Neuronal differentiation in cultures of weaver (wv) mutant mouse cerebellum

In the present study we report for the first time a weaver (wv) gene dose effect on neuron survival and neurite formation in vitro. Dissociated cerebellar cells from postnatal 7- and 8-day-old normal ( + / + ), heterozygous weaver ( + /wv) and homozygous weaver (wv/wv) mice were cultured as monolayers on poly-L-lysine coated glass. Cell death occurred rapidly in wv/wv cultures. Cell counts showed that less than 20% of the total neurons and neuronal precursors (identified by “birthday” radiolabeling techniques) survived by Day 3. Cell death was less extensive in + /wv cultures with 65% of the total neurons and 80% of the precursors surviving by Day 3. In contrast to wv/wv cultures, younger neurons survive better than the total population in + /wv cultures. The impairment of neurite formation over the first week is also proportional to the number of mutant genes as shown by quantitation of (a) the percentage of cells with neurites; (b) the percentage of cells with neurites of a given length class with time; (c) the lengths of the longest processes formed per cell. The mean longest neurite lengths obtained by computer digitization at 6 days in vitro were 41.8, 26.8, and 9.0 μm for + / +, + /wv, and wv/wv granule cells, respectively.     

Photoperiodic regulation of seasonal responses in Indian weaver bird (Ploceus philippinus)

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and third experiments suggest that the photoperiodic induction was depending upon duration and intensity of the light. Birds showed testicular growth-regression cycle followed by molt and plumage color change only under 13L:11D and 15L:9D and only 500- and 800-lux under 13L:11D photoperiod but not under 11.5L:12.5D and 12L:12D and 10- and 50-lux light intensities. Pre- and post-nuptial molting on body feathers were progressed with gonadal stimulation–maturation and regression cycle under 13L:11D and 15L:9D. Results under different light–dark cycles suggest that day length of about 12 h or more and above the threshold level of light intensity are essential for the induction of photoperiodic responses.     

Using insect traps to increase weaver ant (Oecophylla longinoda) prey capture

Weaver ants (Oecophylla spp.) are managed in plantations to control insect pests and are sometimes harvested as a protein‐rich food source. In both cases, the amount of insect prey caught by the ants is imperative for returns, as more prey leads to more effective biocontrol and to a higher production of ants. Malaise‐like traps placed in trees may catch flying insects without catching ants, as ants may use pheromone trails to navigate in and out of the traps. Thus, ants may increase their prey intake if they are able to extract insects caught in traps. In a mango plantation in Tanzania, we estimated the amount of insects caught by simple traps (cost per trap = 3.9 USD), and whether Oecophylla longinoda was able to collect insects from them. On average, a trap caught 110 insects per month without catching any weaver ants. The number of insects found in traps with ant access was 25% lower than in control traps (ants excluded), showing that ants were able to gather prey from the traps. Ant activity in traps increased over time, showing that prey extraction efficiency may increase as ants customize to the traps. The prey removed from traps by ants constituted 5% of the number of prey items collected by O. longinoda under natural conditions (without traps), potentially increasing to 14% if ants learn to extract all insects. Thus, prey intake may be increased with 5–14% per 3.9 USD invested in traps. These numbers increased to 38 and 78%, respectively, when light was used to attract insects during night time. Combining ant predation with insect trapping is a new approach potentially building increased returns to ant biocontrol and to ant entomophagy.     

Protein and amino acid composition of silks from the cob weaver, Latrodectus hesperus (black widow)

The silks from the cob weaving spider, Latrodectus hesperus (black widow), have been examined with the goal of expanding our understanding of the relationship between the protein structure and mechanical performance of these unique biomaterials. The scaffolding, dragline and inner egg case silks each appear to be distinct fibers based on mole percent amino acid composition and polypeptide composition. Further, we find that the amino acid composition of dragline and egg case silk are similar to the analogous silks produced by orb weaving spiders, while scaffolding silk may represent a novel silk. The black widow silks are comprised of multiple high molecular weight polypeptides, however, the egg case and scaffolding silks also contain some smaller polypeptides.     

Reduction of nerve growth factor level in the brain of genetically ataxic mice (weaver, reeler)

By a highly sensitive enzyme immunoassay we measured the level of nerve growth factor (NGF) in the cerebellum and cerebrum of the neurologically mutant mice, weaver, reeler and Purkinje cell degeneration (PCD). A significant decrease in NGF level was observed in both cerebellum and cerebrum of weaver and reeler mutants of either sex. However, there was no such difference between normals and mutants in the case of the PCD mice. These results show that weaver and reeler mice have abnormalities of NGF synthesis and/or degradation not only in the cerebellum but also in the cerebrum.     

