EPOW - Ecology Picture of the Week

Leech in the Night

Leech, poss. Tiger Leech (Haemadipsa sp., cf. picta), Family Haemadipsidae
Tanjung Puting National Park, Borneo, Indonesia

Explanation:  Bearing headlamps during an exploratory night hike through lowland tropical forests of Tanjung Puting National Park in southern Borneo, Indonesia, we happened upon a wonderful nocturnal invertebrate world.  On the edge of some decaying tree bark resided a microcosm of the microworld.  

Look closely at the above photo.  The center star of the scene is indeed the leech, possibly a Tiger Leech.  Some sources note that at least 9 species of leeches occur in Borneo and provide ways to prevent or remove them should they give you a nice leech-hug. 

But also look at the photo again.  Did you notice the two ants, to the upper left and lower right of the leech?  And the spider at left, and the one just under the bark edge at the bottom?  
   

Little is truly understood about the basic and functional ecology of leeches, including on Borneo (Jambari et al. 2022), including their interactions with other invertebrate fauna of the forest.  

One study (Drinkwater et al. 2020) suggests that "blood-feeding terrestrial leeches," including Tiger Leeches, can serve as useful ecological indicators of the degree of forest system degradation, and also -- so interestingly -- as a source of mammal DNA for monitoring mammal species (in the way that species DNA can be detected in some spider webs)!  

Tiger Leeches on Borneo specifically could be useful as indicator taxa for biomonitoring (Nelaballi et al. 2022), as the species has a narrow distribution in lower elevation wet tropical forests and thus may be sensitive to lower levels of soil moisture.  Lower abundance of the leeches, if monitored over time, could indicate trends in aridity and drying of soils and vegetation, and thus potential adverse impacts on the broader biota associated with moist tropical vegetation.

So, hail to the utility of the "giant" leeches of tropical forests!  

    
  
    
Information:
     Drinkwater, R., J. Williamson, T. Swinfield, N. J. Deere, M. J. Struebig, E. L. Clare, D. Coomes, and S. J. Rossiter.  2020.  Occurrence of blood-feeding terrestrial leeches (Haemadipsidae) in a degraded forest ecosystem and their potential as ecological indicators.  bioTROPICA 52(2):302-312. https://doi.org/10.1111/btp.12686.
     Jambari, A., M. Nakabayashi, S. Numata, and T. Hosaka.  2022.  Spatio-temporal patterns in the abundance of active terrestrial leeches in a Malaysian rainforest.  bioTROPICA 54(4):969-978. https://doi.org/10.1111/btp.13120.
     Nelaballi, S., B. J. Finkel, A. B. Bernard, G. R. Estrada, E. Setiawan, T. M. Setia, T. W. Susanto, R. Rhanda, Surya, Jakaria, D. Andika, S. Lemoine, S. M. Jaffe, E. J. Barrow, Ž. Justinek, H. U. Wittmer, and A. J. Marshall.  2022.  Impacts of abiotic and biotic factors on terrestrial leeches in Indonesian Borneo.  bioTROPICA 54(5):1238-1247. https://doi.org/10.1111/btp.13146.