All-female broods and mimetic polymorphism in Acraea encedon (L.) (Lepidoptera: Acraeidae) in Tanzania

In some populations of the African butterfly, Acraea encedon, there are two kinds of females, one producing offspring in a normal 1:1 sex ratio, the other producing females only; in other populations the sex ratio is apparently normal. All-female broods had hitherto been mainly associated with populations in which field sampling revealed an excess of females. The all-female brood trait is described from a population at Dar es Salaam which field sampling suggested was normal, and this indicates that the trait may be much more widespread and common than had previously been supposed. This discovery also extends the known distribution of the trait across Africa from Sierra Leone to eastern Tanzania. The butterfly is also a polymorphic Müllerian mimic of Danaus chrysippus, which is a highly unusual phenomenon as Müllerian mimicry is almost invariably monomorphic. The relative frequencies of two corresponding colour forms of the two species of butterflies at Dar es Salaam adds support to the hypothesis that they are indeed Mullerian mimics. The results of breeding experiments suggest that the polymorphic forms in Acraea encedon are allelic with dominance.     

Wolbachia infection associated with all-female broods in Hypolimnas bolina (Lepidoptera: Nymphalidae): evidence for horizontal transmission of a butterfly male killer

Inherited bacteria that kill male hosts during embryogenesis infect a wide range of insect species. In order to ascertain if there are patterns to host infection, with particular male killing bacteria specialising on particular taxa, we investigated the male killing trait in the butterfly Hypolimnas bolina. All-female broods were first reported in this species in the 1920s. Investigation of this system in the Fiji Islands revealed the causal agent of sex ratio distortion in H. bolina to be a male killing Wolbachia bacterium. This bacterium is identical in wsp and ftsZ sequence to a male killer in the butterfly Acraea encedon in Tanzania, suggesting it has moved between host species, yet retained its phenotype. The prevalence of the Wolbachia was calculated for three different island groups of Fiji, and found to vary significantly across the country. Antibiotics failed to cure either the male killing trait or the Wolbachia infection. The implications of these results are discussed.     

Ocean migration and recaptures of tagged, triploid, mixed-sex and all-female Atlantic salmon (Salmo salar L.) released from rivers in Ireland

Fiftyfour thousand diploid and triploid Atlantic salmon were tagged with coded-wire micro-tags and released to the sea as smolts from two freshwater sites in Ireland in 1996 and 1997. Over 36,000 were mixed-sex groups in which the triploids (MS3N) were treated batches and the diploids (MS2N) were untreated batches of a single group of fertilized eggs at each site and year class. Over 17,000 were all-females, the triploids (AF3N) being treated batches and the diploids (AF2N) untreated batches of a single group of fertilized eggs at each site and year class. Adult tagged fish were subsequently recovered in the coastal fishery and in freshwater traps and angling fisheries in the rivers of release during 1997, 1998 and 1999. Recoveries from migration ranged from 0.08 to 9.79%. Diploid recoveries were within the normal ranges for salmon ranched from these sites, being between 0.64 and 1.82% at one site and between 3.85 and 9.79% at the other. Triploid recoveries, which occurred in the coastal fishery and in freshwater, ranged from 0.08 to 0.40% at the first site and from 0.98 to 2.05% at the other. Overall, triploid recoveries were between 12 and 24% of their diploid siblings within each release group. There were two peaks of recapture in the coastal fishery, the first in mid-June and the second in mid to late July. All-female diploids appeared to enter the fishery in advance of mixed-sex diploids. Triploids were the latest to arrive. There was no evidence of increased straying in triploids relative to diploids and the mean lengths, weights and condition factors were not significantly different between the ploidy groups. Triploidisation therefore reduced the home water harvest of treated salmon to less than 25% but did not completely eliminate triploid recaptures. The way in which triploidisation may influence the return of salmon from the oceanic feeding grounds is discussed.     

Population changes after two years of salmon (Salmo salar L.) stocking in upland trout (Salmo tmtta L.) streams

The survival of salmon stocked in upland trout streams in the presence of salmon parr was found to be only about half the value recorded when trout alone made up the resident stock. Changes in the trout population were also recorded following the two years of salmon stocking, and these suggested that the presence of salmon parr may also influence trout fry survival. The findings are discussed in the context of habitat competition and total stream holding capacity.     

