Additions to the Marine Mastogloia (Bacillariophyceae) from Cuban Coasts; Remarks on Misidentified Taxa

Abstract

During a floristic inspection of sediment samples from Playa Las Gaviotas, 69 specific and infra-specific taxa of Mastogloia were identified in the diatom taxocenosis, including 42 unrecorded taxa for the Cuban coasts. These are added to the 59 Mastogloia taxa previously listed. In this way, currently, the 101 Mastogloia comprised in the benthic diatom associations of the Cuban coast constitute the highest number of taxa ever recorded in similar floristic studies, which also indicates their tropical affinity. Furthermore, observations are made on misidentified taxa such as Mastogloia (Orthoneis) aspera, M. asperuloides, M. (Orthoneis) clevei, M. floridensis, M. latecostata, M. laterorostrata, M. ovata, M. sigillata, M. pseudolatecostata, and others.

1. Introduction

Floristic studies on marine benthic diatoms are still common worldwide [1,2,3,4,5,6,7,8,9,10]. Although these may be underestimated, they constitute the taxonomic basis for further ecological and biogeographical research. However, it has become evident that this type of study is still scarce worldwide, with many marine places and habitats requiring exploration or more in-depth descriptions of benthic diatom associations.

Thus, besides attending the need to correct the floristic problem regarding benthic diatoms, investigating the individual floral components of a diatom taxocenosis may prove useful in the biogeographical characterization of an ecosystem based on the frequency, abundance, and space–time distribution of a certain taxon. An example is the case of Mastogloia Thwaites ex W. Smith whose species and infra-species richness stand out in subtropical and tropical latitudes and worldwide [11,12,13,14]. Diatoms of the genus Mastogloia are naviculoid, isopolar forms characterized by the presence of partecta, i.e., loculate marginal septa in the valvocopulae that bear one or many chambers [15]. Species of this taxon are ubiquitous; however, they find the optimal conditions for their development in warm waters, and most are abundant mainly in epipelic and epiphytic marine assemblages, and some are common in brackish water and freshwater habitats [15,16].

Currently, 292 species names of Mastogloia are accepted out of 420 taxa proposed worldwide [17]. Hustedt’s [18] work alone provided descriptions for 140 Mastogloia taxa from various parts of the planet, while [19] had compiled 89 species and infra-species of Mastogloia for the Caribbean. Later, 75 taxa were recorded [1] solely from the Bahamas Archipelago (Caribbean Sea), and also a higher number of species (>80) were described [20] for several substrata in islands of the same region, which they described and illustrated. Also, there were other floristic studies of epiphytic diatoms of Thalassia testudinum Banks ex König off the coast of Quintana Roo (Caribbean Sea), and 30 Mastogloia taxa were found [21]. And more recently, ref. [13] reported a total of 76 Mastogloia species epiphytic on blades of the seagrass T. testudinum from the coast of Campeche in the southern Gulf of Mexico, which is the highest number of Mastogloia taxa for Mexican coasts. However, in that study, only 51 Mastogloia species or infra-specific taxa were formally identified, while 25 remained with the status of cf. or sp. For the coasts of Cuba, 59 Mastogloia taxa have been hitherto recorded [22].

For the Cuban archipelago, the information on benthic diatom flora is still very scarce and ancient, since most of the research on phytoplankton and phytobenthos in this region dates to the 1970s. The existing research on benthic marine diatoms for Cuba consists mostly of the primary account [22] which includes 395 taxa which resulted from an extensive sampling effort, and a discrete sampling that included benthic diatoms [23]. The objective of this study was to upgrade the species list of Mastogloia that form part of the epipelic diatom associations from sediments of Playa Las Gaviotas, located within the protected marine area Refugio de Vida Silvestre Cayo Santa María on the Cuban coast. So, based on previous accounts of Mastogloia species in several tropical localities, the working hypothesis to be tested was that a significant number (>50%) of species and infra-species would be added to the current species richness of this genus in Cuban coasts, reaching a total of over 90 taxa.

2. Materials and Methods

The sampling site Playa Las Gaviotas is a sandy beach that can be accessed by road, located at 79°11′ and 78°56′ W, and 22°39′ and 22°29′ N, within the marine protected area Refugio de Vida Silvestre Cayo Santa María (Figure 1) on the middle north coast of the Cuban archipelago. It constitutes one of the main areas of the Sabana-Camagüey archipelago, within the biosphere reserve Buenavista. It extends 298.76 km², comprising 43.42 km² of land and 255.32 km² of marine habitats [24]. Cayo Santa María includes an extended seagrass cover with various degrees of plant dominance distributed on a mosaic of muddy, mud–sand, and sandy bottoms [25]. The climate has little variation, but with well-defined rainy (May–October) and dry (November–April) seasons [26].

During November 2021 and July 2022, three sediment samples (replicates) were extracted by free diving at a medium depth of 70 cm in six points along the study area to collect epipelic diatoms from Playa Las Gaviotas (Figure 1). Sampling points were set every 200 m and replicates 2 m apart. A 12 cm diameter Petri dish was used to cut out approximately the first three mm of sediment from the sea-bottom. Sediment samples were preserved in 75% commercial ethanol and kept frozen for later processing in the laboratory.

To separate the diatoms, sediments of each collected replicate were mixed with 60 mL of purified water and treated with ultrasound for two minutes to detach diatoms fixed on the sand grains. The supernatant was separated and let to rest 24 h for the settling of the diatom frustules. Thereafter, 2 mL of the supernatant and remaining sediment were placed in a 150 mL test-tube to which initially 3 mL of nitric acid and 1 mL of 70% ethanol were added to digest all organic matter to clean the frustules so that the morphological characters could be adequately exposed for taxon identification [27]. An exothermal reaction followed, indicating the proper oxidation of organic matter. Whenever the digestive reaction became idle due to excessive organic matter, 2 mL of nitric acid and 1 mL ethanol were added to the mixture, reaching a ratio of 2:5:2 (sample, acid, ethanol). The oxidized sample was diluted with 100 mL distilled water and left to rest 24 h. Thereafter, the sample was rinsed with distilled water every 5 h until reaching a pH ≥ 6.

For mounting permanent slides of the cleaned diatoms, a drop of each replicate was dried on a coverslip and mounted with a drop of synthetic resin Pleurax^® (RI = 1.7) (Bill Daily, University of Pennsylvania) on a glass slide and heated. Three preparations (repetitions) were mounted for each replicate with two coverslips each. The diatom taxa were identified morphologically at 1000× under an Olympus CH-2 compound microscope (Olympus, Japan) equipped with plan-apochromatic lenses and a photographic ocular lens. Finally, an iconographic catalog with micrographs of specimens of representative diatom taxa was assembled. Identification followed: [1,2,6,10,13,15,16,17,18,19,20,21,22,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48]. These were used as a reference for the distribution of the taxa along with [19]. In particular, the taxonomic status of the identified diatoms was updated in Algaebase [17] at: http://algaebase.org/search/species/ (accessed on 15 September 2024) and the Catalogue of Diatom Names of the California Academy of Science [41] at: https://researcharchive.calacademy.org/research/diatoms/names/index.asp (accessed on 15 October 2024).

