Marine Invert Practical Study Guide 2026

Acanthodoris nanaimoensis

Phylum: Mollusca 

Class: Gastropoda 

Tank(s) in lab: 1 

Habitat: Intertidal rocky areas with eelgrass. Found in the Northeast Pacific oceans from Alaska to California.

Acmaea mitra

Phylum: Mollusca

Class: Bivalvia

Tank(s) in lab: 7

Habitat: Lower intertidal to shallow subtidal, mainly found on rocks covered in algae.

Aeolidia papillosa 

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 1

Habitat: Found in cold intertidal waters on the North Pacific and North Atlantic coasts near communities of sea anemones.

Anthopleura artemisia

Phylum: Cnidaria

Class: Anthozoa

Tank(s) in lab: 6, 7

Habitat: Intertidal zones with rocky areas or sandy bottoms.

Anthopleura elegantissima 

Phylum: Cnidaria

Class: Anthozoa

Tank(s) in lab:6

Habitat: medium to high rocky intertidal

     Column is greenish to pale columns, pinkish to gray tentacle tips. Typically on the smaller side with a small column diamter

Anthopleura xanthogrammica 

Phylum: Cnidaria

Class: Hexacorallia

Tank(s) in lab: 1, 6

Habitat: Rocky intertidal

Arctonoe vittata

Phylum: Annelida

Class: Polychaeta

Tank(s) in lab: 24

Habitat: Commensal, live in oral surfaces of sea stars, gastropods and chtions (i.e., Dermasterias imbricata, Diodora aspera, and Cryptochiton stellari), and steal food particles from host

Balanus glandula

Phylum: Arthropoda

Class: Cirripedia or Maxillopoda

Tank(s) in lab: 6,7

Habitat: Found on rocks, piers, piliings, the shells of other organisms- Mytilus californianus. Usually found in the high intertidal zones.

Can be distinguished from other barnacles through the shape and division lines of operculum.

Balanus nubilus

Phylum: Arthropoda

Class: Cirripedia or Maxillopoda 

Tank(s) in lab: 6, 7, 8

Habitat: Found on hard substrates such as rocks and the carapaces of other invertebrates. Can also be commonly found on dock pilings.

Calliostoma ligatum

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 7

Habitat: Rocky Intertidal

Bilateral symmetry

Cancer antennarius

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 7, 11

Habitat: Rocky intertidal and subtidal zones, Can live in depth up to 100 m.

Cancer productus

Phylum: Arthropoda

Class: Malacostraca 

Tank(s) in lab: 7

Habitat: Rocky intertidal zones, bays, and estuaries in the Pacific ocean, found from Alaska to California 

Caprella alaskana

Phylum: Arthropoda

Class: Malacostroca 

Tank(s) in lab: 7

Habitat: Among algae in shallow intertidal to subtidal zones

They are very small and somewhat translucent. However if you focus on a still piece of Obelia dichotoma, you can see their movements to locate them. They will have visible appendages up by their head and the larger anterior portion will be clinging to the hydroid.

Carcinus maenas 

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 22

Habitat: Found primarily in estuaries and mudflats. 

Invasive along the Oregon coast. Five spines on outer edge of eyes.

Chthamalus dalli 

Phylum: Athropoda

Class: Cirripedia or Maxillopoda or Thecostraca

Tank(s) in lab: 7

Habitat: On rocky substrate in the high intertidal, distribution shaped by competition with Balanus glandula -> C. dalli restricted to high intertidal

Cryptochiton stelleri 

Phylum: Mollusca

Class: Polyplacophora

Tank(s) in lab: 24

Habitat: Intertidal to 20 meters. Japan, Alaska to California

Helpful information: The chitons 8 plates are completely covered by the girdle.

Epiactis prolifera 

Phylum: Cnidaria

Class: Anthozoa

Tank(s) in lab: 6

Habitat: In the range of Southern Alaska to southern California, they are found on and under rocks, on algae and eelgrass, and in outer rocky coasts as well as bays.

Distinguishing factors: It has no acontia, column no tubercles and no adherent material. Its oral disk typically has narrow radiating white lines which originate near the mouth and has externally brooding young of various sizes and year-round.

Evasterias troschelii

Phylum: Echinodermata 

Class: Asteroidea

Tank(s) in lab: 14

Habitat: Rocky intertidal and subtidal zones down to 75 meters on the Pacific coast from Alaska to California.

Halichondria panicea 

Phylum: Porifera 

Class: Demospongiae

Tank(s) in lab: 8, 6

Habitat: Intertidal, rocky shores

Haliclona spp.

