Identifying The Vase Tunicate

The Yellow Siphon Rings of Ciona intestinalis

The Gulf of Maine is home to several solitary ascidians with gelatinous bodies and translucent tunics.  These species may be difficult to distinguish from each other when individuals are very young, in masses of mature individuals growing in social groups, or when morphology is masked by overgrowth of colonial ascidians such as Didemnum vexillum or Diplosoma listerianum.  In Provincetown, the cryptogenic Ciona intestinalis and native Molgula sp. (probably manhattensis) are very common, whereas the invasive Ascidiella aspersa, which is common in other marinas along the coast, is less frequently seen. 

Ciona is best distinguished from Ascidiella and Molgula by its elongate, vase shape which is less prominent in small individuals, and it's lemon yellow siphon rings which are visible even when young. The siphon rings are also crowned with 8 orange pigment organs that are more subtle but can be discerned by close examination.  When the siphons close, muscles contract the rings and bring the pigment organs closer together at the bases of notches in the contracted opening. The pigment organs have an ocellus-like structure and probably function in light detection, although there must be additional receptors to detect light because individuals who have the siphons removed still grow towards the light.

 

Yellow Siphon Rings of Ciona intestinalis

Yellow Siphon Rings of Ciona intestinalis. From Adrian Gittenberger's Dutch Ascidians Homepage (www.ascidians.com).

 

 Orange Oral Pigment Organs and Yellow Siphon Rings of Ciona

Eight orange pigment organs are seen on these individuals and can be easily distinguished when the images are enlarged. (The Ciona look like they are wearing jackets of Didemnum vexillum).  Photo by Arne Kuilman. 

 Orange Oral Pigment Organs

Partially closed siphons with orange pigment organs brought

closer together at notches of the contracted opening.

  

During the process of researching images and information on the siphon rings, I came across a 2010 paper on the structure and regeneration of the siphons that was particularly interesting, filled with beautiful color photographs of the yellow rings and orange pigment organs, and available open access on the internet.

 

Auger, H, Y Sasakura, JS Joly, WR Jeffery.  Regeneration of oral siphon pigment organs in the ascidian Ciona intestinalis.  Develop. Biol. 339: 374-389, 2010 (Elsevier).

 

Auger and his research team examined oral siphon regeneration after surgical removal in Ciona intestinalis.  After removal, the oral siphon rapidly reformed (orange) oral pigment organs (OPO) at its distal margin prior to slower regeneration of proximal siphon parts. The pattern of 8 OPOs and siphon lobes was restored with fidelity after dissecting only the end of the siphon, but as many as 16 OPOs and lobes could be reformed after dissection at the base of the siphon (complete removal).  

 

The oral pigment organs, siphon lobes, and yellow pigment bands were the first structures to regenerate. The yellow pigment bands formed as extensions of the pigment organs, which grew together along the edge of the siphons. The rest of the siphon grew outward after the orange oral pigment organs and yellow pigment bands were formed.  They concluded that the pattern of oral pigment organ regeneration is determined by cues positioned along the longitudinal axis of the oral siphon.

 

 Anatomy and Histology of the Oral Pigment Band (PB) and Organ (OPO)

 Morphology of the oral siphon.  A, the tunic was removed and the pigment cells and muscles are clearly visible.  B, higher magnicaiton of yellow and orange cells.  D-E, the ocellus-like organs consist of receptor epithelials cells and an underlying cup-shaped aggregation of organge pigment cells.  OS, oral siphon; AS, atrial siphon; OPO, oral pigment organ; PB, (yellow) pigment band; RC, receptor cells; PC, pigment cells. 

 

PUBLICATIONS:

Hecht, S.  The photo sensitivity of Ciona intestinalis.  J. Gen. Physiol. 1: 147-166, 1918. 
Sutton, MF.  The regeneration of the siphons of Ciona intestinalis.  J. Mar. Biol. Assoc. UK.  32: 249-268, 1953.

Dilly, PN, and JJ Wolken.  Studies on the receptors in Ciona intestinalis.  IV.  The ocellus in the adult.  Micron, 4: 11-29, 1973.  
Chiba, S, A Sasaki, A Nakayama, K Takamura, N Satoh.   Development of Ciona intestinalis juveniles (Through 2nd Ascidian Stage).   Zool. Sci. 21: 285-298, 2004.

