PHTHINOBRANCHII: HEMIBRANCHII, LOPHOBRANCHII,
AND HYPOSTOMIDES
[Illustration:
FIG. 180.—Shoulder-girdle of a Stickleback, _Gasterosteus aculeatus_
Linnæus. (After Parker.)
]
[Illustration:
FIG. 181.—Shoulder-girdle of _Fistularia petimba_ Lacépède, showing
greatly extended interclavicle, the surface ossified.
]
=SUBORDER Hemibranchii.=—Still another transitional group, the
_Hemibranchii_, is composed of spiny-rayed fishes with abdominal
ventrals. In this suborder there are other points of divergence, though
none of high importance. In these fishes the bones of the
shoulder-girdle are somewhat distorted, the supraclavicle reduced or
wanting, and the gill structures somewhat degenerate. The presence of
bones called interclavicles or infraclavicles, below and behind the
clavicle, has been supposed to characterize the order of _Hemibranchii_.
But this character has very slight importance. In two families,
_Macrorhamphosidæ_ and _Centriscidæ_, the interclavicles are absent
altogether. In the _Fistulariidæ_ they are very large. According to the
studies of Mr. Edwin C. Starks, the bone in question is not a true
infraclavicle. It is not identical with the infraclavicle of the
Ganoids, but it is only a backward extension of the hypocoracoid, there
being no suture between the two bones. In those species which have bony
plates instead of scales, this bone has a deposit of bony substance or
ganoid enamel at the surface. This gives it an apparent prominence as
compared with other bones of the skeleton, but it has no great taxonomic
importance. Dr. Hay unites the suborders _Hemibranchii_,
_Lophobranchii_, and _Hypostomides_ to form the order _Phthinobranchii_
(φθινάς, waning; βράγχος, gill), characterized by the reduction of the
gill-arches. These forms are really nearly related, but their affinities
with the _Percesoces_ are so close that it may not be necessary to form
a distinct order of the combined group. Boulenger unites the
_Hemibranchii_ with _Lampris_ to form a group, _Catosteomi_,
characterized by the development of infraclavicles; but we cannot see
that _Lampris_ bears any affinity to the sticklebacks, or that the
presence of infraclavicle has any high significance, nor is it the
supposed infraclavicle of _Lampris_ homologous with that of the
_Hemibranchii_. The dorsal fin in the _Hemibranchii_ has more or less
developed spines; spines are also present in the ventral fins. The lower
pharyngeals are separated; there is no air-duct. The mouth is small and
the bones of the snout are often much produced. The preopercle and
symplectic are distinct. The group is doubtless derived from some
transitional spiny-rayed type allied to the _Percesoces_. The
Lophobranchs, another supposed order, represent simply a still further
phase of degradation of gills and ventral fins. Dr. Gill separates these
two groups as distinct orders and places them, as aberrant offshoots,
near the end of his series of bony fishes. We prefer to leave them with
the other transitional forms, not regarding their traits of divergence
as of any great importance in the systematic arrangement of families.
=The Sticklebacks: Gasterosteidæ.=—The sticklebacks (_Gasterosteidæ_)
are small, scaleless fishes, closely related to the _Fistulariidæ_ so
far as anatomy is concerned, but with very different appearance and
habits. The body often mailed, the dorsal is preceded by free spines and
the ventrals are each reduced to a sharp spine with a rudimentary ray.
The jaws are short, bristling with sharp teeth, and these little
creatures are among the most active, voracious, and persistent of all
fishes. They attack the fins of larger fishes, biting off pieces, and at
the same time they devour the eggs of all species accessible to them. In
almost all fresh and brackish waters of the north temperate zone these
little fishes abound. "It is scarcely to be conceived," Dr. Günther
observes, "what damage these little fishes do, and how greatly
detrimental they are to the increase of all the fishes among which they
live, for it is with the utmost industry, sagacity, and greediness that
they seek out and destroy all the young fry that come their way."
The sticklebacks inhabit brackish and fresh waters of the northern
hemisphere, species essentially alike being found throughout northern
Europe, Asia, and America. The same species is subject to great
variation. The degree of development of spines and bony plates is
greatest in individuals living in the sea and least in clear streams of
the interior. Each of the mailed species has its series of half-mailed
or even naked varieties found in the fresh waters. This is true in
Europe, New England, California, and Japan. The farther the individuals
are from the sea, the less perfect is their armature. Thus,
_Gasterosteus cataphractus_, which in the sea has a full armature of
bony plates on the side, about 30 in number, will have in river mouths
from 6 to 20 plates and in strictly fresh water only 2 or 3 or even none
at all.
