348 
PACIFIC SCIENCE, VoL XXII, July 1968 
to recover the associates. The sponges were 
pulled apart and examined under a binocular 
microscope (120 X)- The inhabitants found 
were preserved in AFA for further examination 
and identification. The results are summarized 
in Table 1. 
OBSERVATIONS AND EXPERIMENTS 
Suberites lata 
S liberties lata occurred in Hood Canal, Wash- 
ington, in a distinct zone of its own at a depth 
of 5-10 meters (MLLW) on nearly vertical 
rocks that were lightly covered with a fine mud. 
The water conditions in this narrow inlet were 
quite stable and calm. 
The consistency of the sponge was very tough 
and impenetrable. It harbored very few orga- 
nisms. The 15 samples studied had 150 associ- 
ates, representing 25 species and 6 phyla. The 
densities of the associates varied from 0.001 to 
0.03 (mean 0.1) organisms per cm 3 of sponge 
(Table 1). The sparsity of inhabitants was most 
likely due to the toughness of the sponge. The 
predominant organisms were the small spionid 
polychaete Polydora socialis which was found 
in every Hood Canal sample, the gammarid 
Aoiroides columbiae, the ectoproct Crista sp., 
and unidentified, filamentous green algae. 
P. socialis was the only organism actually 
living within the sponge, the remainder were 
simply attached to the surface. The larger 
animals, such as the crabs, were usually found 
hiding among the convolutions and contortions 
of the sponge. 
One clump of S. lata was found in an un- 
protected rocky coast situation at Yaquina Head, 
Oregon. It harbored only a few more organisms 
than the Hood Canal samples. The organisms 
found on the Yaquina Head sample were those 
of the local community. 
Microciona pro lifer a 
Microciona prolifera was found attached to 
subtidal rocks in Willapa Bay, Washington. This 
sponge was erect, branching, and bushy, some- 
times forming a mass of branches 1 foot or more 
in diameter and 6 or 7 inches high. 
M. prolifera provided a place to live for many 
animals and plants; the population density 
varied from 0.27 to 3.64 (mean 0.80) orga- 
nisms per cm 3 of sponge. The organisms most 
commonly found were the gammarid Corophium 
acherusicum, various caprellids, the polynoid 
Harmothoe imbricata, the sabellid Sabella 
media, and the anemone Diadumene luciae. The 
15 samples of sponge dissected harbored 9,581 
organisms of at least 52 species from 9 phyla. 
The most common and abundant of this array 
were the amphipods Corophium acherusicum 
and various caprellids. 
The majority of the inhabitants were found 
attached to the surface of the sponge and rela- 
tively few were found within the sponge tissue. 
Some of the amphipods, sabellids, nereids, and 
nematodes occurred within the sponge. It was 
apparently difficult for the associates to pene- 
trate into the tough and fibrous M. prolifera. 
Due to the branching and bushy morphology 
of the sponge, mud often collected on it and 
this mud harbored many of the associates 
that were found. Therefore, there is a question 
whether the associates were attracted to the 
TABLE 1 
Average Thickness, Volume, Total Associates, and Density of Population for 
Samples of Suberites lata , Microciona prolifera, and Halichondria panicea 
SPECIES 
OF SPONGE 
NO. OF 
SAMPLES 
AVERAGE 
THICKNESS 
(CM) 
AVERAGE 
VOLUME 
(CM 3 ) 
AVERAGE 
total 
ASSOCIATES 
AVERAGE 
DENSITY 
Suberites 
lata 
14 
45(3-7) 
503(195-820) 
10(1-59) 
0.2(0.001-0.8) 
Microciona 
prolifera 
15 
5(2-13) 
594(24-2,340) 
640(21-1,885) 
1.2(0.27-3.64) 
Halichondria 
panicea 
33 
1 (0.5-3) 
104(20-540) 
188(18-670) 
1.8(0.126-19.14) 
