Class Hydrozoa
Subclass Anthoathecata (=Anthomedusae, Athecata)
- Garveia annulata
- Hydractinia milleri
- Pinauay marina
- Stylaster californicus
- Stylantheca porphyra
- Polyorchis spp.
Subclass Leptothecata (=Leptomedusae, Thecata)
Subclass Anthoathecata (=Anthomedusae, Athecata)
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.
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, but intermittent 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.
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.
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.
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.
Polyorchis spp.
Phylum Cnidaria, Class Hydrozoa, Subcl. Anthoathecata, Order Capitata, Family Polyorchidae
Medusa with tall bell to 2-6 cm high; 4 radial canals; numerous tentacles with pigmented ocelli at base; polyp phase unknown.
Most common in protected areas such as seagrass flats & harbors; spends most of time perched on bottom, swimming upward then drifting back down catching demersal zooplankton & benthic crustaceans.
Geogr. Range: Aleutians to Gulf of Calif (P. penicellatus)
Synonyms:
Similar species: Polyorchis penicillatus (Eschscholtz, 1829) is more common & larger with lateral side branches on its 4 radial canals; P. haplus Skogsberg, 1948 is smaller, less common & lacks lateral branches on radial canals.
Subclass Leptothecata (=Leptomedusae, Thecata)
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.
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.
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.
Aequorea spp.
Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Conica, Family Aequoreidae
Large transparent hydromedusa to 8 cm diameter; numerous radial canals bearing gonads; many tentacles around margin of bell; bioluminescent.
Intermittently common in waters offshore of kelp forests; preys on other medusae, ctenophores, pelagic tunicates. Polyp phase rarely encountered in the field but easily cultured in the lab. Medusa form is source of green-fluourescent protein (GFP) & aequorin (bioluminescent protein) used in research.
Geogr. Range: Alaska to California
Synonyms:
Similar species:
Image: small ctenophore in foreground (out of focus) is Pleurobrachia.
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.
Orthopyxis spp.
Phylum Cnidaria, Class Hydrozoa, Subcl. Leptothecata, Order Proboscoida, Family Campanulariidae
Polyps on short unbranched stalks arising 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.