Subphylum Urochordata

Cystodytes lobatus  (Ritter,1900)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polycitoridae

Compound tunicate; slab-like colony dense milky white, bluish, pale pink, lavender or pale orange, lacking embedded sand grains; 3-5 cm thick, often growing up into lobes. No zooids visible on surface of colony; microscopic discoid calcareous spicules in tunic; numerous mucus-filled bladder cells in tunic.

Common but seasonal (less apparent in winter); on rocks overgrowing other invertebrates & algae.

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species: other white compound tunicates usually have zooids visible at surface of colony.

Eudistoma molle  (Ritter, 1900)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polycitoridae

Compound tunicate; colony flattened dome, opaque white with bright red zooids; 1-2 cm thick; no sand grains embedded in tunic, zooids not arranged in systems; zooids with only 3 rows of gill slits.

Moderately common, especially in low intertidal around roots of surf grass; in kelp forests, on rocks with other sessile invertebrates and algae.

Geogr. Range: British Columbia to Carmel Bay
Synonyms: Archidistoma molle
Similar species: Aplidium solidum has a red rather than a whitish tunic; its zooids are red and arranged in irregular systems.

image: Ritterella pulchra (rt. of E.molle), Didemnum sp. (upper rt.), Bossiella (bottom left & cntr.), Eudistoma psammion  (lower middle  rt.)

Eudistoma psammion  (Ritter & Forsyth, 1917)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polycitoridae

Compound tunicate; slab-like colony thick & firm with embedded sand grains; brown, purple, sometimes reddish orange. Systems of ~8 zooids with common cloacal opening at top of low mounds; zooids with 3 rows of gill slits.

Abundant (purple & brown color morphs in photo); on rocks with moderate to strong water motion.

Geogr. Range: Washington to San Diego
Synonyms: Archidistoma psammion
Similar species: other compound tunicates have a more gelatinous rather than firm hard texture and usually lack the copious amount of sand present in E. psammion.

Image: Balanus crenatus (scattered over rocks), Reginella (to rt. of purple colony), pale orange on rocks is encrusting bryozoan

Eudistoma ritteri - no information available

Aplidium californicum  (Ritter & Forsyth, 1917)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polyclinidae

Compound tunicate; slab-like colony somewhat gelatinous & glossy 1-2 cm thick, highly variable in color: white, orange, yellow or brownish. Zooids small (6 mm long) arranged in irregular oval systems.

Common, on rocks interspersed with other  sessile invertebrates and red algae.

Geogr. Range:  British Columbia to Baja
Synonyms: Amaroucium californicum
Similar species:  Aplidium solidum is red, firmer & more robust with a thicker colony.

image: Watersipora (upper left), Rhodymenia californica (middle & lower left)

Aplidium sp. (?)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polyclinidae

Compound tunicate; thick slab-like massive colony to 10 cm thick or more, glossy & firm, sometimes lobed; bright white. Zooids clearly visible arranged in irregular systems.

Common in wave-exposed sites with stronger water motion.  Possibly a morph of Aplidium californicum, but its growth form is very much more robust.

Geogr. Range:  British Columbia to Baja
Synonyms: Amaroucium
Similar species: very similar to Aplidium californicum except for size & thickness; its zooids key out to A. californicum but colony form differs.

Image: Rhodymenia californica (red alga).

Aplidium solidum  (Ritter & Forsyth, 1917)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polyclinidae

Compound tunicate; slab-like colony 2-3 cm thick, tunic red with bright red zooids arranged in small irregular systems. Zooids average 12 mm long, but vary greatly.

Common, on rocks in kelp forest habitats.

Geogr. Range: British Columbia to San Diego
Synonyms: Amaroucium solidum
Similar species: red morph of Aplidium californicum is not so bright red and is less firm & robust than A. solidum. Eudistoma molle has white tunic with red zooids not arranged in systems.

Euherdmania claviformis  (Ritter 1903)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family

Colonial tunicate; zooids to 2-5 cm tall but only 2-3 mm diameter; tunics of club-shaped zooids colorless & translucent, often encrusted with sand.

Moderately common but inconspicuous, forms dense low-lying clusters mixed with other sessile inverts or grows in scattered groups among surf grass roots; low intertidal and subtidal on rocks.

Geogr. Range: central California to San Diego
Synonyms:
Similar species: zooids of Clavelina huntsmani are larger & more transparent with pink endostyle & dorsal lamina clearly visible through tunic.

Image: orange-red lobes may be Synoicum; light green spheres are Perophora annectens.

