Gomphonemopsis platypus ( Ostrup ) Lang Li, Yuhang Li & Junxiang Lai, 2024

Li, Lang, Nong, Qun-Zhuan, Chen, Chang-Ping, Li, Yu-Hang & Lai, Jun-Xiang, 2024, Two new diatom species of the genus Gomphonemopsis (Bacillariophyceae) from the coast of China and two new combinations for the genus, PhytoKeys 239, pp. 255-266 : 255

Gomphonemopsis platypus ( Ostrup) Lang Li, Yuhang Li & Junxiang Lai comb. nov.

Gomphonema platypus Østrup 1910. Danske Diatoméer, p. 65, pl. II, fig. 49. Basionym.

Gomphonemopsis exigua var. platypus ( Østrup) Snoeijs in Snoeijs and Balashova 1998, p. 55, fig. 443. Synonyms.

Gomphonema exiguum var. platypus ( Østrup) Lange-Bertalot in Krammer and Lange-Bertalot 1985, p. 47.

PhycoBank registration.

http://phycobank.org/104420.

Dichotomous key to distinguish the Gomphonemopsis species

In order to facilitate the identification of the Gomphonemopsis species, a dichotomous key to all known species is presented as follows:

1	Valves isopolar	2
-	Valves heteropolar	3
2	Apices capitate	G. oahuensis
-	Apices acutely rounded	G. gaoi
3	Valves clavate with widened foot pole	G. platypus
-	Valves linear to lanceolate	4
4	Central area small	G. exigua
-	Central area wide or asymmetrical	5
5	Striae 26-30 in 10 μm	G. nana
-	Striae ≤ 24 in 10 μm	6
6	Areolae round	7
-	Areolae elongate or round near poles	8
7	Mantle areolae only extending along the wider part of valve	G. ligowskii
-	Mantle areolae extending along the whole mantle	G. littoralis
8	Striae ≤ 18 in 10 μm	9
-	Striae ≥ 18 in 10 μm	10
9	Valves 10-17 μm long, 2-3 μm wide; striae 16 in 10 μm	G. obscura
-	Valves 6-8 μm long, 1.7-2.5 μm wide; striae 10-18 in 10 μm	G. domniciae
10	Central area extending to valve/mantle junction	11
-	Central area extending to valve margin	12
11	Transapical striae divided the into two parts	G. sieminskae
-	Transapical striae not divided the into two parts	G. pseudexigua
12	A row of small slits around the foot pole	G. lindae
-	One or two pores around the foot pole	G. novozelandicum

To date, the genus Gomphonemopsis contains thirteen diatom species, six of which have been reported in China seas. This genus may have a wider distribution in the marine coastal waters of subtropical to Polar regions, with the exception of G. oahuensis , which lives in tropical freshwater environments. According to Table 1 , Gomphonemopsis exhibits diverse habitat preferences. Most species are epiphytic on seaweeds and seagrasses, whereas, interestingly, G. gaoi “chooses” copepods as its hosts in this study. This may be not the first report of epizoic modus vivendi in G. gaoi . Lange and Tiffany (2002) found that this species could attach to both green algae and the stalk of the ciliate, but they couldn’t determine whether the ciliate was its strict host. Hence, further ecological studies are needed to reveal the habitats of G. gaoi and other species within the genus.