Phylum Arthropoda, Subph. Crustacea: Subtidal Barnacles, Crabs, Shrimp, & Kin

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Arthropods comprise the largest animal phylum: there are more arthropod species than all other animal phyla combined. Crustaceans dominate the seas while insects and chelicerates dominate the land. Characterized by a segmented body covered with a rigid exoskeleton made of chitin and paired jointed appendages. Animals must shed their exoskeleton periodically in order to grow. >1 million living species; 40-50,000 living species of crustaceans alone.

Class Thecostraca, Subclass Cirripedia
  Order Thoracica
Balanus nubilus
Balanus crenatus
Megabalanus californicus
Menesiniella aqulia
Balanus
nubilus
Balanus
crenatus
Megabalanus californicus
Menesiniella aquila
Class Malacostraca, Subclass Eumalacostraca
  Superorder Eucarida, Order Decapoda
  Infraorder Brachyura
Cancer antennarius
Cancer gracilis Cancer jordani

Heterocrypta occidentalis



Cancer antennarius Cancer gracilis
Cancer jordani

Heterocrypta occidentalis



Loxorhynchus crispatus Loxorhynchus grandis Mimulus foliatus Pugettia richii Pugettia producta Scyra acutifrons
Loxorhynchus crispatus Loxorhynchus grandis Mimulus
foliatus
Pugettia
richii
Pugettia
producta
Scyra
acutifrons




  Infraorder Caridea Infraorder Anomura
Pandalus danae

Cryptolithodes sitchensis Paguristes ulreyi Pagurus armatus Pagurus hemphilli Phyllolithodes papillosus
Pandalus
danae
Cryptolithodes sitchensis Paguristes
ulreyi
Pagurus
armatus
Pagurus hemphilli Phyllolithodes papillosus
 Superorder Peracarida 
   Order Isopoda Order Amphipoda
Idotea resecata
caprellid amphipod gammarid amphipod tubes
Idotea
resecata
caprellids gammarids

 












Balanus nubilus
Balanus nubilus  Darwin, 1854
Phylum Arthropoda, Subph. Crustacea, Class Thecostraca, Subcl. Cirripedia, Order Thoracica, Family Balanidae

One of the largest local barnacles; to 11 cm diameter with a broad aperture relative to its base; opercular plates with distinct beaks. 

Common but patchy, usually occurring in clusters; on rocks especially in deeper water & on isolated rocky pinnacles; also on wharf pilings where they haven't been eaten by sea otters.

Geogr. Range: Alaska to San Diego
Synonyms:
Similar species: Menesiniella aquila is as large but has a much smaller aperture relative to its basal diameter.

Image: Halocynthia igaboja (lower left next to tan sponge)

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Menesiniella aquila
Menesiniella aquila  (Pilsbry, 1907)
Phylum Arthropoda, Subph. Crustacea, Class Thecostraca, Subcl. Cirripedia, Order Thoracica, Family Balanidae

Large barnacle to 13 cm diameter; aperture small relative to basal diameter; opercular plates with distinct beaks. 

Infrequent and patchy, sometimes occurring in clusters; on rocks at all depths; also on wharf pilings.

Geogr. Range: San Francisco to San Diego
Synonyms: Balanus aquila
Similar species: Balanus nubilus is also large but has a much broader aperture relative to its base.

Image: Acanthancora (rt side); sponge on barnacle probably Clathria pseudonapya.

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Balanus crenatus Balanus crenatus  Bruguière, 1789
Phylum Arthropoda, Subph. Crustacea, Class 
Thecostraca, Subcl. Cirripedia, Order Thoracica, Family Balanidae

Acorn barnacle to 10 mm, white with smooth shell plates. 

Abundant but inconspicuous, especially on vertical rock faces in kelp forests.

Geogr. Range: Alaska to Santa Barbara, Japan
Synonyms:
Similar species: Balanus glandula is similar in size but occurs in intertidal rather than subtidal habitats.


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Megabalanus californicus
Megabalanus californicus  (Pilsbry, 1916)
Phylum Arthropoda, Subph. Crustacea, Class Thecostraca, Subcl. Cirripedia, Order Thoracica, Family Balanidae

Acorn barnacle to 30 mm diameter, shell plates with longitudinal red and white stripes; mantle margin with orange, blue, yellow, & red - most colorful local barnacle.

Common but patchy; low intertidal zone and subtidal on rocky substrate; most frequently seen in clusters on buoys & pilings.

Geogr. Range: northern California to Gulf of California
Synonyms: Balanus tintinnabulum californicus
Similar species:  

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Cancer antennarius Cancer antennarius  Stimpson, 1856
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Family Cancridae

Large crab 15-18 cm across; reddish-brown; large claws tipped with black; teeth on anterior edge of carapace taper to a sharp point; underside of body with conspicuous red spots; juveniles' carapace usually covered with hair-like setae.

Common, but cryptic; under rocks and in crevices on rocky substrate in kelp forests.  Predator on hard-shelled prey (snails, clams, etc).

