A Comparative Study of Craspedacusta sower byi 
and Calpasoma Dactyloptera Life Cycles 1 
Donald C. Matthews 2 
In a previous publication (Matthews, 
1963), immature medusae and mature hydranths 
of Craspedacusta sowerbyi were reported from 
aquaria of Mr. Mack Saki, a commercial guppy 
breeder of Honolulu. Whereas these medusae 
lived only three days, the hydranths persisted 
from October I960 to November 1961 and, by 
hydranth and frustule budding, produced hun- 
dreds of hydranths, but no medusae. 
Their reoccurrence on March 19, 1962 in 
aquaria of Mr. Saki (but not in mine) seemed 
again related to the water plant Ceraptopterus 
thalictroides (Matthews, 1963:20), but it har- 
bored no hydranths. However, on internodes 
and leaf axils of Elodea canadensis, hydranths 
abounded. As before, immature medusae lived 
three days. The hydranths cultured in Petri 
dishes until December 1962 afforded material 
for continued study of factors reportedly re- 
sponsible for medusa-bud formation. 
Following Reisinger’s (1934, 1957) meth- 
ods, elevation of temperature from 20 C to 25- 
27 C failed to initiate medusa buds. Likewise, no 
maximal temperatures for hydranth, frustule, or 
medusa budding were found (McClary, 1959), 
nor were seemingly antagonistic budding stages 
altered either by feeding rates or temperature 
levels (Lytle, 1961)- In short, cultures were 
cooled and warmed, starved and surfeited, iso- 
lated and crowded, coddled and coerced, without 
one medusa or tentacular hydranth resulting. 
As might be expected, no hydranths were living 
by December 30, 1962. 3 
Quite by chance, on 30 untreated "bunches” 
1 Contribution No. 242, Hawaii Institute of Marine 
Biology, Honolulu, Hawaii. Manuscript received Sep- 
tember 29, 1964. 
2 Department of Zoology, University of Hawaii, 
Honolulu. 
3 While I was searching for new material, both 
atentacular and tentacular hydranths were undoubt- 
edly present all the time in aquaria on my own lanai, 
where subsequently they were found! 
of E. canadensis purchased March 3, 1963, aten- 
tacular and tentacular hydranths were observed. 
Although most atentacular hydranth stages of 
this study are from the Saki material, all ten- 
tacular hydranth stages are from this new source 
(March 3, 1963 to date). 
For 18 months (March 1963 to August 1964) 
atentacular and tentacular hydranths have lived 
in my laboratory, either together in the same 
culture or isolated in separate cultures; and so 
striking is their resemblance that, although a 
tentacular hydranth stage of C. sowerbyi had 
not been mentioned previously (Browne, 1906; 
Crowell and Lytle, 1955; Dejar, 1934; Dunham, 
1941; Fowler, 1890; Goette, 1909, 1920; Gaw 
and Kung, 1939; Hadzi, 1959; Kramp, 1950; 
Kuhl, 1947; Lytle, 1961; Matthews, 1963; Mc- 
Clary, 1959; Moser, 1930; Payne, 1924, 1926; 
Pennak, 1959; Potts, 1906; Reisinger, 1934; 
Romanes, 1881; Ryder, 1885; Uchida, 1955, 
1963; and Woodhead, 1943), there seemed 
little doubt that this was but an aberrant form 
of a single, dimorphic species. 
The purpose of this paper is threefold: ( 1 ) to 
verify Buchert’s (I960) atentacular and tentac- 
ular stages, ( 2 ) to question, in light of my find- 
ings, the relationship he ascribes to certain of 
these stages, and ( 3 ) to report, for the first time 
in Hawaii, stages in the life cycle of Calpasoma 
dactyloptera (Fuhrmann, 1939). 
I A. ATENTACULAR HYDRANTHS OF 
MIXED CULTURES 
Small portions of Elodea canadensis with at- 
tached atentacular and tentacular hydranths 
were placed in Petri dishes containing 30 ml of 
aged tap water. Although some cultures were 
allowed to evaporate almost completely, most 
were maintained at the 30 ml level. 
Temperatures varied from 20.5 C to 28.0 C, 
with the mean at 26.5 C. The pH ranged from 
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