Pugetia morphology

Morphology

The morphology of an alga does more than just differentiate it from its neighbors. It becomes highly specialized, allowing each algal species to thrive within its unique set of abiotic and biotic factors. In their book, Seaweed Ecology and Physiology, Lobban and Harrison discuss the functional-form model advanced by Littler and Littler in 1980. The model links the functional needs of algae, such as photosynthesis, nutrient uptake, and herbivory survival to the physical form of the weed. Thus, according to the functional-form model, morphology is highly specialized to balance each species unique environmental requirements.

Before the specific function of Pugetia’s morphology can be understood in the context of its habitat, it is important to first be familiar with Pugetia’s basic construction. Although Pugetia firma and Pugetia fragilissima have a few structural differences, the morphology and basic cellular functions of these two species are extraordinarily similar and thus can be generalized together. For the specific differences in morphology and cellular structure refer to fragilissima vs. firma.

Pugetia has an isomorphic life history, meaning that through all stages of its life cycle it has the same basis morphology. Its thallus is erect and almost entirely blade-like with virtually no stipe, just a small holdfast either centered in the middle of the blade or at the bottom. The blades are non-calcified, but instead are cartilaginous and delicate (Murray and Dixon, 1972). Pugetia firma tends to have a slightly thicker thallus, whereas Pugetia fragilissima is a bit finer. Pugetia has a thin, pigmented cortex and a thicker multiaxial m edulla with unpigmented isodiametric cells and small filaments. The cells within cortical tissue appear to lack organization, however they are arranged into filaments. Reproductive structures develop in the cortical layer across the entire blade. To learn about the female reproductive anatomy in Pugetia fragilissima and Pugetia firma and its taxonomical significance click here.

Now that a basic description of Pugetia’s morphology and tissue structure has been described, it is possible to explore these features in relation to Pugetia’s unique environmental circumstances in Monterey Bay.

Photosynthesis

Pugetia’s morphology and growth pattern are essential to ensuring adequate light absorption for photosynthesis. In 1986, M.E. Hay classified six generalized thallus morphologies, which absorb light differently (Lobban and Harrison, 1997).

Pugetia seems to share some characteristics with two of the thallus morphologies Hay described. The first is a monolayered flat opaque thallus, which allows a weed to expose its entire photosynthetic area to light. When under the canopy of the kelp or on the shaded vertical faces of rocks, Pugetia takes on a similar morphology, extending out as if to reach for light. The second is a multilayered thallus with translucent blades, which Hays hypothesized, increases the ratio between thallus area and substrate area and would provided an advantage in well-lit areas (Lobban and Harrison, 1997). Translucent blades decrease self-shading when blades overlap. In this way much more photosynthetic surface area can be exposed. Pugetia fragilissima often utilizes this morphology, having overlapping but translucent blades at the top of a tubeworm.

Like most red algae, Pugetia has a series of photosynthetic pigments within its cells, including chlorophyll a (and d?), carotenoids and phycobiliprotiens, which give it its beautiful red coloration. The sun’s light travels at different wavelengths. In general photosynthetic active radiation is considered to be wavelengths of 350-700nm. Using a spectrophotometer to measure Pugetia absorption pattern, it appears that Pugetia’s peak absorption is at a wavelength of 500nm.

Nutrient Uptake
Unfortunately, nothing is specifically known about Pugetia’s ability to uptake nutrients. Considering the nutrient rich waters where it grows, it is unlikely this is a limiting factor, however, Lobban and Harrison warn against the tendency to generalize the nutritional requirements of algae. The quantities Pugetia requires may not be established, but some of the basic nutrients for metabolic processes are certain to be utilized. These include Cu, Mn, Zn, C, H, O, P, K, N, S, Ca, Fe, and Mg. Many other nutrients are also needed in some specialized algae or can be replaced by another element. More work needs to be done on Pugetia’s nutritional requirements before we know if it has any such special needs.

