Diversity and Distribution of Freshwater Porifera in Wisconsin

by Victoria Bertolami
BIOL/WATER 361, Fall 2012

Key taxa: Porifera, Demospongiae, Spongillidae

Freshwater Porifera (sponges) are filter-feeding masses composed of live and dead material. Sponges benefit their ecosystem in several ways, such as providing habitat for smaller organisms. Wisconsin is of particular importance to the study of freshwater Porifera because of its many streams, ponds, and lakes (Jewell, 1935). Discussing sponge species of Wisconsin focuses our attention on a manageable 13 of 219 freshwater sponge species (Annesley et al., 2008). The physical and chemical characteristics of the streams, ponds, and lakes have varying effects on the distribution and morphology of sponge species in Wisconsin. It is possible that these relationships also apply to the greater Porifera phylum.

Wisconsin was particularly suited for investigating the distribution of freshwater sponges in the early to mid 1900’s. This is because, when investigating the distribution of Spongillidae species, a variety of correlations between species present and physical/chemical properties of the lake need to be tested. Wisconsin’s larger lakes and many of its small lakes had full chemical profiles at this time thanks to the work of previous limnologists (Jewell, 1935). For this reason, there is a history of Spongillidae research in Wisconsin to review.

Narrowing our focus on Wisconsin allows us to take a more personal look at a very broad, world-wide phylum of invertebrates. Any correlations between species present and habitat conditions presented in this essay are only true of Wisconsin species, but it is likely that similar relationships are reflected in the distribution of sponges in other states or regions. Wisconsin is therefore our venue for basic knowledge of diversity and distribution relationships of freshwater sponges.

Diversity of the phylum Porifera (both marine and freshwater) is currently estimated to be about 15,000 species. Of that, all freshwater species belong to one of six families within class Demospongiae (Manconi and Pronzato, 2008). All species present in the United States are from family Spongillidae. The Spongillidae family consists of 145 species total, 30 of which appear in the United States (Manconi and Pronzato, 2008). Of those thirty which appear in the United States, the following 13 species appear in Wisconsin: Anheteromeyenia argyrosperma, Anheteromeyenia ryderi, Corvospongilla everetti, Duosclera mackayi, Ephydatia fluviatilis, Ephydatia muelleri, Eunapius fragilis, Heteromeyenia baileyi, Heteromeyenia tentasperma, Heteromeyenia tubisperma, Radiospongilla crateriformis, Spongilla lacustris, and Trochospongilla pennsylvanica (Annesley et al., 2008). These species can be described in terms of their optimum habitat. Habitat and species relationships discussed qualify this essay as an investigation into Porifera diversity and distribution in Wisconsin.

Why study distributions and diversity between species in the first place? Even now, it may be said that freshwater sponges only live in pristine water bodies. Not often would someone generalize that all birds are found in clean air; thus the generalization that all sponges live in clean water bodies would also be false (Jewell, 1935). There is much more to be distinguished about sponge habitats other than that they are clean. Over half of known freshwater sponges are endemic to a particular lake (Manconi and Pronzato, 2008). Because of the level of endemicity among freshwater sponges, it can be concluded that the presence of freshwater sponge species is dependent on the water body location and the water’s physical and chemical properties. Optimum habitats differ depending on the species of Porifera being discussed. With a better understanding of these habitats and species distributions there will be a better understanding of Porifera species effects on the ecosystem.

Sponge habitat diversity ranges from caves, to water tanks, to estuaries, and even thermal vents (Manconi and Pronzato, 2008). In Wisconsin, sponges have historically been researched in lakes and streams. Within highly variable lake habitats, freshwater sponges are able to tolerate normally devastating fluctuations in climate, oxygen availability, and pollution via a resting stage. These resting stages are called gemmules (Manconi and Pronzato, 2008). It is this type of evolutionary survival technique which allows for sponges to survive the highly variable conditions of freshwater lakes in Wisconsin. Determining the difference between species is often reliant on gemmule morphology. It is possible that there are relationships to be drawn between the diversity of habitats (their physical and chemical characteristics) and gemmule morphology. An understanding of these relationships could provide reasons as to why Porifera species are distributed the way that they are.

Parameters of diversity (morphology, chemical, and physical characteristics of the water) vary in their importance to a given sponge species. This type of information brings about the point that not every parameter measured is a qualifying variable for the presence or absence of sponge species. Every species’ physical and chemical relationship to its environment is going to be unique and not every variable will be a defining factor for every species.

Transparency would be an example of a parameter which has influence on only some species. Transparency varies between water bodies and within water bodies as microhabitats. In a sense, presence of sponge species in areas of low transparency is like saying the sponge is shade tolerant. Only the species Corvospongilla everetti and Spongilla lacustris sponge species were found to be shade intolerant (Jewell, 1935). This is simply an example of the species present, given a physical characteristic of the water.

