The first evidence of intersexuality in Atka mackerel Pleurogrammus monopterygius (Hexagrammidae)

Summary Histological examination of Atka mackerel ovotestes reveals the possibility of intersexuality. Individuals with bisexual gonads have been caught in the North Pacific near the south-east coast of the Kamchatka peninsula. While intersex appeared to be normal females with developing ovaries, histological analysis showed the presence of both female and male tissue in the same gonad. Specifically, primary growth, cortical alveolar and primary vitellogenic oocytes were located among spermatogonia cysts. The prevalence of intersexuality in the population was less than 0.1%.

Sex-linked transcriptional divergence in the hermaphrodite fungus Neurospora tetrasperma

In the filamentous ascomycete Neurospora tetrasperma , a large (approx. 7 Mbp) region of suppressed recombination surrounds the mating-type ( mat ) locus. While the remainder of the genome is largely homoallelic, this region of recombinational suppression, extending over 1500 genes, is associated with sequence divergence. Here, we used microarrays to examine how the molecular phenotype of gene expression level is linked to this divergent region, and thus to the mating type. Culturing N. tetrasperma on agar media that induce sexual/female or vegetative/male tissue, we found 196 genes significantly differentially expressed between mat A and mat a mating types. Our data show that the genes exhibiting mat -linked expression are enriched in the region genetically linked to mating type, and sequence and expression divergence are positively correlated. Our results indicate that the phenotype of mat A strains is optimized for traits promoting sexual/female development and the phenotype of mat a strains for vegetative/male development. This discovery of differentially expressed genes associated with mating type provides a link between genotypic and phenotypic divergence in this taxon and illustrates a fungal analogue to sexual dimorphism found among animals and plants.

Sex determination in honey bees (Apinae and Meliponinae) and its consequences

The first experiments on sex determination in bees began with Dzierzon, Meves, Nachtsheim, Paulcke, Petrunkewitsch, Manning. Whiting, (1943) found multiple alleles in Bracon xo that are the Rosetta stone of sex determination in Hymenoptera. Whiting also discovered that some species of microhymenoptera do not possess xo sex alleles. Therefore, Hymenoptera apparently presents two types of sex determination superimposed on haplodiploidy. In the panmictic groups hemizygous (xo1, xo2,... xon) and homozygous (xo1xo1, xo2xo2... xonxon) are males while heterozygous (xo1xo2, ... xon-1xon) are females. There is no such series of xon in endogamous Hymenoptera, since the constant elimination of diploid males would be damaging to the population and the mutation of xo to xon would be quickly eliminated. Besides the Whiting hypothesis, four others are discussed. The new hypothesis of genomic imprinting, of Beukeboom, is eliminated since: a) spermatozoa that develop within the egg produce male tissue; b) telitokous parthenogenesis due to the fusion of two haploid cells develop into females; c) last instar larvae treated with juvenile hormone become queens. The Cunha and Kerr hypothesis (female determining genes are totally or partially additive and male determination is totally or partially nonadditive) explains all known cases. The xo is a female determining gene. Sex determination in social bees led to the gradual evolution of two systems of caste determination: one in which queens and workers are similar and males are very different (Apinae), and another in which workers and males are very similar and both very different from the queens (Meliponinae). This second system in stingless bees implies that many of the mutations that improve worker capacities also affect the males that will carry out some activities that in Apis are clearly female ones. Ten of these activities are described.

In-vitro evidence for the autoregulation of prolactin secretion at the level of the pituitary gland in the rat

ABSTRACT The autoregulation of rat prolactin secretion at the level of the pituitary gland was investigated, using a static incubation system. The rate of prolactin secretion from the female anterior pituitary gland in vitro was found to be constant when the medium was changed at 20-min intervals. However, when the medium was left unchanged and secretory products were allowed to accumulate, prolactin secretion began to decline within 60 min. This effect was not observed with the male tissue, where the level of accumulated prolactin did not reach that at which the inhibition occurred using female tissue. The nature of the putative secretory product causing the inhibition of prolactin secretion was investigated. Exogenous bovine prolactin (1–4 mg/l) caused an inhibition of endogenous rat prolactin secretion. Inclusion of monoamine oxidase in unchanged medium, to prevent dopamine accumulation in the medium (a possible consequence of co-storage and cosecretion with prolactin granules), did not prevent the inhibition observed in the control incubation. We therefore conclude that in-vitro autoregulation of prolactin secretion can occur at the level of the pituitary gland, probably due to the accumulated prolactin having a feedback action on the lactotroph. This might be of physiological significance if localized concentrations of the hormone within the gland are high. J. Endocr. (1987) 115, 13–18

