Crustaceans. Arthropods Invertebrates Animal Kingdom. Wildlife. Fauna. Zoology. Fauna. Nature of Aragon Spain.

Crustaceans. Arthropods Invertebrates Animal Kingdom. Wildlife. Fauna. Zoology.

Nature of Aragon > Fauna

General characters

Crustaceans are mostly aquatic arthropods, although there are terrestrial species, in varied forms, there are some 26,000 living species.

Morphology of a typical Crustacean

The Body is divided into:
Cephalothorax or portion frequently covered by a shell.
Abdomen or pleon that can be formed by segments and ends in the furcation.
Head or cephalon with compound and pedunculated eyes and two pairs of antennae, mouth appendages with jaws, jaws and maxillipeds.
Abdominal legs or pleopods that serve as copulatory and ovigerous organs.
Ambulatory legs or pereiopods.


Other features

Larval forms of crustaceans are part of the marine "zooplankton."

Classification of Crustaceans


The entomostraceous or lower crustaceans whose body is formed by a variable number of segments are small in size, aquatic, and are part of the marine plankton. Some are parasites.


They have an elongated body. With numerous segments; A single pair of jaws. There is only the genus Hutchinsoniella.


They are crustaceans of small dimensions (2 to 10 mm) with bifid abdominal appendages, with gills. They may have a shell that covers their head and chest. Very developed antennas.

Simple and compound eyes. Some are marine and most freshwater.


They are very abundant in the aquatic plankton. They have antennas adapted for movement.

Females have saccules with eggs attached to the abdomen. They swim freely and some species are parasites of other animals.

One eye.


These small animals have a shell that covers them on both sides with two bean-shaped leaflets. The members employ them for swimming with the help of antennas and anténulas.
 They usually live in rocky lagoons near algae.


They are crustaceans that have a flattened body with a shield that covers the cephalothorax.  They are commonly known as "fish lice" because they are usually temporarily parasites of fish and amphibians. They have compound eyes, sucking mouth and suction cups with which they adhere to the victims, such as the larva of learnea cyprinacea parasite of the fish.


They are crustaceans with elongated body, large cephalic appendages and rudimentary thoracic appendages, absence of abdominal appendages There is only one genus, Derocheilocaris ronanei, which lives in the sand above the level of the tides.


They are more commonly known as barnacles and sea acorns. The larvae of these crustaceans, which pass through several larval forms, swim freely until they are fixed on a wooden rock, shell, etc., forming calcareous plates that cover them like a capsule.
They have well-developed thoracic limbs that beat the water and attract food and also serve as gills.
There are parasitic cirripeds such as Sacculina carcini, which adheres to the abdomen of some crabs and invades it internally with ramifications all over its body.


The malacostraceos or superior crustaceans are the most evolved, with the body divided into 20 segments. The shell almost always covers the cephalothorax.

They are divided into the following orders: leptostráceos, cumáceos, sincáridos, misidaceous, isopods, amphipods, hoplocáridos and eucáridos.


They are small (one centimeter) and drill tunnels in the sand. They have a shell and the abdomen can flex so that the urópodos clean your body.


They are very small (a few millimeters), very primitive, with a soft shell, pedunculated eyes, with 8 thoracic appendages and 6 abdominal ones. They live sunk in the sand of the coast.


They have no shell They have a cylindrical body with articulated segments. They live in freshwater and groundwater.

Spheroma serratum


They are aquatic and terrestrial crustaceans, known as moisture mealybugs.
They lack a shell and roll up into a ball. Some are parasites of fish and other aquatic organisms.
Others dig galleries in the wood causing serious damage.


They are small crustaceans very similar to shrimp and abound in ocean waters, and constitute an important food for numerous fish.

The thoracic limbs serve them for locomotion and breathing.
They are commonly known as beach fleas or bulges.
They have a depressed body, forelegs, and later jumpers.
They are semi-terrestrial and live under the sand of the beaches. There are also freshwater ones.
Galley (Sicylla mantis)


They are elongated and flattened, with a shield-shaped shell. They have eyes and mobile antennae. Front legs with sharp spines.
They are voracious and aggressive carnivores, so it is dangerous to touch them. They live between rocks and seaweed on the prowl of their prey. They measure from 5 to 30 cm.

Known by the name of galleys.


Eukaryids are medium and large sized crustaceans, usually called "crabs."

They are divided into two classes: Eufausiaceae and Decapods.

