Influence of Meloidogyne incognita on Resistant and Susceptible Sweet Potato Cultivars

Effects of several population densities ofMeloidogyne incognita on the sweet potato cultivars Centennial (susceptible) and Jasper (moderately resistant) were studied. Field plots were infested with initial levels (Pi) of 0, 10, 100, 1,000, 5,000, and 10,000 eggs and juveniles/500 cm³ soil in 1980 and 0, 100, 1,000, 2,000, 3,000, 4,000, and 5,000 in 1981. M. incognita population development trends were similar on both cultivars; however, at high Pi, more eggs and juveniles were recovered from Centennial than from Jasper. The highest Pi did not result in the highest mid-season (Pm) counts. Pi was negatively correlated with the number of marketable roots and root weight but positively correlated with total cracked roots, percentage of cracked roots, and cracking severity. Jasper tolerated higher Pi with greater yields and better root quality than Centennial. Cracking of fleshy roots occurred with both cultivars at low Pi.     

Floret specialization, seed production and gender in Artemisia vulgaris L. (Asteraceae, Anthemideae)

Flowering and fruiting behaviour of female and hermaphrodite florets is described and assessed in samples from three populations from Denmark, England and Sweden. Between 25 and 50% of the florets in capitula are female, and flowering gender varies little among plants in each population. Fruiting gender of individuals, G (femaleness), varies from 0 to 0.85, because of variation in fruit set and fruit abortion. Variation in fruiting gender was correlated with plant size parameters in two populations, but not in the third. The data suggest that post-anthesis regulation of maternal investment may be operating. Florets of A. vulgaris are either totally specialized for pollen receipt (female florets) or largely specialized for pollen donation (hermaphrodite florets), and show adaptations for avoiding interference with each other in these functions. Movement of capitula from a pendent position at flowering to an erect position at fruiting optimizes positions for dissemination of pollen and of seeds respectively.     

Parasitism byEphedrus cerasicola [Hym.: Aphidiidae] developing in different stages ofMyzus persicae [Hom.: Aphididae]

The parasitoidEphedrus cerasicola Stary oviposited in the 4 nymphal instars and in newly moulted apterous adults ofMyzus persicae (Sulzer). Development and reproduction of unparasitized and parasitized aphids at 21°C were compared. Unparasitized aphids developed to adults in 6.5 days and started to reproduce after 7 days. Longevity varied between 7 and 42 days. Net reproductive rate (R₀) was 40.7. In contrast to older nymphs, aphids parasitized in the 1 st instar almost never reached the adult stage before mummification. Aphids parasitized in 2nd, 3rd and 4th instar and as newly moulted adults produced respectively 0.07 %, 2 %, 23 % and 32 % of offspring produced by unparasitized aphids. Corresponding reproductive periods were 1, 1.4, 3 and 4 days. Host age at parasitization had a slight effect on the parasitoid's developmental rate and had no effect on egg or pupal survival, or on the sex ratio of the emerging parasitoids.     

Effects of Pratylenchus zeae and Quinisulcius acutus Alone and in Combination on Sorghum

Host-parasite relationships of Pratylenchus zeae and Quinisulcius acutus, alone or in combination, were studied on sorghum in the greenhouse and laboratory. Q. acutus at 1,000 or 5,000 nematodes per 15-cm-d pot and P. zeae at 500 nematodes per pot significantly suppressed plant height and fresh and oven dry shoot and root weights. A mixture of 1,000 Q. acutus and 500 P. zeae per pot resulted in greatest suppression of growth. Roots of plants inoculated with Q. acutus alone were reduced in number and size and showed lesions and discoloration. Reproduction of this nematode 42 days after inoculation was much greater in treatments of 100 or 1,000 than 5,000 nematodes. The population density of the two species at 6 weeks after inoculation was significantly less when combined than for each species alone. When the two species were combined, reproduction of P. zeae was greater than that of Q. acutus, but the final populations per gram of root weight were the same. Q. acutus fed ectoparasitically on epidermal cells of sorghum roots in the zone of elongation and differentiation when observed under in vitro conditions.     

Differential winter mortality and seasonal selection in the polymorphic ladybird Adalia bipunctata (L) in the Netherlands

Seasonal selection acting on the melanic polymorphism in the two-spot ladybird Adalia bipunctata was investigated in The Netherlands. An increase in melanic frequency over the spring-summer reproductive period was quantified. The selective advantage gained by melanics averaged 9%, but significant heterogeneity occurred between populations. Adult hibernation behaviour is described. The beetles when outdoors show a highly clumped distribution both between and within trees. The distribution of the morph classes between aggregations is random. Survivorship in a hibernating cohort (initial n= 1898) on a grid of 70 lime trees near Utrecht was monitored by making three counts over the winter of 1981–1982. Intense selection favouring each melanic morph occurred during December and January. The relative fitness of non-melanics was 0.55 (melanics =1). The discovery of dead beetles in late January (about 5% of total losses) and the absence of spatially density-dependent mortality were consistent with a climatic stress rather than selective predation. The period of selection was associated with very cold temperatures averaging up to 4°C below normal and an overall mortality of nearly 75%. There was no change in morph frequency, near normal temperatures and a lower mortality from February to early April. Examination of groups of nearby trees in late January strongly suggested that similar differential mortality had occurred except on some willows. This difference was probably due to the more protected hibernation sites available on these trees. Samples of hibernating cohorts at three other sites showed no evidence of differential mortality. Laboratory experiments with hibernating beetles found no difference in survivorship or rate of weight loss between starved non-melanics and melanics in temperature regimes with and without periods of adult activity. It is concluded that the intense winter selection on the study limes is probably exceptional. Examination of changes in morph frequency through the annual cycle suggests that at some sites the selection favouring melanics during reproduction is counterbalanced by selection against melanics in late summer or early autumn. The results are discussed in relation to mathematical models of cyclical selection and to other field studies including that of Timoféeff-Ressovsky (1940), who found large decreases in melanic frequency during hibernation in Berlin.     

