Segregation products of male mice doubly heterozygous for the RB(6.16) and RB(16.17) translocations: Influence of sperm karyotype on fertilizing competence under varying mating frequencies

The meiotic segregants of male mice heterozygous for Rb(6.16)24Lub and Rb(16.17)7Bnr were viewed, for the first time, at first cleavage metaphase. Chromosomes were analyzed after G-banding, C-banding, and karyotyping. To study sperm aging effects, chromosomes of 202 one-cell zygotes derived from males mating at intervals of approximately 3,14, and 21 days were examined. At least 89.6% of sperm-derived complements were products of 2:2 segregation; at most, a possible 6.4% were 3:1 segregants. The six expected types of 2:2 segregants, both balanced and unbalanced, were equifrequent in the total zygote population derived from sperm of all ages. When the data were analyzed according to mating frequency, the 3-day sperm population considered most likely to be fresh showed a deficiency of the segregant nullisomic for chromosome 6 and disomic for chromosome 17, when compared with the reciprocal segregant (P < 0.025) as well as to all other 2:2 segregants (P < 0.05). However, these sperm fertilized in greater numbers (P < 0.01) than their reciprocal segregant (disomic for 6 and nullisomic for 17) in the 14-day sperm population. While sperm with chromosomal abnormalities are capable of fertilization, the competence of segregants nullisomic for 6 and disomic for 17 apparently depends on the prior storage period in the male. Further, the results suggest that the effect of aneuploidy on sperm function is dependent on the specific chromosome(s) involved.     

Transformation of sperm nuclei into male pronuclei in nucleate and anucleate fragments of parthenogenetic mouse eggs

Our objective was to examine the ability of nucleate and anucleate fragments of artificially activated mouse eggs to transform sperm nucleus into male pronucleus. To this end, zona-free oocytes in metaphase II were activated by ethanol and bisected into halves (one with the spindle, the other anucleate) either within 10 to 20 min (series A) or 3 or 5 hr later (series B). In series A, the fragments were inseminated 3,5, and 8 h after activation, and in series B. 3 and 5 h after activation. Both nucleate and anucleate fragments lose the capability of transforming sperm nucleus into fully formed pronucleus sometime between 3 and 5 h after activation. In 8 h old parthenogenetic fragments, the majority of sperm nuclei remain unchanged or begin decondensation but never reach the stage of an early pronucleus. In over 1/3 of anucleate fragments of this age group, sperm nuclei develop defectively: chromatin decondenses inside the persisting nuclear envelope. In other experimental groups, the incidence of these abnormal sperm nuclei varies between 0 and 10%. In general, the anuclcate fragments retain the capability to transform sperm nuclei (fully or partially) longer than their nuclear counterparts. This difference may be accounted for by a different level of substances required for pronuclcar growth (extrachromosomal constituents of the germinal vesicle and nuclear lamins): high and constant in the cytoplasm of anucleate egg halves and low and progressively decreasing in the nucleate halves because of their putative uptake by the female pronucleus. However, the cytoplasmic factors responsible for the initial stages of transformation (nuclear envelope breakdown, chromatin decondensation) become eventually inactivated both in the presence and in the absence of a female pronucleus.     

Insect capture and growth of the insectivorous Drosera rotundifolia L.

Summary Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.     

FEMALE CONTROL OF SPERM TRANSFER AND INTRASPECIFIC VARIATION IN SPERM PRECEDENCE: ANTECEDENTS TO THE EVOLUTION OF A COURTSHIP FOOD GIFT

Manipulation of ejaculates is believed to be an important avenue of female choice throughout the animal kingdom, but evidence of its importance to sexual selection remains scarce. In crickets, such manipulation is manifest in the premature removal of the externally attached spermatophore, which may afford females an important means of postcopulatory mate choice. We tested the hypothesis that premature spermatophore removal contributes significantly to intraspecific variation in sperm precedence by (1) experimentally manipulating spermatophore attachment durations of competing male Gryllodes sigillatus and (2) employing protein electrophoresis to determine the paternity of doubly mated females. The relative spermatophore attachment durations of competing males had a significant influence on male paternity, but the pattern of sperm precedence deviated significantly from the predictions of an ideal lottery. Instead, paternity data and morphological evidence accorded best with a model of partial sperm displacement derived here. Our model is similar to a displacement model of Parker et al. in that sperm of the second male mixes instantaneously with that of the first throughout the displacement process, but the novel feature of our model is that the number of sperm displaced is only a fraction of the number of sperm transferred by the second male. Regardless of the underlying mechanism, female G. sigillatus can clearly alter the paternity of their offspring through their spermatophore-removal behavior, and employ such cryptic choice in favoring larger males and those providing larger courtship food gifts. We discuss how female control of sperm transfer and intraspecific variation in sperm precedence may be important precursors to the evolution of gift giving in insects.     

Sperm motility initiation factor is a minor component of the Pacific herring egg chorion

Polyclonal antibodies were generated to the 105 kDa herring sperm motility initiation factor (SMIF) and used to explore the role of SMIF in sperm-egg interaction. Using sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting with SMIF antibodies, it was demonstrated that SMIF is present as a minor (4–7% of total chorion protein) component of the chorion. The major polypeptides in the chorion migrated at 117 kDa and in a grouping between 48–54 kDa, with other minor bands above and below. The only detectable glycosylated component was the 105 kDa band, which was resolved at two isoelectric points (8.22 and 8.31) after isoelectric focusing gel electrophoresis. Using antibodies to SMIF, fertilization was blocked, sperm motility was inhibited in vitro in the presence of solubilized SMIF and SMIF binding sites on sperm were localized. Lastly, SMIF was localized to the region of the herring egg that encircles the micropyle.     

