Hydrozoa & Scyphozoa

Phylum Cnidaria: Subtidal Hydroids & Medusae

Radially symmetrical predators with relatively simple body structure. Most are sessile or move only slowly. Presence of microscopic stinging cells (nematocysts) aids in their effective capture of prey. 10,000 living species.

Class Hydrozoa
Subclass Anthoathecata (=Anthomedusae, Athecata)


Garveia annulata	Hydractinia milleri	Pinauay marina	Stylaster californicus	Stylantheca porphyra

Subclass Leptothecata (=Leptomedusae, Thecata)


Abietinaria	Aglaophenia	Obelia	Orthopyxis	Plumularia

Class Scyphozoa
Order Semaeostomeae


Aurelia labiata	Chrysaora colorata	Chrysaora fuscescens	Phacellophora camtschatica

	Hydractinia milleri Torrey, 1902 Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Hydractiniidae Inconspicuous colonies resembling whitish fuzz of naked hyrdanths 5 mm tall arising from basal mat of stolons; white to pinkish; colonies polymorphic; no free-swimming medusa stage. Moderately common, but inconspicuous due to small size; on sides of rocks and in crevices, Geogr. Range: British Columbia to Monterey Synonyms: Similar species: several species of Hydractinia occur in Monterey, distinguished by size of gastrozooids, number of tentacles and number & location of gonophores. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Garveia annulata (Nutting, 1901) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Bougainvilliidae Conspicuous erect branched colonies to 15 cm tall, bright orange to yellow; main branches composed of several parallel tubes (polysiphonous). Gonophores attached to main axes; no free-swimming medusae. Moderately common in wave-exposed sites (Carmel Bay) on sponges, red algae, and corallines. Also in rocky intertidal. Geogr. Range: Alaska to Channel Islands Synonyms: Similar species: bright orange color is distinctive for this species. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Stylaster californicus (Verrill, 1866) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Stylasteridae Hydrocoral with massive CaCO₃ skeleton; bright purple to pinkish-red. Gastrozooids surrounded by ring of defensive stinging dactylozooids. Abundant, typically in deeper water at wave-exposed sites (e.g. Carmel Bay). Geogr. Range: northern California to Baja Synonyms: Allopora californica Similar species: Stylantheca porphyra grows in encrusting sheets rather than branched erect colonies; molecular data suggests these two species may be morphs of the same species. Several other similar species occur farther north to British Columbia. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Stylantheca porphyra Fisher, 1931 Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Stylasteridae Encrusting hydrocoral with CaCO₃ skeleton; purple. Gastrozooids surrounded by ring of stinging defensive dactylozooids. Infrequent, in wave-exposed sites, low intertidal to subtidal; on rocky substrate. Geogr. Range: British Columbia to southern California Synonyms: Allopora porphyra Similar species: Stylaster californicus grows in erect colonies and is somewhat more variable in color; molecular data suggests these two species may be morphs of the same species. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Pinauay marina (Torrey, 1902) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Capitata, Family Tubulariidae Polyps 5 cm tall, solitary or in well-spaced groups; hydranth pink with 2 concentric rings of tentacles; perisarc of stalk dark. Gonophores located between whorls of tentacles; no free medusae. Moderately common but inconspicuous, on rocks nestled among colonial invertebrates in exposed and semi-exposed sites. Geogr. Range: British Columbia to California Synonyms: Tubularia marina, Ectopleura marina Similar species: Pinauay crocea grows in colonies of tangled mats to 15 cm tall, typically in harbors and protected sites. Image: Crisia (cntr. bottom), Corynactis (lower left & rt.) \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Aglaophenia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Aglaopheniidae Robust feather-like colony to 10 cm tall; brown, orange or tan. Rice grain-like structures (corbulae) on side branches house reproductive individuals (no free-swimming medusae). Abundant, especially in shallow surgy areas where geniculate coralline algae are common; colonies in low intertidal zone often epiphytic on red algae. Geogr. Range: Alaska to southern California Synonyms: Similar species: other feathery hydroid species such as Plumularia are much more delicate that Aglaophenia. