Ichthyophis benjii, Lalremsanga & Purkayastha & Biakzuala & Vabeiryureilai & Muansanga & Hmar, 2021

Lalremsanga, Hmar Tlawmte, Purkayastha, Jayaditya, Biakzuala, Lal, Vabeiryureilai, Mathipi, Muansanga, Lal & Hmar, Gospel Zothanmawia, 2021, A new striped species of Ichthyophis Fitzinger, 1826 (Amphibia: Gymnophiona: Ichthyophiidae) from Mizoram, northeast India, Amphibian & Reptile Conservation (e 288) 15 (2), pp. 198-209 : 199-205

Ichthyophis benjii sp. nov.

Figs. 1–5 ; Tables 1–3 .

urn:lsid:zoobank.org:act:41A96569-4F97-40CD-A47C-54F9A9E70D1C

Holotype: MZMU 1479 , an adult male, collected by Lal Biakzuala on 12 August 2019, from a soil pit of ca. 1.5 m depth for a pillar at a construction site at Durtlang (23°47’6.58”N, 92°43’31.74”E; 1,233 m asl), Aizawl District , Mizoram, India ( Fig. 1 ).

Paratypes (n = 4): MZMU 1462 , adult male, collected by Gospel Zothanmawiia Hmar on 15 July 2019 from a water drain at Chhinga veng (23°44’4.99”N, 92°43’14.04”E; 991 m asl), Aizawl , Mizoram, India ; MZMU 1481 , adult male, collected by Lal Biakzuala on 28 August 2019 from the roadside at Tanhril (23°44’4.07”N, 92°40’34.90”E; 821 m asl), Aizawl , Mizoram, India ; MZMU 1513 , a road-killed adult female, collected by Lal Biakzuala on 4 September 2019 from Lianchhiari road inside Mizoram University Campus (23°44’12.01”N, 92°40’3.45”E; 857 m asl), Aizawl , Mizoram, India ; MZMU 2025 , an adult female, collected from a soil pit of ca. 2 m depth by Lalengzuala Tochhawng on 26 October 2020 from Durtlang Gosen veng (23°47’4.55”N, 92°43’44.08”E; 1,230 m asl), Aizawl , Mizoram, India .

Diagnosis. Ichthyophis with narrow (W/S> 5) irregular faint lateral yellow stripes extending from immediately behind CMs to the level of the posterior of vent, not contacting the disc, barely or not visible on the collars ventrally, patchy in the trunk region; known to attain lengths greater than 400 mm, 26 <L/W <30; head more V-shaped than U-shaped in dorsal view, short (L/H> 24); TAs more than twice as far from nares as from eyes ( TN /TE> 2); without distinctive moustache-like stripes between snout tip and TAs; and C2 noticeably longer than C1. Ichthyophis benjii sp. nov. differs from all other striped congeners in having a markedly less prominent pale yellowish lateral stripe, bordered by a darker ventrolateral longitudinal stripe immediately above the pale venter on each side. It can be differentiated from I. tricolor and I. multicolor in having much higher AGs of 385–422 and 383–423 counted dorsally and ventrally, respectively.

