Brine shrimp

Brine shrimp are small shrimp that live in salt water. They are the Artemia, a genus of aquatic crustacea which has changed little (externally) since the Triassic period.[1] They can often be found in saltwater ponds and marshes. They cannot live very long in fresh water. Brine shrimp avoid most types of predators, such as fish, because they live in waters of very high salinity: (25 parts per thousand). The optimum for Artemia is 100 to 150 parts per thousand.[2] The shrimp grow to be about one centimeter long. Females tend to be larger than males.

Anatomy

The brine shrimp's body has a head, thorax, and abdomen. A hard exoskeleton covers the entire body. The brine shrimp’s muscles are inside this exoskeleton, which is made of chitin. Their muscles are attached internally. They move by beating their tails and by the continuous movement of the legs along their body.

Brine shrimp circulatory and respiratory systems work together to spread oxygen through their body and remove extra salt. They breathe through gills on their feet. The oxygen taken in is carried through the bloodstream. The heart pumps the blood around the body. Brine shrimp have a protein called hemoglobin in their blood. This helps move the oxygen to cells around the body more easily. They need hemoglobin because oxygen levels can be very low in salty water. Then, the gills pump the excess salt, water, and carbon dioxide out of the body. More salt is pumped out through exocrine glands.

Reproduction

Males differ from females by having a larger second antennae, which are changed into clasping organs used in mating.[3]

Adult female brine shrimp ovulate about every 140 hours. In good conditions, the female brine shrimp can make eggs that almost immediately hatch. But in worse conditions, such as low oxygen level or salinity above 150‰, female brine shrimp make eggs inside cysts. They are metabolically inactive and can remain this way for two years in dry oxygen-free conditions, even at temperatures below freezing. While in cysts, brine shrimp eggs survive temperatures of liquid air (−190 °C or −310 °F) and a few can survive above boiling temperature (105 °C or 221 °F) for up to two hours.[4] Once placed in normal briny (salt) water, the eggs hatch within a few hours. The nauplius larvae are less than 0.4 mm in length when they first hatch. Brine shrimp have a biological life cycle of one year.

References

  1. ↑ Coolidge-Stolz M.D.E. et al. 2007. Life Science. Boston: Pearson.
  2. ↑ Sorgeloos P; P. Dhert & P. Candreva 2001. Use of the brine shrimp, Artemia spp. in marine fish larviculture. Aquaculture 200: 147–159 [1]
  3. ↑ Greta E. Tyson & Michael L. Sullivan (1980). "Scanning electron microscopy of the frontal knobs of the male brine shrimp". Transactions of the American Microscopical Society. 99 (2): 167–172. doi:10.2307/3225702. JSTOR 3225702.
  4. ↑ Whitey Hitchcock. Brine shrimp. Clinton High School Science

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