FISHERY BULLETIN: VOL. 76, NO. 3 



Figure 8. — Distribution of Diodon eydouxii (triangles) and Diodon hystnx (circles). Solid symbols denote specimens examined by me; 

 hollow symbols denote acceptable literature records, photographs, or specimens examined for me by colleagues. Some overlapping re- 

 cords omitted. 



spinosissimus Cuvier (see discussion under D. 

 hystrix). Le Danois (1959), without comment, in- 

 correctly placed D. eydouxii in synonomy with D. 

 holocanthus. 



The above citations, and those of Troschel ( 1847 ) 

 and Dumeril (1855) which were essentially re- 

 views of Brissout de Barneville's 1846 paper, con- 

 stitute the entire literature on D. eydouxii. 



Diodon eydouxii has undoubtedly been confused 

 in the past with the similar D. hystrix. Adapta- 

 tions to pelagic life by D. eydouxii include a 

 lighter, smaller, and more fusiform body com- 

 pared with D. hystrix. The blue color and falcate 

 dorsal and anal fins are also probable adaptations 

 to the pelagic environment. Aside from these 

 characters, D. eydouxii differs from D. hystrix 

 primarily in its higher dorsal^ and anal fin ray 

 counts and lower pectoral fin ray counts. Diodon 

 hystrix juveniles are pelagic up to a rather large 

 size, and it is tempting to speculate that D. 

 eydouxii evolved from this pelagic phase. 



All captures of D. eydouxii have been at sea 

 (except for one found dead in a South African har- 

 bor). Most captures were made under night-lights, 

 and field notes occasionally mention large schools 

 of Diodon under the light. Occasional (mostly 



544 



small) specimens have been taken in plankton, 

 neuston, or midwater trawl hauls. 



As a pelagic member of an otherwise slow- 

 swimming, inshore family apparently specialized 

 to feed on heavy-shelled reef animals (e.g., Ran- 

 dall 1967; Hobson 1974), D. eydouxii is unusual. 

 However, a well-developed but relatively un- 

 specialized pelagic stage is present at least in D. 

 hystrix and D. holocanthus. The tetraodontiform 

 fishes, none of which are noted for a combination of 

 rapid and sustained swimming ability and many 

 of which are specialized for feeding on heavy- 

 shelled benthic invertebrates, have a number of 

 pelagic representatives, e.g., Lagocephalus 

 lagocephalus (Tetraodontidae) and Canthidermis 

 maculatus (Balistidae). In addition, many other 

 species of Tetraodontiformes have pelagic juvenile 

 stages of moderate to long duration. At least 16 of 

 the 22 tetraodontiform genera known to occur in 

 Hawaii, e.g., have an extended pelagic life history 

 stage (no information is available for the other six 

 genera — pers. observ.). The extremely specialized 

 Molidae, a totally pelagic tetraodontiform family, 

 have retained a beaklike jaw structure similar to 

 that of diodontids and tetraodontids. The utility of 

 such jaws in the pelagic environment where the 



