Spongilla argyrosperma

Taxobox
name = Freshwater sponge (North America)


image_caption =
regnum = Animalia
phylum = Porifera
classis = Demospongiae
ordo = Haplosclerida
subordo = Spongillina
familia = Spongillidae
genus = "Spongilla"
species = "S. argyrosperma"
binomial = "Spongilla argyrosperma"
binomial_authority = (Potts, 1880)
synonyms =
* "Heteromeyenia (Anheteromeyenia) argyrosperma"

"Spongilla argyrosperma" (Potts, 1880) is a freshwater sponge found across North America.

Geographical Range

Nearctic region from Canada (Quebec, New Brunswick) to Florida and northern Alaska to southern California.²

Habitat

"Spongilla" "argyrosperma" is found in both lotic (flowing water) and lentic (still) habitats. Typically in waters of about neutral pH with low to moderate alkalinity and high conductivity; in temperatures of 9 to 23 °C.² They are sessile suspension feeders that attach to submerged surfaces such as rocks and logs in most inland habitats.

Diet

Sponges filter the water through them to collect numerous species of smaller organisms such as bacteria and protozoa. "Spongilla" "argyrosperma" are especially important in nutrient cycling and primary production.⁴

Physical Characteristics (Morphology)

"Spongilla" "argyrosperma" have a thin, encrusting form with a hispid surface due to emerging spicules. Their color is grey unless green from being in symbiosis with zoocholrellae (algae). Their bodies are permeated with pores, chambers, and canals for the flow of water through them. The smaller, more prevalent incurrent pores are the ostia and the larger excurrent pores are the oscula. Within "S." "argyrosperma" the oscules are inconspicuous.²

Cell Structure/Internal Characteristics

Sponges have no true tissues or germ layers. While the cells are loosely organized, different cells are responsible for different functions within the animal but have the ability to transform into different cell types. "Spongilla" are the Leuconoid stage of progression which means their form is of many collected channels and chambers clustered together so water moves throughout the specimen. The tissue is called the mesohyl and the water movement occurs through flagellated cells called choanocytes.³ "S." "argyrosperma" have siliceous spicules and collagen fibers to give it its form. Spicules are needle like structures which form the mineral skeleton. Megascleres are large spicules that form the main skeleton. Within "S." "argyrosperma" the megascleres are slender, slightly curved acanthoxeas that range in length from 250- 329 µm and in width from 10-15 µm. Microscleres are absent.²

Reproduction

"Spongilla" can reproduce sexually or asexually. They can produce live larvae sexually or asexually they may bud or if a section breaks off the cells can reaggragate and grow into new specimens. In times of environmental stress, which is much more often in freshwater sponges, they can reduce their bodies or produce gemmules or “cysts” which form a hard, protective coating over the asexual larvae so they can be moved about and grow when the conditions permit or are more favorable. In "S." "argyrosperma" the gemmules are yellow and spherical with a diameter ranging from 400-700 µm. The gemmuloscleres have birotulates of two notably different lengths. These details of long recurved rays with shaft spines and the shorter more abundant variation along with the length range of gemmuloscleres are some of the most reliable details to observe in identification.⁴ The specimen pictured is lacking gemmules, probably because of being collected in early summer.

Misidentification

May be mistaken for common algae growth on rocks in habitat because of similar green color and flat, encrusting form. May also be living within algae growths or other "Spongilla" colonies symbiotically. There are abundant misidentifications of these and other species because of incomplete, fragmentary keys for freshwater sponges that have incomplete taxonomic and ecological information. Especially important to this range of varieties and synonyms is a lack of information concerning environmental variation, in morphological types within a given species.⁴

Additional Importance

"Spongilla argyrosperma" live very much within a symbiosis state with many forms of algae (what gives it a green color, see above). This zoochlorellae may augment or supplement their sponge host's nutrition. Also, because of being a susceptible and responsive freshwater animal, "Spongilla" species are potentially very valuable indicators of water quality.⁴

Research Resources

*1. Brusca, Richard C., and Brusca, Gary J. Invertebrates. 2nd. Sinauer Associates, Inc. Sunderland, MA 2003.
*2. Hooper, John N.A, and Van Soest, Rob W.N. Systema Porifera: A Guide to the Classification of Sponges, Volume 1. Kluwer Academic/Plenum Publishers, New York, NY 2002.
*3. Nybakken, James. Diversity of the Invertebrates. 1996.
*4. Ricciardi, Anthony, and Reswig, Henry M. “Freshwater Sponges (Porifera, Spongillidae) of Eastern Canada: taxonomy, distribution, and ecology”. Canadian Journal of Zoology, Volume 71, #4 April 1993, 665-682.

Note: All pictures taken by Alie Perez. Megascleres are photographed on a Zeiss at 400x