Aenigmachanna gollum, Britz & Anoop & Dahanukar & Raghavan, 2019

Britz, Ralf, Anoop, V. K., Dahanukar, Neelesh & Raghavan, Rajeev, 2019, The subterranean Aenigmachanna gollum, a new genus and species of snakehead (Teleostei: Channidae) from Kerala, South India, Zootaxa 4603 (2), pp. 377-388 : 379-382

Aenigmachanna gollum , new species

Figures 1–4

Holotype. BNHS FWF 966 , 90.2 mm SL, Oorakam , Malappuram, Kerala, India (11°03’52’’N and 76°01’00’’E) collected by Ajeer on 3 September 2018 from a paddy field.

Paratype. BNHS FWF 967 , 80.1 mm SL, same information as for holotype .

Diagnosis. Same as for the genus.

Description. Body cylindrical anteriorly to subcylindrical posteriorly and laterally compressed caudally, elongate, eel-like (Figs. 1,2), its length 8.8–9.0 times its depth, tapering towards tail, where body length is 22–23 times its depth. Head large, with eye situated in anterior third of head. Nasal organ large, about 1/10 head length, anterior naris at end of elongate nasal tube, posterior naris a large opening in front of eye. Mouth large ( Figs. 1-3 ), jaw length nearly 2/3 head length. Premaxilla with several rows of strong recurved teeth, larger near symphysis and smaller and only in single row more posteriorly. Vomer with up to 10 strong conical teeth, six prominent teeth on palatine arranged in a single row. Dentary with several rows of smaller but strong and recurved teeth on patch near symphysis, but with larger caniniform teeth further posteriorly. Five large antrorse teeth on posterior patch of parasphenoid. Fifteen elongate gill rakers on external aspect of first gill arch. Five branchiostegal rays. Head lateral-line pore system with two nasal pores, seven circumorbital pores, two frontal pores, four dentary and one anguloarticular pore, four preopercular pores, one pterotic pore, two extrascapular pores, one posttemporal pore. No pored lateral line scales on body ( Fig. 4 ). Dorsal fin long (Figs. 1,2), nearly three-quarters of standard length, originating at first quarter of body, extending to caudal peduncle, almost reaching caudal fin. Anal fin long (Figs. 1,2), more than half of standard length, originating slightly behind first half of body and in posterior extension mirroring dorsal fin by extending almost up to caudal fin. Caudal fin ovoid ( Fig. 1 ). Pectoral fin large, its posterior margin when adpressed reaching beneath origin of eighth dorsal-fin ray (Fig. 1,2). Pelvic fin absent. Morphometric information is presented in Table 1 .

Large scales covering top of head, small scales on postorbital area up to opercle (Figs. 2,3). 29 (10 + 19) predorsal scales. Comparatively small scales on anterior postcranial portion of body arranged slightly irregularly, with larger regularly arranged scales from level of anterior dorsal fin base posteriorly. 83–85 scales in lateral series plus 4 scales on caudal-fin base. 13 transverse scale rows.

Dorsal fin with 56–57 rays, anal fin with 43–44 rays, caudal fin with 7+7 principal caudal-fin rays and 1 dorsal and 1 ventral procurrent ray. Pectoral fin with 12 rays. Vertebrae 64.

Unfortunately, due to the rarity of the material we are unable to comment further on internal features.

Colouration. In life ( Fig. 1 ), entire body from head to caudal peduncle uniformly brown dorsally and mostly brown laterally, but with ventral side of head uniformly lighter beige without melanophores; abdominal area mostly beige with scattered dark spots. Scales covering cheek and opercular region exhibiting reflective, silvery areas resulting in a marbled impression. Body at level of individual scales with characteristic colouration ( Figs. 1–4 ): each scale in dorsal half of body with darker brown anterior crescentic area, light brown to yellowish, narrow and crescentic, elongate marking in middle of scales and dark brown posterior blotch-like marking; scales in ventral half of body with light brown to yellowish crescentic mark becoming progressively wider ventrally, in ventrolateral scales entirely replacing anterior dark crescentic area; most scales in ventral abdominal region uniform beige with few brown scales interspersed, forming scattered spots, some of which are arranged in a midventral streak from isthmus to anus. Fin membranes transparent and fin rays light brown with whitish distal tips forming narrow whitish dorsal, caudal, and anal-fin margins. In preservative, colour pattern as above, but reflective silvery area on cheek scales, light brown area on body scales, and beige scales on ventral abdominal body whitish.

