Percomorph fishes and derivative orders

BIOLOGY OF FISHES
FISH/BIOL 311
BIODIVERSITY V, TELEOST EVOLUTION CONTINUED:
PERCOMORPH FISHES AND DERIVATIVE ORDERS;
MORPHOLOGY, ECOLOGY, AND CO-EVOLUTION
General topics:
1. Percomorpha: perches and perch derivatives
2. Order Lampriformes: ribbonfishes and their allies
3. Order Beryciformes: squirrelfishes and their allies
4. Order Zeiformes: dories and oreos
5. Order Gasterosteiformes: sticklebacks and their allies
6. Order Synbranchiformes: the swamp-eels
7. Order Scorpaeniformes: the mail-cheeked fishes
8. Order Perciformes: the perches
9. Order Pleuronectiformes: the flatfishes
10. Order Tetraodontiformes: triggerfishes, puffers, and their allies

1. PERCOMORPHA: THE PERCHES
AND PERCH DERIVATIVES
O.K., we still have lots
of fishes to describe,
all residing in this
largest of all groups,
the Percomorpha:
nine orders, 245
families, 2,212 genera,
and about 13,173
species. Nearly half of
all living fishes belong
to this group. We’ll
say something about
the following nine
orders:

RELATIONSHIPS OF THE MAJOR GROUPS
OF PERCOMORPH FISHES

2. ORDER LAMPRIFORMES: THE
RIBBONFISHES AND THEIR ALLIES
The lampriform fishes make up a strange,
morphologically diverse assemblage of
seven families, 12 genera, and about 21
species, ranging in body shape from short
and deep to highly elongate and eel-like.

All are marine and found
throughout the world in rather
deep water. Common names
include the opah, crestfishes,
ribbonfishes, oarfishes, tubeeyes,
and thread-tails.

Oarfishes, genus Regalecus, often mistaken for “sea serpents”

All share a peculiar and
unique modification of
the upper jaw that allows
for protrusion of both
premaxillae and maxillae
together: the maxillae,
instead of being
ligamentously attached
to the ethmoid and
palatine, slides in and
out with the highly
protractile premaxillae.

3. ORDER BERYCIFORMES:
SQUIRRELFISHES AND THEIR ALLIES
This is a very poorly understood
group of 16 families, 57 genera, and
about 219 species. Most believe that
it is probably an artificial assemblage
of unrelated taxa that are thrown
together for convenience only (i.e.,
we don’t know what else to do); there
are no convincing characters that tie
all members together. Common
names include pinecone fishes,
slimeheads, lanterneye fishes,
spinyfins, fangtooth, alfonsinos,
squirrelfishes, soldierfishes,
beardfishes, pricklefishes, bigscales
fishes, gibberfishes, and whalefishes.

4. ORDER ZEIFORMES: THE DORIES
AND OREOS
Another very poorly known
group of largely deep-water
marine forms found throughout
the world: 6 families, 21
genera, and only about 36
species. Common names
include dories, oreos, and
the boarfishes.

5. ORDER GASTEROSTEIFORMES:
STICKLEBACKS AND THEIR
ALLIES
This order consists of two rather different looking suborders: the
Gasterosteoidei, including the sticklebacks, tubesnouts, and their
allies; and the Syngnathoidei, containing the pipefishes, seahorses,
and their allies. In fact, these suborders are so different that many
ichthyologists prefer to treat them as separate orders. It contains 11
families, about 71 genera, and 278 species.

Suborder Gasterosteoidei: sticklebacks, tubesnouts, and the sand-eel;
primarily marine, but also brackish and freshwater; restricted to the Northern
Hemisphere; four families, nine genera, and about 14 species.
The recognition of only seven species in
the family Gasterosteidae fails to account
for the enormous genetic diversity and
biological species that exist in the
Gasterosteus aculeatus complex and
perhaps also in the Pungitius pungitius
complex; but the taxonomic and
systematic problems in assigning species
status to populations are formidable.

Suborder Syngnathoidei:
seamoths, pipefishes,
seahorses, trumpet-fishes,
cornetfishes, snipefishes,
shrimp-fishes, and ghost
shrimp-fishes; primarily
marine forms, but some are
found in brackish water, a few
in freshwater; distributed in
all tropical, subtropical, and
temperate seas of the world;
seven families, 62 genera,
and about 264 species.