Behavioral manipulation of the orb‐weaver spider Argiope argentata (Araneae: Araneidae) by Acrotaphus chedelae (Hymenoptera: Ichneumonidae)

We observed the first case of host‐behavioral manipulation of an orb‐weaver spider Argiope argentata induced by a parasitoid wasp of the genus Acrotaphus. The modified web is similar of those constructed by other orb weavers attacked by wasps of the close related genus Hymenoepimecis. The stick spirals and radii are absent and the web is composed of a three‐dimensional structure of non adhesive threads. The discovery of the ability to induce changes in host's web‐building behavior in Acrotaphus is indicative that this trait may be primitively present in the clade that includes the genus Hymenoepimecis.     

Naturally occurring neuronal plasticity in visual wulst of the Baya weaver, Ploceus philippinus (Linnaeus, 1766)

The visual wulst (VW), the rostro-dorsal surface of the avian telencephalon extending from the midline to the lateral region of the brain, is a laminated “bulge” consisting in four histologically distinct rostro-caudally arranged laminae with a specific sequence: hyperpallium apicale, interstitial nucleus of hyperpallium apicale, hyperpallium intercalatum and hyperpallium densocellulare. The VW has been proposed to be the avian equivalent of the mammalian striate cortex. Various behavioral studies including lesion experiments have indicated the importance of the VW, which receives visual and/or auditory cues. We have investigated qualitatively and quantitatively the fascinating structural changes occurring in VW neurons of the seasonally breeding bird, Ploceus philippinus (Linnaeus, 1766). The Golgi method was used to study the seasonal fluctuations in the neuronal classes of the VW with regard to dendritic thickness, spine morphology and spine density during both the non-breeding and breeding periods of male Baya weaver birds. Significant variations in parameters studied among the various neuronal types located in the different well-demarcated regions of the VW are believed to contribute to the functional differences reported among the wulst regions. Thus, this study extends our view demonstrating naturally occurring neuronal plasticity in a seasonally dynamic avian brain of a bird that hones not only its learning and memorizing system but also its social and sexual system in preparation for the breeding season.     

Role of melatonin in photoperiodic time measurement in the migratory redheaded bunting (Emberiza bruniceps) and the nonmigratory Indian weaver bird (Ploceus philippinus)

In the present study, we asked the question whether physiological responses to day length of migratory redheaded bunting (Emberiza bruniceps) and nonmigratory Indian weaver bird (Ploceus philippinus) are mediated by the daily rhythm of melatonin. Melatonin was given either by injection at certain times of the day or as an implant. In series I experiments on the redheaded bunting, melatonin was administered by subcutaneous injections daily at zeitgeber time (ZT) 4 (morning) or ZT10 (evening) and by silastic capsules in photosensitive unstimulated buntings that were held in natural day lengths (NDL) at 27 degrees N beginning from mid February, and in artificial day lengths (ADL, 12L:12D and 14L:10D). Melatonin did not affect the photoperiod-induced cycles of gain and loss in body mass and testicular growth-involution, but there was an effect on temporal phasing of the growth-involution cycle of testes in some groups. For example, the rate of testicular growth and development was faster in birds that received melatonin injection at ZT4 in NDL, and was slower in birds that carried melatonin implants both in NDL and ADL. In series II experiments on Indian weaver birds, melatonin was given in silastic capsules in the first week of September when they still had large gonads. Birds were exposed for 12 weeks to short day length (8L:16D; group 1), to long day length (eight weeks of 16L:8D and four weeks of 18L:6D; group 2), or to both short and long day lengths (four weeks each of 8L:16D, 16L:8D, and 18L:6D; groups 3 and 4). Whereas groups 1 to 3 carried melatonin or empty implant from the beginning, group 4 received one after four weeks. All birds underwent testicular regression during the first four weeks irrespective of the photoperiod they were exposed to or the implant they carried in, and there was a slight re-initiation of testis growth in some birds during the next eight weeks of long day lengths. However, with the exception of group 2, there was no difference in mean testis volume during the period of experiment between the melatonin- and empty-implant birds. The data on androgen-dependent beak color also supported the observations on testes. Together, these results do not support the idea that the daily rhythm of melatonin is involved in the photoperiodic time measurement in birds. However, there may still be a role of melatonin in temporal phasing of the annual reproductive cycle in birds.     

