Clarias rennyae, Low & Ng & Tan, 2022

Low, Bi Wei, Ng, Heok Hee & Tan, Heok Hui, 2022, Two new species of blackwater catfishes (Siluriformes: Siluridae and Clariidae) from the Natuna Archipelago, Indonesia, Raffles Bulletin of Zoology 70, pp. 385-396 : 389-393

Clarias rennyae , new species

( Figs. 3 , 4 )

Clarias leiacanthus (non Bleeker, 1851) – Tan & Lim, 2004: 109 (part).

Holotype. MZB 17237, 108.0 mm SL; Pulau Natuna Besar: blackwater tributary of Sungai Sekeram (3°50′28.6″N 108°03′47.1″E) (W13); D. Wowor et al.; 18 March 2002.

Paratypes. ZRC 62074, 157.9 mm SL ; ZRC 62075, 115.1 mm SL ; MZB 17238, 84.6 mm SL; Pulau Natuna Besar: blackwater tributary of Sungai Sekeram (3°50′28.6″N 108°03′47.1″E) (W12); D. Wowor et al.; 18 March 2002 .

Diagnosis. Clarias rennyae is distinguished from all other Southeast Asian congeners by the following suite of characters: anal-fin length 51.3–56.3% SL, body depth at anus 13.1–13.7% SL, head width 17.9–18.9% SL, distance between occipital process and dorsal-fin origin 6.8–8.9% SL, frontal fontanelle length 17.7–22.5% HL, anterior edge of pectoral-fin spine with 19–31 irregular tiny asperities, and 65–68 total vertebrae.

Description. General body form as in Fig. 3 . Morphometric measurements are shown in Table 2. Body cylindrical, tapering towards caudal peduncle. Skin smooth. Lateral line median, starting just behind operculum and ending at caudal peduncle. Openings to secondary sensory canals arranged regularly on upper flanks of the body in vertical branches above the lateral line, visible as 12–17 vertical rows of 2–6 tiny white spots.

Head depressed, dorsal profile slightly convex, egg-shaped when viewed from the top, snout narrow. Occipital process narrow; round or slightly triangular with rounded tip. Frontal fontanelle around twice (1.9–2.4×) as long as wide, with anterior margin reaching imaginary line between orbits. Occipital fontanelles oval, around 1.5 times as long as wide; anterior margin slightly before pectoral fin insertion. Four pairs of barbels with fleshy base, tapering towards the tips. Mouth subterminal with fleshy lips. Eyes small and subcutaneous. First branchial arch with 15 (1), 16 (1), 20* (1) gill rakers.

Dorsal fin with long base, spanning posterior four-fifths of body, with 72* (2) or 73 (2) rays. Anal fin with long base, spanning posterior three-quarters of body, with 58 (1), 59* (1), 60 (1), or 64 (1) rays. Posterior extremities of dorsal- and anal-fin base extending beyond anterior margin of the hypural complex. Caudal fin rounded, with 8+7 (2) or 9+7* (2) rays. Dorsal, anal and caudal fins covered with thick layer of skin. Pectoral fin with a small spine, and 8 (1) or 9* (3) rays; anterior edge of pectoral-fin spine with 19* (1), 24 (1), 27 (1), or 31 (1) irregular tiny pointed asperities at proximal end, distal end smooth. Pelvic fin with I,5 (4) rays, originating at anterior third of body.

Vertebral formula: 20 + 45 = 65 (1), 21 + 45 = 66* (2), 21 + 47 = 68 (1).

Preserved colouration: Body dark brown on dorsum and sides, fading to cream on the underside. Dorsal, anal, and caudal fins dark brown, distal margins very slightly hyaline. Pectoral and pelvic fins light brown, with hyaline inter-radial membranes.

Distribution and habitat notes. Clarias rennyae , new species, is only known from Pulau Natuna Besar of the Natuna Archipelago, Indonesia, where it occurs in heath-peat swamp forest habitat with acidic (pH ~3.4), tannin-stained black waters. Syntopic species as listed above.

A second species of walking catfish we tentatively identify as C. leiacanthus , was also collected from Pulau Natuna Besar. Both species are not syntopic, however, with C. rennyae only recorded from blackwater streams on the western side of the island, whereas C. leiacanthus was only caught from a rocky clearwater stream (near a waterfall habitat) draining the eastern slope of the island. Additionally, C. rennyae can be distinguished from C. leiacanthus by a wider head (head width 17.9–18.9% SL vs. 17.2–17.9% SL in C. leiacanthus ) and a narrower suborbital snout width (50.4–53.8% HL vs. 54.5–55.4% HL in C. leiacanthus ), giving the appearance of a more tapered snout when viewed dorsally, as well as falcate pectoral fins (vs. rounded pectoral fins in C. leiacanthus ) ( Fig. 4 ).

