Opisthobranchs

Phylum Mollusca: Subtidal Sea Slugs & Allies

Molluscs comprise snails, sea slugs, bivalves, octopus, chitons. Second only to arthropods in numbers of species, molluscs have shown enormous evolutionary flexibility in their basic body plan of a head, a broad creeping foot, and a visceral mass containing their gut & internal organs.  ~100,000 living species. 

Class Gastropoda, Subclass Heterogastropoda

 Super Family Acteonoidea

• Rictaxis punctocaelatus

  Order Anaspidea

• Aplysia californica

  Order Cephalaspidea

• Navanax inermis

Order Nudibranchia
 Infraorder Doridacea

• Acanthodoris brunnea
• Aegires albopunctatus
• Cadlina luteomarginata
• Cadlina flavomaculata
• Diaulula sandiegensis
• Doriopsilla albopunctata
• Doris montereyensis
• Doris odhneri
• Felimida macfarlandi
• Limacia cockerelli
• Okenia rosacea
• Peltodoris nobilis
• Rostanga pulchra
• Triopha catalinae
• Triopha maculata

  Infraorder Cladobranchia, Aeolidida

• Aeolidia papillosa
• Flabellina iodinea
• Hermissenda crassicornis
• Hermissenda opalescens
• Phidiana hiltoni

 Infraorder Cladobranchia, Dendronotida

• Dendronotus albus
• Dendronotus iris
• Dirona albolineata
• Melibe leonina

 

Class Gastropoda, Subclass Heterogastropoda

 Super Family Acteonoidea

Rictaxis punctocaelatus  (Carpenter, 1864)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Superfamily Acteonoidea, Family Acteonidae

White shell to 20 mm with fine radial black lines; resembles a prosobranch gastropod.

Moderately common on mud or fine sand (e.g. Shale Beds). Preys on cirratulid polychaetes.

Geogr. Range: Alaska to Baja
Synonyms: Acteon punctocaelatus
Similar species: 

 

 

 

  Order Cephalaspidea

 

Navanax inermis  (Gosliner & Williams, 1972)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Euopisthobranchia, Order Cephalaspidea, Family Aglajidae

Tubular body with internal shell, to 125 mm. Tan to black with elongate yellow & blue markings

Infrequent in sheltered habitats in Monterey region, on fine sand, mud or eel grass. Feeds on other opisthobranchs, following mucus trails & swallowing them whole.

Geogr. Range: Central California to Baja.
Synonyms: Chelidonura inermis, Aglaja inermis
Similar species:

Image: Hermissenda opalescens about to be consumed.

 

 

 

  Order Anaspidea

 

Aplysia californica  Cooper 1863
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Euopisthobranchia, Order Anaspidea, Family Aplysiidae

Sea hare, to 400 mm; red, brown or greenish with reticulating dark lines and irregular spots.

Sporadically common on red algae in kelp forests or on mudflats. Abundance varies greatly from year to year; more common toward southern California. Herbivorous; digestive gland concentrates toxins making animals unpalatable; when disturbed, secrete a dark purple ink.

Geogr. Range: northern California to Baja
Synonyms:
Similar species:

 

 

 

Order Nudibranchia

 Infraorder Cladobranchia, Aeolidida

 

Hermissenda crassicornis  (Eschscholtz, 1831)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarchia, Infraorder Cladobranchia, Parvorder Aeolidida, Family Facelinidae

Elongate body 30-80 mm with dorsal clusters of fingerlike cerata; cerata with longitudinal white stripe but otherwise vary from pale orange to dark orange, often with dark brown core; body translucent blue with mid-dorsal orange streaks surrounded by blue stripes.

Infrequent on rocks & pilings; seasonal. Feeds on hydroids and other cnidarians.

Geogr. Range: Sitka Alaska to northern California
Synonyms: Phidiana crassicornis
Similar species:  Hermissenda opalescens lacks white lines on its cerata; Phidiana hiltoni lacks mid-dorsal orange patches with blue stripes.

 

 

 

Hermissenda opalescens  (Cooper, 1863)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarchia, Infraorder Cladobranchia, Parvorder Aeolidida, Family Facelinidae

Elongate body 30-80 mm with dorsal clusters of fingerlike cerata; cerata vary from pale orange to dark orange, often with white tips & dark brown core, but lack longitudinal white lines; dorsum of body translucent blue with mid-dorsal orange streaks surrounded by blue stripes.

