Search

The digestive tract of humus-feeding scarab beetle larvae shows considerable parallels to the situation in soil-feeding termites, particularly with respect to the alkaline gut regions. The gut pf Pachnoda ephippiata larvae harbors a dense and diverse microbiota, which differs considerably among the major gut regions and from that in the soil, fed to the larvae.

A report on the community structure of bacteria and archaea in the midgut, hindgut, and food soil of Pachnoda ephippiata larvae, determined with cultivation-independent techniques is presented. Analysis revealed that the intestines of Pachnoda ephippiata larvae contain a complex gut microbiota that differs markedly between midgut and hindgut and that is clearly distinct from the microbia in the food soil.

Optimal values for life history traits are expected to depend upon environmental conditions during development and the period within which development is constrained (e.g., biotic factors and time constraints, respectively). Theory predicts that life history responses to both biotic factors and time constraints may be both direct and behaviorally mediated. Few experimental studies of life histories have considered the joint effects of biotic factors and time constraints, and fewer still have been able to disentangle direct from behaviorally mediated effects. We studied such interactions by manipulating the perceived time to the onset of winter, predation risk, and food resources level in larvae of the damselfly Lestes sponsa. In the first experiment (predation X time constraint), the presence of a predator caused an overall reduction in foraging activity, development rate, and mass at emergence. However, larvae that had less time available before the end of the season, increased foraging activity and development rate, while mass at emergence decreased. These results suggest that the observed changes in life history characters were behaviorally mediated in the presence of predators. In contrast, life history responses of time-constrained larvae occurred independently of the behavioral changes and, therefore, were direct. In the second experiment (food level X time constraint) larvae under high food levels had a higher foraging activity, increased development rate, and higher growth rates, compared to low food-level treatments. Time-constrained larvae accelerated development and had a smaller mass at emergence at high food levels than larvae that were not time constrained. In contrast, and opposite to predictions, time-constrained larvae at low food levels had the slowest development rate and the largest mass at emergence. We suggest that larvae in the latter group were aiming to delay emergence to the next season (cohort splitting). Our results suggest that both behaviorally mediated and direct responses to biotic factors and time constraints are a feature of the life history of this damselfly. Key words: damselflies; development; food resource; growth rate; Lestes sponsa; life history; mass at metamorphosis; phenotypic plasticity; predation risk; time constraints; trade-offs.

In both Drosophila and Manduca sexta, the ecdysone-induced broad complex (BR-C) mRNA first appears in the final larval instar at the onset of metamorphosis and persists through the production of the pupal cuticle. We found that in neither species is it expressed during the adult molt. Application of the JH analog pyriproxifen to Manduca shortly after pupation resulted in formation of a second pupa and caused the appearance of BR-C mRNA at the time of pupal cuticle deposition. Similarly, Drosophila treated with pyriproxifen at pupariation formed pharate adults with normal heads and thoraces but the abdomens lacked bristles and hairs. In these animals, BR-C mRNA persisted in the abdomen, but not in the head and thorax, with the predominance of Z1 isoform. In JH-treated abdomens, the pupal cuticle gene Edg78E was reexpressed later, and the adult cuticle gene Acp65A was suppressed. Using heat-inducible transgenes, we demonstrated that ectopic expression of BR-C Z1 caused the reexpression of Edg78E and suppression of Acp65A in both anterior and posterior portions and resulted in a lack of bristles and hairs on both parts. Heat-shock induction of BR-C Z2 also induced Edg78E mRNA, but it could not suppress the expression of Acp65A. Trace amounts of Edg78E mRNA were found after heat-shock induction of Z4, and none was found after heat shock of Z3. This finding is the first indication that BR-C encodes a transcription factor that directs a developmental switch in differentiation of a polymorphic cell and that it may be pupal-specific. Thus, it mediates the 'status quo' effects of JH during the adult molt.