Etymology. The species is named for the late Renny Kurnia Hadiaty (21 August 1960 – 30 January 2019), a dear friend and colleague who passed away too soon. Renny was a leading expert on the taxonomy of Indonesian freshwater fishes, and was Curator of Fishes and Head of the Ichthyology Laboratory at the Museum Zoologicum Bogoriense, Lembaga Ilmu Pengetahuan Indonesia (Indonesian Institute of Sciences).

Remarks. Twenty-one Southeast Asian Clarias species are currently recognised ( Ng & Kottelat, 2014), viz. C. batrachus (Linnaeus, 1758) ; C. fuscus (La Cepède, 1803) ; C. nieuhofii Valenciennes , in Cuvier & Valenciennes, 1840; C. meladerma Bleeker, 1846 ; C. leiacanthus Bleeker, 1851 ; C. macrocephalus Günther, 1864 ; C. olivaceus Fowler, 1904 ; C. batu Lim & Ng, 1999 ; C. anfractus Ng, 1999 ; C. planiceps Ng, 1999 ; C. microstomus Ng, 2001 ; C. intermedius Teugels, Sudarto & Pouyaud, 2001 ; C. insolitus Ng, 2003 ; C. nigricans Ng, 2003 ; C. kapuasensis Sudarto, Teugels & Pouyaud, 2003 ; C. pseudoleiacanthus Sudarto, Teugels & Pouyaud, 2003 ; C. sulcatus Ng, 2004 ; C. pseudonieuhofii Sudarto, Pouyaud & Teugels, 2004 ; C. gracilentus Ng, Dang & Nguyen, 2011 ; C. microspilus Ng & Hadiaty, 2011 ; and C. serniosus Ng & Kottelat, 2014 . These can be broadly divided into two artificial species groups based on their morphology, with the more elongate/anguilliform species (81–101 dorsal fin rays, 74–84 total vertebrae) being placed into the C. nieuhofii species group, and the less elongate species (53–77 dorsal fin rays, 54–71 total vertebrae) being placed into the C. batrachus species group ( Sudarto et al., 2003; Ng et al., 2011). Presently, the C. nieuhofii species group comprises C. nieuhofii , C. nigricans , C. pseudonieuhofii , and C. gracilentus , whereas the C. batrachus species group comprises the remaining 17 Southeast Asian species. Clarias rennyae , with 72–73 dorsal fin rays and 65–68 total vertebrae, falls into the C. batrachus species group.

Clarias rennyae differs from C. anfractus in having a longer frontal fontanelle (18–23% HL vs. 10–16) and a pectoral spine with a smooth anterior margin along distal two-thirds and tiny pointed asperities along proximal one-third (vs. irregular outline along entire anterior margin), from C. batrachus in having a longer anal fin (51.3–56.3% SL vs. 43.3–50.7) and more vertebrae (65–68 vs. 54–61), and from C. batu in having a shorter distance between the occipital process tip and dorsal fin origin (6.8–8.9% SL vs. 9.9–11.8), a deeper body (depth at anus 13.1–13.7% SL vs. 9.0–11.4) and a longer frontal fontanelle (18–23% HL vs. 13–16). It can be differentiated from C. fuscus by a greater distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 4.8–6.5) and more vertebrae (65–68 vs. 53–57), from C. gracilentus by a shorter anal fin (51.3–56.3% SL vs. 60.0–63.9), a deeper body (depth at anus 13.1–13.7% SL vs. 8.2–11.7), a wider head (17.9–18.9% SL vs. 11.9–12.9) and fewer vertebrae (65–68 vs. 80–84), and from C. insolitus by a shorter distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 10.3–12.4), a deeper body (depth at anus 13.1–13.7% SL vs. 9.9–11.5), a wider head (17.9–18.9% SL vs. 14.0–15.6) and a pectoral spine with tiny asperities on the anterior edge (vs. prominent serrations). Clarias rennyae can be distinguished from C. intermedius by a greater distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 1.8–3.8), a more slender body (depth at anus 13.1–13.7% SL vs. 14.0–18.1) and more vertebrae (65–68 vs. 61), from C. kapuasensis by a more slender body (depth at anus 13.1–13.7% SL vs. 14.4–18.0) and a pectoral spine with tiny asperities on the anterior edge (vs. a smooth edge), and from C. leiacanthus by a wider head (17.9–18.9% SL vs. 17.2–17.9) and a longer frontal fontanelle (18–23% HL vs. 9–16). It further differs from C. macrocephalus in having a longer anal fin (51.3–56.3% SL vs. 46.4–50.2), a greater distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 2.2–5.1), a more slender body (depth at anus 13.1–13.7% SL vs. 16.8–19.2) and a greater number of vertebrae (65–68 vs. 57–61), from C. meladerma in having a greater distance between the occipital process tip and dorsal fin origin (6.8–8.9% SL vs. 2.1–4.8) and a pectoral spine with tiny asperities on the anterior edge (vs. prominent serrations), and from C. microspilus in having a longer anal fin (51.3–56.3% SL vs. 47.4–50.5), a more slender body (depth at anus 13.1–13.7% SL vs. 14.9–18.9), a longer frontal fontanelle (18–23% HL vs. 12–17), more vertebrae (65–68 vs. 60–62), and a pectoral spine with tiny asperities (vs. prominent serrations).