Description of the holotype. Morphometric and meristic data are given in Table 1 . Mostly good condition; longitudinal incisions mid-ventrally 50 mm anterior to the third annulus from the disc and ca. 30 mm approximately one-fourth along anterior body; small depressed scar (5.5 mm long x 2 mm wide) on the mid-dorsal surface of the head slightly posterior to eyes; small subvertical split approximately halfway along left lower lip; patches of stratum corneum scattered throughout. Total length 414 mm, girth maximal throughout midbody, increasing very gradually over first 70 mm, decreasing less gradually over last ca. 40 mm; L/ W 29.2, width at mid-body slightly more than 3% of total length (W/L 0.03). Maximum width of stripe at midbody is less than 1% of total length (S/L 0.0068) and 20.9% of the width at midbody (S/ W 0.20). Head and nuchal region dorsoventrally compressed; ventral surface slightly flattened in the trunk region. Head somewhat more V- than U-shaped in dorsal view. In lateral view, distance of CM from top of head is more than twice the distance from bottom of head (top of head to CM 5 mm, bottom of head to CM 2.3 mm). Eye slightly closer to the lip than to the top of the head in lateral view (top of head to eye 1.7 mm; eye to lip 1.3 mm) surrounded by a narrow whitish ring. Eye slightly elevated above adjacent skin, larger than naris (E 0.4 mm; N 0.3 mm) but smaller than TP (0.65 mm). TAs more than twice as far from nares as from eyes (TA-E/ TA-N 0.47). Naris above the level of AM; equidistant from top and bottom of head in lateral view. Tongue V-shaped, strongly plicate posteriorly, margin overlying only posterior-most IMs. Teeth slender, inwardly curved with sharp and pointed tips (PMs 37; VPs 37; OMs 35; IMs 31 including empty sockets). Choanae elongated along the axis of the head, distance between them four times each of their greatest widths. Collar region broader than adjacent head. Laterally, C2 slightly longer than C1. NG1 complete dorsally. Four anteromedially flexed, evenly spaced TGs on C2 dorsally. Dorsally, AGs are mostly complete, 401 in number, and those on first onethird of the body curve anteromedially. The first three AGs widely incomplete on ventral surface. A total of 397 AGs present ventrally; AGs on first four-fifths of the body curved posteromedially, decreasing posteriorly, more or less orthoplicate by 34 th AG anterior to vent; five AGs interrupted by the disc on both left and right; six more midventrally complete AGs on tail. Tail short (4.7 mm), shorter than ST-TA (5.7 mm), tapered and downturned towards tip. The last few annuli shorter. The terminus ends in a short (1.3 mm) cap, approximately the length of the three preceding tail annuli or two body annuli. Margins of longitudinally slit vent slightly elevated, formed by ten main denticulations, five on each side, with some irregular subdivisions. No associated papillae. Vertebrae 124 in number.

In preservation, dorsum brownish grey, more chocolate brownish where stratum corneum absent. Venter much paler brownish grey. A distinct pale spot, longer than wide (5 x 4 mm), forms a disc around the vent. Narrow (W/ S 5.1), irregular, faint yellowish lateral stripe on each side; unbroken from slightly above and in front of CMs to the second-to-last annulus, fading gradually on first annulus behind the vent; wider and more prominent behind CMs and C1, but almost broken on C2, not visible ventrally on collars, not connecting with or curving towards disc. Immediately below each lateral stripe, running from C2 to the level anterior to the vent, a mostly slightly indistinguishable narrower brown line, a little paler than the dorsal color, with a gradual but rapid transition to a much paler tan color that predominates on the venter, but becomes gradually darker in the posterior region. Narrow, pale lines along upper lower jaw and lower upper jaw. Tentacular papillus and ST pale. Eye covered by translucent skin, surrounded by a narrow whitish ring. In life, dorsum dark brownish grey, venter reddish grey, narrow irregular faint lateral stripes dull-yellow. A pale yellowish, thin midventral line extends from level with the anterior of the CMs across C1 to NG2. AGs appear mostly paler than adjacent skin except in the region where crossing faint lateral yellowish stripes, especially on venter. Tail tip pale.

Variation. Morphometric and meristic data for the type series are given in Table 1 . The specimens generally resemble the holotype except for features highlighted here. Specimens MZMU 1462 and MZMU 1513 much larger, with total lengths of 473 mm and 459 mm, respectively. MZMU 1462 , MZMU 1481 , MZMU 1513 , and MZMU 2025 less elongate, with lower values for L/W (26.1–26.3). MZMU 1481 has the highest dorsal AG count (422) and also is the only specimen to have more ventral AGs (423) than dorsal AGs. MZMU 1481 and MZMU 1513 lack transverse grooves on C2. MZMU 1513 has many fewer OMs (29), possibly due to damage on the lower jaw. W/ S 5.1–5.4 in specimens less than 450 mm in length; W/ S 5.5–5.6 in larger specimens, indicating that the width of the stripe does not grow as fast as the width of the body. Similar allometries are apparent in the relative lengths of the head (L/H) and of the tail (L/ T), and the tail appears to lengthen more slowly than the head. AGs on the tail curve anteromedially in MZMU 1462 but are orthoplicate in other specimens. Radiographs show 118 to 124 vertebrae with no correlation with total length.