During the last larval molt in Manduca sexta, a number of transcription factors are sequentially expressed. Unlike E75A and MHR3, whose mRNAs are induced when the ecdysteroid titer increases, the expression of MHR4 mRNA occurs transiently at the onset of the decline of ecdysteroid titer followed by [Beta] FTZ-F1 mRNA expression when the ecdysteroid titer becomes low. When day 2 fourth epidermis was exposed to 20-hydroxyecdysone (20E) in vitro, MHR4 mRNA appeared between 12 and 21 h, peaked at 24 h, and then declined. Using the protein synthesis inhibitors cycloheximide and anisomycin both in vivo and in vitro, we found that the MHR4 transcript was directly induced by 20E and required the presence of 20E for its expression. The accumulation of MHR4 mRNA, however, did not occur until a 20E-induced inhibitory protein(s) disappeared. This control of MHR4 expression is unique among the ecdysone-induced transcription factors. When the epidermis was cultured with 20E, [Beta]FTZ-F1 mRNA was not induced until after the removal of 20E as previously found for Drosophila and the silkworm Bombyx mori. The presence of juvenile hormone had no effect on accumulation of either transcript. [C] 2001 Academic Press Key Words: MHR4; [Beta]FTZ-F1; 20-hydroxyecdysone; transcription factor; nuclear receptor; Manduca.

The neuromuscular system of Drosophila has been widely used in studies on synaptic development. In the embryo, the cellular components of this model system are well established, with uniquely identified motoneurons displaying specific connectivity with distinct muscles. Such knowledge is essential to analyzing axon guidance and synaptic matching mechanisms with single-cell resolution. In contrast, to date the cellular identities of the larval neuromuscular synapses are hardly established. It is not known whether synaptic connections seen in the embryo persist, nor is it known how individual motor endings may differentiate through the larval stages. In this study, we combine single-cell dye labeling of individual synaptic boutons and counterstaining of the entire nervous system to characterize the synaptic partners and bouton differentiation of the 30 motoneuron axons from four nerve branches (ISN, SNa, SNb, and SNd). We also show the cell body locations of 4 larval motoneurons (RP3, RP5, V, and MN13-Ib) and the types of innervation they develop. Our observations support the following: (1) Only 1 motoneuron axon of a given bouton type innervates a single muscle, while up to 4 motoneuron axons of different bouton types can innervate the same muscle. (2) The type of boutons which each motoneuron axon forms is likely influenced by cell-autonomous factors. The data offer a basis for studying the properties of synaptic differentiation, maintenance, and plasticity with a high cellular resolution, o 2001 Academic Press Key Words: bouton; Drosophila; larva; motoneuron; neuromuscular; single cell; synapse.

E.H. Barman [*] ABSTRACT Identification of the larva of Agabus disintegratus (Crotch) was confirmed by culturing mature larvae from ephemeral central Georgia habitats into the adult stage. Hydroporus signatus youngi [...]

Striking morphological differentiation among individuals structures the complex societies found in insects such as termites, bees, and ants. Castes have also evolved in other insects such as aphids, thrips and polyembryonic wasps. Copidosoma floridanum is a polyembryonic parasitoid wasp that produces two castes during development from a single egg. Polyembryonic development results in a single brood containing approximately 1000 reproductive larvae that develop into adult wasps and 50 precocious larvae that function as soldiers. We examined how the single egg proliferates and responds to environmental factors to produce two castes in C. floridanum. We conducted transplantation experiments of wasp embryos from all developmental stages into unparasitized hosts from all developmental stages. By transplanting wasp embryos of a particular stage into different host environments, we partitioned the effects of the intrinsic properties of the embryos from the extrinsic factors (i.e. -- the host environment) influencing caste fate. Our results indicate that both intrinsic and host environmental factors affect caste formation in this species.

Mature 4th instar larval Aedes aegypti measuring 6.5 [+ or =] 0.19 mm in length have a stomach region of 3.3 [+ or -] 0.18 mm (N=6). The stomach is clearly differentiated into distinct anterior, transitional and posterior regions (53.0 [+ or -] 1.1 6%, 13.7 [+ or -] 1.1 6%, and 33.3 [+ or -] 0% of total stomach length respectively). The anterior stomach consists of cells that range from 5.7 to 44.4 mm in diameter (mean 28.6 [+ or -] 1.68 mm). These cells are uniform in appearance and show a normal distribution by diameter. They have polygonal, flat apical surfaces with very short microvilli (0.4 [+ or -] 0.02 mm). There are no intercellular clefts apparent at the level of SEM, rather the surface of the epithelium is smooth. The most anterior cells of the transitional region are similar in appearance to cells of the preceding anterior stomach region but have microvilli 1.2 [+ or -] 0.03 mm in length. Microvillar length increases to 2.3 [+ or -] 0.26 mm in the mid-transitional region, and to 4.2 [+ or -] 0.25 mm in the posterior transitional region. The mean diameter of transitional region cells is 21.0 [+ or -] 1.26 mm. The transitional region cells show a progression to a more rounded apical profile from anterior to posterior. Posterior stomach cells are characterized by globular protrusions of the apical surface that are separated by relatively deep clefts containing numerous microvilli, that were not observed in other stomach regions. Posterior stomach cell diameter is uniformly 19.7 [+ or -] 1.08 mm throughout the anterior 2/3 of the posterior Stomach (N=22) and increases to 26.2 [+ or -] 1.45 mm (N = 8) in the posterior third of the posterior stomach region (P [is less than] 0.0005).