Consistent differences among individual monarch butterflies (Danaus plexippus L.) in flight activity at low temperatures

Previous work suggested differences in allozyme frequencies between samples of monarch butterflies collected at different times of the day. This study examines the prediction that some individuals are active consistently earlier in the day than others. Four specific hypotheses were tested: (1) Individuals caught early on one day were more likely than those caught late to be caught early on subsequent days. This was true in some experiments. (2) Individuals caught early in the field were more likely than those caught late to fly early in outdoor flight cages. This was true when outdoor temperatures were low (between 10 and 20^oC) but not when they were above 20^oC. (3) Individuals caught early in the field were more likely to be able to fly at low body temperatures than those caught late. This was not true. (4) Individuals that flew early in outdoor flight cages were more likely to be able to fly at low body temperatures. This was not true. Overall we conclude, on the basis of field and flight cage experiments, that some individuals are active consistently earlier in the day than others. The lack of a relationship between field and temperature cabinet results indicates that this is not purely a result of differences in ability to fly at low body temperatures. The implications of these results are discussed.     

The effect of ejaculate mass on female reproductive output in the european swallowtail butterfly,Papilio machaon (L.) (Lepidoptera: Papilionidae)

Previously, we showed that virgin males of Papilio machaondeliver ejaculates that are twice as big as any ejaculates they transfer at later matings. Here, we investigate the consequences of these two size classes of ejaculates on female reproductive output and demonstrate that females that received one small ejaculate laid as many eggs, fertilized the same proportion of eggs, and lived as long as those that had received one big ejaculate. However, females that received big ejaculates laid heavier eggs, but only between the twelfth and the fifteenth days of egg-laying. We conclude that male-derived nutrients appear to have a limited effect on female reproductive output in P. machaonand that the large size of ejaculates delivered by male butterflies are determined primarily by selection on males to produce longer refractory periods in females.     

Genetic changes in a vendace Covegonus albula (L.) population, 92 years after introduction

The Osensjmn vendace, Coregonus albula (L.), population was founded in 1895 by introduction of about 90 000 fry from Lake Mjøsa. After 92 years, or about 46 generations of isolation, remarkable genetic changes were evident among the transplants compared to their source population. Electrophoresis of 33 enzyme loci revealed that allele frequencies differed significantly in eight of the 10 polymorphic loci. Nei's unbiased genetic distance was D = 0.012, representing the level of population differentiation usually observed among distant watercourses in vendace. Genetic variability was clearly higher among the transplants: average observed heterozygosity was 14.8% compared with 11.2% among Lake Mjøsa vendace. The high genetic variation among Osensjoen vendace shows that the divergence is not due to a small number of founders or bottlenecks in later generations. Selection by the contrasting environmental conditions between the habitats of the donor and transplanted populations is the most plausible hypothesis to explain the genetic changes in the Osensjsen vendace.     

Phosphorus availability to rice (Oriza sativa L.)-wheat (Triticum estivum L.) in a Vertisol after eight years of inorganic and organic fertilizer additions

Integrated use of inorganic fertilizer N and well decomposed cattle manure (CM) or 30-35 days old Parthenium (Parthenium hysterophorus L.), a weed grown off site as green manure (GM) under repeated applications of fertilizer P and urea N for eight years in a rice (Oriza sativa L.)-wheat (Triticum estivum L.) sequence was studied on transformation of fertilizer P applied to soil at the National Research Center for Weed Science, Jabalpur, India. Based on the results, it appeared that, repeated applications of 52 kg super-phosphate P resulted in a marked increase in Olsen P linearly with time. Conjunctive use of urea fertilizer N with organic manure resulted in a larger increase in Olsen P in the Vertisol. Studies further revealed that the greater accumulation of fertilizer P applied in excess to crop removal occurred in inorganic P in the plots receiving only fertilizer N. However, plots receiving fertilizer N along with organic manures led to P accumulation predominantly in organic forms. The study suggests that these two pools of P acted as a sink when fertilizer P was applied in excess to crop removal and are bio-chemically active. The Olsen P status after 8 cycles of rice-wheat crops revealed that the average amount of fertilizer P required after adjusting for crop uptake to increase Olsen P by 1 mg kg(-1) soil was 7.2 kg Pha(-1) in the plots receiving only fertilizer N. Whereas, application of 5t FYM or 6t GM reduced it to 4.6 kg Pha(-1). The plots receiving manure always maintained a greater concentration of Olsen P. The application of CM or GM with fertilizer N enriched short-term inorganic P as well as long-term organic P fertility. After eight years, larger concentrations of organic P in the subsurface layer (16-30 cm), compared to initial values, indicates downward movement of P in organic forms.     

