Days Of Larval Development Research Articles

How honeybees ( Apis mellifera L.) change their broodcare behaviour in response to non-foraging conditions and poor pollen conditions

We observed the nursing of larvae during all 5 days of larval development. We caged a queen in a specific area of empty combs inside the broodnest and filmed nursing episodes within this area. We created 5-day observation periods with and without artificial rain, as well as periods with and without manual reduction of pollen stores and reduction of pollen income. In rain periods, there were significantly fewer nursing episodes for young larvae (1–3 days old) than in no-rain periods. The nursing frequency was significantly correlated with the amount of pollen in the hive, as well as with the total amount of unsealed larvae. The ratio of available pollen to larvae had the strongest influence on the nursing frequency: the more pollen available per larva, the higher the nursing frequency of young larvae. Higher nursing frequency, as well as a longer total duration of nursing episodes, resulted in a higher protein content of the larvae. In contrast, the frequency of nursing of older larvae (4 days old) did not depend on the amount of pollen or on the ratio of pollen to larvae, even after some days of severe pollen reduction. The amount of honey stores and the weight of the hive were not correlated with the nursing frequency of any larval age group. When pollen becomes scarce, older larvae receive preferential treatment. They represent a considerable investment for the colony. From an economic point of view, it is important for the colony that they reach the "safe" final capping stage.

Aging and development in social insects with emphasis on the honey bee, Apis mellifera L.

Honey bee colonies typically consist of about 20-40 thousand workers, zero to few thousand males (drones), depending on the time of year, and a single queen, the mother of the colony. Workers typically live 3-6 weeks during the spring and summer and can live about 4months during the winter. Queens are longer lived. Anecdotes of queens living 2-3years are not unusual, though they normally live less than a year in commercial hives. Little is known about the life span of drones. Queens develop from fertilized eggs that are not different from the eggs that develop into workers. Queens are, however, twice as large, have specialized anatomy, live much longer, and develop faster from egg to adult. All of these differences are derived from differences in larval rearing environment, primarily nutrition. The developmental trajectory of a female larva from worker into a queen can be determined as late as the third day of larval development, after this time the developmental pathway is fixed for a worker phenotype. The total time of larval development is only 5-6 days, therefore, just 2-3 days of differential feeding can lead to profound differences in development, and longevity. Workers undergo age development after they become adults. Workers usually initiate foraging behavior when they are 2-3 weeks old. The age at which a worker initiates foraging is a strong determinant of her length of life. This is presumed to be a result of the hazards of foraging, but natural senescence also occurs. Some bees remain in the nest and are never observed to forage, thereby outliving their forager sisters. Corresponding to this behavioral development are changes in the sizes of glands and the production of glandular products, increases in biogenic amine titers within the brain, an increase in the volume of specific regions of the brain, and changes in the neural system that affect perception of stimuli, and learning and memory. These age-related changes in behavior are regulated by intrinsic and extrinsic factors. Genetic variation has been demonstrated for many of these life history and behavioral traits. Selection and genome mapping studies have demonstrated relationships between the neural system, behavior, and life history traits.

Development and role of GABA(A) receptor-mediated synaptic potentials during swimming in postembryonic Xenopus laevis tadpoles.

We have investigated the contribution of GABA(A) receptor activation to swimming in Xenopus tadpoles during the first day of postembryonic development. Around the time of hatching stage (37/8), bicuculline (10-50 microM) causes a decrease in swim episode duration and cycle period, suggesting that GABA(A) receptor activation influences embryonic swimming. Twenty-four hours later, at stage 42, GABA(A) receptor activation plays a more pronounced role in modulating larval swimming activity. Bicuculline causes short, intense swim episodes with increased burst durations and decreased cycle periods and rostrocaudal delays. Conversely, the allosteric agonist, 5beta-pregnan-3alpha-ol-20-one (1-10 microM) or the uptake inhibitor, nipecotic acid (200 microM) cause slow swimming with reduced burst durations and increased cycle periods. These effects appear to be mainly the result of GABA release from the spinal terminals of midhindbrain reticulospinal neurons but may also involve spinal GABAergic neurons. Intracellular recordings were made using KCl electrodes to reverse the sign and enhance the amplitude of chloride-dependent inhibitory postsynaptic potentials (IPSPs). Recordings from larval motoneurons in the presence of strychnine (1-5 microM), to block glycinergic IPSPs, provided no evidence for any GABAergic component to midcycle inhibition. GABA potentials were observed during episodes, but they were not phase-locked to the swimming rhythm. Bicuculline (10-50 microM) abolished these sporadic potentials and caused an apparent decrease in the level of tonic depolarization during swimming activity and an increase in spike height. Finally, in most larval preparations, GABA potentials were observed at the termination of swimming. In combination with the other evidence, our data suggest that midhindbrain reticulospinal neurons become involved in an intrinsic pathway that can prematurely terminate swim episodes. Thus during the first day of larval development, endogenous activation of GABA(A) receptors plays an increasingly important role in modulating locomotion, and GABAergic neurons become involved in an intrinsic descending pathway for terminating swim episodes.