The Gulf of Maine

Created by the Glaciers - Regulated by its Currents



The Gulf of Maine is a large body of water in the Northwest Atlantic Ocean between Cape Cod, Massachusetts, and Cape Sable, Nova Scotia.  Cape Cod Bay, Massachusetts Bay, and the Bay of Fundy are all included within the Gulf.  The underwater features of the seabed were sculptured during the last ice ages 25,000 years ago when  sea levels were lower.  Glaciers scoured the earth and deposited rocks and rubble creating the current Northeast American landmass and several underwater banks (Georges, Browns, Jeffreys, and Stellwagen).  The Gulf is a semi-enclosed sea bounded to the south by Georges Bank and to the east by Browns Bank.  The coastline north of Boston is predominantly rocky due to the effects of glaciation, which stripped sedimentary soil away.  Georges and Browns Banks separate the Gulf from the warmer waters of the Gulf Stream.   Gulf of Maine waters are more strongly influenced by the Nova Scotia and Labrador Currents, making the Gulf waters significantly colder and more nutrient-rich than those found to the south.

 

Bottom Topography of the Gulf of Maine 

Bottom Topography of the Gulf of Maine.  The outer banks enclose several basins and shallow banks that were formed during the advance and retreat of the glaciers.  The Stellwagen Bank is probably an underwater extension of Cape Cod, is the site of the Stellwagen Bank National Marine Sanctuary, and is famous for whale watching.

 

Temperatures in the West Atlantic showing effect of the Gulf Stream

 The Gulf Stream brings warm water from the Caribbean north (red) along the Florida Coast and moves off the coast at Cape Hatteras.   In the summer, eddies and meanders from the Gulf Stream bring warm waters to the mid-Atlantic States and Long Island.  The Labrador Current brings cold water south from Nova Scotia to the Gulf of Maine.  Massachusetts and Cape Cod Bays form a transitional region between colder waters to the north and warmer waters from the Gulf Stream.

Sea Surface Temperatures Along the North American Coast 

Winter and Summer sea surface temperatures along the mid-Atlantic coast and in the Gulf of Maine.  In the winter, the Labrador Current pushes the warm waters from the Gulf Stream south and away from the Northeast coast.  In the summer, warm waters move north towards the Mid-Atlantic States, but the Gulf of Maine remains cooler due to water flowing south from Nova Scotia into the Gulf.

 

Currents in the Gulf of Maine

Within the Gulf, circulation is strongly influenced by the Nova Scotia Current which brings nutrient-rich waters through the Northeast Channel. This current helps drive the primarily counterclockwise circulation of the Gulf which brings cooler water from Maine to Massachusetts. The main currents circulate around the basins, allowing shallow waters along the coast and in Cape Cod Bay to warm up during the summer.  The currents are also influenced by fluctuations in river outflow, often enhanced during spring runoff, and by huge tides (over 10 feet in Provincetown).  Tidal variation increases in a northeast direction along the coastsline reaching a maximum in the Bay of Fundy with variations over 50 feet.

 

 Representative Salinity Levels in Massachusetts and Cape Cod Bays

Salinity in the Gulf of Maine.  Five-day averaged surface salinity (color) and currents (cm s⁻¹) (arrows) during spring blood periods in 1998 and 2000.  Units given in parts per thousand.  Fresh water from rivers on the northeast MA coastline north of Cape Ann (upper dark blue area) and in Boston Harbor (lower dark blue area) reduce salinity levels at the source and locations south of the rivers (because of water currents in the Gulf of Maine, see above).  The outer Cape, including Provincetown, are less affected by rivers because the watershed is limited and large tidal variations recirculate sea water in the marinas.

 

River Systems in Boston Harbor and Coastline North of Cape Ann 

Left, North of Cape Ann, the Merrimack River empties directly on the Coast.  The Parker and  Ipswich Rivers empty into Plum Island Sound whereas the Essex River drains into Essex Bay. 

Right, in Boston Harbor, the Charles and Mystic Rivers empty into the north harbor, the Neponset River joins the mid-harbor at Quincy, and in the south harbor, the Weymouth Fore and Back Rivers empty into Hingham Harbor.  

 

LINKS: 

GOMA - Gulf of Maine Area: Oceanography/Circulation.