The sticklebacks have been noted for their nest-building habits. The
male performs this operation, and he is provided with a special gland
for secretion of the necessary cement. Dr. Gill quotes from Dr. John A.
Ryder an account of this process. The secretory gland is a "large
vesicle filled with a clear secretion which coagulates into threads upon
contact with water. It appears to open directly in front of the vent. As
soon as it is ruptured, it loses its transparency, and whatever
secretion escapes becomes whitish after being in contact with water for
a short time. This has the same tough, elastic qualities as when spun by
the animal itself, and is also composed of numerous fibers, as when a
portion is taken that has been recently spun upon the nest. Thus
provided, when the nuptial season has arrived the male stickleback
prepares to build his nest, wherein his mate may deposit her eggs. How
this nest is built, and the subsequent proceedings of the sticklebacks,
have been told us in a graphic manner by Mr. John K. Lord, from
observations on _Gasterosteus cataphractus_ on Vancouver Island,
although the source of his secretion was misunderstood:
"The site is generally amongst the stems of aquatic plants, where the
water always flows but not too swiftly. He first begins by carrying
small bits of green material which he nips off the stalks and tugs from
out the bottom and sides of the bank; these he attaches by some
glutinous material, that he clearly has the power of secreting, to the
different stems destined as pillars for his building. During this
operation he swims against the work already done, splashes about, and
seems to test its durability and strength; rubs himself against the tiny
kind of platform, scrapes the slimy mucus from his sides to mix with and
act as mortar for his vegetable bricks. Then he thrusts his nose into
the sand at the bottom, and, bringing a mouthful, scatters it over the
foundation; this is repeated until enough has been thrown on to weight
the slender fabric down and give it substance and stability. Then more
twists, turns, and splashings to test the firm adherence of all the
materials that are intended to constitute the foundation of the house
that has yet to be erected on it. The nest, or nursery, when completed
is a hollow, somewhat rounded, barrel-shaped structure worked together
much in the same way as the platform fastened to the water-plants; the
whole firmly glued together by the viscous secretion scraped from off
the body. The inside is made as smooth as possible by a kind of
plastering system; the little architect continually goes in, then,
turning round and round, works the mucus from his body on to the inner
sides of the nest, where it hardens like tough varnish. There are two
apertures, smooth and symmetrical as the hole leading into a wren's
nest, and not unlike it.
"All this laborious work is done entirely by the male fish, and when
completed he goes a-wooing. Watch him as he swims towards a group of the
fair sex enjoying themselves amidst the water-plants arrayed in his best
and brightest livery, all smiles and amiability; steadily and in the
most approved style of stickleback love-making this young and wealthy
bachelor approaches the object of his affections, most likely tells her
all about his house and its comforts, hints delicately at his readiness
and ability to defend her children against every enemy, vows unfailing
fidelity, and in lover fashion promises as much in a few minutes as
would take a lifetime to fulfill. Of course she listens to his suit;
personal beauty, indomitable courage, backed by the substantial
recommendations of a house ready built and fitted for immediate
occupation, are gifts not to be lightly regarded.
"Throwing herself on her side the captive lady shows her appreciation,
and by sundry queer contortions declares herself his true and devoted
spouse. Then the twain return to the nest, into which the female at once
betakes herself and therein deposits her eggs, emerging, when the
operation is completed, by the opposite hole. During the time she is in
the nest (about six minutes) the male swims round and round, butts and
rubs his nose against it, and altogether appears to be in a state of
defiant excitement. On the female leaving, he immediately enters,
deposits the milt on the eggs, taking his departure through the back
door. So far his conduct is strictly pure; but I am afraid morality in
stickleback society is of rather a lax order. No sooner has this lady,
his first love, taken her departure, than he at once seeks another,
introduces her as he did the first, and so on, wife after wife, until
the nest is filled with eggs, layer upon layer, milt being carefully
deposited betwixt each stratum of ova. As it is necessary there should
be two holes, by which ingress and egress can be readily accomplished,
so it is equally essential in another point of view. To fertilize
fish-eggs, running water is the first necessity; and, as the holes are
invariably placed in the direction of the current, a steady stream of
water is thus directed over them."
To the genus _Gasterosteus_ the largest species belong, those having
three dorsal spines, and the body typically fully covered with bony
plates. _Gasterosteus aculeatus_ inhabits both shores of the Atlantic
and the scarcely different _Gasterosteus cataphractus_ swarms in the
inlets from southern California to Alaska, Siberia, and northern Japan.
