|Diatom Research (2009), volume 24(1), 233-236|
The genus Ceratoneis Ehrenberg as listed in the online Catalogue of Diatom Names (2007) have 103 names, if redundancy of duplicated entries is ignored. It seems quite possible that most, if not all, of these taxa (and associated names) will end up in different genera, if they have not already been transferred. Many of the freshwater species of Ceratoneis are better placed in Hannaea R.Patr. (although some understand it as synonymous with Fragilaria Lyng., e.g. Krammer & Lange-Bertalot, 1991, 2000), the marine species better placed in Cylindrothecea Rabenh. (Medlin & Mann 2007). In short, Ceratoneis has been used as a ‘dumping ground’ for many unrelated species that happen to have curved valves and, usually, a central area on the concave side. To make matters worse, typification of Ceratoneis is controversial and still being debated (Jahn & Kusber 2005, Medlin & Mann 2007). This paper can (mercifully) avoid these contentious issues as we discuss only specimens named as the new species Ceratoneis iyengarii Gonzalves & Gandhi, a taxon described some 50 plus years ago from a brackish water locality in Mahim Creek, Mumbai (then Bombay), India (Gonzalves & Gandhi 1952). The original Latin description provided by Gonzalves & Gandhi is given in Figure 1; the English translation provided is as follows:
Given the characters usually associated with species of Ceratoneis (curved valves and, usually, a central area on the concave side); it is no surprise these specimens ended up there. Only one figure was provided (Gonzalves & Gandhi 1952, p. 124, fig. 11), reproduced here as Figure 2, rotated through 180o. Gonzalves & Gandhi (1952) cite no particular specimens in the protologue, none that might be interpreted as types (Gonzalves & Gandhi 1952, p. 123, describe it as 'rare').
In 2006 Gandhi’s entire diatom collection was donated to the Energy and Wetlands Research Group at the Centre for Ecological Sciences, Indian Institute of Science (IISc), Bangalore, India and a programme of collection development is being implemented, which will include typifying Gandhi’s taxa well as digitizing the specimens and many drawings. Among the slides, a specimen of Ceratoneis iyengarii was found on Slide No CESH-5-92 (Dharavi rd [road], [Mahim Creek], brackish water, 23-12-45) that resembled the illustration in Gonzalves & Gandhi (1952, fig.1).
Gonzalves & Gandhi (1952, p. 123) provided some basic dimensions, which were compared to the specimen found on No. CESH-5-92 suggesting that they are of similar dimensions:
This specimen is best considered as lectotype. It is clear that the specimen is neither a species of Hannaea nor Cylindrothecea, while both values of the frustule are curved, they differ in structure from each other: the image is actually of a developing frustule of a species of Achnanthes Bory. The frustule illustrated in Figures 3—6, the lectotype, is of an initial araphid valve (Fig. 3a) coupled with the perizonium of the raphid valve (fig. 3b) – the raphid initial cell is not yet formed. Further specimens, from slide no CESH-5-94 ((Dharavi rd [road], [Mahim Creek], brackish water, 23-12-45), also show what appears to be a possibly deformed araphid valve (Fig. 7; maybe a vegetative cell?) and an initial araphid valve also from a species of Achnanthes (Fig. 8).
Comparison of our Figures 3-6 with Sabbe et al. (2004, fig. 42), who illustrate the central and lateral bands of the longitudinal perizonium of Achnanthes cf. subsessilis, show a certain identity in structure and position ( see also Roshchin and Chepurnov 1993, for Achnanthes brevipes var. intermedia (Kutz.) Cleve; Mizuno, 1994 for Achnanthes javanica f. subconstricta (Meister) Hust.; Toyoda et al.2005, for Achnanthes yaquinensis McIntire and Reimer; and Toyoda et al. 2006, figs 26-28 for illustrations of the perizonium and initial values of Achnanthes crenulata Grunow). As for the deformed araphid value in our Figure 7, a similar value for Achnanthes longipes C.A. Agardh was illustrated in Chepurnov and Mann (1999, p. 3), who note "Even during expansion, it was not uncomman for one auxospore to abort in each pair. The contents of such auxospores looked abnormal (Fig. 1) and they never developed into initial cells" (for further details see Roshchin and Chepurnov 1992 and Chepurnov and Mann 1997).
Thus, we conclude that Ceratoneis iyengarii is a name that refers to the early part of the life-cycle of an as yet unidentified species of Achnanthes and its record should be adjusted accordingly for the diatom flora of India.
CATALOGUE OF DIATOM NAMES (2007). California Academy of Sciences, On-line Version (Compiled by Elisabeth Fourtanier & J. Patrick Kociolek). http://www.calacademy.org/research/diatoms/names/index.asp.
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