{"id":572,"date":"2016-05-24T15:20:06","date_gmt":"2016-05-24T22:20:06","guid":{"rendered":"https:\/\/sites.evergreen.edu\/vms-spring\/?p=572"},"modified":"2016-05-31T23:07:06","modified_gmt":"2016-06-01T06:07:06","slug":"pleurobrachia-bachei-2","status":"publish","type":"post","link":"https:\/\/sites.evergreen.edu\/vms-spring\/pleurobrachia-bachei-2\/","title":{"rendered":"Pleurobrachia bachei"},"content":{"rendered":"

<\/h3>\n

Author – Chelsea Rabourn
<\/em><\/h3>\n

Common name: Sea Gooseberry<\/p>\n

Pleurobrachia bachei<\/em> is a gelatinous, tentaculate Ctenophore\u00a0found\u00a0in the epipelagic (surface) waters of the Pacific NW coast, from southeast Alaska to Mexico. Pleurobrachia<\/em>\u00a0bachei’s<\/em>\u00a0distribution\u00a0tends to be within 5 km of the shore and can reach 50 m deep, \u201cliving mostly in the upper 15 m in the day and at about 30 m at night.\u201d\u00a0(Hirota, 1974)<\/p>\n

\"Pleurobrachia
The phylum Ctenophora, to which Pleurobrachia<\/em> bachei<\/em> belongs, are a group of jellyfish look-alikes known as “comb jellies”. Though their name associates these creatures with jellyfish, jellies belong to the phylum Cnidaria and are thus evolution-wise an entirely different type of organism than comb jellies. Ctenophora and Cnidaria both possess bodies comprised of layers of jelly, but in Ctenophores these jelly-body layers are two cells deep and in Cnidaria they are one cell deep.<\/p>\n

Comb jellies are named for the many rows\u00a0of comb plates\u00a0that line their bodies. In Greek, Ctenophore means “comb-bearing”. Each comb row is comprised of thousands of cilia, which oscillate at rapid speeds and allow the Ctenophore to locomote. Fun fact: Ctenophores are the largest non-colonial animals that move\u00a0primarily\u00a0through the use of their cilia. As the cilia\u00a0oscillate\u00a0they refract light, which to the\u00a0human eye creates a mesmerizing,\u00a0colorful\u00a0display similar to a rainbow. To the untrained eye this beautiful display\u00a0gives a false appearance of\u00a0bio-luminescence. Some comb jellies do in fact\u00a0produce\u00a0bio-luminescence, but this is a separate process than the refraction of light on their combs, and Pleurobrachia<\/em> bachei<\/em> is not a\u00a0bio-luminescent species.<\/p>\n

Confusingly enough\u00a0Ctenophora and Cnidaria also exhibit some predation behavior that looks similar but is in fact different. Cnidaria\u00a0like jellyfish and sea anemones are popularly known for their\u00a0cnidocytes,\u00a0<\/strong>or explosive cells.\u00a0<\/em>An organism possessing\u00a0cnidocytes fires a\u00a0venomous\u00a0structure\u00a0from a subcellular organelle called a nematocyst upon contact with their prey.\u00a0This action produces a\u00a0sometimes painful and often paralyzing sting to the prey of\u00a0Cnidaria.\u00a0In other words,\u00a0Cnidaria\u00a0possess\u00a0“stinging cells”.\u00a0Jellyfish\u00a0are passive carnivores;\u00a0nematocysts line the long tentacles that flow from their\u00a0Medusa\u00a0form\u00a0and catch their prey\u00a0by stinging prey organisms upon contact. Comb jellies are also passive carnivores and possess tentacles for catching their prey. However, comb jelly tentacles do not possess\u00a0cnidocytes or\u00a0nematocysts. Instead they possess colloblasts, which shoot an adhesive substance rather than a venomous sting into their prey. Once a prey organism adheres to the tentacle of a Ctenophore, the comb jelly will pull the tentacle back to its body and consume its prey.\u00a0<\/p>\n

When searching for prey, P<\/em>. bachei<\/em> releases its two long tentacles and twirls its body until the tentacles unfurl and become free to flow behind and around its globular body. That achieved, P<\/em>. bachei<\/em> will passively drift until prey becomes stuck in their tentacles via the adhesive substance emitted by their colloblasts. When P<\/em>. bachei<\/em> is ready to eat, its tentacles will be slowly retracted toward its oral end for consumption.\u00a0(Greene et al., 1986)\u00a0<\/p>\n