MATTHEW P. AYRES [1,5] RICHARD T. WILKENS [2] JONATHAN J. RUEL [3] MARIA J. LOMBARDERO [1] ERICH VALLERY [4] Abstract. The nitrogen content of plant tissue is low relative to [...]

MIKKO KUUSSAARI [13] MICHAEL SINGER [2] ILKKA HANSKI [1] Abstract. We studied host plant abundance, host use, and oviposition preference in metapopulations of the butterfly Melitaea cinxia within an area [...]

Our genetic dissection of behavior has isolated scribbler (sbb), a vital gene that encodes a novel protein expressed in the embryonic and larval nervous systems and in the imaginal discs. Larvae with mutations in sbb exhibit abnormally high amounts of turning behavior in the absence of food sbb is a large gene spanning [is greater than] 50 kb of genomic DNA with four major developmentally regulated transcripts. Transgenic rescue of scribbler behavior was demonstrated by targeting expression of a normal sbb transgene ([sbb.sup.+]) expressing one of the major transcripts to the nervous system. The vital function of sbb was restored by ubiquitous expression of this transgene throughout development.

E.H. Barman [*] ABSTRACT Larvae of Dytiscus carolinus Aube were collected between mid-February and early April from an oligoxeric marsh and cultured to the adult stage. The occurrence of larvae [...]

Specialist herbivores are linked to their host plants through a variety of mechanisms from oviposition cues, to cues to feed on the host the larval herbivore finds itself, to non-tolerance of a host once feeding is initiated. In order to examine the diet breadth of the Giant Swallowtail, Papilio (=Heraclides) cresphontes, in south Florida, I examined survival and development time of larvae to pupation on both the host plants on which eggs were laid and of an alternate host plant that I switched eggs to. Giant Swallowtails range from North America through northern South America, where they specialize on the family Rutaceae. There were three control groups (larvae raised on their natal host plant): Casimiroa edulis, Zanthoxylum fagara, and Z. coriaceum, hereafter referred to CE, ZF and ZC. There were two treatment groups: ZF to CE, and ZC to ZF. Survival in the control groups was either nearly complete (CE and ZF) or an utter failure (ZC). In the treatment groups, survival was complete on ZC, and nearly complete on CE. Among larvae in the control groups, larvae raised on CE took significantly less time to develop than that raised on ZE When I switched eggs from ZF to other plants, the mean number of days to develop reflected that change. Eggs switched to CE pupated after a time intermediate to those raised on a natal plant of ZF or CE. It is interesting to note that the longest development time is that of larvae switched to a palatable plant (ZF) from one they fail to accept as a host (ZC). Additionally, while CE is exotic in Florida, its range includes other portions of the Giant Swallowtail's range. It appears that host plant usage in the Giant Swallowtail is genetically determined, likely as a result of all three mechanisms.

The Tribolium castaneum homeotic gene maxillopedia (mxp) is the ortholog of Drosophila proboscipedia (pb). Here we describe and classify available mxp alleles. Larvae lacking all mxp function die soon after hatching, exhibiting strong transformations of maxillary and labial palps to legs. Hypomorphic mxp alleles produce less severe transformations to leg. RNA interference with maxillopedia double-stranded RNA results in phenocopies of mxp mutant phenotypes ranging from partial to complete transformations. A number of gain-of-function (GOF) mxp alleles have been isolated based on transformations of adult antennae and/ or legs toward palps. Finally, we have characterized the mxp expression pattern in wild-type and mutant embryos. In normal embryos, mxp is expressed in the maxillary and labial segments, whereas ectopic expression is observed in some GOF variants. Although mxp and Pb display very similar expression patterns, pb null embryos develop normally. The mxp mutant larval phenotype in Tribolium is consistent with the hypothesis that an ancestral pb-like gene had an embryonic function that was lost in the lineage leading to Drosophila.

