Re-evaluation of Hymenostylium xanthocarpum (Hook.) Brid., and Ardeuma R.H.Zander & Hedd., a new name for all other species of Hymenostylium (Pottiaceae,Bryophyta)

The Old World Hymenostylium xanthocarpum, the generitype of Hymenostylium, was found to be unrelated to the widespread H. recurvirostrum and other species currently placed in the genus. Major distinguishing traits of H. xanthocarpum are the presence of a stem central strand, leaves broadest about midleaf and constricted just above the base, distal laminal cells usually ventrally bulging and massively unipapillose, and basal cells differentiated only in the lower 1/5–1/7 of the leaf. A new genus name, Ardeuma, is proposed for the remaining species of Hymenostylium, and combinations are made for those that are commonly recognized. A key to Tuerckheimia species in the New World that may be confused with H. xanthocarpum is provided.     

An intertidal balanomorph Hexaminius venerai sp. nov. (Austrobalanidae) colonizing a log of Podocarpoxylon from the La Meseta Formation (Eocene), Seymour Island,Antarctica: a glimpse of Antarctic antiquity

Abstract

The sessile barnacle Hexaminius venerai sp. nov. (Tetraclitoidea: Austrobalanidae) is described from the middle Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula. Hexaminius venerai sp. nov. is the earliest known record of the genus in the Antarctic, the first occurrence of Hexaminius from outside Australian waters and the first record of a fossil cirripede attached to the substrate from the Antarctic. Exceptional preservation of more than 200 specimens, some of which retain opercula within the shell, is discussed. In life, the cirripedes were attached to a tree trunk tentatively identified as Podocarpoxylon, a South Hemisphere conifer. Hexaminius venerai sp. nov. is a survivor of an early phase in balanid radiation, prior to the development of strong radially-interlocked parietes.https://zoobank.org/urn:lsid:zoobank.org:pub:EAA2EB5C-BC57-41FA-93A0-046AF5FD59EB     

Natural variation in chemosensation: lessons from an island nematode

All organisms must interact with their environment, responding in behavioral, chemical, and other ways to various stimuli throughout their life cycles. Characterizing traits that directly represent an organism's ability to sense and react to their environment provides useful insight into the evolution of life‐history strategies. One such trait for the nematode Pristionchus pacificus, chemosensation, is involved in navigation to beetle hosts. Essential for the survival of the nematode, chemosensory behavior may be subject to variation as nematodes discriminate among chemical cues to complete their life cycle. We examine this hypothesis using natural isolates of P. pacificus from La Réunion Island. We select strains from a variety of La Réunion beetle hosts and geographic locations and examine their chemoattraction response toward organic compounds, beetle washes, and live beetles. We find that nematodes show significant differences in their response to various chemicals and are able to chemotax to live beetles in a novel assay. Further, strains can discriminate among different cues, showing more similar responses toward beetle washes than to organic compounds in cluster analyses. However, we find that variance in chemoattraction response is not significantly associated with temperature, location, or beetle host. Rather, strains show a more concerted response toward compounds they most likely directly encounter in the wild. We suggest that divergence in odor‐guided behavior in P. pacificus may therefore have an important ecological component.     

Detection of a rare oligo(A) repeat tract mutation (8As-->7As) in the sequence encoding the La/SS-B autoantigen

Several diseases are characterized by the presence of point mutations, which are amenable to molecular detection using a number of methods such as PCR. However, certain mutations are particularly difficult to detect due to factors such as low abundance and the presence of special (e.g., oligonucleotide repeat) sequences. The mutation 7A in the oligoA sequence of exon 7 of the gene encoding the La autoantigen is difficult to detect at the DNA level, and even at the RNA level, due to both its estimated low abundance and its differentiation from the wild-type 8A sequence. This article describes a technique in which amplification of the excess wild-type 8A La sequence is suppressed by a peptide nucleic acid (PNA) during a nested PCR step. Detection of the amplified 7A mutant form was then performed by simple electrophoresis following a final primer extension step with an infrared dye-labeled primer. This technique allowed us to detect the mutation in 3 of 7 individuals harboring serum immunoglobulin G (IgG) antibodies reactive with a neo-B cell epitope in the 7A mutant protein product. We propose that this method is a viable screening test for mutations in regions containing simple polynucleotide repeats.     

