Abstract
BackgroundDiatoms in genus Licmophora are found as epiphytes on marine shores and are members of fouling communities. They can be abundant on natural coral reef substrates such as filamentous algae and as fringes on Halimeda. Biodiversity of benthic tropical diatoms is generally poorly known. Several new species of Licmophora have been reported from Guam but many are still undescribed.MethodsSamples of seaweeds with evident diatom coatings were collected during scuba dives, examined live, preserved in formalin, and processed with nitric acid cleaning following standard practice. Cleaned samples were examined in LM and SEM.ResultsWe describe two species unusual in having an axial wave in the valve, and a further long, straight species. L. repanda n. sp. and L. undulata n. sp. were of similar lengths (ca. 200 μm long) and both had axial waves but L. undulata was more slender with an inflated basal pole, had colonies on mucilage pads vs. long, single-stranded mucilage stalks. In addition, L. undulata had one apical rimoportula vs. two, elongated areolae along the midrib vs. uniform areolae, and the valvocopular advalvar striae ended halfway along, whereas in L. repanda they continued to the end. L. joymaciae n. sp. grew on long, single-stranded mucilage stalks with valves 300–400 μm long, with two apical rimoportulae, and basal pole not inflated. As in L. undulata its valvocopular advalvar striae ended halfway along the band. Stria densities were different at apex vs. base in L. joymaciae but not in the two wavy species. In all species, the 4th pleura had an apical cap and a narrow band with a single row of pores but it was larger in L. joymaciae. The other three girdle bands did not present any major differences among the three species but are documented for future comparisons with other species.ConclusionsAlthough the morphometric differences are small among the new species and between them and similar known species, the combinations of character states clearly shows that they are different.
Highlights
Diatoms of the genus Licmophora C.A.Agardh are common and sometimes abundant epiphytes on marine shores from the poles to the tropics
Diatoms with wavy outlines, where the valve outline has a wave form are rare
We recently showed that there are many useful characters in the girdle bands (Lobban et al 2018), but this information has yet to be collected for most taxa
Summary
Diatoms of the genus Licmophora C.A.Agardh are common and sometimes abundant epiphytes on marine shores from the poles to the tropics. Diatoms with wavy outlines, where the valve outline has a wave form (as opposed to species where the wavy margins are the result of inflations, such as Grammatophora undulata Ehrenberg) are rare. They include Toxarium undulatum Bailey ex Bailey (Mediophyceae) and Neosynedra tortosa (Grunow) D. Diatoms in genus Licmophora are found as epiphytes on marine shores and are members of fouling communities. They can be abundant on natural coral reef substrates such as filamentous algae and as fringes on Halimeda. Several new species of Licmophora have been reported from Guam but many are still undescribed
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