How optimal life history changes with the community size-spectrum

This paper derives optimal life histories for fishes or other animals in relation to the size spectrum of the ecological community in which they are both predators and prey. Assuming log-linear size-spectra and well known scaling laws for feeding and mortality, we first construct the energetics of the individual. From these we find, using dynamic programming, the optimal allocation of energy between growth and reproduction as well as the trade-off between offspring size and numbers. Optimal strategies were found to be strongly dependent on size spectrum slope. For steep size spectra (numbers declining rapidly with size), determinate growth was optimal and allocation to somatic growth increased rapidly with increasing slope. However, restricting reproduction to a fixed mating season changed optimal allocations to give indeterminate growth approximating a von Bertalanffy trajectory. The optimal offspring size was as small as possible given other restrictions such as newborn starvation mortality. For shallow size spectra, finite optimal maturity size required a decline in fitness for large size or age. All the results are compared with observed size spectra of fish communities to show their consistency and relevance.

Pupil constriction can alter the accuracy of dark room provocative test.

BACKGROUND: Primary angle-closure glaucoma (PACG) is a major cause of visual morbidity in East Asia. Dark-room provocative test (DRPT) has been used to determine which narrow angles have the risk to develop angle closure. However, the accuracy of DRPT might be altered because that after emerging from the dark room, the configuration of the angle is affected by the light of the slit-lamp and the appositionally closed angle reopens. The aim of this study was to examine the pupillary diameter in different light conditions and use it as a parameter to assess the accuracy of dark-room provocative test. METHODS: Patients with suspected primary angle-closure glaucoma undergoing DRPT were recruited. The anterior chamber angle was examined by anterior segment optical coherence tomography under the following conditions: (1) in standard room illumination; (2) after short-term dark-adaptation and (3) after DRPT. Mean values of pupil size and numbers of appositionally closed angle under different conditions were compared. RESULTS: A total of 47 eyes of 47 patients were analyzed. The pupil size after DRPT was smaller than that after short-term dark-adaptation (P < 0.001) and smaller than that in standard room illumination (P = 0.026). The numbers of appositionally closed angles after short-term dark-adaptation were significantly larger than those after DRPT (P < 0.001). There was no significant difference between the numbers of appositionally closed angles in standard room illumination and after DRPT (P = 0.157). CONCLUSIONS: Constriction of pupil size immediately after prolonged dark room provocative test may lead to change in the angle configuration, which may lead to false negative results. We suggest a modified protocol of recording intraocular pressure immediately after DRPT and performing gonioscopy following short-term dark adaptation to improve the accuracy of angle closure assessment.

Fasciola hepatica: Comparative effects of host resistance and parasite intra-specific interactions on size and reproductive histology in flukes from rats infected with isolates differing in triclabendazole sensitivity

The efficacies of putative fasciolicides and vaccines against Fasciola hepatica are frequently monitored in clinical and field trials by determination of fluke egg output in host faeces and by worm counts in the host liver at autopsy. Less often used are parameters based on fluke size and histology, yet these can provide important indications of specific effects on the development of particular germ-line or somatic tissues, especially in relation to the timing and profligacy of egg production. In this study. F. hepatica metacercariae of two distinct isolates, the triclabendazole (TCBZ)-sensitive Cullompton isolate and the TCBZ-resistant Oberon isolate, were administered to rats as single-isolate or mixed-isolate infections. At autopsy 16 weeks later individual adult flukes were counted, measured and the reproductive organs were examined histologically. The degree of development of the testis tubules in each fluke was represented by a numerical score, based on the proportion of the histological section profiles occupied by testis tissue. The level of anti-F. hepatica antibody in the serum of each rat was determined by ELISA. It was found that Cullompton flukes were significantly larger than Oberon flukes, and that significantly more Cullompton metacercariae developed to adults than Oberon metacercariae. The Cullompton flukes showed histological evidence of aspermy and spermatogenic arrest, which was reflected in quantitatively reduced testicular development, as compared with the Oberon isolate. In Cullompton flukes, parthenogenetic egg development is implied. The size of Cullompton and Oberon flukes was significantly related to the number of adult flukes recovered, to the number of metacercariae administered, and to the percentage success of infection. The testis development score in both isolates was significantly related to the number of adult flukes recovered but not to the number of metacercariae administered, or to the percentage success of infection. Fluke size was positively related to testis score for both isolates, and a significant negative relationship was found between percentage success of infection and metacercarial dose. The results are interpreted in terms of differing interactions between various numbers of young flukes and host immunity during invasion of and migration in the hepatic parenchyma, and of fluke intra-specific (possibly pheromonal) stimulatory effects in the final stages of development, within the host bile ducts. No significant relationships were found between host antibody levels and fluke size or testis score. False positive serological reactions were found in some rats that had been infected, but found to harbour no flukes at autopsy. Clearly the act of eliminating the flukes involved generation of an immune response. (C) 2011 Elsevier B.V. All rights reserved.