Social interactions of juvenile Collared peccaries, Tayassu tajacu (Mammalia: Artiodactyla)

Is there a predictable relationship between species-typical behavioural development and social organization in mammals? Earlier work on canids and rodents suggested that adult sociality is associated with a developmental schedule in which juveniles showed, among themselves: (1) frequent social play; (2) frequent amicable contact; (3) frequent olfactory contact; (4) a delay in the emergence of agonistic behaviour. In the highly social Collared peccary (Tayassu tajacu) the behaviour of juveniles conformed only partially to this scheme. Juveniles engaged in social play with each other at an early age, but showed no other observable amicable or olfactory contact until eight to twelve weeks of age and showed no delay in the emergence of agonistic behaviour among themselves. Adults, in contrast, were conspicuously tolerant of juveniles, and 86% of juvenile social interactions in the first year took place with adults.     

Multiple functions for NGF receptor in developing, aging and injured rat teeth are suggested by epithelial, mesenchymal and neural immunoreactivity

We have used immunocytochemistry to analyse expression of nerve growth factor receptor (NGFR) in developing, aging and injured molar teeth of rats. The patterns of NGFR immunoreactivity (IR) in developing epithelia and mesenchyme matched the location of NGFR mRNA assayed by in situ hybridization with a complementary S35-labeled RNA probe. The following categories of NGFR expression were found. (1) There was NGFR-IR in the dental lamina epithelium and in adjacent mesenchyme during early stages of third molar formation. (2) NGFR-IR nerve fibers were posterior and close to the bud epithelium. (3) During crown morphogenesis NGFR expression was prominent in internal enamel epithelium and preodontoblasts; it faded as preameloblasts elongated and as odontoblasts began to make predentin matrix; and it was weak or absent from outer enamel epithelium, the cervical loop, and differentiated ameloblasts and odontoblasts. (4) When NGFR-IR nerve fibers entered the molars late in the bell stage, they innervated the most mature peripheral pulp and dentin in an asymmetric pattern which correlated more with asymmetric enamel synthesis than with mesenchymal NGFR-IR distribution. (5) The mesenchymal pulp cells continued to have intense NGFR expression in adult teeth, especially near coronal tubular dentin. (6) The pulpal NGFR-IR decreased in very old rats or subjacent to reparative dentin (naturally occurring or experimentally induced). (7) During root formation, the preodontoblasts had NGFR-IR but most root mesenchymal cells and Hertwig's epithelial root sheath did not. This work suggests that there are important epithelial and mesenchymal targets of NGF regulation during molar morphogenesis that differ for crown and root development and that do not correlate with neural development. The continuing expression of NGFR-IR by pulpal mesenchymal cells in adult rats was most intense near coronal odontoblasts making tubular dentin; and it was lost during aging, or subjacent to sites of dentin injury that caused a phenotypic change in the odontoblast layer.     

Complete amino acid sequence of human cartilage link protein (CRTL1) deduced from cDNA clones and chromosomal assignment of the gene

Little is known about the primary amino acid structure of human cartilage link protein (CRTL1). We screened a human genomic library with a cDNA encoding the 3' untranslated region and the adjoining B1 domain of chicken link protein. One clone was isolated and characterized. A 3.5-kb EcoRI-KpnI fragment from this genomic clone that contains the human B1 exon was used to map the gene to chromosome 5q13----q14.1. The same fragment was used to screen a cDNA library prepared from mRNA of Caco-2, a human colon tumor cell line. Two overlapping clones were isolated and shown to encode all of CRTL1. The deduced amino acid sequence is 354 residues long. The amino acid sequence shows a striking degree of identity to the porcine (96%), rat (96%), and chicken (85%) link protein sequences. Furthermore, there is greater than 86% homology between the 3' untranslated region of the genes encoding human and porcine link proteins. These results indicate that there has been strong evolutionary pressure against changes in the coding and 3' untranslated regions of the gene encoding cartilage link protein.     