Half-naked forms have been called by various names and one entirely
naked in streams of southern California is named _Gasterosteus
williamsoni_. Its traits are, however, clearly related to its life in
fresh waters.
In _Pygosteus pungitius_, a type of almost equally wide range, there are
nine or ten dorsal spines and the body is more slender. All kinds of
waters of the north on both continents may yield this species or its
allies and variations, mailed or naked. The naked, _Apeltes quadracus_,
is found in the sea only, along the New England coast.
[Illustration:
FIG. 182.—Three-spined Stickleback, _Gasterosteus aculeatus_ L. Wood's
Hole, Mass.
]
[Illustration:
FIG. 183.—Four-spined Stickleback, _Apeltes quadracus_ Mitchill.
Wood's Hole, Mass.
]
_Eucalia inconstans_ is the stickleback of the clear brook from New York
to Indiana and Minnesota. The male is jet black in spring with the sheen
of burnished copper and he is intensely active in his work of protecting
the eggs of his own species and destroying the eggs and fry of others.
_Spinachia spinachia_ is a large sea stickleback of Europe with many
dorsal spines.
No fossil _Gasterosteidæ_ are recorded, and the family, while the least
specialized in most regards, is certainly not the most primitive of the
suborder.
=The Aulorhynchidæ.=—Closely related to the sticklebacks is the small
family of _Aulorhynchidæ_, with four soft rays in the ventral fins.
_Aulorhynchus_, like _Spinachia_, has many dorsal spines and an elongate
snout approaching that of a trumpet-fish. _Aulorhynchus flavidus_ lives
on the coast of California and _Aulichthys japonicus_ in Japan. The
extinct family of _Protosyngnathidæ_ is near _Aulorhynchus_, with the
snout tubular, the ribs free, not anchylosed as in _Aulorhynchus_, and
with the first vertebræ fused, forming one large one as in _Aulostomus_.
_Protosyngnathus sumatrensis_ occurs in Sumatra. _Protaulopsis
bolcensis_ of the Eocene of Italy has the ventral fins farther back, and
is probably more primitive than the sticklebacks.
=Cornet-fishes: Fistulariidæ.=—Closely related to the sticklebacks so
far as structure is concerned is a family of very different habit, the
cornet-fishes, or cornetas (_Fistulariidæ_). In these fishes the body is
very long and slender, like that of a garfish. The snout is produced
into a very long tube, which bears the short jaws at the end. The teeth
are very small. There are no scales, but bony plates are sunk in the
skin. The ventrals are abdominal, each with a spine and four rays. The
four anterior vertebræ are very much elongate. There are no spines in
the dorsal and the back-bone extends through the forked caudal, ending
in a long filament. The cornet-fishes are dull red or dull green in
color. They reach a length of two or three feet, and the four or five
known species are widely distributed through the warm seas, where they
swim in shallow water near the surface. _Fistularia tabaccaria_, the
tobacco-pipe fish, is common in the West Indies, _Fistularia petimba_,
_F. serrata_, and others in the Pacific. A fossil cornet-fish of very
small size, _Fistularia longirostris_, is known from the Eocene of Monte
Bolca, near Verona. _Fistularia kœnigi_ is recorded from the Oligocene
of Glarus.
=The Trumpet-fishes: Aulostomidæ.=—The _Aulostomidæ_, or trumpet-fishes
are in structure entirely similar to the _Fistulariidæ_, but the body is
band-shaped, compressed, and scaly, the long snout bearing the feeble
jaws at the end. There are numerous dorsal spines and no filament on the
tail. _Aulostomus chinensis_ (_maculatus_) is common in the West Indies,
_Aulostomus valentini_ abounds in Polynesia and Asia, where it is a
food-fish of moderate importance. A species of _Aulostomus_
(_bolcensis_) is found in the Italian Eocene. Allied to it is the
extinct family _Urosphenidæ_, scaleless, but otherwise similar.
_Urosphen dubia_ occurs in the Eocene at Monte Bolca. _Urosphen_ is
perhaps the most primitive genus of the whole suborder of
_Hemibranchii_.
[Illustration:
FIG. 184.—Trumpet-fish, _Aulostomus chinensis_ (L.) Virginia.
]
=The Snipefishes: Macrorhamphosidæ.=—Very remarkable fishes are the
snipefishes, or _Macrorhamphosidæ_. In these forms the snout is still
tubular, with the short jaws at the end. The body is short and deep,
partly covered with bony plates. The dorsal has a very long serrated
spine, besides several shorter ones, and the ventral fins have one spine
and five rays.
