Stomatopoda: Physical Characteristics - Case Study Example

Stomatopoda Taxonomically, the order Stomatopoda belongs to Crustacea phylum in the Malacostraca, and the sub Hoplocarida. Stomatopods (mantis shrimps) are basically predatory crustaceans which live in shallow seas (Stan & Debbie, Hauter, 2007). Around four hundred species of mantis shrimps has been identified and described world wide. The name Mantis Shrimp has evolved from the resemblance of the organism with the terrestrial organism named Praying Mantis with regard to the similarity in their prey catching method. Mantis shrimps are on an average thirty centimeters in length. As far its appearance is concerned it occurs in bright colors mainly from brown shades to bright neon colors. The physical features The stomatopods have a shallow carapace which covers its body leaving four thoracic somites uncovered. The shorter length of the carapace makes the rear part of the organism much longer. It has two somites in its head which are movable and bears stalked eyes and the antennules. (Juan, San A, 1998) Their eyes are highly developed with multiple lenses providing them excellent vision. Mantis shrimps have the ability to see shapes accurately under differing conditions of light. They even have three separated divisions in the eyes designed to see infrared, ultraviolet, polarized and visible light. Some body parts of the stomatopods like parts of antennae and tails reflect polarized light which facilitates the process of communication and helps to locate one another. (ALF,2008) The second thoracic limbs form massive spear-like or club-like grasping organs which are held close to the body, underneath the head and thorax. The organism has a large abdomen with large leaf like limbs called pleopods which bear branchial filaments. These are used for swimming and have gills facilitating respiration. Differently from other organisms which have their respiratory system within the thoracic region, the stomatopods have their respiratory system within the abdomen. A flat tail segment forms the end of the abdomen with a pair of appendages, or uropods which is fanlike (ALF,2008) There are obvious physical differences between the genders of stomatopods. Male stomatopods have long, slender sperm-transferral organs located at the bases of the last pair of walking legs. The distinguishing feature of the female stomatopods is that their reproductive organs appear as a narrow slit which opens underneath the body between the first pair of walking legs. (Juan, San A, 1998) Habitat The stomatopods live in shallow waters of the seas of tropical and subtropical climate. However a few species are found living in cooler waters of the sub-Antarctic. They burrow living tubes and cavities in the sand rubble or mud within the shallowness of the ocean and adapt themselves to living in these burrows. They also are found living in holes, cracks or crevices in rocks, and some times within the shells of snails or hermit crabs. Depending on the species, the animals while staying within the burrows close its entrance with rocks or with their raptorial limbs or tail Some of the species of Mantis Shrimp are domesticated in salt water aquariums. However there are myths and stories prevailing wherein these organisms had broken the aquarium glasses in which they were kept. (Stan & Debbie, Hauter, 2007). Most of the mantis shrimps species live individually in isolation from other individuals. They are only found together when males and females come together briefly during mating. Feeding Stomatopods are carnivorous in their feeding habit and are basically predators. Their food includes a wide variety. Generally they attack fish, mollusks, and other crustaceans for their food. However the choice of the food would highly depend on the molting cycle of the particular organism. Though they feed regularly, Mantis Shrimps can persist for few weeks with out food. They are considered as expert and clever hunters. Mantis Shrimp use specialized raptorial appendages to capture and conquer their preys. They use these appendages to either spear or smash their food by clubbing it strongly.(Juan, San A,1998) The strength of these animals is quite unique and some of the species have the strength to break a double layered safety glass. The blow by the appendage of Mantis Shrimps is calculated to have a power as equal as that of a 0.22 caliber bullet. “High-speed images reveal the formation and collapse of vapor bubbles next to the prey due to swift movement of the appendage towards it, indicating that the predator may use destructive cavitation forces to damage its prey”. (Patek,S N. Korff ,W L. & Caldwell R. L, 2004). Generally the Stomatopods are classified into two hunting categories which are spearers or smashers. The first category use their spear-like claw to silently stab soft tissued prey where as the second one use their strong appendages to hit and crack the harder bodied preys. Spearers do not actively go in search of their prey but lie at the entrance of their burrows in mud or sand and wait for a soft-bodied fish or shrimp to come within range. The smashers actively search for prey and hunt them. (Juan, San A,1998) Life processes & Behavior The activeness of mantis shrimps differs from species to species. Some species of mantis shrimps are nocturnal which are active only at night, especially on moonlit nights. Some others are diurnal or active during the day. There are species that are crepuscular as well, who come out only just after sunset or before sunrise. (ALF,2008) An integral part of the body of Mantis shrimp is its exoskeleton which provides them strength and protection. But the non flexibility of the exoskeleton limits the possibility of the development and growth of juvenile to adult. For them to grow they have to undergo the process of molting. Every couple of months, when the body becomes tight within the exoskeleton, Mantis shrimp splits the outer body covering and comes out of it leaving an empty mantis shrimp mold. (Juan, San A,1998) The newly emerged mantis shrimp needs protection till it develops a hardened exoskeleton. However the molting process is quite dangerous as it involves the shedding of integral parts like eye surfaces and inner linings of respiratory tracts. In order to protect themselves during this developmental stage, Stomatopods live in underwater cavities. (Juan, San A,1998) In