3. Results

During the floristic inspection of sediment samples from Playa Las Gaviotas (Cuba), 69 specific and infra-specific taxa of Mastogloia were identified within the diatom taxocenosis, including 42 new records (NR). In what follows, the identified Mastogloia taxa and used references are listed, including remarks on frequency, misidentifications, and floristic confusions. Measurements of the largest specimens in this study are given (10 µm).

1.

Mastogloia achnanthioides var. elliptica Hustedt NR (Figure 2a–h)

Hustedt (1933), p. 510, Figure 937d. Not previously recorded in Cuba nor any other locality in the Caribbean Sea. A single specimen was found in the Playa Las Gaviotas sediment samples. Identified according to the description by Hustedt (1933): pp. 509–510, Figure 937d, and the image in Simonsen (1987), p. 140, pl. 226, Figures 3–8. L = 38, W = 18, 12–13 st/10 µm, 13–16 partecta/10 µm. Rare.

2.

Mastogloia adriatica Voigt NR (Figure 2i–l)

Not recorded before for Cuban waters, it was reported as epiphytic for the Bahamas by Hein et al. (2008), p. 58, pl. 33, Figures 1 and 2. As a specimen of M. labuensis var. lanceolata by Loir and Novarino (2013), p. 37, pl. 15, fig. a, it is clearly distinct, with many more partecta. L = 48, W = 15, 17–18st/10 µm, 6 partecta/10 µm. Rare.

3.

Mastogloia affinis Cleve (Figure 3a–c)

Hustedt (1933), p. 487, Figure 910 (Galapagos; Java). In Foged (1984), p. 49, pl. 37, Figure 9. L = 24, W = 8, 12st/10 µm, 3 partecta/10 µm. Common.

4.

Mastogloia angulata F.W. Lewis (Figure 3d,e)

Hustedt (1933), p. 465, Figure 885 (warm coasts). In Foged (1984), p. 49, pl. 33, Figures 3 and 4. L = 65, W = 30, 10st/10 µm, 3 partecta/10 µm. Common.

5.

Mastogloia apiculata W. Smith (Figure 3f–i and Figure 14l,m)

Hustedt (1933), p. 515, Figure 946 (tropical seas). In Foged (1984), p. 49, no image. Very similar to the specimen in Hein et al. (2007), p. 59, pl. 33, Figure 3. L = 38, W = 17.5, 17st/10 µm, 8–9 partecta/10 µm. Common.

6.

Mastogloia (Orthoneis) aspera H. Peragallo and M. Peragallo (1897) NR (Figure 5c,d)

Although presented as Mastogloia barbadensis (Greville) Cleve in Foged (1984), p. 50, pl. 35, Figure 9, said specimen and ours are clearly the Orthoneis aspera described by Peragallo and Peragallo (1897), p. 29, pl. 5, Figure 13. Not resembling the M. aspera described and depicted by Voigt (1942), pl. 5, Figure 31. As indicated in Guiry and Guiry (2024), this taxon’s status deserves attention as either Orthoneis or Mastogloia. L = 45, W = 28, 21/st/10 µm, 3 partecta/10 µm. Single specimen. Rare.

7.

Mastogloia asperula Grunow NR (Figure 4a–c)

Hustedt (1933), p. 481, Figure 901 (Indomalaya region). Not recorded before for Cuban waters but reported by Loir and Novarino (2013), p. 19, pl. 3, fig. a, for the Caribbean Sea as widely distributed. A single specimen in our samples. L = 38, W = 16, 19st/10 µm, 5 partecta/10 µm. Rare.

8.

Mastogloia asperuloides Hustedt NR (Figure 4d,e)

Hustedt (1933), p. 482, Figure 902 (Samoa; Borneo). Although recorded by Foged (1984), p. 49, pl. 36, Figures 1 and 2, for Cuban waters and in the Bahamas by Hein et al. (2008), p, 59 pl. 33, Figure 6, their specimens show very acute ends and very different partecta that do not correspond to the original (Hustedt, 1933) as in Simonsen (1987), p. 137, pl. 223, Figures 1 and 2, as ours does. L = 50, W = 25, 16st/10 µm, 4.5 partecta/10 µm. Rare.

9.

Mastogloia bahamensis Cleve (Figure 5a,b,e–g)

Hustedt (1933), p. 530, Figure 963 (Philippines; Central America). In Foged (1984), p. 49, pl. 36, Figure 3. However, larger specimens were found. L = 50, W = 25, 11st/10 µm, 12 partecta/10 µm. Common.

10.

Mastogloia beaufortiana Hustedt NR (Figure 5k–n)

Hustedt (1955), p. 19, pl. 6, Figure 11 (North Carolina). Hein et al. (2008), p. 60, pl. 35, Figure 1, report a specimen as Mastogloia cf. beaufortiana in the Bahamas, which is more like our specimen and that of Hustedt’s than the one in Simonsen (1987), p. 407, pl. 609, Figures 16–19. M. beaufortiana resembles small specimens (35–45 µm) of M. jelinecki (Figure 5h–j) both in outline and partecta, but it is smaller and lacks the wavy appearance of coarser striae and is much wider. L = 23, W = 10, 12–13st/10 µm, 4–5 partecta/10 µm. Uncommon.

11.

Mastogloia cf. biapiculata Hustedt (Figure 6n,o)

Hustedt (1933), p. 513, Figure 943 (Borneo). A single (not very good) specimen found in the samples with no partecta and imperceptible transverse striae. Previously recorded by Reyes-Vázquez (1975), p. 209, pl. 2, Figure 18, from the Venezuela Caribbean (frequent). Identification based on its outline, compared also with a specimen from Revillagigedo Islands Siqueiros Beltrones et al. (2022). L = 48, W = 16. Rare.

12.

Mastogloia binotata (Grunow) Cleve (Figure 19n,o)

Hustedt (1933), p. 470, Figure 889 (warm coasts). In Foged (1984) p. 50, pl. 37, Figure 12. L = 24, W = 17, 14 st/10 µm, 1 partectum/10 µm. Common.

13.

Mastogloia biocellata (Grunow) G. Novarino and A.R. Muftah (Figure 6a,b)

Hustedt (1933), p. 524, Figure 959 d, and in Foged (1984) as M. erythraea var. biocellata, p. 52, pl. 4, Figure 2. L = 22, W = 8, striae imperceptible, 7 partecta/10 µm. Common.

14.

