Directional and Fluctuating Asymmetry in Sexual and Asexual Otiorhynchus alpicola Populations

This study concerns the contribution of directional asymmetry (DA) and fluctuating asymmetry (FA) as a characterization of variation in six sexual (diploid) and two asexual (triploid and tetraploid) populations of the weevil Otiorhynchus alpicola. It is shown that DA in sexual populations is about 1 % of the mean length of each of the seven bilateral traits and the average contribution of DA to trait variation is even lower in asexual populations (about 0.85 in triploids and 0.65 in tetraploids forms). The average contribution of FA to the total phenotypic variance is about 23 %, 12 % and 19 % in diploid, triploid and tetraploid populations, respectively. Since FA is generally regarded as a measure of developmental stability, our data indicate that triploid forms of O. alpicola are developmentally more stable than diploid and tetraploid forms. The relationship between the level of ploidy and FA is discussed.     

DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Development, sexual dimorphism, and individual variation were examined in the skeleton of the finless porpoise in the coastal waters of western Kyushu, Japan. Skulls ceased growing by 4 yr. Postcranial skeletons ceased increasing in size at an age older than 11 yr. The finless porpoise was estimated to attain cranial maturity by 4 yr and physical maturity at 14–23 yr. Sexual dimorphism was not detectable in most of the cranial characters but was detected in more than half of the postcranial characters. Females tended to show larger values of postcranial characters. The shape of the pelvic bone was obviously different between males and females. Thus, a discriminant function was proposed to determine sex using measurements of this bone. Individual variation was greatest in the feeding apparatus such as length of the rostrum, and least in the braincase.     

Pathogenesis of SIVmac251 after atraumatic inoculation of the rectal mucosa in rhesus monkeys

Intrarectal inoculation of rhesus monkeys with low doses of SIV_mac led to a prolonged clinical and virological latency that was not observed for high intrarectal doses or for intravenous inoculation. Animals infected intrarectally with low virus doses remained negative for serum antibody responses to SIV for at least one year even though they readily transferred SIV to naive recipients via transfusion of whole blood.     

Selection of buffalo bulls: Sexual behavior and its relationship to semen production and fertility

Forty-four buffalo bulls, used for artificial insemination, were studied to develop libido, mating ability and sexual behavior indices for selection purposes. For each index, 5 categories (i.e., excellent, very good, good, fair and poor) were established. The sexual behavior index was found to be more reliable than the libido and mating ability indices. Buffalo bulls in good to excellent categories were considered acceptable sires.

Reaction time, sexual aggressiveness, and scores of libido, mating ability and sexual behavior differed significantly among the various categories of the 3 indices. Libido significantly correlated with mating ability (r=0.89; P<0.001). Sexual behavior expressed significant relationship with age (r=0.41; P<0.01) and body weight (r=0.48; P<0.01), but was nonsignificant with the scrotal circumference (r=0.28; P>0.05) of buffalo bulls. However, these relationships were absent (P>0.05) in the acceptable sires. Semen production was correlated with sexual behavior in only the fair and poor categories of buffalo bulls (r=0.84; P<0.005). Sexual behavior had no relationship with the fertility rate of buffalo bulls (r=0.44; P>0.05). It is concluded that the sexual behavior index can be used successfully for the selection of buffalo bulls. Excellent- to good bulls should be used in an artificial breeding program if they qualify in the other selection indices.     

Temperature-dependent sex determination in reptiles: Proximate mechanisms,ultimate outcomes,and practical applications

In many egg-laying reptiles, the incubation temperature of the egg determines the sex of the offspring, a process known as temperature-dependent sex determination (TSD). In TSD sex determination is an “all or none” process and intersexes are rarely formed. How is the external signal of temperature transduced into a genetic signal that determines gonadal sex and channels sexual development? Studies with the red-eared slider turtle have focused on the physiological, biochemical, and molecular cascades initiated by the temperature signal. Both male and female development are active processes—rather than the crganized/default system characteristic of vertebrates with genotypic sex determination—that require simultaneous activation and suppression of testis- and ovary-determining cascades for normal sex determination. It appears that temperature accomplishes this end by acting on genes encoaing for steroidogenic enzymes and steroid hormone receptors and modifying the endocrine microenvironment in the embryo. The temperature experienced in development also has long-term functional outcomes in addition to sex determination. Research with the leopard gecko indicates that incubation temperature as well as steroid hormones serve as organizers in shaping the adult phenotype, with temperature modulating sex hormone action in sexual differentiation. Finally, practical applications of this research have emerged for the conservation and restoration of endangered egg-laying reptiles as well as the embryonic development of reptiles as biomarkers to monitor the estrogenic effects of common environmental contaminants. © 1994 Wiley-Liss, Inc.     