6. ORDER SYNBRANCHIFORMES:
THE SWAMP-EELS
Synbranchiform fishes look just like
eels and up until the late 19th century
they were classified with the true eels.
But, the resemblance to anguilliform
fishes is only superficial. Known as
the swamp-eels, and highly evolved
as air-breathers, these are primarily
tropical and subtropical freshwater
fishes, although some species
occasionally enter brackish water;
they are distributed throughout west
Africa, Liberia, Asia, the Indo-
Australian Archipelago, Mexico, and
Central and South America; three
families, 15 genera, and 100 species.

The body is eel-like, pectoral and pelvic fins are absent, and the dorsal
and anal fins are reduced to a ray-less ridge. The caudal fin is vestigial
or absent as well.
The major distinguishing character, however, is found in the structure of
the gills: the gill openings on each side of the head are continuous with
each other beneath the throat, so that there appears to be a single
transverse slit.

7. ORDER SCORPAENIFORMES:
THE MAIL-CHEEKED FISHES
The scorpaeniform fishes, consisting of 26 families, 279 genera,
and about 1,477 species, are usually divided into five suborders,
but keep in mind that the classification of the order is very
provisional:
1. Suborder Scorpaenoidei
2. Suborder Platycephaloidei
3. Suborder Anoplopomatoidei
4. Suborder Hexagrammoidei
5. Suborder Cottoidei

Suborder Scorpaenoidei:
rockfishes, scorpionfishes,
stonefishes, velvetfishes,
pigfishes, and searobins; marine,
rarely brackish and freshwater,
found in all tropical and temperate
seas; six families, 82 genera, and
about 473 species.

Suborder Platycephaloidei: flatheads; marine, rarely brackish water,
confined to the Indo-Pacific Ocean; five families, 38 genera, and about 226
species.
Suborder Anoplopomatoidei: sablefish or blackcod, and the skilfish;
marine, North Pacific; a single family, two genera, and two species
(Anoplopoma fimbria and Erilepis zonifer).

Suborder Hexagrammoidei: greenlings, lingcod, and combfishes;
marine, North Pacific; a single family, five genera, and 12 species.

Suborder Cottoidei: sculpins,
poachers, oilfishes, lumpfishes,
lumpsuckers, and snailfishes; marine
and freshwater; all major oceans and seas
of the world; some freshwater forms with
highly restricted distributions, e.g., Lake
Baikal (Cottocomephoridae and
Comephoridae). Eleven families, about
149 genera, and 756 species.

The evolutionary relationships among these five suborders of the
Scorpaeniformes are completely unknown; they remain undefined
and serve only to group families thought to bear a closer relationship
with one another than with those placed in other suborders. The
arrangement of families and family boundaries is subject to much
disagreement.
Even common descent for the order as a whole is open to question.
There is only one character that provides evidence of shared
ancestry: the so-called suborbital stay, a posterior extension of the
third circumorbital bone (SO3) that extends across the cheek to the
posterior margin of the preopercle. Some argue rather effectively that
the suborbital stay differs so much among major groups that it could
well have evolved independently.

Suborbital stay

Suborbital stay

, 2002

8. ORDER PERCIFORMES: THE PERCHES
Now we turn to the great pinnacle of teleost evolution, the perciform
fishes, the largest and most diversified of all fish orders and, for that
matter, the largest order of vertebrates.
Perciforms are by far the dominate vertebrates in marine habitats as
well as the dominate fish group in many tropical and subtropical
freshwaters.
The classification of the order is largely unknown and highly
controversial: some ichthyologists would like to include other groups
(e.g., Scorpaeniformes, considering them to be percoid derivatives)
while excluding others (e.g., the Mugiloidei: mullets, barracudas, and
threadfins).

Common ancestry for the group is by no means certain. Most
families are basically very similar morphologically and remain
undefined (i.e., no unique derived characters are available).
Although they form a morphologically and ecologically diverse group
with all kinds of secondary losses and gains, the level of evolutionary
change, as contrasted with pre-acanthopterygian teleosts, can be
generalized (but there are many exceptions to these generalizations; e.g.,
many perciforms have cycloid scales):

The order Perciformes contains 20 suborders, 160 families, about
1,539 genera, and about 10,033 species. They constitute the dominate
marine shore fishes of the world: about 75% of all perciforms are
marine shore fishes, while about 14% (mostly cichlids and percids)
normally occur only in freshwater.
We can’t possible talk about all 20 perciform suborders, but we will
say a little about the largest and most diverse:
Suborder Percoidei: includes hundreds of common names; 79
families, 549 genera, and about 3,176 species. Of the 79 families, 26
contain a single genus, 10 have only a single species, and 10 have 100
or more species. The ten largest families—Serranidae, Apogonidae,
Sciaenidae, Percidae, Haemulidae, Carangidae, Chaetodontidae,
Pseudochromidae, Sparidae, and Lutjanidae—contain about 62% of
the species. By far, most are marine; only about 380 or 12% of the
species normally occur only in freshwater.

