NOTE Vidal and Halmovici: Parasites in rhynchoteuthion squid paralarvae 



403 



a nematode (Nematoda) and a copepod (Arthropoda: 

 Crustacea: Siphonostomatoida). About 50 coccidians 

 (Aggregata sp. ) were found distributed along the cae- 

 cum wall of a 7.8-mm-ML paralarva collected in win- 

 ter. Because the paralarva was preserved in glycerin 

 for several months, taxonomic details of the para- 

 sites were not very clear. Cyst capsules (sporocystes) 

 varied in size from 11 to 17 |.im. However, the de- 

 tailed structures inside the capsules were obscure 

 and no certainty could be attained about the pres- 

 ence of sporozooites; hence this protozoan was as- 

 signed to the genus Aggregata. The observed para- 

 sites may have been in a very early stage of develop- 

 ment and if the capsules actually represent sporo- 

 cystes they were unusual because only 1 or 2 were 

 present inside an amorphous oocyst mass (Hoch- 

 bergM. These parasites are deposited at the Santa 

 Barbara Museum of Natural History. 



Six/, argentinus paralarvae (2.2-6.7 mm ML) from 

 autumn, winter, and spring surveys contained 1-3 

 didymozoid metacercariae, probably type Monili- 

 caecum. The body dimensions of the parasites ranged 

 from 140 to 200 |am and because of their size and the 

 absence of testicular anlagen, they appeared to be 

 recently hatched. A single trematode attached to the 

 caecum wall was found in the smallest paralarva. 

 Three parasites were found in the largest paralarva, 

 two attached to the stomach wall and one near the 

 buccal mass. In the other paralarvae, the parasites 

 were found attached to the caecum wall. Data on 

 prevalence and mean intensity of infestation of dif- 

 ferent paralarval types and surveys of didymozoids 



' Hochberg. F. G. 1997. Santa Barbara Museum of Natural 

 History, 2559 Puesta del Sol Road, Santa Barbara, CA 

 93105. Personal commun. 



are presented in Table 1. We found a single (nematode 

 attached to the caecum wall of a 7.0-mm-ML rhyncho- 

 teuthion from the spring sample. The copepod para- 

 site was located on the caecum wall of a 38.0-mm-ML 

 juvenile obtained in spring. The copepod was identi- 

 fied as an adult male of Metacaligus uruguayensis 

 ( Siphonostomatoida: Caligidae ) ( Ho and Bashirullah, 

 1977). Illex argentinus is a newly recorded host for 

 M. uruguayensis. 



In the summer of 1990, didymozoid metacercariae 

 were found in "type A" rhynchoteuthions from 2.0 to 

 5.0 mm ML. Prevalence was 729f and the mean in- 

 tensity of infestation was 3.5 (Table 1). All were at- 

 tached to the caecum or stomach walls, except for 

 three parasites attached to the inner wall of the 

 mantle and two others to the caecum wall of a single 

 paralarva (3.6 mm ML). 



Parasites were not found in "type B" rhyncho- 

 teuthions. However, only four paralarvae of this type 

 were examined. 



Discussion 



Illex argentinus first acquire didymozoid metacer- 

 cariae as small rhynchoteuthions. Hatchlings typi- 

 cally are found off southern Brazil at the outer shelf 

 and slope in tropical and subtropical waters (Vidal 

 and Haimovici, 1997). The infestation may be related 

 to the fact that paralarvae are distributed mainly in 

 tropical waters, where cystophorous cercariae may 

 be abundant and not necessarily because the 

 paralarvae are eating infected intermediate hosts. 

 Crustacean prey were not found in the digestive 

 tracts of rhynchoteuthions smaller than 3.7 mm ML 

 (Vidal and Haimovici, 1998). However, paralarvae 



