Ovarian development rates in the Old World screw-worm fly, Chrysomya bezziana

Rates of ovarian development in relation to temperature were determined for autogenous females of the screw-worm fly, Chrysomya bezziana. Percentage durations of the different ovarian stages (scaled 2–10) were estimated on the basis of observed lengths of the developing oocytes. Mean durations (h) of each ovarian stage was determined at 20, 25, 28 and 35°C. A model of ovarian development rate (%/d) in relation to temperature (T) is presented, the fitted curve being give by R(T)=EXP (–2.73+0.362T–0.0055T²).     

Influences of temperature, fly size and protein-feeding regime on ovarian development rates in the Australian bush fly, Musca vetustissima

A reproductive age-grading system is presented for female Musca vetustissima based on length and yolk content of developing follicles. Ovarian development rate models are also presented for estimating reproductive and chronological ages of females under laboratory and field conditions. Maturation rates are determined primarily by temperature, but are also influenced by protein-availability and fly size (adult headwidth). Females of average size (2 mm headwidth) require 70 and 38 day degrees above 8°C respectively to mature their first and subsequent egg complements. Under suboptimal protein-feeding regimes in the laboratory, females experienced variable periods of arrested development prior to vitellogenesis. These females also resorbed part of their egg complements, but their ovarian development rates were unaffected by oocyte resorption. Under field conditions, females develop their ovaries at near expected rates, requiring only 5 and 2 day degrees more than expected, repectively, to complete their first and each subsequent ovarian cycle.

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Résumé Une échelle de classement est élaborée d'après l'âge des femelles de Musca vetustissima, en se basant sur la longueur et la teneur en vitellus des follicules en croissance. Des modèles de développement ovarien sont proposés pour évaluer les âges chronologique et reproductif, dans les conditions de laboratoire et de la nature. La vitesse de maturation est déterminée avant tout par la température, mais elle est aussi influencée par la disponibilité en protéines et la taille de l'adulte (largeur de la tête). Des femelles de taille moyenne (2 mm de largeur de tête) ont besoin de 70 et 38 degrés/jours au-dessus de 8°C pour conduire successivement à maturité leur premier et leur second lots d'oeufs. Au laboratoire, avec une alimentation protéique inférieure à l'optimum, le développement des femelles est interrompu pendant des durées variables avant le début de la vitellogenèse. Ces femelles résorbent aussi une fraction de leur lot d'oeufs, mais les vitesses de développement ovarien n'ont pas été modifiées par cette résorption. Dans la nature, le développement ovarien s'effectue à peu près à la vitesse prévue, demandant seulement 5 jours de plus que les prévisions pour accomplir leur premier cycle ovarien, et ensuite 2 jours de plus que prévu pour accomplir chaque cycle supplémentaire.

     

Reversible cytoplasmic rearrangements precede wall apposition,hypersensitive cell death and defense-related gene activation in potato/Phytophthora infestans interactions

We used video microscopy techniques as a tool for live examination of the dynamic aspects of plant/fungus interactions. Early, dynamic responses of epidermal midrib cells of leaves from a potato cultivar (Solanum tuberosum L. cv. Datura) carrying resistance gene R1 to Phytophthora infestans (race 1: compatible interaction, race 4: incompatible interaction) were monitored. Similar responses were observed in both types of interaction, ranging from no visible reaction of invaded plant cells to hypersensitive cell death. The overall defense response of each individual cell exhibited a highly dynamic behavior that appeared to be tightly coordinated with the growth of the fungus. Initial localized reactions, including major rearrangements within the cytoplasm, occurred directly at the fungal penetration site, where rapid apposition of autofluorescent material and callose took place. If fungal invasion stopped at this stage, the host cell restored its normal cytoplasmic activity and survived. Hypersensitive cell death occurred only when fungal growth had proceeded to the formation of a clearly identifiable haustorium. In such cases, cytoplasm and nucleus conglomerated around the intracellular fungal structure, followed by a sudden collapse of the whole conglomerate and an instantaneous collapse of the fungal haustorium. Only small quantitative differences between the compatible and incompatible interactions of the two fungal races were observed for these early responses of epidermal cells. In the incompatible interaction, a slightly larger number of epidermal cells responded to fungal attack. More pronounced quantitative differences between compatible and incompatible interactions occurred upon fungal invasion of the mesophyll. These differences in the number of responding cells were not reflected at the level of gene expression: the spatial and temporal activation patterns of two defense-related genes, encoding phenylalanine ammonia-lyase and pathogenesis-related protein 1, were similar in both types of interaction.Dedicated to Professor Peter Sitte, Freiburg, Germany, on the occasion of his 65th birthday     