CHARLES W. Fox [1] Louis Calder Center, Biological Field Station and Department of Biological Sciences, Fordham University, 53 Whippoorwill Road, Box K, Armonk, New York 10504 USA Abstract. Texas ebony [...]

E.H. Barman [*] ABSTRACT Mature larvae of two species of the semivittatus-group, Agabus stagninus Say and A. semivittatus LeConte, were cultured into the adult stage. Descriptions of mature larvae were [...]

DAVID A. BOUGHTON [1] Department of Zoology, University of Texas, Austin, Texas 78712 USA Abstract. In heterogeneous landscapes, a species' habitat may be partitioned into sources and sinks. Conceptually, three [...]

The basic helix-loop-helix transcription factor Twist is required for normal development of larval and adult somatic muscles in Drosophila. Adult flies normally have six pairs of dorsal longitudinal indirect flight muscles (DLMs), whereas when Twist function is reduced, only three pairs of DLMs are formed. Although twist is expressed in precursors of adult muscles throughout the larval and early pupal stages, we demonstrate that Twist function is required only during the late larval stage for DLM patterning. In wild-type flies, this is just prior to the time when three pairs of persistent larval muscle fibers split longitudinally to form templates for the six pairs of DLMs. By examining sections at various times during pupal development, we found that splitting of the larval muscles does not occur in twist mutants, indicating that Twist function is required to induce major changes in the larval templates prior to differentiation. The function of Twist in larval muscle splitting is likely mediated by myocyte enhancer factor-2 (MEF2) since in Mef2 hypomorphic mutants splitting is also reduced and Mef2 expression is dependent upon Twist. Our findings define specific roles for Twist and MEF2 during pupal myogenesis and demonstrate that these transcription factors function in adult muscle precursor cells to regulate downstream factors controlling muscle cell splitting and morphogenesis. Key Words: Twist; MEF2; Drosophila; adult myogenesis; imaginal discs; patterning.

Light perception is a highly useful skill. Like other animals, we humans rely on vision to navigate, to locate food and mates, and to avoid predators. But biological applications of [...]

The ontogenies of three new species of Telephinidae, Telephina calandria, Telephina chingolo, and Telephina problematica are described from Arenig-Caradoc strata in the Argentine Precordillera, and compared with the larval stages of some other Proetida, including other telephinids. New findings reveal 1) a radical metamorphosis in the ontogenies of these Telephina species late in the meraspid period, not previously described among Trilobita; and 2) distinctive hypostomes of Telephinidae containing long, thin anterolaterally and dorsally splayed anterior wings. Early ontogenies of different species currently assigned to the genus Telephina fall into at least two distinct morphological and life history groups, and hypostomes (if correctly assigned in previous works) vary significantly. The three new species strengthen the hypothesis of a phylogenetic connection between Oopsites and Telephina. Three morphological types of protaspid instars are described for proetide trilobites. Two are anaprotaspides, and the third is a metaprotaspis. They always occur in the same sequence in the ontogeny, but no cases are known of all three types in the same species. These larval types are important for understanding the systematics and life cycles of the Proetida. Benthic/pelagic transitions identify four life history patterns among the the Proetida. The best larval synapomorphy for the Proetida is the distinctive metaprotaspid larval type, which is absent in very few proetides (some Telephinidae), perhaps as a result of heterochronic displacement of this stage into the meraspid period.

How is perception of a smell kept stable over a range of concentrations? Drosophila melanogaster larvae (pictured below) are attracted to the fruity odour of ethyl butyrate across a 500-fold [...]

