Descripción: Haemalopinus suis (Anoplura) and Menacanthus stramineus (Mallophaga) have been cytogenetically analyzed. Both species have 2n = 10, holokinetic chromosomes, and achiasmatic male meiosis. Bivalents orientate with their long axis perpendicular to the spindle fibers at melaphase I, and first anaphase is reductional. As in other species of Phthiraptera, male gametogenesis follows a particular pattern: each cell entering meiosis results in a cyst of 64 (in H. suis) and 32 (in M. stramineus) spermatozoa and 64/32 non‐functional cells (=pycnotic nuclei). The results are compared with those previously reported for Phthiraptera, and a new terminology for the different stages of male gametogenesis is proposed. The low chromosome number together with the achiasmatic nature of male meiosis and the mitotic divisions that follow meiosis may restrict the potential for genetic variability. This might be related to the high host specificity of these parasites. Copyright © 1993, Wiley Blackwell. All rights reserved

Descripción: The haploid DNA content of Aeshna confusa (2n = 27, n = 13 + XO, male). A. bonariensis (2n = 26, n = 12 + neo-XY, male) and A. cornigera planaltica (2n = 16, n = 7 + neo-XY, male) has been determined (2.16 ± 0.16 pg, 1.81 ± 0.17 pg, and 2.08 ± 0.08 pg, respectively). Despite the differences in chromosome size and number, differences in DNA content between species are not significant. The karyotypic analysis of Aeshna species leads to the conclusion that fusions between autosomes or autosome and the sex chromosome, are the only chromosome rearrangement that occurred during evolution. In the species here studied, fusions have taken place with a minimal loss of DNA; however, other species of the genus show important differences in genome size, which cannot only be justified by fusion events.

Descripción: Fil:Schweigmann, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: We examined diurnal and nocturnal nectar secretion across sexual stages in protandrous Alstroemeria aurea, a bumble bee-pollinated herb with long-lived flowers native to the southern Andes. We found the following patterns: (1) most nectar was produced diurnally and (2) three times more sugar was secreted during the male than female phase, not only because the male phase lasted longer but also because the rate of nectar production was higher. This 3:1 ratio in nectar production matched the ratio of the minimum number of bumble bee visits required on average to saturate male (pollen removal) vs. female (seed set) functions. Standing crop of nectar, on the other hand, did not differ greatly between male- and female-stage flowers left open to visitors, because the high-production male-phase flowers were visited more frequently than female-phase flowers. In an experiment concurrent with the repeated nectar sampling of individual flowers over their life-span, we removed pollen from anthers or deposited pollen on stigmas by hand. Neither treatment, designed to mimic effects of visits by Alstroemeria's native bumble bee pollinator, affected nectar production. The absence of plasticity in nectar secretion in relation to pollination events may reflect a low cost of nectar production, or may result from developmental constraints related to the evolution of the synchronous protandry that characterizes A. aurea.

Descripción: Background. The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines. Results. Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent. Conclusion. Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology. © 2007 Soto et al; licensee BioMed Central Ltd.

Descripción: Factors affecting mating behaviour in the bug Triatoma infestans were quantitatively studied in the laboratory. Experimental conditions were established so that the probability of copulation increased with the time elapsed since the first adult meal. Copulatory attempts by males did not vary as a function of time, but rejections by females became significantly less frequent with the post feeding time. Non-receptive females displayed four types of rejection behaviour, i.e. flattening, stridulation, evasion and abdominal movements. The occurrence of stridulation performed by females in a sexual context was observed in a regular fashion and was quantified for the first time in this species.

Descripción: Specimens and eggs masses of the gastropod Trochita pileus were collected during a research cruise by bottom trawling at depths between 82 m and 120 m. Adult T. pileus were found attached to such hard substrata as the shells of scallops and oysters. The egg mass of T. pileus is composed of 7-8 transparent, triangular-shaped egg capsules fixed to the substratum with stalks. Four egg masses collected from brooding females, with a total number of 241 embryos, were examined. Trochita pileus is a protandrous hermaphrodite, and histological studies of the male, transitional, and female gonads were performed. The testicular portion of the gonad in both male and transitional individuals and the ovary of the female were studied by histological techniques. Spermatogenesis was observed for males and transitional individuals.

Descripción: Most primates studied have the usual XX/XY sex-chromosome system. However, exceptions to this rule among howler monkeys have been suggested by several authors. Recently a quadrivalent was discovered in male meiosis of Alouatta caraya and it was established that this species has an X1X2Y1Y2 sex chromosome system. On that basis, a cytogenetic analysis of 25 males of this species is described. showing the corrected karyotype of this species. Each chromosome involved in the particular sex-chromosome system of this species is identified on the basis of mitotic chromosome measurements. G and C-banding patterns as well as on the relative measurements of synaptonemal complexes. It is now established that A. caraya has a karyotype with 2n = 52 in both sexes, and that the male one shows a single autosome 7 (X2) besides the X (X1) and the two products of the reciprocal translocation between the second autosome #7 and the Y chromosome (Y1 and Y2), while females show a homomorphic pair #7 (X2) and a pair of X1. The evolutionary implications of the exceptional primate species having composite sex-chromosome systems are discussed.

