Monday, December 3, 2007

Sea Squirt, Tunicate (Sea Pork) and Parchment Tubeworm

November 30, 2007

It was a wonderful day on the beach. Still in the low 70s, the low tide revealed a lot, but, no great shells. In their place were a lot of tunicates and parchment tube worms.
The Tunicates have a common name of Sea Pork. Some types are called sea squirts because they will squirt water when picked up and squeezed. The picture of the brown sack like animal is a Sea squirt (I squeezed this one as I took the picture so you could see the water coming out of it).
“Sea squirts are immobile marine invertebrates which extract food (plankton and organic material) from seawater pumped through a brachial sac in their body cavity. They are called sea squirts because they squirt' seawater. The scientific name for this class of animals is Ascidiacea, so scientists often refer to them as 'ascidians'. They are part of a wider grouping (sub-phylum) of marine invertebrates called 'tunicates'. This sea squirt has been tentatively identified as a Styela plicata.
This invasive sea squirt is known by the name Pleated Sea Squirt. Its scientific name is Styela plicata (Lesueur, 1823).It is also known as the rough tunicate.
The pleated tunicate, Styela plicata is a solitary benthic (an aggregate of organisms that live in the bio-geographic region that includes the bottom of a lake, sea, or ocean and the littoral and supralittoral zones of the shore)(that’s got to be a super word to mean so much while saying it so succinctly !) tunicate believed non-native to the east coast and the western Atlantic, but occurring there in some abundance. The oval, upright body is covered with a tough and leathery cellulose-containing tunic, with numerous rounded warts and pleated grooves and a pair of short siphons.
Individuals range in color from light tannish white to gray. Thin red or purple stripes on the insides of the four-lobed siphons are evident as cross-shaped markings at the tips of the closed siphons. Individuals can be found singly or in groups (Carlton and Ruckelshaus 1997, Kaplan 1999, NIMPIS 2002, USGS, ISSG)
Styela plicata is a hermaphrodite, with individuals starting out as functional males and then becoming functional females later in life. Sequential hermaphroditism insures fertilization through outcrossing. Sperm and eggs are shed to the water column via excurrent siphons and fertilization is external. (Yamaguchi 1975, NIMPIS 2002).

Styela plicata is a sessile (permanently attached), benthic filter-feeder. The incurrent siphon takes water into a sieve-like pharyngeal basket that filters out food of the appropriate size class before water is pumped from the animal via the excurrent siphon. Styela plicata is among the most common introduced ascidian species worldwide. Despite considerable evidence supporting the contention that the organism is not native
to U.S. waters, Styela plicata was originally described in 1823 from specimens collected from the hull-fouling community on a ship in Philadelphia PA. The organism was reported from U.S. coastal waters ranging from North Carolina to Texas in the 1880s, and had been reported from California by 1915. It is thought to be native to the Indo-Pacific region. (Carlton and Ruckelshaus 1997, Lambert and Lambert 1998, Lambert 2001).
Styela plicata is a widespread and common fouler of buoys, pilings, nets and other floating or submerged manmade structures. It is also a common fouler of aquaculture cages, bags, and nets. If fouling is severe costly cleaning of culture gear is required to avoid still costlier loss of stocks (Da Rocha and Kramer 2005).

Kingdom Animalia
Phylum Chordata
Subphylum Tunicata Lamarck, 1816 -- ascidies, sea squirts, tunicates,
Class Ascidiacea
Order Enterogona
Suborder Aplousobranchia Lahille, 1887
Family Polyclinidae Milne-Edwards, 1841
Genus Aplidium Savigny, 1816
Species Aplidium glabrum (Verrill, 1871)

Aplidium glabrum This is the name of the purple tunicate pictured to the right. It is a colonial (colony) species that has zooids in a clear tunic. I had sent a note with photos to Gretchen Lambert who helps publish the Ascidian News out of Seattle WA and she is the one who tentatively identified this animal for me. It seems that it is very difficult to definitively identify the tunicate without dissecting the zooids from the animal and viewing them under a microscope. I'm such a novice, that I have no idea what each zooid looks like. I will continue to research and try to find out. ( I guess my first item of business is to buy a microscope - one that I can take pictures with!)
It is interesting that when I was researching information about this tunicate that scientists have been trying to determine the cytotoxicity to certain types of cancer tumor cells. The research is very promising for the pharmaceutical industry.

"The Chaetopterus parchment tubeworm feeds by fanning water through its home tube with its wing-like legs (fan parapodia). A bag of slime is excreted from two feeding legs (aliform notopodia). Water flows into this bag and out through its side, trapping tiny algal and mud particles. At its bottom end, the bag is continuously rolled up into a ball by the food cup. Once the ball is big enough, the bag is rolled up entirely and the compact ball of mucus transported to the mouth over a conveyor belt of whipping hairs (ciliated dorsal groove). " Dr. Floor Anthoni
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