Cercariae of Cotylurus flabelliformis (Faust, 1917) were individually tested in 6 experiments for evidence of chemoattraction to snail hosts, host-speeificity, and rate of dispersal. Five species of snails were tested: Lymnaea stagnalis appressa Say, 1821, Stagnatola eludes (Say, 1821), Physella gyrina (Say, 1821), Planorbella trivnlvis (Say, 1817), and Oxyloma retusum (Lea, 1834). The data substantiate that cercariae of C. flabelliformis have a chemo-positive attraction to undetermined diffusable substances from snails, show host-specificity, and do not attack the snail that produced them. Cercarial response time was significantly influenced by cercarial age (post-emergence), and duration of presence of snails. Newly emerged cercariae were most consistently chemo-positive to L. stagnalis and quickly located all snail species except the unnatural host O. retusum. Tests of 121 cercariae proved statistically significant in showing preferences for snail hosts. Cercarial dispersal experiments showed that C. flabelliformis cercariae can disperse rapidly but few located and penetrated lab-reared S. eludes at distances up to 1.2 m. The results are consistent with other studies which indicate that chemical gradients are used by cercariae to locate slow moving hosts and that cercariae must come into close proximity of snails before attraction occurs. The significance of these observations to the distribution of C. flabelliformis in the molluscan population is discussed.
The article looks into the competition of the absolute and relative tense in the dependent clauses introduced by adjectival predicates with the meaning of evaluation (bylo + adjective). In the linguistic literature, it was so far argued that these clauses can only have relative tense if an evaluator expressed by a noun or pronoun in the dative is (or, may be) included. However, on the basis of corpus analysis, the author of the article found out that the relative tense in these sentences occur in many other cases as well.
Quadratic relationship between the age of a tea leaf and the net photosynthetic rate (PN) has been found. A progressive increase in PN was recorded for four months. Then the PN slowly declined, yet even seven-month-old tea leaves sustained a low PN. In a tea shoot, the PN increased from the first leaf onwards. Besides the physiological maturity and proximity, photon flux density (PFD) played an important role in reducing the PN. The tea leaf PN was influenced by cultivation procedures which in turn disrupted the quantum of PFD transmitted through the canopy. and R. Raj Kumar, L. Manivel, S. Marimuthu.
The effects of condensed tannins (CT) extracted from seven forages on the motility of the economically important nematode, Trichostrongylus colubriformis (Giles, 1892), were evaluated by using a larval migration inhibition (I.MI) assay. The assay involved incubation of third stage (L3) exsheathed T. colubriformis larvae with CT extracted from Lotus pedunculatus, Lotus corniculatus, sulla (Hedysarum coronorium), sainfoin (Onobrychis viciifolia), Dorycnium rectum, Dorycnium pentaphyllum and dock (Rumex abtusifolius) and measurement of larval migration through nylon mesh with a 20pm pore size. At 100 pg ml'1, CT from L. pedunculatus, L. corniculatus, sulla, sainfoin, D. rectum, D. pentaphyllum and dock inhibited 20%, 10%, 15%, 25%, 28%, 32% and 27% of the larvae, respectively from passing through the sieves compared to controls (no CT added). At 1000 pg CT ml'1, CT purified from D. pentaphyllum had the highest inhibitory activity (63%) against 1-month old larvae followed by sainfoin (59%), L. pedunculatus (57%), D. rectum (53%), dock (50%), sulla (40%) and L. corniculatus (37%). Seven-month old larvae were more sensitive to the action of CT than 1-month old larvae (P < 0.001). Addition of 2 pg polyethylene glycol ([PHG] per pg CT; to remove the effect of'CT) eliminated 81-93% of the CT activity (P < 0.001) compared to incubations without PEG. The impact of CT on larval migration suggests a possible role for these plants in ruminant diets as a means to reduce dependence upon proprietary anthelmintics.