FISHERY BULLETIN: VOL 76. NO. 3 



Diodon niidifrons Jenkin?, 1904:488-489 (Hawaii I. 

 Diodun armiUatus Whitley 1933:107-108, pi. 12, 



15 (Australia). 

 Diodon totara Curtiss 1938:132-133 (Tahiti). 



Diagnosis. — A slender-bodied D/oc/on, head width 

 0.29-0.42, peduncle length 0.14-0.21. Caudal 

 peduncle armed dorsally with short spines. Body 

 spines short to long, slender, and numerous. S-D 

 spines 15-19, S-A spines 14-19. Pectoral axil 

 spines 0.13-0.19, longest on body. A short, fixed 

 tribase spine immediately above gill opening. D 

 14-17. A 14-16, P 21-25. Nasal tentacle with a pair 

 of lateral openings. No barbels or fleshy tentacles 

 on body. No short, downward-pointing spine below 

 the anterior border of the eye. Dorsal and anal fins 

 rounded. Color pattern dominated by small 

 (<pupil) dark spots dorsally and laterally, these 

 extend onto all fins in adults. A dark gular band 

 starting below the eyes and continuing under the 

 lower jaw, often with a branch extending dorsally 

 between eye and gill opening. 



Description . — (34 specimens) D 14-17, A 14-16, the 

 first two rays in each unbranched; P 21-25. Head 

 width 0.29-0.42 (.r = 0.33; SD = 0.03), body width 

 0.30-0.51 ix = 0.37; SD = 0.04), peduncle length 

 0.14-0.21 ix = 0.17; SD = 0.02), eye 0.05-0.14 

 ( X = 0.08; SD = 0.02). Dorsal and anal fins 

 rounded. Nasal tentacles with a pair of lateral 

 openings. 



S-D spines 15-19, S-A spines 14-19, about 15 

 spine rows over the dorsum between pectoral fin 

 bases, about 25 spine rows over the ventrum be- 

 tween pectoral fin bases. Five frontal spines. 

 Longest frontal spine 0.06-0.12 (.v = 0.09; 

 SD - 0.02), pectoral axil spines 0.13-0.19 

 (.r = 0.15; SD = 0.02). Pectoral axil spines the 

 longest on the body, 0.45-0.78 ix = 0.58; 

 SD = 0.09) in frontal spines. Spines short to long, 

 and slender. Dorsal spines, other than those dor- 

 solateral spines from over the eye to over pectoral 

 fin, are approximately equal and of about the same 

 length as the ventral spines. The dorsolateral 

 spines immediately above the pectoral fin may be 

 nearly as long as pectoral axil spines. Spines on 

 peduncle short (ca. 2 in frontal spine) and shaft 

 extension not very large (ca. 2.5 in shaft). Shaft 

 extension on other spines reduced, never more 

 than 167f of shaft length. Subdermal bases mod- 

 erate to very long. In ventral and lateral spines the 

 bases may be 1.5 x or more the length of the shaft. 

 In an ovoid area extending from the interorbital to 



546 



the occipit the spines may be greatly reduced or 

 even embedded, particularly in large individuals. 

 Caudal peduncle with one to three dorsolateral 

 pairs of relatively small spines and one or more 

 unpaired spines located either medially or dor- 

 solaterally. Usually one or two ventrolateral 

 spines on peduncle. A short, fixed tribase spine 

 immediately above the gill opening and a second 

 slightly posterior to it (above the pectoral base), 

 both may be embedded. Three short, flat spines 

 with broad lateral bases form the anterior border 

 of the gill opening. No snout spine. 



No barbels or fleshy tentacles. 



Dorsally in preserved specimens, the ground 

 color is light grey to dark tan grading to white 

 ventrally. Dorsal and lateral surfaces marked 

 with dark brown to black round spots (<pupil). 

 The spots not generally associated with spine 

 axils. Fins unspotted in small specimens ( <50 

 mm), but all fins become covered with spots in 

 adults. The anal fin is not marked except by a 

 dusky area at its base, and in very large individu- 

 als by spots. 



A dark gular band extends from the eye down 

 and forward generally paralleling the ventral out- 

 line of the lower jaw. Often a branch of this band 

 extends dorsally between the eye and gill opening. 

 These bands may be absent in pelagic specimens. 



In life the coloration is essentially as described 

 above, but there may be dorsal blotches ( similar to 

 those of D. holocanthus). These blotches can 

 rapidly appear and disappear. The blotches are 

 particularly evident during feeding but disappear 

 immediately if the fish is disturbed, e.g., by the 

 approach of a diver. I have never seen these 

 blotches retained in a preserved specimen (for 

 examples of these blotches see Clark and Gohar 

 1953 and Bagnis et al. 1972:225). 



The largest specimen examined was 571 mm, 

 but much larger examples have been reported 

 (e.g., 900 mm, de Beaufort 1962). 



Eggs, larvae, and pelagic Juvenile stages. — The 

 identification of the eggs and larvae described 

 here as D. hystrix is tentative because the larvae 

 have not been reared through metamorphosis. 

 Identification is based on the close similarity of 

 these eggs and larvae to those of D. holocanthus 

 and the fact that D. hystrix and D. holocanth us are 

 the only diodontids that commonly occur inshore 

 in Hawaiian waters. Diodon eydouxii has not been 

 taken closer than 30 mi from shore around 

 Hawaii, and Chiloniycterus affinis is very rare 