Decapods almost always have a shell fused with all segments of the thorax and have buccal appendages (maxillipeds), ambulatory legs, whose first pair usually has tweezers or "chelas", and abdominal pleopods. They have moving eyes located on a more or less long peduncle.
There are about 8,500 species of decapods, among which are the tasty "seafood".

Anomides are decapod crustaceans that are characterized by having an elongated and soft abdomen, asymmetric or irregular, without chitinous cover and, in the case of the hermit crab, adapted to accommodate it in the empty shell of a gastropod, keeping it in place by means of modified urópodos that are at the end of the abdomen.
As the animal grows, it searches for larger shells. Some seek association with other organisms for their defense, for example, with the actinias or anemones that they place on the shell.

By day When the hermit crab hides inside the shell, it blocks the entrance with its large clamps.

Other species of anomides:
Coconut palm crab (30 cm)
Galatea (5 cm)
Hairy Porcelain Crab (2 cm)
The coconut palm crab spends almost its entire life on dry land, in dens dug in the ground. From time to time he approaches the sea to deposit his larvae.

The Eufausiaceae

They are small prawns from the depths, with an almost transparent body, whose gills are not covered by the sides of the shell, like the other eukaryids. Some species have luminous organs. They feed on planktonic organisms.

The zooplankton or "krill"

Krill is the set of planktonic organisms, which form immense masses, from which most marine animals feed.
Its composition includes small lower crustaceans, larvae of many animals and large quantities of eufausiaceae.
The plankton mass floats near the illuminated surface during the night and travels very deeply during the day.


The macruros are decapod crustaceans that are characterized by having an elongated abdomen, with the tail formed by telson and urópodos.
They move using their last four pairs of legs and the first serves to cling the food. They swim backwards with rapid movements of the abdomen.

River crab
River crab.


1. Face 2. Anténulas 3. Antennas 4. Pedunculated eye 5. Cephalothorax 6. Shell 7. Abdomen 8. Rings 9. Telson 10. Caliper 11. Locomotive legs 12. Abdominal appendages or pleopods 13. Uropods 14. Mouth appendages 15. Gills 16. Nerve Rope 17. Brain ganglion 18. Green gland 19. Mouth 20. Chewing stomach 21. Liver 22. Genital Orifice 23. Bowel 24. Heart 25. Anterior aorta 26. Posterior aorta 27. Sternal artery 28. Ventral vessel 29. Year 30. Muscles 31. Genital Gland

Appendices of a macruro (crayfish)
crayfish 2 1. Antenulas
2. Antennas
3. Jaws
4. First pair of jaws
5. Second pair of jaws
6. First pair of maxillipedes
7. Second pair of maxillipedes
8. Third pair of maxillipedes
9. First pair of legs or "chelas".
10, 11, 12, 13. Four pairs of ambulatory legs
14, 15, 16, 17, 18. Five pairs of pleopods
19. Uropods
20. Genital holes
21. Copulatory stilettos
22. Year

Chewing pieces or Gastrolitos.
The stomach of the crayfish presents a series of masticatory pieces, called gastric windlass, and two calcareous masses called gastrolites.

Some species:

Stenopus hispidus
Cleaning crab
Langostinos and prawns
Lobster (Up to 1 meter)
Freshwater Shrimp
Lobster (Up to 60 cm)
Crayfish (30 cm)
Sea Cicada
Quisquilla (7 cm)

The crab egg originates a larva called zoea, but most crustaceans are born from microscopic larvae called nauplius.
Lobsters, prawns, lobsters and others are born in a more advanced state, such as mysis larva.
All larvae are part of the plankton.

The braquiuros belong to a suborder of crustaceans of the Decapod order (ten legs), which includes numerous species of crabs with the reduced abdomen and folded a large cephalothorax.
They do not have Uropods or caudal fan.
They live mostly in marine waters and some in fresh waters.
Many of them are edible with exquisite flavor.

Some species:

Pedrero crab (15 cm)
Bengal Crab (15 cm)
Long-legged sea spider (5 cm)
Sand crab (15 cm)
Blue land crab (45 cm)
Fiddler Crab (20 cm)
Japanese giant spider crab (3 meters wide)
Giant Crab (50 cm)
Mussel Crab (1 cm)
Swimmer crab (15 cm)
Crab (25 cm)
Nécora (10 cm)

Other information about fauna in Aragón:

A small list of species in Aragon would be the following:

Vertebrates Invertebrates








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