Clarias rennyae is further distinguished from C. microstomus by a shorter distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 12.8–13.1), a wider head (17.9–18.9% SL vs. 16.2–17.2), a longer frontal fontanelle (17.7–22.5% HL vs. 8.3–10.9), a greater number of vertebrae (65–68 vs. 61–64) and a pectoral spine with tiny asperities on the anterior edge (vs. a smooth edge), from C. nieuhofii by a shorter anal fin (51.3–56.3% SL vs. 59.7–66.8) and a wider head (17.9–18.9% SL vs. 11.7–15.8), and from C. nigricans by a shorter anal fin (51.3–56.3% SL vs. 59.6–63.8), a deeper body (depth at anus 13.1–13.7% SL vs. 10.4–13.0), a wider head (17.9–18.9% SL vs. 11.7–12.3), a longer frontal fontanelle (18–23% HL vs. 9–14), fewer vertebrae (65–68 vs. 76–83) and a pectoral spine with tiny asperities on the anterior edge (vs. a few large serrations). It is further differentiated from C. olivaceus by a longer frontal fontanelle (18–23% HL vs. 10–17), a greater number of vertebrae (65–68 vs. 60–63) and a pectoral spine with tiny asperities (vs. prominent serrations), from C. planiceps by a wider head (17.9–18.9% SL vs. 15.7–17.6), a longer frontal fontanelle (18–23% HL vs. 11–18) and a pectoral spine with tiny asperities on the anterior edge (vs. prominent serrations), and from C. pseudoleiacanthus by a greater distance between the occipital process and dorsal fin origin (6.8–8.9% SL vs. 4.5–5.6), a more slender body (depth at anus 13.1–13.7% SL vs. 15.7–18.2) and a pectoral spine with tiny asperities on the anterior edge (vs. a smooth edge). Lastly, C. rennyae differs from C. pseudonieuhofii in having a deeper body (13.1–13.7% SL vs. 11.0–12.9), a wider head (17.9–18.9% SL vs. 12.7–14.3) and a longer frontal fontanelle (18–23% HL vs. 10–15), from C. serniosus in having a longer anal fin (51.3–56.3% SL vs. 46.2–50.1), a more slender body (13.1–13.7% SL vs. 16.2–16.5), more vertebrae (65–68 vs. 57) and a pectoral spine with tiny asperities on the anterior edge (vs. a smooth edge), and from C. sulcatus in having more vertebrae (65–68 vs. 62–64).

Comparative material. Clarias batrachus: ZRC 2585 (4), 170.3–247 mm SL; Tjilebut, West Java. – MZB 15517 (1), 187.5 mm SL; S. Cipayang, Gn. Ciremai Timur; Kuningan, Jawa Barat. – MZB 20621 (1), 199 mm SL; Situ Manggabolong, kel Srengseng Sawah , kec. Jagakarsa , kotip Jakarta Selatan. – MZB 1270 (1), 167.2 mm SL; Java: Ciangke, Semplak, Bogor. – MZB 1457 (1), 226.1 mm SL; Caringin, Citarik, Pelabuan Ratu, West Java. – MZB uncat. (1), 195 mm SL; Batavia. – MZB 10070 (1), 158 mm SL; S. Cimanuk, Kp. Sipon, Ds. Bayongbong, Garut, Jawa Barat. – MZB 4033 (2), 200.5–218 mm SL; Rawa Pening, JawaTengah. – MZB 4190 (1), 224.4 mm SL; Ambarawa, Jawa Tengah. – MZB 2447 (1), 190.8 mm SL; Telaga Mengen, Womosobo, Jawa-Tengah. – MZB 1237 (2), 221–221.9 mm SL; S. Blawi, 10 km utara Lamongan. – MZB 1451 (3), 173.9–192.7 mm SL; Java: Riv. Bersini, Gemuk Mas, Jembero, East Java. – MZB 1358 (1), 170 mm SL; East Java: Riv. Kuwayangan, Ngantang-Malang.

