Husbandry of the black jelly (Chrysaora achlyos),
a newly discovered scyphozoan in the eastern North
Pacific Ocean
Maintenance de la Méduse Noire (Chrysaora achlyos),
un scyphozoaire récemment découvert dans le Nord-Est
de l’océan Pacifique
M. SCHAADT1, L. YASUKOCHI2, L. GERSHWIN3, D. WROBEL4
1
Cabrillo Marine Aquarium, San Pedro, CA 90731, USA
2
Birch Aquarium at Scripps, La Jolla, CA 92093, USA
3
University of California, Berkeley, CA 94706, USA
4
Monterey Bay Aquarium, Monterey, CA 93940, USA
ABSTRACT
The black jelly (Chrysaora achlyos) has been reported four times in the 1900’s. First
described in 1997, it is believed to be the largest invertebrate named this past century.
During the summer of 1999, adult medusae washed ashore in large numbers near San
Diego, California, USA, and as far north as Los Angeles, California. Gametes were
harvested from mature medusae. In vitro fertilization resulted in the planula, polyp, and
ephyra stages being seen for the first time. Successful husbandry protocols have
resulted in ephyrae growing into young medusae kept in modified aquaria for public
display. Husbandry techniques developed during this study can be used to add new
schyphozoan cultures to the growing list now available to public Aquariums.
RÉSUMÉ
La Méduse Noire (Chrysaora achlyos) a été signalée à quatre reprises au début du
siècle. Décrite pour la première fois en 1997, elle serait la plus grande espèce
d’invertébré découverte au XXe siècle. Durant l’été 1999, des méduses noires adultes
s’échouèrent en grand nombre sur une zone s’étendant de San Diego à Los Angeles,
Californie, USA. Des gamètes furent récoltés sur des spécimens adultes. De leur
fertilisation in vitro résultèrent successivement des planules, des polypes, puis des
éphyrules observées pour la première fois. Grâce à un protocole d’élevage approprié,
les éphyrules grandirent pour devenir de jeunes méduses, présentées au public dans des
aquariums adaptés. Les techniques d’élevage développées pour les besoins de cette
étude peuvent être reproduites pour que cette espèce s’ajoute à la liste grandissante des
scyphozoaires présentés dans les Aquariums publics.
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Black Jelly Chrysaora achlyos
During the summer of 1999, dozens of large scyphozoan medusae (Fig. 1)
washed ashore in San Diego and Los Angeles, California. This was the fourth
time in the 20th century this medusa was reported in the literature (Crowder,
1926; Halstead, 1965; and Martin and Kuck, 1991).
The medusa was first described by Martin et al., in 1997 and named
Chrysaora achlyos (achlyos - after the Greek god of obscurity). The holotype
specimen (Acc. No. 89.28.1) is in the preserved specimen collection of Cabrillo
Marine Aquarium (CMA). It is commonly referred to as the black jelly due to
the dark burgundy coloration of the bell. It is believed to be the largest
invertebrate named during the 20th century reaching bell diameters of over 1 m
and oral arm lengths of over 10 m.
In vitro Fertilization
During the 1990’s, in-vitro fertilization procedures were performed on moon
jellies (Aurelia spp.) and purple-striped jellies, Chrysaora colorata (previously
known as Pelagia colorata – see Gershwin and Collins, 2001) at CMA. When
black jellies washed ashore in 1999, the same techniques were employed by
staff and volunteers at CMA and at Birch Aquarium at Scripps in San Diego in
collaboration with a researcher from University of California Berkeley.
Small bits of gonadal material were taken with forceps from the subgenital
pit area of mature adult medusae. The sex of the individuals was confirmed
using a dissecting microscope (Fig. 2). Eggs are easily seen as spheres
embedded in the female gonadal tissue. Sperm are inside oddly shaped packets
giving the male gonadal tissue a uniform, granular appearance. Eggs and sperm
were combined in petri dishes with filtered seawater and kept covered on a
water table at 15 degrees centigrade.
Within 48 hours, planulae were observed slowly rotating through the water.
