The effect of serotonin and octopamine on the optokinetic response of the crab Leptograpsus variegatus

A standard optokinetic response of the ipsilateral and contralateral (driven) eyes of the crab Leptograpsus variegatus to a sinusoidally oscillating striped drum was established. Optokinetic responses were then measured of animals that had been treated by introducing serotonin and octopamine into the blood stream via the heart and also into the neural tissue of the optic lobes via a micropipette. Both serotonin and octopamine enhance the optokinetic effect when applied in low doses. Experiments show that serotonin is most likely acting closer to the sensory input in the optokinetic system.     

Lectin binding to cystic stages of Taenia taeniaeformis

Studies of membrane glycoconjugates of Taenia taeniaeformis were initiated by assays of the lectin binding characteristics of 35-day-old cysticerci. Parasites fixed in glutaraldehyde were incubated with one of the following FITC-labelled lectins: Concanavalin A (Con A), Lens culinaris agglutinin (LCA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA), fucose binding protein (FBP) and wheat germ agglutinin (WGA) and either their specific or a nonspecific sugar. Ultraviolet microscopy revealed that only Con A and LCA bound in large amounts to the surface of cysticerci. This binding was partly inhibited by the specific sugar, but the nonspecific sugar had little effect. The lectin not removed by either of the sugars may have been bound nonspecifically to the charged glycocalyx. Lectins were primarily bound on the anterior third of the parasite around the scolex invagination. Kinetic studies of lectin interactions were carried out with LCA and RCA by spectrophotofluorometric analysis of the amount bound specifically or nonspecifically over a range of lectin concentrations. Lens culinaris lectin binding was found to be specific and involve 2 receptors which showed large differences in their affinity for lectin and prevalence on the surface. Ricinus communis lectin did not bind specifically but nonspecific interactions were observed. Adherence of small numbers of host cells was shown to have no measurable effect on the lectin binding characteristics. The results suggest that the major surface carbohydrates exposed are D-mannose and/or D-glucose residues with the other sugar groups poorly represented. This relatively homogeneous surface may have implications for the antigenicity of the parasite in its host.     

The detection of real and apparent motion by the crabLeptograpsus variegatus

Summary Optokinetic eye movements can be evoked in rock crabs either by real or apparent motion of the visual field. For wide-field striped stimuli, the apparent motion stimulus is less effective than the real motion but for narrow field light-spot stimuli, intensity is an important factor: at low light intensities real motion is still a more effective stimulus but at high light intensities the opposite is true. The crab's complex response to apparent motion appears to be dominated by the combination of two central mechanisms, one of which decays exponentially during the Dark period, and one which becomes resensitized, after a short delay, in the dark.Supported by the Deutsche Forschungsgemeinschaft ER 79/1     

Brain architecture of the largest living land arthropod, the Giant Robber Crab Birgus latro (Crustacea, Anomura, Coenobitidae): evidence for a prominent central olfactory pathway?

Background

Several lineages within the Crustacea conquered land independently during evolution, thereby requiring physiological adaptations for a semi-terrestrial or even a fully terrestrial lifestyle. Birgus latro Linnaeus, 1767, the giant robber crab or coconut crab (Anomura, Coenobitidae), is the largest land-living arthropod and inhabits Indo-Pacific islands such as Christmas Island. B. latro has served as a model in numerous studies of physiological aspects related to the conquest of land by crustaceans. From an olfactory point of view, a transition from sea to land means that molecules need to be detected in gas phase instead of in water solution. Previous studies have provided physiological evidence that terrestrial hermit crabs (Coenobitidae) such as B. latro have a sensitive and well differentiated sense of smell. Here we analyze the brain, in particular the olfactory processing areas of B. latro, by morphological analysis followed by 3 D reconstruction and immunocytochemical studies of synaptic proteins and a neuropeptide.

Results

The primary and secondary olfactory centers dominate the brain of B. latro and together account for ca. 40% of the neuropil volume in its brain. The paired olfactory neuropils are tripartite and composed of more than 1,000 columnar olfactory glomeruli, which are radially arranged around the periphery of the olfactory neuropils. The glomeruli are innervated ca. 90,000 local interneurons and ca. 160,000 projection neurons per side. The secondary olfactory centers, the paired hemiellipsoid neuropils, are targeted by the axons of these olfactory projection neurons. The projection neuron axonal branches make contact to ca. 250.000 interneurons (per side) associated with the hemiellipsoid neuropils. The hemiellipsoid body neuropil is organized into parallel neuropil lamellae, a design that is quite unusual for decapod crustaceans. The architecture of the optic neuropils and areas associated with antenna two suggest that B. latro has visual and mechanosensory skills that are comparable to those of marine Crustacea.

Conclusions

In parallel to previous behavioral findings that B. latro has aerial olfaction, our results indicate that their central olfactory pathway is indeed most prominent. Similar findings from the closely related terrestrial hermit crab Coenobita clypeatus suggest that in Coenobitidae, olfaction is a major sensory modality processed by the brain, and that for these animals, exploring the olfactory landscape is vital for survival in their terrestrial habitat. Future studies on terrestrial members of other crustacean taxa such as Isopoda, Amphipoda, Astacida, and Brachyura will shed light on how frequently the establishment of an aerial sense of olfaction evolved in Crustacea during the transition from sea to land. Amounting to ca. 1,000,000, the numbers of interneurons that analyse the olfactory input in B. latro brains surpasses that in other terrestrial arthropods, as e.g. the honeybee Apis mellifera or the moth Manduca sexta, by two orders of magnitude suggesting that B. latro in fact is a land-living arthropod that has devoted a substantial amount of nervous tissue to the sense of smell.     