Effect of the microalga Pavlova lutheri (Droop) Hibberd cultured with agricultural fertilizers on the growth and survival of larvae and postlarvae of the mussel Mytilus edulis (L.)

An evaluation was made of the growth and survival of Mytilus edulis larvae to metamorphosis, fed on Pavlova lutheri cultured with three nitrogen sources: two agricultural fertilizers (urea and ammonium sulphate) and laboratory-grade nitrate (medium f/2). In the larval stage, survival between trials was greater than 92.0%, whereas total survival was greater than 87.0% and there were no significant differences between the three treatments. Growth of larvae fed Pavlova lutheri cultured with ammonium sulphate and f/2 was the same during the first 20 days of larval development, except on days 6 and 10. Lesser growth occurred in the treatment with urea and there were significant differences relative to the other two treatments, except on day 20 when growth was the same as in the treatment with ammonium sulphate. Seed survival was better in the two treatments with agricultural fertilizers, with no differences between the two, than in the f/2 treatment, with significant differences relative to urea and ammonium sulphate. Better seed growth was obtained in the treatment with ammonium sulphate, whereas growth in the urea and f/2 treatments was similar and there were no significant differences between the two. The results indicate that urea and ammonium sulphate, especially the latter, can be considered good alternatives for use in the laboratory production of microalgae, reducing costs by 98.81% relative to f/2.

Biochemical characterization of cuticle polypeptides from the infective larvae of Haemonchus contortus

1. 1. Ecdysis of infective Haemonchus contortus larvae is effected by the enzymatic degradation of a specialized region of the second molt cuticle containing a biochemically unique polypeptide (mol. wt = 160,000). 2. 2. The 160,000 mol. wt polypeptide and related polypeptides are synthesized at approximately 6 days of larval development. Antigenically similar polypeptides occur in other ruminant trichostronglyes. 3. 3. Cuticle polypeptides digested during ecdysis differ from second molt cuticle collagnes in amino acid composition and collagenase sensitivity. However, some antigenic homology between the 160,000 mol. wt polypeptide and cuticle collagens suggests structurally similar regions.

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk‐sac, preflexion, flexion and post‐flexion larval stages.Oxygen uptake rates of eggs increased linearly from 0.024 μl O2 per egg h‐1 (0·323 μl O2 mg‐1 dry wt h‐1) by blastulae to 0·177 μlO2 per egg h‐1 (2·516 μlO2mg 1dry wth‐1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%0).Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O2 per larva h‐1 shortly after hatching to 18·880 μl O2 per larva h‐1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass‐specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O2 mg 1dry wt h‐1).Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk‐sac larvae (Q10= 2·75) than in postflexion larvae (Q10= 1·40).

Glutathione S-transferase 1 and 2 in susceptible and insecticide resistant Aedes aegypti

Glutathione S-transferase enzymes (GST) were characterized in permethrin and in DDT resistant and susceptible strains of Aedes aegypti. The predominant GST, designated GST-1, was purified from susceptible and resistant larvae using S-hexyl-glutathione affinity chromatography and anion-exchange chromatography. Rabbit antiserum directed against the 26.8-kDa GST-1 subunit purified from the susceptible strain was specific for a 26.8-kDa subunit in the resistant strain. There was no significant difference in enzyme kinetic constants ( K m and V max) between GST-1 from susceptible and resistant strains. GST-1 enzyme activity varied during larval development in both resistant and susceptible strains, but was approximately 1.7 times greater in resistant larvae and pupae throughout development. The GST-1 amount (measured using a radioimmunoassay) also varied during development, and was generally higher in resistant larvae and pupae. GST-1 enzyme activity measured each day during the 6 days of larval development was significantly correlated with GST-1 protein amount on each of the previous days, suggesting that an inactive enzyme form is converted to the active form approximately 24 hr after it is synthesized. Another GST enzyme, GST-2, was also found in resistant and susceptible A. aegypti larvea. GST-2 was partially purified from resistant larvae using S-2,4-dinitrophenylglutathione affinity chromatography and anion-exchange chromatography. GST-2 has a molecular mass of 28 kDa, and an isoelectric point of less than 5.0. GST-2 was not cross-reactive with GST-1 antiserum. GST-2 enzyme activity varied during the development of both susceptible and resistant larvae, but the pattern was different than that for GST-1. Throughout development, GST-2 enzyme activity was substantially higher (approximately eight-fold) in resistant strains of A. aegypti compared to susceptible strains.

