Age structure, growth and reproduction of Leuciscus pyrenaicus in an intermittent stream in the Guadalquivir river basin, southern Spain

The age, growth and reproduction of Leuciscus pyrenaicus (Günther, 1868), an endemic cyprinid from the Iberian Peninsula, was studied from November 1987 to September 1989 in a small seasonal tributary of the Guadalquivir river basin. Maximum fork lengths observed were a 160 mm male with six scale annuli and a 171 mm female aged 7 +. Maximum ages observed were 7 + in males and 8 + in females. There were no significant differences in the annual growth increments between sexes. Seasonal growth period started in March and continued for 5 to 6 months. Mean lengths of 1 + specimens onwards diminished during summer and/or autumn. Males and females matured in their third and fourth year of life respectively. The overall sex ratio (272 males: 310 females) differed significantly from equality. Spawning began in May and ended in July. L. pyrenaicus is a multiple spawner that releases a minimum of two batches of eggs per female each year. Eggs in each batch were similar in both size (egg diameter) and number released. The relationship between fecundity (Fee) and fork length (mm) was represented by the formula: Fec=1.96 10⁻³ L^2.50.     

Life-history parameters of western flower thrips on susceptible and resistant cucumber genotypes

The life-history parameters reproduction rate, developmental time and age specific survival of the western flower thrips,Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae], were determined on susceptible and resistant cucumber (Cucumis sativus L.) genotypes. Both newly emerged andF. occidentalis females of mixed ages showed a substantial reduction (36 to 50%) of the reproduction rate on all resistant genotypes, in particular after the second day. On the resistant genotypes 9127 and 9140,F. occidentalis had a prolonged developmental period. This was primarily due to a prolongation of the second larval stage. On all resistant genotypes,F. occidentalis suffered from high (82 to 97%) preadult mortality, predominantly at the second larval stage. It is conclude that the resistant genotypes do not cause an immediate intoxication of adult nor preadult thrips stages.     

Age structure,growth and reproduction ofRutilus lemmingii in an intermittent stream of the Guadalquivir river basin,southern Spain

The age, growth and reproduction ofRutilus lemmingii (Steindachner, 1866), an endemic cyprinid from the Iberian Peninsula, was studied for over a period of two years in a small seasonal tributary of the Guadalquivir river basin. Approximately 65 % of the total growth in length occured in the first year of life. Males reached a maximum age of 3+ yr (Fork Length, F.L. = 114 mm) and females 4+ yr (F.L. = 144 mm). Both sexes matured during their second year of life (1 +). The overall sex ratio (334 males to 389 females) differed significantly from unity. Somatic condition decreased markedly during the reproductive period of March to May.R. lemmingii is a multiple spawner and releases two batches of eggs per female each year. Mean egg diameter of the first batch was larger than the second one. The regression between fecundity and Fork Length (mm) was: Fec = 0.014 F.L.Z.^2.858 Compared with available information, thisR. lemmingii population, located at a lower latitude, is characterized by fast growth, early maturity, high level of reproductive effort, and a short life-span. These life-history characteristices are typical of species in unstable environments, where adult mortality is high, variable or unpredictable.     

Effect of Temperature on Pratylenchus penetrans Development

Reproduction and development of Pratylenchus penetrans were studied on genetically transformed ladino clover roots. Solitary females developing on transformed roots in nutrient gellan gum medium (pH 5.5) deposited 1.2, 1.5, 1.6, 1.8, and 2.0 eggs per day at the respective temperatures of 17, 20, 25, 27, and 30 °C. The number of eggs deposited was highly correlated with temperature. A reduction in egg-laying rates at the start of hatching was observed at all temperatures. Juvenile mortality was higher at 17 °C (50.4%), 20 °C (50.3%), and 30 °C (58.4%) than at 25 °C (34.6%) and 27 °C (37.6%). Life-cycle (egg deposition to egg deposition) duration was 46, 38, 28, 26, and 22 days at the respective temperatures. The developmental zero degrees (°C) and the effective accumulative temperatures (degree-days) required for hatching, female emergence, and onset of oviposition (completion of one generation) of P. penetrans were estimated to be 2.7 and 200, 4.2 and 548, and 5.1 and 564, respectively. Pratylenchus penetrans reproduces over a wide range of temperatures.     

Non-invasive monitoring of ovarian function in several felid species by measurement of fecal estradiol-17β and progestins

