Tiny Dragons in Bromeliad Pools

by Joseph DeSisto

In the last week, three amazing new Central American invertebrates were described, in two publications. These species, one dragonfly and two oligochaete worms, are interesting primarily because of where they were found: in the water-holding urn of bromeliad plants.

Bromeliads are flowering plants in the family Bromeliaceae, and include more than 3,000 mostly tropical species. The family includes such disparate species as the ground-dwelling pineapple (Ananas comosus) and the epiphytic Spanish “moss” (Tillandsia usneoides). Many epiphytic bromeliads, those species that live on the surfaces of trees, are shaped so as to hold pools of water between their leaves.

A water-holding bromeliad plant in the genus Werauhia. Photo by Dick Culbert, licensed under CC BY 2.0.

A water-holding bromeliad plant in the genus Werauhia. Photo by Dick Culbert, licensed under CC BY 2.0.

This makes them important components of the rainforest canopy community: although the rainforest floor may be perpetually moist, higher up the air dries, and permanent sources of standing water may be rare. As a result, many species dwell in the bromeliads’ urns, ranging from microscopic ostracods to salamanders, tree frogs, and even a species of Jamaican crab.

To this list Haber et al. (2015) add a new species of dragonfly, a member of the widespread family Libellulidae. Although adult dragonflies are aerial predators, their larvae are aquatic, and so their parents lay eggs in bromeliad pools. Of course, the larvae are themselves predatory, so what are they eating? Apparently, lots of other species live in bromeliad pools, including mosquito larvae, which provide the dragons with plenty to eat.

A second paper, Schmelz et al. (2015) includes a review of the microdrile oligochaete (tiny annelid) worms found in bromeliad pools in a Honduran cloud forest. It turns out that in this forest, at least six microscopic annelid worms are found in bromeliads, among them two new species in the family Enchytraeidae. This family also includes a variety of soil-dwelling species, which behave essentially like tiny earthworms, but in bromeliad pools they make their living by feeding on decaying plant matter that somehow makes its way into the water.

From worms and crabs to dragonflies and frogs, the miniature ecosystem is diverse and vibrant, and clearly there is much still to be discovered.

Cited:

Haber, W.A., D.L. Wagner, and C. de la Rosa. 2015. A new species of Erythrodiplax breeding in bromeliads in Costa Rica (Odonata: Libellulidae). Zootaxa 3947(3): 386-396.

Schmelz, R.M., M. Jocque, and R. Collado. 2015. Microdrile Oligochaeta in bromeliad pools of a Honduran cloud forest. Zootaxa 3947(4): 508-526.

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