The planulae were removed to a small jar with a Plexiglas plate lying at an angle
against the side. Within the next 48 to 96 hours, planulae settled on the
underside of the plate (Fig. 3).
Planulae and polyps were shared with the Monterey Bay Aquarium.
Life Cycle
The life cycle of the black jelly is similar to other scyphozoans in that a freeswimming medusa stage alternates with an attached polyp stage. Polyps clone
new polyps by producing podocysts. At certain times of the year some polyps
undergo a form of cloning called strobilation, resulting in the release of ephyrae.
The newly released ephyrae are about 1-2 mm in diameter and closely resemble
ephyrae of purple-striped jellies. Ephyrae have been grown to adult medusae
with 20 cm bell diameters, 50 cm long oral arms, and 100 cm long tentacles.
The adult medusae bell and frilly oral arms have light brown to dark burgundy
pigmentation with long pale tentacles (Fig. 4).
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Husbandry
Feeding
Newly settled polyps are kept in filtered, 15° C seawater in a closed system
jar with daily 100% water changes. After the first week, they are put into a jar
filled with Rotorich enriched rotifers (Brachionus sp.) for about one hour per
day then returned to a closed system jar with clean seawater and a small amount
of rotifers. This method helps keep water quality within acceptable limits. At
about one month old, they are put into a tank with flowing seawater at 15° C and
their diet is supplemented twice a day with Super Selco enriched brine shrimp
(Artemia sp.). Care is taken not to overfeed, which seems to allow for growth of
opportunistic organisms (like diatoms, polychaete worms, and hydrozoan or
other scyphozoan polyps) that will out-compete or overgrow black jelly polyps.
Under lab conditions, strobilaton first occurs when the polyps reach one to
four months of age (Fig. 5). Newly released ephyrae (Fig. 6) are removed from
the polyp tank and kept in closed system jars with gentle bubbling to keep
ephyrae suspended. The water is changed at least every other day. Prior to
changing the water the ephyrae are removed to a small finger bowl and allowed
to feed on highly concentrated, enriched rotifers and finely chopped moon jelly
mesoglea for about one-half hour. The mucus producing epithelial layer of the
moon jelly bell is removed with a strong spray of seawater thus reducing the
chance of entrapping tiny, feeding ephyrae. After feeding for about one-half
hour, the ephyrae are put back into closed system jars with filtered seawater. A
small amount of rotifers are kept with the ephyrae to allow feeding between
water changes.
At the post-ephyra stage (Fig. 7), about one month old or when the bell
develops and oral arms become evident, the diet is supplemented with moon
jelly ephyrae and larger pieces of adult moon jelly bell. The post-ephyrae are
removed to a finger bowl and given the opportunity to feed for about one-half
hour then moved back into jars with filtered seawater. Again a small amount of
rotifers are kept with the post-ephyrae to allow feeding between water changes.
Juvenile medusae (1-7 cm in bell diameter) (Fig. 8) are fed larger pieces of
moon jelly as well as moon jelly ephyrae and enriched brine shrimp nauplii.
Tank Requirements
Plates with attached polyps are suspended in a small (1 L) clear plastic box.
The overflow empties into a smaller clear plastic box with a screen prior to the
overflow so as not to lose ephyrae. Newly released ephyrae are moved into
small (1.5 L), round, clear plastic containers. These round containers have an air
source that delivers small bubbles that help keep the ephyrae suspended.
Juvenile medusae (1-3 cm bell diameter) are kept in small (20 L) acrylic
aquaria that are modified to serve as pseudokreisels. Young adults (7+ cm bell
diameter) are on public display in a stretch planktonkreisel (1 m tall, 2 m long
and 28 cm front to back) (Fig. 9).
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Compatibility With Other Jellies
Medusae of purple-striped jellies are raised together with black jellies once
they reach a bell diameter of about 2 cm.
Safety
Nematocyst patches are obvious in the ephyrae stage of the black jelly but
not dangerous to humans. Adult black jelly medusae stings deliver less potent
venom than Chrysaora quinquecirrha, a phylogenetic congeneric cousin
(Radwin, Gershwin and Burnett, 2000).
