A review of research on the interactions between dugongs (<Emphasis Type="Italic">Dugong dugon</Emphasis> Müller 1776) and intertidal seagrass beds in Indonesia

Research on dugong–seagrass interactions in Indonesia was done during the period 1990 until 2005 in respectively East Aru, Maluku Province and East Kalimantan, Indonesia. This research investigated intensive rotational grazing by dugongs in intertidal inshore Halodule univervis seagrass meadows, dugong movements in relation to these grazing swards, and analyses of parameters explaining the temporal and spatial patterns of grazing in these meadows. In this paper, we report the findings of this long-term study. The patterns of movement and the results of snorkelling surveys confirmed a practice of regular recropping of restricted grazing swards by small feeding assemblages of dugongs. Dugong grazing showed a significant correlation with carbohydrate content of the below-ground biomass and no significant relation with total N. The timing of dugong grazing in these intertidal meadows coincides with high below-ground biomass and high carbohydrate content in the rhizomes of H. uninervis in the upper 0–4 cm sediment layer. Our findings support the hypothesis that temporal dugong grazing is ruled by carbohydrate content in below-ground biomass. The mechanisms of rotational grazing in restricted grazing swards are not yet well understood, and the maximisation of carbohydrates does not fully explain this phenomenon. Our research confirms that intertidal H. univervis seagrass meadows form a crucial resource for dugong survival. These relatively unknown biotopes need therefore more attention in research and conservation programmes.     

Lycopene and preclinical carotid atherosclerosis

Evidence from epidemiological and clinical studies suggests a possible correlation between serum antioxidant levels and cardiovascular disease risk. High plasma concentrations of lycopene have been associated with reduced prevalence of cardiovascular disease. The aim of this study is to compare plasma concentrations of lycopene in subjects with or without ultrasonic evidence of asymptomatic carotid atherosclerosis. One hundred and twenty subjects underwent physical examination, ultrasonic measurement of common carotid artery intima-media thickness and serum profile analysis. Logistic regression methods and analysis of variance were used to determine whether differences existed between participants with or without evidence of carotid atherosclerosis. Of the 120 participants, 58 exhibited evidence of carotid atherosclerosis. Participants with ultrasonic evidence of carotid atherosclerosis exhibited significantly higher serum concentrations of total cholesterol, LDL-cholesterol and triglycerides. In contrast, participants with ultrasonic evidence of carotid atherosclerosis exhibited significantly lower plasma concentrations of lycopene. These data suggest that higher serum levels of lycopene may play a protective role versus cardiovascular diseases, in particular carotid atherosclerosis.     

Field evaluation of efficacy and persistence of an insect vacuum device against the tarnished plant bug (Hemiptera: Miridae) in a day-neutral strawberry field

The efficacy of a vacuuming device to reduce Lygus lineolaris (Palisot de Beauvois) populations was evaluated over 3 yr in a day-neutral strawberry field. Immediately after treatments, a significant reduction of population estimates (by tapping of flower clusters) was observed for adults (75% of the time) and nymphs (50% of the time). Under the same conditions, control (i.e., vacuum turbine off) treatments significantly reduced adult population estimates 25% of the time. Lygus lineolaris tapping samples taken from strawberry plants adjacent to the treated zone did not show significant variations over sampling time, suggesting that no escape behavior occurred. This was supported by adult catches on sticky traps located in zones adjacent to the treated one. Our results suggest that vacuuming had inconsistent effect on tarnished plant bug populations and that L. lineolaris mobility plays a marginal role in the use of this control method.     

Ecological implications of parasites in natural <Emphasis Type="Italic">Daphnia</Emphasis> populations

In natural host populations, parasitism is considered to be omnipresent and to play an important role in shaping host life history and population dynamics. Here, we study parasitism in natural populations of the zooplankton host Daphnia magna investigating their individual and population level effects during a 2-year field study. Our results revealed a rich and highly prevalent community of parasites, with eight endoparasite species (four microsporidia, one amoeba, two bacteria and one nematode) and six epibionts (belonging to five different taxa: Chlorophyta, Bacillariophyceae, Ciliata, Fungi and Rotifera). Several of the endoparasites were associated with a severe overall fecundity reduction of the hosts, while such effects were not seen for epibionts. In particular, infections by Pasteuria ramosa, White Fat Cell Disease and Flabelliforma magnivora were strongly associated with a reduction in overall D. magna fecundity. Across the sampling period, average population fecundity of D. magna was negatively associated with overall infection intensity and total endoparasite richness. Population density of D. magna was negatively correlated to overall endoparasite prevalence and positively correlated with epibiont richness. Finally, the reduction in host fecundity caused by different parasite species was negatively correlated to both parasite prevalence and the length of the time period during which the parasite persisted in the host population. Consistent with epidemiological models, these results indicate that parasite mediated host damages influence the population dynamics of both hosts and parasites.