Chemical mimicry of the ant Oecophylla smaragdina by the myrmecophilous spider Cosmophasis bitaeniata: Is it colony-specific?

Workers of most social insects can distinguish between nestmates and non-nestmates, and actively attack the latter if they attempt to intrude into the nest or surrounding territory. Nevertheless, there are many records of heterospecific organisms living within the nests of social insects, and they are thought to gain access through chemical mimicry. The salticid spider Cosmophasis bitaeniata lives within the leaf nests of the ant Oecophylla smaragdina, where it preys on the ant larvae. We investigated, using behavioural bioassays and chemical analyses, whether the previously reported resemblance of the cuticular hydrocarbons of ant and spider was colony-specific. Behavioural experiments revealed that the spiders can distinguish between nestmate and non-nestmate major workers and are less inclined to escape when confined with ants that are nestmates. More significantly, C. bitaeniata were more likely to capture ant larvae from nestmate minor workers than non-nestmate minor workers. The chemical analyses revealed that the cuticular hydrocarbon profiles of the spiders and the major workers of the ant colonies were colony-specific. However, the hydrocarbon profiles of C. bitaeniata do not match those of the major workers of O. smaragdina from the same colony. Perhaps the colony-specific cuticular hydrocarbon profiles of C. bitaeniata function to obtain prey from the minor workers rather than avoid eliciting aggression from the major workers.     

Inhibition of vitamin D metabolism by ethane-1-hydroxyl-1, 1-diphosphonate

The administration of disodium-ethane-1-hydroxy-1,1-diphosphonate (20 mg/kg body weight subcutaneously) to chicks given adequate amounts of vitamin D₃ causes a hypercalcemia, inhibits bone mineralization, and inhibits intestinal calcium transport. The administration of 1,25-dihydroxyvitamin D₃, a metabolically active form of vitamin D₃, restores intestinal calcium absorption to normal but does not restore bone mineralization in disodium-ethane-1-hydroxy-1,1-diphosphonate-treated chicks. In rachitic chicks, the disodium-ethane-1-hydroxy-1,1-diphosphonate treatment does not further reduce the low intestinal calcium transport values while it nevertheless further reduces bone ash levels and increases serum calcium concentration.These observations prompted a more detailed study of the relationship between disodium-ethane-1-hydroxy-1,1-diphosphonate treatment and vitamin D metabolism. A study of the hydroxylation of 25-hydroxyvitamin D₃ in an in vitro system employing kidney mitochondria from chicks receiving disodium-ethane-1-hydroxy-1,1-diphosphonate treatment demonstrates a marked decrease in 1,25-dihydroxyvitamin D₃ production and a marked increase in the 24,25-dihydroxyvitamin D₃ production. In addition, the in vivo metabolism of 25-hydroxy-[26,27-³H]vitamin D₃ in disodium-ethane-1-hydroxy-1,1-diphosphonate treated chicks supports the in vitro observations. In rachitic chicks the disodium-ethane-1-hydroxy-1,1-diphosphonate treatment markedly reduces the 25-hydroxyvitamin D₃-1-hydroxylase activity of kidney, but does not increase the 25-hydroxyvitamin D₃-24-hydroxylase.These results provide strong evidence that large doses of disodium-ethane-1-hydroxy-1,1-diphosphonate produce a marked effect on calcium metabolism via alterations in the metabolism of vitamin D as well as the expected direct effect on the bone.     

Water as an Essential Resource: Orb Web Spiders Cannot Balance Their Water Budget by Prey Alone

Water is essential for all living organisms because it acts as a major solvent and reaction medium. Terrestrial animals may lose water through evaporation and excretion and consequently have evolved strategies to balance their water budget by either minimising losses or by gaining water. The major pathway to gain water is via food intake, although many animals additionally drink free water. Spiders acquire substantial amounts of water by ingesting enzymatically liquefied prey. However, this may not account for the water needs of some species. We tested whether drinking is essential for orb web spiders of the genus Argiope by experimentally manipulating the diet (flies or crickets) and water supply (no water or a daily shower) to females and then measuring their subsequent drinking behaviour. Individuals of Argiope trifasciata, which are typically found in dry habitats, increased their body mass when fed crickets but not when fed flies. However, spiders deprived of water subsequently ingested significantly more water than spiders that received water every day, regardless of their feeding regime. This pattern was replicated in Argiope aetherea, which is found in the tropics and perhaps less likely to be water deprived in natural populations. Our results reveal that drinking allows these spiders to realise their water balance independent from the nutritional status. We suggest that the spiders may need to drink fresh water to process ingested nutrients.     

Mechanical Aspects of Rapid Flower Opening in Asiatic Lily

Several processes contribute to the rapid opening of Asiaticlily flowers. Opening occurs after the tepals stop increasingin length, and have reached maximum thickness. Up to day -0.5(where day 0 is time that flowers are half-open), the sepalsentirely encase the petals, and their edges are tightly claspedin deep grooves beside the petal midribs. At day -0.5 to -0.3,the petal midrib reduces in width, opening the groove and allowingthe tepals to pull apart (bud ‘cracking’). Unlockingis not complete until about day -0.15: it is not the key eventdirecting opening, but helps to sharpen its onset. The midribscontrol subsequent opening, pulling the laminae behind them.In the first 3–4 h of opening (‘dark phase’),the main process is an increase in the angles the midribs makewhere they join the pedicels. During this time, the petals andsepals are only slightly curved. Subsequently through to day0.5 (the ‘light phase’), an increasingly markedcurvature of the midribs pulls the tepals further apart andcauses them to progressively reflex. By day 1 the flowers aremature and the laminae are no longer being pulled by the midribs.In studies of isolated tissue segments, we found that in thelater stages of opening there is greater cell expansion in theepidermis of the inner surfaces, contributing to the recurving.Petal expansion is accompanied by cell separation and osmoticchanges, and inhibitors of starch hydrolysis inhibit expansionof petal segments. Of the various processes operating duringlily opening, we believe that the most influential is the changein angle between midribs and pedicel, suggesting a pulvinus-likemechanism.Copyright 2000 Annals of Botany Company Flower opening, lily, mechanics, petal lock, osmotic changes, starch, epinasty     

The uptake and metabolism of [32P]pyrophosphate by mouse calvaria in vitro

In order to study the uptake and metabolism of PP(i) by bone, (32)PP(i) was added to the medium surrounding explanted mouse calvaria maintained in organ culture. Most of the PP(i) was hydrolysed during incubation, but there was a measurable entry of intact PP(i) into bone. When (32)P(i) was added to the medium, synthesis of PP(i) and organic phosphates from P(i) was observed in bone. There was no detectable passage of PP(i) from bone into the medium. These results are discussed in terms of two models of pyrophosphate hydrolysis and exchange. Some quantitative estimates about the fate of PP(i) in bone were made.