Alterations in Heart Rate Physiology of the Blackworm (Lumbriculus variegatus) after Treatment with Extracts from Various Hosta varieties.

Abstract

Agriculture in the United States is a recognized national resource but it can be threatened by ecological disturbances causing potential harm to the agricultural industry. Changes in soil microfloral structure could cause disruptions in soil ecosystems. Hosta plants are known producers of inhibitory allelopathic chemicals that disrupt the growth of competing organisms. The blackworm-annelid is a test model organism for the inhibitory effects of allelochemicals. Previous studies reported that the variety Guacamole (G) was a strong producer of allelochemicals such as phenols and other flavonoids antioxidants. Fragrant Bouquet (FB) produced a lower level of allelochemicals when assayed for seed germination. It is hypothesized that Hosta extracts will have inhibitory physiological effect on these worms and follow a concentration gradient for survival correlated with altered pulse rates. Aqueous extracts of Hosta leaves were made and divided by concentration, (full, half, and quarter strength). Physiological effects were measured by observing pulse rates/beats of blackworms after incubation for 15 or 7.5 minutes (BPM). Results were compared to the base-line rates of blackworms incubated in spring water. Blackworms exposed to full strength G extract died exhibiting hemorrhaging and aneurysms of the dorsal blood vessel (DBV). Blood was observed in the coelomic cavity. Lower extract concentrations resulted in higher survival rates but worms still showed increased pulse rates. Pulse rates were higher than baseline controls, 16.8 BPM. Half strength induced 36.7 BPM, while quarter strength induced 30.6 BPM. Worms treated with FB extract showed decreased mortality. Pulse rates for quarter strength FB were lower than quarter strength G, approaching control rates. These data reinforce the hypothesis that G and FB extracts differ in their levels of mortality, G being most lethal. Between varieties a concentration gradient exists, that is, both mortality and pulse rate decrease with dose. Lumbriculus variegatus is shown here to be a viable model organism to assess the allelopathic properties of Hosta varieties. Future research will assess allelopathic properties of other Hosta varieties in a search for a naturally occurring, plant-derived biocide.