Interactions among leaf photosynthetic rates,flowering and pod set in soybeans

The seasonal maximum in photosynthetic CO₂ exchange rate (CER) and the cessation of leaf expansion in soybeans (Glycine max (L.) Merr) accompany fruiting under normal agricultural conditions. To investigate whether these phenomena were obligatively tied together, we caused early flowering of long-season varieties by imposing artificial short-day treatments. Comparisons of CER and leaf area between vegetative (long-day treatment) and fruiting (short-day treatment) plants of long-season cultivar confirmed the relationship of these phenomena. The same comparisons made between a long-season and a short-season cultivar, both at the same daylength, also confirmed the relationship.     

Light,leaf age,and leaf nitrogen concentration in a tropical vine

Summary Tropical vines in the Araceae family commonly exhibit alternating periods of upward and downward growth, decoupling the usual relationship between decreasing light environment with increasing age among the leaves on a shoot. In this study I examined patterns of light, leaf specific mass, and leaf nitrogen concentration in relation to leaf position, a measure of developmental age, in field collected shoots of Syngonium podophyllum. These data were analyzed to test the hypothesis that nitrogen allocation parallels within-shoot gradients of light availability, regardless of the relationship between light and leaf age. I found that leaf nitrogen concentration, on a mass basis, was weakly correlated with leaf level light environment. However, leaf specific mass, and consequently nitrogen per unit leaf area, were positively correlated with gradients of light within the shoot, and either increased or decreased with leaf age, providing support for the hypothesis that nitrogen allocation parallels gradients of light availability.     

Studies on the age and growth of the bata,Labeo bata (Ham.) (Cyprinidae,Teleostei) from the river Kali,India

Age and growth of Labeo bata (Ham.) was studied by the analysis of annuli found on the scale and by length-frequency distribution. The fish attained lengths of 131, 194, 236, 277, 314, 341 and 364 mm at the end of the 1st, 2nd, 3rd, 4th, 5th, 6th and 7th years of life respectively. The increase in length of scale bears a constant relationship with the increase in length of fish, and regression analysis yielded a straight line between scale and body length. Calculated values could be expressed as: Y = –2.534 + 0.064 XThe growth rate of the fish was found high during the 1st and 2nd years and decreased gradually afterwards till the 7th year. Both sexes showed more a or less similar growth rate and attained a similar longevity. Growth trend of the fish confirmed the von Bertalanffy growth equation: Lt = 450(l–e^{–0.2165(t+0.5963))} The seasonal growth curve was chiefly influenced by feeding intensity in fishes of 1st year class while in adults it was affected by feeding intensity as well as by maturation of the gonads.     

Dominance,age, and reproductive success in free-ranging female hanuman langurs (Presbytis entellus)

Correlations among female age, dominance, and reproduction were investigated for a 12-year period in free-ranging, provisioned Hanuman langurs (Presbytis entellus), living in one-male groups near Jodhpur in Rajasthan, India. Of 2940 displacement episodes, 27% occurred over natural food, 26% over provisioned food, 8% over grooming, 23% over position and shade, and 16% for other reasons. It was possible to reconstruct a displacement hierarchy that was linear and stable over short periods but fluctuated according to the age composition of the troop, resulting in an age inversed dominance structure. Females occupied top ranks as soon as they experienced menarche (around 2.4 years of age) and gradually declined thereafter, with postmenopausal females (≥30 years) being the lowest ranking individuals. Old females tended to be peripheral, while young females were highly social and active. Fertility peaked at about 7 years and gradually decreased thereafter, but infant mortality was much higher in young females than in old ones. During years when females gave birth, their ranks, especially those of old females, were higher than the average expectation for their age class, which suggests that females compete more vigorously if they have an infant. Reproductive success (i.e., infant survival to ≥2 years) declined significantly from high-over middle-to low-ranking females but did not differ for the three age classes investigated, because the higher fecundity of young females was balanced by better rearing success of older females. These results are discussed in light of the controversy over whether the langur social system is strongly influenced by kin selection (Hrdy and Hrdy, 1976; Dolhinow et al., 1979).     

