! A HYBRID IN DANIO | 
| | ERNEST LEITHOLF | 
* 
During the past few years, after hav- 
ing raised a sufficient number of young 
Danio rerio and D. analipunctatus, we 
have at times placed breeding pairs of 
both species together. While the spe- 
cies have been associated we have at 
times secured spawn, but until this year 
the resulting progeny have always proved 
of one or the other, and from this we 
concluded that there was no disposition 
to interbreed. Last spring three or four 
pairs of each species were placed to- 
gether in an aquarium. From them we 
raised a large number of young, the eggs 
having been secured at intervals. Later 
in the season, while selecting specimens 
to be placed aside for breeding next year, 
we were astonished to discover four 
youngsters, about three-fourths grown, 
that displayed unmistakable evidences of 
hybridity ! 
To give a good conception of the rela- 
tive color arrangements of the parents 
and their fortuitous offspring, I have pre- 
pared three sketches; D. rerio is shown 
at the top, the hybrid next, and D. anali- 
punctatus below. ‘The hybrids seem to 
have inherited characters equally from 
each parent. The body is similarly prim 
and elegant, but the colors are more iri- 
descent, and the silvery bars of a warmer 
hue than in D. rerio. The back or dorsal 
region is a greenish olive. Through the 
centre of the side runs a wide, dark blue 
band, which is edged above with a promi- 
nent band of silver, this in turn 1s fol- 
lowed by a band of blue about half as 
wide as the central one. The two wide 
bands with the narrow one above is a 
pronounced characteristic of D. anali- 
punctatus. A row of symmetrical dots 
crowns the upper bands. Below the 
bands are two rows of dark blue bars of 
varying lengths, interspersed with dots, 
the lowest extending forward to the 
ventrals. At this point the four indi- 
viduals differ somewhat in detail. In one 
the dots predominate, but the linear ef- 
fect is retained. The caudal, anal and 
ventral fins carry rows of long dashes. 
Upper, Danio rerio; lower, D. analipunctatus; 
centre, D. rerio x D. analipunctatus 
Original Water Color by the Author From Life 
Regarding the actual production of the 
hybrid, we are inclined to think that the 
parent species chanced to spawn simul- 
taneously, and that the sperm of one fer- 
tilized the ova of the other. This seems: 
the only tenable theory, inasmuch as the 
persistent association of the parent spe- 
cies during other years yielded none other 
than the progeny of properly disposed 
Danio. The possibility of this hybrid 
being fertile is now engrossing our 
thoughts. It is needless to add that the 
four individuals are enjoying unusual 
care. 
