Biology, Phylogeny, and Ecology of the Stomatopoda
Stomatopods, also known as mantis shrimp, are an ancient group of marine arthropods that belong to the class Stomatopoda. There are approximately 350 species of stomatopods that have been discovered to date, ranging in size from 1 to 30 cm. (Caldwell 1975) Stomatopods are a group of crustaceans that belong to the class Malacostraca, along with familiar crustaceans such as crabs, lobsters, and shrimp. The malacostracans are defined by their unique bauplan, which consists of a segmented body divided into three distinct tagmata: the head, thorax, and abdomen. All living stomatopods are represented by four families: Squillidae, Lysiosquillidae, Gonodactylidae, and Bathysquillidae. (Caldwell 1975)
A typical stomatopod, Pseudosquilla ciliata
The head of the mantis shrimp is divided into 5 segments, each associated with a pair of appendages. Two pairs of antennae, the first of which is biramous, the second uniramous, make up the first two pairs of appendages. Both pairs of antennae are used for sensory purposes. Behind the antennae there are a pair of mandibles, a pair of maxillulae, and a pair of maxillae. (Haug et al. 2012) The mandibles are used for crushing food, and both the maxillulae and the maxillae are used to taste and manipulate food. The head also bears a pair of very complex compound eyes, each of which may contain up to ten thousand ommatidia.
The thorax of stomatopods consists of 8 body segments, which are also associated with their own pair of appendages. As in most crustaceans, the head and the thorax are fused and function as a single unit called the cephalothorax. (Srour 2011) A hard carapace covers most of the cephalothorax, with the exception of the last three thoracic segments. The first 5 segments of the thorax each have their own pair of maxillipeds. The mantis shrimp is most famously known for its enlarged second maxilliped, a highly developed raptorial claw that is used for killing prey. The claw very much resembles that of a praying mantis, hence the name mantis shrimp. The rest of the maxillipeds are finger-like appendages that are used to grasp objects, deliver food to the mouth, and dig burrows. Behind the maxillipeds there are three pairs of pereopods, or walking legs. (Ahyong and Lowry 2001)
The abdomen is made up of 6 body segments. The first 5 segments each have a pair of pleopods, which are biramous, flap-like appendages that are used for swimming. The gills are leaf-like and are carried on the outer branch of the pleopods. (Ahyong and Lowry 2001) The last segment contains a pair of flattened appendages called uropods that have been modified for swimming, as well as the telson, which is an extension of the last body segment that is covered with extremely hard armor and spines, developed for defensive purposes. The telson and the uropods together make up the tail fan. (Ahyong and Lowry 2001)
Stomatopods have developed a number of unique defining characteristics. One of their most renowned features is their highly advanced pair of compound eyes. Mantis shrimp are considered to have the most complex visual system in the animal kingdom. The range of light that is visible to humans is made up of three colors (red, blue, and green), because our eyes only have three different photoreceptors for detecting light. Our vision is better than that of dogs because they only have two different photoreceptors (blue and green), but not as good as birds, which have four (red, blue, green, and ultraviolet). The eye of the mantis shrimp, however, contains 16 different photoreceptors. (Srour 2011) They see many more colors than we do, as well as UV, infrared, and polarized light. Stomatopods are also the only known animals able to detect circularly polarized light. It has been suggested that this ability allows them to communicate through reflections of circularly polarized light, as well as to enhance contrast in turbid environments. (Chiou et...
References: 1. Caldwell, Roy L. 1975. Ecology and Evolution of Agnostic behavior in Stomatopods. Naturwissenschaften 62: 214-222
This is an article on stomatopods taken from a scientific journal
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