The effect of age at mating on the rate of egg laying in the cricket, Teleogryllus commodus

As female crickets, Teleogryllus commodus (Walker) age there is a progressive change in their ability to produce eggs as indicated by the number deposited. Virgin females lay very few eggs (11/week) when only one week old, but the number increases to an average value of 160/week by the age 3, 5 or 7 weeks post imago. There is essentially no change in the number of eggs oviposited when very young (1 week old) or senescent (7 weeks old) females are mated, but there is a dramatic increase in the long term production of eggs when females are mated at middle age (3 and 5 weeks old). The results are correlated with previously published data from this species on the JH III titres of virgin females and females mated at different ages.

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Zusammenfassung Das Altern von T. commodus-Weibchen bringt eine fortschreitende Veränderung in ihrer Eiproduktion mit sich, die sich in der Anzahl von abgelegten Eiern ausdrückt. Während 1 Woche-alte, unbegattete Weibchen wenige Eier (11/Woche) ablegen, steigt ihre Zahl im Alter von 3, 5 oder 7 Wochen auf eine Durchschnittswert von 160/Woche an. Eine Begattung von jungfräulichen Weibchen im Alter von 1 Woche oder 7 Wochen ändert die Anzahl der abgelegten Eier nicht, wogegen sich bei 3–5 Wochen alten Weibchen zu einem dramatischen Anstieg in der langfristigen Eiproduktion führt. Die Ergebnisse sind mit früher publizierten Daten an T. commodus korreliert, die unterschiedliche JH III Titer in unbegatteten und begatteten Weibchen aufzeigten.

     

Predation by vervet monkeys in an outdoor enclosure: The effect of age,rank, and kinship on prey capture and consumption

Sixty-one instances of vertebrate predation have been directly observed or inferred from remains in a captive colony of vervet monkeys (Cercopithecus aethiops sabaeus)over a 6-year period. Vertebrate prey included 33 rodents,27 birds, and 1 frog. Prey capturing was performed predominantly by juvenile males and females, independent of rank. Avian prey were highly preferred: all 27 birds were eaten completely, while only 1 of 33 rodents was consumed completely and 5 others partially. Prey consumption was related to age-sex class, rank, and kinship. All age-sex classes were observed to consume avian prey, but juvenile males and females predominated. Seventy-six percent of all animals noted consuming avian prey were members of the alpha matriline in their group. When two or more animals were observed cofeeding on the same preferred prey item, they were generally members of the same kinship group.     

Temperature-dependent growth rates for the cassava mealybug, Phenacoccus herreni, and two of its encyrtid parasitoids, Epidinocarsis diversicornis and Acerophagus coccois in Colombia

Developmental rates for Phenacoccus herreni Cox & Williams were determined at 18°, 20°, 22°, 25°, 30° and 35°C for the egg, all juvenile male and all juvenile female stadia. Longevity was determined for adult females and adult males. Developmental rates for the P. herreni parasitoid Epidinocarsis diversicornis (Howard) were determined at 18°, 20°, 25° and 30°C for the oviposition-to-mummy-formation period and the mummy-formation-to-adult-eclosion period. Developmental rates were determined for the P. herreni parasitoid Acerophagus coccois Smith for the same two life stages at 20°, 25° and 30°C. Least-squares-derived polynomial equations or logistic equations were fitted to each data set (except for A. coccois) so that rates could be interpolated for temperatures between observed points for use in an analysis of the impact of these parasitoids on population dynamics of P. herreni. Results of this analysis are presented separately.

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Résumé Les vitesses de développement des oeufs et de tous les stades larvaires mâles et femelles de P. herreni Cox & Williams ont été déterminées à 18°, 20°, 22°, 25°, 30° et 35°C. La longévité des adultes mâles et femelles a été déterminée. Les vitesses de développement de la ponte à la formation du cocon et de celleci à l'émergence de E. diversicornis Howard, encyrtide parasite de P. herreni ont été déterminées à 18°, 20°, 25° et 30°C. Il en a été de même pour un second encyrtide parasite A. coccois Smith à 20°, 25° et 30°C. Les équations polynomiales des derniers carrés dérivés et les équations logistiques ont été ajustées pour chaque lot de données (à l'exception de A. coccois) de façon à ce qu'elles aient pu être interpolées pour analyser l'impact de ces parasites sur la dynamique de population de P. herreni. Les résultats de cette analyse sont présentés à part.

     

The influence of oocyte resorption on ovarian development rates in the Australian sheep blowfly, Lucilia cuprina

Rates of ovarian development in L. cuprina are determined by ambient temperatures and females require a minimum of 57 day degrees above 8°C to mature their first complement of eggs. The number of oocytes that a female can mature depends on her size and the amount of protein-rich material ingested. Under field conditions, females usually obtain sufficient protein to reach maturity but rarely mature their full egg complements (Vogt et al., 1985), i.e., most females resorb some of their oocytes. Oocyte resorption prolongs the maturation period by approximately 0.3 day degrees/oocyte resorbed.A model of ovarian development rates is presented which incorporates resorption delays and uses ambient temperature regimes to estimate the physiological ages and maturation rates of field females.

