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ANTARCTICA

MARINE BOTANY

Codium setchellii

Cellular Structure

Codium setchellii is unusual in that it is comprised of a single cell. The siphonous construction of the alga means it is an elongate cell with no cell wall divisions that is coiled around itself. This construction is rather obvious under the microscope. The elongate internal structures of Codium are known as utricles and are drawn schematically below.

Figure. 1: Schematic drawing of C. setchellii utricles (note rounded apex)
(After Scagel 1967)

The utricles of C. setchellii have a rounded tip. Utricles in this species are heavily branched; the shape is usually cylindrical, but may be narrowly clavate (Abbott and Hollenberg 1976). The utricle may be between 65 and 90 micrometers in diameter and typically 0.65 to 1.0 millimeters long. Utricle walls up to 16 micrometers thick; the walls are lamellate at the apex and lack internal sculpturing.

Figure 2: Lateral view of siphonous utricles of C. setchellii

Figure 3: View down onto surface of utricles of C. setchellii

Comparison with Codium fragile

The cellular structure is similar to the related Codium fragile, but slight differences in the utricle can be used to differentiate these congeners. Utricles in C. fragile have a thorn-like projection which is absent in C. setchellii. The tips of the utricle are smooth in C. setchellii, thus there is a clear morphological difference at the utricle tip.