Ecology of the Northeast U.S. Continental Shelf: Oceanography

New England Coastal Wildlife Alliance: The Gulf of Maine

Stellwagen Bank National Marine Sanctuary

Jiang, M., Z. Meng, S. Libby, and C.D. Hunt.  Influences of the Gulf of Maine intrusion on the Massachusetts Bay spring bloom: A comparison between 1998 and 2000. Continental Shelf Research. 27: 2465–2485, 2007. 

Coast Watch 2012

Marine Invasives Overview

It's a new summer season in New England and the CZM launched its Marine Invasive Species Program for 2012.  This summer, I'll be working with the Provincetown Center for Coastal Studies monitoring marinas in Provincetown and Wellfleet.  There are no new species classified as invasvie this year.  The collection of MIMIC ID Cards gives detailed descriptions of the 16 marine invasive species and the 7 potentially new species that have not yet reached the New England coast.  Guidelines are listed for distinguishing MIS species from related native species. 

MIMIC ID Cards for MIS Species (16 ID cards)

MIMIC ID Cards for Potential Invasives whose geographic ranges are spreading (7 ID cards)

Recently, I was searching the internet for information on invasive species and I came across several Wikipedia listings that described some of the issues around terminology for invasive species.  They contrasted the terms "invasive, introduced, immigrant, naturalized, exotic, alien, foreign, non-native, and non-indigenous".  For example, "invasive" and "alien" have unintended negative connotations that may not apply to all species, and "exotic" is also used for rare or unusual pets.  Many native and formerly invasive species are also "fouling" organisms that have spread beyond their native habitat (usually because of human activities).  Many invasives are simply in the process of geographic range enlargement or globalization because of new opportunities created by humans.  Marinas help facilitate the spread of MIS, especially for species that prefer quiet waters, because they are so numerous along the coasts of many countries.  At some point in time, the invasive species will most likely reach an equilibrium and at some point may be considered established.

Here is this year's list of species featuring images from recent web searches, a few of my own micrographs, and my impressions of the species from last season's monitoring:

Ascidians:

• Didemnum vexillum (beige colonial tunicate).  This species aggressively grows over everything - any flat surface including docks, solitary ascidians, mussels, algae blades.  Have I forgotten anything?  If so, include it too.

  

• Diplosoma listerianum (grey/green colonial tunicate) - Diplosoma is also a rapid grower and shows seasonal and regional variability with Didemnum. It is also a member of the Didemnidae family but lacks spicules.  It is distinguished by its smooth, slimy texture - like the body of an anemone, but it grows in a flat sheet.



• Ascidiella aspersa (translucent solitary tunicate) - The translucent, bumpy solitary ascidian.  Distinct from Ciona, another related species, and distinguished by its placement of siphons, which are far apart.  Ascidiella and Ciona can easily to distinguished from Molgula by the internal organs which can be seen through the tunic in young specimens. 

• Styela clava (club solitary tunicate) - Very common but can be missed when small and large individuals are frequently covered by Didemnum with only the brown Styela siphons sticking out.

• Botryllus schlosseri (star colonial tunicate) - Probably the most commonly studied adult ascidian as a model for colonial growth and tissue rejection.  Numerous color and pattern variants.

• Botrylloides violaceus (orange colonial tunicate)  - One of the most beautiful invaders/foulers.  Comes in many different shades of red/orange/peach.  Not as aggressive as the Didemnid colonials. 

Bryozoa:

• Membranipora membranacea (lacy encrusting bryozoan, posted Feb 12, 2012) - common on any flat, sturdy surface.  Co-exists with the native encrusting bryozoan.  Helpful to have a 30X magnifier. 

• Bugula neritina (purple bushy bryozoan)  - Similar to red algae in growth form but calcareous and distinctly different in structure.  Individual zooids may be discerned with a 30x magnifier.  

Anemones:

• Diadumene lineata (orange striped anemone, posted Dec 22, 2011) - seen in the "murky" waters of Wellfleet but not in the "sparkling" waters of Provincetown.  They're tiny gems. 

Bivalves: 

• Ostrae edulis (European oyster) - Not likely to be seen on docks.

