The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1897-04-11
SLEEPING FISH CHANGE COLOR.
Some Also Take Peculiar Attitudes
When They Rest.
Nature.


While investigating the nocturnal habits
and colors of some of our native marine
nsheS L made the unexpected discovery that
number of species had the peculiar habit
OF assuming while sleeping a style of col
time.
Most OF my observations were made late
at night, between midnight and 2 o'clock a.
m. The gas jets near the aquaria were
turned down so low AS to give barely light
enough 10 distinguish the forms and colors
or the fishes. Under these conditions by
using great care not to cause any jar of
the floor nor sudden movement OF any kind,
L succeeded in observing many species
asleep. Most fishes sleep very lightly and
are aroused by almost impeTceptible Vibra-
tons or the air or water. Some of these
hshes took unexpected attitudes while
In many cases the change Of color from
that seen while awake or In the daytime
consisted In simple increase In the depth
or intensity of the colors, the pattern OF
colors being the same This the case
with several species of founders. Those
that are spotted or notified with dark pig
ment showed their markings much more
strongly or in greater contrast with the
ground color than by day. Several species
or minnOWS tunduluS), which are marked
either with longitudinal or transverse dark
bands, have these markings more decidedly
black and better defined than by day. The
same Is true of the king fish (menticirrus
nebuloSus), in which there are obliquely
transverse dark stripes that come out more
strongly at night than by day.
The black seabass (Serranus furvus) and
the searobins (Prionotus plamipes and p.
evolans) presented the same phenomena
several sf; species OF trout (Salvelinus fontin-
darker at night than in the daytime, but
L was not sure that any of those observed
were asleep at the time.
Ii is well known that trout founders and
some other fishes are able to change their
color, even in the daytime according 10 the
color or their surroundings. Therefore a
darkening of the colors at night is TO be
expected, even if not asleep. But in all
the cases mentioned above the nocturnal
change of color Is of a protective character
Other fishes, however. show much more
remarkable changes. Among these the soup
or pOrgy tStenOtomus chrysopS) is enc of
in the daytime, usually has a bright sill
very color with iridescent tints. But at
night, when asleep, it has a dull. hronzy
ground color, and the body is crossed by
about six transverse black bands When
one of these fishes, with this coloration,
was awakened by suddenly turning Up the
gas, II Immediately assumed the bright sill
very colors belonging TO it's daytime dress.
This experiment was repeated many times,
On different individuals, with the same
SUIT. As this fish naturally rests among
eel-grass and seaWeeds, the protective
character of its nocturnal colors is obvious.
A common fetish (Monacanthus, sp) was
observed that presents a very decided
change in color pattern. This species, in
the daytime, is notified with brown and
dark olive green. and the fins and tail are a
asleep. at night, its body becomes pallid
gray or nearly white, while the fms and
tail become decidedly black These colors
are decidedly protective at night, in a
feeble light, among rocks and weeds. where
II lives. This and other species of filefishes,
when sleeping. would usually rest on the
bottom with the back leaning against the
glass OF the aquarium or against a stone
at considerable angle.
The common tautog or blackhsh (Tauto-
so onitis) has the curious habit of resting
upon one side. half buried among gravel
Or partly under stones. and is often curved
in strange positions. IL il easy TO imagine
that the founders originated from some
symmetrical ancestral form that acquired,
like the tautog. the habit OF resting upon
one side. at first only when sleeping but
afterwards continually. owing TO the 81 at
or protection that this habit and its imi-
tatiVe cOloration afforded. The one-sided
coloration and the changes i'm the position
OF the eyes, etc, would gradually follow in
accordance with well-knOwn laws of evolu-
ton.
The common squid Loligo PealeD was
observed sleeping on several occasions. At
such times II rests in an inclined position
on the tip OF its tail and on the basal parts
or the arms. which are punched together
and extended forward. 50 that the head and
anterior part OF the body are raised from
the bottom 10 give room for breath
ing. The Siphon tube is then turned to one
side Under these circumstances the color
II darker ana the spots more distinct than
when ~ IL active. owing TO the expansion
of the brown and UUrnlp ChrOma tOphOrpg