Mastogloia bisulcata Grunow NR (Figure 6c–j)

Taxon described by Grunow (1877) from Honduras, p. 176, pl. 195, Figure 6. He distinguished it from M. minuta by noticing two distinctive longitudinal smooth furrows bordering the partecta (not visible in the original description). Initially mistaken for M. decipiens in the Cuban samples but discriminated likewise. L = 28, W = 12, 18 st/10 µm, 6 partecta/10 µm. Common.

15.

Mastogloia (Orthoneis) clevei Grunow NR (Figure 22a–d)

Hustedt (1933), p. 464, Figure 884 as M. fimbriata (warm coasts). After the original record by Van Heurck (1880), pl. 28, Figure 4, most of the time it has been identified as M. fimbriata as in Navarro (1983), p. 121, Figures 34–37, Witkowski et al. (2000), p.247, pl.77, Figures 1–4; pl. 83, Figures 1–4; Hein et al. (2008), p. 66, pl. 38, Figures 1 and 3; Lobban et al. (2012), p. 273, pl. 28, Figures 8–11; Loir and Novarino (2013), p. 32, Figure 11c and Siqueiros Beltrones (2021), p. 10, Figures 8g and 15a–h, disregarding the discriminating difference in the form of the partecta. L = 39, W = 25, 9 st (margin)-11/10 µm, 3 partecta/10 µm. Common.

16.

Mastogloia cocconeiformis Grunow (Figure 24a–c)

Hustedt (1933), p. 469, Figure 888 (warm coasts). In Foged (1984), p. 50, pl. 32, Figures 16 and 17. L = 34, W = 28, 20 st/10 µm, 7 partecta/10 µm. Common conspicuous taxon.

17.

Mastogloia corsicana (Grunow) H. Peragallo and M. Peragallo (Figure 7a–g)

Hustedt (1933), p. 533, Figure 966 (warm coasts). In Foged (1984), p. 51, pl. 35, Figures 4 and 5. L = 35, W = 11, 15st/10 µm, 6 partecta/10 µm. Common.

18.

Mastogloia corsicana var. capitata Meister NR (Figure 7j–n)

Previously recorded only for the Bahamas by Hein et al. (2008), p. 62, pl. 34, Figure 5, commonly distributed in various substrates. L = 22, W = 7.5, 18st/10 µm, 9 partecta/10 µm. Uncommon.

19.

Mastogloia cribrosa Grunow (Figure 23a–d)

Hustedt (1933), p. 468, Figure 887 (warm coasts; Mediterranean). In Foged (1984), p. 51, pl. 33, Figure 2. L = 26, W = 21, 14st/10 µm, 3 partecta/10 µm. Common.

20.

Mastogloia crucicula (Grunow) Cleve (Figure 19d–g)

Hustedt (1933), p. 475, Figure 894 (Samoa). In Foged (1984), p. 51, pl. 37, Figures 7 and 8. L = 18, W = 9, 19st/10 µm, 1.5 partecta/10 µm. Common.

21.

Mastogloia crucicula var. alternans Zanon NR (Figure 19h,i)

Previously recorded only for the Bahamas by Hein et al. (2008), p. 63, pl. 36, Figure 5, infrequent in several habitats. L = 11, W = 7, 22st/10 µm, 2 partecta/10 µm. Common.

22.

Mastogloia cuneata (Meister) Simonsen NR (Figure 8a,b)

Previously recorded only for the Bahamas by Hein et al. (2008), p. 63, pl. 36, Figure 4. Although pictured by Foged (1984), he identified this taxon (and M. inaequalis) as M. schmidtii. L = 29, W = 6, striae imperceptible, 8–10 partecta/10 µm. Common.

23.

Mastogloia decipiens Hustedt (Figure 8c–k)

Hustedt (1933), p. 504, Figure 929 (Adriatic Sea). In Foged (1984), p. 51, pl. 37, Figure 17. L = 30, W = 14, 24st/10 µm, 7 partecta/10 µm. Common.

24.

Mastogloia delicatissima Hustedt NR (Figure 8n–r)

Hustedt (1933), p. 482, Figure 903 (Borneo). Previously recorded only for the Bahamas by Hein et al. (2008), p. 64, pl. 36, Figure 9. Although this species is very similar to M. cannii, based on their co-occurrence in Siqueiros Beltrones et al. (2021; 2022), there is a distinction in the shape of the partecta, square in M. cannii, elongated in M. delicatissima. L = 20, W = 10, striae imperceptible, 6 partecta/10 µm. Common.

25.

Mastogloia lucayensis Lobban and Franckovich NR (Figure 8s–x)

Recorded as M. discontinua Paddock and Kemp for the Bahamas by Hein et al. (2008), p. 64, pl. 36, Figure 9. L = 35, W = 11, 14st/10 µm, 8 partecta/10 µm. Common.

26.

Mastogloia elegans Lewis (Figure 9a–d)

Hustedt (1933), p. 498, Figure 924 (North America coasts; Java). In Foged (1984), p. 52, pl. 35, Figures 1 and 2. Common. However, his specimen and that of Hein et al. (2008) resemble more closely the M. jelinecki (Grunow) Grunow depicted in Hustedt (1933), while ours is the same as in Yohn and Gibson (1982a) and Navarro (1983), p. 120, Figures 32 and 33. Outline and striae similar also to M. pseudoelegans (see below). L = 58, W = 20, 16st/10 µm, 4 partecta/10 µm. Uncommon.

27.

Mastogloia emarginata Hustedt (Figure 20k–m)

Hustedt (1933), p. 477, Figure 896 (Borneo). In Foged (1984), p. 52, pl. 36, Figures 14 and 15. L = 17, W = 9, 22st/10 µm, 3 partecta/10 µm. Common.

28.

Mastogloia erythraea Grunow (Figure 9e–g)

Hustedt (1933), p. 524, Figure 959 (warm coasts; Mediterranean). In Foged (1984), p. 52, pl. 35, Figure 3. L = 35, W = 12, 24st/10 µm, 7–8 partecta/10 µm. Common.

29.

Mastogloia fallax f. biloculis Foged (Figure 10a–f)

Foged (1984), p. 53, pl. 37, Figures 1 and 2. L = 36, W = 15, 20st/10 µm, 6 partecta/10 µm. Common.

30.

Mastogloia fimbriata (Brightwell) Cleve (Figure 22i–l)

Hustedt (1933), p. 464, Figure 884 (warm coasts; Mediterranean). In Foged (1984), p. 53, pl. 32, Figure 14. L = 35, W = 25, 9 st/10 µm, 1 partectum/10 µm. Common.

31.

Mastogloia floridensis Lobban and Franckovich NR (Figure 11a–c)

Recorded by Hein et al. (2008) for the Bahamas as M. frickei, p. 66, pl. 38, Figure 4, and Siqueiros Beltrones et al. (2020), wrongly following Hustedt (1933), p. 534, Figure 967. L = 60, W = 15, 16st/10 µm, 13 partecta/10 µm. Uncommon.

