Stable carbon isotopes and the metabolism of the terrestrial Devonian organism Spongiophyton

Devonian fossils of Spongiophyton have been identified as a terrestrial evolutionary intermediate between algae and vascular land plants on the basis of their dichotomously branched, tubular morphology, thick cuticles, and the scattered distribution of surface pores. Our understanding of their physiology is, however, severely limited, but may be increased through the use of stable carbon isotope measurements. One such study led to the hypothesis that Spongiophyton carried a carbon isotope (δ¹³C) signature characteristic of lichens ( Jahren et al., 2003 Geology 31 , 99–102). Here, we outline three difficulties with accepting this idea and report independent isotopic measurements of Spongiophyton fossils from Canada and Ghana. Our results show that the isotopic discrimination of analogous tissues of Spongiophyton, extant lichens, liverworts and mosses are statistically indistinguishable. We suggest therefore that claims to have definitively identified lichen metabolism are premature, and cannot be sustained.     

Mating systems in primitive Lepidoptera, with emphasis on the reproductive behaviour of Korscheltellus gracilis (Hepialidae)

Adults of Korscheltellus gracilis (Grote) are crepuscular. Flight is restricted to two 20–40 minute periods each day: the first flight follows sunset during evening twilight, the other precedes dawn. Four to five times as many adults are active during the evening when courtship, mating and oviposition occur. Of these behaviours, only oviposition occurs during the pre-dawn period of activity. Field observations indicate that females release a sex pheromone while fanning their wings. Females usually fly before pairing. There is no obvious female choice or stereotyped courtship behaviour prior to pairing.
In some hepialid genera females attract males, while in others ( Hepialus Fabricius, Phymatopus Wallengren, Sthenopis Packard and Zenophassus Tindale) the calling system is reversed, with males attracting females. Cladistic analysis of the Hepialidae suggests that the plesiomorphic condition for the family is for females to release the long-distance attractant, and that the reversed calling system represents a derived condition restricted to lineages within a single clade.
Available information on the mating systems of other basal lepidopteran lineages and Trichoptera support the hypothesis that ancestral Lepidoptera possessed a female-released, long-range attractant. Support for this position comes from (1) published literature; (2) field observations made by DLW; (3) the apparent absence of male scent structures and recognizable male calling behaviour among the pre-Neolepidoptera; and (4) cases of male antennal elaboration in several basal lepidopteran lineages.     

A change in the breeding season of Rüppell's Griffon Vultures Gyps rueppellii in the Serengeti in response to changes in ungulate populations

Breeding by Rüppell's Griffon Vultures Gyps rueppellii is synchronized but the time of breeding of colonies in the Serengeti region of Tanzania has changed by 5 months over the period between 1969–1970 and 1985. During this interval there have been considerable changes in the ungulate populations within the feeding range of the vultures, resulting in an increase to the food supply available to the birds. It is suggested that this species may have two alternative breeding seasons, the selective value of each depending on the magnitude of the food supply.     

Cladistics of the genera of Mesochorinae (Hymenoptera: Ichneumonidae)

Abstract. A cladistic analysis is presented for the genera of the ichneumonid subfamily Mesochorinae. Nine genera are recognized as valid. Previous work on larval morphology is reviewed and a number of larvae are newly illustrated and discussed. Four new synonyms are proposed: Oncocotta, Piestetron, Plectochorus and Rhaibaspis are all synonymized with Mesochorus , and Stictopisthus is placed back as a synonym of Mesochorus. Four new genera are described: Artherola from South Africa, Chineater from Chile, Thamester from Japan, and Varnado from Morocco. A new key is provided to the mesochorine genera of the world.     

CELLULAR BIOLOGY OF BONE RESORPTION

Past knowledge and the recent developments on the formation, activation and mode of action of osteoclasts, with particular reference to the regulation of each individual step, have been reviewed. The following conclusions of consensus have emerged.
1. The resorption of bone is the result of successive steps that can be regulated individually.
2. Osteoclast progenitors are formed in bone marrow. This is followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone.
3. The exact pathways of differentiation of the osteoclast progenators to mature osteoclasts are debatable, but there is clear evidence that stromal cells support osteoclast generation.
4. Osteoclasts are activated following contact with mineralized bone. This appears to be controlled by osteoblasts that expose mineral to osteoclasts and/or release a factor that activates these cells.
5. Activated osteoclasts dissolve the bone mineral and digest the organic matter of bone by the action of agents secreted in the segregated microcompartments underlying their ruffled borders. The mineral is solubilized by protons generated from CO, by carbonic anhydrase and secreted by an ATP-driven vacuolar H⁺-K⁺-ATPase located at the ruffled border. The organic matrix of the bone is removed by acid proteinases, particularly cysteine-proteinases that are secreted together with other lysosomal enzymes in the acid environment of the resorption zone.
6. Osteoclastic bone resorption is directly regulated by a polypeptide hormone, calcitonin (CT), and locally, by ionized calcium (Ca²⁺) generated as a result of osteoclastic bone resorption.
7. There is new evidence that osteoclast activity may also be influenced by the endothelial cells via generation of products including PG, NO and endothelin.     

