What are the characteristics of the class malacostraca?
Distinguishing characteristics The head has 6 segments. Possess antennules, antennae and mouth parts. Usually have 8 pairs of thoracic legs and 8 thoracic segments. Possess compound stalked or sessile eyes.
What makes something a malacostraca?
: a major subclass of Crustacea including most of the well-known marine, freshwater, and terrestrial members of the group (as lobsters, crabs, shrimps, sow bugs, beach fleas)
How many appendages do malacostraca have?
The anteriormost five abdominal appendages are, almost without exception, biramous. In most malacostracans, the posteriormost abdominal appendages, if present, are flattened and form a tail fin with the telson. Orders are often categorized by the specialization of specific limbs and body segments.
Are crayfish and lobster related?
Crayfish, also called crawfish or crawdad, any of numerous crustaceans (order Decapoda, phylum Arthropoda) constituting the families Astacidae (Northern Hemisphere), Parastacidae, and Austroastracidae (Southern Hemisphere). They are closely related to the lobster.
What are problems Malacostraca face?
However, a number of problems make it difficult to determine the relationships between the orders of Malacostraca. These include differences in mutation rates in different lineages, different patterns of evolution being apparent in different sources of data, including convergent evolution, and long branch attraction.
Is malacostraca an order?
The class Malacostraca contains more than 29,000 living species and represents about half of all known crustacean species. Within the Malacostraca, Decapoda is the largest order, with more than 10,000 described species, followed by the orders Isopoda (10,000 species) and Amphipoda (6,200 species).
Where are malacostraca found?
Most malacostracans live in the marine environments,but a few are found in the freshwater and terrestrial environments. They occupy all three dimensions in the water column, such as crawling on top of the sediment, burrowing in the substrate, or swimming with the oceans currents.
Where can one find the members of the class malacostraca?
They are found worldwide from the intertidal zone to the deep ocean, all but one species being benthic (living on the seabed).
What are problems malacostraca face?
Which is the largest order of malacostracans?
Size range and diversity of structure. Within the Malacostraca, Decapoda is the largest order, with more than 10,000 described species, followed by the orders Isopoda (10,000 species) and Amphipoda (6,200 species). The other major orders have fewer than 1,000 species each. Most malacostracans are marine.
What kind of larva does a Malacostraca have?
Most metamorphosing malacostracans have a nauplius larva, but in many species eggs hatch into zoea larvae. Virtually every imaginable feeding strategy is demonstrated by at least one member of the class. Many malacostracans are strictly carnivorous, and are active hunters.
How are the legs of a Malacostraca modified?
Sometimes the head and thorax are fused into a cephalothorax, as in crayfish and crabs. The thoracic legs are variously modified for feeding, defense (with pincers), and locomotion. Abdominal appendages, often called pleopods, may be modified for swimming and sometimes respiration and care of eggs and young. Gary A. Wellborn,
Where does the chemical processing of Malacostraca take place?
The walls of this have chitinous ridges, teeth and calcareous ossicles. The fine particles and soluble material are then moved into the midgut where chemical processing and absorption takes place in one or more pairs of large digestive caeca.