Distribution and natural history. All the specimens were collected from a secondary forested area of Aizawl Municipal Council area, Aizawl District in Mizoram at ca. 821–1,233 m asl during the mid- to late monsoon season from the months of July to October. All of the specimens were found on the surface. Three of the paratypes were encountered and collected at night from the roadside, while the holotype and one paratype ( MZMU 2025) were likely trapped during night time in the pit for a pillar basement in the heart of the residential area at the Durtlang locality. During this period, surface activity appears to be nocturnal. This species is more rarely encountered than other sympatric Ichthyophis species; a thorough day-and-night survey of the herpetofauna in this area conducted from 2015 to date has yielded only the five individuals described here. A small freshwater shrimp was recovered from inside the mouth of MZMU 1462, indicating that prey items include freshwater macroarthropods. Other amphibians found in the same macrohabitat during the collection period include the caecilians Ichthyophis khumhzi , I. moustakius , and the recently confirmed I. multicolor ( Lalremsanga et al. 2021) , and frogs Duttaphrynus melanostictus, Fejervarya multistriata, Minnervarya asmati, Megophrys serchhipii, Polypedates teraiensis, Zhangixalus suffry , and Zhangixalus smaragdinus .

Etymology. The species epithet “ benjii ” is dedicated in memory of Benjamin Lalremsanga (1988–2020, nephew of Hmar Tlawmte Lalremsanga) who used to actively assist the author(s) in their herpetofaunal surveys.

Suggested English common name: Benji’s Caecilian

Comparison. The comparison is based on the examination of specimens, papers with original descriptions, and review articles ( Taylor 1960, 1965, 1968, 1973; Pillai 1986; Pillai and Ravichandran 1999; Wilkinson et al. 2007; Kamei et al. 2009; Mathew and Sen 2009; Bhatta et al. 2011; Nishikawa et al. 2013; Wilkinson et al. 2014; Kamei and Biju 2016). Ichthyophis benji sp. nov. differs from all the other known congeners by the following criteria. Ichthyophis benji sp. nov. has a distinct dorsolateral stripe which is absent in I. acuminatus , I. billitonensis , I. cardamomensis , I. catlocensis , I. chaloensis , I. dulitensis , I. glandulosus , I. javanicus , I. lakimi , I. laosensis , I. larutensis , I. monochrous , I. orthoplicatus , I. sikkimenis , I. singaporensis , I. sumatranus , I. weberi , and I. youngorum ; and by having a higher number of annular groves (385–422) vs. less than 380 annular groves in I. asplenius (247–270), I. atricollaris (275–310), I. beddomei (240), I. biangularis (330–333), I. davidi (321–336), I. elongates (274–290), I. hypocyaneus (314–316), I. kodaguensis (276–305), I. longicephalus (348), I. mindanaoensis (287–326), I. nguyenorum (212–218), I. paucisulcus (259), I. pauliI (335), I. pseudangularis (269–271), I. supachaii (322), and I. tricolor (245–284). Ichthyophis benji sp. nov. has a higher number of vertebrae (118–121) than I. humphreyi (112) and I. mindanaoensis (110–116). Ichthyophis benji sp. nov. has L/W 26–30 vs. L/W 19– 21 in I. glutinosus . In life, I. benji sp. nov. has a dark brownish grey dorsum and a pale reddish venter vs. both dorsum and venter black in color in I. nigroflavus . Splenial teeth are present in I. benji sp. nov. vs. being absent in I. paucidentulus . In addition to these, no single character serves to distinguish I. benjii sp. nov. from all other Ichthyophis , but combinations of diagnostic characters serve to distinguish it from any other species. In particular, with the exception of I. khumhzi and I. longicephalus , all other south Asian striped Ichthyophis ( I. beddomei , I. garoensis , I. glutinosus , I. kodaguensis , I. pseudangularis , and I. tricolor ) differ from I. benjii sp. nov. in having TAs less than twice as far from nares as from eyes ( TN /TE <2). All southeast Asian striped Ichthyophis ( I. attricolaris , I. biangularis , I. bannanicus , I. bernisi , I. elongatus , I. humphreyi , I. hypocyaneus , I. kohtaoensis , I. paucisulcus , and I. supachaii ) differ from I. benjii sp. nov. in having markedly fewer IMs than dentary teeth. Ichthyophis longicephalus differs from I. benjii sp. nov. in head shape and size (L/H <18 vs.> 25, respectively), and in having subequal collars and a stripe that extends onto the tail.