Functional redundancy in the tissue-specific enhancer of the Drosophila Sgs-4 gene.

During the last day of larval development, the Sgs-4 glue gene of Drosophila melanogaster is expressed at high levels in a single tissue, the larval salivary glands. As shown by transformation experiments and by DNA sequence analysis of Sgs-4 underproducing strains, an essential regulatory region for Sgs-4 expression lies between 149 and 568 bp upstream from the transcribed part of the gene. This region shows the positional independence of a transcriptional enhancer and directs at least three regulatory activities: tissue specificity, developmental timing and high-level expression. Here we use a transient transformation assay to identify three elements within this enhancer that are involved in tissue specificity. For at least this regulatory activity the enhancer is internally redundant. Any pairwise combination of the three elements is sufficient to direct salivary gland expression, although none of the three can act alone.

Thyroxine content of eggs and larvae of coho salmon, Oncorhynchus kisutch

AbstractThe whole‐animal content of the thyroid hormone thyroxine (T4) was measured in embryonic and larval coho salmon (Oncorhynchus kisutch) by radioimmunoassay following the validation of an extraction method. The embryonic yolk, at 20 days after fertilization and 10 days before hatching, was found to have 5.3 ± 0.3 ng T4 (mean ± SEM). At hatching, the total T4 content decreased to 4.4 ± 0.3 ng, of which 96% remained in the yolk and 4% was distributed in the larva. T4 content decreased to 1.5 ± 0.1 ng during the 30 days of larval development. The first increases in T4 were detected within 2 weeks following emergence from the substrate of the actively feeding juvenile; the newly emerged salmon responds significantly to bovine TSH. The presence and clearance of T4 from the yolk suggest that T4 may be critical to normal larval morphogenesis, that initially the T4 is of maternal origin, and that the hypothalamo‐adenohypophysial‐thyroid axis begins to function independently at or near the time of emergence.

Reduction in the critical number of short days for pupal diapause in Papilio machaon with precocious metamorphosis

Normal and allatectomized larvae of Papilio machaon were transferred from short (light:dark 10:14) to long (light:dark 16:8), or long to short days, on successive days of larval development to examine the critical number of short days necessary for diapause induction. The reciprocal transfer revealed that the normal larvae required 12 consecutive short days during the early instars to raise the incidence of pupal diapause to 50%. The critical number of short days was reduced to 9.5 days when the length of the larval period was cut due to precocious pupation induced by allatectomy. The reduction in the critical number of short days with precocious metamorphosis was less remarkable when the larvae were exposed to short days during the late instars. A possible summation mechanism of photoperiodic information for diapause induction in P. machaon is presented to explain the results obtained.

Transcription of tandemly repeated genes in embryonal and larval tissues of Calliphora erythrocephala

The transcription of rRNA genes in Calliphora erythrocephala embryonal and larval fat bodies and guts was analyzed by electron microscopy. A gradual increase in the number of active genes and in the RNA polymerase density was observed in both tissues in the hours preceding hatching. Despite this increase, the rRNA genes at hatching are not fully loaded with RNA polymerase molecules. An additional increase in rRNA synthesis is characteristic of the first two days of larval development. This increase in rRNA synthesis is accomplished by an increase in RNA polymerase density, by activation of previously inactive rRNA genes, and by activation of newly replicated rRNA genes. The rRNA seems to be generated exclusively on genes not interrupted by a 6.1 kb intervening sequence. After the first 2 days, the RNA polymerase densities decline. Synthesis of rRNA seems to be coordinately regulated in these two tissues. — Two classes of tandemly repeated nonribosomal transcription units were detected in the fat bodies. The first class has an estimated DNA length of 3.3 kb and cannot be assigned to any of the known genes. The second class appears to represent very short transcription units with no visible RNP fibrils and is a candidate for 5S or tRNA transcription units.

Influence of juvenile hormone on gravity orientation in the female honeybee larva (Apis mellifera L.)

