The Nene Branta sandvicensis Recovery Initiative: research against extinction

Since 1960, about 2150 Hawaiian Geese or Nene Branta sandvicensis were reintroduced in Hawaii to supplement the remaining wild population of about 30 birds. These geese were released mostly in high mountain sanctuaries. These sites became unsuitable during prolonged drought and the few surviving birds were those which had moved away from the release sites. The geese that survived had moved to, or were released near, agricultural pasture land. About 600 Nene are currently living in the wild; numbers are declining on the island of Hawaii, stable on Maui and increasing on Kauai. Management priorities include enhancement of grasslands, predator control and maximizing genetic diversity. To enable the species to recover, management will probably have to be large scale, intensive and prolonged. Further released captive-bred or translocated Nene should have access to enhanced habitats after predators have been controlled.     

Deterrent effect of carboxylic acids on cabbage root fly oviposition

In laboratory experiments, 11 selected carboxylic acids were tested to determine which part of the sinapic acid molecule is responsible for deterring cabbage root fly from laying its eggs on otherwise-acceptable cauliflower host-plants. The deterrent effect was only obtained with compounds containing at least one carboxylic group in the molecule. Hence, the aliphatic acids were as deterrent as the aromatic acids to the fly and all the carboxylic acids were as deterrent as sinapic acid, reducing oviposition by > 50%. The inclusion of two carboxylic groups in the molecule, (e.g. phthalic acid and oxalic acid) did not increase the deterrent effect observed with sinapic acid. Some of the long chain fatty acids, with low volatility, low water solubility and thus greater persistence, offer practical opportunities for deterring Delia radicurn from laying its eggs on plants in the field.     

THE ORIGIN OF THE SPINNING APPARATUS IN SPIDERS

• 1 Previous attempts to explain the evolution of spider silk have relied heavily on conjecture. The formulation of testable historical hypotheses to replace such speculation is discussed.
• 2 The importance of phylogenetic reconstructions and other historical hypotheses for use in generating and testing hypotheses concerning the evolution of specific adaptations is examined. Recent ideas on arachnid phylogeny are reviewed and their relevance to the problem of silk evolution in spiders is explored.
• 3 Evidence from the analysis of three historical problems (origin of spinnerets, origin of silk glands, original selective pressure favouring evolution of silk) is reviewed from three different frames of reference (in-group analysis, out-group analysis, convergence analysis). Several lines of evidence are found which suggest that silk use originated in spiders due to selective pressures associated with reproduction (specifically, the transfer of sperm or the protection of eggs).
• 4 The prevalence of segmental appendages retained for use in manipulating genital products in both arachnids and non-arachnid arthropods and the probable placement of spinnerets near the genital opening in ancestral spiders suggest that spinnerets represent modified gonopods.
• 5 The most primitive types of silk glands are retained in virtually all spiders, in part, for use in the construction of sperm webs and egg sacs. Similar silk glands are found near the genital opening in many male spiders and used in building a portion of the sperm web.
• 6 The silk of adult arthropods other than spiders is used largely in manipulating or protecting sex cells. If there are multiple functions, use in reproduction is typically one of them. Thus, there is evidence for strong selective pressure favouring the evolution of silk for use in reproduction.
• 7 Two hypotheses are proposed which are consistent with the conclusion that silk in spiders evolved for reproductive needs (the spermatophore-sperm web and egg sac hypotheses). Testable predictions of each hypothesis are proposed.

     

Powdery mildew of tobacco (Erysiphe cichoracearum DC)

A Hirst volumetric spore trap, at a height of 30 cm., was used to assess the diurnal distribution of Erysiphe conidia in the air in tobacco crops infected with E. cichoracearum in Rhodesia. Air temperature and humidity, and the length of time leaves were wet each day, were also recorded at the same height, amongst the plants. In four seasons, most conidia were caught between 13.00 and 15.00 hr. There were close positive correlations in 1962 between numbers of conidia per m.3 of air per hour and saturation deficit and air temperature during the same hours (10.00–18.00 hr.) Correlations of total Erysiphe conidia per day with temperature and humidity were very variable; temperature had no apparent effect during three seasons, but in one (1961)there was a highly significant positive correlation between numbers of conidia and the daily duration of temperatures > 25d? C. More conidia were also caught when the air was dry for long periods that season, though temperature probably had the greater effect. In 1962, more conidia were caught per day the longer the air was humid (s.D. 0–1 mb.) In 1961, the amount of rain per day had no apparent effect on numbers of conidia, but in 1962 more were caught the greater the daily rainfall. However, rain, which nearly always fell in the afternoon, also removed most conidia from the air that afternoon. Neither windspeed nor duration of leaf wetness appeared to affect spore dispersion.     

