212 
FOREST AND STREAM 
[Aug. ii, igo6. 
The Sea-Horses 
BY THEODORE GILL. 
From “The Life History of the Sea-Horses,” by Theodore 
Gill, Honorary Assistant in Zoology. Printed in the 
Proceedings of the United States National Museum. 
In the ordinary works on fishes or natural 
history very little is said about the interesting 
little fishes popularly known as sea-horses. Many 
details, however, have been published in isolated 
notes or buried in general articles, which only 
one familiar with ichthyological literature would 
be likely to know about or even to find by using 
the current bibliographies. For the benefit of 
those interested in the group the notes here pre¬ 
sented, brought together for a general work on 
fishes, are published. 
The sea-horses (Hippocampids) vary in form, 
but all are compressed and incapable oi flexing 
the body sideways to any very considerable ex¬ 
tent, the plates having extensions which are 
buttressed against corresponding ones of the 
preceding and succeeding plates, thus pro¬ 
hibiting any decided lateral movements. 
The tail is more or less curved down¬ 
ward, and in typical forms highly prehensile, it is 
quadrangular in section. 
The head in front of the eyes, or snout, is pro¬ 
longed in a tubiform manner as in the pipe-fishes 
(Syngnathida) , and the mouth and jaws are 
small and at the end of the tube; the preopercle 
is absent and the operculum greatly enlarged. 
The likeness to the convential knight of the 
chessboard is much more marked than to a 
horse’s head; indeed, if a spirula-shell or coiled 
worm were attached to the base of a chess knight 
the sea-horse would be well imitated. The 
ancient Hippocampus is therefore very apt, being 
derived from the Greek hippos, horse, and kampe, 
worm or caterpillar. But let no one be deceived 
by superficial resemblance of parts. The head 
of the fish and that of a horse are essentially® 
homologous, but here real likeness ends; the con¬ 
tracted part of the sea-horse does not correspond 
to the neck of a true horse, but to the fore part 
of the abdomen, there being no true neck in the 
fish; the lower part of the “neck” of the fish is 
really the hinder part of the abdomen, and the 
anus marks its hinder boundary. 
The peculiar modification of the finless tail de¬ 
prives it of its locomotor faculty, but a new 
function—prehension—results from its power to 
curl inward, and, to some extent, sideways. 
The species are numerous, and one or more 
may be found in almost every tropical and tem¬ 
perate sea. Somewhere near three dozen species 
have been described, and of these one is a com¬ 
mon European fish, and half a dozen are inhab¬ 
itants of north or middle American seas. One 
of them extends northward in the Atlantic as far 
as Cape Cod, and another one of the largest of 
the genus, in the Pacific to San Diego. 
Strongly marked and bizarre as is the form, 
the fishes nevertheless are not conspicuous in 
the midst of their natural surroundings, and in¬ 
deed the little animals appear to be able to readily 
adapt themselves to their environment. Kent 
tells that “some very extraordinary colored speci¬ 
mens” of the common Mediterranean species 
were given to him; some were “bright red, others 
pale pink, bright or light yellow, and even almost 
interblending shades. Such colors had apparently 
been assumed by the fish in keeping with and as 
a means of concealment among the brilliant 
vegetation and zoophytic growth indigenous to 
the locality from whence they were derived. 
These tints in confinement gradually disappeared, 
until the fish had assumed the normal light-brown 
or speckled hue by which they are generally 
characterized.” 
The attitudes and movements of the sea-horses 
are eminently characteristic. The most frequent 
is a state of rest, with the tail wound around the 
stem of a plant or some other substance and the 
body is then carried nearly or quite erect. Such 
is the most frequent position, but notwithstanding 
the apparent rigidity of the cuirass, almost every 
other attitude consistent with such a form may 
be assumed. The body may be thrown outward 
at various angles and even downward and the 
tail wound around a plant in a double coil. Once 
in a while one eye may roll toward you, while 
another may be passive or look backward or in 
an opposite direction. It becomes obvious that 
the little fish can move its eyes independently of 
each other and in entirely different ways. 
A comical effect is produced by the way in 
which the little fishes peer at some object, re¬ 
minding one of the actions of a very near-sighted 
person. 
Releasing itself at length from its support, one 
may slowly progress, still in a vertical position, 
its tail curved inward, its dorsal fin rapidly un¬ 
dulating and reminding one of a screw propeller, 
its pectorals vibrating in harmony. The rapidity 
of the undulatory or vibratory movements of the 
dorsal and pectorals is especially noteworthy. 
Incased as it is in an almost inflexible coat of 
mail, progression can not be affected by lateral 
AUSTRALIAN SEA HORSE RESEMBLING SEA-WEED. 
flexion of the body as in ordinary fishes, and 
flexion in a vertical direction is limited. 
