350 
PACIFIC SCIENCE, VoL XXII, July 1968 
The hollow branches were found to contain 
clusters of 20-30 fish eggs with living embryos 
inside. The eggs were probably those of a small 
blenny or goby that normally deposits its eggs 
within sponges. All the eggs found died before 
hatching. 
Assuming that these eggs are from a sponge- 
dwelling fish, this example of fish-sponge in- 
quilinism is the first recorded for Homaxinella 
sp. and for the Pacific Ocean. 
DISCUSSION 
The four species of sponge studied showed 
great variation in the community of associates 
found. These variations were due to the differ- 
ent habitats of the sponges and also to different 
properties of the sponges that acted as attrac- 
tants and inhibitors. Other species of sponge 
adjacent to those studied harbored fewer associ- 
ates, probably because they lacked factors that 
attracted the associates, or they possessed some- 
thing that discouraged them. 
In comparing Halichondria panicea, Micro- 
ciona prolifera, and Suberites lata, which oc- 
curred in progressively deeper waters, the com- 
munity of associates was progressively more 
stable, consistent, and predictable and its com- 
position fluctuated less from sample to sample. 
The intertidal H. panicea showed great varia- 
tion in community density and composition, in- 
dicating that these parameters were related to 
the fauna of the immediate area. When two 
species of sponge (e.g., S. lata and H. panicea ) 
occurred next to each other, the tougher, more 
impenetrable species harbored fewer associates. 
The majority of associates did little harm to 
the host sponge. The numerous Crustacea may 
have benefited the sponges by cleaning them. 
Such a relationship can be considered mutualist- 
ic. The intracellular algae of H. panicea were 
also probably mutualistic with the sponge. The 
most deleterious associate was Archidoris mon- 
tereyensis, which, along with other predators, 
fed voraciously on H. panicea. Some of the tube 
worms and amphipods associated with M. 
prolifera caused minor structural damage to the 
sponge. The sponge-dwelling fish whose eggs 
were deposited within Homaxinella sp. obvious- 
ly benefited from the water currents and shelter 
of the sponge, while it did not appear to inhibit 
the growth or function of the host. 
CONCLUSIONS 
Four species of sponge from the coasts of 
Oregon and Washington were studied for 
associates. A large number and great variety of 
associates were found. The great numbers of 
sponge associates suggests that sponges are im- 
portant to the ecology of the numerous associ- 
ates. The relationships of these associates fall 
into four general categories: (1) inquilinism, 
or lodging, within or upon the sponges; (2) co- 
existence of two organisms on the same sub 
strate as a result of simultaneous growth; (3) 
predation or grazing; (4) mutualism. 
The 32 samples of Halichondria panicea 
harbored 6,098 organisms, representing 68 
species, with a mean density of 1.15 organisms 
per cm 3 of sponge. The 15 samples of Micro- 
ciona prolifera had 9,581 associates with a mean 
density of 0.80 organism per cm 3 . The 14 sam- 
ples of Suberites lata had 150 associates at a 
mean density of 0.1 organism per cm 3 of 
sponge. 
Significant differences in composition and 
density among the sponge communities were 
attributed to the different habitats of the species 
studied, and to differences in the exudates and 
consistencies of the species of sponge. The nudi- 
branch Archidoris montereyensis, which fre- 
quently occurred on Halichondria panicea, ex- 
hibited a distinct preference for that species in 
laboratory experiments. 
The tubular sponge Homaxinella sp. harbored 
the eggs of a fish, which was assumed to be an 
unidentified, sponge-dwelling inquiline. 
ACKNOWLEDGMENTS 
Space and facilities were provided by Prof. 
Ivan Pratt at his laboratories in Corvallis and at 
the Marine Science Center, Newport. The fol- 
lowing persons provided identifications of many 
of the sponge associates: Dr. Joel Hedgpeth 
(insects), Dr. J. Laurens Barnard (amphipods), 
Mr. Danil Plancock (annelids). 
REFERENCES 
Caullery, M. 1952. Parasitism and Symbiosis. 
(A. M. Lysaught, trans.) Sidgwick and Jack- 
son, London. 340 pp. 
Dales, R. Phillips. 1957. Commensalism. In: 
