L I B R.ARY OF THL U N IVLRSITY Of 1LLI NOI5 590-S FI V.34 BIOLOGY Return this book on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. University of Illinois Library DEC L161— O-1096 14" FIELDIANA . ZOOLOGY Published by CHICAGO NATURAL HISTORY MUSEUM Volume 34 JULY 8, 1953 No. 11 A NEW FISH FROM NORTH BORNEO Genus Tetraodon ^ ROBERT F. INGER ASSISTANT CURATOR, DIVISION OF FISHES The Borneo Zoological Expedition (1950) of Chicago Natural History Museum obtained what appears to be a new species of Tetraodontidae. The new form was collected in the drainage of the Kretam Kechil River, which flows into Dewhurst Bay on the north- east coast of Borneo about 35 miles southeast of Sandakan. This species is common in brackish water, occurring near the banks of the larger streams, in the nipa palm and mangrove swamps fringing them, and in the lower reaches of the smaller fresh-water tributaries near the upper limits of tidal water. Tetraodon kretamensis sp. nov. Type. — Chicago Natural History Museum no. 51558, from the Pinang River, a tributary of the Kretam Kechil River, Kinabatan- gan District, East Coast Residency, North Borneo. Collected May 10, 1950, by Robert F. Inger. Description of type. — Body oblong, cylindrical anteriorly, last third of trunk slightly compressed; dorsal profile rising steeply to interorbital, more gradually to point above end of pectoral, sloping downward to center of caudal peduncle, concave above peduncle; ventral profile sloping steeply from mouth to below hind margin of orbit, deepest opposite base of pectoral; body broadest just behind eyes; head subconical before orbit; snout truncate; lips plicate, very thick; single large tooth in each half of both jaws, the teeth sub- equal and forming a beak; nasal apparatus a solid oblong tentacle bifid in distal two- thirds, apposed surfaces of terminal "lobes" smooth (fig. 27, 6); nasal tentacle 2.3 mm., antero-mesad from orbit; eye in center of head, longitudinal axis slightly above line connecting upper end of branchial opening and corner of mouth; branchial opening immediately anterior to base of pectoral, shorter than pec- toral base, half diameter of eye. THE LIBRARY OF THE No. 708 149 AUG17-F1 (- fjJ'tOlS 150 FIELDIANA: ZOOLOGY, VOLUME 34 Scaleless; erectile spines with bifid base covering back, sides, and belly anterior to level of vent, top of head and throat to an- terior level of eyes, and sides of head behind eyes; lateral line system indistinct, a line across snout between nasal tentacles and mouth, a supraorbital line strongly curved inward, a transverse occipital line curving backward from hind corner of eyes, a lateral line arching high above pectoral and becoming invisible anterior to level of dorsal. Pectorals broad, base slightly off vertical, in mid-line, margin feebly rounded, third and fourth branched rays the longest, sub- equal to eye; origin of dorsal equidistant from end of pectoral and mid-base of caudal, margins rounded; anal origin opposite that of dorsal, margin rounded; caudal truncate; vent 2.5 mm. before anal origin. Dorsal ii,10; pectoral ii,16; anal i,9; caudal ii,9; total length 64 mm.; standard length 52.0 mm.; head length 22.5 mm., width 19.0 mm.; eye 6.1 mm.; snout 8.4 mm.; postorbital head length 8.0 mm.; maximum body depth (uninflated) 17.8 mm. Color (in life) olive-green dorsally and laterally, with round and oblong black spots of varying sizes; a black occipital chevron; a partially interrupted ventro-lateral black stripe running from mouth below eye and pectoral and fading anterior to vent; ventral surface of head and trunk anterior to vent white; fins unmarked; caudal dusky. Paratypes. — C.N.H.M. 51559 (34 specimens) from the type lo- cality; C.N.H.M. 51562 (12 specimens) from the Gaja River, ap- proximately one and one-half miles above its mouth; C.N.H.M. 51560-61 (7 specimens) from the Kretam Kechil River near its mouth; C.N.H.M. 51563 (3 specimens) from a tributary of the Gaja River. Variation in color among these involves the presence or absence of the ventro-lateral band and its intensity. The distribution, size, and shape of the black spots also vary. The occipital chevron is almost always present. Some specimens have an interorbital bar, others only a spot. Occasionally spots coalesce to form a partial or complete cross on the back. In no specimen is the caudal barred. Dorsal ii-iii,8-ll; pectoral ii,15-18; anal i-ii,7-9; total length 10.5-60 mm.; standard length 7.9-46.6 mm.; head in standard length 2.10-2.26 (mean of eleven including type 2.19±0.02). Remarks. — The new species is similar to leiurus Bleeker (type locality Java) and fluviatilis Hamilton (type locality Bengal) but INGER: A FISH FROM BORNEO 151 differs from both in fin ray counts. It also differs from fluviatilis in having smooth rather than spongy or cellular inner surfaces on the nasal flaps (fig. 27). The following table sets forth differences distinguishing these species. The counts of leiurus are taken from Bleeker's original description (1852) and one other specimen collect- ed by Bleeker and now in the British Museum. The Ganges fluvi- atilis is represented by four specimens (also in the British Museum) FIG. 27. Nasal tentacles of Tetraodon showing difference between (a) T. fluviatilis Ham. (42 mm.) and (b) T. kretamensis sp. nov. (52 mm.). from Allahabad, which is not far from the type locality. Data on the British Museum specimens were generously supplied by Mr. N. B. Marshall. Information on Bornean fluviatilis is based on twelve specimens from North Borneo. leiurus Dorsal 14 Pectoral 22-23 Anal 11 Nasal surface . . . . smooth fluviatilis kretamensis Ganges Borneo 15-16 13-15 10-13 19-20 21-23 17-20 13-14 11-12 9-11 spongy spongy smooth The exact relationship between leiurus and kretamensis is not clear. They may prove to be geographic representatives of a wide- ranging species. There can be no doubt, however, of the distinction between fluviatilis and kretamensis. Both species were collected at the same stations on the Pinang River. The two groups of speci- mens, separated on the basis of the inner surfaces of the nasal flaps, showed striking differences in fin ray counts as may be seen in the preceding table and the following comparisons of means. 152 FIELDIANA: ZOOLOGY, VOLUME 34 fluviatilis kretamensis (12 specimens) (24 specimens) Difference t P Dorsal 13.8±0.2 11.7±0.1 2.1 9.012 <0.001 Pectoral 21.8±0.2 18.5±0.1 3.3 13.750 <0.001 Anal 11.8±0.1 10.2±0.1 1.6 9.580 <0.001 Differences among fluviatilis, leiurus, and kretamensis in colora- tion of the tail (usually without bars in the last two and with bars in fluviatilis) may not be reliable. The bars of fluviatilis may be obscure or completely lacking. The ability of these fishes to change color pattern may account for the apparent difference. REFERENCES BLEEKER, PIETER 1852. Bijdrage tot de kennis der blootkakige visschen van den Soenda-Moluk- schen Archipel, met beschrijving van eenige nieuwe soorten. Verb. Batav. Genootsch., 24: 1-26. UNIVERSITY OF ILLINOIS-URBANA