Recruitment of honeybees to non-scented food sources

Small groups of honeybees (five to nine individuals) were trained to forage at feeders 150 m, 300 m and 800 m from an observation hive. Their behaviour in the hive and at the feeder was recorded by observers that maintained continuous radio contact with one another. At low concentrations of sugar in the feeder (0.5 mol x l(-1)) foragers do not dance in the hives, their flights to the feeder are often undertaken alone, they land immediately after arrival at the site and no recruits from the hive landed on the feeder during 30 h of observation. Raising the concentration of sugar in the feeder to 2 mol x l(-1) leads to vigorous dancing by the foragers and the gradual (over 10-15 min) synchronisation of their flights so that they arrive in groups of up to five bees at the feeder and undertake circular "buzzing" flights before landing. Such behaviour of the foragers is associated with the appearance of recruits which were never seen to fly around the feeder and land alone or before the foragers. Recruits typically circle the feeder together with foragers and land with them or continue their circling flights to land about 10 s later. While circling the feeder recruits, but not foragers, will fly after a moving lure if the presentation of the lure is accompanied by the release of geraniol scent. We propose that recruits that have witnessed a waggle dance are unlikely to find a non-scented feeder unless the foragers continue their flights to that feeder and provide supplementary visual and/or olfactory cues, at least in the vicinity of the feeder. We propose that the synchronisation of the flights of foragers and their behaviour at the feeding site is a strategy designed to overcome a navigational gap in the recruiting process in which the dance can indicate the general area of a food source but not the precise position of a highly localised site.     

In vivo and in vitro studies of the effects of immune rat serum on Fasciola hepatica

Significant protection against infection with 10 or 30 metacercariae of Fasciola hepatica was conferred on naive rats by the passive transfer of serum derived from rats which had been exposed to primary and challenge infections with 5 or 10 and 30 or 20 metacercariae respectively. Immune serum did not have a pronounced effect on the mortality of metacercariae in vitro. However, its presence was associated with the formation of a precipitate on the tegument of each metacercaria and in the culture medium. The precipitate contained rat antibody and other components, presumably parasite antigens, which elicited the formation of antibody when the precipitate was injected into rats. Viability of metacercariae cultured in immune and normal sera as well as freshly excysted specimens was tested in rats by intraperitoneal infection. Metacercariae cultured in immune serum did not develop. By comparison with the viability of freshly excysted metacercariae, that of some metacercariae cultured in normal serum was impaired; this was attributed to inadequacies in the culture technique. A relationship between precipitate formation in vitro and impaired viability of metacercariae in vivo has yet to be established.     

Parasites, parasitology and parasitologists

The science of parasitology is one of the many new disciplines of the twentieth century, as such it is a dynamic and rapidly evolving science which encompasses an increasing number of sub-disciplines and technologies. However, will the fragmentation involved in current methods of scientific enquiry and the competition for funding mean the decline of certain areas of parasitology or perhaps the complete loss of the discipline. This paper attempts to address these questions by considering the development of the discipline of parasitology especially within Australia and by considering the mechanisms of attaining funding for science. Technological change and its impact on parasitology is also considered, and requirements for maintenance of the discipline and its practitioners are suggested.     

The cytokine and chemokine expression profile of nucleus pulposus cells: implications for degeneration and regeneration of the intervertebral disc

Introduction

The aims of these studies were to identify the cytokine and chemokine expression profile of nucleus pulposus (NP) cells and to determine the relationships between NP cell cytokine and chemokine production and the characteristic tissue changes seen during intervertebral disc (IVD) degeneration.

Methods

Real-time q-PCR cDNA Low Density Array (LDA) was used to investigate the expression of 91 cytokine and chemokine associated genes in NP cells from degenerate human IVDs. Further real-time q-PCR was used to investigate 30 selected cytokine and chemokine associated genes in NP cells from non-degenerate and degenerate IVDs and those from IVDs with immune cell infiltrates (‘infiltrated’). Immunohistochemistry (IHC) was performed for four selected cytokines and chemokines to confirm and localize protein expression in human NP tissue samples.

Results

LDA identified the expression of numerous cytokine and chemokine associated genes including 15 novel cytokines and chemokines. Further q-PCR gene expression studies identified differential expression patterns in NP cells derived from non-degenerate, degenerate and infiltrated IVDs. IHC confirmed NP cells as a source of IL-16, CCL2, CCL7 and CXCL8 and that protein expression of CCL2, CCL7 and CXCL8 increases concordant with histological degenerative tissue changes.

Conclusions

Our data indicates that NP cells are a source of cytokines and chemokines within the IVD and that these expression patterns are altered in IVD pathology. These findings may be important for the correct assessment of the ‘degenerate niche’ prior to autologous or allogeneic cell transplantation for biological therapy of the degenerate IVD.