Did you know that the heaviest terrestrial arthropod that we can find in nature is a crustacean? We are talking about the coconut crab ( Birgus latro ), a species of hermit crab capable of opening with its strong pincer-shaped appendages the coconuts of the areas of the Indian Ocean and western Pacific in which it lives. It is one of the most striking species within the more than 26,000 species of crustaceans that have been discovered and classified to date. Undoubtedly, the heterogeneous group of crustaceans never ceases to surprise those who know their peculiar characteristics and variety of types.
In this AgroCorrn article we provide detailed information about crustaceans: what they are, types, characteristics and examples .
What are crustaceans
Crustaceans belong to the diverse group of arthropods , thus characterized by having a segmented body and by having numerous articulated appendages. In general, marine crustaceans are the most abundant, although there are also some species of freshwater or freshwater crustaceans, as well as terrestrial ones, although they do not present any type of special adaptation to this environment.
Crustacean animals are also one of the most characteristic groups within shell animals , the shell of crustaceans being of the calcareous type. It covers the head and part of the trunk, providing protection and it is common for them to carry out the molting process during the development and growth stages. In some species of crustaceans, this shell is bivalve, it protects the entire body of the organism and is called a shell.
In this other AgroCorrn article you can meet +20 animals with shells .
Types of crustaceans
The classification of crustaceans (including both marine, freshwater and terrestrial crustaceans), is based on the grouping of this great diversity of crustaceans into 6 fundamental types or classes:
- Branchiopods (small species whose head has a laminar shape).
- Remipedios (organisms that lack vision, inhabit deep caves of salt water).
- Cephalocarids (only includes 10 species of crustaceans that live exclusively in benthic areas).
- Maxilopods (they are small in size, with reduced appendages and abdomen. Many are part of the zooplankton).
- Ostracods (they have a bivalve shell that protects them. They are very small, sometimes microscopic).
- Malacostráceans (it is the most numerous group, it includes almost all the best known crustaceans, such as the decapod group and those commonly known as krill).
Characteristics of crustaceans
The main characteristics of crustacean animals are the following:
- The body of crustaceans is divided into segments (between 16 and 20), with 3 well differentiated parts: head (cephalon), thorax (pereion) and abdomen (pleon).
- On the head they have 5 pairs of appendages, including 2 pairs of antennae, a pair of mandibles and another 2 pairs of maxillae). Crustacean eyes can be simple or compound.
- The thorax includes the different segments for locomotion, respiration, feeding and defense.
- As for the abdomen, it has a variable number of appendages, usually shovel-shaped, used for swimming.
- The heart of crustaceans is usually long and tubular, with an arterial circulatory system.
- They breathe through gills or through the body wall. In this other post you can see +40 animals that breathe through gills .
- They have diverse and surprising sensory organs that allow them to detect pressure variations, water currents, capture sounds, as well as chemoreceptor and thermoreceptive organs.
- In terms of their diet, crustaceans can be predators, filter feeders, or even scavengers.
- The surprising capacity for regeneration of many crustaceans stands out.
How crustaceans reproduce
There are both dioecious crustaceans (with male and female individuals), as well as hermaphrodite crustaceans , that is, the same individual has male and female reproductive organs at the same time. Here you can learn everything about Hermaphroditic Animals: reproduction and examples .
Male individuals often have specialized thoracic appendages for grasping females during fertilization, which is always external. Later, the development of the new individuals undergoes a process of metamorphosis, going through several stages, from nauplius-type larvae to becoming adults.
Examples of crustaceans
The best known crustaceans are usually those that we are used to seeing and consuming in markets and shops. For this reason, from the Fund for the Regulation and Organization of the Market of Fishing Products and Marine Cultures (FROM), in Spain they commonly differentiate between short-bodied crustaceans and long-bodied crustaceans. Here are some examples of crustacean names :
- Short-bodied crustaceans: Atlantic crab ( Carcinus maenas ), crab ( Cancer pagurus ), spider crab ( Maja squinado ), barnacles ( Pollicipes cornucopia ) and crabs ( Necora puber ).
- Long-bodied crustaceans : prawns ( Parapenaeus longirostris ), shrimp ( Palaemon elegans ), prawns ( Penaeus kerathurus ), crayfish ( Nephrops norvegicus ), lobsters ( Palinurus elephas ) and lobsters ( Homarus gammarus ).
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