Living on the continental shelf edge: habitat use of juvenile shortfin makos Isurus oxyrinchus in the Great Australian Bight,southern Australia

We used satellite telemetry data to investigate the movement patterns and habitat use of juvenile shortfin makos Isurus oxyrinchus (Lamnidae) tagged in the Great Australian Bight, southern Australia. Tracking durations ranged from 49–672 days and six deployments were > 1 year. During winter and spring, some shortfin makos migrated to the tropical NE Indian Ocean and Coral Sea, and the Subtropical Front region. One shortfin mako undertook an extended migration of 25 550 km across the Indian Ocean. Areas characterized by sea‐mounts in the NE Indian Ocean, the oceanic Subtropical Front region, and the continental shelf edge (200‐m depth) and slope canyons were visited by several sharks. Juvenile shortfin makos used the outer continental shelf, the shelf edge, the slope and oceanic waters during migrations and mostly exhibited fidelity in the mid‐outer shelf, the shelf edge and slope habitats characterized by high bathymetric relief and oceanographic frontal gradients. Our findings highlighted that the continental shelf and slope and associated submarine canyons of the Great Australian Bight represent ecologically important habitats for juvenile shortfin makos. The findings of this study will be pertinent during future management processes for this highly migratory species in this Southern Hemisphere region.     

The use and appreciation of botanical gardens as urban green spaces in South Africa

There are few formal studies on the contribution of botanical gardens as urban green spaces, particularly within developing countries. Therefore, this paper reports on an assessment of the use and appreciation of botanical gardens as urban green spaces in South Africa. Users and staff were surveyed in six national botanical gardens. The gardens provided numerous benefits in terms of conservation, education and recreation. However, the people using the gardens were not demographically representative of the general population of the surrounding city or town. Generally, most of the visitors were middle- to old-aged, well-educated professionals with medium to high incomes. Most were white and English was their home language. There was an even gender representation. Most visited only a few times per year. The majority of users visited the gardens for recreation and psychological reasons rather than educational ones. However, the staff of each garden placed emphasis on education in the gardens and amongst surrounding schools. Most visitors appreciated the conservation dimensions of botanical gardens, and felt that there was insufficient public green space in their town or city. Understanding how people perceive and use the botanical gardens of South Africa is important to inform future research and strategies regarding the conservation of urban green space within a developing country.     

Retinal Photoreceptor Fine Structure in the American Crow (Corvus brachyrhynchos)

The morphology of the light-adapted retinal photoreceptors of the American crow (Corvus brachyrhynchos) has been investigated by light and electron microscopy. They consist of rods, single cones and double (unequal) cones present in a ratio of about 4:3:3 respectively. The rods are stout cells with a long inner segment and an outer segment that reaches to the RPE cell body. In the light-adapted state, the pigment-laden apical processes of the RPE cells surround cell photoreceptor types for most of their length. The rod inner segment displays an ellipsoid of mitochondria, a large hyperboloid of glycogen, much RER, numerous polysomes, Golgi zones and autophagic vacuoles. Single cones show a slightly tapered outer segment, a large and usually heterogeneous oil droplet and an ellipsoid of mitochondria at the apex of the inner segment. Double cones consist of a longer, stouter chief member which displays a more homogeneous oil droplet and a prominent paraboloid of glycogen and a slightly shorter and thinner accessory member with no oil droplet or paraboloid. Both members of the double cone as well as the single cones show a prominent ellipsoid and plentiful polysomes, RER and Golgi zones in the inner segment. Along the length of the contiguous membranes of the two members of the double cone are presumed interreceptor junctions. All cone photoreceptors are relatively small in diameter and hence are tightly packed. Judging by their morphology in the light-adapted state neither rods nor cones are felt to undergo photomechanical movements in this species. Rods and cones (both types) display both invaginated (ribbon) synapses as well as numerous flat (conventional) synaptic sites.     

Retinal Epithelial Fine Structure in the Domestic Cat (Felis catus)

The morphology of the retinal epithelium (RPE) and closely associated choriocapillaris and Bruch's membrane (complexus basalis) has been investigated in the eye of the domestic cat (felis catus) by light and electron microscopy. The RPE consists of a single layer of cuboidal cells joined laterally by apically-located junctional complexes. Basally (sclerally) these cells display numerous infoldings while apically (vitreally) two distinct types of processes enclose photoreceptor outer segments. Internally the large vesicular nucleus is centrally located. Smooth endoplasmic reticulum, mitochondria, polysomes and lysosome-like bodies are abundant. Rough endoplasmic reticulum while present is not plentiful. Over the tapetum lucidum, melanosomes are absent from the RPE cells while in non-tapetal locations melanosomes are large and plentiful. The endothelium of the choriocapillaris is highly fenestrated and these capillaries are deeply indented into the epithelial layer over the tapetum. Bruch's membrane (complexus basalis) is non-tapetal regions is the typical pentalaminate structure noted for most mammals. Over the tapetum however it is reduced to a trilaminate structure and when associated with the indented capillary profiles is further reduced to a single thickened basal lamina.     