Cell cycle mutation in Paramecium tetraurelia discriminates between sexual and vegetative functions

The temperature-sensitive mutation cc1 blocks a number of cell cycle processes in Paramecium including macronuclear DNA synthesis, oral morphogenesis, and the later stages of micronuclear mitosis. Oral morphogenesis and micronuclear mitosis also occur in the sexual pathway. This study shows that cc1 cells can proceed through conjugation or autogamy under restrictive conditions; neither stomatogenesis nor micronuclear mitosis is blocked. Fertilization and macronuclear determination occur normally, but DNA synthesis in macronuclear anlagen is blocked. Therefore, this mutation discriminates between oral replacement during meiosis and vegetative prefission stomatogenesis, and between mitotic spindle elongation during the pregamic and postzygotic divisions and spindle elongation during the vegetative cell cycle. These results point to a fundamental regulatory difference between morphogenesis in the vegetative and sexual pathways. © 1994 Wiley-Liss, Inc.     

榆耳有性结构及生活史的研究

本文通过电镜扫描、石腊切片及用苏木精染色法和DAPI荧光染色,对榆耳子实体有性结构进行观察,证实榆耳子实体菌盖结构分三层:上表层为毛层,表面着生有排列较密集顶端游离的菌丝,它们相互粘连呈菌丝束;中间层为髓部,由较疏松而相互交织在一起的薄壁菌丝组成,菌丝间充满胶质物质;下表层为子实层,表面起伏不平,呈不规则的疣状突起,上面着生担子和囊状体,担子无隔膜棍棒形,外表有不规则的网状纹饰,其顶部着生4个瓶梗状小梗,每个小梗上着生1个椭圆形或腊肠形担孢子,大小为2.5—3.0×6.0—6.5μm,担孢子表面有不规则的网状纹饰结构。在担子间的囊状体为长圆柱形或圆锥形,表面有较密的不规则的网状纹饰。 榆耳有性生殖为异宗配合。绝大多数担孢子含一个细胞核,很少数担孢子含两个细胞核。孢子萌发为一端萌发,也有少数为两端萌发。初生菌丝单核,不能形成子实体,当两种不同遗传性的交配型的初生菌丝结合后,形成具有锁状联合结构的双核菌丝,并可发育成子实体。榆耳具有典型减数分裂过程,不具有减数分裂后核分裂行为,四个子核分别进入四个担孢子内。 在初生菌丝或次生菌丝上,均可产生间生的或顶生的厚垣孢子。经过温度、光照和紫外线照射的诱发,均未发现有其它类型的无性孢子产生。因此,榆耳菌的生活史和大多数担子     

Sexual differentiation of brain and behavior in the zebra finch: Critical periods for effects of early estrogen treatment

In order to determine the critical period(s) during which estrogen alters sexually dimorphic behavior and neuroanatomy in zebra finches (Poephila guttata), nestlings were injected daily 20 μg estradiol benzoate (EB) during posthatching week 1, week 2, week 3, or weeks 1, 2, and 3. At 7 months of age, birds were implanted with testosterone propionate and tested with female partners for singing, dancing, and copulatory mounting. Brains were subsequently processed for morphometry, and the volumes of the song system nuclei HVC, area X, and RA and the soma sizes and densities of neurons in RA were determined. Males given EB during week 1 failed to mount. Females given EB during week 1 were fully masculinized with respect to dancing and RA neuron soma size and density, and were partially masculinized with respect to song nuclei volumes and singing. Treatment beginning after week 1 was ineffective or less effective for all measures. Only for RA neuron measures was treatment for all three weeks more effective than week 1 treatment. Thus the first post-hatching week is the most influential period of those tested for effects of exogenous estrogen on sexual differentiation in this species, and is a period during which both masculinization of females and demasculinization of males is possible. 1994 John Wiley & Sons, Inc.     

Sexual isolation in Drosophila. II. Intraspecific variation in mate recognition systems

A simple behavioral model is used to investigate whether differences in the specific-mate-recognition system (SMRS), occur within species of the Drosophila genus. This model takes into account, and overcomes, the distorting effect of vigor differences on experimental results. Analysis shows significant deviations from the expected values under the assumption of identical SMRSs in around one fifth of the multiple-choice experiments performed with natural strains of twelve different Drosophila species. Different selection procedures raise the number of significant assortative mating results between strains of D. melanogaster and D. pseudoobscura from 3.0% to 32.8%. Finally, sub- or semispecific taxa show variations in their SMRS even more frequently (74.5%). Differences in male vigor and female receptivity are also found. These results show that a classification of Drosophila species based on SMRS stability, as proposed by the “Recognition concept of species”, is virtually impossible.