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Résumé Les taux de développement ovarien de L. cuprina sont déterminés par la température ambiante, et la femelle exige un minimum de 57 degrés-jours audessus de 8°C pour développer son premier lot d'oeufs. Le nombre d'ovocytes qu'une femelle peut former dépend de sa taille et de la quantité d'aliments riches en protéines absorbées. Dans les conditions de la nature, les femelles obtiennent normalement suffisamment de protéines pour atteindre la maturité mais rarement l'ensemble de leur contingent d'oeufs se développe totalement, c'est à dire que la majorité des femelles résorbé une partie de ses ovocytes. La résorption des ovocytes prolonge la période de maturation d'environ 0,3 dégre-jour par ovocyte résorbé. Un modèle de taux de développement ovarien est proposé qui incorpore les retards dus à la résorption et utilise les régimes de température ambiante pour évaluer les âges physiologiques et les taux de maturation des femelles dans la nature.

     

Effect of thidiazuron,light fluence rates and kanamycin on in vitro shoot organogenesis from excised Rubus cotyledons and leaves

The relationship between genotype, tissue age and endogenous cytokinin levels on adventitious bud formation on Lachenalia leaf tissue were investigated. The genotypes studied, showed a variation in bud formation. The hybrid explants responded differently to factorial combinations of BA and NAA. The growth regulators could not substitute for the regeneration potential of the genotype. Tissue age had a pronounced effect on regeneration potential. Young tissue formed the largest number of buds. An interaction between tissue age and genotype was detected. Cytokinin levels in young leaf tissue were higher than in older tissue. In young tissue no relationship was observed between the cytokinin level and the number of buds formed. However, in older tissue it appears as if a relatively low endogenous cytokinin level enhanced bud formation.Abbreviations BA benzyladenine - NAA naphthalene-1-acetic acid - Z zeatin - ZR ribosylzeatin     

Relation between size and age of holdfasts of Ecklonia stolonifera Okamura (Laminariales,Phaeophyta) in northern Honshu,Japan

Ecklonia stolonifera is distributed along the coast facing the Sea of Japan. The size of various parts of the shoot (blade length and width and stipe length and diameter) and the age were determined at Ooma, Aomori Prefecture. The smaller the holdfast, the higher the percentage of one-year-old shoots. Holdfasts 10 cm in diameter seemed to be three years old, whereas holdfasts 40 cm in diameter seemed to be five or more years old. Zoosporangial sori were observed on blades three or more years old. Ecklonia stolonifera holdfast diameter expands only vegetatively by stoloniferous rhizoids. Zoospores, formed on shoots three or more years old, serve for the formation of new populations.     

Grazing rates and behaviors of Neocalanus plumchrus: implications for phytoplankton control in the subarctic Pacific

Grazing rates and behaviors of the copepod Neocalanus plumchrus were investigated in shipboard experiments during the first SUPER Program cruise (May, 1984). N. plumchrus can exploit cells in the 2 to 30 m size range with equal clearance efficiency but displays considerable flexibility in responding to changes in concentration and size composition. Its functional response helps to stabilize phytoplankton at low densities. In 60-liter microcosms, a density of one copepod liter^–1 was sufficient to maintain the ambient abundance and structure of the phytoplankton community for a week. In the absence of the copepod, phytoplankton bloomed to unnaturally high levels, and the community composition was dramatically altered. Despite its grazing potential, N. plumchrus was not present in sufficient density to control phytoplankton blooms in the subarctic Pacific. However, the copepod may have an important role in regulating the abundance of smaller grazers and the size structure of the phytoplankton community.Contribution No. 2002 from Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822     

Juvenile settlement,survivorship and in situ growth rates of four species of Caribbean damselfishes in the genusStegastes

Synopsis FourStegastes species were visually censused to determine seasonality and size of juvelines at settlement as well as their survival and growth rates. The census was performed weekly from September 1987 to March 1991 in southwest Puerto Rico. All species had a settlement pulse during September–October. The threespot damselfish,S. planifrons, appeared to have the strongest site fidelity, longest survivorship and slowest growth of the four species. The cocoa damselfish,S. variabilis, and the bicolor damselfish,S. partitus, had similar patterns of site fidelity, life expectancy and growth rates, but these two species differed in being the most and least abundant, respectively. The beaugregory,S. leucostictus, occurred second in abundance but included the least number of new settlers. This species displayed poor site fidelity, a characteristic which probably influenced calculations indicating poor survivorship, life expectancy and growth relative to its congeners. Similarities and differences in these characteristics, as well as in the habitat preferences displayed by these four fishes, may contribute to their abilities to coexist in the same area.     

