5 p. : ill. ; 24 cm.Includes bibliographical references

Gudger, E. W. (Eugene Willis), 1866-1956.

Mortimer, Lawrence.

American Museum of Natural History Scientific Publications

AMERICAN MUSEUM NOVITATESPublished byNumber 896 THE AMERICAN MUSEUM OF NATURAL HISTORY Dec. 31, 1936New York CityA REVERSED ALMOST WHOLLY AMBICOLORATESUMMER FLOUNDER, PARALICHTHYS DENTATUSBY E. W. GUDGERThis specimen, the most abnormal flounder that has ever come intomy hands, was taken at Freeport, Long Island, July 21, 1935. It waspresented to the Museum by Mr. Lawrence Mortimer of Garden City,Long Island, to whom go my best thanks for this remarkable specimen.It is most abnormal in that it is reversed i.e., it points to the rightwhen it should point left; and it is ambicolorate-i.e., its under surface,instead of being white, is almost wholly dark.Fig. 1. Upper side of a normal Paralichthys dentatus. The normal fish is left-handed, i.e., the fish points left and has eyes and color on the left side.After Jordan and Evermann, 1900.THE NORMAL FISHIn order that the reader may have a basis for understanding just howabnormal this specimen is, it will be necessary to give a figure and briefdescription of the normal fish. This, as shown in Fig. 1, is a sinistral,left-pointing or left-handed fish, having eyes and color on the left sideand the right side blind and colorless. The color of the upper sidevaries with the bottom on which it is found, but in its southern range atAMERICAN MUSEUM NOVITATESany rate it is generally a light olive with many small white spots on thebody, and still smaller ones on the vertical fins (not shown, however,in the figure). In addition there are on the upper side 10 to 15 ratherlarge dark spots with white borders.P. dentatus is a western Atlantic flounder ranging from Massachu-setts (Cape Cod) to Florida. Except the halibut, it is the largest of oureast coast flatfishes. It grows to a length of 3 ft. and a weight of 26 lbs.,but the average weight is about 3 lbs. My specimen measures 15 in.over all, and weighs 1 lb. 1 oz. It is then a comparatively small summerflounder.THE REVERSED FISHSince this specimen is abnormal on both sides it will be necessarycarefully to study both surfaces. That side will be taken up first whichthe observer would see first.Fig. 2. The upper, or eyed and colored side of the reversed or right-handedsummer flounder. Note the number and position of the spots, also the hooked dorsalfin and the incompletely rotated eye.A.-THE UPPER OR DARK SIDEFig. 2 shows that the normally left-handed P. dentatus has becomeright-handed in this specimen. It is eyed and colored on the right sideinstead of on the left. In reversal the color of the left side has come overto the right. This is not an unusual phenomenon in flatfishes, but inthis specimen it is noteworthy that the spots normal to the left sidehave come over along with the general coloration to the right side.[No. 89621936] REVERSED AMBICOLORATE SUMMER FLOUNDER 3Noticeable are the 15 large dark spots with white rings. Three ofthese are on the lateral line; and if this ran straight forward to themouth, then a fourth would also be on it. Four are found well up towardthe base of the dorsal, and four near the anal fin. Further these dorsaland anal spots show a certain bilaterality with reference to the medianline of the body and with regard to each other. Then along the basesof dorsal and anal fins, and on these fins, are many small white spots ofindeterminate number. Presumably in the normal fish there is somevariation in the number and arrangement of these spots. What andwhere these would have been on a normal fish, one cannot say, but Idare conjecture that their number and arrangement in this reversedspecimen are what they would have been on the left side of this fishhad it not been reversed.In ambicolorate flounders, specimens have been recorded in whichdorsal spots have been reproduced on the ambicolorate lower surface.But this seems to be the first figure and record showing the reproductionof spots on a reversed flounder. At least I found none in a recentpaper' on reversal, in which I studied every account that I could find ofthis phenomenon.When this reversed flounder is looked at from its functional upperside, one sees not merely that this side is colored, but that the head showscertain anomalies. Compared with the normal fish, the travelling eyehas not come over to its normal position but has stopped nearly on thedorsal crest. Furthermore the anterior end of the dorsal fins ends in acurious hook. Attention is called here to these anomalies; they willbe discussed in the next section.B.-THE LOWER OR AMBICOLORATE SIDEEven after a year in alcohol the under side of this fish is of a decidedlyolive hue. The color is lighter than that of the upper side, but it issurely ambicolorate. As Fig. 3 shows, the under side is everywhere darksave for the white on the hinder part of the pectoral fin and on the headproper. On the top of the head, the dark color comes over from the upperside-barely over in front of the eye, but markedly over under andbehind the eye and under the hooked dorsal fin. The dark color coversthe opercles and the lower jaw. In other words the white head proper isframed in dark.Of particular interest is the number (15) of the large spots on the'Gudger, E. W. 'Abnormalities in Flatfishes (Heterosomata). I. Reversal of sides: acomparative study of the known data.' Jour. Morphol., 1935, LVIII, 1-39, 5 figs.AMERICAN MUSEUM NOVITATESlower side of this fish. About 12 of them in their positions fairly dupli-cate those of the upper side. The careful insertion of a needle throughthe center of each of the 12 lower spots shows that each is a duplicateof that on the upper side. Sometimes the needle comes out squarely inthe center of the upper spot, sometimes the lower is placed eccentricallywith regard to the upper spot, and in a few cases the needle narrowlymisses the upper spot. But the spots on the lower side surely in a fairlyaccurate way duplicate those above.Also of especial interest are the head anomalies. The left or rotatingeye has its left edge just on the dorsal ridge, so evidently so that the eyeis plainly visible from the blind side. Overhanging the hinder edge ofthe eye is the hooked anterior part of the dorsal fin. The point of thehook is curiously enough white on the lower side but it is dark on theupper side.Fig. 3. The left or lower ambicolorate side of this reversed summer flounder.The whole lower side is dark save the central part of the head and the piebald pectoralfin. Note the number and position of the spots. The rotating eye is still visible andis overhung by the hooked dorsal fin.This almost wholly ambicolorate flounder in its color and its headanomalies conforms to the general rule. This is that when the wholelower body and approximately one-third of the head is dark, then therewill be found an incompletely rotated eye and a hooked dorsal fin.This specimen is unique among flounders. There has been but oneother reversed ambicolorate flatfish described. In 1907, Cunningham11 Proc. Zool. Soc. London, pt. 1, pp. 174-181, 2 figs.4 [No. 8961936] REVERSED AMBICOLORATE SUMMER FLOUNDER 5figured and described a reversed turbot partially ambicolorate on theblind side and white on the eyed side. However, it was only 44 mm.(1.7 in.) long-hardly more than a post-larval fish, whereas my speci-men is an adult. In addition to the flounder herein described, I havetwo reversed partially ambicolorate halibuts. These will be describedlater, and still later I plan to bring together and study all these re-versed ambicolorate flatfish in the endeavor to find an explanation ofthis double anomaly.

Reversed ambicolorate summer flounder

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