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Abietinaria spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Sertulariidae Planar colony to 8 cm tall, with side branches alternating from central axis (pinnate); drab tan. Hydranths (not visible to naked eye) in flask-shaped cups (thecae) that alternate along opposite sides of branches. Abundant, colonies often in clusters with plane of colony oriented perpendicular to direction of wave surge. Geogr. Range: Alaska to southern California Synonyms: Similar species: several species of Abietinaria occur in Monterey Bay and are difficult to identify in the field without high magnification. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Plumularia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Plumulariidae Delicate colonies resembling sparsely branched feathers ~2 cm tall; usually growing in clusters, pale tan. Gastrozooids widely spaced on side one side of each side branch. Abundant but inconspicuous, on rocks among other sessile invertebrates and algae. Geogr. Range: Alaska to Baja Synonyms: Similar species: Aglaophenia is much more robust & larger than Plumularia. Several species of Plumularia occur in Monterey but require a microscope to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Obelia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Proboscoida, Family Campanulariidae Bushy delicate colony up to 15 cm tall with side branches arising in all planes; pale tan. Gastrozooids tiny; free-swimming medusae released from reproductive gonozooids. Abundant on any hard surface; good colonizer of newly open substrate. Geogr. Range: genus occurs world-wide Synonyms: Similar species: several species of Obelia occur in Monterey but require microscopic examination to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Orthopyxis spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Proboscoida, Family Campanulariidae Unbranched polyps arise from basal stolon overgrowing red algae and other ephemeral substrata, pale tan. Can be very abundant; most conspicuous on low-lying red algae such as Rhodymenia pacifica, several species. Geogr. Range: Alaska to southern California Synonyms: Similar species: several species of Orthopyxis occur in Monterey, but require microscopic examination to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Chrysaora colorata (Russell, 1964) Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Pelagiidae Large medusa 70 cm diameter, pale with distinctive dark markings on bell and margin. Unpleasant sting. Can be common but does not form large surface aggregations; pelagic; specimens encountered offshore of kelp forests often damaged. Geogr. Range: central California to southern California Synonyms: Pelagia colorata Similar species: C. colorata often misidentified as Chrysaora noctiluca which is a southern, warm water spp. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Chrysaora fuscescens Brandt, 1835 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Pelagiidae Large medusa 30 cm diameter; bell yellow-brown to reddish brown with 24 dark tentacles around margin. Oral arms long & folded, dark with white/clear frills. Unpleasant sting. Can form large aggregations, especially late summer through winter; pelagic offshore from kelp forests. Geogr. Range: Alaska to Baja. Synonyms: Chrysaora helvola, C. gilberti Similar species: often misidentified as Chrysaora melanaster. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Phacellophora camtschatica Brandt, 1835 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Ulmaridae Large medusa 60 cm diameter; clear to yellowish bell with central yellow gonads; 16 clusters of tentacles, 16 sensory rhopalia around margin of bell; small individuals often with milky white bell. Oral arms short & highly folded, said to resemble a fried egg. Mild sting. Does not usually form large aggregation; pelagic offshore from kelp forests. Geogr. Range: Kamchatka to Alaska & south to Chile. Synonyms: Similar species: \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Aurelia labiata Chamisso & Eysenhardt, 1821 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Ulmaridae Shallow bell to 40 cm fringed with many fine tentacles; 4 short oral arms; opaque white, usually with 4 horseshoe-shaped gonads visible. Very mild sting. May form dense aggregations (late summer / autumn), pelagic offshore from kelp forests. Geogr. Range: Oregon to central California Synonyms: Similar species: often misidentified as the non-native Aurelia aurita. \| back to spp. list \| more info \| refs. \| kelp forest index \|

