240 



These crustaceans externally resemble gammarids. The body is com- 

 pact, most often with small, nonbulging head. The eyes are usually dis- 

 tinct and located laterally on the head, occupying 1/5-1/2 the lateral 

 surface; in some cases they are absent or comprise individual rows of 

 ocelli. In antennae I the 1st segment of the flagellum is flattened, spat- 

 ulate, and bears two longitudinal bands of sensory setae on the inner 

 surface; one-two highly reduced, successive segments present apically in 

 the flagellum, which are difficult to discern in adults but well defined in 

 younger individuals. Antennae II are five- to eight-segmented, in females 

 shorter, in males longer than antennae I or equal to them. The mandibles 

 have a long palp, its 3rd segment longer than the 2nd; the masticatory 

 process has a flat oval or rectangular apex covered with tubercles and 

 bordered with denticles. Maxillae I have a small oval inner lobe. The 

 2nd segment of pereopods I-II is not broadened (except in V. robusta). 

 Pereopods VII have a full complement of segments, their 2nd segment in 

 all species (except V. chuni) considerably shorter than the remaining part 

 of the leg. The epimeral plates have a rounded edge. The basipodite of 

 uropods III may be longer or (rarely) shorter than the rami; sometimes it 

 is equal to them in length. The telson does not extend beyond the middle 

 of the basipodite of uropods III. 



Type species: V7^///a pewn/ Milne-Edwards, 1830. 



Most of the species of Vibilia are associated with swarms of salps. 

 They are often found in the body cavity of salps, although on being 

 200 alarmed when the salps are caught, they usually exit from the host. 

 However, according to our observations, when put in an aquarium with 

 live salps, they moved inside them and rarely emerged from their shelter. 

 Vibilia species use salps as a source for food; they select some of the 

 salp's catch concentrating directly at the entrance into the esophagus or 

 branchial cord, along which the food particles filtered by the salp are 

 passed over to the esophagus (Madin and Harbison, 1977). 



The salps also have a less important role in the life cycle of Vibilia, 

 as shelter for the young crustaceans. Laval (1963) observed in an exper- 

 iment how the female transfers larvae from the brood chamber to the 

 surface of the salp by means of the specialized pereopods VII. At this 

 stage the larvae lack pereopods and are not capable of independent active 

 swimming. They live in salps up to complete development of the natatory 

 legs. Obviously, this is the reason why most often females and young 

 and rarely the males are caught along with salps. Laval also noticed the 

 feeding of early larvae of. Vibilia on the tissues of the host; more adult 

 crustaceans feed only on the suspension matter filtered by the salps. There 

 is a definite link between the structure of antennae I and the semiparasitic 

 mode of life of Vibilia; the distal part of the flagellum of antennae I was 