The Percoidei seems to be the basal evolutionary group from which the other
perciform suborders have been derived as well as the two perciform
derivative orders yet to be described.

RELATIONSHIPS OF THE MAJOR GROUPS
OF PERCOMORPH FISHES

9. ORDER PLEURONECTIFORMES:
THE FLATFISHES
In contrast to all the other groups we’ve talked about today, this order, the
Pleuronectiformes, is a well-defined, highly distinctive group. We have little
doubt that all members of the group were derived from a common ancestor—
together they form a monophyletic
assemblage.
Larval flatfishes are bilaterally
symmetrical and swim
upright, but early in their
development one eye migrates
across the top of the skull to lie
adjacent to the eye on the other
side. They then lie and swim
on the eyeless side.

The change involves a complex modification of skull bones, nerves, and
muscles that leaves one side of the fish blind and the other side with two eyes.
The upper side is darkly pigmented, whereas the under side is usually white.
Asymmetry is usually also reflected in other characters such as dentition,
scalation, and paired fins. Most species have both eyes on the right side and lie
on their left side (dextral) or have both eyes on the left and lie on the right
(sinistral).

In some species both dextral and sinistral individuals occur. Among the
latter species, the starry flounder, Platichthys stellatus, is especially
interesting because of the varying frequency of dextral and sinistral forms
that occurs over its range in the North Pacific: from California to southeast
Alaska the two forms (dextral and sinistral) are about equal in frequency;
around Kodiak Island and the Alaskan Peninsula about 70% are sinistral,
but almost 100% of the catch from Japan is sinistral.
Dextral Sinistral
The difference between sinistral and dextral starry flounders appears to be
largely under genetic control, but there are no convincing arguments for
any advantage to being left-eyed or right-eyed.

Most authors recognize 14 families of flatfishes, within which are
distributed about 134 genera and 681 species. There are three suborders:
1. Suborder Psettodoidei
2. Suborder Pleuronectoidei
3. Suborder Soleoidei
Suborder Psettodoidei:
spiny turbots; marine; west
Africa and Indo-Pacific
Ocean; a single family, one
genus, and three species.
Dorsal fin not extending
out onto the head; spines
present in the anterior parts
of dorsal and anal fins;
palatine bone well toothed.

Suborder Pleuronectoidei:
flounders (lefteye flounders,
family Bothidae; righteye
flounders, family
Pleuronectidae); marine,
present in all oceans of the
world; ten families, 95 genera,
and about 421 species.
Dorsal fin extending out onto
the head, reaching at least to
the eyes; dorsal- and anal-fin
spines absent; palatine
toothless.

Suborder Soleoidei:
tonguefishes and soles;
primarily marine, some
in freshwater; tropical
and subtropical seas;
two families, 38 genera,
and about 257 species.
Right- or left-eyed;
dorsal and anal fins far
forward and usually, but
not always, confluent
with a pointed caudal
fin. All fins without
spines.

Matthew Friedman, 2008. The evolutionary origin of flatfish
asymmetry. Nature, 454:209−212.

10. TETRAODONTIFORMES:
TRIGGERFISHES AND THEIR ALLIES
This last of the major groups of teleost fishes is, like the Pleuronectiformes,
a rather well-defined group. Many of the characters that tie
tetraodontiforms together are loss characters: many bony parts have
dropped out altogether or have become fused to other elements. For
example, all members of the group lack parietals, nasals, circumorbital
bones, and usually lower ribs; the posttemporal, if present, is fused to the
pterotic bone; the hyomandibula and palatine are firmly attached to the
cranium; and the maxilla is usually firmly united or fused with the
premaxilla.
Most ichthyologists recognize nine families, with approximately 101
genera and 357 species, all divided among two suborders:

Suborder Balistoidei: spikefishes, triplespines, leatherjackets, triggerfishes,
filefishes, boxfishes, cowfishes, and trunkfishes; marine; tropical
and subtropical seas and oceans of the world; five families, 72 genera, and
203 species.

Suborder Tetraodontoidei: puffers, porcupinefishes, and molas;
primarily marine, a few species entering and occurring in brackish and
freshwater; all tropical and subtropical seas and oceans of the world; four
families, 29 genera, and 154 species.