New species of the diatom genus Fryxelliella (Bacillariophyta), Fryxelliella pacifica sp. nov., from the tropical Mexican Pacific

Abstract

During phytoplankton monitoring of coasts off Salina Cruz, Oaxaca, in the tropical Mexican Pacific, a new species, Fryxelliella pacifica sp. nov., was found and is described in this paper. The species is solitary, with cells of medium size, discoid with three relatively large ocelli on the valve face, located close to the margins (3-5 areolae from the margins) and placed symmetrically. Significantly, it possesses the morphological characters that distinguish the genus Fryxelliella from related genera: the presence of the 'circumferential marginal tube' (siphon marginalis), the external subcircular or subtriangular apertures at the valve margins, and the 'juxtaposed rectangular plates' in the valve mantle. The species that appears to be the most closely related is Fryxelliella floridana Prasad, an extant species and the type of the genus. However Fryxelliella pacifica differs from it (i) the size and shape of the cell; (ii) the size, location and structure of the ocelli (which additionally are not elevated); (iii) the shape and density of the subcircular to subtriangular marginal apertures; (iv) the external morphology of the rimoportulae (short process, two concentric tubes with the outer tube tip as a crown); and (v) it is marine rather than brackish. Externally the rimoportulae have a rather complex structure of two concentric tubes: the exterior tube has a tip divided like a crown. In spite of the fact this species was found in plankton samples, it is considered to inhabit sandy sediments (epipsammic) or as tychoplanktonic.

Nomenclatural priority of the diatom name Fryxelliella sepulvedana over Fryxelliella pacifica (Triceratiaceae, Bacillariophyta)

“…Other characters, such as the structure of cribra, density of the sub-triangular apertures, and continuity of the sipho marginalis were also mentioned (Meave et al 2008). Fryxelliella pacifica was differentiated from F. floridana by the size and shape of the cell, size location and morphology of ocelli, shape and density of the sub-triangular marginal apertures and the external morphology of rimoportulae (Hernández-Becerril & Barón-Campis 2008). These data justified the creation of a new species different from F. floridana but they describe one species not two.…”

Morphology of three marine epizoic diatoms from the Mexican Pacific: Protoraphis hustedtiana, Pseudohimantidium pacificum and Sceptronema orientale (Bacillariophyta)

“…(Hiromi and Takano, 1983;Tiffany, 2011;Totti et al, 2011;Gárate-Lizárraga and Esqueda-Escarcega, 2018). During several oceanographic expeditions carried out along coasts of the Mexican Pacific, the high diversity of planktonic diatoms has been confirmed (Hernández-Becerril et al, 2010, 2013, but additionally epipsammic forms have been also reported, including descriptions of two new species (Hernández-Becerril and Barón-Campis, 2008;Hernández-Becerril et al, 2012).…”