The influence of juvenile hormone (JH) on the behaviour of the female honeybee larva (Apis mellifera L.) during ultimate orientation was investigated. The effect of gravity was tested in natural and artificial cells by changing their inclination and by rotation experiments. In queen larvae ultimate orientation (final orientation at the outset of metamorphosis) is controlled by gravity. They display a positive geotaxis under all experimental conditions tested even in reversed natural cells. However, ultimate orientation of worker larvae in natural cells is not affected by gravity. A positive geotactic preference is shown only in long artificial cells whereas larvae in short cells respond indifferently to gravity. The texture of the cell ending has a directing effect. The geotactic indifference is replaced by a positive geotaxis in worker larvae treated with JH-I or JH-III during the third day of larval development (Fig. 5). In JH-treated larvae the evaluation of gravity equals that of queen larvae (Fig. 7). A positive geotaxis is evoked even in individuals that develop rather weak adult queenlike characteristics (Table 2). The juvenile hormone titer not only controls the differentiation of morphological and anatomical caste characteristics but also affects the orientation behaviour of the spinning larva.

A Comparative Study of the Endocrine System of the Honey Bee Larvae under Normal and Experimental Conditions

Abstract The endocrine system of the honey bee (Apis mellifera L.) has been studied morphologically through post-embryonic development with several histological techniques. Marked differences in the structure of the neurosecretory complex of queen and worker larvae have been observed during larval stages. In queen larvae, morphogenesis of the neurosecretory cells, their axons and the formation of the chiasma takes place during end of 2nd and beginning of 3rd, in the workers at beginning of 4th larval instar. Stainable neurosecretory material was found in queen larvae at the beginning, in worker larvae at the end of 4th instar. In early larval stages, the corpora allata are more active in the queen. During initial 3 - 5 days of larval development the gland volume is reduced in both castes. After 36 to 48 hours of endocrine retardation, the glands become active again. The same histological effects are found under experimental conditions, where worker larvae of 2nd instar were reared in the incubator on basic food, Royal Jelly and with topically applied juvenile hormone I.

Fatty acid synthetase complex from the insect Ceratitis capitata

Fatty acid synthesis capacity of the insect Ceratitis capitata has been investigated in vitro from [1- 14C]acetyl-CoA using homogenates at different stages of development. A maximum activity was observed after 5–6 days of larval development. But homogenates of the pharate adult insect did not show synthetic capacity of fatty acids. Fatty acid synthetase complex has been isolated from the particle-free supernatant fraction of homogenates from the 6-day C. capitata larvae. The enzyme complex was purified 182-fold with respect to the protein contained in the crude extract. The complex was homogeneous when analysed by gel filtration and by polyacrylamide-gel electrophoresis. The molecular weight was 5.2 × 10 5. The enzyme was dissociated into half-molecular subunits. Amino acid analysis, general properties, stability and kinetic constants ( V and K m ) for the substrates are reported. The fatty acid synthetase complex from the insect contains 42 ± 1-SH residues and one phosphopantetheine moiety per 5.2 × 10 5. Activity was dependent on the presence of NADPH; FMN strongly inhibited the enzyme activity promoted by NADPH. The enzyme complex synthesized a range of fatty acid (10:0–18:0), palmitate being the predominant end product. The proportions of fatty acids synthesized varied with substrate concentrations. Fatty acids released from the complex were almost completely in the free form.

Action of Bracon hebetor1 Say as a Parasite of Plodia interpunctella2 at Controlled Densities3

Under controlled conditions of 27°C and 60% relative humidity, standard populations of about 1800 larvae of the Indian meal moth, Plodia inter punctella (Hubner), were allowed to proceed through 12 days of larval development. Adults of the braconid parasite Bracon hebetor Say were then introduced at 9 different densities and with a sex ratio of 2 ♀ : 1 ♂. Tests at each density were replicated and randomized, and each experiment was terminated before the initiation of a 2nd host generation. Equilibrium was not sought, but rather the optimum ratio of parasite:host density for most efficient immediate control of the host. At an introduction of 250 ♀ Bracon , 97% of Plodia larvae were killed. Higher numbers of female Bracon up to 1000 did not increase this mortality significantly. The sex ratio of surviving Plodia in a parasitized colony was found to be dependent on the density of female Bracon . A significantly larger number of female larvae were parasitized in preference to male. The sex ratio of Bracon in the F1 generation appeared also to vary with the host:parasite density ratio. The female:male ratio of F1 Bracon showed a quadratic relationship, with a maximum number of female F1 at the 250-♀ wasp density.