Cuticle development and ultrastructure: evidence for a procuticle of high osmium affinity

Transmission electron microscopy was used to investigate the development and ultrastructure of the cuticles of the bladder primordium and other parts of Utricularia, the stem of Cuscuta gronovii, and the leaves of Athanasia parviflora. In all materials investigated, except the apical meristem of Cassytha pubescens, the first-formed cuticle, named the procuticle, was very electron dense and apparently amorphous in texture. Later, the procuticle changed its ultrastructural appearance: in all species having a procuticle it lost much of its electron density. Simultaneously, it developed into a lamellar structure in U. lateriflora and Cuscuta, and became part of a lamellar cuticle proper. In U. sandersonii and Athanasia the procuticle generally remained without visible structure. The velum of the pavement epithelium of Utricularia is considered to be a slightly modified procuticle which has become loosened from the epithelial cells and stretched.     

Harbour porpoises respond to climate change

The effects of climate change on marine ecosystems and in particular on marine top predators are difficult to assess due to, among other things, spatial variability, and lack of clear delineation of marine habitats. The banks of West Greenland are located in a climate sensitive area and are likely to elicit pronounced responses to oceanographic changes in the North Atlantic. The recent increase in sea temperatures on the banks of West Greenland has had cascading effects on sea ice coverage, residency of top predators, and abundance of important prey species like Atlantic cod (Gadus morhua). Here, we report on the response of one of the top predators in West Greenland; the harbour porpoise (Phocoena phocoena). The porpoises depend on locating high densities of prey species with high nutritive value and they have apparently responded to the general warming on the banks of West Greenland by longer residence times, increased consumption of Atlantic cod resulting in improved body condition in the form of larger fat deposits in blubber, compared to the situation during a cold period in the 1990s. This is one of the few examples of a measurable effect of climate change on a marine mammal population.     

An estimate of the fraction of belugas (<Emphasis Type="Italic">Delphinapterus leucas</Emphasis>) in the Canadian high Arctic that winter in West Greenland

Five belugas, or white whales (Delphinapterus leucas), were tracked by satellite from Creswell Bay, Somerset Island, in the Canadian high Arctic towards West Greenland in autumn 2001. After 1 October, three of the whales stayed in the North Water polynya and the other two whales moved to West Greenland. One of the whales that moved to Greenland migrated south along the west coast, following a route and timing similar to another beluga tracked in 1996. The belugas that moved towards West Greenland from Canada did so before or near 1 October. The movements of both these whales followed a similar timing and assumed migratory route of belugas hunted in autumn in West Greenland. In Greenland, the hunt begins in September, where the first whales are taken in the northernmost community of Qaanaaq. Hunting takes place farther south in Upernavik in October, and finally in November and December, belugas are taken even farther south in Uummannaq and Disko Bay. The whales that remain in the North Water after 1 October most likely do not contribute to the harvest in West Greenland. Based on the total number of belugas satellite-tracked in Canada between 1995 and 2001 with tags that lasted beyond 1 October, approximately 0.15 (95% CI 0.06-0.35; n=26) of the summering stock of belugas in the Canadian high Arctic move to West Greenland for the winter. Genetic studies have indicated that belugas moving east through Lancaster Sound are significantly differentiated from belugas taken in the autumn hunt in West Greenland. These conflicting results suggest molecular genetics cannot be solely relied on to reveal the stock identity of these belugas.     

Acoustic detection and satellite-tracking leads to discovery of rare concentration of endangered North Pacific right whales

The North Pacific right whale, Eubalaena japonica, is one of the most endangered species of whale in the world. On 10 August 2004, two right whales were located in the Bering Sea using headings to right whale calls provided by directional sonobuoys. A satellite-monitored radio tag attached to one of these whales functioned for 40 days. Over the 40-day period, this whale moved throughout a large part of the southeast Bering Sea shelf, including areas of the outer-shelf where right whales have not been seen in decades. In September, multiple right whales were acoustically located and subsequently sighted by another survey vessel approaching a near-real-time position from the tag. An analysis of photographs confirmed at least 17 individual whales (not including the tagged whales). Genetic analysis of biopsy samples identified 17 individuals: 10 males and 7 females. The discovery of seven females was significant, as only one female had been identified in the past. Genetics also confirmed the presence of at least two calves. Although the future of this population is highly uncertain, the discovery of additional females and calves gives some hope that this most critically endangered of all whale populations may still possess the capacity to recover.     