32.

Mastogloia funafutensis A.W.F. Schmidt NR (Figure 6l,m)

Hustedt (1933), p. 511, Figure 938 (Indian Ocean). Previously recorded only for the Bahamas by Hein et al. (2008), p. 67, pl. 40, Figure 1, as M. cf. funafutensis but images agree in outline and areolae, especially with that of Schmidt et al. (1874–1959) and in the shape of the partecta (though the authors prefer to be cautious). L = 58, W = 24, 9 st/10 µm, 7 partecta/10 µm. Uncommon.

33.

Mastogloia gilberti A. Schmidt NR (Figure 11d,e)

Hustedt (1933), p. 479, Figure 899 (warm coasts). Not hitherto recorded for the Caribbean, although we believe that Foged’s (1984) M. gracillima, p. 53, pl. 33, Figure 6, is actually M. gilberti as in Schmidt et al. (1874–1959), pl. 187, Figures 14 and 15, according to the outline and longer partecta, as can be noted in Figure 11f,g (M. gracillima) vs. M. gilberti; but see also the comparison with M. sublatericia. L = 25, W = 14, 19 st/10 µm, 5 partecta/10 µm. Common.

34.

Mastogloia gracillima Hustedt (Figure 11f,g)

Hustedt (1955), p. 19, pl. 6, Figure 16 (North Carolina). Reported by Foged (1984), p. 53, pl. 33, Figure 6, but as noted above, represented with a specimen of M. gilberti. Here its outline is like that in Simonsen (1987) with longer partecta. L = 23, W = 13, 18 st/10 µm, 4.5 partecta/10 µm. Common.

35.

Mastogloia graciloides Hustedt NR (Figure 11h–n)

Hustedt (1933), p. 508, Figure 934 (Borneo). Allegedly recorded for Cuba by López and Borrero (1977; in Hernández-Becerril and Navarro, 1987), but the record is not available for contrast with the M. ignorata reported by Foged (1984) that seems like M. graciloides, clearly distinguished in Simonsen (1987), p. 140, pl. 225, Figures 9 and 10. L = 33, W = 12, 17 st/10 µm, 7 partecta/10 µm. Common.

36.

Mastogloia cf. horvathiana Grunow (Figure 14n)

Hustedt (1933), p. 471, Figure 890 (warm coasts; Mediterranean). For the region, Navarro (1983), p. 121, Figure 38, recorded it for Puerto Rico and Hein et al. (2008), p. 67, pl. 41, Figure 1, in the Bahamas, both as uncommon. Although we found a single specimen in bad shape (no partectal ring), it can be tentatively recognized by its football outline and number of striae (10/10 µm) as in Siqueiros Beltrones et al. (2020), Figure 6k,l. However, it needs confirmation to be proposed as a new record for Cuban waters. L = 55, W = 32, 10 st/10 µm. Rare.

37.

Mastogloia jelineckii var. extensa (Grunow) Voigt NR (Figure 5h–j and Figure 12a–n)

Hustedt (1933), p. 544, Figure 977 shows only M. jelineckii. Voigt (1963), p. 116, pl. 25, Figure 1, proposes this new variety that resembles closely the larger form the former author which Foged (1984) records (not illustrated). These and those in Pennesi et al. (2012), p. 1251, Figures 1h,i and 5, and in the original description by Grunow (1877), p. 174, pl. 195, Figure 1, agree well with our specimens. L = 58, W = 22, 18 st/10 µm, 4 partecta/10 µm. Common.

38.

Mastogloia lacrimata Voigt NR (Figure 13a–e)

Previously recorded only in the region by Hein et al. (2008) for the Bahamas, p. 67, pl. 33, Figure 7. And, it has been recorded from the Revillagigedo Islands, Pacific Ocean (Siqueiros Beltrones et al., 2022), p. 12, Figures 12i–s and 26j–k. L = 30, W = 14, 20 st/10 µm, 4 partecta/10 µm. Common.

39.

Mastogloia latecostata Hustedt NR (Figures 20a–c and 23m,n)

Hustedt (1933), p. 536, Figure 969 (Java; Honduras). Recorded by Yohn and Gibson (1982a), p. 43, Figure 19a,b, for the Bahamas. Certain confusion may occur when compared with M. pseudolatecostata, discernible mainly by the subdivided partecta. We show specimens identical to the one in Hustedt (1933) p. 537, Figure 969. L = 34, W = 21, 14 st/10 µm, 6 partecta/10 µm. Uncommon.

40.

Mastogloia laterorostrata Hustedt NR (Figure 13f–i)

Hustedt (1933), p. 516, Figure 948 (Samoa). Simonsen (1987), p. 141, pl.227, Figures 11 and 12. Hitherto unrecorded for the Caribbean region. Very likely confused with M. decipiens or even with M. bisulcata due to their similar outline and disposition of partecta. However, in this taxon, the striae are coarser and the partecta larger and fewer than in M. decipiens, while lacking the longitudinal furrows in M. bisulcata. L = 27, W = 10, 20 st/10 µm, 5 partecta/10 µm. Uncommon.

41.

Mastogloia lineata var. albifrons (Brun) Hustedt (Figure 6k)

Hustedt (1933), p. 539, Figure 972 (Bahamas). In Foged (1984), p. 54, no image. A single incomplete specimen lacking partecta, but with an outline and valvar structure much like the image in Hustedt (1933); occurring in the region (Bahamas). L = 40, W = 20, 20 st/10 µm. Rare.

42.

Mastogloia manokwariensis Cholnoki NR (Figure 13j–m)

Small form, with taxonomic traits being difficult to see. Most likely the same as the M. pusilla v. subcapitata in Foged (1984), p. 56, pl. 36, Figures 12 and 13; pl. 37, Figure 18. Our specimens agree with those in Witkowski et al. (2000), p. 253, pl. 80, Figure 11, and Hein et al. (2008), p. 68, pl. 38, Figure 2, in general form (outline and partecta). In contrast, the partecta differ from those of the M. pusilla v. subcapitata drawing in Hustedt (1933). L = 17.5, W = 8, 25 st/10 µm, 5.5 partecta/10 µm. Common.

43.

Mastogloia matthaei Pennesi and Poulin NR (Figure 19j–m)

Until the description by Pennesi et al. (2013), p. 10, Figures 53–56, this taxon had been most likely included with M. emarginata. However, the partecta are much longer relatively in M. matthaei. L = 14, W = 8, 20 st/10 µm, 2 partecta/10 µm. Common.

44.