Most common eolid in Monterey region on rocks & pilings, but seasonal. Feeds on hydroids and other cnidarians as well as compound tunicates.

Geogr. Range: northern California to Baja
Synonyms: Phidiana crassicornis
Similar species:  Hermissenda crassicornis has longitudinal white lines on its cerata; Phidiana hiltoni lacks mid-dorsal orange patches with blue stripes.

 

 

 

Phidiana hiltoni  (O'Donoghue, 1927)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarchia, Infraorder Cladobranchia, Parvorder Aeolidida, Family Facelinidae

Elongate body 40 mm, with dorsal clusters of fingerlike cerata; rhinophores pale yellow with red band at base; red line connects top of oral tentacles; cerata pink to red with white tips and dark gray-black core.

Moderately common, on rocks. Feeds on hydroids, other cnidarians.

Geogr. Range: Monterey Bay to Baja
Synonyms: Phidiana pugnax
Similar species: Hermissenda crassicornis and H. opalescens have mid-dorsal orange streaks bordered with blue stripes which are absent in Phidiana.

 

 

 

Aeolidia papillosa  (Linnaeus, 1761)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarchia, Infraorder Cladobranchia, Parvorder Aeolidida, Family Aeolidiidae

Broad body 25-50 mm covered with white flattened cerata which begin anterior to rhinophores. Distinctive triangular bright white patch between oral tentacles & rhinophores.

Infrequent, on pilings; feeds on tentacles of anemones & other cnidarians.

Geogr. Range: Cosmopolitan (world wide) in temperate seas
Synonyms:
Similar species:

 

 

 

Flabellina iodinea  (Cooper, 1862)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarchia, Infraorder Cladobranchia, Parvorder Aeolidida, Family Flabellinidae

Elongate body 40 mm; body bright purple with red rhinophores and orange cerata.

Infrequent on rocks, most often in deeper water in Monterey region.  Feeds on hydroids and other cnidarians. Can swim using lateral flexions of whole body.

Geogr. Range: British Columbia to Baja
Synonyms: Flabellinopsis iodinea
Similar species: no other eolids in Monterey region are purple.

 

 

  Infraorder Cladobranchia, Dendronotida

 

Dendronotus iris  Cooper, 1863
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarhcia, Infraorder Cladobranchia, Parvorder Dendronotida, Family Dendronotidae

Large dendronotid 60-300 mm with branched cerata; usually red but varies from white to gray or orange; thick branched rhinophores.

Sporadically common, on rocks or sand. Feeds on tentacles of the tube anemone Pachycerianthus & lays  egg masses on its tube.

Geogr. Range: Aleutian Islands to Baja
Synonyms:
Similar species:  Dendronotus albus is much smaller, white with orange-tipped cerata.

 

 

 

Dendronotus albus MacFarland, 1966
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarhcia, Infraorder Cladobranchia, Parvorder Dendronotida, Family Dendronotidae

Small dendronotid 15 mm with translucent white body, 5-7 pairs of branched cerata with orange tips.

Infrequent in Monterey kelp forests; somewhat seasonal. Feeds on hydroids and other cnidarians.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species:  Dendronotus diversicolor is also translucent white, but only 4 or fewer pr. cerata;  Dendronotus iris is much larger and red (not white).

Image: Parapholas siphon (upper rt.)

 

 

 

Melibe leonina  (Gould, 1852)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarhcia, Infraorder Cladobranchia, Parvorder Dendronotida, Family Tethyidae

Large dendronotid 35-300 mm with disk-shaped cerata; body translucent white to pale yellow. Large oral hood edged with fine tentacles surrounds mouth.

Large adults sporadically abundant on kelp fronds; small individuals common, but cryptic on kelp fronds in surface canopy. Lacks radula; captures larger zooplankton with oral hood.

Geogr. Range: Alaska to Gulf of California
Synonyms:
Similar species: no other nudibranch in Monterey has a large oral hood and disk-shaped cerata.