The haustorium of the root parasite Triphysaria (Scrophulariaceae), with special reference to xylem bridge ultrastructure

Haustoria of Triphysaria pusilla and T. versicolor subsp. faucibarbata from a natural habitat were analyzed by light and electron microscopy. Secretory trichomes (root hairs) participate in securing the haustorium to the surface of the host root. The keel-shaped intrusive part of the secondary haustorium penetrates to the depth of the vascular tissue of the host. Some of the epidermal interface cells differentiate into xylem elements. A significant number of haustoria do not differentiate further, but in most haustoria one to five of the epidermal xylem elements terminate a similar number of xylem strands. The strands mostly consist of vessel members and they connect host xylem or occasionally host parenchyma to the plate xylem adjacent to the stele of the parasite root. Each strand of this xylem bridge is accompanied by highly protoplasmic parenchyma cells with supposed transfer cell function. Increased surface area of the plasmalemma occurs in these cells as it does in interface parenchyma cells. Graniferous tracheary elements are restricted to the haustorium and occur most frequently in the plate xylem. The plate xylem is also accompanied by highly protoplasmic parenchyma cells. Hyphae of mycorrhizal fungi of the host root occasionally penetrate into the distal part of the xylem bridge. We combine structural observations and physiological facts into a hypothesis for translocation of water and nutrients between host and parasite. Some evolutionary aspects related to endogeny/exogeny of haustoria are discussed, and it is argued that the Triphysaria haustorium represents a greatly advanced and/or reduced condition within Scrophulariaceae.     

Acceleration of leaf senescence inFagus sylvatica L. by low levels of tropospheric ozone demonstrated by leaf colour,chlorophyll fluorescence and chloroplast ultrastructure

From April 1988 to October 1991 3-year-old seed propagated beech (Fagus sylvatica L.) trees were exposed in open-top chambers to four different levels of air pollution: (1) charcoal filtered air, (2) ambient air, (3) ambient air plus 30 nl 1^-1 ozone during the summer, and (4) ambient air plus 30 nl 1^-1 ozone during the summer and 20 nl 1^-1 SO₂ and NO₂ during the winter. Leaf colour was studied in the autumns of 1989 and 1991 and a close relationship between ozone dose and premature senescence was found. A correlation also exists between the colour groups and chlorophyll fluorescence (F_v/F_m). Ozone fumigation increases the size and speeds up the development of the plastoglobules. This is described using an index based on the volume of plastoglobules as a percentage of chloroplast volume. The index was significantly higher for ozone fumigated plants than for control plants during August to November 1989. According to all three methods it is concluded that low levels of ozone accelerate leaf senescence processes inF. sylvatica. There are indications that leaves of the first and the second flush react differently to the ozone treatment. Irrespective of the ozone treatment a special cell wall structure, probably a local suberization, is confined to the subsidiary cells in leaves of the first flush.     

The effects of UV-B radiation on European heathland species

The effects of enhanced UV-B radiation on three examples of European shrub-dominated vegetation were studied in situ. The experiments were in High Arctic Greenland, northern Sweden and Greece, and at all sites investigated the interaction of enhanced UV-B radiation (simulating a 15% reduction in the ozone layer) with artificially increased precipitation. The Swedish experiment also involved a study of the interaction between enhanced UV-B radiation and elevated CO₂ (600 ppm). These field studies were supported by an outdoor controlled environment study in the United Kingdom involving modulated enhancement of UV-B radiation in combination with elevated CO₂ (700 ppm). Effects of the treatments on plant growth, morphology, phenology and physiology were measured. The effects observed were species specific, and included both positive and negative responses to the treatments. In general the negative responses to UV-B treatments of up to three growing seasons were small, but included reductions in shoot growth and premature leaf senescence. Positive responses included a marked increase in flowering in some species and a stimulation of some photosynthetic processes. UV-B treatment enhanced the drought tolerance of Pinus pinea and Pinus halepensis by increasing leaf cuticle thickness. In general, there were few interactions between the elevated CO₂ and enhanced UV-B treatments. There was evidence to suggest that although the negative responses to the treatments were small, damage may be increasing with time in some long-lived woody perennials. There was also evidence in the third year of treatments for effects of UV-B on insect herbivory in Vaccinium species. The experiments point to the necessity for long-term field investigations to predict the likely ecological consequences of increasing UV-B radiation.     