Notes on Algerian aquatic fungi: Pythium pythioides

Pythium pythioides (Roze & Cornu) Ramsbottom is recorded from Algeria. Since its original discovery in 1869 this species had not been found back. A brief history is given and morphological and reproductive characters are discussed.     

In vitro culture of the strobilar stage of Echinococcus granulosus from protoscoleces of human, camel, cattle, sheep and goat origin from Kenya and buffalo origin from India

Protoscoleces from human, camel, cattle, sheep, goat (all from Kenya) and buffalo (from India) hydatid cysts were cultured under identical conditions in vitro using the diphasic culture system of Smyth (1979b). Organisms from all sources grew and segmented in culture. Genital anlagen developed in all cultured worms but further genital differentiation occurred only in cultures of cattle (testes) and camel (testes and genital pore) material. The possible significance of these results is discussed in relation to the general epidemiology of hydatid disease and the potential infectivity of the different strains to man.     

Reproduction and social rank in female stumptail Macaques (Macaca arctoides)

Reproductive physiology was studied in female stumptail macaques. Initially the monkeys were housed indoors (individually and in small groups) and later as one large (92 individuals) social group in an outdoor cage. Most data were collected during the 4-year outdoor period. Plasma progesterone determination in blood samples taken at weekly intervals allowed estimation of ovulation and conception dates. The age at first ovulation (X =3.73 years) was positively correlated with body weight at 3 years of age. The average age at first birth was 4.90 years. Gestation lengths averaged 176.6 days. Following a live birth ovulations returned after a mean interval of 11 months but following an abortion or still birth this interval was 1 month. Usually a number of ovulatory cycles (X =2.37) preceded a conception. Interbirth intervals (IBIs) in the outdoor cage (X =619.4 days) were significantly longer than IBIs during the indoor period (X =523.1), because indoors the infants were weaned at the age of 7 months, while outdoors weaning occurred more naturally. IBIs following abortions or still births (X =291.9 days) were significantly shorter than IBIs following live births. Age at first ovulation, age at first birth, IBIs, and infant production rates were not correlated with dominance rank. Ovarian cycle lengths (X =30.2 days, mode = 28 days) were comparable to previously reported data from laboratory-housed stumptails. No systematic seasonal fluctuations were found in the onset of sexual maturity, in ovarian cycle lengths, in copulation frequencies, and in distribution of births.     

Effects of steroid hormones on the neuropil of the hypothalamic paraventricular nucleus of male chickens

Summary Testosterone and corticosterone, administered in doses of 0.5 mg/day for two weeks to three-day-old male chickens, induced alterations in the distributional pattern and in the number of synapses in the rostral neuropil of the hypothalamic paraventricular nucleus. This avian nucleus is a target area for both above-mentioned hormones and also one of the most important centers involved in the regulation of behavioral patterns related to reproduction. Testosterone increased the number of synapses in the rostral paraventricular nucleus, while corticosterone altered their distributional pattern causing an increase in type-B terminals; according to morphological criteria the latter are regarded to represent aminergic endings. Similar results were induced by simultaneous administration of both testosterone and corticosterone. Precocious sexual behavior was also provoked by double treatment.Preliminary results have been presented on the occasion of the 5th ENA meeting (Liège, Belgique, Sept. 1981) and the 1st Italian Meeting of Cell Biology (Rimini, Italy, April 1982)This study was supported by CNR bilateral grants (82.00215.04 & 83.00492.04), MPI 40% and European Training Program in Brain and Behaviour Researchs (twinning grant)     

Absence of sexual dimorphism in the goat: Induction of luteinizing hormone discharge in the castrated male and female and in the intersex with estradiol benzoate

Gonadectomized male (n = 5) and female (n = 5) and intact intersex goats (n = 2) were injected i.m. with 50 mug 17(beta)-estradiol benzoate (EB). After treatment, there was a transient 6- to 9-hr decrease in circulating levels of LH followed by a preovulatory-like discharge of LH in all goats. Release peaked at 12 to 18 hr after EB treatment. The magnitude of discharge and the time from treatment until peak of release were not influenced by the goat's sex. These findings suggested that the positive feedback effects of estrogen on LH release were not sexually differentiated in the goat. Since tonic concentrations of LH prior to EB treatment were not different among the groups, the studies also suggested that the intersex goats lacked the inhibitory gonadal influences on gonadotropin release that characterize intact animals.