Seed Dispersal by Geochelone carbonaria and Geochelone denticulata in Northwestern Brazil1

The role of red‐footed tortoises (Geochelone carbonaria) and yellow‐footed tortoises (G. denticulata) as seed dispersal agents was investigated in northwestern Brazil from 5 to 26 January 2002 by analyzing fecal samples for frequency and viability of seed species and estimating daily displacement of tortoises from recaptured and thread‐trailed individuals. Fourteen of 19 fecal samples contained a total of 646 seeds represented by 11 plant species. The most abundant species was Ficus sp. (N= 400) with 100 percent of seeds viable, followed by Aechmea sp. (N = 88) with 93 percent of seeds viable, and Genipa americana (N= 59) with 91 percent of seeds viable. Mean minimum retention time of seeds was 1.6 d and mean daily displacement of tortoises based on recaptured (N= 7) and thread‐trailed tortoises (N= 2) was 57 m. Thus, the diversity and proportion of viable seeds consumed by tortoises, combined with the seed retention times and daily movements, suggest they may be effective dispersal agents. These preliminary findings warrant further investigation into the ecological role of these tortoises in Neotropical ecosystems and their contribution to the maintenance of species diversity and forest structure.     

Matrix gamma-carboxyglutamic acid protein (MGP) G-7A and T-138C gene polymorphisms in Indian (Mayo and Teenek) and Mestizo populations from Mexico

Matrix gamma-carboxyglutamic acid protein (MGP) genotypes (G-7A and T-138C) were determined in 266 individuals from three Mexican populations. Mexicans showed increased frequencies of the G-7A G allele and the G7-A GG genotype compared to Europeans. For the T-138C genotype, we found differences among the Mexicans. This study could help to define the significance of MGP polymorphisms as genetic markers in Amerindian populations.     

Invasion of exotic earthworms into ecosystems inhabited by native earthworms

The most conspicuous biological invasions in terrestrial ecosystems have been by exotic plants, insects and vertebrates. Invasions by exotic earthworms, although not as well studied, may be increasing with global commerce in agriculture, waste management and bioremediation. A number of cases has documented where invasive earthworms have caused significant changes in soil profiles, nutrient and organic matter dynamics, other soil organisms or plant communities. Most of these cases are in areas that have been disturbed (e.g., agricultural systems) or were previously devoid of earthworms (e.g., north of Pleistocene glacial margins). It is not clear that such effects are common in ecosystems inhabited by native earthworms, especially where soils are undisturbed. We explore the idea that indigenous earthworm fauna and/or characteristics of their native habitats may resist invasion by exotic earthworms and thereby reduce the impact of exotic species on soil processes. We review data and case studies from temperate and tropical regions to test this idea. Specifically, we address the following questions: Is disturbance a prerequisite to invasion by exotic earthworms? What are the mechanisms by which exotic earthworms may succeed or fail to invade habitats occupied by native earthworms? Potential mechanisms could include (1) intensity of propagule pressure (how frequently and at what densities have exotic species been introduced and has there been adequate time for proliferation?); (2) degree of habitat matching (once introduced, are exotic species faced with unsuitable habitat conditions, unavailable resources, or unsuited feeding strategies?); and (3) degree of biotic resistance (after introduction into an otherwise suitable habitat, are exotic species exposed to biological barriers such as predation or parasitism, “unfamiliar” microflora, or competition by resident native species?). Once established, do exotic species co-exist with native species, or are the natives eventually excluded? Do exotic species impact soil processes differently in the presence or absence of native species? We conclude that (1) exotic earthworms do invade ecosystems inhabited by indigenous earthworms, even in the absence of obvious disturbance; (2) competitive exclusion of native earthworms by exotic earthworms is not easily demonstrated and, in fact, co-existence of native and exotic species appears to be common, even if transient; and (3) resistance to exotic earthworm invasions, if it occurs, may be more a function of physical and chemical characteristics of a habitat than of biological interactions between native and exotic earthworms.     