History and dynamics of the crown-of-thorns starfish Acanthaster planci (L.) in the Suva area,Fiji

Annual recruitment of Acanthaster planci over a 13 year period in a known juvenile refuge substratum on Suva Reef was very patchy in time and space. Macroscale recruitment events resulted in outbreaks over many thousands of hectares over 100 km of coastline whereas localised but intensive mesoscale events resulted in concenrated aggregations over areas of several tens of hectares. A very low level of recruitment occurred in most years but three intensive, macroscale recruitment events occurred in 1977, 1984 and 1987, and two localised but intensive recruitment events occurred in 1982 and 1983. Annual recruitment of A. planci between 1975–89 had no overt relationship with rainfall events, as proposed in the terrestrial run-off hypothesis on the cause of primary out-breaks. Growth rates within monitored cohorts were highly variable, but mean growth rates of two cohorts 1984 and 1987 were relatively similar. Mortality rates of three monitored cohorts were variable. Longevity of the 1977 cohort was 7–8 years, while that of the 1984 cohort was 2–3 years. Mortality of the 1987 cohort has been low to date (i.e. 4 years of age). Disease, attributed to an undescribed sporozoan pathogen, was responsible for two mass mortalities in the 1984 cohort, in 1984 and in 1986, and eventually resulted in the extinction of this cohort. Anecdotal reports indicate that outbreaks of A. planci are increasing in frequency and severity. According to Fijian reef fishermen, the starfish were low to moderate in abundance in the Suva area from the 1920s to the 1960s. A progressive build up occurred on some reefs in 1963–67 leading to a major outbreak episode from 1967–1971. The outbreaks were in a chronic phase between 1977–1989. Our findings demonstrate that there is no invariable pattern or process involved in the population dynamics of A. planci and that a single explanation of the A. planci phenomenon is therefore unlikely.     

Radial distributions of Cd in stems of oak trees (Quercus robur L.) re-analyzed after 10 years

Radial distribution patterns of Cd were determined in stems of the same oak trees (Quercus robur L.) in 1983 and again in 1994. On both sampling dates the same distribution patterns were generally observed. Highest concentrations of Cd were found at the sapwood-heart-wood transition. A sharp drop over this boundary towards inner parts of the stems occurred in all trees. In the decade between the two investigations the sapwood-heartwood boundaries had shifted outwards by 9–11 annual rings. The Cd peaks at the boundaries were shifted by approximately the same interval. The results suggest that the described Cd peaks are mobile in a radial direction. The present location of such peaks cannot be used to infer the pollution history of the tree's environment. The Cd accumulation at the sapwood-heartwood boundary is probably affected by physiological processes in the wood. Thus it is concluded that radial distributions of Cd in stems of oak trees are no reliable source of information for retrospective monitoring of past time pollution levels.     

Gene frequency in an artificial colony of the Scarlet Tiger Moth Panaxia dominula (L.) after 28 years

An artificial colony of Panaxia dominula was started in Wirral in 1961 by P. M. Sheppard to study the selection acting on the medionigra gene. Previous evidence from Oxford indicated a lowered fitness which, balanced by a mating advantage, led to an equilibrium at about three per cent. The Wirral colony was rediscovered in 1989 and now has a medionigra gene frequency of 27 per cent compared with an initial one of 25 per cent, i.e. the Hardy-Weinberg equilibrium has been virtually unchanged. The selective balance in the colony is therefore very different from that elsewhere, and the suggestion is made that the original gene frequencies have remained unchanged because there has been no human interference, unlike Oxford where mark-release-recapture has been the standard procedure, but there are some caveats to this view.     