Polyclinum planum  (Ritter & Forsyth, 1917)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polyclinidae

Compound tunicate; colony a fleshy flattened lobe 10 cm tall attached by a stout fleshy stalk, olive green, tan or orange; zooids clearly visible in systems.  Commonly known as the elephant ear tunicate.

Common, on rocks in areas with moderate to strong water motion.

Geogr. Range: northern California to Baja
Synonyms:
Similar species: no other compound tunicate in Monterey region grows in stalked flattened lobes.

Synoicum parfustis  (Ritter & Forsyth, 1917)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Polyclinidae

Compound tunicate; colony few to many lobes 4-8 cm tall; orange, often with sand embedded in tunic; zooids in systems of ~12 around common cloacal pores located on bumps at distal ends of lobes.

Common, on rocks in areas with moderate to strong water motion, also in low intertidal among roots of surf grass.

Geogr. Range: northern California to San Diego
Synonyms:
Similar species: Orange sandy lobed tunicates are difficult to distinguish in the field. Ritterella pulchra grows in orange lobes, but lobes are more low-lying to substratum & zooids are not in systems.  Ritterella rubra grows in sandy lobes that are bright ruby red rather than orange.

Ritterella pulchra (?)  (Ritter, 1901)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Ritterellidae

Compound tunicate; colonies in short densely- packed lobes 1-2 cm across; orange.  Oral and atrial apertures of zooids clearly visible on raised projections at top of each lobe. Tend to be less sand-encrusted in Monterey.

Abundant, especially in kelp forests with only moderate water motion.

Geogr. Range: Alaska to central California
Synonyms: Sigillinaria pulchra
Similar species: Orange lobed tunicates are difficult to identify in the field.  Synoicum parfustis is orange sometimes with more elongate & more sandy lobes with zooids arranged in systems at distal end of lobes.

Ritterella rubra  Abbott & Trason, 1968
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Ritterellidae

Compound tunicate; colonies in short rounded lobes to 3 cm long; bright ruby red.  Oral and atrial apertures of zooids clearly visible at top of each lobe. Tend to be less sand-encrusted.

Common, especially in sites with stronger water motion.

Geogr. Range: Alaska to central California
Synonyms:
Similar species: Bright red color is distinctive; other similarly lobed species are orange or reddish-orange.

Image: Didemnum (lower rt, lower left), Metridium exilis ? (brown anemone)

Didemnum carnulentum Ritter & Forsyth, 1917
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Didemnidae

Compound tunicate; grows as small flattened lumps 1-2 cm across but only 1-4 mm thick, pale orange; numerous small oral apertures with fewer larger common cloacal apertures. Tunic with microscopic spiky calcareous spicules.

Very abundant throughout kelp forests in Monterey region, on rocks with other invertebrates and algae.

Geogr. Range: Oregon to Panama  
Synonyms:
Similar species: Didemnum sp. grows in continuous sheets, but otherwise looks identical to D. carnulentum.  Trididemnum opacum is thicker, grows in continuous sheets and is usually gray or brownish with fewer common cloacal apertures.

Didemnum  sp. (?)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Didemnidae

Compound tunicate; grows as a continuous sheet 10 cm or more across & sometimes >4 mm thick, pale orange to cream; numerous smaller oral apertures with fewer larger common cloacal apertures. Tunic with microscopic spiky calcareous spicules.

Abundant, on rocks in same locations as D. carnulentum.

Geogr. Range: British Columbia to central California  
Synonyms:
Similar species: Didemnum carnulentum looks the same but usually grows in separate flattened lumps rather than a continuous sheet and is usually thinner.

Trididemnum opacum  (Ritter, 1907)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Didemnidae

Compound tunicate; colony a continuous sheet 2-10 mm thick, gray-brown to pinkish; oral apertures of zooids are small dark dots; common cloacal apertures large and widely separated across tunic.

Abundant, on rocks with other compound tunicates, sessile invertebrates, and algae where water motion is moderate to strong.

Geogr. Range: northern California to San Diego
Synonyms:
Similar species:  Didemnum carnulentum and Didemnum sp. are yellow-orange, much thinner with more numerous common cloacal apertures.

Image: Didemnum (bottom cntr. & rt.), Corynactis is defending its space in upper left.

Trididemnum (?)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Didemnidae

Compound tunicate; colony a continuous sheet 2-10 mm thick, uniform dense gray; with numerous small oral apertures and fewer, more dispersed cloacal apertures across tunic.

Moderate to infrequent, on rocks with other compound tunicates, sessile invertebrates, and algae where water motion is moderate to strong.