Patterns in a species‐rich tropical understory plant community

Understory plants are an important component of the high plant species diversity characteristic of neotropical rain forests. Herbs, shrubs, understory trees, and saplings of canopy trees occupy a broadly uniform environment of abundant rainfall, low light levels, and high humidity. We asked whether this community at the La Selva Biological Station in the Caribbean lowlands of Costa Rica was structured by environmental filters such as soil origin, topographic position, and understory light availability. We used nested quadrats to assess effects of soil origin (recent alluvium, weathered alluvium, residual volcanic soil) and topographic position (ridges, mid‐slopes and flats) on species composition, density, and diversity and measured six edaphic and understory light parameters. Non‐metric multidimensional scaling ordinations were based on frequency of occurrence in 20 quadrats for 272 species in the shrub size class and 136 species in the small‐tree size class for 17 sites. Three axes were correlated with composite environmental variables produced by principal component analysis representing slope, extractable phosphorus, and light. NMS site positions also reflected soil origin, topographic position, and geographic location. The analyses illustrated a complex community structured by species responses to environmental filters at multiple, interdigitated spatial scales. We suggest that light availability affected by canopy dynamics and dispersal limitation provides additional sources of variation in species distributions, which interact with edaphic patterns in complex ways. Abstract in Spanish is available with online material.     

Natural occurrence in Argentina of a new fungal pathogen of cockroaches,Metarhizium argentinense sp. nov.

The aim of this study was to search for entomopathogenic fungi that infect wild cockroaches in forest ecosystems in two protected natural areas of Argentina. Two isolates of Metarhizium argentinense were obtained and identified from wild cockroaches (Blaberidae: Epilamprinae) through the use of morphological characteristics and molecular phylogenetic analyses. This novel species was found in Argentina and is a member of the Metarhizium flavoviride species complex. Phylogenetic analyses, based on sequence similarity analysis using internal transcribed spacer (ITS) and a set of four protein-coding marker sequences (EF1A, RPB1, RPB2 and BTUB), supported the status of this fungus as a new species. In addition, we tested the biological activity of the new species through assays against Blattella germanica nymphs and found that the two evaluated isolates were pathogenic. However, isolate CEP424 was more virulent and caused a confirmed mortality of 76 % with a median lethal time of 7.2 d. This study reports the southernmost worldwide location of a Metarhizium species that infects cockroaches and will help expand the knowledge of the biodiversity of pathogenic fungi of Argentine cockroaches.     

Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest

In tropical forest communities, seedling recruitment can be limited by the number of fruit produced by adults. Fruit production tends to be highly unequal among trees of the same species, which may be due to environmental factors. We observed fruit production for ~2,000 trees of 17 species across 3 years in a wet tropical forest in Costa Rica. Fruit production was modeled as a function of tree size, nutrient availability, and neighborhood crowding. Following model selection, tree size and neighborhood crowding predicted both the probability of reproduction and the number of fruit produced. Nutrient availability only predicted only the probability of reproduction. In all species, larger trees were more likely to be reproductive and produce more fruit. In addition, number of fruit was strongly negatively related to presence of larger neighboring trees in 13 species; presence of all neighboring trees had a weak‐to‐moderate negative influence on reproductive status in 16 species. Among various metrics of soil nutrient availability, only sum of base cations was positively associated with reproductive status, and for only four species. Synthesis Overall, these results suggest that direct influences on fruit production tend to be mediated through tree size and crowding from neighboring trees, rather than soil nutrients. However, we found variation in the effects of neighbors and nutrients among species; mechanistic studies of allocation to fruit production are needed to explain these differences.     

