Pleurobrachia bachei

From marinelife1011

P. bachei is a carnivorous species of planktonic ctenophora that can be common in large swarms.

Contents 1 Description and Morphology 2 Reproduction 3 Ecology and Behavior 4 Images 5 References

Description and Morphology

When full grown P. bachei can reach sizes of up to 2cm in body length, when its tentacles are fully extended it can reach sizes of up to 150mm.

The main body is which is composed of 99% water and biradialy symmetrical. It has a mouth and pharynx opening in the oral pole, exact opposite to the mouth on the aboral pole which include the anal pore, tentacle sheaths and the statocyst, which is a unique sense organ that controls equilibrium in the organism and movement of the cilia which in turn directs movement.

It has 8 comb rows comprised of fused cilia plates. Each plate consists of thousands of microcilia. The comb rows run like lines of longitude along the spherical body. These propel it through the water and beat rhythmic and fragmented patterns, which offer it a higher degree of control in the water.

It has two tentacles that extend from sheaths originating in the aboral hemisphere. The tentacles originate from a tentacle bulb at the bottom of the sheath. The tentacles are extended and act as a mechanism to hunt zooplankton and other planktonic organisms including larvae and fish eggs. The tentacles release a substance called colloblast which is a mucus that ensnares prey.

Reproduction

Ctenophores are hermaphroditic and the gonads of both sexes are located in the lining of the meridional canals. An adult can release up to 1000 eggs per day, and breeding can occur in a wide range of its entire life cycle. Gametes are shed to the sea through numerous tiny gonopores in the comb rows. Fertilization of the gametes is external. Development is direct without metamorphosis but includes a cydippid larval stage which resembles the adult form. They are planktonic their entire life cycle and have no sessile stage.

Ecology and Behavior

Common on both Atlantic, Pacific, and west Pacific coasts. Occurs worldwide. With a short-lived lifespan, around 4-6 months. This species occurs in pelagic and near shore environments, extending to considerable depth. P. bachei species are aggressive predators. This species and other ctenophores have the ability to have a considerable effects on copepod communitys and other planktonic organism communities if the conditions present the opportunity. P. bachei has predators which include A. aurita and other larger jellies.

Images

(Photo by: Dave Cowles July 2007)

(Photo by: Dave Cowles July 2007)

References

"Pleurobrachia - Encyclopedia of Life." Encyclopedia of Life. Web. 28 Feb. 2011. <http://www.eol.org/pages/49271>.

Pleurobrachia Bachei." Wikipedia, the Free Encyclopedia. Web. 28 Feb. 2011. <http://en.wikipedia.org/wiki/Pleurobrachia_bachei>.

Shonali T. Chandy and Charles H. Greene (Jul., 1995). Estimating the Predatory Impact of Gelatinous Zooplankton, Vol. 40, No. 5 (Jul., 1995), pp. 947-955. Published by: American Society of Limnology and Oceanography Article Stable URL: http://0-www.jstor.org.cals.evergreen.edu/stable/2838634

"BBC - Science & Nature - Sea Life - Fact Files: Sea Gooseberry." BBC - Homepage. Web. 28 Feb. 2011. <http://www.bbc.co.uk/nature/blueplanet/factfiles/jellies/gooseberry_bg.shtml>.

Harris, William H., and Judith S. Levey. The New Columbia Encyclopedia. New York: Columbia UP, 1975. Print.

Smith, DeBoyd L. A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae. Dubuque, IA: Kendall/Hunt Pub., 1977. Print.

"Pleurobrachia Bachei." WWU: On Campus. Web. 28 Feb. 2011. <http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Ctenophora/Pleurobrachia_bachei.html>.

"Across-shelf Predatory Effect of Pleurobrachia Bachei (Ctenophora) on the Small-copepod Community in the Coastal Upwelling Zone off Northern Chile (23° S) — J PLANKTON RES." Oxford Journals | Life Sciences | Journal of Plankton Research. Web. 28 Feb. 2011. <http://plankt.oxfordjournals.org/content/28/2/115.full>.