Geogr. Range: British Columbia to Cabo San Lucas, Baja
Synonyms:
Similar species: Cancer productus is also reddish with black-tipped claws, but lacks red spots on underside and carapace teeth are broader & rounder.

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Cancer gracilis Cancer gracilis  Dana, 1852
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Family Cancridae

Medium-size crab 6-9 cm across; carapace more oval than other Cancer & widest at 9th tooth; legs slender & graceful; teeth of carapace edged with white; tips of claws white, legs purple.

Can be common on sand & mudflats; feeds on barnacles & small bivalves.  Late stage larvae & young juveniles commonly found living on large jellyfish (Chrysaora spp.)

Geogr. Range: Prince William Sound Alaska to Baja
Synonyms:
Similar species: Cancer productus is larger,  reddish with black-tipped claws;C. antennarius is larger, has black-tipped claws but also red spots on underside..

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Cancer jordani Cancer jordani  Rathbun, 1900
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Family Cancridae

Small, hairy Cancer crab to 3.9 cm across; mottled brown or red with black tips on claws; teeth on carapace strongly curved; legs & carapace with many fine hair-like setae.

Uncommon & cryptic; under rocks and nestled in kelp holdfasts.

Geogr. Range:  Washington to Baja
Synonyms:
Similar species: Cancer productus is larger,  reddish with black-tipped claws;C. antennarius is larger, has black-tipped claws but also red spots on underside.

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Loxorhynchus crispatus Loxorhynchus crispatus  Stimpson, 18578
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura,  Superfamily Majoidea, Family Pisidae

Decorator crab; large triangular carapace 8-12 cm across; decorates heavily when young, but less so with increased size (inset); rostrum a pair of short, flattened, straight- sided horns; males with larger claws than females.

Common, in rocky habitat with good algal & invertebrate cover.

Geogr. Range: northern California to Baja
Synonyms:
Similar species: Scyra acutifrons is much smaller and differs from juvenile L. crispatus and L. grandis by leaf-shaped horns of rostrum with rounded outer edges.

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Loxorhynchus grandis Loxorhynchus grandis  Stimpson, 1857
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Superfamily Majoidea, Family Pisidae

Sheep crab; large, rounded carapace 11-16 cm across with wart-like tubercles; rostrum angles sharply downward; grayish- brown with blue on tips of tubercles; young crabs usually decorate carapace, but decreases with age/size.

Uncommon in Monterey, in rocky areas with kelp or on adjacent nearby sandy areas.

Geogr. Range: northern California to Baja
Synonyms:
Similar species: Carapace of Loxorhynchus crispatus  more triangular & not so rounded & inflated. Rostrum of Scyra acutifrons flattened leaf-shaped horns with distinctly rounded outer margins while that of L.grandis is straight-sided and angled downward.

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Scyra acutifrons Scyra acutifrons  Dana, 1851
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Superfamily Majoidea, Family Pisidae

Triangular carapace 4-5 cm across; rostrum a pair of flat, leaf-shaped horns; carapace brown or tan, but usually overgrown with encrusting invertebrates. Males with larger claws than females.

Abundant, among algae & sessile invertebrates on rocky substrate. 

Geogr. Range: Alaska to Baja, uncommon south of central California
Synonyms:
Similar species: young Loxorhynchus crispatus  decorate more heavily; rostrum is shorter with straight horns lacking rounded outside edges. Loxorhynchus grandis has a rounder, inflated carapace with wart-like spines and its rostrum is angled downward rather than flat.

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Mimulus foliatus Mimulus foliatus  Stimpson, 1860
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Superfamily Majoidea, Family Epialtidae

Carapace wider than long, 3-4 cm across; 2 flattened carapace teeth form pointed flanges on either side of rostrum; lateral margins of carapace with pair of wide triangular flanges; color pattern variable, often forming disruptive patterns between carapace, legs, and claws.

Abundant, but cryptic; on rocky substrate nestled among algae & sessile invertebrate cover. Decorates relatively little compared to other spider crabs.

Geogr. Range: Alaska to San Diego
Synonyms:
Similar species: this is the only local spider crab whose carapace is broader than long.

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Pugettia richii Pugettia richii  Dana, 1851
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Superfamily Majoidea, Family Epialtidae

Carapace 3-4 cm across, somewhat diamond-shaped with several prominent lateral spines; brownish to scarlet; lateral carapace with curved horn-like teeth; tips of claws white. Decorates rostrum (but not rest of carapace) with red algae.

Abundant, but well camouflaged among red algae & sessile invertebrates; at night, climbs kelp fronds and reproductive fronds of Cystoseira.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species: Pugettia gracilis has shorter legs, tips of claws bluish with orange tips.

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Pugettia producta Pugettia producta  (Randall, 1840)
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Superfamily Majoidea, Family Epialtidae

Kelp crab; carapace smooth & broad 8-9 cm across; pointed lateral teeth curve forward; edge of carapace between teeth straight; kelp brown to dark maroon. Juveniles may occasionally decorate rostrum, but adults devoid of decoration.

Common, in canopy of giant kelp, also wharf pilings. Juveniles in low intertidal on rocky shores.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species: other Pugettia lack such a smooth, kelp-colored carapace.

