The fauna of planet Earth is wide, varied and interesting. Among those animals that make life in nature are crustaceans . They have very particular characteristics that differentiate them from other groups, although they are classified within the Arthropods. They are a very large type because there are at least 65 thousand discovered species. Their dimensions are different depending on the type, some only observable with a microscope. Its value in the ecosystem is fundamental and several are even part of the human diet with great nutritional and monetary value such as shrimp, lobsters and crabs.
What are crustaceans?
The animal crustaceans that are included within the order called Arthropoda (arthropods), that is to say, endowed with rigid or shell “exoskeletons” . In fact, the word that derives from the Latin “crustaceus” is translated as “having a shell or bark” . Despite the term, not everything is limited to it. In this category there are about 65 thousand different species, some with little known tiny sizes and others as popular as prawns.
- Characteristics of crustaceans
- Freshwater crustaceans
- Land crustaceans
- Microscopic crustaceans
- Crustaceans in danger of extinction
- Nutritional value
Characteristics of crustaceans
In general, crustaceans have certain characteristics that distinguish them from other orders or types, most of them related to their morphology. Some of them are:
- Their limbs are often divided in two , divided into branches and with pincers.
- They have a resistant exoskeleton (shell) which acts as a shield against predators and dangers.
- Its evolution is larval . That is, they are born as larvae and gradually go through stages in which they develop their parts and grow. The first stage is called “nauplius larvae” which is unique to crustaceans.
- Its head is segmented into five parts . With an elongated trunk in which the thorax and abdomen are located.
- When they are larvae they have only one eye, when they grow up they lose it, but some species keep it in adulthood. It is called the “naupliar eye”.
- Much of its organs are located in the abdominal cavity.
- Their legs are used to move and / or take their food.
- They have a first “denture” in the larval stage with which they chew their food and this is found in one of their two antennae. The provisional tooth structure is known as “naupliar arthrite”. It disappears when it is fully formed to make use of its jaw.
Research to determine the evolution of crustaceans and their ancestors has not stopped, as several details are still unknown in this regard. The “arthrite naupliar” is one of the data that has generated clues about its origins. It is estimated that they date from the Cambrian period, that is, they were created 500 million years ago. Canadaspis is the name of the oldest crustacean discovered by man. When analyzing the fossil, it was determined that it was part of the malacostráceos class, the same as lobsters.
The variety of crustacean species is immense, scientifically they are grouped into six different types:
- Remipedia : They are lowercase and primitive dimensions. The length they have is between 10 and 40 millimeters. They lack eyes.
- Maxillopoda : The main feature is that its abdomen is very small.
- Cephalocarida : They are the most primitive of all and small. The largest size they reach is just 4 millimeters.
- Ostracoda : it is distinguished by its soft shell and small size.
- Brachiopoda : They live in fresh water . They have small dimensions and are distinguished by the appendix that they show behind the head.
- Malacostraca : They are the best known, since most are consumed by man. It is also the broadest line, since it brings together about 40 thousand species.
It would be endless to name the more than 60 thousand species of crustaceans that exist, however, we can mention the most famous in world cuisine: crayfish, lobster, prawns, prawn, sea crab, lobster, crab, crab, barnacle and spider crab. . Other species that stand out for their curious shape and behavior are: ghost shrimp, pistol shrimp, lernaea, amphipods pram and sacculina.
Most of the crustaceans inhabit our oceans and seas. They are a key piece of balance in the maritime ecosystem . However, being such a large group, it is not surprising that there are species that live in almost any type of natural environment. Even in small puddles that arise after the rain , these animals can be found. There are fresh and terrestrial waters. Among the best known land species is the cochineal.
They mostly eat meat , a few feed on plants, but tastes are varied when it comes to eating. Therefore, depending on the species, they can be:
- Supensivores : They feed on organic matter that floats on water. Sea acorns stand out in this section.
- Scavengers : Certain crabs like hermits prefer to eat decomposing or lifeless animals.
- Parasites : They inhabit the body of other living animals and feed on it. They can cause illness or injury. An example is nudibranchs.
- Predators : They are those that go hunting, catch their prey and devour them to feed. Lobsters are on this list.
Certain crabs and other animals in the group feed exclusively on algae.
There are also species of crabs and other animals that are only herbivores feeding on algae that are attached to rocks. Some eat everything and act as fish cleaners, others crustaceans and animals, as they eat plant debris, dead skin and waste that accumulates on the outside of their marine companions.
The different types and groups of crustaceans reproduce sexually . In nature they are found in a male and female version. Males are provided with suitable appendages to transfer their sperm to females. Internally in them the fertilization process occurs. Later they are in charge of depositing their eggs in the water (so that the larvae hatch). There are also hermaphroditic species or that reproduce through parthenogenesis.
Some carry out migratory processes and others do not, but there are several species that inhabit the fresh waters of rivers, lakes, streams and ponds. Caribbean waters are great carriers of these animals, among which shrimp (tiger, guábara, palancú, buruquena, etc.), prawns and crabs stand out.
Among the most outstanding species that live on earth, the “coconut crab” (Birgus latro) stands out, which is also the largest land crustacean there is. It exceeds 4 kilograms in weight and reaches a length of up to 75 centimeters. The largest population is found on Christmas, an island in Australia . Mealybugs or oniscids are a much more common type of land-dwelling crustacean. They are found in common gardens and patios almost all over the world. They prefer humidity and darkness.
These tiny crustaceans are identified within several classes called cladocerans, copepods, misids, isopods, amphipods, and decapods . They serve as food for many small fish and play an important role in the ecological chain. Most are scavengers, but they also feed on vegetables, which keeps the waters clean. Some species are: daphnia, the cyclops and the red crab.
Crustaceans in danger of extinction
Crustaceans, like other animals, suffer the ravages of climate change and pollution or alterations to their habitat, which makes them susceptible to extinction or a significant reduction in their numbers. However, these have adapted very well to the different habitats offered by the Earth and are found all over the planet. One of the most documented species on the threats that surround it and point to its disappearance is the freshwater shrimp.
Crustaceans are a source of food for humans . Most stand out for their pleasant flavor and delicacy on the palate, which makes it the raw material of many dishes, especially Asian and Mediterranean cuisine. Its nutritional contributions due to its composition are similar to that of marine fish. They are also very healthy and recommended in diets, since they have a low fat content and caloric intake. For example, 100 grams of lobster contains 77 calories. Nutrients such as potassium, sodium and phosphorus predominate, which are essential for the human body. The recipes based on crustaceans are innumerable.