Life Span
Black jellies can be grown from ephyrae to young adults in 2 to 6 months,
depending on the intensity of feeding and cleaning efforts. Once the young
adults reach bell diameters of about 15 to 20 cm, the bell shows signs of
deterioration and begins to shrink. We are investigating this phenomenon and at
this time we believe that upon reaching about the inside dimension of the stretch
planktonkreisel (Hamner, 1990), the jellies touch surfaces much of the time
which results in bell tissue damage and inefficiency of feeding efforts.
Future
We are planning for the future.
Polyp Cultures
Polyps on the plates have continued to produce podocysts. Podocysts
eventually grow into new polyps (Fig. 10). This cloning of polyps has been very
slow resulting in few new polyps. New polyp plates can be sent to other
aquariums to start their culture.
In-vitro of Tank-raised Medusae
We are continuing our efforts at in-vitro fertilization of the tank-raised
medusae. To date, we have successful fertilization events but very few planulae
and no settled polyps. We will continue efforts at in-vitro fertilization with the
goal of producing more polyp plates, some of which can be shared with
aquariums, zoos and other educational institutions.
ACKNOWLEDGEMENTS
The authors extend their appreciation to Freya Sommer who taught us invitro fertilization techniques for scyphozoans, Stephane Hénard who graciously
provided the French translation of the title and abstract for this paper, to Norbert
Wu for Figure 1, and to Gary Florin who provided many of the photographs.
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
REFERENCES
CROWDER, W., 1926.- The life of the moon-jelly-. Nat. Geogr. 50:187-202.
GERSHWIN, L. and A.G. Collins, Apr. 2001.- A preliminary phylogeny of
Pelagiidae (Cnidaria: Scyphozoa), with new obervations of Chrysaora
colorata comb-. J. Nat. Hist.
HALSTEAD, B.W., 1965.- Phylum Coelenterata-. Poisonous and Venomous
Marine Animals of the World, vol. I. Invertebrates. U.S. Government
Printing Office, Washington, D.C. 994: Plate 43. 297-535 pp.
HAMNER, W.N., 1990.- Design developments in the planktonkreisel, a plancton
aquarium for ships at sea. J. Plank. Res. 12 (2): 397-402.
MARTIN, J.W., L. GERSHWIN, J.W. BURNETT, D.G. CARGO, and D.A. BLOOM,
1997- Chrysaora achlyos, a remarkable new species of scyphozoan from the
Eastern Pacific-. Biol. Bull. 193: 8-13.
MARTIN, J.W., and H.G. KUCK, 1991.- Faunal associates of an undescribed
species of Chrysaora (Cnidaria, Scyphosoa) in the Southern California Bight,
with notes on unusual occurrences of other warm water species in the area-.
Bull. South. Calif. Acad. Sci. 90 (3): 89-101.
RADWIN, F., L. GERSHWIN and J.W. BURNETT, 2000- Toxinological studies on
the nematocyst venom of Chrysaora achlyos. Toxicon-. 38:1581-1591.
Captions for figures
Figure 1. Chrysaora achlyos, the black jelly with adult garibaldi.
Figure 2. Gonads of C. achlyos. (a) gonadal tissue with eggs. (b) gonadal tissue
with sperm in packets. Magnification of both photographs is 40X.
Figure 3. Newly settled polyps of C. achlyos. Magnification is 100X.
Figure 4. Young adult C. achlyos medusa.
Figure 5. Strobilating polyps of C. achlyos. Magnification is 40X.
Figure 6. Ephyra of C. achlyos. Magnification is 50X.
Figure 7. Post-ephyra of C. achlyos. Magnification is 20X.
Figure 8. Juvenile medusa of C. achlyos. Magnification is 4X.
Figure 9. Young adult C. achlyos medusae on public display in a
planktonkreisel. Bell diameters are 15cm.
Figure 10. Polyps and podocysts of C. achlyos. Magnification is 40X.
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)
Bulletin de l’Institut océanographique, Monaco, n° spécial 20, fascicule 1 (2001)