Geogr. Range:  
Synonyms:
Similar species:  Trididemnum opacum is usually more brown rather than gray and tends to have fewer, larger cloacal apertures;  Didemnum sp. is yellow-orange, much thinner with more numerous common cloacal apertures.

Diplosoma listerianum  Herdman, 1886
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Didemnidae

Compound tunicate; colony very delicate & fragile 1-3 mm thick; transparent gray, olive or tan-yellow; numerous oral apertures with fewer large common cloacal apertures dispersed across a delicate fragile gelatinous tunic.

Moderately common, overgrowing other invertebrates and algae; also common in harbors and wharf pilings.

Geogr. Range:  British Columbia to San Diego
Synonyms: Diplosoma macdonaldi
Similar species: no other local compound tunicate is so delicately fragile and gelatinous; Trididemnum has a similar appearance, but is much thicker & robust.

Distaplia smithi  Abbott & Trason, 1968
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Holozoidae

Compound tunicate; clusters of flattened paddle- shaped lobes 3-4 cm tall, cream to yellow brown; zooids in linear systems with common cloacal apertures at end of flattened lobe & oral apertures on face of paddle; older zooids are eroded from terminal end of paddle & new ones bud near base.

Locally abundant but patchy in wave exposed sites; on rocks.

Geogr. Range: Alaska to Monterey Bay
Synonyms:
Similar species:

Distaplia occidentalis  Bancroft, 1899
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Holozoidae

Compound tunicate; colony dome or mushroom- shaped 1-3 cm, purple to pale orange, gray, yellow or cream; zooids in small round systems around common cloacal apertures.

Moderately common in wave exposed sites (e.g. Carmel Bay).

Geogr. Range: Alaska to Monterey Bay
Synonyms:
Similar species:

Image: Crisia (top cntr.), Corynactis (surrounding), sponge (upper left)

Clavelina huntsmani  Van Name, 1931
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Clavelinidae

Colonial tunicate; zooids nearly transparent 2-4 cm tall, 5-10 mm diameter; branchial basket with pink endostyle & dorsal lamina clearly visible through tunic.  Light bulb tunicate.

Abundant, but seasonally variable, regressing in  autumn & reappearing in late winter; on rocks among algae & other sessile invertebrates.

Geogr. Range: British Columbia to San Diego
Synonyms:
Similar species: Euherdmania claviformis is less abundant at kelp forest depths and is more elongate; pink endostyle/dorsal lamina not so  visible as in Clavelina.

Image: Celleporina (far left), Didemnum carnulentum (bottom cntr.), solitary Petaloconchus (green coiled tube, top cntr.)

Pycnoclavella stanleyi  Berrill & Abbott, 1949
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Aplousobranchia, Family Clavelinidae

Colonial tunicate; zooids tiny (1-2 mm); transparent with bright orange branchial basket. Base of colony obscured by encrusting sand grains.

Abundant, on low-lying rocks near sandy substrate with moderate to strong water motion.

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species: no other colonial tunicate in Monterey region has such tiny orange zooids.

Image: Calliarthron (lower rt. & cntr.)

Perophora annectens  Ritter, 1893
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Phlebobranchia, Family Perophoridae

Colonial tunicate; zooids transparent green 2-4 mm tall in grape-like clusters; zooids interconnected by basal stolons that grow along substratum.

Moderately common but inconspicuous, on rocks or blades of algae in sites with moderate to strong water motion.

Geogr. Range: British Columbia to San Diego
Synonyms:
Similar species: color & size of Perophora is distinctive in Monterey region.

Image: Didemnum (cntr.), Dodecaceria (black tufts of  tentacles throughout)

Corella willmeriana  Herdman, 1898
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Phlebobranchia, Family Corellidae

Solitary tunicate; tunic clear, glass-like with small white spots;1-5 cm tall; oral & atrial apertures terminal; gut on right side of body (instead of left like most other solitary ascidians w. a single body region).

Moderately common; in deeper sites with lower water motion.

Geogr. Range:  Alaska to central or southern California
Synonyms:
Similar species: No other solitary ascidian in Monterey has such a transparent tunic; the gut loop of Ciona lies below the pharynx rather than along its right side.

Ciona savignyi  Herdman, 1882
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Phlebobranchia, Family Cionidae

Solitary tunicate; tubular body 10-15 cm tall with  separate siphons at top; tunic translucent, delicate & soft, with white & yellow-orange pigment spots & visible longitudinal muscle bands.

Very common in protected waters such as shaded wharf pilings and marina floats.  Introduced from Japan.

Geogr. Range:  Alaska to southern California.
Synonyms: previously confused with Ciona intestinalis
Similar species: tunic of Ciona intestinalis is tougher, lacks white & orange spots & has a red spot at terminal end of sperm duct; Corella has gut loop along rt. side of pharynx while Ciona's gut loop is below pharynx.

