Acanthuridae

Author: Gianluca Casati

Classification  
La
family acanthuridae belongs to the suborder Acanthuridea
of the order Perciformes.
Sometimes the family Zanclidae
it is classified as a subfamily of the family
Acanthuridae.

Acanthurus lineatus (Photo Roberto Sozzani)

The family
acanthuridae It is divided into the following genres: Acanthurus,
Ctenochaetus, Paracanthurus, Zebrosoma, Naso e Prionurus. the first 4
they group together the true surgeonfish, those equipped with a mobile sting;
The last 2 are characterized by fish with spines or prickles
properties.
Nota * The 4 genera classified as surgeonfishes
are equipped with a mobile sting; those that do not fall into this classification
they are equipped with immovable spines.

Diffusion area
Most of the species of this
family proliferates in the tropical seabeds of the Indian Ocean and the
Peaceful.
They live, in small quantities, in the tropical areas of the ocean.
Atlantic and Caribbean Sea.

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Physical characteristics
-
Acanthuridae They are equipped with sharp spines enclosed in a groove, at the two
sides of the caudal peduncle.
When these blades are raised, they constitute
a valid tool for offense and defense, making them particularly dangerous
lateral attacks performed with the tail. Given the sharp shape of these
prickles, the Acanthuridae They are also called surgeonfish.
Means
the pectoral fins perform swimming movements of an undulating nature, sometimes
can reach high speeds. These limbs are used for cleaning
the eyes and even the head, a characteristic also found in other fish
such as Wrasses and some species of the family Nemipteridae.
For
move in certain directions, the Acanthuridae they use the fin
caudal as if it were a rudder.

 

Biotope
- Acanthuridae they live in the
coral reef, sometimes in correspondence with areas of undertow and strong
currents.
Some species can be found, albeit in minimal quantities, in
great distance from the reef.

Behavior in nature
Di
normally, they live in large packs where countless skirmishes take place
mostly intimidating nature: when 2 specimens come into close contact,
they tend to make some attacks, but without actually touching each other.
Typically, this
behavior is sufficient to distance the two contenders without consequences
harmful to both.
Therefore the specimens of this family are from
consider themselves relatively peaceful.

Acanthurus blochii (Photo Roberto
Sozzani)

Supply
In adulthood the
Acanthuridae They feed mainly on algae, and sometimes like
crustaceans and organisms of various types.
Their particular shape
dental, in the shape of a serrated spatula, allows them to shred even the
smaller plant samples.
Thanks to a thick muscular coat located
in the stomach, some species can swallow hard substances and sand, useful
to grind the hard cell walls of algae and make digestion easier
easy.
Conversely, species that do not have a muscular coat
robust, they avoid the ingestion of the above-mentioned substances.
Common to all
Acanthuridae, It is an elongated intestinal apparatus, formed as follows:
to promote the assimilation of substances
vegetables.

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Special features
In some species of
Acanthuridae, the color of the sting or groove, in which it is hidden, as well as
of the surrounding skin varies significantly; this chromatic variation
represents for the fish that has tested the tip of the sting, a sort of
warning to avoid further clashes in the future.
The species belonging to the
genres Nose e Prionurus they are devoid of stings, but
they compensate for the lack with the presence of immobile spines, sometimes
identifiable in small humped bone formations which, however, manage to
damage the opponent.
This different anatomical conformation of the
specimens Nose e Prionurus, it was enough for some
scientists who classified these last 2 genera into a single family
called Nasidae, classification that was promptly refuted
by most taxonomy experts.
The genres Acanthurus e
Paracanthurus they denote a high degree of vivacity which leads them to
swim very quickly and move with ease between obstacles of various sizes
nature.
Specimens of the genus Zebrosome e Ctenochaetus
on the contrary, they perform with calmer movements and tend to extricate themselves from the
corals with greater caution.
Fish of the genus Nose they live in the
waters above the coral reefs and, swimming slowly, they make
more measured movements than the species Acanthurus e
Paracanthurus.