An extraction and assay procedure to measure fecal estradiol-17β and progestin concentrations in several cat species was developed and validated for use for noninvasive monitoring of ovarian function. Fecal samples were collected over a range of 3–20 months from female tigers (three), lions (three), snow leopards (three), cheetahs (two), caracals (two), and domestic cats (five). Samples were extracted with 90% methanol, lipids removed with petroleum ether, and the estradiol and progestins in the methanol measured by radioimmunoassay (RIA). High Performance Liquid Chromatography (HPLC) fractionation and subsequent RIA of the fractions indicated that the estradiol-17β antiserum cross-reacted primarily with estradiol-17β in the feces of lions and tigers and was assumed to be specific for estradiol-17β in the feces of other species as well. However, there were several immunoreactive compounds, presumably progesterone metabolites, excreted in the feces which varied both quantitatively and qualitatively among species. The behavior of tigers, lions, cheetahs, and caracals was visually monitored during the collection period and frequency of sexual behaviors was positively correlated with increases in fecal estradiol in all species observed. The mean fecal estradiol-17β peaks were as follows: tigers, 128.0 ± 13.1; lions, 186.0 ± 14.8; snow leopards, 136.7 ± 15.9; cheetahs, 140.9 ± 9.0; caracals, 24.5 ± 4.0; and domestic cats 158.9 ± 19.3 ng/gm. Fecal progestin concentrations rose significantly (P < 0.001) only after breeding or during pregnancy and were as follows: tigers, 5.6 ± 0.6; lions, 1.9 ± 0.1; cheetahs, 8.4 ± 1.1; and caracals, 2.4 ± 0.4 μg/gm. Fecal progestins were elevated for one-half to two-thirds of the gestation length during presumed pseudopregnancy but remained elevated throughout successful pregnancies. These results suggest that ovarian function can be monitored noninvasively in the family Felidae by the measurement of fecal estradiol-17β and progestin concentrations. © 1995 Wiley-Liss, Inc.     

Aphid growth and reproductive rates

Aphid size, although generally a good indicator of fecundity is not a good indicator of aphid performance over a wide range of conditions. In general, the greater the mean relative growth rate (MRGR) of apterous morphs of Rhopalosiphum padi (L.), the greater their fecundity. Intrinsic rate of increase (r_m) is even more closely correlated with mean relative growth rate than fecundity.Once these criteria are quantified for a morph of a particular species of aphid over a range of conditions the morphs intrinsic rate of increase on a particular host can be estimated by a quick measure of its mean relative growth rate.

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Résumé La taille des pucerons, bien que considérée généralement comme un bon indice de la fécondité, n'est pas un bon indice pour leurs performances dans une grande gamme de conditions. En général, plus le taux moyen de croissance relative est élevé chez les types aptères de Rhopalosiphum padi, plus leur fécondité est importante. Le taux intrinsèque de croissance (r_m) est encore plus étroitement lié au taux moyen de croissance relative que la fécondité.Une fois que ces critères ont été quantifiés pour un type d'une espèce donnée de puceron dans une gamme de conditions, les taux intrinsèques de croissance des différents types sur un hôte particulier peuvent être estimés par une mesure rapide de leur taux moyen de croissance relative.

     

Metabolism of activated oxygen in detached wheat and rye leaves and its relevance to the initiation of senescence

Pollen grains of Plumbago zeylanica L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and organelle content. The larger of the two sperm cells (S_vn) is distinguished by the presence of a long (approx. 30 m) projection, which wraps around and lies within embayments of the vegetative nucleus. This cell contains numerous mitochondria, up to two plastids and, infrequently, microbodies. It is characterized by a larger volume and surface area and contains a larger nucleus than the other sperm cell. The second sperm cell (S_ua) is linked by plasmodesmata with the S_vn, but is unassociated with the vegetative nucleus. It is smaller and lacks a cellular projection. The S_ua contains relatively few mitochondria, but numerous (up to 46) plastids and more microbodies than the other sperm. The degree of dimorphism in their content of heritable cytoplasmic organelles must at fertilization result in nearly unidirectional transmission of sperm plastids into just one of the two female reproductive cells, and preferential transmission of sperm mitochondria into the other.Abbreviations S_ua sperm cell unassociated with the vegetative nucleus - S_vn sperm cell physically associated with the vegetative nucleus 1=Russell and Cass (1981)     

Selected aspects of collared peccary (Dicotyles tajacu) reproductive biology in a captive texas herd

Collared peccaries (Dicotyles tajacu) from 32 litters were born in captivity during the period from September, 1981 through July, 1983. Incidence of singleton, twin, and triplet litters was 28%, 66%, and 6%, respectively. Mean (± SE) weight of young from singleton, twin, and triplet litters was 751 (± 35) gm, 698 (± 17) gm, and 612 (± 74) gm, respectively. Sex ratio among all litters was 56:44 (M:F). Neonatal mortality amounted to 9% of the young born. Mean duration of estrus was 2.60 days and mean length of gestation was 145.6 days. Evidence indicated that multiple copulations increased ovulation rate and the chance for conception.     

ÜberHydrianum viride (Characiaceae,Chlorophyceae), seine fortpflanzung und taxonomie

The little known epiphytic algaHydrianum viride was studied and pictured. The morphology and the variability of the vegetative cells are described in detail and compared with the observations of other authors. For the first time typical biflagellate zoospores of the chlorophycean-type have been recognized and the course of the asexual reproduction is studied. The residual protoplasm, that is the proximal half of the zoosporangium protoplast, growth up to the original size, typical for the genusHydrianum. The life cycle, especially the settling down of the zoospores, is described.Hydrianum viride belongs to the characteristic inhabitants of peaty waters; it belongs together with the host alga,Microspora loefgrenii, to the dominants of algal association of peat-springs. At last the taxonomic position and the synonyma of this organism are discussed.