Cryptic biodiversity of freshwater fish species in Bangladesh

PLOS One | https://doi.org/10.1371/journal.pone.0318982 April 28, 2025 9 / 18 PLOS One Cryptic biodiversity of freshwater fish formed clades with other Awaous sp. (Gobiidae) and demonstrated poor degrees of diver- gence (COI divergence 0.3%) (Fig 2). These specimens were collected from the Bogura and Faridpur districts which are linked with the rivers Jamuna and Padma. Lepidocephalichthys sp. (Cobitidae) collected from Netrokona (24°41’31.3“N 90°51’46.5”E), formed clades with other known sequences (MK572291, MK572294) and demonstrated15.50% COI divergence from its nearest congeners (Fig 1). Ophichthys sp.(Synbranchidae) demonstrated 7.7% genetic divergence from its near congeners (Fig 1). Erethistes sp. (Sisoridae), belonging to the genus Table 2. Possible cryptic species found in this study. Voucher Number Scientific Name (Family) Morphological Characteristics Total length (mm) Ratios Accession Number MHBSFMSTU Fish 3 Ailia sp. (Ailiidae) 1. Body elongate, deeply compressed and silvery in color 2. Four pairs of barbells present. 3. Adipose fin present. 4. Lateral line extends up to tip of the caudal fin. 78 TL:SL=7.8:7.2 TL:HB=7.8:1.3 TL:LBD=7.8:0.4 TL:HL=7.8:1.1 TL:ED=7.8:0.3 TL:PROL=7.8:0.2 TL:PTOL=7.8:0.6 LC823245 MHBSFMSTU Fish 6 Awaous sp. (Gobiidae) 1. Elongate, sub-cylindrical anteriorly, compressed posteriorly 2. Head obtusely convex and mouth little oblique 3. Spiny dorsal fin. 4. Opercule scaled. 99 TL:SL=9.9:8.2 TL:HB=9.9:1.9 TL:LBD=9.9:0.8 TL:HL=9.9:2.1 TL:ED=9.9:0.4 TL:PROL=9.9:0.7 TL:PTOL=9.9:1.0 LC823247 MHBSFMSTU Fish 17 Lepidocephal- ichthyssp.

(Cobitidae) 1. Caudal fin rounded; a light band extends from snout to caudal 2. Deep black spots present pectoral region and these spots become irregular at the base of caudal peduncle. 3. Small pelvic fin present. 69 TL:HB=6.9:1.2 TL:LBD=6.9:0.8 TL:HL=6.9:1.1 TL:ED=6.9:0.2 TL:PROL=6.9:0.4 TL:PTOL=6.9:1.2 LC823258 MHBSFMSTU Fish 56 Ophichthys sp. (Synbranchidae) 1. Body cylindrical, elongated with rounded abdomen. 2. Small eye and head not conspicuous. 3. Tail tapering and compressed. 4. Upper jaw longer, fleshy lips. 256 TL:LBD=25.5:1.3 TL:HL=25.5:0.5 TL:ED=25.5:0.1 TL:PROL=25.:0.3 LC823288 MHBSFMSTU Fish 83 Erethistes sp. (Sisoridae) 1. Head depressed and flattened ventrally. 2. Dorsal profile arched and ventral profile nearly horizontal. 3. Mouth small inferior and upper jaw little longer. 4. Four pairs of barbells and pectoral girdle present 57 TL:SL=5.7:4.7 TL:HB=5.7:1.1 TL:LBD=5.7:0.3 TL:HL=5.7:1.5 TL:ED=5.7:0.1 TL:PROL=5.7:0.8 TL:PTOL=5.7:0.6 LC823309 MHBSFMSTU Fish 100 Schisturasp. (Nemacheilidae) 1. Snout conical and abdomen rounded. 2. Eyes dorso-lateral. 3. Nostril in front of eye separated by valve. 4. Caudal fin weakly forked. 38 TL:SL=3.8:3.3 TL:HB=3.8:0.5 TL:LBD=3.8:0.1 TL:HL=3.8:0.6 TL:ED3.8:0.1 TL:PROL=3.8:0.2 TL:PTOL=3.8:0.3 LC823323 MHBSFMSTU Fish 126 Cynoglossus sp. (Cynoglossidae) 1. Body elongated, flat and tapering posterioly. 2. Eyes close together, on the left side of the body, upper one is advanced compared to lower one 3. Snout obtusely pointed. 4. Dorsal and anal fins confluent with caudal. 291 TL:SL=29.1:27.2 TL:HB=29.1:6.1

TL:LBD=29.1:0.2 TL:HL=3.8:4.8 TL:ED=29.1:0.5 TL:PROL=29.1:0.9 TL:PTOL=29.1:3.4 LC823337 https://doi.org/10.1371/journal.pone.0318982.t002