 

Acanthurus coeruleus (Photo Roberto
Sozzani)

Playback
During the period of the
reproduction, they form large schools that swim together in a frenetic manner,
until at sunset, small groups of fish abandon the school to head
towards the surface, where they expel their eggs and sperm.
The expulsion of the
eggs and sperm is probably facilitated by the decrease in blood pressure
inside the swim bladder, this last operation made possible by the
rapid motion towards the surface.
The eggs float on the sea surface
with the help of a special oily drop and in a short time they hatch
revealing the larvae.
The development time of the latter is 26 hours and it is
manifests itself in various phases: initially the larva, just 2 mm long,
sustenance, for a few days, from the yolk sac, after which it evolves to
second stage called Acronurus.
After a few weeks, the larva
It takes the form of a tiny fish, about 20 mm long, which feeds
mainly of very small planktonic organisms.
Anatomically
speaking, the larva Acronurus it is not equipped with scales but with strips
horns placed vertically on the sides.
It has a transparent appearance and
It has poisonous rays in the first dorsal fin, in the anal fin, as well as in
the pectoral ones.
Many species of Acanthuridae (for example,
Acanthurus coeruleus, A. olivaceus e (A.pyroferus) they have a livery
yellow in color which changes chromatically permanently when the animal
reaches a length of 8 cm.
The radical difference in appearance between these
organisms and the Acanthuridae adults has induced, in the past, the experts of
taxonomy to classify larvae Acronurus in an independent genre
named with the term of the same name.
Similarly, the larvae of Nose immense
were associated with the Acanthuridae and were classified under the name
Keris.

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Species
Let's look in detail at the various best-known species of Acanthuridae.

Acanthurus Achilles

Length
Up to about 18 cm.
Biotope
In close proximity to
strong currents and rip currents and reefs
coralline.
Promotion
Especially around the atolls in the area
tropical Hawaii and, more generally, in the Ocean
Peaceful.
Behavior in nature
Lives in packs composed of
several dozen specimens.
Special features
The most specimens
small (less than 6 cm in length) do not have the typical red spot of the
adult fish.

Acanthurus coeruleus

Length
The maximum length is 37 cm.
Promotion
In the tropical part
western Atlantic Ocean and the Caribbean Sea.
They are spotted
also around Bermuda, Rio de Janeiro and New York, during the period
summer.
Biotope
The natural habitat of this species is the reef
coral reef with algae and, in general, areas characterised by vast meadows of
algae.
Behavior in nature
These fish have not developed a
stomach predisposed to the ingestion of solid substances or substances mixed with sand,
therefore they feed on algae and marine plants
hold.
Special features
There are chromatic differences in livery in
depending on the age of the specimens: the young ones, up to about 10 cm long, are
yellow color with a blue stripe in the dorsal and anal fins; those
the smaller ones have a light blue livery.

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Acanthurus japonicus

Length
Size up to about 18
cm.
Promotion
They certainly live around the Riu-Kiu islands and
in Philippine territorial waters.
Biotope
Like the others
kind of Acanthuridae, they swim in the areas marked by the
coral reef.
Behavior in nature
The specimens of this
species swim in large schools (composed of a maximum of 60 fish) and, very
rarely, in tiny groups of a few units.
Occasionally they tolerate the
presence of specimens Acanthurus glaucopareius within the
White.
Special features
This species is particularly similar to
Acanthurus glaucopareius, and, for this reason, in the past, it has been
mistaken for it.

Acanthurus leucosternon

Length
Maximum length 30 cm.
Promotion
The species lives in waters
of the Indian Ocean and the Indo-Australian Archipelago.
Biotope
-
specimens live in coral reefs (even dead ones) and in rocky areas where
the concentration of algae is more intense.
Behavior in nature
I
schools of this species are composed of a minimum of 6 fish and a maximum of
30.
They generally prefer calm waters and, in the case of young specimens,
They swim in very shallow waters near the coast, as well as in puddles
left by the low tide.
Similarly to other species, such as Acanthurus
glaucopareius e Acanthurus japonicus, they keep their distance
minimum of 40 cm from each other.

