Amblyceps species

Darshan, Achom, Kachari, Akash, Dutta, Rashmi, Ganguly, Arijit & Das, Debangshu Narayan, 2016, Amblyceps waikhomi, a New Species of Catfish (Siluriformes: Amblycipitidae) from the Brahmaputra Drainage of Arunachal Pradesh, India, PLoS ONE (e 0147283) 11 (2), pp. 1-10 : 5-8

Amblyceps species have unossified pinnate-like rays (4–5 pinnate rays per lepidotrichium) on the anterior margins of the procurrent caudal-fin rays [ 2]. In the present study, we examined cleared and stained specimens of A. mangois , A. arunachalensis , A. apangi , and A. waikhomi and found the pinnate like rays (except A. apangi ) only on the distal half of the anterior margin of the segmented procurrent rays and unbranched principal rays. Ng and Kottelat [ 9] further reported the presence of pinnate like rays along the median caudal-fin rays of Amblyceps of the Indian subcontinent. This finding was confirmed by our observations on A. mangois ( Fig 4a; S 3 Fig) and A. arunachalensis ( Fig 4b), which exhibited strongly-developed ossified projections on the proximal lepidotrichia of the median caudal-fin rays. However, this feature was absent in A. waikhomi ( Fig 4c) and A. apangi . In A. arunachalensis these ossified projections were

hypural in A. waikhomi , not shown in figure). [Ph: parhypural, H: hypural plate, Dr: depression, E: epural, C: centrum Uprr: upper procurrent ray, Uspr: upper simple principal ray, Ubpr: upper branched principal ray, Sdp: strongly developed-projections, Lbpr: lower branched principal ray, Lspr: lower simple principal ray]

doi:10.1371/journal.pone.0147283.g004

observed between the two lowermost branched principal rays of the upper lobe, between the two uppermost branched principal rays of the lower lobe, and also between the lowermost and the uppermost rays of the upper and lower lobe of the caudal fin respectively. In the case of A. mangois , these projections were located only between the two lowermost branched rays of the upper lobe of caudal fin.

With the description of Amblyceps waikhomi , seven species of Amblyceps are now known from the Ganga-Brahmaputra River system viz. A. waikhomi , A. mangois , A. arunachalensis , A. tenuispinis , A. apangi , A. laticeps , and A. cerinum . Amblyceps species can be divided into two groups: one having a deeply forked caudal fin, and the other with an emarginate or truncate caudal fin. In addition to the characters mentioned in the diagnosis (specifically for the congeners in the first group, to which A. waikhomi belongs), A. waikhomi further differs from A. tenuispinis in having a shorter snout (23.4–27.2% HL vs. 33.6–43.3) and dorsal to adipose distance (17.0–21.3% SL vs. 23.9–34.0), a longer pectoral fin (16.8–19.0% SL vs. 15.1–16.6), and a deeper caudal peduncle (13.0–16.4% SL vs. 9.6–12.9); from A. arunachalensis in having a longer predorsal (25.7–30.6% SL vs. 22.5–23.2), prepelvic (48.3–50.3% SL vs. 45.1–45.9), prepectoral (19.2–23.0% SL vs. 18.2–19.8), and adipose-fin base (20.3–23.7% SL vs. 18.1–19.8) lengths and fewer pleural ribs (7 vs. 12); and from A. macropterus in having fewer vertebrae (34–35 vs. 37), a shorter adipose-fin base (20.3–23.7% SL vs. 28.3), and in lacking (vs. having) the strongly-developed projections on the proximal lepidotrichia of the median caudal-fin rays.

Amblyceps waikhomi can be further distinguished from A. carinatum by its shorter adipose-fin base length (20.3–23.7% SL vs. 37.5–44.6) and longer dorsal to adipose distance (17.0– 21.3% SL vs. 7.8–10.7); from A. tuberculatum by its shorter caudal peduncle length (15.5– 18.6% SL vs. 21.2–22.4), shorter dorsal to adipose distance (17.0–21.3% SL vs. 27.8–28.0), and incomplete (vs. complete) lateral line; from A. kurzii by its longer adipose-fin base (20.3–23.7% SL vs. 15.1–18.3), shorter dorsal to adipose distance (17.0–21.3% SL vs. 30.1–30.6), and deeper caudal peduncle (13.0–16.4% SL vs. 9.8–10.7).

Amblyceps waikhomi can be further distinguished from A. platycephalus by its fewer principal caudal-fin rays (17 vs. 20); from A. caecutiens in having a larger eye (6.7–7.5% HL vs. 2.0– 3.4) and shorter adipose-fin base (20.3–23.7% SL vs. 25.6–33.5); from A. protentum in having a longer prepelvic (48.3–50.3% SL vs. 42.8–47.8), prepectoral (19.2–23.0% SL vs. 15.9–18.3), and pectoral-fin (16.8–19.0% SL vs. 11.2–14.4) lengths, shorter and deeper caudal peduncle (length:15.5–18.6% SL vs. 20.0–25.6; depth: 13.0–16.4% SL vs. 8.0–10.3), shorter snout (23.4– 27.2% HL vs. 30.1–34.6), and shorter dorsal to adipose distance (17.0–21.3% SL vs. 26.3–32.2); and from A. variegatum by its uniformly brownish (vs. mottled) body coloration.