Studies on the behaviour, and development in fish, ofSubtriquetra subtriquetra: a uniquely free-living pentastomid larva from a crocodilian

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Abstract
SUMMARY: The primary larva of the porocephalid pentastomidSubtriquetra subtriquetra, which infects the nasopharynx ofCaiman sclerops, is uniquely free-living. Eggs hatch within the nasal passages and the emergent larvae can remain infective to the fish intermediate host for 4–5 days. During this period larvae exhibit very stereotyped behaviour, alternating between a characteristic stationary ‘fishing’ posture and very brief periods of movement. Larval activity increases significantly at 3 days, probably effecting dispersal to a more favourable site for host invasion. Host location is passive and invading larvae penetrate to the swim-bladder where subsequent larval development, which involves 7 moults, occurs. All 8 larval stages are freely mobile in the swim-bladder and possess hooks. Sensilla, disposed in characteristic patterns, are present throughout development, increasing in number to the infective stage; the majority of sensilla are located on sensory papillae.