Phylum: Porifera

Class: Demospongiae

Tank(s) in lab: 8

Habitat: intertidal and rocky shores

*do not need to know species - just phylum, class, genus

Hemigrapsus nudus 

Phylum: Arthropoda

Class: Malacostraca 

Tank(s) in lab: 3,7

Habitat: Rocky intertidal, prefers less muddy environments

Distinguishable by lack of hair on their legs, most have purple spots on pincers, however there is a green variant.

Hemigrapsus oregonensis

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 3

Habitat: Rocky intertidal beneath rocks

Has hair on legs, one spine next to each eye

Henricia leviuscula 

Phylum: Echinodermata

Class: Asteroidea

Tank(s) in lab: 6

Habitat: Intertidal zone up to 400m deep. From Alaska to Mexico and Japan.

Characteristics: Commensalist relationship with Arctonoe vittata, a polychaete worm. No pedicellaria or spines

Hermissenda crassicornis 

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 1 and 5

Habitat: Predominantly found in the rocky intertidal but also in bays and estuaries

Idotea montereyensis

Phylum:  Arthropoda

Class: Malacostraca

Tank(s) in lab: 6, 5

Habitat: Found in the intertidal, strictly a marine species

Tips for Identification: Idotea montereyensis may be confused with Idotea wosnesenskii but can be distinguished by its longer, more slender body compared to Idotea wosnesenskii which is more rounded and wider.

Idotea wosnesenskii 

Phylum:  Arthropoda

Class: Malacostraca

Tank(s) in lab: 8

Habitat: Intertidal, under rocks. Clinging to stalks of seaweed

Katharina tunicata 

Phylum: Mollusca

Class: Polyplaccophora

Tank(s) in lab: 8

Habitat: Rocky intertidal ares

Littorina spp. 

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 3,6,7,8

Habitat: intertidal rock shores, but can also be found in mudflats or marsh habitats

*do not need to know species - just phylum, class, and genus

photo not correctly added to slide deck yet

Lottia asmi

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 1, 3, 2, 7, 8, 10, 11, 13 

Habitat: Rocky Intertidal

Bilateral symmetry

Commonly known as the black limpet, ranging 5-10mm in size, found commonly on snails, mussels, or rocks. (very tiny!)

Lottia digitalis

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 6, 7, 8

Habitat: Rocky intertidal areas higher than most other species of limpets

Tips for Identifcation: Lottia digitalis can be distinguished from other limpets by its ribbed shell. If one runs their fingers along this species, noticeable bumps or “ribs” can be felt compared to other limpets which possess a smoother shell.

Macoma nasuta

Phylum: Mollusca

Class: Bivalvia

Tank(s) in lab: 4

Habitat: Burrows in mudflats and other soft substrates

Species Interactions: Pea Crabs, Pinnixa littoralis or Nemertean worms, Malacobdella grossa, may live in it’s mantle cavity 

Distinguishing features: posterior ends are bent to the right

Membranipora serrilamella

Phylum: Bryozoan

Class: Gymnolaemata

Tank(s) in lab: 6

Habitat: Forms calcified colonies on kelp, rocks, shells or human made structures such as boats and docks.

Mesocentrotus (or Strongylocentrotus) franciscanus 

Phylum: Echinodermata

Class: Echinoidea

Tank(s) in lab: 10

Habitat: rocky intertidal zones from Alaska to Mexico up to 160m. Ecological engineers by controlling kelp forest growth.

Mopalia muscosa 

Phylum: Mollusca

Class: Polyplacophora

Tank(s) in lab: 1, 3, 6, 7, 8

Habitat: Rocky low to mid intertidal zones, found typically clinging to rocks

Mytilus californianus 

Phylum: Mollusca

Class: Bivalvia

Tank(s) in lab: 2, 3, 6, 7, 8, 10, 11, 14, 23,24

Habitat: Intertidal zones, preferring rocky areas

Mytilus trossulus

Phylum: Mollusca

Class: Bivalva

Tank(s) in lab: 2,3,6,7,8,10,11,14,22

Habitat: Rocky intertidal, dock fouling communities

Tips for Indentifcation: Mytilus trossulus can be distinguished from Mytilus californianus by the former’s smaller size and being more brown in color.