 

Crustacea:

• Carcinus maenus (green crab) - Vary in size on docks - usually smaller than the size of a quarter.  It is distinguished from the Asian crab by its color, shape of the carapace, and solid coloring on its legs. 

• Hemigrapsus sanguineus (asian shore crab) - Easily identified by its striped legs and body.

• Palaemon elegans (European rock shrimp) - Present in Salem Sound.  Difficult to distinguish from native shrimp, especially when small before the blue bands on its legs and body fully develop.  Best to confer with the crustacean or MIMIC experts.



• Caprella mutica (Caprellid amphipod a.k.a. skeleton shrimp) - Very common living on algae and bryozoa. These small amphipods look and act like miniature preying mantis.  They hold tight to surfaces and do not "swim around" like typical amphipods and shrimp.  Not very compatible with fine nets where they need to be hand-picked off. 

 Algae:

• Codium fragile (green fleece) - Common in mid-late summer along dock water lines where they grow in masses. Characterized by branching growth pattern (right).

 

• Grateloupia turuturu (leafy red algae) - Arrives late season in the Gulf of Maine due to cold temperatures.

Links:
Pappal, A, Pederson, J, and Smith JP. Marine Invaders in the Northeast. Rapid Assessment Survey of Non-native and Native Marine Species of Floating Dock Communities.
Non-Native Species Invasions, Marine Biodiversity Wiki
Invasion Biology Terminology, Wikipedia
Invasive Species, Wikipedia
Introduced Species, Wikipedia

Ascidian Filter Feeding Mechanism

Styela clava as the model

Ascidians are suspension feeder that filter food particles such as phytoplankton from the surrounding sea water.  They transport water through the branchial sac (pharynx) which is perforated with small, ciliated slits, the stigmata.  The ciliary tracts on each side of the stigmata create a water current that pulls water through the branchial siphon into the branchial sac, through the stigmata, and into the atrial cavity from which the water leaves the body as a stream through the atrial siphon. When the water is transported across the branchial wall, suspended particles are trapped on a mucous net that is created by the endostyle, a mucus secreting structure on the ventral wall. 

Diagram of the Ascidan Filter Feeding Process

Diagram of the ascidian filter-feeding process. From Woods Hole Oceanographic Institute Website, 2005

The feeding mechanism is similar in different ascidians regardless of the complexity of the structures. Styela clava belongs to a group of solitary ascidians with a structurally complex branchial sac that is folded.  The folding increases the internal surface area, thereby increasing the number of stigmata and filtration capacity.   A mucus secreting organ on the vental surface, the endostyle, secretes a mucus net that moves across the surface of the sac by cilia on the pharyngeal bars.  The mucus net with its retained food particles then moves toward the esophagus. Thus, the amount of food consumed is determined by the concentration of food particles in the sea water, the efficiency of particle retention, and the volume of water transported. At a structural level, the endostyle is a longitudinal ciliated groove on the ventral wall and is composed of 8 different types of cells, a single band at the base of the groove with very long cilia that extend toward the surface of the groove and 7 pairs of bands on each side of the endostyle wall.

Diagram of the Branchial Sac of S. clava in Relation to the Digestive Tract

 The digestive tract of Styela clava from the left side with the internal surface of the branchial sac exposed.   bs, branchial siphon;  bt, branchial tentancles;  en, endostyle;  bb, branchial bar;  s, stigmata; i, intestine;  as, atrial siphon;  dt, dorsal tubercle;  r, rectum;  dl, dorsal lamina;  es, esophagus;  rb, retropharyngeal band;  st, stomach.

 Cross Section through the Branchial Sac of Styela clava

Section passes through the tranverse bars and not the stigmata.  The endostyle is located on the ventral surface.  Mucus and entrapped food pass along the ciliated branchial bars towards the dorsal lamina and then towards the esophagus.  bf, branchial folds;  d, dorsal lamina;  en, endostyle;  lb, longitudinal bars;  sv, subendostyle vessel.  

View of the Internal Surface of the Branchial Basket of Styela clava

Internal surface of the branchial basket of Styela clava by scanning electron microscopy (SEM) showing branchial fold (left 1/3 of image) and direct view of rows of stigmata, major and minor trasverse folds, and longitudinal folds.

Internal View of 3 Stigmata in the Branchial Sac of Styela clava

 

Internal surface of the branchial sac of Styela clava by SEM showing 3 stigmata, a major transverse fold at the lower left and a minor transverse fold at the upper right.  Densely packed cilia are uniform in length. 

