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In the animal kingdom we can find an immense variety of morphological structures, both in the group of vertebrates and in that of invertebrates. Bodies formed by bony or cartilaginous skeletons, animals with four, six, eight or up to fifty limbs, various protective structures or striking colors to indicate that they are poisonous species. Each and every one of them appears as adaptations to the environment and their way of life.
Among the morphological structures that many animals use to protect and aid locomotion, the carapace appears. We all know the shells of turtles, but … are these the only animals that have shells? By what other name can we find similar structures in nature? Keep reading this Green Ecologist article to learn more about the shell animals.
What is a shell and what types are there
The shell is a support and protection structure that many animals present. Its morphology is highly variable, depending mainly on whether it appears in vertebrate or invertebrate animals.
Internal skeletons
In vertebrate animals, as we well know, we find bony or cartilaginous internal skeletons, divided into trunk and extremities. In this case, the structure of the carapace is anchored to the vertebral column and the rib cage of the animal, being one more element of its internal skeleton.
External skeletons
On the other hand, there are external skeletons, which support proportionally less weight than endoskeletons of the same size. The main examples of exoskeleton are found among arthropods (group of invertebrates), in which the exoskeleton forms a shell that protects internal organs. In addition, we can find other ways to name it, such as, shell.
Among the arthropods, it stands out the group of crustaceans as shell or shell bearers in their anatomy. Although they are not the only invertebrates that present it, it is also the case of mollusks.
Let's take a closer look at these types of shell with some examples.
The shell of the turtles
Whether terrestrial, marine or freshwater, the internal skeleton of turtles develops its own strength as a shell, a unique trait among vertebrates. The shell of these reptiles acts as an envelope that protects internal organs from its body, allowing the head, front and rear legs, and tail to emerge from it.
- Turtles: in tortoises, such as the Mediterranean tortoise (Testudo hermanni), the shell is always dome-shaped, to prevent possible predators from catching them with their mouths or claws.
- Sea or freshwater turtles: On the other hand, in aquatic turtles, the shape of the shell is flattened, presenting a more hydrodynamic and lighter structure that allows them to be great swimmers, such as the loggerhead turtle (Caretta caretta) and the Florida terrapin (Trachemys scripta elegans).
The shell or shell of mollusks
Mollusks constitute one of the great phyla (Phylum Mollusca) within the animal kingdom. In it, the group of gastropods ("feet on the stomach"), that of bivalves ("two valves") and that of cephalopods ("feet on the head") stand out.
The soft body of mollusks is protected by a shell formed from cells that secrete calcium carbonate, which crystallizes outside in the form of a calcareous substrate. Thus, a resistant and essential structure is constituted to avoid the dissolution of the organism in acidic environments.
The shell of land and marine snails (Gastropods) is in one piece and is wound in a spiral, being normally open to the right side.
Regarding the group of bivalves, they present a carapace with two symmetrical lateral valves, which are closed by the action of one or two muscles and linkages that act as a hinge. Those commonly known as mussels (Mytilioida family), oysters (Ostreoida family) and clams (Veneroida family) are some of the many examples of marine bivalves.
Among the most surprising mollusks appears the nautilus (genus nautilus), a living fossil belonging to the group of cephalopods, whose outer shell is highly developed, is plano-spiral and totally septate.
The shell or shell of crustaceans
Crustaceans, as arthropods that they are, have an exoskeleton whose main component is chitin. This exoskeleton often acquires the character of a true shell, being mineralized with calcium salts, which gives it great hardness. Among the main crustaceans, we can find:
- Crabs
- Crawfish
- Lobsters
- Lobsters
Other animals with shells
Other of the most surprising animals with shells are:
- Pangolin
- Armadillo
- River crab
- Crab
- Sea urchin
- Crab
- Spider crab
- Hermit
- Shrimp
- Cockroach
- Beetle
- Galley
- flea
- Tick
- Moisture mealybug
- Turtle
- Conch
- snail
- ladybug
If you want to read more articles similar to +20 animals with shells, we recommend that you enter our Wild Animals category.
Bibliography- Ponder & Lindberg (1997). Towards a phylogeny of gastropod molluscs; an analysis using morphological characters. Zoological Journal of the Linnean Society, 119: 83-101.
- S. Gordillo (1995). Southern Mollusks: An Illustrated Guide. Zaguier and Urruty Publications, Buenos Aires. p. 115.
- T. Hirasawa, H. Nagashima & S. Kuratani (2013) The endoskeletal origin of the turtle carapace. Nature communications, 4.
