Critical,pupal and adult weights in the size related metamorphosis of the black lyre leafroller ‘Cnephasia’ jactatana

Adult reproductive performance is linked to the period of feeding done by the final instar larva after attainment of a larval critical weight (L_CW). The highest weight attained by a final instar larva is referred to as the larval maximum weight (L_MW) and is the onset of the pre-pupal period. The relationships between L_CW, pupal weight (P_W) and adult weight (A_W) are described as functions of the L_MW. In the leafroller Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) L_CW was dependent on larval size and was approximately 75% of the mean L_MW. L_CW was about 29 mg and 36 mg for male and female larvae of 1.18 mm and 1.20 mm head-capsule width, respectively. Over three successive generations of laboratory rearing, P_W was approximately 30% and 25% lower than the L_MW for males and females, respectively. A_W was consistently about 50% and 40% lower than the P_W for males and females, respectively. The decrease in weight from L_MW to P_W was named as the constant D_P and found to be 0.3 for males and 0.25 for females. The total decrease from L_MW to A_W was the constant D_A and was 0.6 for males and 0.5 for females. The duration of the latent feeding period was positively correlated to P_W and A_W. L_CW may be used to derive quality indices that describe and predict pupal and adult performance.

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Résumé Les performances reproductives sont liées à la période d'alimentation du dernier stade larvaire après l'obtention d'un poids critique (L_CW). Le poids maximal atteint au dernier stade larvaire est défini comme le poids larvaire maximal (L_MW), il correspond au début de la période prénymphale. Les relations entre poids de la chrysalide (P_W) et poids de l'audulte A_W) sont présentées comme des fonctions de L_MW). Chez Cnephasia jactatana Walker (Lep. Tortricidae), L_CW dépend de la taille de la chenille et correspond à environ 75% de la valeur moyenne de L_MW. L_CW est respectivement de 29 mg et 36 mg pour les chenilles mâles et femelles dont les capsules céphaliques ont 1,18 et 1,20 mm. Pour 3 générations successives, P_W est environ 30% et 25% inférieur à L_MW des mâles et des femelles. La régression du poids de L_MW à P_W est désignée comme la constante D_P et vaut 0,3 pour les mâles et 0,25 pour les femelles. La régression de L_MW à A_W est désignée comme la régression D_M et vaut 0,6 pour les mâles et 0,5 pour les femelles. La durée de la période d'alimentation latente est liée positivement à P_W et A_W. L_CW peut être utilisé comme indice dérivé décrivant et prédisant les potentialités nymphales et imaginales.

     

Nutritional requirements for conidial germination and hyphal growth of Beauveria bassiana

Nutritional requirements for germination and growth of the entomopathogenic fungus Beauveria bassiana are not complex. For germination to occur, a utilizable source of carbon must be present; however, a nitrogen source is needed for continued hyphal growth, otherwise lysis ensues. Compounds that can serve as utilizable carbon-energy sources for germination include glucose, N-acetylglucosamine, glucosamine, chitin, starch, lanolin, hydrocarbons in crude oil, and some longer-chain fatty acids. Both organic and inorganic sources of nitrogen are readily utilized for growth. Conidia undergo active metabolism soon after being placed in a suitable growth medium, indicating that conidia are released from their state of dormancy several hours before emergence of the germ tube can be observed. Because of the nutritional versatility of B. bassiana, this fungus should be able to survive and be infective in several types of natural environments.     

The amino acid/K symporters for neutral amino acids along the midgut of lepidopteran larvae: Functional differentiations