Section through the Stigmata and a Branchial Bar of Styela clava

Section through the stigmata and a branchial bar of Styela clava. Cilia prevent food particles from leaving the branchial cavity but allow filtered sea water to pass through.  Ciliated bars transport food-containing mucus along the longitudinal and transverse bars to the dorsal lamina and thereafter to the esophagus. The cilia on the bars actually pull the mucus net forward, whereas the stigmata cilia act only as filters. sb, stigmata bar, ve, ciliated ventral epithelium;  ue, unciliated epithelium. 

Histologic Section through the Stigmata of Styela clava

Semi-cross section through a group of about a dozen ciliated stigmata ending on the left at a branchial bar.  The ascidian had contracted and stopped feeding, so the branchial sac is not in its normally expanded, feeding configuration.  Hemotoxylin stain.  

Cross section of the Endostyle of Styela clava

  Cross-sectional diagram of the different cell types of the endostyle of Styela clava.   The cells at the base of the groove have very long, flagella-like cilia.  The remaining cells are paired with semi-alternating glandular and ciliated cells.  

Histological Section of the Endostyle of Styela clava

Cross section through the endostyle of Styela clava.  The long cilia in Zone 1 can be seen extending part-way up the depth of the groove.  Hemotoxylin stain. 

PUBLICATIONS:

Armsworthy, SL, MacDonald, BA, & Ward, JE. Feeding activity, absorption efficiency and suspension feeding processes in the ascidian, Halocynthia pyriformis (Stolidobranchia: Ascidiacea): responses to variations in diet quantity and quality.  J. Exp. Mar. Biol. Ecol. 260: 41–69, 2001.

Ermak, T.H. Cell proliferation in the digestive tract of Styela clava (Urochordata: Ascidiacea) as revealed by autoradiography with tritiated thymidine. J. Exp. Zool. 194: 449-465, 1975.
Godeaux, J.E.A. Functions of the endostyle in the tunicates.  Bull. Mar. Sci. 45: 228-242, 1989.
Holmes, N.  Water transport in the ascidians Styela clava Herdman and Ascidiella aspersa (Mueller).  J. Mar. Bio. Ecol. 11: 1-13, 1973.
MacGinitie, GE. The method of feeding of Tunicates.  Biol Bull 77: 443-447, 1939.
Petersen, J, & Svane, I. Filtration rate in seven Scandinavian ascidians: implications of the morphology of the gill sac. Mar. Biol. 140: 397-402, 2002.
Petersen, JK, Mayer, S, & Knudsen, MÅ. Beat frequency of cilia in the branchial basket of the ascidian Ciona intestinalis in relation to temperature and algal cell concentration. Mar. Biol. 133: 185-192, 1999.
Riisgird, HU.  The ascidian pump:  properties and energy costs.  Mar. Ecol. Prog. Ser. 47:129-134, 1988.  (Studied in Styela clava). 

WEB LINK:
Shimek, RL. Tunicates or Sea Squirts: A Wet Link. Reefkeeping Online Magazine.

The Invasive Club Tunicate

An Abundant Resource for Ascidian Research

Styela clava and its cousin Styela plicata have been getting some pretty bad press over the last 10 years due to their circumglobal distribution and classification as Marine Invasive Species.  As a Styela biologist, I'd like to spend some time discussing some of the positive aspects to the Styela story. They may be be ugly ducklings on the outside (literally), but because of their recent world-wide distribution, they have also been the subject of scientific investigation by several research labs.  They are an attractive research model because they are readily available to researchers around the temperate world (in both hemispheres), and they are an important group of ascidians biologically in terms of their relationships to colonial botryllid species and other solitary ascidians.  In Asia (Korea), S. clava is part of the regional cuisine (Mideodok-chim) and is grown in aquaculture. The biology of Styela has become important for understanding diseases that have threatened commercially-cultured ascidians (soft-tunic syndrome in Halocynthia roretzi).  Inside, they are fascinating to study because their internal organs are bright orange and easy to examine.   S. clava is particularly useful because it is slender with a relatively thin, easily-cut tunic, whereas S. plicata is globular in shape and has a thick, less pliable tunic.  S. clava cohabitates with S. plicata in bays where their ranges overlap on both the East and West US coasts. 