With such limited powers of progression, a 
nice adjustment of organs is called for, and 
Dufosse has explained one method. The air 
bladder is comparatively large and always dis¬ 
tended by a quantity of gas so exactly in harmony 
with the specific gravity of the body that this 
entire body is a hydrostatic apparatus of extreme 
sensibility. A proof of this is that if a single 
bubble of gas no larger than the head of a very 
small pin be extracted, the fish immediately loses 
its equilibrium and falls to the ground, on which 
it must crawl till its wound has been cicatrized 
and a new supply of gas secreted by the internal 
membrane of the bladder. 
Another noteworthy peculiarity is a faint sound 
which is sometimes evoked. Kent, while making 
“some colored sketches” of the fishes, had two 
“isolated in separate glass receptacles some few 
yards apart, when unexpectedly a sharp little 
snapping noise was heard at short and regular 
intervals to proceed from one of the vases placed 
on a side table, and to which a response in a like 
manner was almost immediately made from the 
vase close at hand. On seeking for the cause, 
the sound was found to proceed from the mouths 
of the little Hippocampi, which were thus con¬ 
versing with, or signaling to, one another. The 
noise observed was produced by the muscular 
closing and sudden expansion of the lower jaw, 
and much resembled in strength and tone the 
snapping sound produced for a similar purpose, 
but in this instance with its claw, by the little 
scarlet prawn,” ‘relatives of which occur along 
the southern coast of the United States. 
The mechanism which produced the sounds emit¬ 
ted by the sea-horse was explained at length by Du¬ 
fosse in 1874 to whose memoir reference may be 
made by those who wish to learn details. Suffice 
it here to note that Dufosse found that the fishes 
had the power of making long series of move¬ 
ments so slight and so rapid that they evade the 
sight, but are appreciable to touch, and conse¬ 
quently are simple quiverings or vibrations, and 
that these quivering movements are accompanied 
by sounds which, however, are rarely distinctly 
audible. The sounds are produced by females as 
well as males; notably in the spawning season, 
when they are both more frequent and more in¬ 
tense. 
The natural food of the sea-horses consists 
mainly of small crustaceans, such as copepods, 
sand-fleas and the opossum shrimps as well as 
the young of higher forms. Such being not 
readily obtainable by aquarium keepers, Kent im¬ 
provised for his aquaria “a successful substitute 
in the form of the larvae of the common gnat” 
or mosquito and “other water insects.” 
The mode of feeding is curious. A supply of 
amphipodous crustaceans may be supplied to them 
and a fish will slowly move toward one, peering 
at it, approaching the mouth to it, and suddenly 
the animalcule may disappear without any per¬ 
ceptible movement of the jaws as though the fish 
had sucked it in % But the amphipod (or other 
animal) must be at rest or on the ground or a 
plant; for the fish is too slow to get one moving; 
nevertheless it must be alive. The fish may throw 
itself on its sides or in any attitude most fit to 
get hold of the coveted “bug.” 
The species of Hippocampus are numerous (be¬ 
tween 30 and 40), but the many common charac¬ 
ters are so much more prominent and striking 
than the specific ones that the latter are apt to be 
lost sight of and overshadowed by the for¬ 
mer. The distinctions between the species are 
chiefly based on the length and number of rays 
of the dorsal fin, the number of rings encircling 
the body, the comparative lengths of the body 
and tail behind the anus, the depth of the body 
or distance across from the dorsal ridge to the 
ventral, and the relative length of the head and 
snout in front of the eyes. These are supple¬ 
mented by the comparative development of the 
tubercles or spines, of the coronet at the crown 
of the head or nape, of the filaments with which 
the body may be covered, and the color. In 
illustration of such, figures are given of four 
species. 
The common eastern American sea-horse ( Hip¬ 
pocampus hudsonius ) has a long dorsal with 
about nineteen rays, about forty-five rings, the 
tail longer than head and trunk combined, the 
snout short but appreciably longer than rest of 
head and the depth of the body approximately 
equals the length of the head. The coronet is 
little developed, the tubercles and spines weak, 
and the filaments rather few, short, and mostly 
simple. The color is dusky and spotless (but 
blotched) and the dorsal has a submarginal dark 
band. 
The sea-wrack sea-horse ( Hippocampus zos- 
terce) of Florida contrasts with the common 
species of the north in most of its characters. It 
has a short dorsal (covering only three rings) with 
about twelve rays, about forty-one rings, the tail 
rather shorter than the rest of the body, the 
snout extremely short and not more than half 
the rest of the head, and the depth of the body 
great and almost equal to length from snout to 
margin of pectoral fins. The coronet is high, 
the spines are well developed, and the filaments 
moderate and often branched. The color is 
olive green, more or less mottled, and the dorsal 
has no distinct submarginal band. It is, accord- 
