Carbon isotopes as indicators of elephant diets and African environments

Stable carbon isotope ratios have been successfully used to assess modern animal diets and to reconstruct prehistoric diets of animals and humans (Vogel & van der Merwe, 1977; van der Merwe & Vogel, 1978; Burleigh & Brothwell, 1978; Vogel, 1978a; DeNiro & Epstein, 1978; Tieszen et al., 1979; Tieszen & Imbamba, 1980; Chisholm, Nelson & Schwarcz, 1982; Tauber, 1981). We have used ¹³C/¹²C ratio measurements of bone collagen to study the diets of African elephants in twelve wildlife refuges. These represent most of the habitats in which elephants live, including such diverse plant communities as primary rain forest, savanna woodland and desert. The δ¹³C values were found to have a simple linear relationship with tree density in most cases. When translated into relative amounts of dietary browse (C₃ plants) and graze (C₄ plants), the grass content is seen to be systematically under-represented, presumably due to inefficient metabolism. This does not affect the relationship between elephant diet and tree density, which has implications for the study of elephant-woodland interactions, and for reconstructions of past African environments.     

Tumor Suppressor p53 Down-Regulates Tissue-Specific Expression of Tyrosinase Gene in Human Melanoma Cell Lines

Tyrosinase, the key gene in melanin pigment synthesis, is tissue-specifically expressed in melanocytic cells. Expression of this gene is regulated by various hormones, carcinogens, and environmental factors. The molecular basis underlying tyrosinase gene regulation is still not clear. In this report, we present the effects of tumor suppressor p53 protein on tyrosinase gene expression and melanin synthesis in human melanoma. After stable transfection of wild type p53 expression plasmid into a highly pigmented melanoma cell line, overexpression of wt p53 suppressed the pigmentation of the melanoma cells. The loss of pigmentation was associated with the loss of endogenous tyrosinase expression at the activity and mRNA levels. In order to determine whether the p53 repression of tyrosinase mRNA involved modulation of tyrosinase promoter activity, transient transfection approaches involving p53 expression plasmid and construct containing chloramphenicol acetyl transferase (CAT) reporter gene linked to 270 bp tissue-specific tyrosinase promoter have been used. p53 specifically repressed CAT gene expression from the tyrosinase promoter and not from the Rous sarcoma virus promoter. These data suggest that in human melanoma p53 down-regulates the tissue-specific expression of tyrosinase gene and subsequent melanin synthesis.     

Linking intronic polymorphism on the CHD1‐Z gene with fitness correlates in Black‐tailed Godwits Limosa l. limosa

We show that variation in an intronic length polymorphism in the CHD1‐Z gene in Black‐tailed Godwits Limosa l. limosa is associated with fitness correlates. This is the second example of the CHDZ‐1 gene being correlated with fitness, a previous study having established that Moorhens Gallinula chloropus carrying the rare Z* allele have reduced survival. In Godwits, however, carriers of the Z* allele (374 bp) fared better than those with the more frequent Z allele (378 bp) with respect to body mass, plumage ornamentation, reproductive parameters and habitat quality. The Z* allele was found in 14% of 251 adult birds from nature reserves, but was absent from 33 birds breeding in intensively managed agricultural lands. Males and females with the Z* allele had less extensive breeding plumage, and females had a higher body mass, bred earlier and had larger eggs. There were no significant differences in annual survival between birds with and without the Z* allele. DNA isolated from museum skins demonstrated that this polymorphism was present at low frequency in 1929. We speculate that strong asymmetrical overdominance may explain the low frequency of the Z* allele and that genetic linkage to causal genes might be an explanation for the phenotypic correlations. Our findings suggest a degree of cryptic genetic population structuring in the Dutch Godwit population.     

Genital primordium of the free-living marine nematode Halichoanolaimus sonorus (Chromadoria,Chromadorida)

Summary

The genital primordium of the first stage juvenile (J1) of the free-living marine nematode Halichoanolaimus sonorus (Chromadorida: Selachinematidae) was studied using transmission electron microscopy. The primordium consists of four undifferentiated cells: two primordial germ cells (PGC) 5–6 μm in diameter and two somatic cells. The PGC have a large nucleus with nucleolus. The centriole was detected in close vicinity of the PGC nucleus. Most of the cell mitochondria are in close contact with the nuclear envelope. The mitochondria are interspersed by 0.2–0.3 μm particles of an electron-dense diffuse substance devoid of surrounding membrane. Both PGC are closely attached to each other and to the neighboring somatic cells of the genital primordium. The elongated somatic cells contain nuclei devoid of nucleoli; the cytoplasm is filled with free ribosomes and contains occasional cisternae of rough endoplasmatic reticulum (RER), Golgi bodies, mitochondria, and transparent vesicles. The genital primordium is separated by a narrow space from of the intestine (dorsally) and the somatic muscles (ventrally). The PGC of H. sonorous are devoid of typical P granules known for previously studied nematodes as distinct markers of germ line cell lineage. Perinuclear particles of dense diffuse substance found in PGC of H. sonorous could be considered as germ determinants analogous to P granules.     