Identifying gray whale (Eschrichtius robustus) foraging grounds along the Chukotka Peninsula, Russia, using satellite telemetry

The purpose of this study was to evaluate summer and fall residency and habitat selection by gray whales, Eschrichtius robustus, together with the biomass of benthic amphipod prey on the coastal feeding grounds along the Chukotka Peninsula. Thirteen gray whales were instrumented with satellite transmitters in September 2006 near the Chukotka Peninsula, Russia. Nine transmitters provided positions from whales for up to 81?days. The whales travelled within 5?km of the Chukotka coast for most of the period they were tracked with only occasional movements offshore. The average daily travel speeds were 23?km?day^?1 (range 9–53?km?day^?1). Four of the whales had daily average travel speeds <1?km?day^?1 suggesting strong fidelity to the study area. The area containing 95% of the locations for individual whales during biweekly periods was on average 13,027?km² (range 7,097–15,896?km²). More than 65% of all locations were in water <30?m, and between 45 and 70% of biweekly kernel home ranges were located in depths between 31 and 50?m. Benthic density of amphipods within the Bering Strait at depths <50?m was on average ~54?g wet wt m^?2 in 2006. It is likely that the abundant benthic biomass is more than sufficient forage to support the current gray whale population. The use of satellite telemetry in this study quantifies space use and movement patterns of gray whales along the Chukotka coast and identifies key feeding areas.     

Presence and behavior of bowhead whales (Balaena mysticetus) in the Alaskan Beaufort Sea in July 2011

The Western Arctic bowhead whale (Balaena mysticetus) is highly adapted to sea ice and annually migrates through the Bering, Chukchi, and Beaufort seas. While the overall distribution and seasonal movements of bowhead whales are mostly understood, information about their distribution in the Alaskan Beaufort Sea in early to mid-summer has not been well documented. In July 2011, we conducted an exploratory flight in the Alaskan Beaufort Sea, north of Camden Bay (71°N 144°W), near the location of a single satellite-tagged bowhead whale. Eighteen bowhead whales were observed, and behavior consistent with feeding was documented. To our knowledge, this is the first documentation of behavior consistent with feeding north of Camden Bay in mid-July. Few studies have focused on bowhead whale distribution in the Alaskan Beaufort Sea in early to mid-summer, and no long-term, region-wide surveys have been conducted during summer. Bowhead whales are already exposed to anthropogenic disturbance in the Canadian Beaufort Sea in summer, the Alaskan Beaufort Sea in fall, and the Chukchi and Bering seas from fall through spring. The presence of bowhead whale aggregations in the Alaskan Beaufort Sea in summer should be considered when assessing the cumulative effects of human-related activities.     

Epidermal derivatives as xylem elements and transfer cells: a study of the host-parasite interface in two species of Triphysaria (Scrophulariaceae)

Summary Haustoria ofTriphysaria pusilla andT. versicolor subsp.faucibarbata from a natural habitat were analysed by light and electron microscopy. The keel-shaped edge of the secondary haustorium generally splits the epidermis and cortex of the host root parallel to the root axis, and penetrates to the host vascular tissue. Anticlinally elongated epidermal cells of the haustorium constitute most of the host/parasite interface. Some of these epidermal cells are divided by oblique cell walls. Some of their oblique daughter cells as well as some undivided epidermal cells differentiate into xylem elements. Single epidermal cells occasionally intrude into the vascular tissue of the host and individual host cells can be invaded. The surface area of the plasmalemma in parasitic parenchymatous interface cells is increased by the differentiation of wall labyrinths characteristic of transfer cells and by the development of membrane-lined cytoplasmic tubules or flattened sacs which become embedded in the partly lignified interface cell-wall. Mycorrhizal fungal hyphae enter the xylem bridge in some haustoria. Implications of these observations for the function of the haustorium are discussed.