Neotrypaea californiensis 

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 17 and 9

Habitat: intertidal mudflats and beaches in burrow systems

Nereis vexillosa 

Phylum: Annelida

Class: Polychaeta

Tank(s) in lab:5 

Habitat: sand, muddy sand or rocks in the intertidal to subtital

The posterior noropodila lobes are elongated and strap like, generally on the large side for polychaeta, about 1.2cm wide

Nucella ostrina

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 3, 6, 7, 8

Habitat: high-mid rocky intertidal, found amongst barnacle prey and on mussels

N. ostrina has so much natural variation that it can be hard to think of as one species.

Images not added by classmates

Nucella canaliculata

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 7

Habitat:

Images not added by classmates

Obelia dichotoma

Phylum: Cnidaria

Class: Hydrozoa

Tank(s) in lab: 8

Habitat: Rocky intertidal from Alaska to South America. Colonies often found hanging from algae, of other inverts. 

Distinguishable by zig-zag center branching pattern

Ophlitaspongia pennata

Phylum: Porifera

Class: Demospongiae

Tank(s) in lab: 6, 8

Habitat: Rocky intertidal

Orthione griffensis

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 18, 21

Habitat: On or under the gill flap of Upogebia pugettensis, with which they have a parasitic relationship

Smaller = male

Larger = female

Pachygrapsus crassipes

Phylum: Anthropoda

Class: Malacostraca

Tank(s) in lab: 21 and 5

Habitat: Found in crevices, under rocks, in tidepools and mussel beds. They can also sometimes be found in clay burrows. 

Pagurus spp.

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 3,6,7,8

Habitat: Rocky intertidal areas through the upper and lower zones. They can be found in areas with rocky, sandy, muddy, and grassy bottoms.

*do not need to know species - just phylum, class, and genus

Peltodoris nobilis

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 8

Habitat: Rocky intertidal

White tipped gills and spots between tubercles. Whereas Doris montereyensis has spots on top of tubercles

Petrolisthes spp.

Phylum: Anthropoda

Class: Malacostraca

Tank(s) in lab: 3, 6, 7

Habitat: Found in the rocky intertidal. Commonly found under rocks or in bunches of mussels.

Differentiate from Hemigrapsus by flattened carapace shape and only three pairs of walking legs.

*do not need to know species - just phylum, class, and genus

Phascolosoma agassizii

Phylum: Sipuncula

Class: Sipunculidea

Tank(s) in lab: 2,6

Habitat: Found buried in the mud near surfgrass roots or hiding in the cracks of rocks

Pisaster ochraceus

Phylum: Echinodermata 

Class: Asteroidea

Tank(s) in lab: 14

Habitat: Tidepools, rocky intertidal, and kelp forests to 97m

Pollicipes polymerus

Phylum: Arthropoda

Class: Maxillopoda

Tank(s) in lab: 1, 3, and 8 

Habitat: Lives in intertidal zone on rocks and wave swept boulders; exposed

Protothaca staminea

Phylum: Mollusca

Class: Bivalvia

Tank(s) in lab: 1, 4

Habitat: middle-to-low intertidal zones, sandy muds

Pugettia producta

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 2

Habitat: Kelpbeds, pilings, juveniles in tidepools

Distinguishable by extended, two-pointed carapace between eyes and shield-shaped carapace

Rostanga pulchra

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 1 and 8

Habitat: rocky intertidal often on top of red sponges like Ophiliaspongia pennata 

Semibalanus cariosus 

Phylum: Arthropoda

Class: Cirripedia or Maxillopoda or Thecostraca

Tank(s) in lab: 7

Habitat: Lives in mid intertidal low intertidal on rocks; exposed

Strongylocentrotus purpuratus 

Phylum: Echinodermata

Class: Echinoidea

Tank(s) in lab: 10

Habitat: Rocky intertidal, tidepools, kelp beds

Tegula funebralis 

Phylum: Mollusca

Class: Gastropoda

Tank(s) in lab: 8, 7, 6, and 3

Habitat: rocky intertidal of the PNW and california

Upogebia pugettensis 

Phylum: Arthropoda

Class: Malacostraca

Tank(s) in lab: 17, 18, 20, 21

Habitat: Found along the intertidal burrowing in estuarine mudflats from Alaska to California.

Urticina crassicornis

Phylum:Cnidaria

Class: Hexacorallia

Tank(s) in lab: 1,6

Habitat: Intertidal to at least 30 m. Range from Alaska to California

Helpful information: Look very similar to Anthopleura elegantissima. Distinguishable by bands of color instead of the color at the tentacle tips in elegantissima.

Velella velella

Phylum: Cnidaria 

Class: Hydrozoan

Tank(s) in lab: 4

Habitat: Open ocean (pelagic), temperate to tropical oceans of the Pacific and Atlantic.