CONTROL OF FEMALE REPRODUCTION IN DROSOPHILA: GENETIC DISSECTION USING GYNANDROMORPHS

ABSTRACT The sexual behavior of Drosophila melanogaster gynandromorphs was studied to analyze the relationship between different steps in the female reproductive pathway. It was assumed that, in some gynandromorphs, certain female functions are missing because the corresponding control sites (foci) are either composed of male tissue or did not develop. A given gynandromorph can show elements of both male and female reproductive pathways. None of the steps of the female reproductive pathway appeared to be dependent on any other, in contrast to male behavior where, for example, following of females is a prerequisite for attempted copulation. By correlating each of the behaviors with the genotype of the cuticle, we confirmed previous findings that the focus for the female sex appeal is located in the abdomen, but receptivity to copulation is controlled by a site in the head. Many of the gynandromorphs did not lay eggs, presumably because either the focus controlling egg transfer from the ovaries to the uterus or the one controlling egg deposition was composed of male tissue. Many of the nonovipositing gynandromorphs laid eggs while dying or could be induced to deposit eggs after implantation of hormone-producing glands or topical application of a juvenile hormone analog. Some of the noninseminated gynandromorphs laid eggs at the rate characteristic for inseminated females, suggesting that an oviposition focus (mapping in the head region) suppresses oviposition in virgin females, but not in gynandromorphs whose focus is composed of male tissue. Some of the inseminated gynandromorphs oviposited eggs at a low rate, possibly because the focus responsible for detection of insemination could not function properly. Some of the inseminated gynandromorphs laid unfertilized eggs, revealing the importance of the focus controlling sperm release from the seminal receptacle. Foci controlling egg transfer, egg deposition and sperm release are located in the thorax, according to mosaic fate mapping results and studies on the reproductive behavior of decapitated females. The location of egg deposition in the culture vial seems to be controlled by a brain site. Sexual behavior in Drosophila does not depend on the presence (or absence) of the ovary or germ line.

Genetics of Gracilaria tikvahiae (Rhodophyceae). VII. Further observations on mitotic recombination and the construction of polyploids

Tetrasporophytes of the marine red alga Gracilaria tikvahiae produce spermatia as well as tetraspores. It has been demonstrated previously that these spermatia are diploid and are produced as a consequence of mitotic recombination in somatic cells of the fertile thallus. It has now been demonstrated that female tissue is also present, often adjacent to the male tissue as would be expected, but is more difficult to recognize because it rarely becomes fertile. However, it was found that female tissue could be excised from the tetrasporophyte and induced to regenerate into complete fronds. Crossing experiments indicated that this female tissue was functional and diploid like the corresponding male tissue. Diploid male and female fronds have been established in culture as free-living plants. Morphological mutants of Gracilaria were found useful in obtaining stocks of diploid gametophytes. Triploid and tetraploid sporophytes were readily synthesized by using the diploid gametophytes (or spermatia from normal diploid tetrasporophytes) in crosses to each other or to normal haploid gametophytes. In one case an apparent tetraploid was synthesized by crossing a haploid female with a triploid tetrasporophyte. In this work polyploid designations are made on the basis of the method of construction and the reproductive behaviour of the polyploids. Cytological confirmation (made for a triploid previously) is incomplete for tetraploids but supports the designations that have been made.

Regeneration and compartments in Drosophila

A clonal analysis was performed in order to study the process of regeneration in wounded wing discs of Drosophila. Regeneration was induced either by cutting the disc in situ, or by shifting gynandromorphic larvae whose male tissue was hemizygous for a temperature sensitive cell lethal to the restrictive temperature. Fast growing M+ clones, labelled with y and/or mwh, were produced by X-irradiation of the following genotypes: y; scJ4(y+)M(3)i55/ mwh jv M+ (series I), and l(1)ts 504 sn3l(1)ts 5697/ In(1)w°vC; M(3)i55/mwh M+ (series II). The clones were induced either before or after the experimental lesion. Clones initiated one day prior to the lesion were able to cross compartment boundaries whereas clones initiated one day after the lesion did not do so. It is concluded that cells involved in the process cf regeneration lose their compartmental commitment, but that later on the growing population of cells again becomes subdivided into the same compartments.

The Reproductive Behaviour of Gynandromorphic Drosophila melanogaster

Reproductive behaviour was studied in 192 gynandromorphs with female genitalia and reproductive system, produced by ring-X chromosome loss. Male and female behaviour patterns were frequently found to coexist in the same individuals, and male courtship behaviour, when it occurred, retained its characteristic hierarchical organisation. Sexually receptive individuals were found to be an almost perfect subset of those ovipositing, and the control of both of these behaviours mapped to the head, as did male orientation (courtship). High rates of wing flicking, a response of males to courtship, mapped rather to the thorax, although a quantitative analysis demonstrated that the frequency of flicking behaviour was also influenced by male tissue in the head. In non-ovipositing individuals mature oocytes were retained in the ovary. An egg held in the uterus is not deposited by a fly without female tissue in the head and all but one sexually receptive individuals laid eggs. It is therefore concluded that both of these behaviours depend upon closely related neural circuitry operating the genital musculature under control from the brain.