Descripción: In many groups of insects with holokinetic chromosomes the meiotic process is, without doubt, either pre‐reductional or post‐reductional. In Odonata, however, the mode of orientation (axial or equatorial) and type of meiosis (pre‐ or post‐reductional) of bivalents is still controversial. Copyright © 1995, Wiley Blackwell. All rights reserved

Descripción: The factors affecting the sexual behaviour of Panstrongylus megistus were studied under laboratory conditions. A general description of mating behaviour is presented for this species. The effect of the time elapsed after the first imaginal feeding on the mating frequency, the motivation of males to mate and the rejection behaviour by females, were analyzed. We also determined the number of copulas accepted by females of this species. Finally, the possible existence of a sexual chemical signal promoting male aggregation around mating couples was evaluated. Results showed that mating frequency increased with the time elapsed since the first adult meal. Despite the number of male copulatory attempts did not change as a function of time, the rejection behaviour of females became gradually less frequent. Females rejected mating by means of body flattening on the substrate, abdominal movements, evasion or stridulation. After a single copula, females did not usually accept to mate again. Neither male nor female aggregation around mating couples was observed, suggesting the absence of a sexual assembling pheromone in P. megistus.

Descripción: Modulation of sensitivity to sensory cues by experience is essential for animals to adapt to a changing environment. Sensitization and adaptation to signals of the same modality as a function of experience have been shown in many cases, and some of the neurobiological mechanisms underlying these processes have been described. However, the influence of sensory signals on the sensitivity of a different modality is largely unknown. In males of the noctuid moth, Spodoptera littoralis, the sensitivity to the female-produced sex pheromone increases 24 h after a brief preexposure with pheromone at the behavioral and central nervous level. Here we show that this effect is not confined to the same sensory modality: the sensitivity of olfactory neurons can also be modulated by exposure to a different sensory stimulus, i.e., a pulsed stimulus mimicking echolocating sounds from attacking insectivorous bats. We tested responses of preexposed male moths in a walking bioassay and recorded from neurons in the primary olfactory center, the antennal lobe. We show that brief exposure to a bat call, but not to a behaviorally irrelevant tone, increases the behavioral sensitivity of male moths to sex pheromone 24 h later in the same way as exposure to the sex pheromone itself. The observed behavioral modification is accompanied by an increase in the sensitivity of olfactory neurons in the antennal lobe. Our data provide thus evidence for cross-modal experience-dependent plasticity not only on the behavioral level, but also on the central nervous level, in an insect.

Descripción: A population of Belostoma sp. polymorphic for the sex chromosome determining system has been analyzed. The fundamental karyotype of the species is 2n = 16 = 14 + XY (male), and at different times individuals 2n = 17 have been encountered in a low frequency (27% and 16%, respectively). Sex chromosome area measurements confirm that the original X chromosome of the XY system has fragmented into two unequal-sized chromosomes (X1 and X2). At male metaphase II, the sex univalents associate in a pseudotrivalent that can show different arrangements (in a chain, in a double-plate, or in other transitional arrangements). Their frequency varies among individuals. The present polymorphic population represents a direct evidence of a multiple sex chromosome system originating through fragmentation of the single X. The different kinds of arrangement of the three sex chromosomes at male metaphase II, and their frequency within each individual suggest that some forces are acting to achieve a double plate arrangement and a regular meiotic behaviour. The maintenance of the polymorphism during more than three years seems to indicate that the new chromosomal variant is neutral, or even could be selectively advantageous.

Descripción: The life cycle of Ascocotyle (Leighia) hadra n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei, collected from Los Ranchos stream, near Mercedes city, Buenos Aires Province, Argentina. Metacercariae were found encysted in the liver and mesentery of experimentally and naturally infected fishes Cnesterodon decemmaculatus and Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Ascocotyle (Leighia) mcintoshi Price 1936 as described by Leigh, 1974, differing in behavior and morphology of cercarial, metacercarial and adult stages.

Descripción: The nature of telencephalic control over premotor and motor circuits is debated. Hypotheses range from complete usurping of downstream circuitry to highly interactive mechanisms of control. We show theoretically and experimentally, that telencephalic song motor control in canaries is consistent with a highly interactive strategy. As predicted from a theoretical model of respiratory control, mild cooling of a forebrain nucleus (HVC) led to song stretching, but further cooling caused progressive restructuring of song, consistent with the hypothesis that respiratory gestures are subharmonic responses to a timescale present in the output of HVC. This interaction between a life-sustaining motor function (respiration) and telencephalic song motor control suggests a more general mechanism of how nonlinear integration of evolutionarily new brain structures into existing circuitry gives rise to diverse, new behavior. © 2013 Goldin et al.

