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.     

Cell and molecular biology of bryophytes: ultimate limits to the resolution of phylogenetic problems

Ultrastructure, biochemistry and 5S rRNA sequences link tracheophytes, bryophytes and charalean green algae, but the precise interrelationships between these groups remain unclear. Further major clarification now awaits primary sequence data. These are also needed to determine directionality in possible evolutionary trends within the bryophytes, but are unlikely to overturn current schemes of classification or phylogeny. Comparative ultrastructural studies of spermatogenesis, sporogenesis, the cytoskeleton and plastids reinforce biochemical and morphogenetic evidence for the wide phyletic discontinuities between mosses, hepatics and hornworts, and also rule out direct lines of descent between them. Direct ancestral lineages from charalean algae to bryophytes and to tracheophytes are also unlikely. EM studies of gametophyte/sporophyte junctions, plus immunological investigations of bryophyte cytoskeletons, are likely to accentuate the differences between mosses, hepatirs and hornworts. Other priorities for systematics include elucidation of oil body ultrastructure, analysis of the changes in nuclear proteins during spermatogenesis and a detailed comparison of bryophyte and charalean plastids. The combined evidence from ultrastrueture, biochemistry, morphology and morphogenesis warrants general acceptance of the polyphyletic origin of the bryophytes. Ultrastructural attributes should be more widely used in bryophyte systematics.     

Comparison of the Disruption of Mitosis and Cell Plate Formation in Oat Roots by DCPA, Colchicine and Propham

Holmsen, J. D. and Hess, F. D. 1985. Comparison of the disruptionof mitosis and cell plate formation in oat roots by DCPA, colchicineand propham.—J. exp. Bot. 36: 1504–1513. Concentrationsof DCPA, propham and colchicine were selected to cause from0% to greater than 60% inhibition of oat (Avena sativa L. ‘Victory’)root growth after 24 h exposure. Root growth progressively declinedas concentrations were raised from 1·0 to 5·6mmol m^–3 DCPA, 1·0–5·0 mmol m^–3propham, and 50–500 mmol m^–3 colchicine. In additionto inhibiting root growth each mitotic disrupter caused theroot tips to swell to an extent dependent upon concentration.All three compounds effectively disrupted mitosis at concentrationsthat caused less than maximal root growth inhibition. Mitoticdisruption was manifest as a reduction in the number of normalmitotic figures and an increase in the number of condensed prophase,multipolar and anaphase bridge division figures. The frequencyof each type of division figure was different for each of thethree compounds. DCPA disrupted mitosis more effectively whencompared with propham and colchicine at concentrations whichcaused the same amount of root growth inhibition. Each mitoticdisrupter also induced the formation of aberrant cell walls.DCPA was the most effective at disrupting cell plate formation,whereas colchicine was least effective. These data suggest thatthe mechanism of action of DCPA is distinct from the mechanismof colchicine or propham Key words: Avena sativa L., mitotic disruption, DCPA, colchicine, propham     

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.

     

Carbon Dioxide Effects on Carbohydrate Status and Partitioning in Rice

The atmospheric carbon dioxide (CO₂) concentration has beenrising and is predicted to reach double the present concentrationsometime during the next century. The objective of this investigationwas to determine the long-term effects of different CO₂ concentrationson carbohydrate status and partitioning in rice (Oryza sativaL cv. IR-30). Rice plants were grown season-long in outdoor,naturally sunlit, environmentally controlled growth chamberswith CO₂ concentrations of 160, 250, 330, 500, 660, and 900µmolCO₂ mol¹ air. In leaf blades, the priority between the partitioningof carbon into storage carbohydrates or into export changedwith developmental stage and CO₂ concentration. During vegetativegrowth, leaf sucrose and starch concentrations increased withincreasing CO₂ concentration but tended to level off above 500µmolmol^–1 CO₂. Similarly, photosynthesis also increased withCO2 concentrations up to 500µmol mol^–1 and thenreached a plateau at higher concentrations. The ratio of starchto sucrose concentration was positively correlated with theCO₂ concentration. At maturity, increasing CO₂ concentrationresulted in an increase in total non-structural carbohydrate(TNC) concentration in leaf blades, leaf sheaths and culms.Carbohydrates that were stored in vegetative plant parts beforeheading made a smaller contribution to grain dry weight at CO₂concentrations below 330µmol mol^–1 than for treatmentsat concentrations above ambient Increasing CO₂ concentrationhad no effect on the carbohydrate concentration in the grainat maturity Key words: CO₂ enrichment, starch, sucrose     

