Effects of plant chemical extracts and physical characteristics of Apium graveolens and Chenopodium murale on host choice by Spodoptera exigua larvae

Choice tests with whole plants and leaf discs indicated that fourth instar Spodoptera exigua (Hübner) (Noctuidae: Amphypyrini) were found more frequently and ate significantly more of the weed Chenopodium murale than the associated crop plant Apium graveolens. In order to explain the preference, plant extracts, plant volatiles, soluble protein concentrations, water contents, and leaf toughness of the two plants were investigated. Bioassays of aqueous methanol (90%) and hexane extracts of leaves on cellulose discs indicated that neither attractants in C. murale nor repellents in A. graveolens could account for the observed preference. No significant difference could be found between the effects of plant volatiles from C. murale, A. graveolens and a control on larval dispersal by S. exigua. Selective feeding for higher levels of proteins also was not a factor, because A. graveolens had nearly twice the soluble protein of C. murale. Water content was approximately 6% higher (by weight) in C. murale than A. graveolens but most polyphagous larvae do not typically show compensatory feeding for water alone. However, the potentially related characteristic of leaf toughness was significantly different, with A. graveolens exhibiting 1.53 times the toughness of C. murale. Studies comparing five types of larval behavior on both plant species showed that the time spent in swallowing behavior was significantly greater on the tougher A. graveolens leaves relative to C. murale. To test the hypothesis that leaf toughness was affecting larval host choice, both plants were finely ground and incorporated into agar blocks. No differences in feeding behavior were detected. The implications of leaf toughness for larval diet and host choice are discussed.     

MORPHOLOGICAL DESCRIPTION OF THE LARVAE OF CERATOPHYLLUS FARRENICHAOI AND THEIR COMPARISON WITH THE LARVAE OF CERATOPHYLLUS CALLINAE TRIBULIS

Abstract This paper deals with the morphology of the larvae of Cerutophyllus farreni chaoi Smit and Allen, 1955 and a comparison is made with the larvae of C. gallinue tribulis Jordan, 1926.
The diagnostic characters of the larvae of the two subspecies are the shape of egg burster, number of mandibular teeth, the relative positions of the sense organs and setae on the tergites of the thorax and abdomen and number of the setae of anal comb and the strut setae.     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.

     

Heterogeneity of twoBeauveria bassiana strains revealed by biochemical tests,protein profiles and bio-assays ofLeptinotarsa decemlineata (Col.: Chrysomelidae) andColeomegilla macultata lengi (Col.: Coccinellidae) larvae

Biochemical profiles on API Rapid CH^* strips and protein profiles on polyacrylamide gels in the presence of sodium dodecyl sulfate were used to distinguish two strains of the entomopathogenic fungusBeauveria bassiana (Balsamo) Vuillemin, ARSEF 2991 and ATCC 44860. Next, the toxicity of these two strains was determined at concentrations of 10², 10⁴, 10⁶ and 10⁸ blastospores/ml on larvae of the Colorado potato beetleLeptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) and of its predator, the spotted ladybird beetle,Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Both strains were highly toxic toL. decemlineata larvae. However, the two strains exhibited different levels of toxicity forC. maculata larvae: ARSEF 2991 was toxic, whereas ATCC 44860 caused little coccinellid larval mortality.

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Résumé Les profils biochimiques sur galeries API Rapid CH^* et les profils protéiques sur gels de polyacrylamide ont été utilisés pour distinguer deux souches du champignon entomopathogèneBeauveria bassiana (Balsamo) Vuillemin. La toxicité de ces deux souches a été déterminée à des concentrations de 10², 10⁴, 10⁶ et 10⁸ blastospores/ml sur des larves du doryphore,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) et de la coccinelle maculéeColeomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Les deux souches deB. bassiana se sont avérées actives à l'égard des larves deL. decemlineata. Toutefois la souche ARSEF 2991 s'est avérée pathogène pour les larves deC. maculata, alors que la souche ATCC 44860 a provoqué une faible mortalité des larves.

     

Ciliated epithelium in the gut of larval Atlantic halibut, Hippoglossus hippoglossus

The presence of cilia was documented in the hindgut of larval Atlantic halibut ( Hippoglossus hippoglossus ) with the use of electron microscopy. Cilia were shown to be present as late as 8 and 9 day post hatch. These observations were compared to similar observations in more primitive teleosts.     

Spawning and distribution of bluefish Pomatomus saltatrix (L.) in the northwestern Mediterranean

The present study was carried out on the Catalan coast, the northern limit of the geographic distribution of Pomatomus saltatrix (Linnaeus, 1766) in the Mediterranean. Within the area studied, both larvae and adults were more abundant in the southern part, where surface temperature was slightly higher than in the north. Spawning of P. saltatrix was limited to the warmest months, from July to September, when the surface temperature was about 25° C, The most common larval sizes, between 2.25 and 2.75 mm s.l. , were distributed over the continental shelf, and the greatest concentrations were found between 20 and 100 m, suggesting an inshore spawning. Larvae, including the smallest sizes, were found in the most superficial layers and no evidence of vertical migration was observed. The species was regularly fished in the southern zone, maximum monthly catches ranging between 10–20 tonnes. The presence of adults in the coastal zone showed a marked seasonality closely related to temperatur, the lowest catches corresponding to the coldest months.     

RESPONSES AND CORRELATED RESPONSES TO ARTIFICIAL SELECTION ON THORAX LENGTH IN DROSOPHILA MELANOGASTER

Two sets of four replicate lines of Drosophila melanogaster were selected for large and small thorax with controls. F, progeny of crosses between the selected lines within each size category showed (a) a reduction in preadult viability in large lines relative to control and small lines when they were cultured at medium or high density in competition with a standard mutant marked competitor stock, and (b) an increase in larval development time in large lines relative to control and small lines. Natural selection for increased body size in adults may therefore be opposed by adverse effects on larval viability. The results are discussed in terms of the developmental mechanisms probably responsible for the change in body size. The preadult survival of the large and control lines was measured at three different temperatures, and there was no evidence for a significant interaction between size and temperature. The observed evolutionary increase in body size in response to reduced temperature in Drosophila must therefore involve either different genes from those subject to selection for size at a single temperature, or a fitness component other than preadult survival. There was no significant asymmetry in response to selection, and thorax length showed heterosis in crosses between the selected lines.     

Climatic adaptations in the Drosophila immigrans species group: seasonal migration and thermal tolerance

Abstract. 1. In central Japan, Drosophila curviceps Okada and Kurokawa was collected in spring and autumn but not in summer at lowlands (alt. 500–1200 m), while it was collected only in summer at highlands (1500–2000 m). Experiments on its thermal tolerance suggested that summer heat at the lowlands and winter low temperatures at the highlands were adverse to this species. It is considered that this species escapes from these extreme temperatures by undergoing seasonal migration between the lowlands and the highlands. This species had no photo-periodic diapause and bred at both lowlands and highlands.
2. D.immigrans Sturtevant was less cold-hardy but more heat-tolerant than D.curviceps. It is considered that this species is unable to overwinter outdoors at least in the study areas (i.e. alt. 500m or higher in central Japan) and its populations in these areas originate with migrants from warmer areas.
3. D.albomicans Duda, a subtropical species, was less cold-hardy but more heat-tolerant than the above two species.
4. Climatic adaptations and distributions of these species are discussed with reference to their thermal tolerance.     

Hatching plasticity in a Southeast Asian tree frog mitigates submergence-induced mortality

Environmentally cued hatching has been well-documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub-Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence-induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade-off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding-induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg-stage threats may be an indicator of species' ability to flexibly navigate a changing environment.