Population dynamics of pedigree leopards,Panthera pardus ssp,in captivity

The demographic history of 4 races or subspecies of leopard, Panthera pardus, was reviewed from international studbook records dating back to 1953. The Chinese leopard has been the most common pedigree race maintained in captivity, a factor linked to the length of time (29 years) this subspecies has been in captivity. The relative youth of the wild-born founders also helped them to adjust to captivity as well as live long reproductive lives. Today, however, this race is suffering from the ill effects of inbreeding due to the small founder size. This condition appears to be correctable now that additional specimens have been located. Persian leopards have a larger founder size than the former race, but some of their ancestors were older animals at the time of acquisition. Because of this, their potential fecundity was probably depressed from psychological problems related to adjustment and a shorter life span in captivity. Two founding females experienced pelvic deformities while young, and few of their cubs survived because they all had to be delivered via caesarian section. This procedure also shortened the reproductive life of the females involved because the owning zoos refrained from breeding the animals in the leopards' later years. Captive leopards appear to live longer than their wild counterparts, although precise data on wild populations is not available. In captivity many reach 12–15 years old, and exceptional individuals of several races have lived 20 years. Most captive-born leopards begin breeding when they are 3 years old and continue until they are 8–10 years old. Reproduction in females usually ceases at 12–14 years, although males have a longer reproductive life, with several successfully breeding when 19–20 years old.     

Effects of aluminum mulch on fecundity of apterous Myzus persicae on head lettuce in a field planting

Head lettuce field plantings were artificially infested with apterous adults of the green peach aphid, Myzus persicae (Sulzer). Significantly greater aphid fecundity was demonstrated on plants grown through aluminum-coated construction paper than on plants grown on bare soil. Higher temperatures and host-plant physiology were factors modified by the mulch, and could have resulted in larger aphid populations on plants grown over a reflective surface as the season progressed. Faster plant growth and a significantly larger yield per head of lettuce also resulted from the use of the aluminum mulch. The incidence of a leafhopper-borne plant disease, aster yellows, was significantly reduced on head lettuce in the aluminum mulch plots.

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Résumé Des cultures de laitue ont été artificiellement contaminées avec des adultes aptères de Myzus persicae. La fécondité a été significativement augmentée sur les plantes poussant sur un sol recouvert par un voile d'aluminium, comparées à celles poussant sur un sol nu. Cette augmentation pourrait entrainer des populations de pucerons de plus en plus importantes, au fur et à mesure de l'avancement de la saison, sur les plantes poussant au dessus d'une surface fortement réfléchissante. L'utilisation du voile d'aluminium a provoqué simultanément une accélération de la croissance et une augmentation des rendements de laitue. Ces résultats semblent dus à une augmentation de la température diurne, à une meilleure conservation de l'humidité et à une plus forte réflexion de la lumière lorsqu'il y a présence de voile d'aluminium. Par aulleurs, les dégâts provoqués sur feuilles par les germes pathogénes transmis par les Cicadelles delles sont significativement plus rares sur sol couvert de voile d'aluminium.

     

Comparative Studies on Root Invasion,Root Galling,and Fecundity of Three Meloidogyne spp. on a Susceptible Tobacco Cultivar

Root invasion, root galling, and fecundity of Meloidogyne javanica, M. arenaria, and M. incognita on tobacco was compared in greenhouse and controlled environment experiments. Significantly more M. javanica than M. arenaria or M. incognita larvae were found in tobacco roots at 2, 4, and 6 d after inoculation. Eight days after inoculation there were significantly more M. arenaria and M. javanica than M. incognita larvae. Ten days after inoculation no significant differences were found among the three Meloidogyne species inside the roots. Galls induced by a single larva or several larvae of M. javanica were significantly larger than galls induced by M. incognita: M. arenaria galls were intermediate in size. Only slight differences in numbers of egg masses or numbers of eggs produced by the three Meloidogyne species were observed up to 35 d after inoculation.     

Foraging behavior and life history of the stemborer parasitoidCotesia flavipes (hymenoptera: Braconidae)

The gregarious parasitoidCotesia flavipes (Hymenoptera: Braconidae) attacks larvae of pyralid and noctuid stemborers by entering the stemborer tunnel. The short-range foraging behavior of femaleC. flavipes was studied on stemborerinfested plants, in patches with host-related products and in artificial transparent tunnels. In addition, the longevity under specific conditions and the potential and realized fecundity of femaleC. flavipes were determined. Larval frass, caterpillar regurgitate, and holes in the stem are used in host location byC. flavipes. The response to host products byC. flavipes seems not to be host species specific. FemaleC. flavipes respond to frass from four stemborer species and one leaf feeder. No differences are found in the behavior ofC. flavipes on maize plants infested with the suitable host,Chilo partellus (Lepidoptera: Pyralidae), or the unsuitable host,Busseola fusca (Lepidoptera: Noctuidae). Attacking a stemborer larva inside the stem is risky for the parasitoid. The mortality rate of the parasitoids inside the stem is high: 30–40% of the parasitoids are killed by the spitting and biting stemborer larva.C. flavipes is relatively shortlived: without food the parasitoids die within 2 days; with food and under high-humidity conditions they die within 5–6 days.C. flavipes is proovigenic and has about 150 eggs available for oviposition. A relatively large proportion of the available egg load (20–25%) is allocated to each host, so femaleC. flavipes are egg depleted after parasitizing only five or six hosts.     