Successful MIS Species:  S. clava and S. plicata

Styela clava and Styela plicata have made a home in Marinas and Bays around the world and are two of the most commonly studied Styela species.  In North America, both species have been established on both coasts for several decades.  S. clava has a more northern distribution than S. plicata, and the two co-habitate where their ranges overlap.  

Native American Styelids (Pacific Coast):  S. montereyensis, and S. gibbssi.

 

Styela montereyensis and Styela gibbsii, two Styela species from the Pacific coast were the two Styela research species of choice before the two MIS species became established in North America and Europe.  S. montereyensis and S. gibbsii have stayed within their ranges in the North American Pacific and prefer the cooler waters of the open coast. 

Styela clava showing orange-colored internal organs

   

Dissection of Styela clava with branchial sac (bs) on left and digestive tract on the right.  All the internal organs are located in the upper portion of the individual and not in the stalk whose function is essentially to raise the siphons and body above the growth of encrusting invertebrates and algae.  st, stomach; int, intestine;  os, oral siphon. as, atrial excurrent siphon. 

Diagram of the internal organs of Styela clava

Diagram of the internal organs of Styela clava.  Branchial sac, digestive tract consisting of esophagus, stomach, and intestine; reproductive organs in the body wall (both sides); and heart.   en, endostyle; bf, branchial folds; dl, dorsal lamina; rb, retropharyngeal band; ht, heart; es, esophagus; st, stomach; in, intestine; ov, ovary; t, testis.

Styela clava has a number of advantages as a model system for the study of solitary ascidians.  It is abundant, grows up to 4-5 inches (12 cm), and is easy to dissect.  It is adaptable for a wide range of studies and has a firm, flexible tunic that supports the internal organs during dissection.  In coastal marinas, S. clava individuals on docks show a range of sizes depending on the season and whether the substrate has been recently cleared.  During my 2011 MIS monitoring from Cape Cod to Salem Harbor, the population density was kept at a moderate level by competition with other encrusting invertebrates and colonial ascidian species, especially Didemnum vexillum and Diplosoma listerianum, which can aggressively overgrow solitary ascidians.  When fully mature, large individuals are easy to spot (unless totally covered by Didemnum).  However, small, young individuals may not be counted in the field when if they are not recognized. This is particularly important in marinas with new or cleaned docks. 

Young and Fully-Grown Individuals of Styela clava

Size distribution of Styela clava (the field is approx 5 inches [12.5 cm] high). The 6 smallest individuals were covered with Diplosoma listerianum, which was manually removed, revealing a smooth, light-tan tunic. The 3 medium sized individuals show typical bumpy brown corrugated tunic. The 3 largest individuals are covered with colonial ascidians and other attaching invertebrates. Left, complete coverage with Didemnum vexillum except for the siphons.  Center, patch-work collection of orange Botrylloides and Botryllus. Right, coverage by Didemnum and Botrylloides. Siphons and the upper body can contract within the tunic of the colonial species maintaining water flow and inhibiting overgrowth.

Styela has been used as a model system for studying filter feeding, the anatomy, histology, and ultrastructure of tunicates, cell biology (such as the function of the endostyle), blood cell formation, and the production of anti-bacterial peptides (styelins, clavanins, and clavaspirin).  The ovaries and testes are located in the body wall on both sides of the body instead of along the digestive tract and are arranged in radiating rows that are ideal for morphological and developmental studies.  Styela is a good control solitary ascidian for the study of coloniality in botryllid ascidians and is therefore important from an evolutionary point of view.  The styelids are located at a cross road linking more distantly related solitary ascidians such as Ciona, Ascidia, and Ascidiella, and other more closely related advanced ascidians such as Pyura (on the West Coast), Halocynthia (sea peach), and Boltenia (sea potato).  Some of these topics will be discussed in more detail in upcoming posts.

Granulocytes in Blood-Forming Tissue of Styela clava

Granulated blood cells in ascidians contain antimicrobial peptides that are important in fighting off bacterial and fungal infections.  The peptides are made in the cytoplasm and are concentrated into secretion granules that are released from the cell when they detect microorganisms.  This process is a part of the innate immune response and serves a similar function to the granulated blood cells in vertebrates that fight infections.  