Page created by J.M. Watanabe
All images copyright James Watanabe unless otherwise indicated

Contact: watanabe_at_stanford_dot_edu Last update: 10 October 2009

	Hydractinia milleri Torrey, 1902 Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Hydractiniidae Inconspicuous colonies resembling whitish fuzz of naked hyrdanths 5 mm tall arising from basal mat of stolons; white to pinkish; colonies polymorphic; no free-swimming medusa stage. Moderately common, but inconspicuous due to small size; on sides of rocks and in crevices, Geogr. Range: British Columbia to Monterey Synonyms: Similar species: several species of Hydractinia occur in Monterey, distinguished by size of gastrozooids, number of tentacles and number & location of gonophores. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Garveia annulata (Nutting, 1901) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Bougainvilliidae Conspicuous erect branched colonies to 15 cm tall, bright orange to yellow; main branches composed of several parallel tubes (polysiphonous). Gonophores attached to main axes; no free-swimming medusae. Moderately common in wave-exposed sites (Carmel Bay) on sponges, red algae, and corallines. Also in rocky intertidal. Geogr. Range: Alaska to Channel Islands Synonyms: Similar species: bright orange color is distinctive for this species. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Stylaster californicus (Verrill, 1866) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Stylasteridae Hydrocoral with massive CaCO₃ skeleton; bright purple to pinkish-red. Gastrozooids surrounded by ring of defensive stinging dactylozooids. Abundant, typically in deeper water at wave-exposed sites (e.g. Carmel Bay). Geogr. Range: northern California to Baja Synonyms: Allopora californica Similar species: Stylantheca porphyra grows in encrusting sheets rather than branched erect colonies; molecular data suggests these two species may be morphs of the same species. Several other similar species occur farther north to British Columbia. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Stylantheca porphyra Fisher, 1931 Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Filifera, Family Stylasteridae Encrusting hydrocoral with CaCO₃ skeleton; purple. Gastrozooids surrounded by ring of stinging defensive dactylozooids. Infrequent, in wave-exposed sites, low intertidal to subtidal; on rocky substrate. Geogr. Range: British Columbia to southern California Synonyms: Allopora porphyra Similar species: Stylaster californicus grows in erect colonies and is somewhat more variable in color; molecular data suggests these two species may be morphs of the same species. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Pinauay marina (Torrey, 1902) Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Capitata, Family Tubulariidae Polyps 5 cm tall, solitary or in well-spaced groups; hydranth pink with 2 concentric rings of tentacles; perisarc of stalk dark. Gonophores located between whorls of tentacles; no free medusae. Moderately common but inconspicuous, on rocks nestled among colonial invertebrates in exposed and semi-exposed sites. Geogr. Range: British Columbia to California Synonyms: Tubularia marina, Ectopleura marina Similar species: Pinauay crocea grows in colonies of tangled mats to 15 cm tall, typically in harbors and protected sites. Image: Crisia (cntr. bottom), Corynactis (lower left & rt.) \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Aglaophenia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Aglaopheniidae Robust feather-like colony to 10 cm tall; brown, orange or tan. Rice grain-like structures (corbulae) on side branches house reproductive individuals (no free-swimming medusae). Abundant, especially in shallow surgy areas where geniculate coralline algae are common; colonies in low intertidal zone often epiphytic on red algae. Geogr. Range: Alaska to southern California Synonyms: Similar species: other feathery hydroid species such as Plumularia are much more delicate that Aglaophenia. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Abietinaria spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Sertulariidae Planar colony to 8 cm tall, with side branches alternating from central axis (pinnate); drab tan. Hydranths (not visible to naked eye) in flask-shaped cups (thecae) that alternate along opposite sides of branches. Abundant, colonies often in clusters with plane of colony oriented perpendicular to direction of wave surge. Geogr. Range: Alaska to southern California Synonyms: Similar species: several species of Abietinaria occur in Monterey Bay and are difficult to identify in the field without high magnification. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Plumularia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Plumulariidae Delicate colonies resembling sparsely branched feathers ~2 cm tall; usually growing in clusters, pale tan. Gastrozooids widely spaced on side one side of each side branch. Abundant but inconspicuous, on rocks among other sessile invertebrates and algae. Geogr. Range: Alaska to Baja Synonyms: Similar species: Aglaophenia is much more robust & larger than Plumularia. Several species of Plumularia occur in Monterey but require a microscope to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Obelia spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Proboscoida, Family Campanulariidae Bushy delicate colony up to 15 cm tall with side branches arising in all planes; pale tan. Gastrozooids tiny; free-swimming medusae released from reproductive gonozooids. Abundant on any hard surface; good colonizer of newly open substrate. Geogr. Range: genus occurs world-wide Synonyms: Similar species: several species of Obelia occur in Monterey but require microscopic examination to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Orthopyxis spp. Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Proboscoida, Family Campanulariidae Unbranched polyps arise from basal stolon overgrowing red algae and other ephemeral substrata, pale tan. Can be very abundant; most conspicuous on low-lying red algae such as Rhodymenia pacifica, several species. Geogr. Range: Alaska to southern California Synonyms: Similar species: several species of Orthopyxis occur in Monterey, but require microscopic examination to distinguish. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Chrysaora colorata (Russell, 1964) Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Pelagiidae Large medusa 70 cm diameter, pale with distinctive dark markings on bell and margin. Unpleasant sting. Can be common but does not form large surface aggregations; pelagic; specimens encountered offshore of kelp forests often damaged. Geogr. Range: central California to southern California Synonyms: Pelagia colorata Similar species: C. colorata often misidentified as Chrysaora noctiluca which is a southern, warm water spp. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Chrysaora fuscescens Brandt, 1835 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Pelagiidae Large medusa 30 cm diameter; bell yellow-brown to reddish brown with 24 dark tentacles around margin. Oral arms long & folded, dark with white/clear frills. Unpleasant sting. Can form large aggregations, especially late summer through winter; pelagic offshore from kelp forests. Geogr. Range: Alaska to Baja. Synonyms: Chrysaora helvola, C. gilberti Similar species: often misidentified as Chrysaora melanaster. \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Phacellophora camtschatica Brandt, 1835 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Ulmaridae Large medusa 60 cm diameter; clear to yellowish bell with central yellow gonads; 16 clusters of tentacles, 16 sensory rhopalia around margin of bell; small individuals often with milky white bell. Oral arms short & highly folded, said to resemble a fried egg. Mild sting. Does not usually form large aggregation; pelagic offshore from kelp forests. Geogr. Range: Kamchatka to Alaska & south to Chile. Synonyms: Similar species: \| back to spp. list \| more info \| refs. \| kelp forest index \|
	Aurelia labiata Chamisso & Eysenhardt, 1821 Phylum Cnidaria, Class Scyphozoa, Order Semaeostomeae, Family Ulmaridae Shallow bell to 40 cm fringed with many fine tentacles; 4 short oral arms; opaque white, usually with 4 horseshoe-shaped gonads visible. Very mild sting. May form dense aggregations (late summer / autumn), pelagic offshore from kelp forests. Geogr. Range: Oregon to central California Synonyms: Similar species: often misidentified as the non-native Aurelia aurita. \| back to spp. list \| more info \| refs. \| kelp forest index \|