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LUMINESCENT FISHES

FAMILIES MYCTOPHIDAE, MAUROLICIDAE, CHAULIODONTIDAE, GONOSTOMIDAE, STOMIATIDAE, AND STERNOPTYCHIDAE


These families include a heterogeneous assemblage of small oceanic fishes, that are primitive in some respects, but are highly specialized in others for existence in mid-depths, on the high seas.

They all have light-producing organs, which no other Gulf of Maine fish has; this is the only reason why we group them together here.

KEY TO GULF OF MAINE LUMINESCENT FISHES
1. Trunk at least ½ as deep as it is long from tip of snout to base of tail fin; front part of rayed dorsal fin is a hard triangular plate, supported by 7 or 8 spines Hatchet fish, p. 149
Trunk less than ¼ as deep as it is long from tip of snout to base of tail fin; rayed dorsal fin does not commence with a hard plate or hard spines 2  
2. Mouth does not gape back as far as the eye Pearl sides, p. 144
Mouth gapes back beyond the eye 3  
3. No barbel on the chin; the ventral fins are about mid-way of the trunk; origin of rayed dorsal fin either in front of midlength of trunk or at least not much behind it 4  
There is a long fleshy barbel on the chin; the ventral fins are considerably behind the mid-length of the trunk; the rayed dorsal fin is far back, close to the tail fin 7  
4. The rayed dorsal fin is far in advance of the ventrals; the jaws are armed with long and conspicuous fangs Viperfish, p. 145
The rayed dorsal fin is about over the ventral fins (it may be a little in front of them or a little behind); the teeth are small 5  
5. Eyes very small; no adipose fin behind the rayed dorsal fin; anal fin reaches nearly to the base of the caudal Cyclothone, p. 146
Eyes very large; there is an adipose fin behind the rayed dorsal; there is a considerable interspace between the rear end of the anal fin and the origin of the tail fin 6  
6. There are 3 or 4 separate luminescent dots at the base of the caudal fin; the Gulf of Maine species has a large luminescent patch on the snout Headlight fish, p. 142
There are only 2 separate luminous dots at the base of the caudal fin; the snout does not have a large luminescent patch Lanternfish, p. 143
7. The point of origin of the anal fin is in advance of the origin of the rayed dorsal fin by a distance about as long as the diameter of the eye; the tip of the chin barbel is distinctly swollen as well as bearing several filaments Stomioides, p. 147
The point of origin of the anal fin is not in advance of the rayed dorsal fin, the tip of the chin barbel is not swollen 8  
8. Each side has only about 68 luminescent spots; there is a large luminescent patch crossing the top of the cheek, behind the eye; the point of origin of rayed dorsal fin is in advance of origin of anal fin by a distance about as long as the diameter of the eye; the tip of the lower jaw does not enclose the tip of the upper jaw when the mouth is closed Trigonolampa, p. 148
Each side has about 85 luminescent spots; the side of the cheek behind the eye does not have a large luminescent patch; the point of origin of rayed dorsal fin is about over origin of anal fin; the tip of the lower jaw encloses the tip of the upper jaw when the mouth is closed Stomias, p. 147