A newly recognized Mesozoic–Recent interspecific association: calcifying bacteria on decapod crustaceans

Using microscopy and spectroscopy tools, we succeeded in identifying undescribed diminutive epibionts (as epibiotic bacterial colonies) both on exceptionally well‐preserved fossil shrimps and on extant taxa (N. Robin, S. Bernard, J. Miot, M.‐M. Blanc‐Valleron, S. Charbonnier & G. Petit, submitted). This study outlines the ecological parameters of this totally newly recognized interspecific association. To this aim, the systematics and environmental setting of fossil and modern decapod hosts are described; count of bacterial colonies is made to assess prevalence and intensity; scanning electron microscopy is used to illustrate colonial growth patterns; and histological sections of the extant colonies nested in cuticle are stained to determine their incidence on the carapace of their decapod hosts. Thus, the prevalent and intense association is found on decapods of the superfamily Penaeoidea Rafinesque‐Schmaltz 1815 occupying up to 2 cm² of the entire carapace. The association is here observed in deep environments such as that of the Jurassic La Voulte‐sur‐Rhône Lagerstätte. A non‐random distribution of colonial growth patterns is determined; it illustrates a favourite access site along the ventral margin of the shrimp carapace. SEM images and stained sections reveal strong colony embedment within the cuticle, but also damage such as erasing of the cuticular layers. This bioeroding effect, possibly linked to a feeding benefit to the bacteria, brings this interspecific association that has existed, for at least 160 myr, near to parasitism. In addition to illustrating a rare case of interaction in Recent forms that could be described due to previous recognition in fossils, it constitutes a textbook example of the preservation of intimate interactions through geological time.     

La autoantigen suppresses IRES-dependent translation of the hepatitis A virus

The human RNA-binding protein La, is an essential trans-acting factor in IRES-dependent translation initiation of poliovirus, the prototypic picornavirus. For hepatitis A virus (HAV), an unusual member of this virus family, the role of host proteins in its inefficient translation and slow replication is unclear. Using small interfering RNA in vivo and purified La in vitro, we demonstrate for the first time that La suppresses HAV IRES-mediated translation and replication. We show that La binds specifically to distinct parts of the HAV IRES and that—unlike poliovirus—HAV proteinase 3C does not cleave La. The La-mediated suppression of HAV translation and stimulation of poliovirus translation implies unexpected mechanistic differences between viral IRES elements.     

The influence of upwelling,coastal currents and water temperature on the distribution of the red tide dinoflagellate, <Emphasis Type="Italic">Noctiluca scintillans</Emphasis>, along the east coast of Australia

Quasi-synoptic surveys along the east coast of Australia between 28 and 34°S show that the heterotrophic dinoflagellate, Noctiluca scintillans, occurs along this entire stretch of the coast. Areas of relatively high abundance of Noctiluca were observed downstream of regions predisposed to current-induced upwellings as a consequence of alongshore topographic variations. High-resolution temporal and spatial sampling of upwelling events showed that Noctiluca was abundant (up to 28 cells l^?1) within mature upwelled waters. A high proportion (>80%) of fed Noctiluca cells (cells with prey in their vacuoles) was observed in the mature upwelled waters indicating that the observed increase in abundance of Noctiluca was associated with increased feeding activity. The absolute abundance of Noctiluca in upwelled waters was, however, found to vary from one upwelling location to another and between seasons. In particular, highest abundances of Noctiluca were recorded south of 31.5°S, where the East Australian Current (EAC) characteristically separates from the coast. The high abundances partly arise from southward advection and retention of the Noctiluca cells, and partly from upwelling inshore of the separated EAC driven by cross-shelf boundary layer fluxes. The temperature of the EAC was also found to influence absolute abundances. Surface water temperatures during our summer cruise were anomalously high due to a strong La Niña phase, and up to 4°C warmer than during our spring cruise. We found that the warmer surface water temperatures were associated with relatively lower average abundances of Noctiluca in the near shore zone.