The marine araphid diatom genus Licmosphenia in comparison with Licmophora, with the description of three new species

Abstract

Licmosphenia Mereschkowsky is distinguished from Licmophora C.A. Agardh on the basis of a septum with an apical aperture. Nine species have been named; hardly any have been reported since they were first described. Three species that clearly fit Mereschkowsky's generic definition have been found in samples from filamentous seaweeds in Guam and observed with light and scanning electron microscopy. Two are very similar to Mereschkowsky's Licmosphenia peragalli and Licmosphenia vanheurckii, but different enough to be proposed as new species, Licmosphenia peragallioides sp. nov. and Licmosphenia albertmannii sp. nov., along with Licmosphenia leuduger-fortmorelii sp. nov. Valves of these species are structurally similar to one another and to Licmophora aff. ehrenbergii (Kützing) Grunow and Licmophora abbreviata C.A. Agardh. All have wide striae of apically elongated areolae, and all have three rimoportulae per frustule: on the head pole of each valve but on the foot pole of only one. They differ in the shape of the valve and septum and can be distinguished on the basis of septum structure alone. A summary is provided of all other named Licmosphenia species, including a key for their identification. Comparison with Licmophora shows that the fine structure of the three new species is similar to species with coarse striae, e.g., Licmophora ehrenbergii and Licmophora abbreviata, but other species in both genera have finer striae, which in Licmophora are known to have different ultrastructure. At present there is insufficient evidence to emend the generic description of Licmosphenia or to decide if it should be included in Licmophora.

Keywords:

• biodiversity
• coral reefs
• diatoms
• Guam
• Licmophoraceae
• Licmophora ehrenbergii
• Licmosphenia albertmannii
• Licmosphenia peragallioides
• Licmosphenia leuduger-fortmorelii
• Podocystis

Acknowledgements

I acknowledge NIGMS RISE funding for LM and SEM instruments on Guam and COMNAVMAR for access to study sites on Naval Facility Guam. Thanks to Matt Ashworth (University of Texas, Austin) for Figure 68 and Supplementary Table 1, Rick L. Castro (University of Guam) for Figure 32, Friedel Hinz (Alfred-Wegener-Institut für Polar- und Meeresforschung) for photos of Licmosphenia taylori, and, as always, my wife María Schefter for encouragement and support in the field work.

Notes

According to Russian diatomist V. Stepanova (pers. comm., June 2012), also one may note the absence of Mereschkowsky's name from the list of collectors/investigators in the compilation of diatom collections by Fryxell (1975).