Monterey Bay Aquarium Research Institute
Marine Botany

Codium setchellii

Structure and Morphology


Codium setchellii has a rather unusual body form for a green alga. Unlike most familiar green algae, C. setchellii is a crustose species, forming a thick mat on rocks in the low intertidal zone. This green crust comes in a variety of shades; most often the crust is brilliant green, but in some areas of Monterey Bay the crust is dark green, almost black in color. Crustose C. setchellii usually forms individual round clusters on the substrate. These amorphous "blobs" in the intertidal are often velvety in texture, varying from deep, dark green to lighter shades of green in some individuals. The "cushion" of the alga can reach a diameter of 25 centimeters, though individual algae may coalesce into larger crusts over the substrate (Abbott and Hollenberg 1976). The thallus of C. setchellii crusts is typically 6 to 15 millimeters thick, forming a tight association with the substrate to which it is attached (Abbott and Hollenberg 1976).

Figure 1: Codium setchellii occurring as a solitary round colony in the low intertidal (Point Pinos, Pacific Grove, CA, USA)

An unusual morphology appeared in individuals observed and collected from Carmel (CA). Here, C. setchellii completely encrusted some rocks. This unusual form had a velvet texture and formed thick and thin mats over the rock. In some areas, the crust actually formed projections off the main form; the function of these projections remains unknown, but may be related to increasing surface area of nutrient uptake and gas exchange.

Figure 2: Unusual crust formation by C. setchellii observed at Carmel Beach (Carmel, CA, USA) dominates the low intertidal

Forms Similar to Codium setchellii

Various other organisms that live in the intertidal zone closely resemble Codium setchellii. Some algae are similar in appearance to C. setchellii from a distance, but only when examined up-close do the differences become obvious.

In some areas of Monterey Bay, the filamentous green alga Cladophora columbiana often looks like C. setchellii. Both species are green and have a similar globular appearance when wet. However, the texture of Cladophora is clearly comprised of large filaments which can be teased apart, a feature not seen in C. setchellii.

Figure 3: Tufts of the filamentous alga Cladophora columbiana in the intertidal zone may resemble C. setchellii from a distance

The "Petrocelis" form (tetrasporophyte) of Mastocarpus papillatus superficially resembles C. setchellii. Both form crusts in the intertidal zone, but the crust of Mastocarpus is dark brown in color and is much thinner than C. setchellii crusts.

Figure 4: The black crust of the tetrasporophyte of Mastocarpus papillatus (sometimes called the "Petrocelis" morph)

Choose one of the following links to learn more about Codium setchellii:

|Taxonomy | Distribution | Habitat | Structure & Morphology | Cellular Structure |

| Reproduction & Life Cycle | Ecology | Epiphytes | References |

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© 2005 Raúl Nava.
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Last updated: Feb. 05, 2009