A major locus controls a biologically active pheromone component in Heliconius melpomene

Understanding the production, response, and genetics of signals used in mate choice can inform our understanding of the evolution of both intraspecific mate choice and reproductive isolation. Sex pheromones are important for courtship and mate choice in many insects, but we know relatively little of their role in butterflies. The butterfly Heliconius melpomene uses a complex blend of wing androconial compounds during courtship. Electroantennography in H. melpomene and its close relative Heliconius cydno showed that responses to androconial extracts were not species specific. Females of both species responded equally strongly to extracts of both species, suggesting conservation of peripheral nervous system elements across the two species. Individual blend components provoked little to no response, with the exception of octadecanal, a major component of the H. melpomene blend. Supplementing octadecanal on the wings of octadecanal-rich H. melpomene males led to an increase in the time until mating, demonstrating the bioactivity of octadecanal in Heliconius. Using quantitative trait locus (QTL) mapping, we identified a single locus on chromosome 20 responsible for 41% of the parental species’ difference in octadecanal production. This QTL does not overlap with any of the major wing color or mate choice loci, nor does it overlap with known regions of elevated or reduced F_ST. A set of 16 candidate fatty acid biosynthesis genes lies underneath the QTL. Pheromones in Heliconius carry information relevant for mate choice and are under simple genetic control, suggesting they could be important during speciation.     

A hitchhiker’s guide to the Maritimes: anthropogenic transport facilitates long‐distance dispersal of an invasive marine crab to Newfoundland

Aim To determine timing, source and vector for the recent introduction of the European green crab, Carcinus maenas (Linnaeus, 1758), to Newfoundland using multiple lines of evidence. Location Founding populations in Placentia Bay, Newfoundland, Canada and potential source populations in the north‐west Atlantic (NWA) and Europe. Methods We analysed mitochondrial and microsatellite genetic data from European and NWA populations sampled during 1999–2002 to determine probable source locations and vectors for the Placentia Bay introduction discovered in 2007. We also analysed Placentia Bay demographic data and shipping records to look for congruent patterns with genetic analyses. Results Demographic data and surveys suggested that C. maenas populations are established and were in Placentia Bay for several years (c. 2002) prior to discovery. Genetic data corroboratively suggested central/western Scotian Shelf populations (e.g., Halifax) as the likely source area for the anthropogenic introduction. These Scotian Shelf populations were within an admixture zone made up of genotypes from both the earlier (early 1800s) and later (late 1900s) introductions of the crab to the NWA from Europe. Placentia Bay also exhibited this mixed ancestry. Probable introduction vectors included vessel traffic and shipping, especially vessels carrying ballast water. Main conclusions Carcinus maenas overcame considerable natural barriers (i.e., coastal and ocean currents) via anthropogenic transport to become established and abundant in Newfoundland. Our study thus demonstrates how non‐native populations can be important secondary sources of introduction especially when aided by human transport. Inference of source populations was possible owing to the existence of an admixture zone in central/western Nova Scotia made up of southern and northern genotypes corresponding with the crab’s two historical introductions. Coastal vessel traffic was found to be a likely vector for the crab’s spread to Newfoundland. Our study demonstrates that there is considerable risk for continued introduction or reintroduction of C. maenas throughout the NWA.     

As good as dead? Sublethal predation facilitates lethal predation on an intertidal clam

Although ecologists have speculated that sublethal predation can impact prey dynamics, consequences of these predator effects have seldom been experimentally tested. In soft‐sediment marine communities, fishes crop extended feeding siphons of buried clams, potentially causing clams to reduce their burial depth, thereby enhancing their susceptibility to excavating lethal predators. We simulated cropping of the confamilial clams, Protothaca staminea and Venerupis philippinarum, by removing the top 40% of siphons, which caused each species to burrow 33–50% shallower than conspecifics with intact siphons. To examine subsequent consequences of reduced burial depth, we exposed cropped and intact clams to natural levels of predation in the field. Because of a naturally longer siphon, Protothaca, even after cropping, remained at relatively safe burial depths. In contrast, siphon cropping nearly doubled the mortality rate of Venerupis. Thus, while sublethal predation facilitates lethal predation, this linkage depends on specific life history characteristics, even among ecologically similar species.     