RAPD and morphological analysis of the rare plant species Vicia pisiformis (Fabaceae)

The amount and pattern of genetic variation was surveyed in two Swedish and three Czech populations of the rare perennial forest plant Vicia pisiformis. This species has a mainly easterly-continental European distribution and has few and small populations in Sweden. It is classified as 'vulnerable' on the Swedish Red Data list. Seeds from natural populations were collected and grown under controlled conditions in growth chambers. The variation was estimated in growth and fecundity traits and with Random Amplified Polymorphic DNA, RAPD. Low inter- and intra-population variation in RAPD-markers was found using 11 primers, with a similarity index (Wetton) for the families of 0.98. In contrast, multivariate analysis of variance showed significant morphological differences within and between populations. Also in the univariate ANOVAs, a number of the traits showed significant between-and/or within population differentiation. Cluster analysis for the morphological traits and RAPDs (UPGMA) did not structure the variation of families in accordance with their geographical distance. A Mantel test based on comparisons between Mahalonobfs and Jaccard distance for morphological and RAPD data, respectively, did not reveal any significant correlation between the two matrices. It is concluded that if a genetic conservation program is to be applied on Vicia pisiformis , different sampling strategies are needed to capture morphological vs RAPD variation. This is, to our knowledge, the first investigation that compares RAPD and morphological variation in a threatened plant species.     

Reproductive cycling and fecundity estimation in the upland bully

The upland bully is a prolific and widespread member of New Zealand freshwater fish communities that may mature at age 1 (or earlier). It begins spawning in spring, laying as many as eight clutches of eggs over the spring and summer, at periods as brief as 13 days. Ovaries contain two modes of maturing oocytes, so that oogenesis must be continual during the spawning season. This poses difficulties in fecundity estimation, which were solved by captive rearing. The ovoid eggs are about 2 mm long; egg size declines with clutch number during the summer, but increases with fish size. Clutch size varied, in 70 spawnings, from 121 to 880 eggs, with total seasonal fecundity up to >5000 eggs. The production of multiple clutches greatly increases seasonal fecundity and may explain the success of this species in sometimes unreliable or harsh environments.     

Fecundity and egg density in the redd for sea trout

The relationship between fecundity and length for sea trout Salmo trutta from three streams in NW England was curvilinear and, after logarithmic transformation of both variables, was well described by a linear regression model. Regression equations for the fish from the three streams were not significantly different ( p >0.05). The relationship between estimated eggs per redd and female size in a tributary of one of the streams was also well described by a linear regression model after logarithmic transformation. Fecundity was usually higher than estimated eggs per redd, and this difference increased with female size so that the mean number of eggs per redd expressed as a percentage of mean fecundity decreased from 100% for a female with a length of 240 mm to 79% for one of 650 mm. The power function in its logarithmic form has now been fitted to fecundity-length data for sea trout from 12 streams and rivers in England, Scotland, Ireland and Norway. Comparisons between fecundity estimates for the same sizes of females revealed a large variation between populations and possible reasons for this are discussed.     

Immunization of Atlantic salmon against the salmon louse: identification of antigens and effects on louse fecundity

Injection of extracts derived from adult caligid copepods induced a partial immunity to Lepeophtheirus salmonis in Atlantic salmon. Antigens were derived from the supernatant of adult lice extracts and were partially purified by Con A affinity chromatography. The antigens were also present in the pellet derived from adult lice extracts, Immunohistochemistry showed that antibodies present in the serum of rats immunized with the Con A purified extract bound predominantly to the gut of L. salmonis. Components of apparent sizes > 205 000, 165 000, 133 000, 130 000, 125 000, 114 000, 110 000, 96 000, 82 000, 78 000, 65 000, 46 000, 35 000, 31 000 and < 29 000 were present in the extract. Although the numbers of attached lice were initially higher on those fish in the immunized group, throughout the course of the challenge experiment the total numbers of lice did not vary greatly between the immunized or control groups of fish. Initially, an overall average of about 17 attached stages were recorded from each fish sampled and by the end of the experiment this figure had fallen to about five adult lice per fish. However, compared with control fish fewer gravid female lice were present on immunized fish and furthermore these lice possessed fewer eggs (P<0.01). No major differences in egg hatching success were recorded. Further exploitation of this would require the isolation and purification of the antigens responsible for the observed effects. The possibilities for the development of a salmon louse vaccine are promising.     

Complex competitive interactions in four species of Lucilia blowflies

Abstract.

• 1 The effects of intraspecific and interspecific larval competition on larval survival, adult size, adult longevity and fecundity were quantified in four species of coexisting Lucilia blowflies: illustris, silvarum, sericata and caesar.
• 2 There was a general negative effect of increasing density on larval and adult survival, size and fecundity. Additionally, complex species-specific and frequency-dependent responses were identified, which were not expected in these biologically and morphologically closely similar species.
• 3 Lucilia illustris, the numerically dominant species in the natural community, was a superior competitor to L.silvarum at intermediate densities but an inferior competitor at high density. Such nonlinear responses may be related to differences in the life histories and larval behaviour of the species (bigger eggs and more contest-type outcome of competition in L.silvarum).
• 4 We parameterized a model of interspecific competition on a subdivided resource in an attempt to reconcile the conflicting results on larval competitive abilities and the abundances of the species in the field. Using laboratory and field-estimated parameter values the model predicted coexistence of L.illustris and L.silvarum and the observed numerical dominance of the former species. The average densities of flies in the field are limited to relatively low levels, apparently preventing L.silvarum (the superior competitor at high density) from dominating and excluding L. illustris.