Ophthalmomyiasis is a condition in which the eye is infested by larvae of the sheep nasal bot fly, Oestrus ovis. This fly is found in sheep herding areas of the Mediterranean, Asia and the Americas. During the summer, the adult female fly deposits her larvae in the nostrils of sheep and goats; occasionally humans may be the target and direct infestation of the conjunctiva can occur. A report is presented of a 32-year-old woman who felt a foreign-body sensation in her eye while she was sunbathing in her garden in Dorset, England. A fly had landed on her closed eyelid; she had difficulty brushing away the fly and a foreign-body sensation persisted. She examined her eye, and found and removed several moving larvae from her conjunctiva (mucous membrane lining the eyelids and anterior surface of the eyeball). At the hospital several more larvae were removed; they were identified to be oestrus ovis. The patient received prednisolone eye drops and chloramphenicol drops, and the eye condition improved. She developed unilateral sneezing and runny nose, but examination did not reveal any larvae and the symptoms resolved within several days. She had no residual eye problems from the infestation. If the larvae are removed promptly they are relatively harmless; they do not burrow so they remain on the outer membranes of the eye. It is rare for this type of eye infestation to occur in Western Europe. (Consumer Summary produced by Reliance Medical Information, Inc.)

Saline-tolerance has evolved in mosquito larvae several times in various genera. The Ochlerotatusgenus is of interest because there are both freshwater and saline-tolerant forms within this group and both forms are osmoregulators. The physiological ability to cope with saline water versus freshwater in the Ochlemtatus mosquitoes is associated with a morphological difference in the rectum, an organ that serves an osmoregulatory function in these insects. The saline-tolerant forms have a two-part rectum while the freshwater obligates have a one-part rectum. Of the many species of this genus whose saline-tolerance has not been described, we have collected several in their larval stages. Our study includes 16 Ochlerotatus species collected in North America and one closely related and saline-tolerant New Zealand Opifex species. For each species we performed a morphological analysis of the larval recta. To determine saline-tolerance, mosquito larvae were gradually taken from dilute water to water adjusted up to 1000 mOsm using InstantOcean. Those with high survival to pupation in solutions up to 1000 mOsm were determined to be saline-tolerant. We then looked at the evolutionary patterns of saline-tolerance in this genus by mapping this character onto a phylogenetic tree. We constructed this tree by PCR amplifying and direct sequencing of the 18s rDNA gene, the D2 region of the 28s rDNA gene and two mitochondrial genes, COI and COII for each species. We then used PAUP 4.0 to construct and analyze a phylogenetic tree. Our tree does not suggest a single point when the saline-tolerant and freshwater forms split. Instead, it provides evidence that saline-tolerance evolved once from a freshwater ancestor and was subsequently lost or arose multiple times.

The density of corn pollen on leaves of milkweed plants inside and outside of cornfields was measured in several studies from different localities. The purpose was to obtain a representative picture of naturally occurring pollen densities to provide a perspective for laboratory and field studies of monarch larvae feeding on milkweed leaves with Bt corn pollen. Pollen density was highest (average 170.6 grains per c[m.sup.2]) inside the cornfield and was progressively lower from the field edge outward, falling to 14.2 grains per c[m.sup.2] at 2 m. Inside the cornfield, and for each distance from the field edge, a frequency distribution is presented showing the proportion of leaf samples with different pollen densities. Inside cornfields, 95% of leaf samples had pollen densities below 600 grains per c[m.sup.2] and the highest pollen density observed was 1400 grains per c[m.sup.2], which occurred in a study with a rainless anthesis period. All other studies had rainfall events during the anthesis period. A single rain event can remove 54-86% of the pollen on leaves. Leaves on the upper portion of milkweed plants, where young monarch larvae tend to feed, had only 30-50% of the pollen density levels of middle leaves.

To assess the likelihood that monarch larvae will be exposed to Bacillus thuringiensis (Bt) pollen, we studied milkweed and monarch densities in habitats which comprise much of the land available to breeding monarchs, e.g., cornfields, cornfield edges, other agricultural fields, and nonagricultural areas, in four regions of the monarch breeding range. We found that monarchs use milkweed in cornfields throughout their breeding season, and that per plant densities are as high or higher in agricultural habitats as in nonagricultural habitats. As a result of the prevalence of agricultural land, most of the monarchs produced in the upper Midwest are likely to originate in cornfields or other agricultural habitats. There was a greater temporal overlap between susceptible monarchs and corn anthesis in the northern than the southern part of the summer breeding range, because of earlier pollen shed in the south. The importance of agricultural habitats to monarch production suggests that, regardless of the impact of genetically modified crops, agricultural practices such as weed control and foliar insecticide use could have large impacts on monarch populations.