Descripción: Medical and biochemical analysis were performed on 58 patients with chronic alcoholism. In accordance with medical characterisation, patients were divided in three groups: A (patients having only hepatopathy), B (patients with hepatopathy and neuropathy) and C (patients having only alcoholic neuropathy). Simultaneously, several parameters related to heme biosynthesis were examined. Urinary delta-aminolevulic acid (ALA), porphobilinogen (PBG) and porphyrins and fecal porphyrins measurements did not show significant difference among all studied groups. The activities of ALA-dehydratase (ALA-D), uroporphyrinogen-I-synthase (URO-I-S) and uroporphyrinogen-III-synthase (URO-III-S) were monitored in peripheral erythrocytes. From the enzymes measured, only ALA-D levels in groups B and C were significantly depressed (p < 0.002) compared with normal subjects. The decrease in ALA-D correlated with the degree of neuropathy.

Descripción: The electroencephalogram (EEG) together with electromyogram (EMG) of the ischiocavernosus, bulbocavernosus and levator penis muscles were chronically monitored across behavioral states of the armadillo Chaetophractus villosus. This animal has a very long penis, which exhibits remarkable phenomena during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS). During W it remains retracted within a skin receptacle. During SWS penile protrusion can be observed together with very complex movements. Protrusion is a non erectile event during which the penis remains out of its receptacle but without rigidity. Penile erections are observed only during SWS. Contrasting with other mammals, no erections occur during PS. During this phase the penile muscles share the atonia of the body musculature characteristic of that phase. Some reflections on mechanisms of those penile events are presented.

Descripción: Stenurus globicephalae Baylis et Daubney, 1925 (Nematoda: Pseudaliidae) was found in the cranial air sinuses of a false killer whale, Pseudorca crassidens (Owen), stranded on the coast of Uruguay in 1999. Although this species has been reported once in P. crassidens from the North Atlantic, this is the first record for South America. A total of 920 specimens were obtained, of which 663 were females (body length: 4.34 ± 0.45 cm) and 257 were males (2.99 ± 0.18 cm). Morphometric details are presented for S. globicephalae in this host, which do not show significant differences from those parasitizing Globicephala melas (Traill), but are distinct from those parasitizing Peponocephala electra (Gray), The host's skull revealed loss of osseous mass with the disappearance of the left zygomatic arch, and the left jaw had three osseous fenestrations in the region related to the organ of acoustic reception. These lesions support the hypothesis that this infection, known as stenurosis, was related to the stranding.

Descripción: Insects in general, and Drosophila in particular, are much more capable of surviving anoxia than vertebrates, and the mechanisms involved are of considerable biomedical and ecological interest. Temperature is likely to strongly affect both the rates of damage occurring in anoxia and the recovery processes in normoxia, but as yet there is no information on the effect of this crucial variable on recovery rates from anoxia in any animal. We studied the effects of temperature, and thus indirectly of metabolic flux rates, on survival and recovery times of individual male Drosophila melanogaster following anoxia and O2 reperfusion. Individual flies were reared at 25° and exposed to an anoxic period of 7.5, 25, 42.5 or 60?min at 20, 25 or 30°. Before, during and after anoxic exposure the flies' metabolic rates (MRs), rates of water loss and activity indices were recorded. Temperature strongly affected the MR of the flies, with a Q10 of 2.21. Temperature did not affect the slope of the relationship between time to recovery and duration of anoxic exposure, suggesting that thermal effects on damage and repair rates were similar. However, the intercept of that relationship was significantly lower (i.e. recovery was most rapid) at 25°, which was the rearing temperature. When temperatures during exposure to anoxia and during recovery were switched, recovery times matched those predicted from a model in which the accumulation and clearance of metabolic end-products share a similar dependence on temperature. ©2011. Published by The Company of Biologists Ltd.

Descripción: This study documents differences in the courtship behavior of wild strains of Ceratitis capitata (Wiedemann) from Madeira (Portugal), Hawaii (U.S.A.), Costa Rica, and Patagonia (Argentina). Some traits showed large variations and others substantial overlaps. The angle at which the male faced toward the female at the moment of transition from continuous wing vibration and intermittent buzzing changed very little during the course of courtship in all strains, but males from Madeira tended to face more directly toward the female than other males. Females tended to look more, and more directly, toward the males as courtship progressed in all strains. The distance between male and female tended to decrease as courtship proceeded in all strains, but the distances at which males initiated continuous vibration, intermittent buzzing, and jumped onto the female were relatively less variable between strains, except for the strain from Costa Rica. Flies of Madeira courted for longer and the male moved his head and buzzed his wings longer than the other strains.