I. Background InformationScientific Classification:Kingdom: Animalia Phylum: Chordata Subphylum: Tunicata Class: Ascidiacea Order: Pleurogona Suborder: Stolidobranchia Family: Pyuridae Genus: Boltenia Species Name: Boltenia villosaCommon name(s): Spiny-headed tunicate, hairy sea squirt, stalked hairy sea squirt, bristly tunicateDescription: It is a solitary ascidian with an opaque, leatherytunic that is covered with spinelike projections or large, bristly hairs. Attached to the substrate by a stalk,which may be short or long. The tunic is reddish-orange or tan, with orange to red siphons. The siphonscan be hard to see and are short. Tunic bristles bear many secondary bristles that are irregularly distributed,or may be smooth.Size: The globular or heart shaped body is 1 to 3cm across, and borne on distinct stalk that is 1 to 4cmlong. It can be up to 10 cm tall, especially if on a long stalk, and a diameter that is about 2.5 cm.Geographical Range: Southern Alaska to San Diego, CA. It is most common on outer coasts.Depth Range: Low intertidal to 100 mHabitat: Attached to hard substrates in water with good circulationHow to Distinguish from Similar Species: The only other solitary ascidians with an opaque tunic and with spinelike projections have nodistinct stalk and the projections have side branches arranged in circles.Biology/Natural History: This species concentrates vanadium in its body tissues (500-750 ppm by dry weight, excluding thetunic). These are some of the highest levels of vanadium concentration seen in tunicates. Diet includescrustacean nauplii, mollusc veligers, and eggs. Predators include the seastars Dermasterias
imbricata and Orthasterias koehleri, and the predatory Oregon triton snail Fusitriton oregonesis . Sometimes containsthe symbiotic crab Pinnotheres pugettensis or the several species of copepods. Gametes are ripe year-round,but mainly in the summer. Fertilization is external. Settle 6 hours to 5 days after hatching. LIST OF REFERENCESMarine Biodiversity of British Columbia. 2012. Sea Squirts. Retrieved March 13, 2012 from http://bcbiodiversity.lifedesks.org/pages/20590Gary McDonald. 2010. Boltenia villosa. Retrieved March 13, 2012 from http://www2.ucsc.edu/ seymourcenter/ Inverts/Ascidiacea/Boltenia_villosa/Boltenia_villosa.html
II. Stages of Embryonic Development of Spiny-headed tunicate (Boltenia villosa) A. Unfertilized Egg T F The orange myoplasm is seen throughout the cortex of the egg. The test cells (T) float around the egg inside of the thick chorion. Attached to the chorion are a number of follicle cells (F). Most ascidian eggs have both test cells and follicle cells. B. Fertilized Egg, Zygote After fertilization, the myoplasm contracts toward the vegetal pole which will become the dorsa side of the embryo. The myoplasm marks where gastrulation will begin at the vegetal pole. C. Cleavage , 2-cell Stage 2-cell stage embryonic development of Boltenia villosa
D. Cleavage: 4-Cell Stage At the 4-cell stage, the polarity of the embryos is visible by the bright orange myoplasm at the posterior.E. Cleavage, 8-cell Stage 8 cell stage embryonic development of Boltenia villosaF. Cleavage, 16-cell Stage A 16-cell embryo shows the distinct bilateral cleavage in an ascidian embryo. The plane of the bilateral symmetry is in the center, anterior is up. At this stage, there are 4 myoplasm containing cells.
G. Cleavage, 32-cell Stage 32-cell stage of Boltenia villosaH. Cleavage, 64-cell Stage a) Animal hemisphere b) Vegetal hemisphere 64-cell stage of Boltenia villosa; (a) animal hemisphere and (c) vegetal hemisphere. The entire endoderm lines of cells are derived from only 10 precursor cells beginning at this stage.
I. Cleavage, 110-cell Stage a) Animal hemisphere b) Vegetal hemisphere 110-Cell stage of Boltenia villosa; (e) animal hemisphere contains the ectoderm cells and (g) vegetal hemisphere contains the endoderm cells.J. Gastrula Stage Gastrulation begins. The cells dive in (invagination) towards the interior of the embryo.K. Early Tail Bud Formation After gastrulation, an early tail bud forms. The tail bud embryo has a white head and the orange muscle cells surround the notochord in the posterior.
L. (A) Late Tail Bud Formation and (B) Tail Formation (A) Late formation of tail bud. (B) The tadpole larva just before hatching has undergone extensive convergence and extension, so now the tail wraps around the head and the white notochord cells are visible in the center of the tail.M. Tadpole a) Head b) Tail Tadpole finally develops. (a) Head portion and (b) tail portion of the tadpole. Palps (adhesive papillae) are found in the anterior portion of the tadpole.
N. Juvenile Stage O. Siphon After the larva swims for a period of time, the tail retracts during the Siphon of Boltenia villosa process of metamorphosis. The where water will enter. metamorphosing juvenile flattens down and makes a number of ectodermal ampullae that radiate out from the larva. LIST OF REFERENCESCell Dynamics. 2004. Embryogenesis in the Sea Squirt Boltenia. Retrieved March 13, 2012 from http://celldynamics.org/embryos/boltenia.htmlDassow, G. von. . 2004. Sea Squirts. Retrieved March 13, 2012 from http://celldynamics.org/celldynamics/courses/archive/2003gndcb/squirtweb/index.htmlSpring 2001 Undergraduate Apprenticeship at FHL. 2012. Boltenia villosa. Retrieved March 13, 2012 from http://faculty.washington.edu/bjswalla/fhl_sp01/boltenia.html
An image of Boltenia villosa ina larval stage. Frame-by-frame image of Boltenia villosa embryonic development.