The rain forests of South-East Asia represent a biodiversity hotspot of terrestrial leeches, but we have only fragmentary and often anecdotal information on this component of tropical communities. To address the foraging tactics of terrestrial leeches, we studied the vertical distribution of Haemadipsa picta on foliage in a Bornean tropical rain forest. We investigated the links between leech body length and the above-ground height of their ambush positions under natural conditions and in a choice experiment performed under semi-natural conditions. We studied 167 leeches, which varied considerably with respect to body length (4–29 mm). On average, the leeches ambushed at lower heights under natural conditions than under experimental conditions (47.7 cm vs. 67.5 cm), though the heights of ambush positions overlapped considerably. Leeches that chose higher ambush positions under natural conditions consistently chose higher ambush positions in the experiment (Pearson r = 0.29). Under both natural and experimental conditions, leech body length was positively correlated with the height of ambush positions (Pearson r = 0.48); on average, a 1-mm increase in body length corresponded to a 2–3 cm higher ambush position. Our findings suggest that H. picta individuals actively choose hunting locations according to their above-ground height, shifting their ambush sites over ontogeny to higher foliage. We hypothesize that growing leeches might target different prey following ontogenetic shifts in the foraging optima, ultimately decreasing intraspecific competition.
Phytochemical investigation of Marsypopetalum modestum (Annonaceae) led to the isolation of a new phenylpropanoid glycoside, lyciumphenylpropanoid B (10), along with nine known compounds (1-9) from an aqueous methanolic extract of the stem. Most compounds are reported from this genus for the first time. The structures of the isolated compounds were elucidated using spectroscopic methods including NMR spectroscopy, high-resolution mass spectrometry, and quantum chemical electronic circular dichroism (ECD) calculations. Cytotoxic and antitubercular activities of several isolated compounds were evaluated. Dipyrithione (1) displayed anti-mycobacterial (MIC = 0.23 μM) and cytotoxic (IC50 = 0.8 μM in Hep G2 cells; 4.1 μM in HCT 116 cells) activities. Kelampayoside A (8) showed moderate cytotoxic activity against cancer cells.
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