The malaria vector, Anopheles gambiae s.l. oviposits both on standing water and hydrated mud surrounding the temporary pools comprising typical larval habitats. A question that arises is whether larvae eclosing above the waterline have sufficient mobility to reach nearby standing water. A related question is whether developing larvae have the capacity to move back to standing water after being displaced from a pool by mechanical disturbance by, e.g., auto tires or cattle passing through the puddle. Two forms of locomotion were documented by direct behavioral observations of first and fourth instar larvae field-collected at Kisian, Kenya and placed on hydrated mud in the laboratory. The first was "tail-lashing," the same series of maneuvers used for normal swimming and which result in tailward displacement. When the film of water around a larva was insufficient to allow tail lashing, larvae switched to a form of headward displacement ("caterpillaring"), whereby a single wave of slight elevation of individual body segments progressed from the posterior abdomen to the head. The body moved forward by about one head-length each cycle. Caterpillaring is a slow form of locomotion; however, some first instar larvae were observed to travel more than 20 body lengths in 15 min. Collectively, these data suggest that An. gambiae larvae can be sufficiently mobile on hydrated mud to have a reasonable probability of reaching nearby standing water. This knowledge should prove useful to interpretations of other aspects of the biology of this vector, e.g., ovipositional site selection.
Species 1: Diptera Culicidae Anopheles gambiae (malaria mosquito)
Keywords: malaria mosquito
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