Functional morphology of genitalia of four species of julidan millipedes (Diplopoda: Nemasomatidae; Julidae)

The functional anatomy of the genitalia of Nemasoma varicorne (Nemasomatidae), Brachyiulus lusitanus, Unciger foehdus and Cylindroiulus boleti (Julidae) was investigated by shock freezing of animals in copula followed by serial semithin sectioning of the engaged genitalia. The species show conspicuous differences in the functional mechanism of their genitalia. In M varicorne and B. lusitanus the vulvae remain within the vulval sac during copulation while in U.foetidus and C. boleti parts of the gonopods (promerite and mesomerite) form clasper-like structures that pull out the vulvae from the vulval sacs. With the exception of C. boleti all investigated species have a 'central funnel' on the vulva which leads into the receptaculum seminis. The sperm-transferring part of the male gonopods (solenomerite) is introduced into this funnel during copulation. In B. lusitanus and C. boleti a projection of the posterior gonopods (end-projection, brachite) fits into a slit anterior to the openings of the receptacula. The results are discussed with regard to sexual selection theory and a hypothesis is proposed that explains the evolutionary change of millipede genitalia by a combination of female choice and sperm competition phenomena.     

The association of proctolin with a ventral abdominal muscle of Locusta migratoria

The association of proctolin with the external ventral protractor muscle of the VIIth abdominal segment (M234) of Locusta migratoria was investigated using immunohistochemistry and RP-HPLC in conjunction with the sensitive locust oviduct bioassay. Immunohistochemistry of whole-mount tissues revealed two proctolin-like immunoreactive axons in N2B_2b1 (the nerve branch which innervates M234) as well as immunoreactive processes and varicosities on the surface of M234. Immunogold staining of M234 demonstrated that the proctolin-like immunoreactivity was present in electron-dense granules in its motor terminals. A material indistinguishable from proctolin and with proctolin-like bioactivity co-eluted with authentic proctolin on two different RP-HPLC systems. Bath application of proctolin at concentrations greater than 10^-11 M resulted in a dose-dependent increase in the neurally-evoked fast twitch amplitude and duration of M234. Concentrations greater than 10^-9 M resulted in a dose-dependent increase in basal tonus of M234. These results indicate that proctolin, or a peptide very similar to proctolin, is present in the motor innervation of M234 and acts as a cotransmitter and/or neuromodulator at this typical fast skeletal muscle.Abbreviations M234 external ventral protractor muscle of the Vllth abdominal segment - RP-HPLC reverse-phase high pressure liquid chromatography - TFA trifluoroacetic acid     

Energy detection and temporal integration in the noctuid A1 auditory receptor

The temporal integration of the A1 auditory receptor of two species of noctuid moths (Lepidoptera, Noctuidae) was investigated. Tympanal nerve spikes were recorded while stimulating the ear with broad band clicks. Thresholds were measured for single clicks, pairs of clicks with a separation of 1–20 ms, and trains of up to 8 clicks at separations of 1–2 ms. The average threshold for single clicks was 52.9 dB peSPL (SD 1.7 dB, n = 40) for Noctua pronuba and 50.1 dB peSPL (SD 4.0 dB, n = 27) for Spodoptera littoralis. The thresholds for double clicks with a 1 ms separation were lower than the thresholds for single clicks. The difference decreased as the separation between the clicks was increased. The results were fully consistent with an energy detector model (a leaky integrator with an exponential decay) with a time constant of about 4 ms.The results are compared to previously published results with pure tone intensity/duration trading. A common underlying mechanism is suggested, based on the passive electric properties of the receptor cell membrane.It is suggested, that the time constant revealed in the present study characterizes auditory receptors in general, and is related to the short time constants in vertebrate audition.Abbreviations peSPL peak equivalent sound pressure level - SD standard deviation - time constant     

Causal connection between detoxification enzyme activity and consumption of a toxic plant compound

Insect herbivores can increase their detoxification activities against a particular plant poison in response to prolonged ingestion of the same compound. For example, larval tobacco hornworms (Manduca sexta) experience a dramatic increase in cytochrome P450 activity against nicotine after ingesting nicotine. While it is generally assumed that this induction process permits increased consumption of toxic plant tissues, we are not aware of any direct experimental support for this assumption. Using a two-tiered approach, we examined the functional significance of P450 induction to M. sexta larvae ingesting a toxic but non-deterrent concentration of nicotine. First, we related the time-course of P450 induction in midgut microsomes to changes in nicotine consumption. When offered a nicotine diet, larvae failed to show a significant increase in consumption before 36 h, which was coincident with the time-course of the induction of midgut P450 activities against aldrin and nicotine. Second, we determined whether inhibiting the induced P450 activities affected nicotine consumption. We found that the increase in nicotine consumption following the induction of nicotine metabolism could be strongly inhibited by treatment with piperonyl butoxide, which by itself did not inhibit consumption. These results provide direct evidence for a causal connection between P450-mediated detoxification activity and consumption of a toxic plant compound.Abbreviation PB piperonyl butoxide     

华北棉区夏播棉田害虫发生特点分析

分析和比较了华北棉区夏季播种与春季播种的棉田主要害虫（棉铃虫与棉蚜）的发生特点,探讨了它们的管理对策。