The functional properties of the K⁺-dependent symporter for neutral amino acids have been investigated in brush border membrane vesicles prepared from the anterior, middle and posterior portions corresponding to the three morphologically distinguishable regions of the midgut of Bombyx mori larvae. An intravesicular accumulation of leucine was driven by a K⁺-gradient in the three preparations, but vesicles from the posterior tract displayed much higher uptake and accumulation values. Kinetic analysis of leucine uptake, performed in experimental conditions which mimic as closely as feasible experimentally those occurring in vivo (Δψ = −90 mV, pH_in7.2/pH_out8.7, [K⁺]_out100 mM), evidenced that the affinity for the amino acid was similar along the midgut (150 μM), but V_max in the posterior region was more than 11-fold higher than that of the anterior-middle tract (11.3 ± 0.7 and 0.98 ± 0.07 nmol/7s/mg protein, respectively). Leucine uptake was remarkably influenced by extravesicular pH and by Δψ only in vesicles from the posterior midgut: a lowering of pH to 7.2 caused a sevenfold increase of K_m, whereas in the absence of Δψ, V_max decreased threefold. The selectivity sequence for the alkali cations was somewhat different in the two midgut regions, but K⁺ remained the most effective. In the posterior midgut, the selectivity for K⁺ was greatly enhanced when a transmembrane electrical potential was present. Leucine kinetics as a function of external potassium concentration was hyperbolic in the posterior and sigmoidal in the anterior-middle part. Inhibition of leucine uptake induced by a 20-fold excess of different amino acids suggested the presence in both midgut tracts of a broad specificity system for neutral amino acids, with many-but not all-features in common with the B^o system of mammal intestinal and renal epithelial brush borders. However, there are differences between the two midgut regions as regard to the ability of the symporters to recognize the different amino acids, which concern the side chain and the presence of the aromatic ring. Altogether these data suggest that two kinds of symporters for neutral amino acids, with different functional properties, are expressed in the anterior-middle and posterior regions of the lepidopteran midgut.     

Effects of carbon-dioxide anaesthesia on the number of instars,larval duration and adult body size of the German cockroach, Blattella germanica

Effects of repeated carbon-dioxide anaesthesia during larval development on the number of moults, larval duration, and the body size of resulting adults were investigated. Concentration of carbon dioxide administered was 70%, and each period of anaesthesia lasted for 3 min. Anaesthesia administered twice a week until the 3rd instar increased the number of instars required to reach maturity. However, repeated anaesthesia after the 4th instar scarcely influenced the number of instars. On the other hand, repeated anesthesia prolonged larval duration whenever administered during the early or late instars. It is thus suggested that anaesthesia by carbon dioxide during larval development has two distinct effects: increasing the number of moults and prolonging larval duration. The former is stage specific and effective only during early instars, whereas the latter is effective during any particular instars until the last instar. The body size of resulting adults remained almost the same as for controls even after the repeated carbon-dioxide anaesthesia as many as 14 times. Some further observations concerning correlations between the number of moults, larval duration and adult body size are shown, and differences between the sexes regarding the number of instars and larval duration are also presented.     

Wandering behaviour and pupariation in tsetse larvae

Abstract .Following parturition, the third instar larva of Glossina morsitans morsitans West begins a wandering period in which it crawls to the site of pupariation. The duration of wandering can be drastically shortened by pinching or by denying the larva physical contact with the substrate. Contact with water increases the wandering period. Duration of subsequent activities appears to be rigidly fixed. At the end of the wandering period, the larva quickly progresses through a stereotypic sequence of behaviours that include immobilization and excretion of a liquid from the anus, retraction of the anterior segments, cuticular shrinkage, and tanning. Muscular activity and mechanical changes in the cuticle are reflected in changes of haemocoelic pressure. Muscular contractions produce pressure pulses that gradually increase in frequency and intensity, reaching a peak during retraction of the anterior segments. Changes in the mechanical properties of the cuticle cause a more gradual elevation of baseline pressure as the cuticle shrinks and loses its plasticity. As tanning begins, muscular activity ceases and haemocoelic pressure gradually decreases. In spite of its unusual early development within the confines of the female's uterus, the free-living larva shows the full behavioural repertoire observed in other cyclor-rhaphous Diptera at pupariation.     

Effects of Disinfectants on Larval Development of Ascaris suum Eggs

The objective of this study was to evaluate the effects of several different commercial disinfectants on the embryogenic development of Ascaris suum eggs. A 1-ml aliquot of each disinfectant was mixed with approximately 40,000 decorticated or intact A. suum eggs in sterile tubes. After each treatment time (at 0.5, 1, 5, 10, 30, and 60 min), disinfectants were washed away, and egg suspensions were incubated at 25˚C in distilled water for development of larvae inside. At 3 weeks of incubation after exposure, ethanol, methanol, and chlorohexidin treatments did not affect the larval development of A. suum eggs, regardless of their concentration and treatment time. Among disinfectants tested in this study, 3% cresol, 0.2% sodium hypochlorite and 0.02% sodium hypochlorite delayed but not inactivated the embryonation of decorticated eggs at 3 weeks of incubation, because at 6 weeks of incubation, undeveloped eggs completed embryonation regardless of exposure time, except for 10% povidone iodine. When the albumin layer of A. suum eggs remained intact, however, even the 10% povidone iodine solution took at least 5 min to reasonably inactivate most eggs, but never completely kill them with even 60 min of exposure. This study demonstrated that the treatment of A. suum eggs with many commercially available disinfectants does not affect the embryonation. Although some disinfectants may delay or stop the embryonation of A. suum eggs, they can hardly kill them completely.     

