Polyorchis Penicillatus Class: Hydrozoa, Hydroidolina

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Polyorchis penicillatus Class: Hydrozoa, Hydroidolina

Taxonomy: Polyorchis penicillatus was orig- latinous. inally identified as Melicertum penicillatum Radial canals: There are four by Eschscholtz in 1829. It was re-described radial canals, each with 15–25 pairs of short by Arai and Brinckmann-Voss in 1980 based diverticula (blind side branches). The divertic- on the lateral branches on its radial canals ula are longer than twice the width of the radi- and its simple gonads. P. minuta, P. mon- al canal (Fig. 1) (Mills et al. 2007). tereyensis, P. campanula, and P. pinnatus Ring canal: The ring canal is are all synonyms for P. penicillatus simple (i.e., un-branching) and contains the (Schuchert 2015c). Higher classification of tentacles. The ocelli are on extensions at the this species has also undergone revision. bases of the tentacles (Fig. 2). The family Polyorchidae was determined to Ocelli: Ocelli are pigment-cup be a synonym of family Corynidae in 2010 eyespots suspended from the ring canal (fig. (Schuchert 2015b). The order Hydroida was 2). The ocelli can measure gradients in light determined to be synonymous with subclass intensity (Martin 2002), which is thought to Hydroidolina in 2004 (Schuchert 2015a). facilitate diel migration in P. pencillatus. Mouth: The manubrium extends Description from a short, pronounced gelatinous gastric General Morphology: The only known form peduncle (Fig. 1), and is as long as the bell of P. penicillatus is the gelatinous hydrome- cavity. It has four oral lips densely armed with dusa, with a deep bell and many tentacles. nematocysts that form a distinct marginal Within the bell are radial canals that run from band (Fig. 1). the top of the bell to the bell margin, where Tentacles: Polyorchis penicilla- they are connected by a ring canal (Fig. 1). tus can have up to 160 tentacles, set in a sin- Medusa: gle whorl along the bell margin on the ring ca- Size: Polyorchis penicillatus is higher nal. The tentacles are not in clusters, and they than it is wide. Individuals can reach 60 mm are unbranched (Mills et al. 2007). The num- in height (Mills et al. 2007) and average 20 ber of tentacles increases rapidly with age mm in width (Ricketts et al. 1985). (Skogsberg 1948). Color: Most P. penicillatus are trans- Velum: The velum is a thin layer parent white with purple-red eyespots. The inside the bell rim and contracts during swim- color of the gonads (sausage-shaped and ming. hanging from each radial canal, see Gon- Gonads: There are four to eleven sau- ads) and other organs is variable and rang- sage-shaped gonads (with an average of es from yellow brown to purple (Ricketts et eight) hanging from each radial canal as it al. 1985). joins manubrium (Fig. 1). They produce either Body: eggs or sperm (dioecious). Bell: The bell is higher than it is wide. Cnidae: Stinging cells, characteristic of all The membrane is thin, delicate, and not ge- cnidarians, (Fig. 4) are found on the manubri-

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected]

Piazzola, C.D. and L. Hiebert. 2015. Polyorchis penicillatus. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biol- ogy, Charleston, OR.

um and tentacles. Each contains a poison they are in P. penicillatus (Brinkmann-Voss sac and a stinging thread. According to Arai 2000). and Brinckmann-Voss (1980), the cnido- Ecological Information blasts (Fig. 3) are microbasic p- Range: The type locality is most likely San mastigophores in juveniles, and stenoteles Francisco Bay. Polyorchis penicillatus has and desmonemes in adults. However, there been found from the Aleutian Islands to the is variation in cnidoblast naming schemes Sea of Cortez (Mills et al. 2007). between researchers. Local Distribution: Locally, P. penicillatus is Polyp: The polyp form of P. penicillatus is found in the Coos Bay estuary. unknown. All attempts to raise P. penicillatus Habitat: Medusae are found in the plankton larvae in the lab have failed. It is possible near the surface of the water. They are often that the polyp form is symbiotic on or in an- found in protected or shallow bays and other organism (Mills et al. 2007). around docks (Mills 1981; Mills et al. 2007), Possible Misidentifications as well as in beds of Zostera species. (Mills The family Polyorchidae includes bell- and Strathmann 1987). shaped anthomedusae with deep bodies. Salinity: Collected at salinities of 30. Polyorchis penicillatus Juveniles lack a peduncle, which develops Temperature: is found as they mature. Mature specimens also in both cold (Vancouver, British Columbia, have four fringed oral lips, four radial canals, Canada) and temperate water (San Francis- and gonads with either a sausage or spiral co, California). However, it has been found as shape (Arai and Brinckmann-Voss 1980). far south as the Gulf of California (Rees and Two other species of Polyorchidae Larson 1980; Mills 2001; Mills et al. 2007). occur in our area. Polyorchis haplus is the Tidal Level: Individuals are found throughout smallest of the local Polyorchidae (up to 20 the water column, though they spend most of mm high), and has the fewest tentacles (up their time within several meters of the bottom. Polyorchis penicillatus to 30). It also lacks knob-like diverticula on Associates: is parasi- Achelia alas- its radial canals (Mills et al. 2007). Scrippsia tized by larvae of the sea spider kensis pacifica, the largest of the family (75 mm in Japan (Russel and Hedgpeth 1990) Hyperia medu- high), has a peduncle that reaches halfway and by the Hyperiid amphipod sarum down the bell (much longer than P. penicilla- in Puget Sound, Washington (Towanda tus). They also have many more tentacles and Thuesen 2006). (about 256) that are set in 7 whorls rather Abundance: These are the most common than one, and that can attach to the bell large Anthomedusa in our area, but are spec- above, rather than just at, the radial canal. ulated to be less abundant across their distri- Other tall, bell-shaped medusae are bution, possibly due to increased urbanization either very small (like Aequorea, this guide), of coastal regions as well as heavy take by or have greatly different tentacles or manu- scientists for research (Mills 2001). brium, as in Coryne or Sarsia. However, ju- Life-History Information veniles of P. penicillatus and Sarsia bella Reproduction: Like other hydrozoans, P. can be mistaken for one another. Sarsia bel- penicillatus has a two-phased reproductive la has radial rows of two vertically aligned cycle, involving both asexual and sexual stag- nematocyst patches while P. penicillatus has es. Its sexual (medusa) stage is dioecious. at least three patches per row. Additionally, Efforts to raise P. penicillatus in the lab have the nematocysts are smaller in S. bella than produced planula larvae, but they would not A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected]