Image: Ascidia ceratodes covered with Diplosoma listerianum (lower left), Botryllus schlosseri (lower rt).

Ascidia ceratodes  (Huntsman, 1912)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Phlebobranchia, Family Ascidiidae

Solitary tunicate with compressed body 3-4 cm long; tunic opaque & often overgrown with encrusting organisms; oral siphon projects anteriorly, atrial siphon from dorsal mid-body.

Very common, clustered in groups in protected waters such as wharf pilings and marina floats; also inside seawater systems.

Geogr. Range:  British Columbia to Costa Rica.
Synonyms:
Similar species:

Image: Serpula columbiana (lower rt.)

Cnemidocarpa finmarkiensis (Kiaer, 1893)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Styelidae

Solitary tunicate; tunic dome-shaped 2-4 cm long, glassy pink to pale red, with two obvious siphons.

Moderately common; on rocks with moderate to strong water motion.

Geogr. Range: Alaska to Monterey Bay
Synonyms:
Similar species:

Image: yellowish-tan crusts are bryozoan, drab orange crust (middle rt.) is sponge, Balanophyllia elegans (upper rt., middle left)

Metandrocarpa taylori  Huntsman, 1912
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Styelidae

Colonial tunicate; zooids dome-shaped 2-4 mm long, bright orange with obvious oral and atrial siphons; interconnected by basal stolons.

Moderately common, but inconspicuous, on rocks.

Geogr. Range: British Columbia to San Diego
Synonyms: Metandrocarpa michaelseni
Similar species:

Styela montereyensis  (Dall, 1872)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Styelidae

Solitary tunicate to 25 cm long (most are smaller); tunic reddish brown, leathery with longitudinal grooves & attached with an elongate stalk; oral siphon bent to always face upstream as animal oscillates in wave surge.

Abundant, on rocks among red algae with moderate to strong wave action. Stalks of older individuals often covered with hydroids & other fouling organisms.

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species: Boltenia villosa is also stalked, but it is smaller & has bristly spines covering its tunic.

Image: Hippoporina (lower left)

Botryllus schlosseri  (Pallas, 1776)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Styelidae

Compound tunicate; colony 1-2 mm thick, tunic transparent with orange-tipped blood vessels at margins (arrow); zooids 3-5 mm, yellow, orange, red, or gray-black in flower-shaped systems with common cloacal aperture at center; zooids undergo continual degeneration & replacement by asexual budding; systems usually with fewer than 20 zooids; colonies regress in winter &  grow vigorously in spring & summer.

Abundant in protected habitats such as wharf pilings and marina floats; introduced from Europe.

Geogr. Range: distributed worldwide
Synonyms:
Similar species:

Image: colony growing on tunic of solitary ascidian Ascidia

Boltenia villosa  (Stimpson, 1864)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Pyuridae

Solitary tunicate; to 10 cm long, attached by a short flexible stalk.  Tunic orange to red-orange, covered with thorny soft spines. Oral & atrial siphons sometimes partially obscured by spines.

Common, on rocks among other sessile invertebrates and red algae.

Geogr. Range: British Columbia to San Diego
Synonyms:
Similar species: no other stalked solitary tunicate in Monterey region is spiny.

Image: Calliostoma annulatum (bottom), Clavelina (rt. side), Scrupocellaria (upper left)

Pyura haustor  (Stimpson, 1864)
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Pyuridae

Solitary tunicate; body usually cryptic with only pair of rose-tinted siphons visible; tunic leathery, dark red with wrinkles & creases 2-4 cm long.

Moderately common, in crevices & other cryptic microhabitats.

Geogr. Range: Aleutian Islands to San Diego
Synonyms:
Similar species:

image: Haliclona enamela? (upper left), Crisia (top rt.),

Halocynthia igaboja  Oka, 1906
Phylum Chordata, Subphylum Urochordata, Class Ascidiacea, Order Stolidobranchia, Family Pyuridae

Solitary tunicate; oblong globose tunic without stalk, 2-5 cm long, covered with thorn-like fleshy spines; tunic brown to orange with red or orange siphons.

Uncommon; on rocks.

Geogr. Range: Alaska to California
Synonyms: Halocynthia hilgendorfi igaboja
Similar species: Boltenia villosa has a similarly spiny test, but it is smaller and  has a stalk, which is absent in Halocynthia.

image:  Dodecaceria fewkesi (upper left & across top); Serpula columbiana (lower rt); gastropods are all Calliostoma ligatum.