The Boar-Operated-System: a Novel Method to Deliver Baits to Wild Pigs

ABSTRACT Bait-delivered pharmaceuticals, increasingly used to manage populations of wild boar (Sus scrofa) and feral pigs, may be ingested by nontarget species. Species-specificity could be achieved through a delivery system. We designed the BOS^TM (Boar-Operated-System) as a device to deliver baits to wild pigs. The BOS^TM consists of a metal pole onto which a round perforated base is attached. A metal cone with a wide rim slides up and down the pole and fully encloses the base onto which the baits are placed. We conducted a pilot, captive trial and found that captive wild boar fed from the BOS^TM either directly, by lifting the cone, or indirectly, by feeding once another animal had lifted the cone. Thus, we tested whether free-living wild boar fed from the BOS^TM and whether the BOS^TM could prevent bait uptake by nontarget species. We observed that free-living wild boar fed regularly from the BOS^TM and that the device successfully prevented bait uptake by nontarget species. The BOS^TM should be trialed more extensively to confirm its effectiveness and species-specificity to distribute pharmaceuticals to wild suids. If successful, the BOS^TM could be used to deliver vaccines in disease control programs as well as contraceptives to manage overabundant populations of wild suids.     

Phylogeny of the parasitic wasp subfamily Euphorinae (Braconidae) and evolution of its host preferences

The braconid subfamily Euphorinae is a large, cosmopolitan group of endoparasitoid wasps. The majority of species attack adult hosts, a strategy that is rare among parasitic wasps, but there are also many species that attack nymphs and larval stages. Euphorine hosts may belong to a variety of insect orders (Coleoptera, Hemiptera, Hymenoptera, Neuroptera, Psocoptera, Orthoptera and Lepidoptera) although most euphorine tribes are confined to Coleoptera. Here we investigate the phylogenetic relationships of the Euphorinae based on molecular data (3 kb of nucleotide data from four markers: 18S, 28S, CAD and COI) and propose a higher‐level classification based upon the resulting phylogeny. We also infer the evolution of host associations and discuss the diversification of the Euphorinae. Results from both Bayesian inference and maximum‐likelihood analysis show that the subfamily, as previously circumscribed, is paraphyletic. We propose that the subfamily be expanded to include the tribes Meteorini and Planitorini (Mannokeraia + Planitorus), so that it corresponds to a clade that is strongly supported as monophyletic in our analyses. Based on our results, a revised higher classification of the Euphorinae is proposed, in which 52 extant genera and 14 tribes are recognized. We reinstate the genus Microctonus belonging to the tribe Perilitini, and synonymize Ussuraridelus with Holdawayella, Sinuatophorus with Eucosmophorus. Furthermore, we propose the following tribal rearrangements: Spathicopis and Stenothremma are transferred to Perilitini; Tuberidelus, Eucosmophorus and Plynops to Cosmophorini; Ecclitura to Dinocampini; Chrysopophthorus, Holdawayella and Wesmaelia to Helorimorphini; Proclithroporus and Heia to Townesilitini. The monotypic tribe Cryptoxilonini is synonymized with Cosmophorini. The genera Pygostolus and Litostolus are placed in a separate tribe, Pygostolini, previously recognized as a subtribe among the Centistini. Parsimony‐based ancestral state reconstructions suggest that the ancestor of Euphorinae was a parasitoid of lepidopteran larvae, and that a host shift to larval Coleoptera occurred only in one clade of the Meteorini, some members of which secondarily shifted back to larval lepidopteran hosts. In the remainder of the subfamily, there was an initial shift from larval to adult coleopterans, followed by subsequent shifts to adults or larvae of Hemiptera, Hymenoptera, Neuroptera, Orthoptera and Psocoptera.     

Phosphorus recycling in photorespiration maintains high photosynthetic capacity in woody species

Leaf photosynthetic CO₂ responses can provide insight into how major nutrients, such as phosphorus (P), constrain leaf CO₂ assimilation rates (A_net). However, triose‐phosphate limitations are rarely employed in the classic photosynthesis model and it is uncertain as to what extent these limitations occur in field situations. In contrast to predictions from biochemical theory of photosynthesis, we found consistent evidence in the field of lower A_net in high [CO₂] and low [O₂] than at ambient [O₂]. For 10 species of trees and shrubs across a range of soil P availability in Australia, none of them showed a positive response of A_net at saturating [CO₂] (i.e. A_max) to 2 kPa O₂. Three species showed >20% reductions in A_max in low [O₂], a phenomenon potentially explained by orthophosphate (P_i) savings during photorespiration. These species, with largest photosynthetic capacity and P_i > 2 mmol P m^?2, rely the most on additional P_i made available from photorespiration rather than species growing in P‐impoverished soils. The results suggest that rarely used adjustments to a biochemical photosynthesis model are useful for predicting A_max and give insight into the biochemical limitations of photosynthesis rates at a range of leaf P concentrations. Phosphate limitations to photosynthetic capacity are likely more common in the field than previously considered.     

Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia)

Abstract: The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel‐fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.