Mastogloia mauritiana Brun NR (Figure 13n,o)

Hustedt (1933), p. 563, Figure 995 (Mediterranean). Recorded for the Caribbean Sea by Hein et al. (2008), p. 68, pl. 42, Figure 1, for the Bahamas, and Loir and Novarino (2013), p. 38, pl. 16, fig. b, for the French Lesser Antilles, where it co-occurs with similar taxa such as M. mauritiana v. capitata and M. peragalli. L = 34, W = 17, 24 st/10 µm, 11 partecta/10 µm. Uncommon.

45.

Mastogloia mauritiana var. capitata Voigt NR (Figure 13p,q)

Recorded by Hein et al. (2008), p. 68, pl. 42, Figure 2, in the Bahamas, and gathered by Loir and Novarino (2013), p. 42, pl. 18, fig. b, in the French Lesser Antilles, although they identified it as M. peragalli. L = 32, W = 15, 28 st/10 µm, 9 partecta/10 µm. Common.

46.

Mastogloia minuta Greville NR (Figure 14a–e)

Taxon recorded by Grunow (1877) from Honduras p. 176, pl. 195, Figure 7. Similar to M. bisulcata but distinguishable for lacking the two longitudinal furrows and for having much finer striae that also set it apart from M. decipiens. L = 18, W = 9, striae imperceptible, 11 partecta/10 µm. Common.

47.

Mastogloia ovata Grunow (Figures 20g–j and 21a,b,n–r)

Hustedt (1933), p. 476, Figure 895 (warm coasts). Although recorded by Foged (1984), no image is provided. This taxon shows much morphological variation; thus, images from different specimens are required considering a potential confusion with other Ellipticae such M. latecostata and M. pseudolatecostata as in Siqueiros Beltrones (2022). Our specimen, 21a-b, is very similar to the M. ovata in Hustedt (1933), p. 476, Figure 895, and Witkowski et al. (2000), pl. 82, Figure 1, but also to the M. pseudolatecostata specimen in Lobban et al. (2012), pl. 35, Figures 1 and 2. L = 28, W = 21, 18 st/10 µm, 5–6 partecta/10 µm. Common

48.

Mastogloia parva Hustedt NR (Figure 14i–k)

Hustedt (1933), p. 513, Figure 942 (Borneo). Hitherto unrecorded for the Caribbean region, but found as epiphyte in Campeche Bay, Mexico (Siqueiros Beltrones et al., 2020), p. 8, Figure 8n. May be confused with small specimens of M. subaffirmata, though their partecta are quite different. Single specimen (not good), L = 22, W = 9, 12 longitudinal st/10 µm, 8 partecta/10 µm. Uncommon.

49.

Mastogloia peracuta Janisch NR (Figure 14f–h)

Hustedt (1933), p. 485, Figure 906 (Leton Bay). Recorded by Navarro (1983), p. 121, Figures 52 and 53, from Puerto Rico, Hein et al. (2008), p. 70, pl. 43, Figure 1, in various substrata in the Bahamas, and Loir and Novarino (2013), p. 41, pl. 18, fig. a, in Martinique. L = 32, W = 16, 17 st/10 µm, 4 partecta/10 µm. Rare.

50.

Mastogloia pisciculus Cleve NR (Figure 15j,k)

Hustedt (1933), p. 558, Figure 990 (Pensacola). Hitherto recorded only by Loir and Novarino (2013), p. 42, pl. 18, fig. c, in the French Lesser Antilles, with a report from Florida Coast. L = 42, W = 14, 30 st/10 µm, 3 partecta/10 µm. Rare.

51.

Mastogloia pseudoelegans Hustedt (Figure 15f,g)

Hustedt (1955), p. 19, pl. 6, Figure 10 (North Carolina). Although in Foged (1984), depicted as M. asperuloides, p. 55, pl. 34, Figure 3. Distinguished by the rectangular horizontal partecta vs. the vertically elongated partecta in M. elegans. Also found in Hein et al. (2008). L = 58, W = 20, 20 st/10 µm, 9 partecta/10 µm. Uncommon.

52.

Mastogloia pseudolacrimata Yohn, T.A. and R.A. Gibson NR (Figure 15a–e,h,i)

A conspicuous taxon, described by Yohn and Gibson (1982a), p. 42, Figure 7a,b, for the Bahamas, and later recorded by Hein et al. (2008), p. 70, pl. 43, Figures 4 and 6, in multiple substrata albeit with smaller specimens (28 µm). Here, we depict a wider range of sizes (>30 µm). Not reported by Loir and Novarino (2013). L = 44, W = 23, 14 st/10 µm, 9 partecta/10 µm. Common.

53.

Mastogloia pseudolatecostata Yohn, T.A. and R.A. Gibson NR (Figures 20d–f, 21c–m and 23o,p)

Originally described by Yohn and Gibson (1982a), p. 43, Figure 20a,b for the Bahamas and by Hein et al. (2008), p. 70, Figures 1–3 and 45. They observed that this taxon is morphologically like M. latecostata but can be discriminated against by having partecta with central notches instead of being subdivided by a primitive septum. We show specimens (20d-f) identical to the one in Witkowski et al. (2000), p. 258, pl. 77, Figures 5 and 6, as well as others that depart from the general outline. L = 28, W = 18, 20 st/10 µm, 6 partecta/10 µm. Common.

54.

Mastogloia punctatissima (Greville) Ricard NR (Figures 22e–h and 23i–l)

Hustedt (1933) as M. splendida (Greg.) Cleve (coasts of all seas), p. 463, Figure 883. A widely distributed conspicuous taxon, v.gr., common at Revillagigedo Islands (Siqueiros Beltrones et al., 2021), p. 14, Figures 2b, 23a–d and 24a–d. Identified also as M. splendida by Foged (1984) and in earlier works. Correctly reported by Hein et al. (2008), p. 71, pl. 44, Figures 1 and 2 from the Bahamas. L = 48, W = 35, 10 st/10 µm, 10 partecta/10 µm. Common.

55.

Mastogloia punctifera Brun (Figure 16a–k)

Hustedt (1933), p. 490, Figure 914 (Mediterranean). In Foged (1984), p. 56, pl. 37, Figure 3. Image is barely discernible but comparable to Hustedt (1933). Better references in Hein et al. (2008), Paddock and Kemp (1988), Siqueiros Beltrones et al. (2020). Not in Loir and Novarino (2013). L = 29, W = 13, 24 st/10 µm, 7 partecta/10 µm. Common.

56.

Mastogloia rigida Hustedt NR (Figure 7h,i)

Hustedt (1933), p. 531, Figure 964 (Honduras). Although M. rigida appears in Foged (1984), the image in pl. 37, Figure 3, does not match Figure 964 in Hustedt (1933) nor in Simonsen (1987), Figures 8, 9 and 230. It seems to be something else, so it cannot be regarded as a record. Our specimen does match figures in both references and constitutes an actual new record. L = 30, W = 11, 14 st/10 µm, 8 partecta/10 µm. Rare.

