Allison Louise Stockman, Zoology
During the seven weeks which I spent researching at Hopkins Marine Station in Monterey, California, my focus was to delve into the many aspects of Poriferan biology. I am curious as to how sponges function and to what does the Phylum owe its long success in occupying such a specialized niche in the ecosystem. The core of my project was to discover and chart zonation patterns of the various species of Porifera along designated shores along the Monterey Peninsula, and then use this information to integrate sponges into preestablished zonation patterns of the marine environment. Through my efforts I am attempting to develop a unique record of an important and inadequately known section of the marine intertidal community.
My data collection techniques consisted of gathering species from four different coastal sites-recording the characteristics of each sample site as well as the specimens of sponges gathered. For each specimen gathered, a record of depth, appearance, location, oscule size, color and zone (in 6 inch increments with a reference point at the 0 tide level) was taken. To avoid direct contact between each specimen, a detail necessary for accurate identification, each sample was cut with a clean knife and put in a separate vial. The samples were then taken back to a laboratory where I used taxonomic keys, mainly E.F. Light’s A Taxonomic Guide For Invertebrates, to identify each sample.
Since the skeleton, or spicules of each sponge species are unique yet variable, these hard calcareous or siliceous spicules are the basis on which Poriferan taxonomy lies. The epidermis, mesodermis and basement membrane of each individual often contain different types of spicules so I took pieces of each section to examine. I then bleached the sponge samples-which dissolves the mesenchymal tissue and leaves only the spicules which can then be mounted on slides and examined. Once I identified the samples, the patterns of zonation could then be correlated with each species. I also collected additional information on the type of exposed shores, characterization of the substratum, distribution for each species on the substratum, and organisms existing in association with the sponges.
In the five different sites which I collected from, sponges are most prevalent, with a larger biomass, on rocky substratums with irregular outcrops and crevices-rather than small boulder beaches or sand/mud substratums. In the Great Tide Pool, a small boulder beach, only two specimens were found, both of the same species Ophlitospongia penatta. No specimens were found on the mud/ sand beach site. The reason for the Poriferans’ existence in this habitat is foremost for attachment purposes-easier attachment to rocks rather than smooth sand/mud. The rocks also provide specific distribution sites important for specific light, exposure, and submersion vs. emersion needs.
Distribution of each sponge species on the rocks overwhelmingly favored the undersides of rocks, crevices, or in caves. Caves contained the most numerous individuals as well as the greatest diversity of species. Few if any specimens were found on the topsides of rocks or on exposed surfaces. I concluded the reason for this distribution pattern is that the delicate nature of sponges requires a protected, unexposed habitat to avoid smashing and injury by loose rocks or agitating seaweed and wave action. The dark environment of the caves helps the sponges avoid not only ambient temperature damage but also desiccation dangers. I am also investigating the possibility of a correlation between sponge distribution on the substratum to protect from predators.
Organisms associating with the Poriferans included Rostanga pulchra, the red sea slug. I found the eggs of Rostanga on sponges with red or orange color, especially Ophlitospongia penatta, Plocamia karykina, and Axocieletia originalis. The slug uses the toxic taste of the sponge and its red camouflaging color to protect its eggs from predators. Rostanga feeds on sponges, and although it has been seen in association with red and orange colored sponges, it is not known exactly which species Rostanga feeds on. I also found that certain tunicates are space competitors with sponges and I am investigating the possibility that sponges may secrete a biochemical which combats encroachment from certain tunicates.
I have yet to establish a definite pattern of zonation for the Phylum Porifera, although several consistent characteristic are evident. Sponges exhibiting a red color, such as Axocielita originalis, Plocamissa igzo, and A earn us erithacus occupy the widest span of zonation, with a low of -48 inches in the intertidal and 50 feet deep in the subtidal region to +36 inches and 10 feet deep respectively. One possibility is that these red sponges are generally thin, 1/16-1/8 inch thick, and they have a very smooth, tight, glossy surface. This could have something to do with their ability to retain water and resist desiccation in the upper intertidal regions which have greater emersion times. Larger individuals of all species occupying an area of six square inches or more occupied lower intertidal areas from -2 feet to -3 feet and also deep subtidal areas or 50 feet and deeper. I am currently looking at the possibility of space competition as related to zonation for this phenomenon. As of yet, I still have hundreds of samples yet to be identified. Identification for a single species can take up to 7 hours of straight microscopic taxonomy. Further identification will enhance my results and invariable pose more questions.
My research is far from completed in Poriferan zonation hut fascinating questions await answers. My direction of focus with this project will be involved with space competitors as related to zonation and the physiological aspects of certain species’ resistance to desiccation in relation to zonation.