Localisation and surface quantification of secondary metabolites in the red alga Delisea pulchra

The localisation of halogenated furanones, the biologically active secondary metabolites from the red alga Delisea pulchra (Greville), was determined by a combination of fluorescence microscopy, culture studies and quantitative chemical analyses. All types of evidence showed that furanones are localised in the central vesicle of gland cells in D. pulchra. These cells release furanones onto the surface of the plant, where they can be quantified using a newly developed surface extraction-technique. Levels of furanones on the surface of the plant were highest near the apical tips (≃100 ng cm⁻²), and decreased towards the base of the alga. Variation in furanone levels within the plant and variation in the number of gland cells followed a similar pattern. The localisation of furanones within gland cells in D. pulchra and the presence and concentrations of furanones on the surface of the plant are consistent with furanones functioning as antifoulants and in mediating other ecological interactions at the surface of the alga. Received: 5 March 1998 / Accepted: 10 September 1998     

Potential for long-distance dispersal of Euphausia crystallorophias in fast current jets

The euphausiid Euphausia crystallorophias Holt and Tattersall, 1906 is considered to be a neritic species. It has been found in greatest abundance along the Antarctic continental margins, often in association with regions of pack ice. Although E. crystallorophias has been observed at some islands to the west of the Antarctic Peninsula, the species has not previously been reported from islands of the maritime- or sub-Antarctic further north. During an oceanographic transect in November 1997 from South Georgia to the South Sandwich Islands, acoustic observations revealed a dense, discrete pelagic target at 50 m. The target was fished and was found to be an aggregation of small E. crystallorophias. The fishing location (54.48°S; 30.61°W) was >1500 km from the Antarctic continent, and >250 km from the nearest land, in water of several thousands of metres depth – clearly a non-neritic environment. Examination of hydrographic data revealed that the E. crystallorophias swarm had been located within a fast-flowing band of water that had characteristics of water found near the Antarctic Peninsula. This band was ≃150 km wide, and had a speed ranging from 9 to 22 km d⁻¹ in a north-easterly direction. The possible origins of this E. crystallorophias swarm are explored in the light of the eddy-dominated current patterns prevalent in the Weddell–Scotia Confluence region, and with reference to published growth-rate estimates for the species. We discuss the potential for long-distance dispersal of E. crystallorophias and other neritic species in fast current jets, and examine how such oceanographic features could facilitate long-distance dispersal, colonization, and gene flow. Received: 23 November 1998 / Accepted: 25 March 1999     

A multi-factorial experiment on heart rate variations in the intertidal crab Pachygrapsus marmoratus

A multi-factorial experiment was designed to investigate the effect of the following factors on the cardiac activity of the intertidal crab Pachygrapsus marmoratus: respiratory medium (air, water), temperature (four levels, 10, 17.5, 25, 32.5 °C), season (winter, summer) and body size (two levels, carapace ≤21 mm and carapace >21 mm). The results showed that the heart rate of P. marmoratus increased linearly with temperature and decreased when the specimens were exposed to air rather than water. Moreover, the heart rate values in summer were lower than those in winter at the corresponding temperature and body size. The summer heart rate–temperature regression line was laterally (to the right) shifted with respect to the winter line, suggesting a seasonal acclimation. Body size affected heart rate only at the acclimation temperature (17.5 °C), while no significant effect was detected at lower or higher temperatures. During the reproductive season a separate experiment was carried out to assess the effect of sex and reproductive status on heart rate. No significant difference was found among mean values of males, berried females and females without eggs. The results of the present study confirm the high physiological plasticity of this species, suggesting that P. marmoratus is a truly amphibious crab, able to deal with both water- and air-breathing during its activity. Received: 5 January 1999 / Accepted: 7 July 1999     

Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores

We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton. Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within this range, colors are well-adapted to the particular environment which the species inhabit. Received: 27 April 1998 / Accepted: 27 October 1998     

Lethal and sub-lethal effects of phototrophic endoliths attacking the shell of the intertidal mussel Perna perna

Animals that bore into calcareous material can cause considerable damage to molluscan shells. In contrast, smaller microbial phototrophic endoliths have until recently been thought of as relatively benign. Phototrophic endoliths (primarily cyanobacteria) infest the shells of 50 to 80% of midshore populations of the mussel Perna perna (L.) in South Africa. This infestation causes clearly visible shell degradation, and we record here ecologically important lethal and sub-lethal effects (e.g. changes in growth and reproductive output) of the endoliths on their mussel hosts. Endolith infestation reduced the strength of shells significantly and also affected shell growth. In situ marking of shells, using the fluorochrome calcein, showed that infested and non-infested mussels increased in shell length at the same rate. However, the rate of increase in shell thickness (associated with shell repair) was significantly faster in infested than in uninfested individuals. This increase in the rate of shell thickening was not sufficient to compensate for rapid endolith-induced shell degradation and, around the site of adductor muscle attachment, infested shells were thinner than their uninfested counterparts. The shells of 18% of recently dead mussels had holes induced by endolith erosion. This effect was highly size dependent, and the proportion of mortality due to endoliths rose to almost 50% for the largest mussels. The re-routing of energy due to shell repair had important sub-lethal effects on the reproductive rates of mussels. During the reproductive period, mean dried flesh mass for large (>70 mm), non-infested P. perna was substantially higher than for infested individuals. This difference was almost entirely due to differences in gonad mass, which was approximately 100% higher for non-infested mussels. We conclude that, by attacking the shell, phototrophic endoliths reduce both the longevity and reproductive output of large mussels on the midshore. Received: 26 January 1999 / Accepted: 17 August 1999     

