Leptotyphlops breuili, Hedges, 2008

Hedges, S. Blair, 2008, At the lower size limit in snakes: two new species of threadsnakes (Squamata: Leptotyphlopidae: Leptotyphlops) from the Lesser Antilles, Zootaxa 1841 (1), pp. 1-30 : 9-10

Leptotyphlops breuili sp. nov.

Fig. 1B

St. Lucia Threadsnake

Holotype. USNM 564810 , adult male, collected on 13 June 2006 under rock on ground on north slope of Maria Major Island , St. Lucia ( Fig. 2A ), 60 m (13° 43.430’ N, 60° 55.897’ W), by S. Blair Hedges and Carla Ann Hass. Field tag number 267731.

Paratypes. USNM 564811–812 from type locality; 564813–814 from Anse Galet (near Anse La Raye), St. Lucia, 5 m (13° 56.080’ N, 61° 02.950’ W); 222954 from 0.1 mi E Anse Galet River; 564815–817 from 1.6 km N Praslin, St. Lucia, 40 m (13° 52.875’ N, 60° 53.418’ W); Museum of Comparative Zoology, Harvard University ( MCZ) 10693 from St. Lucia (exact locality unknown).

Diagnosis. A small species of the genus, reaching 113 mm maximum TOL (preserved specimens); up to 119 mm TOL in live specimens ( Buley et al., 1997). It is a member of the West Indian bilineatus group having two dorsolateral lines, most closely related to Leptotyphlops bilineatus and L. carlae . It differs from both in having a typical pattern of two spots behind the head and a dark tail ( Fig. 2A–B ). In scale characters ( Figs. 3– 4 , Table 1) it also differs from both species in having a wider PA1 (width/length 2.08–2.28 vs. 1.56–1.93) and a wider PA2 (2.03–2.48 vs. 1.71–2.01). In addition, it differs from L. bilineatus in having a wider SO (0.99– 1.16 vs. 0.78–0.99), a shorter OC (0.63–0.76 vs. 0.78–0.84), and shorter anterior middorsals, PF+FR+IP+IO (2.07–2.28 vs. 2.28–2.55). From L. carlae , it differs in the three characters noted above in the diagnosis of that species. Measurements and scale counts, including those of the holotype, are in Table 1.

Description. Body with 14 scale rows, reducing in region of vent; middle of tail with ten rows; four supralabials and four infralabials. Similar in body proportions to previous species. In average width, PF = IO> IP> F. Eye large, 37–49% distance from naris to posterior edge of eye. Coloration in life dark brown to black above and below, with pale yellow dorsolateral lines extending from two scales behind PA2 to base of tail, defining a reddish-brown middorsal zone three scales in width; tail dark to black, lacking stripes completely, or with faint indication or stripes; usually a dorsal v-marking on last two scales of tail ( Fig. 2A ); lower sides and venter pale grayish-brown, beginning 1.8 scales below dorsolateral lines; pale markings on PA1 and PA2, usually in the form of two irregular spots in line with the dorsolateral lines; pale markings also on each PN scale; 7–18 white scales around vent. Live weight, 0.50–0.70 g (mean = 0.61 g; n = 4 adults).

Etymology. The species name is dedicated to Michel Breuil for his contributions to the herpetology of the Lesser Antilles.

Comments. The species is known from only two areas on Saint Lucia and a third locality on Maria Major Island off the southeast coast. Buley et al. (1997) reported collecting six specimens under rocks and in leaf litter on Maria Major in 1997 (22–24 September), measuring (in life) 58–113 SVL (62–119 TOL). They were not sexed, and all were released. All localities for this species have been in forested areas, on slopes, and there are no reports of it being encountered in open areas or beach habitats. Several other suitable localities in eastern and western St. Lucia were searched during a visit by the author in June 2006 (and during an earlier visit by the author in April 1996) without success, although more effort is needed to better delineate the distribution of L. breuili . The genetic difference between the eastern and western populations on Saint Lucia, ~1.4% ( Fig. 4C ) is much greater than between the eastern locality and Maria Major, suggesting a relatively long period of differentiation on the island. Development of forested areas on Saint Lucia, for housing, roads, tourism, and other activities, is likely to continue reducing the available habitat of this species.

Figures

FIGURE 1. Two species of threadsnakes (Leptotyphlops) from the Lesser Antilles. (A) Leptotyphlops carlae (101 mm TL), adult female paratype (USNM 564818). (B) Leptotyphlops breuili (108 mm TL), adult male paratype (USNM 564811).

FIGURE 2. Distribution and pattern variation in threadsnakes (Leptotyphlops) from three islands in the Lesser Antilles. (A) Distribution and generalized color pattern differences (head, midbody, and tail). The location of samples used in sequence analyses is indicated. (B) Head pattern in three individuals from each island, illustrating variation (MNHN 2006.0516, USNM 564808, 564809; USNM 564810, 564815, 564816; BM1969.792, USNM 564819, 564818). Dashed line in Barbados indicates geologic region of sub-reef outcrop.

FIGURE 3. Variation in scalation of threadsnakes (Leptotyphlops) from three islands in the Lesser Antilles. (A) Head scalation (top and side of head) in representatives from each island (USNM 564809, 564810, 564819). Scale bar = 1 mm. Numbered head scales are rostral, RO (1); prefrontal, PF (2); frontal, FR (3); interparietal, IP (4); interoccipital, IO (5), postnasal, PN (6); preocular, PO (7); parietal-I, PA1 (8); parietal-II, PA2 (9); and ocular, OC (10). (B) Plot of parietal-1 scale width versus length. (C) Plot of parietal-2 scale width versus length.

FIGURE 4. Variation in the number of middorsal scales in Leptotyphlops from the Lesser Antilles. The two groups identified for L. bilineatus are suspected to be different species.