Relationships between bed age,bed size,and genetic structure in Chesapeake Bay (Virginia,USA) eelgrass (<Emphasis Type="Italic">Zostera marina</Emphasis> L.)

Genetic structure and diversity can reveal the demographic and selective forces to which populations have been exposed, elucidate genetic connections among populations, and inform conservation strategies. Beds of the clonal marine angiosperm Zostera marinaL. (eelgrass) in Chesapeake Bay (Virginia, USA) display significant morphological and genetic variation; abundance has fluctuated widely in recent decades, and eelgrass conservation is a major concern, raising questions about how genetic diversity is distributed and structured within this metapopulation. This study examined the influence of bed age (<65years versus<6years) and size (>100ha versus<10ha) on morphological and genetic (allozyme) structure and diversity within Chesapeake Bay eelgrass beds. Although both morphology and genetic diversity varied significantly among individual beds (F _ST=0.198), neither varied consistently with bed age or size. The Chesapeake eelgrass beds studied were significantly inbred (mean F _IS=0.680 over all beds), with inbreeding in old, small beds significantly lower than in other bed types. Genetic and geographic distances within and among beds were uncorrelated, providing no clear evidence of isolation by distance at the scale of 10's of km. These results suggest that local environmental conditions have a greater influence on plant morphology than do bed age or size. They support the hypotheses that eelgrass beds are established by multiple founder genotypes but experience little gene flow thereafter, and that beds are maintained with little loss of genetic diversity for up to 65 years. Since phenotypic and genotypic variation is partitioned among beds of multiple ages and sizes, eelgrass conservation efforts should maximize preservation of diversity by minimizing losses of all beds.     

The influence of female age on phonotaxis during single and multiple song presentations in the field cricket,Gryllus integer (Orthoptera: Gryllidae)

The influence of age on variation in female phonontaxis in the field cricket,Gryllus integer, was investigated using a Kugel treadmill-type device. Synthetic male calling songs, with different pulse rates, were presented in both single-stimulus and three-stimulus designs. Females were either 11–14 or 25–28 days postecdysis. Females varied in motivation, or the degree of reproductive effort they exhibited, but only in single-stimulus trials: older females achieved higher scores than younger females. Females varied in selectivity, or the extent to which they discriminated among potential mates, in both presentation designs. All females discriminated against atypical pulse rates. In multiple-stimulus trials with normal range pulse rates, younger females were discriminatory; older females were not. Mated females showed reduced phonotaxis and selectivity irrespective of mating interval.     

Growth and age structure of the swan mussel Anodonta cygnea (L.) at different depths in lake Mattsee (Salzburg, Austria)

Unionid clams were collected at 1–2 m, 3–4 m and 6–7 m depth in lake Mattsee, a moderately mesotrophic lake, to investigate the effect of depth on clam growth and age structure. No significant differences in age structure of Anodonta cygnea were found (p=0.65). Three and ten years old clams were present at all depths, but in different percentages. Whereas at 1–2 m 13.3% of the collected clams were <4 years old, this percentage was 4.4% at 6–7 m and 7.1% at 3–4 m. A greater percentage (6.7%) of older mussels (9, 10 years) were collected at 6–7 m than at 1–2 m (2.2%). Growth declined with depth. Total length at a given age of clams at 1–2 m and 3–4 m did not differ (p=0.54), whereas differences were significant between clams at 1–2 m and 6–7 m (p<0.05) as well as between 3–4 m and 6–7 m (p<0.05). The Growth constant k was highest at 1–2 m depth.     

Survival and cause-specific mortality rates of female sika deer in eastern Hokkaido, Japan

Survival and cause-specific mortality rates of female sika deer (Cervus nippon) were studied using radio telemetry in eastern Hokkaido, Japan. We captured and radio-collared 18 female deer, and monitored their survival from April 1993 to May 1996. Estimated annual survival rate for adult females was 0.779 (95% confidence interval was 0.609–0.997). The harvest mortality rate of adult females was higher than the natural mortality rate. Experimental female hunting during 1994–1996 contributed to an increase in the mortality rate for females and was useful in the control of the sika deer population.