162 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



THE MUMMICHOGS OR KILLIFISHES. FAMILY POECILIIDAE 



The mummichogs are small fishes made rec- 

 ognizable by having only one short soft-rayed 

 dorsal fin situated far back, and ventrals situ- 

 ated on the abdomen, combined with a small 

 mouth at the tip of the snout, a very thick caudal 

 peduncle, and a rounded tail fin. The family is 

 represented in the Gulf of Maine by three species, 

 two of Fundulus and one of Cyprinodon, the former 

 slender and the latter deep in outline, a dif- 

 ference in body form sufficient to distinguish the 

 one genus from the other at a glance. The 

 teeth are likewise different in the two genera, 

 those of Fundulus being sharp-pointed, whereas 

 they are wedge-shaped in Cyprinodon and in- 

 cisorlike. The two local species of Fundulus 

 are separable by their markings, majalis of all 

 ages being barred or streaked with black while 

 the adult heteroclitus is not. 



Common mummichog Fundulus heteroclitus 

 (Linnaeus) 1766 



Killifish; Salt-water minnow; Chub; Mummy 



Jordan and Evermann, 1896-1900, p. 640. 



Description. — This is a stout-bodied little fish, 

 about one-fourth as deep as long, its body thickest 

 just back of the pectoral fins, whence it tapers to 

 the tail. Both its back and its belly are rounded, 

 but the top of the head is flat between the ej^es. 

 The snout, as seen from above, is blunt. The 

 mouth is at the tip of the snout and is so small that 

 it does not gape back to the eye. Perhaps the most 

 striking feature of Fundulus is its very deep caudal 



peduncle and rounded caudal fin. The fins are of 

 moderate size, the dorsal situated behind the 

 middle of the body above the anal, the pectorals 

 broad and rounded. Both head and body are 

 covered with large rounded scales. On males in 

 breeding condition the scales on the sides of the 

 head and those on the flanks below and behind the 

 dorsal fin develop fingerlike processes on their free 

 edges, called "contact organs." 



The mummichog shows a striking sexual dimor- 

 phism in the dorsal and anal fins, which are not 

 only larger in the male than in the female, and the 

 anals of a different shape, 90 but are more muscular 

 and are used as claspers in the act of spawning. 



Color. — Males and females differ in color as well 

 as in the sizes of the fins. Out of breeding season 

 the males are dark greenish or steel blue above, 

 with white and yellow spots, and marked on the 

 sides with narrow irregular silvery bars or mot- 

 tlings made up a series of dots. The belly is 

 white, pale yellow, or orange; the dorsal, anal, and 

 caudal fins are dark green or dusky with pale 

 mottlings; the front edges of the anal and of the 

 ventrals are yellow. Sometimes there is a dark- 

 edged, pale-centered eyespot on the rear part of 

 the dorsal fin. At spawning time the pigmenta- 

 tion of the male is generally intensified, the back 

 and upper sides darkening almost to black, while 

 the yellow of the belly becomes more brilliant and 

 the body generally takes on steel-blue reflections. 

 The females (much paler than the males) are uni- 



x> A detailed account of the sexual differences is given by Newman (Biol. 

 Bull., vol. 12, No. 5, 1907, pp. 314-348). 



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Figure 76. — Common mummichog (Fundvhts heteroclitus), Maryland. From Jordan and Evermann. 



A. H. Baldwin. 



Drawing by 