Amonabactin, a novel tryptophan- or phenylalanine-containing phenolate siderophore in Aeromonas hydrophila.

Aeromonas hydrophila 495A2 excreted two forms of amonabactin, a new phenolate siderophore composed of 2,3-dihydroxybenzoic acid, lysine, glycine, and either tryptophan (amonabactin T) or phenylalanine (amonabactin P). Supplementing cultures with L-tryptophan (0.3 mM) caused exclusive synthesis of amonabactin T, whereas supplements of L-phenylalanine (0.3 to 30 mM) gave predominant production of amonabactin P. The two forms of amonabactin were separately purified by a combination of production and polyamide column chromatographic methods. Both forms were biologically active, stimulating growth in iron-deficient medium of an amonabactin-negative mutant. Of 43 additional siderophore-producing isolates of the Aeromonas species that were tested, 76% (19 of 25) of the A. hydrophila isolates were amonabactin positive, whereas only 19% (3 of 16) of the A. sobria isolates and all (3 of 3) of the A. caviae isolates produced amonabactin, suggesting a predominant synthesis of amonabactin in certain Aeromonas species.     

The role of cadherin,beta-catenin,and AP-1 in retinoid-regulated carcinoma cell differentiation and proliferation

Vitamin A derivatives (retinoids) are potent regulators of cell proliferation and differentiation. Retinoids inhibit the function of the oncogenic AP-1 and beta-catenin/TCF pathways and also stabilize components of the adherens junction, a tumor suppressor complex. When treated with retinoic acid (RA), the breast cancer cell line, SKBR3, undergoes differentiation and reduction in cell proliferation. The present work demonstrates that in SKBR3 cells, which exhibit high AP-1 activity, RA-regulation of cadherin expression and function, but not changes in AP-1 (or beta-catenin/TCF) signaling, is responsible for the epithelial differentiation. However, cadherin function and recruitment of beta-catenin to the membrane is not required for RA to regulate DNA synthesis in these cells. RA also reduces the activity of an AP-1 and TCF-sensitive cyclin D1 reporter in SKBR3 cells in a manner that is independent of the TCF site. In contrast, in SW480 cells, which have high levels of beta-catenin/TCF signaling, the activity and retinoid responsiveness of the cyclin D1 promoter was markedly inhibited by mutation of the TCF site. These data indicate that the remarkably broad effects of RA on the growth and differentiation of many different epithelial cancers may well be explained by the ability of RA to differentially regulate the activity of RAR/RXR, AP-1, and beta-catenin/TCF pathways.     

PCR-based assays for the fish pathogen Aeromonas salmonicida. I. Evaluation of three PCR primer sets for detection and identification

In an effort to develop a rapid diagnostic test for the fish pathogen Aeromonas salmonicida, the performance of 2 polymerase chain reaction (PCR) primer sets (AP and PAAS) targeting the fish pathogen A. salmonicida and 1 PCR primer set (MIY) targeting A. salmonicida subsp. salmonicida were evaluated. Initially, the PCR assays were used to screen purified DNA extracted from 308 A. salmonicida isolates. The AP and PAAS PCR tests were demonstrated to be 100% specific for the species A. salmonicida and did not cross-react with any of the non-target organisms (bacterial species other than A. salmonicida) used in this study. The combined sensitivity of the AP and PAAS tests was 99.4% and offered the best coverage in terms of identifying the target organism. The MIY PCR appeared to be 100% sensitive and specific for A. salmonicida subsp. salmonicida. Studies with tissues, spiked with known quantities of bacteria, were conducted to determine the lower detection limit of the PCR tests, and then the ability of these PCR tests to detect A. salmonicida in experimentally infected salmonids was assessed.