Distribution. Aenigmachanna gollum is so far known only from the type locality (Figs. 5,6), a paddy field, but a third specimen has been reported from a well at the Village of Peringara near Tiruvalla (9°22’33” N and 76°33’00” E), approximately 250 km south of the type locality.

Etymology. Named after Gollum, a character from J. R. R. Tolkien’s books ‘The Hobbit’ and ‘The Lord of the Rings’, a creature that went underground and during its subterranean life changed its morphological features. A noun in apposition. We propose the common name Gollum snakehead for this species.

Genetic analysis. Aenigmachanna showed high genetic divergence, with minimum and maximum raw genetic distances ranging from 15.8–24.2% in cox1 for the species of Channa , and with 20.4–22.2% in cox1 for species of Parachanna . Best partition scheme for the data was TNe+I+G4 for first two codon positions of cox1 (BIC = 18328.676, lnL = -8606.791, df=172) and TN+ASC+G4 for third codon position of cox1 (BIC = 18714.922, lnL = -8511.415, df=261). The maximum likelihood tree based on the best partition scheme ( Fig. 7 ) showed a deep divergence between Aenigmachanna gollum and the clades of Parachanna and Channa within Channoidei. Additional studies are needed to place Aenigmachanna gollum with confidence into a phylogenetic framework and to decide whether it is the sister group of Parachanna , of Channa or even of Parachanna plus Channa , as in the cox1 analysis ( Fig. 7 ).

Figures

FIGURE 1. Aenigmachanna gollum, alive, holotype, BNHS FWF 966, 90.2 mm SL, Oorakam, Malappuram, Kerala, India.

FIGURE 2. Aenigmachanna gollum, preserved, holotype, BNHS FWF 966, 90.2 mm SL, Oorakam, Malappuram, Kerala, India in lateral (A), dorsal (B), and ventral view (C).

FIGURE 3. Aenigmachanna gollum, preserved, paratype, BNHS FWF 967, 80.1 mm SL, Oorakam, Malappuram, Kerala, India, head in lateral (A), dorsal (B), and ventral view (C), sensory pores of head lateral-line marked by black dots. Abbreviations: aa anguloarticular pore; co circumorbital pores; d dentary pores; esc extrascapular pores; f frontal pores; po preopercular pores; pt posttemporal pores; pto pterotic pores.

FIGURE 4. Aenigmachanna gollum, preserved, holotype, BNHS FWF 966, 90.2 mm SL, details of body pigmentation. A, anterior body behind pectoral fin; B, posterior body at middle of caudal peduncle. Note increase in size of pigment free area at bases of scales in B.

FIGURE 7. Maximum likelihood tree based on mitochondrial cox1 gene using best partition scheme for nucleotide substitution pattern. Anabantiform fishes of the genera Badis and Nandus were used as outgroups. Values along the nodes are percentage bootstrap values based on 1000 iterations.

Tables

TABLE 1. Selected measurements in mm of the holotype and paratype of Aenigmachanna gollum.

	Holotype	Paratype
	BNHS FWF 966	BNHS FWF 967
Standard length	90.2	80.1
Head length	19.5	16.6
Head depth	9.0	8.0
Head width	9.3	7.2
Body depth	10.5	9.3
Body width	6.8	5.3
Predorsal length	24.2	21.3
Preanal length	39.1	34.6
Prepectoral length	19.2	16.1
Dorsal-fin base length	64.1	57.2
Anal-fin base length	49.2	43.5
Pectoral-fin length	12.9	10.4
Caudal peduncle length	1.9	1.7
Caudal peduncle depth	4.1	3.5
Snout length	3.9	3.0
Eye diameter	2.6	2.1
Preorbital depth	4.6	3.7
Postorbital depth	6.4	5.7
Interorbital width	4.4	3.6
Upper jaw length	11.9	10.1