page_title: Mysida
section_title: Behavior
hierarchical_section_title: Mysida / Behavior
caption_attribution_description: Deutsch: Brackwasserkrebs, Spaltfußkrabbe (Mysis vulgaris), Zeichnung von Julius Fürst um 1895
context_page_description: Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this pouch and are not free-swimming characterises the order. The mysid's head bears a pair of stalked eyes and two pairs of antennae. The thorax consists of eight segments each bearing branching limbs, the whole concealed beneath a protective carapace and the abdomen has six segments and usually further small limbs.
  Mysids are found throughout the world in both shallow and deep marine waters where they can be benthic or pelagic, but they are also important in some fresh water and brackish ecosystems. Many benthic species make daily vertical migrations into higher parts of the water column. Mysids are filter feeders, omnivores that feed on algae, detritus and zooplankton. Some mysids are cultured in laboratories for experimental purposes and are used as a food source for other cultured marine organisms. They are sensitive to water pollution, so are sometimes used as bioindicators to monitor water quality.
context_section_description: Some species are benthic (living on the seabed) and others pelagic (living in mid-water), but most are found close to, crawling on or burrowing into the mud or sand. Most marine species are benthic by day but leave the seabed at night to become planktonic. Locomotion is mostly by swimming, the pleopods being used for this purpose. Some mysids live among algae and seagrasses, some are solitary while many form dense swarms. Mysids form an important part of the diet of such fish as shad and flounder. In general, they are free-living, but a few species, mostly in the subfamily Heteromysinae, are commensal and are associated with sea anemones and hermit crabs. Several taxa have also been described from different freshwater habitats and caves. Mysis relicta and its close relatives inhabit cold, deep lakes and have a diurnal cycle of vertical migrations.
  The majority of Mysida are omnivores, feeding on algae, detritus, and zooplankton. Scavenging and cannibalism are also common, with the adults sometimes preying on their young once they emerge from the marsupium. The pelagic and most other species are filter feeders, creating a feeding current with the exopods of their pereopods. This wafts food particles into a ventral food groove along which they are passed before being filtered by setae (bristles) on the second maxillae. Larger planktonic prey can be caught in a trap composed of the endopods of the thoracic appendages. Some benthic species, especially members of the subfamily Erythropinae, have been observed feeding on small particles which they collected by grooming the surfaces of their bodies and legs.
  Individual mysids are either male or female, and fertilisation is external. The gonads are in the thorax and are tubular in shape. Males have two gonopores in the eighth thoracic segment and a pair of long penises. The female gonopores are in the sixth thoracic segment and the oostegites are attached to the first to seventh pereopods to form a brood pouch. Mating usually takes place at night and lasts only a few minutes. During the process, the male inserts his penises into the marsupium and releases sperm. This stimulates the female and the eggs are usually released into the marsupium within an hour. Here they are fertilised and retained, development of the embryos in the brood pouch being direct with the young hatching from the eggs as miniature adults. The size of a mysid brood generally correlates with body length and environmental factors such as density and food availability. The age at which mysids reach sexual maturity depends on water temperature and food availability. For the species Mysidopsis bahia, this is normally at 12 to 20 days. The young are released soon afterwards, and although their numbers are usually low, the short reproductive cycle of mysid adults means a new brood can be produced every four to seven days.
caption: Neomysis integer
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