57.

Mastogloia rimosa Cleve NR (Figure 16l–p)

Although mentioned by Hustedt (1933) p. 534 from the Bahamas, no image is provided. Recorded from the same area by Hein et al. (2008), pl. 46, Figures 3 and 5, albeit not reported in Loir and Novarino (2013). L = 48, W = 17, 11 st/10 µm, 10 partecta/10 µm. Uncommon.

58.

Mastogloia rostellata Grunow (Figure 17a–c)

Hustedt (1933), p. 485, Figure 907 (Seychelles). In Foged (1984), p. 56, pl. 32, Figure 15. Recorded also by Hein et al. (2008), Loir and Novarino (2013) for the region. L = 48, W = 19, 16 st/10 µm, 4.5 partecta/10 µm. Uncommon.

59.

Mastogloia sigillata Voigt NR (Figure 19a–c)

Hitherto unrecorded for the Caribbean region. These specimens were initially identified as M. ovalis; however, the M. sigillata proposed as a new species by Voigt (1963), p. 118, pl. 24, Figures 3 and 4 is clearly the same taxon as ours. First record for the region. L = 29, W = 16, 15 st/10 µm, 4 partecta/10 µm. Uncommon.

60.

Mastogloia similis Hustedt (Figure 17d–h)

Hustedt (1933), p. 522, Figure 955 (Borneo), distinguished from M. seychelensis and M. lunula (Voigt, 1942), which seem to be the same, by the disposition of partecta and the angular base of the tips. In Foged (1984), although the images do shed confusion on which one is M. similis and if the other is M. paradoxa which has a wavy raphe vs. a straight one in the former. Our specimens match those in Hein et al. (2008), Witkowski et al. (2000) and Simonsen (1987). L = 40, W = 10, striae imperceptible, 5/8 partecta/10 µm. Common.

61.

Mastogloia sp. 1 NR (Figures 20e–h, 21a,b,r–n and 24d–k)

Specimens of this unidentified taxon in this study were proposed as M. ovata by Hein et al. (2008), p. 69, pl. 38, Figure 5, a-b, and Lobban et al. (2012), p. 279, pl. 33, Figures 7 and 8. But, although certain similarities are evident such as the partecta, the striae show no longitudinal patterns as seen in Hustedt (1933), p. 476, Figure 895a-c, or Witkowski (2000), p. 255, pl. 82, Figure 1, nor in the present work. L = 26, W = 21, 22 st/10 µm, 5.5 partecta/10 µm. Common.

62.

Mastogloia staurophora Hustedt NR (Figure 17l,m)

Hustedt (1933), p. 514, Figure 945 (Seychelles, Indian Ocean). Small inconspicuous taxon with a stauros-like structure barely visible. First recorded for the Caribbean Sea by Navarro (1983), p. 122, Figures 66 and 67; then Hein et al. (2008), p. 72, pl. 45, Figures 4 and 5, and Loir and Novarino (2013), p. 48, pl. 22, fig. c. L = 23, W = 7, 25 st/10 µm, partecta imperceptible. Rare.

63.

Mastogloia stephensiana Yohn, T.A. and R.A. Gibson NR (Figure 17i–k)

A common and conspicuous taxon first recorded and described by Yohn and Gibson (1982), p. 44, Figures 30a,b and 31a,b, for Bahamas. Smaller specimens resemble M. sublatericia which is more rounded, less rostrate, and has coarser striae (Simonsen, 1987, pl. 222, Figures 12–15). L = 36, W = 16, 17 st/10 µm, 3 partecta/10 µm. Common.

64.

Mastogloia subaffirmata Hustedt (Figure 18a,b,f–h)

Hustedt (1933), p. 526, Figure 960 a-f (Borneo). In Foged (1984), p. 57, pl. 36, Figures 8 and 9. A taxon showing high morphological variation as shown in Hein et al. (2008) for various substrata in Bahamas. Frequently confused with M. cyclops, as in Witkowski et al. (2000) and Loir and Novarino (2013), which shows a conspicuous stigma near the central area that is lacking in M. subaffirmata, clearly indicated by Lobban et al. (2012). L = 37, W = 16, 22 st/10 µm, 12 partecta/10 µm. Common.

65.

Mastogloia sublatericia Hustedt NR (Figure 18c–e,i,j)

Hustedt (1933), p. 479, Figure 900 (Bislang). Hitherto not recorded for the Caribbean region. A small taxon that may be mistaken for smaller specimens of M. stephensiana having somewhat similar partecta but bigger, coarser striae, and less capitated apices. It may also be confused with M. gilberti which is similarly capitated, but this taxon has very different partecta which are clearly squarer. L = 25, W = 12, 18 st/10 µm, 2.5 partecta/10 µm. Common.

66.

Mastogloia tenera Hustedt NR (Figure 18m,n)

Hustedt (1933), p. 494, Figure 919 (Borneo). Recorded only for the Caribbean (Lesser Antilles) by Loir and Novarino (2013), p. 49, pl. 23, fig. b, as an uncommon taxon. L = 42, W = 12, 19 st/10 µm, 5 partecta/10 µm. Rare.

67.

Mastogloia tenuis Hustedt NR (Figure 18k,l)

Hustedt (1933), p. 570, Figure 1004 (Borneo). Also recorded for the Caribbean (Lesser Antilles) by Loir and Novarino (2013), p. 49, pl. 23, fig. c, as an uncommon taxon. L = 47, W = 9.5, striae imperceptible, 4 partecta/10 µm. Rare.

68.

Mastogloia umbra Paddock and Kemp NR (Figure 18r,s)

Hitherto known only from the Bermuda Islands, from which Paddock and Kemp (1988), p. 117, Figures 39–44, originally described it. They relate it to M. varians with which it has been most likely confused where these taxa co-occur (see next report). However, the striae are much finer and the partecta longer than in M. varians. L = 20, W = 7, striae imperceptible, 5 partecta/10 µm. Common.

69.

Mastogloia varians Hustedt (Figure 18o–q)

In Foged (1984), p. 58, pl. 36, Figures 10 and 11. However, his image more resembles M. affinis (Hustedt, 1933) as long partecta can be barely discerned like in this taxon and it also has coarser striae. Unlike our M. varians which as described by Hustedt (1933), p. 486, Figure 909, shows a similar outline and striae variation with shorter and more numerous partecta. L = 19, W = 8, 20 st/10 µm, 5 partecta/10 µm. Common.

Figure 2. (a–h) Mastogloia achnanthioides var. elliptica; (i–l) M. adriatica. Scale bar = 10 µm.

Figure 2. (a–h) Mastogloia achnanthioides var. elliptica; (i–l) M. adriatica. Scale bar = 10 µm.

Figure 3. (a–c) Mastogloia affinis; (d,e) M. angulata; (f–i) M. apiculata. Scale bar = 10 µm.