the molting stage, mantis shrimp often will have to fight with others to ensure food and protection as there would be only limited supply of it. There are scientific evidences which indicate that mantis shrimp have evolved several strategies for competing with the opponents in order to maintain their cavities for protection. These strategies have evolved through the process of natural selection and acted on the behavior of mantis shrimp, leading to a variety of behavioral strategies for avoiding injury and defending ones cavity. (Juan, San A,1998) One of these most common behavioral acts is the speed by which it elevates its cephalothorax, extends its antennules and antennal scales, and spreads its raptorial and other walking appendages. These acts in totality increase the size of the animal and also expose the brightly-colored depression on the dorsal surface of the merus of the raptorial appendage. The extremity of the color and the apparent size of the animal would reflect the aggressiveness of the particular animal. This aggression is quite high in females guarding eggs. (ALF,2008) Mantis Shrimp performs deception which means that it would deliberately misrepresent its capabilities to win against a potential competitor. However there are proofs that these acts can turn detrimental to the performing organism itself in terms of the injury it may cause. This kind of reflexive behavior is not actually expected in animals with such extremely simplified nervous systems. However the natural environment of these animals and the necessity of the situations would have evolved the animals to behave accordingly. (Juan, San A,1998) Reproduction & mating The life cycle of Stomatopods have four broader stages which are egg stage, a series of free-swimming and plankton-feeding larval stages, a series of immature or sub adult growth stages and finally a sexually mature reproductive adult stage. The appearance of the larvae of Mantis Shrimp is of a scary predator with fearsome raptorial appendages. It has long slender body and bulging eyes. (Juan, San A,1998) The post-larvae are much similar to the adults. The larvae take almost three months to reach adulthood by passing through different developmental stages. The onus of the reproductive phase is mainly on the female. As individual organisms live in isolation from other, for the process of mating, one of the sexes will have to search for the other. However this search process turns detrimental as they may be fed by bigger animals on their way to reach their mate. (ALF,2008) Mating is done belly to belly. During the process of mating, the sperm is temporarily stored in seminal receptacles of the female. Later the female extrudes her eggs and fertilizes them, with the aid of an adhesive secretion from special glands on the thorax of the female. The hatching of the eggs are ensured by carrying it by the front thoracic appendages and constantly cleaning and turning it. It is noticed that the female does feed during the reproductive stage. (Juan, San A,1998) Though differed with species, many of the male species of mantis shrimps safe guard their female during breeding. After hatching, the larvae are carried away from the living area of the adults by water current. The hatching usually occurs when such ideal current occurs. The habitat of the larvae also differ with species as some species are benthic and start out on the sea bottom where as others are pelagic which immediately set off in the open sea. All species eventually develop into pelagic larvae and settle to the bottom as post-larvae. In some of the species a close relation between the lunar cycle and the female breeding cycle has been observed. (ALF,2008) Another general incidence during mating is that the female chooses a male who is physically bigger than her. After the female extrudes the eggs, the male finds another cavity to live in. In some of the species like smasher Haptosquilla, only the males go out in search of females where as this habit differs in different species. In this species the process of mating extends up to thirty minutes. Differently from other species, the female selects males who are smaller than them and another unique feature in this species is that the male does not guard the female during breeding. The size of the mates is not relevant in the case of spearer Oratosquilla and the sperm is stored for many months after mating. In some species, the partner is kept life long. In these cases they share the same burrow as well. (ALF,2008) Conservation None of the species of Stomatopods are currently reported to be at the verge of extinction. Therefore there is no conservation measures suggested currently for Mantis Shrimps. However it is vital to notice that Mantis shrimps are especially sensitive to pollution. This sensitivity is used as measure of the environmental health of the habitat by the environmentalists, as the presence or absence of Mantis shrimps directly refers to the organic purity of the habitat. (ALF,2008) The domestication of Stomatopods in aquariums needs due care. There are differential opinions among aquarists on the inclusion of Stomatopods in aquariums. They should be kept alone in a tank if not the tank is hugely big. Construction of tubes or cavities in sand, rubble or mud, look for holes or tunnels in the substrate should be done to create ideal habitat for Stomatopods. (Stan & Debbie, Hauter, ‘Mantis Shrimp,2007) Human Utility Some species of Mantis shrimps enjoy the status as a much appreciated pet in salt water aquariums. (Stan & Debbie, Hauter,2007) Squilla mantis is well known for its taste. There are efforts underway to domesticate and culture them in the Mediterranean and Adriatic seas so as to commercially use them as a human food ( ALF,2008). Works Cited Patek,S N. Korff ,W L. & Caldwell R. L. ‘Biomechanics:  Deadly strike mechanism of a mantis shrimp’, Nature (2004) 428, 819-820. ALF, ‘Mantis Shrimps: Stomatopoda - Physical Characteristics, Behavior And Reproduction, Mantis Shrimps And People’ Animal Life Resource, 2008, Animals.jrank, 5.Dec 2008, < http://animals.jrank.org/pages/1761/Mantis- Shrimps-Stomatopoda.html> Juan, San A. ‘Stomatopod Biology’, Juan, San A, 1998, Lurker’ Guide to Stomatopoda, 5.Dec 2008,< http://www.blueboard.com/mantis/bio.htm> Stan & Debbie, Hauter, ‘Mantis Shrimp: Pet or Pest?’, Stan & Debbie, Hauter, 2007, About.com, 5.Dec 2008 Read More