Flight Studies on Photic Communication by the Firefly Photinus pyralis

Flash communication by the firefly Photinus pyralis was studiedin a stationary, simulated flight apparatus in which an individualof either sex could be "flown" and its flashing behavior andflight orientation recorded in response to photic stimulation.Males made long "flights" showing many of the characteristicsof their natural, female-seeking patrol flights. Males orientedtheir flight vectors towards light emitting diode (LED) flashesthat mimicked the responses of females to their patrol flashes.Females flew and responded to male-emulating LED flashes, makinga previously unknown early response followed by the typical2 sec delayed response characteristic of the dialoging perchedfemale, including abdominal aiming of the flash. Pairs consistingof males, in tethered flight, and females, perched, were runin an integrating sphere photometer, permitting the first determinationsof flash intensities of both sexes during courtship dialog.The implications of this work on thought about evolution ofphotic behavior in fireflies are considered.     

Pneumocystosis in wild small mammals from California

Cyst forms of the opportunistic fungal parasite Pneumocystis carinii were found in the lungs of 34% of the desert shrew, Notiosorex crawfordi (n = 59), 13% of the ornate shrew, Sorex ornatus (n = 55), 6% of the dusky-footed wood rat, Neotoma fuscipes (n = 16), 2.5% of the California meadow vole, Microtus californicus (n = 40), and 50% of the California pocket mouse, Chaetodipus californicus (n = 2) caught from southern California between February 1998 and February 2000. Cysts were not found in any of the harvest mouse, Reithrodontomys megalotis (n = 21), California mouse, Peromyscus californicus (n = 20), brush mouse, Peromyscus boylii (n = 7) or deer mouse, Peromyscus maniculatus (n = 4) examined. All infections were mild; extrapulmonary infections were not observed. Other lung parasites detected were Hepatozoon sp./spp. from M. californicus and Notiosorex crawfordi, Chrysosporium sp. (Emmonsia) from M. californicus, and a nematode from S. ornatus.     

Mechanisms of dispersed central-place foraging in polydomous colonies of the Argentine ant

Many species of ants occupy multiple nests, a condition known as polydomy. Because of their decentralized structure, polydomous colonies may be removed from some of the constraints associated with classic central-place foraging. We used laboratory and field experiments to assess the mechanisms involved in dispersed central-place foraging in polydomous colonies of the Argentine ant Linepithema humile, a widespread invasive species. Both in the laboratory and in the field, Argentine ants established new nests at sites located near food. Laboratory colonies of L. humile redistributed workers, brood and resources among nests in response to the spatial heterogeneity of food resources. In addition, laboratory colonies formed recruitment trails between nests in the context of foraging, providing a mechanism for the transport of material between nests. This highly flexible system of allocating nests, workers and brood throughout a colony's foraging area potentially increases foraging efficiency and competitive ability. The importance of polydomy as a determinant of competitive ability is underscored by its prevalence among ecologically dominant ants, including most, if not all, highly invasive species. Copyright 2000 The Association for the Study of Animal Behaviour.     

Effect of Interspecific Competition and Herbivory on the Recruitment of an Invasive Alien Plant: Conyza sumatrensis

Most studies on the spread of a species have been carried out retrospectively. Conyza sumatrensis provides an exception; it has only been in Great Britain since 1984 and thereby provides the opportunity to follow an invasion from its early stages. Many different factors could lead to the exclusion of invading species from new habitats. Here we report results of a field experiment to determine the recruitment ability and population dynamics of C. sumatrensis within treatments of different levels of interspecific competition and herbivory over three years. Interspecific competition was manipulated using three cultivation treatments giving low, medium and high intensity competition. Factorial combinations of mollusc, insect and vertebrate (rabbit) herbivory were achieved using both chemical and physical exclusion techniques. We show that although C. sumatrensis recruitment occurs in areas where disturbance has caused low interspecific competition, maintenance of a population during secondary succession is unlikely. Effects of herbivory were dependent on the type of herbivory and the plant stage grazed. Rabbit grazing had strong negative effects on recruitment and survival of C. sumatrensis throughout the experiment. Insect herbivory, however, had no effect on any life stage. Mollusc herbivory showed a significant interaction with interspecific competitors, reducing recruitment only where competition was experimentally reduced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Disassembly and reassembly in vitro of complexes of secretory proteins from Chironomus tentans salivary glands

The secretory proteins of Chironomus tentans larvae form insoluble fibers that are spun into threads used to construct underwater feeding and pupation tubes. We began in vitro studies of the mechanism of assembly into fibers, the structure of the assembled proteins, and the contribution of individual proteins to the assembled structure. From measurements of turbidity and electron micrographs, we observed that the secretory proteins were isolated as complexes. These complexes are most likely at initial stages of assembly; further assembly into insoluble fibers must occur in vivo. Denaturation and reduction disrupted the complexes, and removal of the denaturing and reducing agents resulted in reassembly of the complexes. The circular dichroic spectrum of the complexes indicated that the assembled proteins had the tertiary structure alpha + beta. The largest secretory proteins were purified and shown to have both similar morphology, using electron microscopy, and a similar dichroic spectrum to that of the native complexes. We concluded that the large secretory proteins form the fibrous backbone of the complexes that we observe.     

Über Musterbildung in der Rhizodermis und Exodermis bei einigen Angiospermen und einer Polypodiacee

Ohne Zusammenfassung     

Effect of Arginine-deficient Media on the Herpes-Type Virus Associated with Cultured Burkitt Tumor Cells

After incubation at 37 C for 2 or more days, Basal Medium Eagle (BME) supplemented with 25% fetal calf serum (FCS) was not able to support adequate growth of EB3 and other lines of Burkitt tumor cells. The medium did, however, increase, by a factor of about 10, the number of cells synthesizing herpes-type virus with which the cultures were persistently infected. Not every lot of FCS produced these effects, nor were these effects seen when BME and FCS were incubated separately for 7 days before the medium was completed. At 37 C, appropriate lots of FCS interacted with several of the amino acids present in BME; this interaction resulted in an inhibition of cellular growth, whereas interaction with arginine yielded the virus-enhancing effect. Arginine-free BME, supplemented with 25% FCS and used without prior incubation, prevented cellular replication and promoted viral infection to a similar extent as did preincubated complete medium. Replenishment of arginine reduced, but did not regularly abolish, the virus-enhancing activity of preincubated media. RPMI-1629 medium was less affected by preincubation with FCS because it contained twice the amount of arginine that BME contained. The FCS factors which act upon arginine and other amino acids are not dialyzable and are partially resistant to heating at 56 or 60 C for 30 to 60 min. Calf and horse sera appear to be devoid of these activities. The nature of these interactions, as well as the mechanism by which arginine deficiency enhanced the viral infection, remains to be ascertained.