Figure 3. (a–c) Mastogloia affinis; (d,e) M. angulata; (f–i) M. apiculata. Scale bar = 10 µm.

Figure 4. (a–c) Mastogloia asperula; (d,e) M. asperuloides. Scale bar = 10 µm.

Figure 4. (a–c) Mastogloia asperula; (d,e) M. asperuloides. Scale bar = 10 µm.

Figure 5. (a,b,e–g) Mastogloia bahamensis; (c,d) M. (Orthoneis) aspera; (h–j) M. jelinecki var. extensa; (k–n) M. beaufortiana. Scale bar = 10 µm.

Figure 5. (a,b,e–g) Mastogloia bahamensis; (c,d) M. (Orthoneis) aspera; (h–j) M. jelinecki var. extensa; (k–n) M. beaufortiana. Scale bar = 10 µm.

Figure 6. (a,b) Mastogloia biocellata; (c–j) M. bisulcata; (k) M. lineata var. albifrons; (l,m) M. funafutensis; (n,o) M. cf. biapiculata. Scale bar = 10 µm.

Figure 6. (a,b) Mastogloia biocellata; (c–j) M. bisulcata; (k) M. lineata var. albifrons; (l,m) M. funafutensis; (n,o) M. cf. biapiculata. Scale bar = 10 µm.

Figure 7. (a–g) Mastogloia corsicana; (h,i) M. rigida; (j–n) M. corsicana var. capitata. Scale bar = 10 µm.

Figure 7. (a–g) Mastogloia corsicana; (h,i) M. rigida; (j–n) M. corsicana var. capitata. Scale bar = 10 µm.

Figure 8. (a,b) Mastogloia cuneata; (c–k) M. decipiens; (n–r) M. delicatissima; (l,m,s–x) M. lucayensis. Scale bar = 10 µm.

Figure 8. (a,b) Mastogloia cuneata; (c–k) M. decipiens; (n–r) M. delicatissima; (l,m,s–x) M. lucayensis. Scale bar = 10 µm.

Figure 9. (a–d) Mastogloia elegans; (e–g) M. erythraea. Scale bar = 10 µm.

Figure 9. (a–d) Mastogloia elegans; (e–g) M. erythraea. Scale bar = 10 µm.

Figure 10. (a–f) Mastogloia fallax f. biloculis. Scale bar = 10 µm.

Figure 10. (a–f) Mastogloia fallax f. biloculis. Scale bar = 10 µm.

Figure 11. (a–c) Mastogloia floridensis; (d,e) M. gilberti; (f,g) M. gracillima; (h–n) M. graciloides. Scale bar = 10 µm.

Figure 11. (a–c) Mastogloia floridensis; (d,e) M. gilberti; (f,g) M. gracillima; (h–n) M. graciloides. Scale bar = 10 µm.

Figure 12. (a–n) Mastogloia jelinecki var. extensa. Scale bar = 10 µm.

Figure 12. (a–n) Mastogloia jelinecki var. extensa. Scale bar = 10 µm.

Figure 13. (a–e) Mastogloia lacrimata; (f–i) M. laterorostrata, (j–m) M. manokwariensis; (n,o) M. mauritiana; (p,q) M. mauritiana var. capitata. Scale bar = 10 µm.

Figure 13. (a–e) Mastogloia lacrimata; (f–i) M. laterorostrata, (j–m) M. manokwariensis; (n,o) M. mauritiana; (p,q) M. mauritiana var. capitata. Scale bar = 10 µm.

Figure 14. (a–e) Mastogloia minuta; (f–h) M. peracuta; (i–k) M. parva; (l,m) M. apiculata; (n) Mastogloia cf. horvathiana. Scale bar = 10 µm.

Figure 14. (a–e) Mastogloia minuta; (f–h) M. peracuta; (i–k) M. parva; (l,m) M. apiculata; (n) Mastogloia cf. horvathiana. Scale bar = 10 µm.

Figure 15. (a–e,h,i) M. pseudolacrimata; (j,k) M. pisciculus; (f,g) M. pseudoelegans. Scale bar = 10 µm.

Figure 15. (a–e,h,i) M. pseudolacrimata; (j,k) M. pisciculus; (f,g) M. pseudoelegans. Scale bar = 10 µm.

Figure 16. (a–k) Mastogloia punctifera; (l–p) M. rimosa. Scale bar = 10 µm.

Figure 16. (a–k) Mastogloia punctifera; (l–p) M. rimosa. Scale bar = 10 µm.

Figure 17. (a–c) Mastogloia rostellata; (d–h) M. similis; (i–k) M. stephensiana; (l,m) M. staurophora. Scale bar = 10 µm.

Figure 17. (a–c) Mastogloia rostellata; (d–h) M. similis; (i–k) M. stephensiana; (l,m) M. staurophora. Scale bar = 10 µm.

Figure 18. (a,b,f–h) Mastogloia subaffirmata; (c–e,i,j) M. sublatericia; (k,l) M. tenuis; (m,n) M. tenera; (o–q) M. varians; (r,s) M. umbra. Scale bar = 10 µm.

Figure 18. (a,b,f–h) Mastogloia subaffirmata; (c–e,i,j) M. sublatericia; (k,l) M. tenuis; (m,n) M. tenera; (o–q) M. varians; (r,s) M. umbra. Scale bar = 10 µm.

Figure 19. (a–c) Mastogloia sigillata; (d–g) M. crucicula; (h,i) M. crucicula var. alternans; (j–m) M. matthaei; (n,o) M. binotata. Scale bar = 10 µm.

Figure 19. (a–c) Mastogloia sigillata; (d–g) M. crucicula; (h,i) M. crucicula var. alternans; (j–m) M. matthaei; (n,o) M. binotata. Scale bar = 10 µm.

Figure 20. (a–c) Mastogloia latecostata; (d–f) M. pseudolatecostata; (g–j) M. ovata; (k–m) M. emarginata. Scale bar = 10 µm.

Figure 20. (a–c) Mastogloia latecostata; (d–f) M. pseudolatecostata; (g–j) M. ovata; (k–m) M. emarginata. Scale bar = 10 µm.

Figure 21. (a,b,n–r) Mastogloia ovata; (c–m) M. pseudolatecostata. Scale bar = 10 µm.

Figure 21. (a,b,n–r) Mastogloia ovata; (c–m) M. pseudolatecostata. Scale bar = 10 µm.

Figure 22. (a–d) Mastogloia clevei; (e–h) M. punctatissima; (i–l) M. fimbriata. Scale bar = 10 µm; and 20 µm for M. punctatissima.

Figure 22. (a–d) Mastogloia clevei; (e–h) M. punctatissima; (i–l) M. fimbriata. Scale bar = 10 µm; and 20 µm for M. punctatissima.