Clarias fuscus: Data from Arai & Hirano (1974).

Clarias intermedius: Data from Teugels et al. (2001).

Clarias kapuasensis: Data from Sudarto et al. (2003).

Clarias leiacanthus: ZRC 37758 (10), 49.1–129.5 mm SL; Borneo: Sarawak, Bako National Park, Ulu Assam, stream I. – ZRC 39744 (12), 155.0– 326.7 mm SL; Borneo: Sarawak, Serian market, from Batang Kerang. – ZRC 40551 (3), 191.7–206.0 mm SL; Borneo: Sarawak, Miri, from pasar malam next to bus station, purportedly from Sungai Bakung. – ZRC 42697 (8), 20.4–95.8 mm SL; Brunei: Belait district, 2 streams near old padi fields ca. 200 m downstream of Kampung Melilas (4°15′24.3″N, 114°39′40.2″E). – ZRC 40131 (1), 97.7mm SL; Java : Java Barat , Bogor , tributary of Cipinang Gading. – ZRC 39105 (4), 37.0–150.0 mm SL; Sumatra : Riau , stream near Pangkalankasai , 43 km from Rengat on Rengat–Jambi road. – ZRC 41523 (5), 175.1–255.7 mm SL; Sumatra : Jambi , Angso Duo market. – ZRC 11678–11679 (2), 109.8–202.9 mm SL; Singapore: Nee Soon Swamp Forest . – ZRC 39985 (5), 23.8–177.5 mm SL; Malaysia: Johor, Pontian , Kampung Parit Tekong. – ZRC 39961 (2), 56.9–120.7 mm SL; Malaysia: Johor, 3–4 km towards Kukup after Sri Bunian turnoff. – ZRC 2596 (2), 93.4–109.5 mm SL; Malaysia: Pahang, Kuala Tahan. – ZRC 25669 (1), 124.8 mm SL; Malaysia: Pahang, 69 km on Mersing–Kuantan road. – ZRC uncat. (2), 133.8–214.1 mm SL; Pulau Natuna Besar : stream under last wooden bridge towards waterfall from Ranai (DW0207).

Clarias macrocephalus: ZRC 30465 (1), 197.2 mm SL; Malaysia: Pahang, Sg. Jelai. – ZRC uncat. (1), 280 mm TL; Malaysia: Perak, Sg. Sungkai Mati. – ZRC uncat. (1), 205 mm SL; Thailand: Phuket province, Thalang district. – MARNM 5887 (1), 139.5 mm SL; Thailand: Chiang Rai province, Teung district, Ing River . Additional data from Teugels et al. (1999).

Clarias meladerma: ZRC uncat. (1), 160 mm TL; Malaysia: Langkawi, stream along Persiaran Langkawi Indah 12, near intersection with Langkawi Highway.

Clarias nieuhofii: Data from Sudarto et al. (2004).

Clarias pseudoleiacanthus: Data from Sudarto et al. (2003). Clarias pseudonieuhofii: Data from Sudarto et al. (2004).

For a list of additional material examined, see Ng (1999, 2001, 2003a, b, 2004), Lim & Ng (1999), Tan & Ng (2000), Ng & Hadiaty (2011), Ng et al. (2011), Ng & Kottelat (2008, 2014).

Figures

Fig. 3. Clarias rennyae, new species, holotype, MZB 17237, 108 mm SL; Indonesia: Natuna Islands, Pulau Natuna Besar (composite of dorsal, lateral, and ventral views).

Fig. 4. Dorsal views showing differences in head and pectoral fin morphology between A) C. rennyae, new species, holotype, MZB 17237, 108 mm SL, Pulau Natuna Besar, and B) C. leiacanthus, ZRC uncat., 133.8 mm SL, Pulau Natuna Besar (not to scale).