Protective immunity against Taenia crassiceps murine cysticercosis induced by DNA vaccination with a Taenia saginata tegument antigen

This study investigated the protective capacity of the recombinant Taenia saginata Tso18 antigen administered as a DNA vaccine in the Taenia crassiceps murine model of cysticercosis. This Tso18 DNA sequence, isolated from a T. saginata oncosphere cDNA library, has homologies with Taenia solium and Echinococcus sp. It was cloned in the pcDNA3.1 plasmid and injected once intramuscularly into mice. Compared to saline-vaccinated control mice, immunization reduced the parasite burden by 57.3-81.4%, while lower levels of non-specific protection were induced in control mice injected with the plasmid pcDNA3.1 (18.8-33.1%) or a plasmid with irrelevant construct, pcDNA3.1/3D15 (33.4-38.8%). Importantly, significant levels of protection were observed between the pcDNA3.1/Tso18 plasmid and pcDNA3.1/3D15 plasmid immunized mice. Mice immunized with pTso18 synthesized low levels of, primarily IgG1 sub-class, antibodies. These antibodies were shown to recognize a 66 kDa antigen fraction of T. crassiceps and T. solium. Splenocytes enriched in both CD4+CD8- and CD4-CD8+ T cells from these vaccinated mice proliferated in vitro when exposed to antigens from both T. solium and T. crassiceps cestodes. Immunolocalization studies revealed the Tso18 antigen in oncospheres of T. saginata and T. solium, in the adult tapeworm and in the tegument of T. solium cysticerci. The protective capacity of this antigen and its extensive distribution in different stages, species and genera of cestodes points to the potential of Tso18 antigen for the possible design of a vaccine against cestodes.     

Cutting Edge: A Novel Mechanism Bridging Innate and Adaptive Immunity: IL-12 Induction of CD25 To Form High-Affinity IL-2 Receptors on NK Cells

NK cell expression and use of the IL-2Rα-chain (CD25), required for the high-affinity IL-2R, remain poorly understood. The studies reported in this article demonstrate that infections with murine CMV (MCMV), but not with lymphocytic choriomeningitis virus, induce CD25 on NK cells, along with high levels of IL-12 and IL-18. The cytokines act ex vivo to increase CD25 levels, and IL-12, IL-12R, and STAT4, but not the NK activating receptor Ly49H, are required for peak induction in vivo. All examined NK cell populations are driven into proliferation and incorporate BrdU in response to high ex vivo concentrations of IL-2, but only those from MCMV infection respond to low ex vivo concentrations of IL-2. The numbers of NK cells elicited during MCMV infection are reduced by IL-2 neutralization. Thus, a link between innate and adaptive immunity is established by which composition of innate cytokine responses sets up to promote NK cell use of a factor supporting adaptive responses.     

Modulation of social interactions by immune stimulation in honey bee, <Emphasis Type="Italic">Apis mellifera</Emphasis>, workers

Background  

Immune response pathways have been relatively well-conserved across animal species, with similar systems in both mammals and invertebrates. Interestingly, honey bees have substantially reduced numbers of genes associated with immune function compared with solitary insect species. However, social species such as honey bees provide an excellent environment for pathogen or parasite transmission with controlled environmental conditions in the hive, high population densities, and frequent interactions. This suggests that honey bees may have developed complementary mechanisms, such as behavioral modifications, to deal with disease.     

Flying lemurs – The 'flying tree shrews'? Molecular cytogenetic evidence for a Scandentia-Dermoptera sister clade

Background  

Flying lemurs or Colugos (order Dermoptera) represent an ancient mammalian lineage that contains only two extant species. Although molecular evidence strongly supports that the orders Dermoptera, Scandentia, Lagomorpha, Rodentia and Primates form a superordinal clade called Supraprimates (or Euarchontoglires), the phylogenetic placement of Dermoptera within Supraprimates remains ambiguous.