ratios, and male winglessness. In thrips genera in which males exhibit foreleg armature, males are larger relative to females. The ecological circumstances promoting sexual dimorphism and male fighting in spatially-structured populations are discussed.

     

Sexual behavior and reproduction ofCercocebus albigena johnstonii in Kibale forest,Western Uganda

Gray-cheeked mangabeys live in multimale social groups. Two groups of these monkeys were studied extensively over a period of 22 months, and a further eight groups were observed opportunistically. Data on the occurrence of sexual swelling infernales were collected and the different phases of swelling and deflation are described in detail together with data on their duration. The data were found to agree broadly with those presented by other workers on captive animals. Pre and postpartum swellings are described. The majority of copulations was observed to occur at peak swelling and a specific gesture, the head flag, was noted as a solicitation. The data on initiation of copulations show that the males initiated more copulations than the females. However, female-initiated copulations ended in ejaculation more often than male-initiated copulations. The behaviors of the mangabeys during precopulation and copulation were found to be broadly similar to those of the macaque. Copulations were observed most often on the day of peak swelling;however, adult males were the only animals to copulate prior to peak swelling. Subadult male copulations were most often after peak swelling. Masturbation was observed to ejaculation on two occasions. The data show gestation periods of between 184 and 189 days. A mean interbirth interval was calculated to be 33.33 ± 15.87 months.     

Induction of sexual reproduction in Opalina sudafricana by injecting its host Bufo regularis with gibberellic acid

Induction of sexual reproduction in Opalina sudafricana by injecting its host Bufo regularis with gibberellic acid. International Journal for Parasitology4, 203–206. Opalina sudafricana parasitic in the rectum of Bufo regularis was induced to reproduce sexually when its host was injected subcutaneously with 0·3 mg of gibberellin-A₃. This plant growth substance had no effect on the induction of encystation in the parasites in vitro. Urine of toads injected with gibberellin-A₃ induced sexual reproduction (encystation) in the opalinids in vitro. It is speculated that the plant hormone must either be broken down into an active substance by the toad or cause the toad to excrete its own gonadal hormones (or other hormones) into the urine. This active substance or the excreted hormones may induce division in the parasites resulting in the formation of small forms which encyst.