Guide to Gato

This monotypic genus is known from marine waters of Caribbean islands (Puerto Rico, Jamaica), Micronesia (Guam, Palau, Yap, Chuuk, Majuro), and from samples of Sargassum from Honduras (Grunow Collection).

Frustules are heteropolar and rectangular in girdle view. Valves are obovate in shape. Striae are very fine, poroid, and uniseriate on one valve. Striae extend from a narrow, irregular, central sternum to the valve margin. Valves within a frustule have differing rimoportulae, so they are considered heterovalvar. One valve of the frustule has a large rimoportula at the basal pole; both valves possess a smaller rimoportulae at the apex. A row of rimmed pores is present on the valve margin around both basal poles. One or two additional rimmed pores are present on each side, further from the base. The valve with the basal rimoportula has oblique, biseriate striae.

Gato is, so far, monotypic and the only known araphid diatom to form and inhabit mucilage tubes. Colonies are small, branching, and segmented with one cell in each segment (two if recently divided). Plastids are elongate and numerous. Striae are not discernable in LM. The rimoportulae are visible in LM, in what otherwise appears to be just girdle bands so they are easily overlooked.

The systematic position of the genus is unknown. The heterovalvar rimoportula arrangement in heteropolar valves is reminiscent of Licmophora C.A.Agardh, but the rimmed basal pores bear no resemblance to the multiscissura of Licmophora and the copulae differ. The production of mucilage tubes and rimmed pores set the genus apart from other araphids. There are presently no genetic data for Gato. Valves bear some resemblance to Florella J.N.Navarro in the irregular narrow sternum and lack of apical pore fields, but cells of both species of Florella are cylindrical with many deep girdle bands,  free-living chains, valves broadly oval and isopolar, small rimoportulae, striae visible in LM, and no large rimmed pores.