 

 

 

Dirona albolineata  MacFarland in Cockerell & Elliot 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Dexiarhcia, Infraorder Cladobranchia, Family Dironidae

Translucent white body 40-180 mm; cerata leaf-shaped with dense white margins & easily broken.

Infrequent & sporadic in Monterey kelp forests. Feed on small gastropods & a variety of sessile species such as hydroids, bryozoans & tunicates.

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

Image:  Phidolopora (upper rt.)

 

 

 Infraorder Doridacea

 

Peltodoris nobilis  (MacFarland, 1905)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Discodorididae

Large oval dorid 50-200 mm, yellow to orangish with black markings that do not extend onto dorsal tubercles; gill with 6 branchial plumes.

Common on rocks. Feeds on a variety of sponges.

Geogr. Range: British Columbia to Baja
Synonyms: Anisodoris nobilis
Similar species: Doris montereyensis is yellow with black markings that do extend up onto dorsal tubercles; Geitodoris (=Discodoris) heathi has black speckles on dorsum & tubercles, often with dark blotch just in front of gills; gills white w. minute black speckles.

 

 

 

Diaulula sandiegensis  (Cooper, 1863)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Discodorididae

Oval body 30-150 mm; white, cream, or pale yellow with paired irregular dark rings or irregular spots in 2 rows on dorsum.

Infrequent, on rocks. Feeds on sponges.

Geogr. Range: Alaska to Baja
Synonyms: Discodoris sandiegensis
Similar species: other white dorids in Monterey region lack distinctive dark rings on dorsum.

 

 

 

Rostanga pulchra MacFarland, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Discodorididae

Small dorid to 10 mm; usually bright red but varies from orange-yellow to scarlet; sometimes with minute brown spots on dorsum.

Common but inconspicuous, often on red encrusting sponges on which it feeds and lays its spiral egg ribbons. 

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species:

Image:

 

 

 

Cadlina luteomarginata  MacFarland, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Cadlinidae

White dorid, 35 mm, with yellow tubercles and yellow mantle margin.

Moderately common on rocks. Feeds on variety of sponges.

Geogr. Range: British Columbia to Baja
Synonyms:
Similar species: Doris odhneri is larger and lacks any yellow markings. Other species of Cadlina are white with yellow & dark markings or are yellow.

 

 

 

Cadlina flavomaculata  MacFarland, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Cadlinidae

Small white dorid, 15-20 mm, with two longitudinal rows of yellow spots on dorsum; rhinophores dark brown-black; gills yellow to white with 10-12 plumes (retracted in image).

Infrequent on rocks. Feeds on sponges.

Geogr. Range: Vancouver Island, BC to Punta Eugenia, Baja
Synonyms:
Similar species: Cadlina luteomarginata larger with yellow mantle margin and lacks black rhinophores; Doris odhneri larger and lacks any yellow markings. Other species of Cadlina are white with yellow & dark markings or are yellow.

 

 

 

Felimida macfarlandi  Cockerell, 1901
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Chromodorididae

Elongate dorid, 25-60 mm; bright purple with 3 dorsal longitudinal stripes and yellow edge to mantle.

Infrequent on rocks. Feeds on sponges.

Geogr. Range: Monterey Bay to Baja
Synonyms: Chromodoris macfarlandi
Similar species:

 

 

 

Doris montereyensis  Cooper, 1863
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Dorididae

Large yellow dorid, 50-150 mm; dark pigment mostly on tubercles but extending to dorsal surface itself; gill with 7 branchial plumes.

Moderately common on rocks. Feeds on encrusting sponges.  The individuals in image are mating.

Geogr. Range: Alaska to San Diego
Synonyms: Archidoris montereyensis
Similar species: Peltodoris nobilis is yellow with dark pigment that does not extend up onto dorsal tubercles; Geitodoris (=Discodoris) heathi has a prominent dark blotch just in front of branchial plume; white gills w. minute black speckles (requires a microscope)

Image: Dermasterias imbricata (top); Diplosoma listerianum(?) lower left.

 

 

 

Doris odhneri  (MacFarland, 1966)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Dorididae

Large pure white dorid, 60-200 mm; gill with 7 branchial plumes.

Infrequent in Monterey region, on rocks.  Feeds on a variety of encrusting sponges.