Characterization of Kinetoplast DNA from Phytomonas serpens

ABSTRACT. The restriction enzyme digestion of kinetoplast DNA from four Phytomonas serpens isolates shows an overall similar band pattern. One minicircle from isolate 30T was cloned and sequenced, showing low levels of homology but the same general features and organization as described for minicircles of other trypanosomatids. Extensive regions of the minicircle are composed by G and T on the H strand. These regions are very repetitive and similar to regions in a minicircle of Crithidia oncopelti and to telomeric sequences of Saccharomyces cerevisiae. Conserved Sequence Block 3, present in all trypanosomatids, is one nucleotide different from the consensus in P. serpens and provides a basis to differentiate P. serpens from other trypanosomatids. Electron microscopy of kinetoplast DNA evidenced a network with organization similar to other trypanosomatids and the measurement of minicircles confirmed the size of about 1.45 kb of the sequenced minicircle.     

Gall aphids do not select optimal galling sites (Smynthurodes betae; Pemphigidae)

Abstract. 1. In studies of insect-host plant interaction it is often suggested that insects preferentially colonize host plants (or sites within plants) on which their fitness is maximized (a positive covariance of preference and performance). This suggestion stems from the assumption that natural selection has driven the system toward optimal use of resources.
2. Our study of the galling aphid Smynthurodes betae Westw. demonstrates that the distribution of galls on leaves is not due to preference, and can be altered by manipulating the aphid arrival time or the shoot growth rate.
3. We found no correlation between gall density and performance (aphid clone size) at different positions along the shoot.
4. Because leaves on the growing shoot are not equally responsive to aphid stimulation, the colonizers have no choice but to settle on leaves that are at the right stage when they arrive.
5. S.betae colonizers did not discriminate between shoots of their host and a congeneric non-host, on which their fitness is invariably zero.
6. Synchronization between galler and host plant phenologies seems to be the key to the observed distribution of galls on the tree. The data give no support to the preference-performance hypothesis.     

A STUDY OF TEXTURE-FLAVOR INTERACTIONS USING FREE-CHOICE PROFILING

Interactions between perceptions of texture and volatile flavors were assessed by free-choice profiling using gelatin desserts as a model product. Gels were prepared with all combinations of 2 levels of gelatin, and 2 concentrations of 2 different flavors. A trained sensory panel profiled each sample for aroma, flavor, and oral and manual texture. Generalized Procrustes Analysis was carried out separately for each sensory modality. The results indicate that while gelatin concentration and flavor type both modified perception of flavor, flavor concentration did not. Gelatin content influenced instrumental, oral, and manual evaluations of texture; however, the type and level of flavoring had little influence on oral perception of texture.     

A comparison of digestive efficiency in birds of prey

Differences in how raptors hunt and what they catch are correlated with size-independent differences in length of the small intestine, the region of the digestive tract responsible for food absorption. The study examined the functional significance of these differences among ten raptor species. Dry matter apparent digestive efficiency was calculated for each species fed a diet of day-old cockerels. For Falconiformes and Strigiformes, efficiencies varied between 75% and 82%, digestive efficiency being positively correlated with intestine length.
Generalist species, with a wide prey spectrum and feeding on relatively easily caught prey and carrion, had long intestines and high digestive efficiencies. Raptors specializing on fast-moving, avian prey had short intestines and reduced digestive efficiency. The Peregrine Falco peregrinus and the Common Buzzard Buteo buteo were used as examples of specialist and generalist feeders, respectively. Rabbit and pigeon were fed to both. Buzzards digested both diets more efficiently than Peregrines. Body-mass changes were used to examine the nutritional value of the two diets to each species. Buzzards gained body-mass when eating rabbit, Peregrines lost mass. Both species gained mass when feeding on pigeon. It seems that consideration of diet quality, not just quantity, is essential in understanding raptor food requirements. Generalist raptors have high efficiencies on several diets, specialists compensate for their reduced efficiency by eating food of high nutritional quality. Various aspects of prey quality are examined.