settle (Rudy pers. obs.). A single colony of their manubrium. Sometimes, they will hop on P. penicillatus has been described, but was the sediment, likely to stir up possible prey or later identified as Sarsia bella (Brinkmann- move to a new location (Mills 1981, 2001). In Voss 1977, 2000). The medusae are highly the water column, they use “sink fishing” to fecund and produce 10,000 eggs a day for find their prey. During sink fishing, the medu- much of their lives (Mills 2001). One function sae extend their tentacles out from their bell of their diel migration could be to synchro- and let the distal ends sink downward. They nize spawning locations. Polyorchis penicil- either maintain their position in the water col- latus spawn in the hour immediately after umn or sink slowly and catch prey with their dark, a process that usually lasts less than tentacles. When a prey item touches a tenta- ten minutes (Arkett 1984). The resulting cle, the medusa will use that tentacle to bring eggs are transparent and 100 µm in diame- the prey to the manubrium, though large prey ter (Mills and Strathmann 1987). sometimes require more tentacles; this pro- Larva: Polyorchis penicillatus produces cess causes cessation in swimming and planula larvae. Planulae are usually oval or crumpling (Arkett 1984). club-shaped and ciliated evenly all over their Predators: Eaten by the hydromedusa Ae- bodies. These larvae are non-feeding and quorea, as well as fishes, sea anemones free-swimming. They are armed with nem- (Urticina sp., Pachycerianthus sp.) and crabs atocytes, but lack an apical ciliary tuft and (Cancer productus). Most of their predators septa (see Fig. 3, Sadro 2001). are benthic (Arkett 1985). Juvenile: Juveniles have 24 small, distinct Behavior: Individuals exhibit a small diel mi- patches of cnidocysts on their exumbrella gration (based on dusk and dawn) concomi- (the outer surface of the bell). There are six tant with demersal plankters. During the day, patches per quadrant, arranged in three nearly all the medusae stay within a meter of rows of two and spaced evenly over the sur- the bottom, but at night they diffuse through- face of the bell. There is a red or a black out the water column, though even then they ocellus on each tentacle bulb. They only usually stay within several meters of the bot- have four tentacles, and the bell apex is tom. This migration is heavily food-driven rounded. They are only 1-2 mm in diameter (Arkett 1984). They also exhibit a shadow re- and have been found around marina floats sponse, in which rapid changes in light trigger and over eelgrass beds (Mills et al. 2007). a burst of swimming and tentacle contrac- Longevity: The longevity of P. penicillatus tions. Though this reaction was initially is unknown. thought to be an escape method (Martin Growth Rate: Individuals grow rapidly in the 2002), further research suggests it may be spring, when food is abundant (Larson related to their diel migration (Arkett 1985). 1986). Additionally, this response does not occur in Food: Polyorchis penicillatus eats large de- young medusae (Arkett 1985). mersal crustaceans and other planktonic or- Bibliography ganisms, especially copepods, caprellid and gammarid amphipods, and tanaids (Arkett 1. ARAI, M. N., and A. BRINKMANN-VOSS. 1984). They feed in both the water column 1980. Hydromedusae of British Columbia and on the bottom, using different methods and Puget Sound. Canadian Bulletin of for each (Mills et al. 2007). On the bottom, Fisheries and Aquatic Sciences. 204:1- they perch on their tentacles and eat benthic 192. organisms by touching the sediment with 2. ARKETT, S. A. 1984. Diel vertical migra-

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Updated 2015 C.D. Piazzola and L. Hiebert