Differentiation of subspecies and sexes of Beringian Dunlins using morphometric measures

Five subspecies of Dunlins (Calidris alpina) that breed in Beringia are potentially sympatric during the non‐breeding season. Studying their ecology during this period requires techniques to distinguish individuals by subspecies. Our objectives were to determine (1) if five morphometric measures (body mass, culmen, head, tarsus, and wing chord) differed between sexes and among subspecies (C. a. actites, arcticola, kistchinski, pacifica, and sakhalina), and (2) if these differences were sufficient to allow for correct classification of individuals using equations derived from discriminant function analyses. We conducted analyses using morphometric data from 10 Dunlin populations breeding in northern Russia and Alaska, USA. Univariate tests revealed significant differences between sexes in most morphometric traits of all subspecies, and discriminant function equations predicted the sex of individuals with an accuracy of 83–100% for each subspecies. We provide equations to determine sex and subspecies of individuals in mixed subspecies groups, including the (1) Western Alaska group of arcticola and pacifica (known to stage together in western Alaska) and (2) East Asia group of arcticola, actites, kistchinski, and sakhalina (known to winter together in East Asia). Equations that predict the sex of individuals in mixed groups had classification accuracies between 75% and 87%, yielding reliable classification equations. We also provide equations that predict the subspecies of individuals with an accuracy of 22–96% for different mixed subspecies groups. When the sex of individuals can be predetermined, the accuracy of these equations is increased substantially. Investigators are cautioned to consider limitations due to age and feather wear when using these equations during the non‐breeding season. These equations will allow determination of sexual and subspecies segregation in non‐breeding areas, allowing implementation of taxonomic‐specific conservation actions.     

How river structure and biological traits influence gene flow: a population genetic study of two stream invertebrates with differing dispersal abilities

1. Determined by landscape structure as well as dispersal‐related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small‐scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal‐related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre‐alpine catchment and compared these results to the broader‐scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in‐stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in‐stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal‐related traits when planning management and conservation strategies.     

Genetic differentiation and signatures of local adaptation revealed by RADseq for a highly dispersive mud crab Scylla olivacea (Herbst, 1796) in the Sulu Sea

Connectivity of marine populations is shaped by complex interactions between biological and physical processes across the seascape. The influence of environmental features on the genetic structure of populations has key implications for the dynamics and persistence of populations, and an understanding of spatial scales and patterns of connectivity is crucial for management and conservation. This study employed a seascape genomics approach combining larval dispersal modeling and population genomic analysis using single nucleotide polymorphisms (SNPs) obtained from RADseq to examine environmental factors influencing patterns of genetic structure and connectivity for a highly dispersive mud crab Scylla olivacea (Herbst, 1796) in the Sulu Sea. Dispersal simulations reveal widespread but asymmetric larval dispersal influenced by persistent southward and westward surface circulation features in the Sulu Sea. Despite potential for widespread dispersal across the Sulu Sea, significant genetic differentiation was detected among eight populations based on 1,655 SNPs (F_ST = 0.0057, p < .001) and a subset of 1,643 putatively neutral SNP markers (F_ST = 0.0042, p < .001). Oceanography influences genetic structure, with redundancy analysis (RDA) indicating significant contribution of asymmetric ocean currents to neutral genetic variation (Radj2 = 0.133, p = .035). Genetic structure may also reflect demographic factors, with divergent populations characterized by low effective population sizes (N _e < 50). Pronounced latitudinal genetic structure was recovered for loci putatively under selection (F_ST = 0.2390, p < .001), significantly correlated with sea surface temperature variabilities during peak spawning months for S. olivacea (Radj2 = 0.692–0.763; p < .050), suggesting putative signatures of selection and local adaptation to thermal clines. While oceanography and dispersal ability likely shape patterns of gene flow and genetic structure of S. olivacea across the Sulu Sea, the impacts of genetic drift and natural selection influenced by sea surface temperature also appear as likely drivers of population genetic structure. This study contributes to the growing body of literature documenting population genetic structure and local adaptation for highly dispersive marine species, and provides information useful for spatial management of the fishery resource.