Ecological, Evolutionary, and Physical Factors Influencing Aquatic Animal Respiration

Compared to air-breathers, animals that respire aquaticallyhave limited access to O₂ and their habitats are more subjectto hypoxia. Because O₂ diffuses more slowly through water thanair, animals in water experience greater diffusion boundarylayer effects on respiratory gas diffusion. While ventilationand specialized exchange surfaces mitigate O₂ diffusion limitationson respiration, most animal phyla, particularly those confinedto aquatic habitats, lack these. Diffusion limitation influencesthe ontogeny of aquatic animals and may have also shaped Precambrianmetazoans. In spite of a more limited O₂ access, aquatic animalsdisplay a much greater spectrum of respiratory adaptation, rangingfrom the loss of Hb in icefishes to the independent evolution,invention, and acquisition of Hb in many invertebrates confinedto hypoxic habitats. Three features of aquatic respiratory systemsdistinguishing them from aerial systems are the widespread occurrenceof integumental respiration, the frequent presence of combinedrespiratory and feeding surfaces, and the profound effect ofhypoxia on shaping respiratory adaptation, both in shallow waterand in the deep sea.     

Heterogeneous Regulation of Steroid Hormone Receptors in the Brain

SYNOPSIS. The ovarian steroid hormones, estradiol and progesterone,act in the guinea pig brain to regulate the expression of sexualbehavior. In studies of the cellular mechanisms of steroid hormoneaction, we have used an immunocytochemical technique to studythe regulation of these receptors in different neuroanatomicalregions. We have observed that progestin receptor-immunoreactivityin cells in certain neuroanatomical regions are more responsiveto particular steroid hormone treatments than are cells in otherregions. Similarly, we have observed selective regulation ofprogestin receptor-immunoreactivity in neurons identified onthe basis of their neuropeptide content. Finally, in the rostralpart of the ventrolateral hypothalamus, a site involved in hormonalregulation of female sexual behavior, estrogen receptor-immunoreactiveneurons that have dopamine-ß-hydroxylase varicositiesclosely-associated have higher levels of immunostaining forestrogen receptors than neurons without this relationship. Takentogether, these studies demonstrate the possibility of studyingthe microregulation of steroid hormone receptors in subsetsof neurons defined by neuroanatomical location, neuropeptide/neurotransmittercontent, afferent input and projection sites. The ability tostudy interactions among different systems at the cellular levelmay help us to understand more clearly the cellular processesinvolved in hormonal regulation of fundamental neuroendocrineprocesses, including the neuroendocrine regulation of sexualbehavior     

Priority effects among young‐of‐the‐year fish: reduced growth of bluegill sunfish (Lepomis macrochirus) caused by yellow perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age‐0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age‐0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age‐0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (<4 mg wet weight L^?1), predation by age‐0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. <1.0 mg wet weight L^?1). The exception was 2005 when age‐0 yellow perch were absent. 3. Growth of age‐0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (>4 mg wet weight L^?1) compared with the other years (<0.2 mg wet weight L^?1). 4. We conclude that age‐0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age‐0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age‐0 yellow perch when competing with age‐0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age‐0 yellow perch densities.     

Muscular anatomy of a whipspider, Phrynus longipes (Pocock) (Arachnida: Amblypygi), and its evolutionary significance

Skeletal muscles in the whipspider Phrynus longipes are surveyed and compared with those of other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of the arachnids. Representatives of 115 muscle groups are described and illustrated, and their possible functions are proposed. Principal results of this analysis include new functional models for the operation of the pharyngeal and sternocoxal mechanisms in Amblypygi and a greatly expanded list of apparently unique synapomorphies supporting the monophyly of Pedipalpi (= Amblypygi, Schizomida, Thelyphonida).     

Charge Dependent Distribution of Endogenous Proteins within Vitellogenic Ovarian Follicles of Actias luna

In vitellogenic ovarian follicles of Actis luna, internal Ca(2+) activity currents create an electrical gradient which influences the distribution of charged macromolecules between nurse cells and oocyte. We show that, between oocyte and nurse cells, there is an ionic gradient of 1-12 mV with the nurse cells being more electronegative than the oocyte by an average 3.5+/-0.2 mV(s.e.)(p<0.001). As previously reported for another saturniid, Hyalophora cecropia, the transbridge ionic gradient of luna: (1) is focused across the intercellular bridges, (2) is abolished by 200 &mgr;M vanadate and (3) includes a [Ca(2+)](i) gradient. Endogenous soluble proteins collected from control and from vanadate treated populations of nurse cells and oocytes were separated by two-dimensional (2-D) gel electrophoresis and visualized with sliver stain. Densitometric analysis showed that 14 out of the 19 acidic proteins and six of the eight basic proteins studied, changed their oocyte-to-nurse cell distribution in consort with change in the transbridge ionic gradient. This suggests that a transbridge ionic gradient may be, at least within the saturniidae, a method for maintaining different molecular concentrations in nurse cells compared to oocytes. Copyright 1997 Elsevier Science Ltd. All rights reserved