Polyorchis penicillatus
(Eschscholtz, 1829)
Common name(s): Red-eye jellyfish,
bell medusa, bell-shaped
jellyfish
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Synonyms:
Polyorchis penicellata |
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Phylum Cnidaria
Class Hydrozoa
Order
Hydroida
Suborder Athecata
Family Polyorchidae |
Polyorchis penicillatus from Rosario
Bay. About 3 cm long. |
(Photo by: Dave Cowles,
June 2006) |
Description: This
hydromedusa
has a bell that is at least as high as it is wide, with many (around
100)
evenly-spaced, unbranched tentacles around the bell margin.
The tentacles
may be contracted to very short (especially when the animal is actively
swimming) or extended to twice the bell length (especially when the
animal
is drifting). As with many hydromedusae,
it has a clearly developed velum.
Nematocysts
on
the tentacles are not grouped into rings. Ocelli
(eyespots) around the bell margin, at the base of the tentacles, are
ringed
with red which can be clearly seen. It has 4 unbranched radial
canals which have many (15-25 pairs of) lateral diverticula.
The ring
canal
may or may not have several short centripetal
diverticula.
The fingerlike or sausagelike gonads hang down from the subumbrellar
surface, under the radial
canals near the juncture of the stomach with the radial
canals, in 4 groups (photo).
Usually there
are less than 15 gonads. The bell is transparent with white
parts
but the gonads and some other internal organs may be yellow,
yellow-brown,
reddish-brown, or purple. The manubrium,
which is long and has 4 short frilly lips, hangs from a rounded
"gastric
peduncle". Average size is 2-3 cm, and up to 5 (10) cm
tall.
Older individuals may have green algae growing on the exumbrella.
How to Distinguish from
Similar Species:
Ptychogena lactea and Staurophora mertensi
are similar except
that their bells are much wider than high and their gonads do not hang
down into the
subumbrellar
space. Polyorchis haplus does not have
lateral diverticula
on the radial
canals.
Geographical
Range: Aleutian Islands,
Alaska to Sea of Cortez, Mexico
Depth Range:
Habitat:
A coastal species (nearshore),
especially in bays.
Biology/Natural History:
This is a
common hydromedusa
along the west coast. It can often be seen in midwater but
more often
swims near the bottom, especially around eelgrass. The jelly
eats
caprellid
amphipods and other small crustaceans which are common on
eelgrass,
as well as worms and crustaceans from the bottom and small
plankton.
Sexes are separate. The polyp stage of this species is either
very
small or unknown, and the medusa may develop directly from a planula
larva.
This species is large for a hydromedusa,
and some of the largest hydromedusae
are in this genus. The medusa is common in some years and
nearly
absent in others.
References:
Dichotomous Keys:
Flora
and Fairbanks, 1966
Kozloff
1987, 1996
Smith
and Carlton, 1975
General References:
Gotshall,
1994
Harbo,
1999
Johnson
and Snook, 1955
Kozloff,
1993
Morris
et al., 1980
Niesen,
1994
Niesen,
1997
Ricketts
et al., 1985
Wrobel
and Mills, 1998
Scientific Articles:
Web sites:
General Notes and
Observations: Locations, abundances,
unusual behaviors:
In this closeup view the red spots at the ocelli, the pendant gonads,
the long manubrium
can be clearly seen. The lateral diverticula
are also visible on
several radial canals.
This freely swimming individual has its tentacles extended out farther
than the one above does. Photo by Dave Cowles, July 2008
Another individual, photographed 2012. Note the
long, dangling
gonads inside the bell. Two individuals dancing in a planktonkreisel. Photo by Dave Cowles, July 2020
Click HERE
for a 1-minute movie of this species swimming in a planktonkreisel,
taken summer 2020. Some individuals are greenish-colored due to algae
adhering to their outer surfaces.
Authors and Editors of Page:
Dave Cowles (2006): Created original page
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