Motion would be an example of a parameter which influences the presence and absence of most Porifera species. This is similar to saying that freshwater sponges exist in lotic and lentic environments. Ephydatia muelleri, Anheteromeyenia argyrosperma, and Heteromeyenia tubisperma favor slow moving streams or a constant weak current. Spongilla lacustris and Trochospongilla pennsylvanica need standing water or lake conditions for good health (Jewell, 1935). This is a more intuitive description of habitat (stream or lake), and it is an important example of how a physical characteristic of the water, effects species presence. Again, this is simply an example of the species present when given a physical characteristic of the water. It is a look at a simple relationship which affects the presence of most sponge species.

Morphology can also be used in predicting the distribution of freshwater sponge species. The gemmule resting stage varies in form between species, possibly as a unique response or development to that particular environment. Species such as Spongilla aspinosa, a North American freshwater sponge, are notorious for their scarce gemmules. While typically used as a defining feature, when none are found it is difficult to assume that the species is not present. The species record in Wisconsin once listed S. aspinosa, but has since been found invalid. Though this is the current ruling on Spongilla aspinosa, their true range extent is difficult to define because they lack abundant gemmules (Annesley et al., 2008). Lack of gemmules defines the species, but it may also explain why they are not present in Wisconsin. It could be that Wisconsin’s fluctuating climate requires a sponge to have abundant gemmules for survival. In this example, we see that even a lack of morphological structures can be used to assume relationships between the species and its distribution.

Relationships between the species morphology and their preferred or optimum habitat can be theorized using another example. The Wisconsin species Spongilla lacustris is known for its gemmule’s varying wall thickness, and lack of gemmoscleres (Annesley et al., 2008). The species is known to have a typical and an atypical form (Frost et al., 1982). The typical form’s optimum environment can be described by its varying calcium content (Jewell, 1939). S. lacustris (typical) is also found most often with Heteromeyenia spp. and Ephydatia muelleri (Jewell, 1935). It could then be that the typical thin walled form is associated with an environment of varying calcium content because they do not rely on a lot of calcium for wall structure. This is only an assumption, and it is an example of how conclusions can be drawn from combining data on sponge species. Distribution of the Wisconsin species can be further scrutinized for relationships across many variables.

Habitat correlations and species morphology can be examined in the Wisconsin species Trochospongilla pennsylvanica as well. T. pennsylvanica is known for a gemmule with many megascleres on the entire surface (Annesley et al., 2008). The megascleres are like needles lying across the gemmules surface. T. pennsylvanica prefers environments with low calcium concentrations but is capable of survival within a specific range. When it is located in waters at the upper range of calcium concentrations, the sponges are most often found in the muck and areas of rapid decomposition (Jewell, 1935). Though it can survive in high calcium concentrations, with enough organic matter, its preference for low calcium concentration is somewhat puzzling. A gemmule surface with many needles requires structure. Before, we said that for a thin-walled gemmule, the sponge is likely to be found in water of low or varying calcium concentration. T. pennsylvanica contradicts this previous assumption. This example demonstrates that assumptions do not always carry between species proves that the relationships between sponge species distribution and water characteristics are not always simple.

In Minna Jewell’s (1935) study of Wisconsin, sponge species were found in over 80 percent of the streams and lakes. There is no doubt that freshwater sponges are of interest to the study of species diversity. This essay was meant to introduce readers to the breadth of diversity in morphology and preference for physical and chemical water characteristics among sponges. Attempting to identify relationships within these parameters is an attempt at defining the distribution of various sponge species in Wisconsin. These small scale, yet complex, relationships in Wisconsin species shed light on the magnitude of relationships possible among species of the greater Porifera phylum.

Porifera are important members of an ecosystem for their filter feeding and organic matter removal as well as for their provision of habitat (Manconi and Pronzato, 2008). Sponges therefore contribute to the diversity and quality of a water body in several ways. Understanding the sponge/environment relationship can help us to better grasp their impact on water bodies. In Wisconsin, lakes and rivers have a history of appreciation. This provided a good base for investigation into the chemical and physical parameters of the water and their effect on sponge distribution and species present. Wisconsin sponges range in calcium tolerance, shade tolerance, and current tolerance. These qualities, and more, are what determine if a certain sponge species is present. They may be in upwards of 80% of water bodies in Wisconsin, but their presence is still a function of habitat parameters and relationships which have yet to be fully defined.

References Cited

• Annesley, J., J. Jassa, and D. Watermolen. 2008. Wisconsin freshwater sponge species documented by scanning electron microscopy. Journal of Freshwater Ecology 23:263-272.
• Frost, T. M., G. S. DeNagy, and J. J. Gilbert. 1982. Population dynamics and standing biomass of the freshwater sponge Spongilla lacustris. Ecology 63:1203-1210.
• Jewell, M. E. 1935. An ecological study of fresh-water sponges of northeastern Wisconsin. Ecological Monographs 5:461-504.
• Jewell, M. E. 1939. An ecological study of fresh-water sponges of Wisconsin, II. The influence of calcium. Ecology 20:11-28.
• Manconi, R. and R. Pronzato. 2008. Global diversity of sponges (Porifera: Spongillina) in freshwater. Hydrobiologia 595:27-33.