In general, a large unbranched thallus and multicellularity reduce the surface area to volume ratio, thus reducing photosynthesis and nutrient uptake. The degree of multicellularity (thickness) of Pugetia is probably not great enough to make any substantial change in its nutrient uptaking abilities. However, its pseudoparenchymatous medulla reduces cytoplasmic contact between the cells of neighboring filaments. It is believed that the secondary pit connections found in most red algae solve this problem by creating another pathway for nutrient exchange (Lobban and Harrison, 1997).

Grazer Susceptibility
Pugetia’s morphology leaves it relatively susceptible to herbivory. It is not calcified, nor does it grow as a crust. Pugetia has sacrificed these lines of defense for fast growth, and large blades for photosynthesis. To minimize its fitness loss due to herbivory, Pugetia grows quickly, replacing lost tissue, and has scattered reproductive structures along the entire thallus. In this way, Pugetia never looses its entire reproductive hub to one hungry herbivore. Additionally, Pugetia may avoid some herbivores by growing on tubeworms out on the sand flats. For more on information on this theory go to tubeworms.

Space Constraints
Pugetia grows erect for its entire life cycle, allowing it to attach to small areas of substrate, while still expanding its photosynthetic tissue. With its small holdfast, Pugetia fragilissima can even grow on the tips of tubeworms. Pugetia’s cup-like morphology may give it even another competitive advantage in the battle for open substrate. Some algae with flat wide growth patterns, such as the form taken by Pugetia on rocks, may actually block spores from other algae before they reach the substrate (Lobban and Harrison, 1997). In this way Pugetia may guard the substrate around its own holdfast, providing a possible explanation for why Pugetia firma, when present, tends to cover the entire rock face, excluding other species.