Geogr. Range: British Columbia to San Diego
Synonyms: Archidoris odhneri
Similar species: Cadlina luteomarginata is also white, but smaller & has yellow tubercles and a yellow mantle margin.

 

 

 

Doriopsilla albopunctata  (Cooper, 1863)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Dendrodorididae

Yellow dorid, 25 mm with white tips on dorsal tubercles; color varies from pale yellow to reddish-brown; gill white to pale yellow.

Abundant in Monterey, on rocks. Lacks radula; feeds on sponge prey by secreting digestive enzymes & ingesting liquefied tissue.

Geogr. Range: Northern California to Baja
Synonyms:
Similar species:  the other common yellow dorids (Peltodoris nobilis & Doris montereyensis) have dark pigment on dorsum & lack white-tipped tubercles. Cadlina modesta is yellow with midlateral brighter yellow spots & yellowish gills.

 

 

 

Triopha catalinae  (Cooper, 1863)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Polyceridae

Elongate dorid, 40 mm, with semi-circular oral veil bearing short branched tentacles; translucent white with orange-tipped tubercles and red-orange rhinophores.

Moderately common on rocks in kelp forests, also occurs in tidepools & on wharf pilings. Feeds on erect bryozoan colonies.

Geogr. Range: Aleutian Islands to Baja
Synonyms:
Similar species: Triopha maculata varies from yellow to orange, red, or dark brown (but not white) & has bluish white oval spots. Limacia cockerelli is also white with orange tubercles, but is much smaller and more oval.

 

 

 

Triopha maculata  MacFarland, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Polyceridae

Elongate dorid, 15-40 mm, with semi-circular oral veil bearing branched tentacles; body yellow to orange, red, or dark brown (but not white) with oval dorsal tubercles tipped with orange and small bluish-white spots on dorsum; also has a row of orange spots along dorsal mid-line between gill plume & rhinophores.

Infrequent on rocks and kelp fronds, where they often lay egg ribbons in summer.  Also occurs in Zostera beds on mudflats.  Feeds on erect & encrusting bryozoan colonies.

Geogr. Range: Oregon to Baja
Synonyms: larger individuals previously identified as Triopha grandis
Similar species: Triopha catalinae is white with orange-tipped tubercles & lacks blue spots.

 

 

 

Limacia cockerelli (MacFarland, 1905)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Polyceridae

Small dorid 15 mm with elongate orange-tipped club-shaped tubercles around margin of dorsum; rhinophores bright red-orange.

Moderately common, but inconspicuous on rocks.

Geogr. Range: British Columbia to Baja.
Synonyms: Laila cockerelli
Similar species: Triopha catalinae is much larger, more elongate with a distinct oral veil and has fewer orange tubercles on dorsum.

 

 

 

Okenia rosacea (MacFarland, 1905)
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Goniodorididae

Small pink hopkinsia dorid 20 mm; with very elongate dorsal tubercles which superficially resemble cerata but lack extensions of internal digestive gland.

Infrequent to common in Monterey region; on rocks. Feeds on rose-colored encrusting bryozoan Eurystomella bilabiata from which it obtains its pink pigment.

Geogr. Range: Oregon to Baja
Synonyms: Hopkinsia rosacea
Similar species: no other pink dorids occur in Monterey Bay

 

 

 

Acanthodoris brunnea  Cockerell & Eliot, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Onchidorididae

Small dark brown-black dorid 15-20 mm; dorsum covered with numerous blunt-tipped papillae; rhinophores elongate, tipped with yellow.

Infrequent in Monterey region; on rocks. Feeds on bryozoans.

Geogr. Range: Vancouver Island, British Columbia to Los Angeles
Synonyms:
Similar species:

 

 

 

Aegires albopunctatus  MacFarland, 1905
Phylum Mollusca, Class Gastropoda, Subcl. Heterobranchia, Infracl. Nudipleura, Order Nudibranchia, Suborder Eutenidiacea, Infraorder Doridacea, Family Aegiridae

Small white dorid to 20 mm; dorsum covered with cylindrical tubercles; body white with numerous dark brown or black spots; rhinophores white to yellow.

Infrequent in Monterey region; on rocks. Feeds on calcareous sponges.

Geogr. Range: Vancouver Island, British Columbia to Coronados Islands, Baja
Synonyms:
Similar species: