Marine Botany

Pugetia versus Callophyllis

Where does firma belong?


In 1941, Kylin described and named a new alga species, Pugetia firma. Kylin assigned the new species to the genus Pugetia due to its remarkably similar morphology and basic cell structure to Pugetia fragilissima, which he had described in 1925. Like P. fragilissima, P. firma has an undivided blade-like thallis and a medulla with large isodiametric cells divided by chains of smaller well-developed filaments.

In 1957, R. Norris moved two Pugetia species, P. firma and P. chilensis from the genus Pugetia to the genus Callophyllis, making them Callophyllis firma and Callophyllis chilensis. Although these species do not share the regularly dichotomously branched thalli of other Callophyllis species, their female reproductive structure was much more akin to Callophyllis than to Pugetia fragilissima, the archetype for Pugetia. Norris placed reproductive structure as the primary taxonomic characteristic.

According to Norris, Pugetia fragilissima has a relatively primative female reproductive structure, within the family Kallymeniaceae. It is nonprocarpial, meaning that the carpogonia do not have a close spatial association with auxiliary cells. Instead, many three-celled carpogonial branches are rooted to one supporting cell, which may in turn be attached to another supporting cell through a connecting filament and fusion cell. In this way the second supporting cell may act as an auxiliary cell for its neigbors carposporophytes. Its own carpogonial branches are nonfunctional. Pugetia firma and most Callophyllis species have a slightly different female reproductive system than Pugetia fragilissima. They are procarpial with one cell acting both as a supporting cell and as an auxiliary cell with no connecting filaments. Each supporting cell can bear one to many carpogonial branches. Since Pugetia firma has similar reproductive anatomy to Callophyllis, it was considered to be part of that genus for approximetly 50 years. Only recently has Pugetia firma's true taxonomic relationships been deciphered.

A study published in 2002 conducted by James Harper and Gary Saunders used molecular data to finally resolve the gentic relationships between Callophyllis, Pugetia and other genera within the family Kallymeniaceae. They demonstrated that female reproductive anatomy was not the most important trait for taxonomic classification and that Callophyllis firma and Callophyllis chilensis were actually genetically much more similar to Pugetia fragilissima then the other species within the genus Callophyllis. The study confirmed Kylin's initial classification and these two species and they have subsequently been returned to the genus Pugetia.

© 2005 Laure Sierra Katz.
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Last updated: Oct. 21, 2005