Coccidia of Brazilian Mammals: Eimeria corticulata N. Sp. (Apicomplexa: Eimeriidae) from the Anteater Tamandua tetradactyla (Xenarthra: Myrmecophagidae) and Eimeria zygodontomyis N. Sp. from the Cane Mouse Zygodontomys lasiurus (Rodentia: Cricetidae)

Feces from a specimen of Tamandua tetradactyla (Linn.) from Portel, Para State, north Brazil, contained two different coccidial oocysts; one identified as Eimeria tamanduae Lainson 1968, and the other as a new species, described here as Eimeria corticulata n. sp. Oocysts of E. corticulata are ellipsoidal, 37.4 × 30.4 (31.2–43.7 × 23.7–35.0) μm, shape index (length/width) 1.2 (1.0–1.5). Oocyst wall 2.5–3.7 μm thick and composed of two layers; an outer thick, brown-yellow one with radial striations, and a thin inner smooth one: no visible micropyle. Oocyst residuum a large globule of about 10.7 × 10.3 μm, usually accompanied by a number of smaller attached globules. Sporocysts ellipsoidal, 21.0 × 11.0 (20.0–22.5 × 10.0–12.5) μm, with a conspicuous Stieda body: shape index 1.9 (1.6–2.2). Sporocyst residuum a small number of scattered granules: sporozoites 18.7 × 5.0 μm, with a large posterior refractile body. Eimeria zygodontomyis n. sp. is described in feces from Zygodontomys lasiurus (Lund) from the Serra dos Carajas, Para. Oocysts ellipsoidal to cylindrical, 16.5 × 12.0 (13.7–18.7 × 11.2–12.3) μm, shape index 1.4 (1.2–1.5). Wall colorless, smooth, single-layered and about 0.6 μm thick: no micropyle. No oocyst residuum, but a polar granule of about 1.8 × 1.0 μm is sometimes present. Sporocysts ellipsoidal, 8.4 × 5.5(7.5–8.7 × 5.0–6.2) μm, shape index 1.5 (1.4–1.7), with a thin colorless wall and a delicate Stieda body. Sporozoites enclose a compact residuum of about 2.5 × 3.7 μm.     

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.     

The effect of suspended clay on ciliate population growth rates

• 1 Renewed batch cultures of three algivorous and one bacterivorous ciliate showed that ciliate reproductive rates increase with increasing food concentration up to an asymptote. Maximum r_m values for Strobilidium gyrans, Bursaridium difficile and Euplotes eurystomus feeding on the cryptomonad alga Rhodomonas minuta were 0.87, 0.86 and 0.45 day-¹, respectively, while Paramecium aurelia feeding on the bacterium Enterobactor aerogenes had an r_m of 0.40 day-¹. B. difficile had a food threshold (r_m= 0) of 0.38 μg Cml-¹ and P. aurelia had a threshold of 1.6μg Cml-¹.
• 2 The presence of suspended fine (particle size <1 μm) and coarse (particle size 1–2μm) clay suppressed the half maximum reproductive rate of the ciliate Strobilidium gyrans by up to 69% but had no effect on B. difficile, E. eurystomus or P. aurelia. Populations of ciliates unaffected by clay may be released in situations where suspended particles negatively affect their metazooplankton predators and competitors.