CrustaceanCrustaceans belong to the subphylum Crustacea (krəˈsteɪʃə), and form a large, diverse group of arthropods including decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods (insects and entognathans) emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea.
ArthropodArthropods (ˈɑːrθrəpɒd, (gen. ποδός)) are invertebrate animals in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a segmented body, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They are an extremely diverse group, with up to 10 million species. Haemolymph is the analogue of blood for arthropods.
InsectInsects (from Latin insectum) are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms.
Mantis shrimpMantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in length, while a few can reach up to . A mantis shrimp's carapace (the hard, thick shell that covers crustaceans and some other species) covers only the rear part of the head and the first four segments of the thorax. Varieties range in colour from shades of brown to vivid colours, with more than 450 species of mantis shrimp known.
ShrimpA shrimp (: shrimp (US) or shrimps (UK)) is a crustacean (a form of shellfish) with an elongated body and a primarily swimming mode of locomotion – typically belonging to the Caridea or Dendrobranchiata of the decapod order, although some crustaceans outside of this order are also referred to as "shrimp". More narrow definitions may be restricted to Caridea, to smaller species of either group or to only the marine species.
DragonflyA dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world. Adult dragonflies are characterized by a pair of large, multifaceted, compound eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body.
Simple eye in invertebratesA simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-lensed "compound eye", and is not necessarily at all simple in the usual sense of the word. The structure of an animal's eye is determined by the environment in which it lives, and the behavioural tasks it must fulfill to survive.
MantisMantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They have triangular heads with bulging eyes supported on flexible necks. Their elongated bodies may or may not have wings, but all Mantodea have forelegs that are greatly enlarged and adapted for catching and gripping prey; their upright posture, while remaining stationary with forearms folded, has led to the common name praying mantis.
OmmatidiumThe compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (singular: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea. Each ommatidium is innervated by one axon bundle (usually consisting of 6–9 axons, depending on the number of rhabdomeres) and provides the brain with one picture element.
LobsterLobsters are a family (Nephropidae, synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others. Highly prized as seafood, lobsters are economically important and are often one of the most profitable commodities in the coastal areas they populate.