Mating system evolution in response to search costs in the speckled wood butterfly, Pararge aegeria

A general and intuitive prediction from models of mate preference is that when the cost of searching for mates increases, individuals should become less choosy. Here, we test this prediction by comparing the mating propensity of females in two populations of the butterfly Pararge aegeria. The populations originated from southern Sweden and Madeira and due to different adult emergence patterns throughout the year, the average density of males per female is likely to be lower on Madeira. Therefore, we expected that the cost of searching should be greater on Madeira and, consequently, that the Madeiran females should be less choosy. In line with predictions, the Madeiran females mated significantly sooner after the first interaction with males than did females from southern Sweden. This difference may reflect a weaker preference for territorial males over non-territorial patrollers in the Madeiran population, because of the greater costs of searching. The Madeiran females also showed a shorter time lag between mating and the start of oviposition. We discuss this unexpected result and propose that the same mechanism could also explain this population difference, i.e. different costs of searching for suitable host plants. Both search processes are fundamental for female reproductive success and we find it plausible that they can be generalised into the same theory of optimal search behaviour. Received: 14 May 1998 / Accepted after revision: 13 December 1998     

Aphids are unaffected by the elemental defence of the nickel hyperaccumulator Streptanthus polygaloides (Brassicaceae)

Summary. Nickel hyperaccumulation, resulting in plant Ni contents of >1000 mg kg^у dry mass, has been shown to defend plants against folivorous herbivores. We determined whether this elemental defence tactic protected hyperaccumulating plants from attack by a phloem-feeding herbivore. We used the pea aphid, Acyrthosiphon pisum, and the Ni-hyperaccumulating plant Streptanthus polygaloides. Aphids were allowed to colonize mixed arrays of S. polygaloides in which plants either were hyperaccumulating Ni, not hyperaccumulating Ni and treated with a systemic insecticide, or not hyperaccumulating Ni. Aphid numbers g^у dry mass of plant biomass were lowest for the insecticide treatment, intermediate for low-Ni plants, and highest for plants hyperaccumulating Ni. Artificial liquid aphid diet, amended with varying levels of Ni, resulted in decreased aphid survival at 2500 mg kg^у Ni dry mass (or 5.03 mM Ni). We concluded that Ni levels in the phloem of hyperaccumulating plants of S. polygaloides were < 5.03 mM and, as a result, were not effective in defending plants against aphid attack.     

Trends in Wildlife Management and the Appropriateness of Australian University Training

Abstract: That the greatest challenges in conservation are often not technical but rather economic or sociological has been expressed for at least the last 20 years. This raises the question of whether the training offered to tomorrow's conservation practitioners prepares them sufficiently to deal with the human dimensions of conservation. We analyzed 747 papers from seven wildlife management and conservation biology journals to determine the trends in this area of conservation management between 1985 and 1995. We found that over that time the emphasis stayed on single-species issues with a science focus, but there was a marked shift toward conservation biology issues, management-oriented research, and discussion of economic and social factors relevant to management. We also examined the handbooks of 11 Australian universities to analyze the content of 439 compulsory subjects in 12 degrees that we judged could produce wildlife managers. More than 68% of subjects were from a basic science or technology discipline, 16% from resource management, and only 13% from economics, humanities, communications, or planning. Thus, many of the skills required by contemporary wildlife managers must be learned in postgraduate training or on the job. Much of the undergraduate training syllabus, in Australia at least, does not reflect trends in the practice of wildlife management today and will not provide tomorrow's managers with the range of disciplinary understanding required. We were able, however, to identify three types of undergraduate training—ecological system managers, environmental managers, and human system managers—and we found that the curricula in human-system management contained increased emphasis on socioeconomic issues relevant to management.     

War Zones and Game Sinks in Lewis and Clark's West

The journals of Lewis and Clark reveal a major difference in the taxa, numbers, and behavior of megafauna on either side of the Rocky Mountains in western North America. Two prior events set the stage for what Lewis and Clark would find. The first was the extinction around 13,000 years ago of two-thirds of the native megafauna of the American West. The second was the effects on Indians of deadly new diseases and new technologies brought by Europeans in the post-Columbian era. Populations of large animals, which were preferred prey for native people, were not immune to European influence. Along the Columbia River corridor west of the Rockies, tens of thousands of people lived in a game sink. Here Lewis and Clark's party found too few animals to live off the land by hunting. They adapted poorly to the local diet of fish and roots offered by the Nez Perce and bought dogs and horses to sustain themselves. To the east, uninhabited lands along the Upper Missouri and the Yellowstone rivers supported an abundance of wild game, especially bison, elk, deer, pronghorn, and wolves. This game source occupied part of a buffer zone of 120,000 km² probed by various Indian war parties, some of them armed with muskets. William Clark recognized the relationship and near the end of their journey he wrote that they found large numbers of large animals in the land between nations that were at war. Both the abundance of game in buffer or war zones and scarcity of big game in sinks have been misinterpreted as a natural or typical condition. Although efforts to restore ecosystems to what is described in early journals may have merit, they are aimed at a flickering target. Long before these journals were written, the land had been stripped of most of its native megafauna through human influence. In the absence of humans, we predict that much larger populations of bison, elk, deer, and wolves would have ranged the West than were reported in historic documents.