Some 7800 km have been surveyed for Cabomba, but it was found to be very abundant in some very specific environments, which are, however, very extended in the province of Corrientes (Fig. 1), and in isolated locations in Chaco province (bordering Corrientes), and central Paraguay. Mostly, but no exclusively, clear and/or black, deep waters. 

Two varieties were found in Argentina, C. caroliniana var. caroliniana and var. flavida, determined by the colour of the flowers. The plant was sometimes mixed with Egeria, Myriophyllum, Chara, and specially Utricularia. But it was frequently found in dense, pure stands. 

Associated fauna. Some of the organisms associated to fanwort have been found in the field as a result of direct observation in the plant’s environment, or close inspection onboard the boat or along the watercourse banks. Such has been the case of the relatively large and conspicuous insects like caterpillars or caddisflies. However, most organisms appeared after laborious inspection in water filled white tubs of the samples brought back to the laboratory, samples actually planted in the 26-litre tubs described above, and left to “stew” for several days, and Berlese style funnels and net bags.  

The following phytophages of interest were observed feeding on fanwort: 

1)      A click beetle that feeds on shoots and leaves (Iberá lake, Corrientes prov.). This 10-mm beetle is completely covered in an air bubble when submerged (Fig. 5), except for its mouthparts and last leg articles (Fig. 6 and 7). It is a true aquatic insect, that does not emerge to replenish its air bubble, indicating oxygen exchange occurs at the water/bubble interface (plastron respiration). The damage observed on Cabomba consists on clipping and defoliation.

2)      The weevil Hydrotimetes natans feeds on the plant. Adults feed on foliage, and the larvae mine the stems. The pupa develops in a kind of air tight cocoon attached to the stems. It has been collected at several locations in the province of Corrientes. As the preceding beetle, it is a true swimmer/diver that can live under water for hours on end by holding a permanent air bubble surrounding its abdominal sternites.

3)      An aquatic caterpillar [genus Paracles (?)] was collected at several locations. This caterpillar causes heavy defoliation on Cabomba (Fig. 11), and seems to prefer the leaves near the terminal shoots. It feeds underwater keeping air bubbles amidst the short, orange hairs on its dorsum. Its cocoon is also aquatic, resembling a canoe, in which only the silk tufts on the ends remain dry and above the water surface. The adult, a 25-mm brown moth (Fig. 13), stretches it wings on the floating cocoon upon emergence.  It can feed on several aquatic weeds, but preliminary tests suggest it needs to feed on Cabomba to molt and complete its development.

4)      All these organisms are fully aquatic, and can swim and remain under water indefinitely. An exception is a large (up to 3 mm), black aphid (Fig. 14), that has poor aquatic performance, feeding on emergent stems.

References Cited 

Mackey, A. P. 1996. Cabomba (Cabomba spp.) in Queensland. Pest status review series, Department of Natural Resources and Mines, Qld, Australia.

Orgaard, M. 1991. The genus Cabomba (Cabombaceae) - a taxonomic study. Nord. J. Bot. 11: 179-203.

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Weevil feeding on Cabomba stems.	Weevil larva feeding on Cabomba stems.	Aquatic moth feeding on Cabomba leaves
Click-beetle feeding on Cabomba leaves.	Stream overgrown with C. caroliniana var.	Tanks with different aquatic plant species for specificity tests.
Leaves and flowers of Cabomba carolineana