Microsatellite loci for the weaver ant Oecophylla smaragdina

We developed 13 microsatellite loci in Oecophylla smaragdina from random amplified polymorphic DNA (RAPD) fragments. These loci showed two to 14 alleles in O. smaragdina with expected heterozygosity of each locus from 0.10 to 0.89, and six were also polymorphic in the related species, O. longinoda. The results suggested that the loci will be useful to analyse the genetic structure of Oecophylla species at both the colony and population levels.     

Adaptative properties of the chemical trail system of the African weaver antOecophylla longinoda Latreille (Hymenoptera,Formicidae, Formicinae)

Summary Trail communication of the weaver antOecophylla longinoda is highly adapted to the African rain forests, insofar natural selection in the tropics might favour chemical trails which are durable in nature. A dry chemical trail can last over nine weeks, and over ten months when reinforced with fecal marking. The trail pheromones are resistant to rain, whether they are fresh or three months old, and whether they are reinforced or not with anal deposits.     

Diversity of insects captured by weaver spiders (Arachnida: Araneae) in the cocoa agroecosystem in Tabasco, Mexico

The aim of this work was to know the diversity of insects captured by weaver spiders in a plantation of cocoa (Theobroma cacao L.) of 6 ha in the State of Tabasco, Mexico. The study was carried out from July 2004 to June 2005 by means biweekly samples of the insects captured on the spiders webs. The total of 3,041 webs of 54 species of spiders belonging to seven families (Araneidae, Theridiidae, Tetragnathidae, Uloboridae, Pholcidae, Dyctinidae and Linyphiidae) were revised. We found 1,749 specimens belonging to 10 orders of insects, represented by 93 families, the majority of Coleoptera, Diptera and Hemiptera that constituted 74% of the identified families. The biggest number of specimens of all orders was captured by Araneidae, except of Isoptera, whose specimens were captured mainly by the family Theridiidae. The index of diversity (H'), evenness (J') and similarity (Is), applied to know the diversity of families of insects captured among families of spiders, varied from 0.00 to 3.24, 0.00 to 0.81, and 0.04 to 0.522, respectively. We conclude that there is a wide diversity of insects predated by the weaver spiders in the cocoa agroecosystem, and that there are species that can be promising for the biological control of pests.     

Evidence for a circadian oscillation in the gonadal response of the tropical weaver bird (Ploceus philippinus) to programmed photoperiod.

The effect of an asymmetrical skeleton photoperiod scheduleee was studied on the gonadal development in a tropical finch, the weaver bird (Ploceus philippinus). The schedul comprised a short nonstimulatory primary photoperiod of 6 hrs and a secondary much shorter lightperiod given as a 15-min light pulse at different times in the dark period. The light pulse 11 hrs after the basic period resulted in gonadal stimulation, while light pulse in contimuation with the basic period or 8, 14 or 21 hrs after the basicperiod was not stimulatory. The "photoinducible phase" was much more precisely outlined by shifting the birds from an 8-h to a 10-h pulse, and from an 11-h to 12-h pulse and was found to be very short, lasting about an hour falling between 11 and 12 hrs after the primary light period. The short photoinducible phase may be of an adaptive value since in the tropics the difference between the shortest and the longest daylength is also rather small (3 hrs and 15 min at Varanasi, 25degrees N). Clearly the weaver bird possesses a fine time-measuring device involving an endogenous circadian rhythm in photosensitivity. In nature, spermatogenesis in this bird also begins in March when the daylength exceeds 11 hrs (thus perhaps coinciding with the photoinducible phase). In rather small, photoperiod may not serve as a cue to trigger seasonal reproductive periodicity, it seems that photoperiod can act as a Zeitgeber for the initiation of spermatogenesis in the weaver bird at least.     

Comparing different methods for trapping mated queens of weaver ants (Oecophylla longinoda; Hymenoptera: Formicidae)

The predatory efficiency of African weaver ants Oecophylla longinoda and their utilisation in protein production is a function of ant abundance. Reliable control of insect pests in tropical crops is achieved when ant populations are constantly high. Transplanted populations of weaver ant colonies containing egg-laying queens are more stable than those without. Achieving such stability through collection of colonies established in the wild is usually difficult because of uncertainty in locating the nest containing the egg-laying queen. In this study, we investigated four methods that may be used to collect mated queens that subsequently can be used to stock ant nurseries. The catch efficiencies of (1) leaf traps, (2) paper traps (both types providing a refuge for founding queens), (3) random search for queens and (4) light trapping were compared. Light trapping was the most efficient way to collect queens followed by leaf traps, random search and, last, paper traps. Light trapping and random search, though, required the presence of a person throughout the ant's mating season (several months), whereas this was not required when using leaf and paper traps.