Fine Structure of the Bovine Tapetum Fibrosum

The fine structure of the tapetum lucidum of the domestic cow was studied by electron microscopy. In this ungulate the reflective layer is a tapetum fibrosum situated in the choroid and mainly restricted to the superior fundus. The tapetum is composed of a large array of fine extracellular collagen fibrils separated into lamellae by fibrocytes. The collagen fibrils display the normal cross-striations of native collagen, are 0.2 μm in diameter and are arranged in a hexagonal pattern with a center-to-center spacing of about 0.2 μm. The diameter and spacing of these fibrils is consistent with the constructive interference of reflected light. A vascular lamella adjacent to the retinal epithelial layer contains the choriocapillaris and some irregularly arranged collagen fibrils. The tapetum is pierced by blood vessels which supply the choriocapillaris. Over the tapetum the retinal epithelium is non-pigmented while in nontapetal regions this layer is pigmented. The choriocapillaris is not indented into the retinal epithelium as is the case in species with a tapetum cellulosum.     

Fine Structure of the Choriocapillaris, Bruch''s Membrane and Retinal Epithelium of the Cow

The fine structure of the choriocapillaris, Bruch's membrane and retinal epithelium was investigated in both the tapetal and non-tapetal fundus of the bovine eye. In ail locations the retinal epithelium consists of a single layer of cuboidal cells. The epithelial cells are joined laterally by apically located tight junctions and throughout the retina display numerous basal infoldings and fine apical processes which enclose rod outer segments. All retinal epithelial cells are rich in smooth endoplasmic reticulum and mitochondria and contain phagosomes. Although not as abundant, profiles of rough endoplasmic reticulum and polysomes are also noted in all locations. In non-tapetal areas, melano-somes are numerous whereas over the central tapetum fibrosum they are absent. The absence of melanosomes over a functional tapetum is to be expected. While lysosomes are present throughout the epithelial layer, over the tapetal region they appear to be more numerous. The apparent increase in lysosomal numbers in this location may indicate an enhanced shedding of outer segment material over the tapetum. Although some retinal epithelial cells are modified to accomodate a tapetum lucidum their morphology is basically similar throughout the retina and probably indicates that ail regions of the retinal epithelium are capable of the normal functions of this indispensible retinal layer. The choriocapillaris is heavily fenestrated on the border facing the retina and overlying the tapetum also displays fenestrae on its choroidal edge. Bruch's membrane ( complexus basalis ) is pentalaminate throughout the retina and is slightly thicker in the posterior fundus.     

Screening techniques and sources of resistance against parasitic weeds in grain legumes

Summary A number of parasitic plants have become weeds, posing severe constraints to major crops including grain legumes. Breeding for resistance is acknowledged as the major component of an integrated control strategy. However, resistance against most parasitic weeds is difficult to access, scarce, of complex nature and of low heritability, making breeding for resistance a difficult task. As an exception, resistance against Striga gesnerioides based on a single gene has been identified in cowpea and widely exploited in breeding. In other crops, only moderate to low levels of incomplete resistance of complex inheritance against Orobanche species has been identified. This has made selection more difficult and has slowed down the breeding process, but the quantitative resistance resulting from tedious selection procedures has resulted in the release of cultivars with useful levels of incomplete resistance. Resistance is a multicomponent event, being the result of a battery of escape factors or resistance mechanisms acting at different levels of the infection process. Understanding these will help to detect existing genetic diversity for mechanisms that hamper infection. The combination of different resistance mechanisms into a single cultivar will provide durable resistance in the field. This can be facilitated by the use of in vitro screening methods that allow highly heritable resistance components to be identified, together with adoption of marker-assisted selection techniques.     

Environmental biogeochemistry of mercury in Antarctic ecosystems

Polar regions are recognized as important sinks for long-range transport and deposition of Hg derived from natural and anthropogenic sources at lower latitudes. In previous studies we found enhanced Hg accumulation in soils, mosses and lichens from ice-free areas of Victoria Land facing the Terra Nova Bay coastal polynya. This study extends research to the distribution of organic C, total N, S, Hg, Al and Fe in surface soils, cyanobacterial mats and short sediment cores from four lacustrine ecosystems, each with different environmental characteristics and varying distances from the polynya. Results show that planktonic and benthic mats from lakes, along with mosses in the watershed, are the main sinks for Hg in summer meltwater. The C-normalized Hg concentrations in short sediment cores were higher in samples from lakes more exposed to marine aerosols from the coastal polynya. Reactive halogens in the aerosol promote the oxidation and deposition of atmospheric Hg in coastal ecosystems. The analysis of sediment cores did not reveal increasing Hg concentrations in recent sediments, except in the Lake 14 at Edmonson Point. The latter ice-free area is unaffected by the polynya and the increase in Hg concentrations in surface sediments could be due to local changes in lake water level and S biogeochemistry. Although change in sea ice coverage may enhance the role of Antarctic coastal ecosystems as sink in the global Hg cycle, our results seem to exclude possible risks for Antarctic terrestrial and freshwater organisms.