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Heterocrypta occidentalis
Heterocrypta occidentalis  (Dana, 1854)
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Brachyura, Family Parthenopidae

Elbow crab; wing-shaped carapace with straight posterior edge, much broader than long, 2 cm across; rostrum shaped like an arrowhead; propodus & carpus of claws very elongate, tipped with small, angled pincers. 

Moderately common, but very cryptic, remaining buried in sand or shell rubble during daylight hours. Captures small prey in the elbow of claw between propodus & carpus, not with pinchers.

Geogr. Range: central California to Baja
Synonyms:
Similar species: no other local crab looks like Heterocrypta

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Pandalus danae Pandalus danae  Stimpson, 1857
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Caridea, Family Pandalidae

Coonstripe shrimp; brown to red irregular stripes with blue spots and white & yellow markings; antennae and legs banded. To 14 cm but usually much smaller in kelp forest habitats.

Common, in crevices on rock outcrops; maybe be a facultative fish cleaner.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species: numerous small shrimp occur in Monterey, but Pandalus is probably the most commonly encountered by divers.

Image: Cryptochiton (rt. side), Astrangia (upper left)


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Pagurus hemphilli Pagurus hemphilli  (Benedict, 1892)
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Anomura, Family Paguridae

Hermit crab; red with small white or blue markings; distinctive yellow rings on compound eyes. 

Very abundant, throughout kelp forest habitats on and around rocky substrate. Usually in Chlorostoma shells. Scavengers & micro-predators.

Geogr. Range: Alaska to central California, San Miguel Island
Synonyms:
Similar species: yellow rings on eyes are distinctive for P. hemphilli.

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Pagurus armatus Pagurus armatus  (Dana, 1851)
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Anomura, Family Paguridae

Large hermit crab with distinctive black oblong compound eyes; claws with numerous spines; legs and claws with orange-red & white bands.

Common, in sandy areas adjacent to rocky kelp forest habitats. Often in shell of the moon snail Euspira.

Geogr. Range: Alaska to San Diego
Synonyms:
Similar species: this is one of the larger hermit crabs in Monterey region.

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Paguristes ulreyi Paguristes ulreyi  Schmitt, 1921
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Anomura, Family Diogenidae

Medium large hermit crab; with orange to brown legs & claws covered with golden hairs; eye stalks long and slender; short stout antennae with obvious fringe of long hairs used for suspension feeding. 

Moderately common in Monterey kelp forests, on rocks, sandy areas near bases of rocky outcrops.

Geogr. Range: British Columbia to Gulf of California
Synonyms:
Similar species: several other hairy hermit crabs occur in Monterey but are less abundant than P. ulreyi.

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Cryptolithodes sitchensis Cryptolithodes sitchensis  Brandt, 1853
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Anomura, Family Lithodidae

Helmet crab; carapace to 8 cm across, expanded to cover legs & claws; width of rostrum expands from base to tip; bright red, orange to white with spots of various colors. 

Common, on rocky substrate or sand near rocks.

Geogr. Range: Alaska to San Diego
Synonyms:
Similar species:

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Phyllolithodes papillosus Phyllolithodes papillosus  Brandt, 1849
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Eucarida, Order Decapoda, Suborder Pleocyemata, Infraorder Anomura, Family Lithodidae

Triangular carapace to 9 cm across (usually less) with obvious heart-shaped raised ridge; legs and claws with thick spine-like projections.

Uncommon, in rocky areas.

Geogr. Range: Alaska to San Miguel Island
Synonyms:
Similar species:

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Idotea resecata
Idotea resecata  Stimpson, 1857
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Peracarida, Order Isopoda, Suborder Valvifera

Elongate body, dorso-ventrally flattened; posterior edge of telson distinctly concave. Kelp colored. 

Abundant on fronds of giant kelp; also occurs on sea grasses and smaller red algae.  Major prey of many fishes.

Geogr. Range: Alaska to Mazatlan, Mexico
Synonyms:
Similar species: numerous other species of Idotea occur in central California & can be distinguished by shape of telson.

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gammarid tubes Gammarid amphipods
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Peracarida, Order Amphipoda

Beach hoppers; bodies laterally compressed. Most amphipods in kelp forests are tiny; some species build spongy proteinaceous tube masses (photo) in which many individuals live.

Very abundant; ubiquitous. Important prey for a variety of fishes.

Geogr. Range:
Synonyms:
Similar species:

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caprellid amphipod Caprellid amphipods
Phylum Arthropoda, Subph. Crustacea, Class Malacostraca, Subcl. Eumalacostraca, Superorder Peracarida, Order Amphipoda

Skeleton shrimp.  Tiny elongate amphipods; grasp substrate with posterior legs and wave upper body in the water to capture food particles drifting by.

Very abundant, on algae, hydroids, and other bushy invertebrate colonies.  

Geogr. Range:
Synonyms:
Similar species:

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Page created by J.M. Watanabe
All images copyright James Watanabe unless otherwise indicated
Contact:  watanabe_at_stanford_dot_edu                                                                                                                                   Last  update: 24 August 2011