Figure 23. (a–d) Mastogloia cribrosa; (e–h) M. sp.1; (i–l) M. punctatissima; (m,n) M. latecostata; (o,p) M. pseudolatecostata. Scale bar = 10 µm; and 20 µm for M. punctatissima.

Figure 23. (a–d) Mastogloia cribrosa; (e–h) M. sp.1; (i–l) M. punctatissima; (m,n) M. latecostata; (o,p) M. pseudolatecostata. Scale bar = 10 µm; and 20 µm for M. punctatissima.

Figure 24. (a–c) Mastogloia cocconeiformis; (d–k) Mastogloia sp.1. Scale bar = 10 µm.

Figure 24. (a–c) Mastogloia cocconeiformis; (d–k) Mastogloia sp.1. Scale bar = 10 µm.

4. Discussion

More than 40 years after the first comprehensive work [22], the benthic diatom flora of the Cuban coasts is undergoing its first formal update. The overall floristic list is currently being constructed and used to describe the structure of the diatom taxocenosis. Meanwhile, certain taxa considered as indicators of environmental conditions depicting biogeographical distributions, such as Mastogloia species [14], are being inspected. In this way, with 42 new records, the number of Mastogloia taxa is increased by ca. 73%, from 59 to 101. This increase supported our working hypothesis which, although simple, was well founded and instigated a thorough search for expected unreported taxa.

In general, the species and infra-species of Mastogloia are frequently the most diverse within benthic marine assemblages from warm seas of tropical and subtropical latitudes where they occur in high numbers and with species richness [11,12,13,14]. However, finer biogeographical observations are required as some taxa are being recorded in distant and isolated localities, such as the Cuban littorals and the Revillagigedo Islands, such as M. pseudolatecostata, M. ovata, M. gilberti, M. lacrimata, and others more common and widely distributed like the Ellipticae forms. In contrast, the fact that several conspicuous Mastogloia taxa from [22] were missing in this study (M. braunni, M. citrus, M. corsicana v. constricta, M. meisteri) provides a warning about the comprehensiveness of the sampling strategies required for making biogeographical inferences. It is likely that further sampling may help to confirm the identification of Mastogloia horvathiana by providing better specimens.

The Mastogloia are clearly distinguished from other genera of diatoms by the presence of partecta, which also correspond with the general outline and striae patterns. Nonetheless, in many cases, the similarity between species and infra-species of Mastogloia makes them difficult to identify. This is evidenced in most studies where the identification and/or description of the Mastogloia taxa are either part of a wide floristic study or one that has been expressly undertaken such as the early works by [20,44]. In the present study, besides the new records for the Cuban coasts, the relatively recent new taxa found in the Caribbean region such as M. umbra [32], M. pseudolatecostata, M. stephensiana, M. pseudolacrimata [31], which were barely available during the work by [22], made this floristic update necessary.

The process for separating certain established Mastogloia taxa is often quite difficult, e.g., ref. [22] misidentified M. cuneata and M. inaequalis as M. schmidtii (pl. 37, Figures 5 and 6), a common mistake in general, especially when dealing with many taxa. The same applies to his M. barbadensis (pl. 35, Figure 9) which is really Mastogloia aspera; see above (reported as Orthoneis aspera by [29], p. 29, pl. 5, Figure 13). Its formal transference to Mastogloia is required. Also, the image in [22] pl. 36, Figures 1 and 2, is clearly not M. asperuloides; we identified it as M. elegans sensu [31].

Besides the above, original descriptions may not be without confusion. For example, Mastogloia fimbriata and M. clevei, although correctly shown by [29] as in the original record by [45], thereafter, both were mostly identified just as M. fimbriata, e.g., refs. [1,9,18,22,33]. This is because of the assertion that the difference in the form of partecta between these is due to variation in M. fimbriata specimens [18], with transitional forms that showed the need to consider a synonym [16]. However, Hustedt’s proposal was not as explicit and definitive. For instance, in M. fimbriata (Figure 22i–l), the outline is slightly polygonal, following the pattern of the elongated partecta, whereas in M. clevei (Figure 22a–d), it is smoothly rounded with twice as many pyramidal partecta. Thus, two taxa should be recognized for now until an adequate discriminant study is carried out, including the formal transference of Orthoneis clevei to Mastogloia.

Also, on the one hand, frequently confusions result when assigning an image to the description or taxonomic name, e.g., the authors of [31], when describing Mastogloia pseudolatecostata, refer to an image that resembles much more closely the M. latecostata originally described by [18]; the images of refs. [1,16] are very similar to each other and to the image of [31] of M. latecostata, while a M. ovum-paschale in [13] is actually the latter. On the other hand, distinctive traits are often overlooked; consequently, in other studies, specimens of M. pseudolatecostata have been placed as M. ovata or vice versa [9,20], bypassing the distinct inner margin of the partecta which is clearly notched in the former [31] and straight in the latter [18].

In another case, the Mastogloia biapiculata drawing in [43] allegedly taken from [28] does not agree with the figure in [18]. This is in part because many of the original descriptions refer to images that consist of drawings, such as in [18,28], that are not as reliable as expected. Nonetheless, in the last case, the fine photographic catalog by [43] is of great help, although it is not fully comprehensive. And finally, there is the case of Mastogloia jelineckii depicted with rhomboid specimens by [1,33], which is just one of several forms in [18], p. 544, Figure 977, that match our various specimens and those in [12], and in the original description by [46]. The form variation in this taxon does not seem to be caused by size differences inasmuch as the specimen in [1] is much larger than the one in [33] which calls expressly for inspection. The name spelling also needs revision (M. jelinecki; M. jelinickii; M. jelinekii; M. jelineckii). However, the problem had been solved in part [47] with the description of M. jelineckii var. extensa. In another case, the similarity and definitive differences between specimens of M. frickei from Guam and specimens from Florida were recently noticed [48], resulting in a new species, M. floridensis. Likewise, M. lucayensis, which had been formerly recorded as M. discontinua which it resembles but of which it does not fit the original description [34], was later cleared through adequate inspection [48], constituting an example of formal taxonomic work on which floristic studies like this one should be based. And, finally, M. sigillata, which has been misidentified as M. ovalis and by us as M. pernotata, was opportunely noticed by one reviewer who pointed out the proper reference [47], showing the need for a more exhaustive use of the literature, some of which is hard to come by. Communication between colleagues is also encouraged, which was quite helpful in the present study.

5. Conclusions

Because misidentifications are an important risk when handling many taxa, said problem should not discourage this type of study, but instead should serve as a motivation to pursue more reliable floristic references. In addition, the heterogeneous distribution of benthic diatoms in various substrata, seasonality, and connectivity is a factor that may cause gaps in the floristic information from any given locality. Thus, target samplings are required to complete said data to ensure that biogeographical and ecological models are precise for issuing conservation measures for the protection of natural areas.