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		Marine Botany
MARINE BOTANY Monterey Bay Flora Seagrasses Green algae Red algae Brown algae Phytoplankton Lichens Methods Habitats Bibliography Glossary Syllabus Students PHYCOLOGICAL SOCIETY OF AMERICA	Pugetia fragilissima & Pugetia firma Morphology The morphology of an alga does more than just differentiate it from its neighbors. It becomes highly specialized, allowing each algal species to thrive within its unique set of abiotic and biotic factors. In their book, Seaweed Ecology and Physiology, Lobban and Harrison discuss the functional-form model advanced by Littler and Littler in 1980. The model links the functional needs of algae, such as photosynthesis, nutrient uptake, and herbivory survival to the physical form of the weed. Thus, according to the functional-form model, morphology is highly specialized to balance each species unique environmental requirements. Before the specific function of Pugetia’s morphology can be understood in the context of its habitat, it is important to first be familiar with Pugetia’s basic construction. Although Pugetia firma and Pugetia fragilissima have a few structural differences, the morphology and basic cellular functions of these two species are extraordinarily similar and thus can be generalized together. For the specific differences in morphology and cellular structure refer to fragilissima vs. firma. Pugetia has an isomorphic life history, meaning that through all stages of its life cycle it has the same basis morphology. Its thallus is erect and almost entirely blade-like with virtually no stipe, just a small holdfast either centered in the middle of the blade or at the bottom. The blades are non-calcified, but instead are cartilaginous and delicate (Murray and Dixon, 1972). Pugetia firma tends to have a slightly thicker thallus, whereas Pugetia fragilissima is a bit finer. Pugetia has a thin, pigmented cortex and a thicker multiaxial m edulla with unpigmented isodiametric cells and small filaments. The cells within cortical tissue appear to lack organization, however they are arranged into filaments. Reproductive structures develop in the cortical layer across the entire blade. To learn about the female reproductive anatomy in Pugetia fragilissima and Pugetia firma and its taxonomical significance click here. Now that a basic description of Pugetia’s morphology and tissue structure has been described, it is possible to explore these features in relation to Pugetia’s unique environmental circumstances in Monterey Bay. Photosynthesis Pugetia’s morphology and growth pattern are essential to ensuring adequate light absorption for photosynthesis. In 1986, M.E. Hay classified six generalized thallus morphologies, which absorb light differently (Lobban and Harrison, 1997). Pugetia seems to share some characteristics with two of the thallus morphologies Hay described. The first is a monolayered flat opaque thallus, which allows a weed to expose its entire photosynthetic area to light. When under the canopy of the kelp or on the shaded vertical faces of rocks, Pugetia takes on a similar morphology, extending out as if to reach for light. The second is a multilayered thallus with translucent blades, which Hays hypothesized, increases the ratio between thallus area and substrate area and would provided an advantage in well-lit areas (Lobban and Harrison, 1997). Translucent blades decrease self-shading when blades overlap. In this way much more photosynthetic surface area can be exposed. Pugetia fragilissima often utilizes this morphology, having overlapping but translucent blades at the top of a tubeworm. Like most red algae, Pugetia has a series of photosynthetic pigments within its cells, including chlorophyll a (and d?), carotenoids and phycobiliprotiens, which give it its beautiful red coloration. The sun’s light travels at different wavelengths. In general photosynthetic active radiation is considered to be wavelengths of 350-700nm. Using a spectrophotometer to measure Pugetia absorption pattern, it appears that Pugetia’s peak absorption is at a wavelength of 500nm. Nutrient Uptake Unfortunately, nothing is specifically known about Pugetia’s ability to uptake nutrients. Considering the nutrient rich waters where it grows, it is unlikely this is a limiting factor, however, Lobban and Harrison warn against the tendency to generalize the nutritional requirements of algae. The quantities Pugetia requires may not be established, but some of the basic nutrients for metabolic processes are certain to be utilized. These include Cu, Mn, Zn, C, H, O, P, K, N, S, Ca, Fe, and Mg. Many other nutrients are also needed in some specialized algae or can be replaced by another element. More work needs to be done on Pugetia’s nutritional requirements before we know if it has any such special needs. In general, a large unbranched thallus and multicellularity reduce the surface area to volume ratio, thus reducing photosynthesis and nutrient uptake. The degree of multicellularity (thickness) of Pugetia is probably not great enough to make any substantial change in its nutrient uptaking abilities. However, its pseudoparenchymatous medulla reduces cytoplasmic contact between the cells of neighboring filaments. It is believed that the secondary pit connections found in most red algae solve this problem by creating another pathway for nutrient exchange (Lobban and Harrison, 1997). Grazer Susceptibility Pugetia’s morphology leaves it relatively susceptible to herbivory. It is not calcified, nor does it grow as a crust. Pugetia has sacrificed these lines of defense for fast growth, and large blades for photosynthesis. To minimize its fitness loss due to herbivory, Pugetia grows quickly, replacing lost tissue, and has scattered reproductive structures along the entire thallus. In this way, Pugetia never looses its entire reproductive hub to one hungry herbivore. Additionally, Pugetia may avoid some herbivores by growing on tubeworms out on the sand flats. For more on information on this theory go to tubeworms. Space Constraints Pugetia grows erect for its entire life cycle, allowing it to attach to small areas of substrate, while still expanding its photosynthetic tissue. With its small holdfast, Pugetia fragilissima can even grow on the tips of tubeworms. Pugetia’s cup-like morphology may give it even another competitive advantage in the battle for open substrate. Some algae with flat wide growth patterns, such as the form taken by Pugetia on rocks, may actually block spores from other algae before they reach the substrate (Lobban and Harrison, 1997). In this way Pugetia may guard the substrate around its own holdfast, providing a possible explanation for why Pugetia firma, when present, tends to cover the entire rock face, excluding other species. Intertidal Stress Intertidal Pugetia firma and subtidal Pugetia firma have slightly different morphologies due to the extra stress within the intertidal. Intertidal Pugetia firma must withstand wave action and exposure to dry air and direct sunlight, thus it has a slightly thicker thallus with large medulla cells. The result is a slightly tougher thallus and a lower surface area to volume ratio reducing the risk of desiccation. Pugetia Home Taxonomy Distribution Habitat Morphology Life Cycle Ecological Interactions Glossary References and Acknowledgments © 2005 Laure Sierra Katz. You are welcome to use any of my images. If you have any questions, comments or happy ocean stories please email me at laurek@stanford.edu Marine Flora Habitats Glossary Syllabus Students Last updated: Oct. 21, 2005
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Pugetia fragilissima & Pugetia firma

Morphology