Abstract Detail



Ecology

Nyandwi, Alphonse [1], Eckardt , Winnie [2], DeVore, Melanie [3].

Stinging trichome density and morphology of three nettle species reflect mountain gorilla feeding behavior.

Plants have developed numerous mechanisms against herbivory. One of the most interesting mechanical defenses are stinging trichomes. Unlike smaller trichomes, which deter insects, the larger, biomineralized, stinging trichomes in Urticeaeae defend plants from mammals. When the trichome tip breaks off, it pierces and enters the skin and injects irritants causing and immediate sensation of pain.  The herbivore will immediately cease consuming the plant.  However, there are herbivores which have successfully learned how to disarm nettles. The Volcanoes National Park in Rwanda is known for its dense terrestrial vegetation and has been described as a “salad bowl” for several sympatric large folivores, including the endangered mountain gorilla (Gorilla beringei beringei). Mountain gorillas diet includes three stinging nettle species including Laportea alatipes (0.29%), Urtica massaica (0.1%), and Girardinia bullosa (<0.1%). We investigated the link between the importance (proportion) of these stinging nettles in mountain gorilla diet and their level of defense through assessing the trichome density, length, and glandular base length from each plant organ of 15 specimens per nettle species which were photographed with a scale ruler under a microscope. We also videotaped eight mountain gorillas consuming L. alatipes to examine adapted feeding techniques to cope with stinging trichomes. Using ANOVA, we found that L. alatipes, which is consumed most frequently from the three study nettles, had a significantly higher stinging trichome density compared to U. massaica and G. bullosa. However, the length of stinging trichomes and glandular bases containing irritating secrets were significantly smaller in L. alatipes and U. massaica than in G. bullosa from which gorillas almost exclusively avoid consuming above-ground organs covered with trichomes. This suggests that larger stinging trichomes and secretory glandular bases offer a more effective defense against mountain gorillas than increased trichome density. Our findings also show that trichome density of L. alatipes tended to be lower on bottom leaves and the bottom section of stems from where gorillas start stripping leaves off the stem, a process that damages trichomes on leaves and the stem before ingestion and mastication and thus may be a specific feeding technique adapted by this gorilla population.


1 - University of Rwanda, Butare, Rwanda
2 - The Dian Fossey Gorilla Fund, Musanze, Rwanda
3 - Georgia College & State University, Biological And Environmental Sciences, Campus Box 081, Milledgeville, GA, 31061, United States

Keywords:
none specified

Presentation Type: Poster Time and date to be determined
Number: PEC007
Abstract ID:471
Candidate for Awards:None


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