Ichthyophis benjii s p. nov. differs from all the species of northeast India and adjacent Myanmar by the combination of the following characteristics. Ichthyophis benjii s p. nov. has a much higher dorsal AG count (388– 422) than other species in the Indo-Burma region: I. alfredi (269–299), I. bannanicus (328–381), I. daribokensis (264–310), I. garoensis (264–309), I. khumhzi (341– 362), I. kohtaoensis (362–366), I. moustakius (238–268), I. multicolor (346–386), I. nokrekensis (269–300), I. sendenyu (283–308), and I. sikkimenis (276–292). For the W/S ratio, Ichthyophis benjii s p. nov. (5.1–5.6) differs from I. daribokensis (2.8–4.2), I. moustakius (2.68–4.0) and I. sendenyu (3.26–4.0). Ichthyophis benjii s p. nov. differs from I. alfredi in a smaller L/H ratio (28.62–45.05 vs. 25.1–28.9 in Ichthyophis benjii sp. nov.) and from I. sikkimensis by the presence of lateral stripes (vs. unstriped in I. sikkimensis ). Furthermore, I. benjii sp. nov. differs from I. khumhzi (50–56), I. kohtaoensis (22–23), and I. garoensis (40–52) in having fewer PMs (38–39); from I. garoensis (39–48), I. khumhzi (47–58), I. kohtaoensis (22–23), I. moustakius (40–43), and I. sikkimenis (41– 44) in number of VP (31–37); from I. khumhzi (42–49) and I. kohtaoensis (20–21) in number of OMs (29–37); from I. alfredi (40), I. daribokensis (36), I. garoensis (38–51), I. khumhzi (40–46), I. kohtaoensis (17–18), and I. sikkimenis (43–45) in number of IMs (29–35). Ichthyophis benjii s p. nov. differs from I. multicolor in having <125 vertebrae (118–124) vs.> 125 (126–132); <120 in I. tricolor . Among many other differences, Ichthyophis benjii sp. nov. can be easily distinguished from its sympatric species I. garoensis , I. moustakius and I. sendenyu by the absence of distinctive moustache-like stripes extending forward from the TAs, and from I. multicolor in having a markedly less prominent, thin, and irregular pale yellowish lateral stripe (see Fig. 4 ).

Molecular systematics. Both the 16s ML and BI phylogenies are congruent in the position of Ichthyophis benjii sp. nov., which is recovered as a moderately supported (65% bootstrap; BPP=0.79) sister taxon to a strongly-supported lineage (100% bootstrap; BPP=1.0) of I. multicolor ( Fig. 5 ). Genetically, Ichthyophis benjii sp. nov. is distinct from I. multicolor with an uncorrected p -distance of 0.055. Uncorrected p -distances to other sampled Ichthyophis are 0.059 –0.085 ( Table 3 ).

Figures

Fig. 1. Holotype (MZMU 1479) of Ichthyophis benjii sp. nov. in life from Durtlang. Photo by H.T. Lalremsanga.

Fig. 2. Preserved holotype (MZMU 1479) of Ichthyophis benjii sp. nov. (A) Dorsal view of full body. (B) Ventral view of full body. (C) Dorsal view of head. (D) Ventral view of head. (E) Left lateral view of head. (F) Ventral side of tail. Each scale bar indicates 10 mm. Photos by Ro Malsawma.

Fig. 3. Distribution of type localities of the Indo-Burman Ichthyophis species, including I. benjii sp. nov.

Fig. 4. Paratypes of Ichthyophis benjii sp. nov. in life: (A) MZMU 1462 from Chhinga Veng, (B) MZMU 1481 from Tanhril, (C) MZMU 2025 from Gosen, and (D) I. multicolor MZMU 1740 from Tuirini Bridge, Aizawl District. Photos by H.T. Lalremsanga.

Fig. 5. Maximum Likelihood phylogram of 16s rRNA. Numbers at internal branches are bootstrap support.Epicrionops marmoratus and Rhinatrema bivittatum were used as the out-group. The taxon name in bold denotes the sample newly sequenced in this study. Numbers preceding taxon names are GenBank accession numbers.