[Illustration:
FIG. 185.—Japanese Snipefish, _Macrorhamphosus sagifue_ Jordan &
Starks. Misaki, Japan.
]
The snipefish, or woodcock-fish, _Macrorhamphosus scolopax_, is rather
common on the coasts of Europe, and a very similar species (_M.
sagifue_) occurs in Japan. The _Rhamphosidæ_, represented by
_Rhamphosus_, an extinct genus with the ventrals further forward, are
found in the Eocene rocks of Monte Bolca. _Rhamphosus vastrum_ has
minute scales, short dorsal, and the snout greatly attenuate.
=The Shrimp-fishes: Centriscidæ.=—One of the most extraordinary types of
fishes is the small family of _Centriscidæ_, found in the East Indies.
The back is covered by a transparent bony cuirass which extends far
beyond the short tail, on which the two dorsal fins are crowded.
Anteriorly this cuirass is composed of plates which are soldered to the
ribs. The small toothless mouth is at the end of a long snout.
[Illustration:
FIG. 186.—Shrimp-fish, _Æoliscus strigatus_ (Günther). Riu Kiu
Islands, Japan.
]
These little fishes with the transparent carapace look very much like
shrimps. _Centriscus scutatus_ (_Amphisile_) with the terminal spine
fixed is found in the East Indies, and _Æoliscus strigatus_ with the
terminal spine movable is found in southern Japan and southwards.
[Illustration:
FIG. 187.—_Æoliscus heinrichi_ Heckel. Eocene of Carpathia. Family
_Centriscidæ_. (After Heckel.)
]
A fossil species, _Æoliscus heinrichi_, is found in the Oligocene of
various parts of Europe, and _Centriscus longirostris_ occurs in the
Eocene of Monte Bolca.
In the _Centriscidæ_ and _Macrorhamphosidæ_ the expansions of the
hypocoracoid called infraclavicles are not developed.
=The Lophobranchs.=—The suborder _Lophobranchii_ (λοφός, tuft; βραγχός,
gill) is certainly an offshoot from the _Hemibranchii_ and belongs
likewise among the forms transitional from soft to spiny-rayed fishes.
At the same time it is a degenerate group, and in its modifications it
turns directly away from the general line of specialization.
The chief characters are found in the reduction of the gills to small
lobate tufts attached to rudimentary gill-arches. The so-called
infraclavicles are present, as in most of the _Hemibranchii_. Bony
plates united to form rings take the place of scales. The long tubular
snout bears the short toothless jaws at the end. The preopercle is
absent, and the ventrals are seven-rayed or wanting. The species known
as pipefishes and sea-horses are all very small and none have any
economic value. They are numerous in all warm seas, mostly living in
shallow bays among seaweed and eel-grass. The muscular system is little
developed and all the species have the curious habit of carrying the
eggs until hatched in a pouch of skin under the belly or tail; this
structure is usually found in the male.
=The Solenostomidæ.=—The _Solenostomidæ_ of the East Indies are the most
primitive of these fishes. They have the body rather short and provided
with spinous dorsal, and ventral fins. The pretty species are
occasionally swept northward to Japan in the Black Current.
_Solenostomus cyanopterus_ is a characteristic species. _Solenorhynchus
elegans_, now extinct (with the trunk more elongate), preceded
_Solenostomus_ in the Eocene of Monte Bolca.
=The Pipefishes: Syngnathidæ.=—The _Syngnathidæ_ are very long and
slender fishes, with neither spinous dorsal, nor ventral fins, the body
covered by bony rings. Of the pipefish, _Syngnathus_, there are very
many species on all northern coasts. _Syngnathus acus_ is common in
Europe, _Syngnathus fuscum_ along the New England coast, _Syngnathus
californiense_ in California, and _Syngnathus schlegeli_ in Japan.
Numerous other species of _Syngnathus_ and other genera are found
further south in the same regions. _Corythroichthys_ is characteristic
of coral reefs and _Microphis_ of the streams of the islands of
Polynesia. In general, the more northerly species have the greater
number of vertebræ and of bony rings. _Tiphle tiphle_ is a large
pipefish of the Mediterranean. This species was preceded by _Tiphle
albyi_ (_Siphonostoma_) in the Miocene of Sicily. Other pipefishes,
referred to as _Syngnathus_ and _Calamostoma_, are found as fossils in
Tertiary rocks.