A comparison of apomictic reproduction in eastern gamagrass (Tripsacum dactyloides (L.) L.) and maize-Tripsacum hybrids

The expression of gene(s) governing apomictic reproduction inTripsacum provides the best foundation for comparing the effectiveness of apomictic reproduction in a series of maize-Tripsacum hybrids. Several 38-chromosome, apomictic maize-Tripsacum hybrids are available which possess the gene(s) conferring apomictic reproduction fromTripsacum. Without a base line for comparison, studies directed towards discerning the successful transfer or effectiveness of gene expression in a maize background are hampered. The objectives of this study are to compare the reproductive features found in apomicticTripsacum with those in apomictic maize-Tripsacum hybrids. In addition, this study determined the feasibility of utilizing these maize-Tripsacum hybrid materials to continue an attempt to transfer the genes into a pure maize background. The frequency and occurrence of five unique reproductive features found in apomictic accessions ofTripsacum dactyloides were compared to the reproductive behaviours exhibited in the maize-Tripsacum hybrids. Results indicate the genes controlling apomixis in tetraploidTripsacum are fully functional in maize-Tripsacum hybrids with diploid and triploid maize constitutions. The ability of theTripsacum apomictic genes to retain full expression provides evidence to continue their transfer to a diploid or tetraploid maize background.The use of company names in this publication does not imply endorsement by the USDA-ARS, or the product names or criticism of similar ones not mentioned. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.     

Breeding of four-leaf white clover (Trifolium repens L.) through 60Co gamma-ray irradiation

Four-leaf white clover is not found easily in nature due to its low appearance rate (1 in 10,000). Because people believe that it brings good luck and like to either keep it or present it to a loved one, it has commercial and ornamental value. To breed four-leaf clover, we exposed its flowers to γ-rays at the pollination stage. The M₁ seeds produced following doses at 25–100 Gy showed an approximately 74% germination rate, with seedling survival at 46%. In the M₁ generation of plants irradiated within that dose range, we found an increased frequency of four leaflets. One of them, Jeju Lucky-1 (JL-1), had a frequency of about 60%. To see whether that mutation was somaclonal or genetic, we observed its M₂ generation and found that such a phenotype reappeared. Although our results demonstrated that the irradiation of fully mature flowers led to a higher frequency of 4-leaflets, we could not clearly explain the genetic mechanism involved. We suggest that JL-1 is valuable as a new variety, without further genetic fixation, because white clover can be propagated vegetatively by stolons. I.-J. Song and H.-G. Kang contributed equally to this work.     

A novel hepcidin-like in turbot (Scophthalmus maximus L.) highly expressed after pathogen challenge but not after iron overload

Hepcidins are antimicrobial peptides with an important role in the host innate immunity. Moreover, it has been reported that mammalian hepcidins present a dual-function being a key regulator in the iron homeostasis. Here, we describe the coding sequence of a novel hepcidin-like peptide in turbot, Scophthalmus maximus. This molecule presents several differences with regard to the previously characterized hepcidin in this flatfish species and it has not the hypothetical iron regulatory sequence Q-S/I-H-L/I-S/A-L in the N-terminal region. Therefore we propose the existence of at least two types of hepcidin in turbot. Moreover, results revealed a higher variability in the mRNA sequences of the novel hepcidin compared with the other form. Constitutive expression of turbot hepcidins (Hepcidin-1 and Hepcidin-2) was analyzed in several tissues and as expected, both molecules were highly represented in liver. On the other hand, the effect of three different stimuli (bacterial or viral infection and iron overloading) in the level of hepcidin mRNA was also examined and a differential response to pathogens and iron was observed. Whereas both hepcidins were affected by pathogen challenge, only Hepcidin-1 was up-regulated after iron overloading. Therefore, this and other evidences suggest that these peptides could be involved in different functions covering the dual role of mammalian hepcidins.     

Tissue distribution and residue depletion of thiamphenicol after multiple oral dosing in seabass (Dicentrarchus labrax L.) and seabream (Sparus aurata L.)

The distribution and residue depletion of thiamphenicol (TAP) were studied in seabass ( Dicentrarchus labrax L.) and seabream ( Sparus aurata L.) reared in field conditions at temperatures of 20–28 °C. The drug was administered orally as medicated feed at the rate of 40 mg active ingredient (a.i.) kg⁻¹ of biomass once a day for 5 days. Samples of muscle, liver, skin and vertebrae from 10 fishes were collected on the 2nd and 4th day of treatment and 1, 2, 3, 5, 7, 9, 12, 15, 18, 21, 24, 27 and 30 days after the last administration of the drug, and were stored at −20 °C. Quantitative analysis of TAP was performed by high performance liquid chromatography (HPLC) after liquid-liquid extraction; the quantification limits of the HPLC method were 0.02 μg/g for muscle, and 0.05–0.10 μg/g for the other tissues. In seabass, TAP concentrations during treatment were higher in liver and muscle than in skin and vertebrae, and rapidly decreased after the end of medication. Three days after treatment ceased, TAP was still detectable in liver (0.41 ± 0.23 μg/g), vertebrae (0.09 ± 0.03 μg/g) and in three out of 10 samples of muscle (0.03 μg/g), but not in skin. All tissues were below the limits of quantification on the 5th day of withdrawal. In seabream the highest TAP concentrations during treatment were measured in liver and skin, and their reduction after the end of medication was as rapid as that of seabass: on the 3rd day after treatment ceased traces were found in only four out of 10 samples of muscle (0.03 ± 0.00 μg/g) and vertebrae (0.08 ± 0.02 μg/g).     