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Acanthurus lineatus

Length
It measures approximately 20
cm.
Promotion
This species proliferates in the ocean waters
Pacific and Indian Ocean.
Biotope
The specimens live in the
coral reefs and also like areas of undertow and strong currents in the
reef.
Behavior in nature
Algae and organisms derived from
they represent the food requirement of this species, whose specimens
they live in packs of a certain size.
 

Acanthurus sohal

Length
Up to about 40 cm long.
Promotion
It is present only in the waters of the Sea
Red.
Biotope
Like the others Acanthuridae, lives in the
coral reefs.
Behavior in nature
Lives in small groups
above the large umbrella-shaped corals, of which it prefers specimens
Acropora corymbosa e Acropora pharaonis and draws sustenance
from algae.
 

Naso brevirostris

Length
Up to 60cm.
Promotion
Red Sea, Indian Ocean and
Peaceful.
Biotope
Coral reefs and reefs
Death.
Behavior in nature
The young specimens (about 1.5 m long)
15 cm) feed on algae grazed in seagrass beds or near reefs
dead.
Adult fish appear to feed mainly on zooplankton and
They form large schools that swim in the areas above the reefs
coralline.
 

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Naso lituratus

Length
Up to 50cm.
Promotion
Red Sea,
Indian and Pacific Oceans.
Biotope
It lives in coral reefs,
mostly at great depths, in the open sea area.
Behavior in
nature
From what little we know, it seems that these specimens live alone.
or as a couple.
The presence of young fish (in groups) was confirmed
in shallow waters, which feed mainly on
algae.
 

Zebrasoma flavescens

Length
It measures just 18
cm.
Promotion
Pacific Ocean, mostly at the
Hawaiian Islands.
Biotope
It lives in coral reefs in non-marine waters.
shake.
Behavior in nature
The herds of this rare species,
because they are solitary animals or those that swim in pairs.
They earn their living
from algae and some microorganisms (invertebrates).
 

Paracanthurus hepatotus

Length
up to about 18
cm
Promotion
Pacific Ocean and
Indian
Biotope
Coral reefs
Behavior in
nature
It also lives in large herds of hundreds of
specimens.
As with most of the Acanthuridae, algae
represent the main subsistence objective.
 

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Zebrasoma scopas

Length
up to 18
cm.
Promotion
Pacific Ocean and
Indian.
Biotope
Coral reefs and lagoons with corals
solitary.
Behavior in nature
The youngest specimens (long
up to 12 cm) tend to live in packs of 20 individuals unlike
of adults who prefer a solitary life, in pairs or less frequently
in groups of no more than 5 units.
Algae are in the food crosshairs of
this species.
Special features
Several ichthyologists classify,
still today, Zebrosoma scopas as a variety of Zebrasoma
flavescens.

Zebrasoma veliferum

Length
Up to about 30
cm.
Promotion
Red Sea, Indian Ocean and Pacific Ocean.
Biotope

It lives in coral reefs.
Behavior in nature
Live
predominantly solitary: the word pack has no meaning for this
species that only occasionally live in pairs.
Special features
Tale
species differs from Zebrasoma desjardinii (Bennett classifies the species
propria, whose distribution area is in the Red Sea and in the vicinity of Mauritius
and Zanzibar) for the greater number of soft rays in the dorsal fin and in the
anal.
Small differences can also be noticed in the livery design,
particularly in the youth sector.

Zebrasoma xanthurum

Length
Up to 20cm.
Promotion
Mar
Red, Gulf of Aden and Sri Lanka (Ceylon).
Biotope
lives in barriers
coralline, especially in deeper waters, towards the sea
tightness
Behavior in nature
The search for algae and small
animals occurs during the day; in this phase the specimen swims alone or
in pairs.
The behavior in the late afternoon is radically different:
the fish gather in large numbers in large schools that stay above the
reef.

Zebrasoma desjardinii

Length
Up to about 30 cm.
Promotion
Mar
Red.
Biotope
It lives in coral reefs.
Behavior in
nature
It lives mainly alone: ​​the word pack has no meaning
meaning for this species which only occasionally lives in
couple.
 

 

We thank Roberto Sozzani for the photos provided.
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