Antibacterial Peptides from Blood Cell Granules of Styela clava

Styelins share amino acid sequences with each other and with cecropins in the domestic pig Sus scrofa domesticus (P1) and Drosophila virilis (Dv1).  Clavanins also share similar amino acid sequences.   

WEB AND LITERATURE SEARCH TERMS:

Styela, branchial sac, filter feeding, endostyle, stigmata, cilia, mucus, digestive tract, stomach, blood cells, hemocytes, granulocytes, cell renewal, reproduction, ovary, testis, innate immunity, styelin, clavanin, etc.

REFERENCES:

1.  Ermak TH. Cell proliferation in the digestive tract of Styela clava (Urochordata: Ascidiacea) as revealed by autoradiography with tritiated thymidine. J. Exp. Zool., 194: 449-466, 1975.

2.  Ermak TH. The hematogenic tissues of tunicates. In, The Phylogeny of Thymus and Bone Marrow-Bursa Cells, RK Wright and EL Cooper, Eds., Elsevier/North Holland, Amsterdam, pp. 45-56, 1976.

3.  Ermak TH. The renewing cell populations of ascidians. Amer. Zool. 22: 795-805,1982.

4.  Jiang AI, Lin J, Wang CH. Physiological energetics of the ascidian Styela clava in relation to body size and temperature. Comp. Biochem. Physiol. 149: 129-136. 2006.

5.  Kumagai A, Suto A, Ito H, Tanabe T, Takahashi K, Kamaishi T, Miwa S. Mass mortality of cultured ascidians Halocynthia roretzi associated with softening of the tunic and flagellate-like cells. Dis. Aquat. Org. 90: 223-234, 2010.

6.  Lambert G. New records of ascidians form the NE Pacific: a new species of Trididemnum, range extension and redscription of Aplidiopsis pannosum (Ritter, 1899) including is larva, and several non-indigenous species. Zoosystema 25: 665-67X, 2003 (includes an updated description of Styela clava).
7.  Lee IH, Cho Y, and Lehrer RI.  Styelins, broad-spectrum antimicrobial peptides from the solitary tunicate, Styela clava.  Comp Biochem. Physiol. 118B: 515-521, 1997.
8.  Lehrer RI, Lee IH, Menzel L, Waring A, and Zhao C.  Clavanins and styelins, alpha-helical antimicrobial peptides from the hemocytes of Styela clava.  Adv. Exp. Med. Biol. 484: 71-76, 2001.

9.  Lehrer RI, Tincu JA, Taylor SW, Menzel LP, and Waring J.  Natural Peptide Antibiotics from Tunicates: Structures, Functions and Potential Uses. Integr. Comp. Biol. 43: 313-322, 2003.
10.  Menzel LP, Lee IH, Sjostrand B, and Lehrer RI.  Immunolocalization of clavanins in Styela clava hemocytes.  Dev. Comp. Immunol. 26: 505-515, 2002.
11.  Raftos DA, and Cooper EL. Proliferation of lymphocyte-like cells from the solitary tunicate, Styela clava, in response to allogeneic stimuli. J. Exp. Zool., 260: 391–400, 1991.
12.  Raftos DA, Stillman DL, and Cooper EL. In vitro culture of tissue from the tunicate Styela clava.  In Vitro Cell. Dev. Biol. 26, 962-970, 1990.
13. Sawada T, Zhang J, and Cooper EL. Classification and characterization of hemocytes in Styela clava. Biol. Bull. 184:87-96,1993.
14. Thorndyke MC. Observations on the gastric epithelium of ascidians with special reference to Styela clava.  Cell Tiss. Res. Volume 184, 539-550, 1977.

15. Thorndyke MC.  Comparative studies on the effects of cholecystokinins, caerulein, bombesin 6-14 nonapeptide, and physalaemin on gastric secretion in the ascidian Styela clava.  Gen. Comp. Endocrinol., 1984. 

LINKS:

National System for the Prevention and Management of Marine Pest Incursions

Korean Mideodok-chim (Steamed Styela with beef, clams, vegetables, and ground rice over noodles)
iTunicate Newsletter (Invasive Tunicate Network in Alaska):  Plate Watch.  Includes a recipe for steamed Mideodok-chim.