Evaluation of pesticides against major pests of jute (Corchorus olitorius L.) in West Bengal,India

Among the pesticides evaluated against the jute pests under field conditions, endosulfan 35 EC at 350 g a.i./ha was found to be the most effective insecticide for controlling semilooper, Bihar hairy caterpillar and myllocerus weevil. Endosulfan and fenpropathrin provided good control of yellow mite as well. Even, endosulfan-treated plots gave maximum fibre and stick yield with greater benefit–cost ratio (BCR) over others. Next to endosulfan and chlorpyriphos, neemazal (azadirachtin 50,000 ppm) are useful and safer options against semilooper, Bihar having caterpillar, myllocerus and yellow mite. Methoxyfenocide 10 EC at 200g a.i./ha provided good control (70.60%) of S. obliqua even after 14 days of spraying, but it was not effective against other pests of jute. Further, almost similar efficacy of neemazal and chlorpyriphos was found against the pest complex of jute and based on BCR, neemazal could be an alternative choice over chlorpyriphos.     

Micropropagation of the endangered aromatic varieties of Vigna radiata (L.) Wilczek in West Bengal, India

Summary Vigna radiata (L.) Wilczek, popularly known as mungdaal in India, is an important source of protein for supplementing the vegetarian diet in all the states of India. There are various varieties of mungbean. Depending upon the flavor and aroma, these are classified into two groups: (a) the good aromatic variety or Sonamung, and (b) the other, without any significant aroma, the Tilmung. In the present investigation, we attempted to propagate a good aromatic variety of mungbean (which is becoming nearly extinct) by in vitro shoot-tip multiplication. The best hormone combination in B5 medium was 0.2 mg of α-naphthalene acetic acid per 1 (1.074 μM) and 5 mg of N⁶-benzyladenine per 1 (22.192 μM). The plantlets were then rooted in hormone-free B5 medium and finally transferred to soil. This method of shoot-tip multiplication was found to be a reproducible and effective method for germplasm preservation of mungbean.     

Conservation of S-locus for self-incompatibility in Brassica napus (L.) and Brassica oleracea (L.)

 Self-incompatibility (SI) in Brassica is a sporophytic system, genetically determined by alleles at the S-locus, which prevents self-fertilization and encourages outbreeding. This system occurs naturally in diploid Brassica species but is introduced into amphidiploid Brassica species by interspecific breeding, so that in both cases there is a potential for yield increase due to heterosis and the combination of desirable characteristics from both parental lines. Using a polymerase chain reaction (PCR) based analysis specific for the alleles of the SLG (S-locus glycoprotein gene) located on the S-locus, we genetically mapped the S-locus of B. oleracea for SI using a F₂ population from a cross between a rapid-cycling B. oleracea line (CrGC-85) and a cabbage line (86-16-5). The linkage map contained both RFLP (restriction fragment length polymorphism) and RAPD (random amplified polymorphic DNA) markers. Similarly, the S-loci were mapped in B. napus using two different crosses (91-SN-5263×87-DHS-002; 90-DHW-1855-4×87-DHS-002) where the common male parent was self-compatible, while the S-alleles introgressed in the two different SI female parents had not been characterized. The linkage group with the S-locus in B. oleracea showed remarkable homology to the corresponding linkage group in B. napus except that in the latter there was an additional locus present, which might have been introgressed from B. rapa. The S-allele in the rapid-cycling Brassica was identified as the S₂₉ allele, the S-allele of the cabbage was the S ₅ allele. These same alleles were present in our two B. napus SI lines, but there was evidence that it might not be the active or major SI allele that caused self-incompatibility in these two B. napus crosses. Received: 7 June 1996/Accepted: 6 September 1996