=The Sea-horses: Hippocampus.=—Both fossil and recent forms constitute a
direct line of connection from the pipefishes to the sea-horses. In the
latter the head has the form of the head of a horse. It is bent at right
angles to the body like the head of a knight at chess. There is no
caudal fin, and the tail in typical species is coiled and can hardly be
straightened out. _Calamostoma_ of the Eocene, _Gasterotokeus_ of
Polynesia, and _Acentronura_ of Japan are forms which connect the true
sea-horses with the pipefish. _Gasterotokeus_ has the long head and
slender body of the pipefish, with the prehensile finless tail of a
sea-horse. Most of the living species of the sea-horse belong to the
genus _Hippocampus_. These little creatures have the egg-sac of the male
under the abdomen. They range from two inches to a foot in length and
some of the many species may be found in abundance in every warm sea.
Some cling by the tails to floating seaweed and are swept to great
distances; others cling to eel-grass and live very near the shore. The
commonest European species is _Hippocampus hippocampus_. Most abundant
on our Atlantic coast is _Hippocampus hudsonius_. _Hippocampus
coronatus_ is most common in Japan. The largest species are _Hippocampus
ingens_ of Lower California and _Hippocampus kelloggi_ in Japan. Many
species, especially of the smaller ones, have the spines of the bony
plates of the body ending in fleshy flaps. These are sometimes so
enlarged as to simulate leaves of seaweed, thus serving for the
efficient protection of the species. These flaps are developed to an
extreme degree in _Phyllopteryx eques_, a pipefish of the East Indies.
[Illustration:
FIG. 188.—_Solenostomus cyanopterus_ Bleeker. Misaki, Japan.
]
[Illustration:
FIG. 189.—Sea-horse, _Hippocampus hudsonius_ Dekay. Virginia.
]
No fossil sea-horses are known.
The following account of the breeding-habits of our smallest sea-horse
(_Hippocampus zosteræ_) was prepared by the writer for a book of
children's stories:
"He was a little bit of a sea-horse and his name was Hippocampus. He was
not more than an inch long, and he had a red stripe on the fin on his
back, and his head was made of bone and it had a shape just like a
horse's head, but he ran out to a point at his tail, and his head and
his tail were all covered with bone. He lived in the Grand Lagoon at
Pensacola in Florida, where the water is shallow and warm and there are
lots of seaweeds. So he wound his tail around a stem of seaweed and hung
with his head down, waiting to see what would happen next, and then he
saw another little sea-horse hanging on another seaweed. And the other
sea-horse put out a lot of little eggs, and the little eggs all lay on
the bottom of the sea at the foot of the seaweed. So Hippocampus crawled
down from the seaweed where he was and gathered up all those little
eggs, and down on the under side of his tail where the skin is soft he
made a long slit for a pocket, and then he stuffed all the eggs into
this pocket and fastened it together and stuck it with some slime. So he
had all the other sea-horse's eggs in his own pocket.
"Then he went up on the seawrack again and twisted his tail around it,
and hung there with his head down to see what would happen next. The sun
shone down on him, and by and by all the little eggs began to hatch out,
and each one of the eggs was a little sea-pony, shaped just like a
sea-horse. And when he hung there with his head down he could feel all
the little sea-ponies squirming inside his pocket, and by and by they
squirmed so much that they pushed the pocket open, and then every one
crawled away from him, and he couldn't get them back, and so he went
along with them and watched to see that nothing should hurt them. And by
and by they hung themselves all up on the seaweeds, and they are hanging
there yet. And so he crawled back to his own piece of seaweed and
twisted his tail around it, and waited to see what would happen next.
And what happened next was just the same thing over again."
=Suborder Hypostomides, the Sea-moths: Pegasidæ.=—The small suborder of
_Hypostomides_ (ὑπό, below; στόμα, mouth) consists of the family of
_Pegasidæ_. These "sea-moths" are fantastic little fishes, probably
allied to the sticklebacks, but wholly unique in form. The slender body
is covered with bony plates, the gill-covers are reduced to a single
plate. The small mouth underneath a long snout has no teeth. The
preopercle and the symplectic are both wanting. The ventrals are
abdominal, formed of two rays, and the very large pectoral fin is placed
horizontally like a great wing.
[Illustration:
FIG 190.—Sea-moth, _Zalises umitengu_ Jordan & Snyder. Misaki, Japan.
(View from below.)
]
The species, few in number, known as sea-moths and sea-dragons, rarely
exceed four inches in length. They are found in the East Indies and
drift with the currents northward to Japan. The genera are _Pegasus_,
_Parapegasus_, and _Zalises_. The best-known species are _Zalises
draconis_ and _Pegasus volitans_.
No fossil species of _Pegasidæ_ are known.