Mantidactylus microtis ( Guibé 1974 ), Guibe, 1974

Andreone, Franco & Nussbaum, Ronald A., 2006, A revision of Mantidactylus microtis and M. microtympanum, and a comparison with other large Madagascan stream frogs (Anura: Mantellidae: Mantellinae), Zootaxa 1105, pp. 49-68 : 52-57

Mantidactylus microtis ( Guibé 1974)

( Figs. 1–4 )

Material examined.— MNHN 1973–1080, 1081 (holotype and paratype), Chaînes Anosyennes, ruisseau, Camp Sommital (= Camp VII), 23.XI.1971, leg. Ch.P. Blanc; MNHN 1973­1082, same locality and collector, 16.XI.1971; MNHN 1973–1083, 1084 (paratypes), Chaînes Anosyennes, Cuvette, Sommet (proche des Camps VI–VII), leg. Ch. P. Blanc, 16.XI.1971; MNHN 1973–1085 (paratype) Chaînes Anosyennes, Camp IV e IIIbis, leg. Ch. P. Blanc, 2.XII.1971; MNHN 1973–1086 (paratype), Chaines Anosyennes, Camp V, leg. Ch. P. Blanc, 1.XII.1971; MNHN 1975­2636 / 2649 and 2651 /2655, Andohahelo [= Andohahela], 1800 m, torrent, leg. J. Arnoult, I.1954; UMMZ 198414–198421, Ampamakiesiny Pass, C. J. Raxworthy, 26.XII.1990, UMMZ 198422, same locality and collector, 28.XII.1990, UMMZ 214574–214586, PN d’Andohahela, Parcel 1, 13.5 Km NW of Eminiminy, 1100 m, leg. A. P. Raselimanana & J. B. Ramanamanjato, 13.XI.1995, UMMZ 214587, PN d’Andohahela, Parcel 1, 15 Km NW of Eminiminy, leg. A. P. Raselimanana & J. B. Ramanamanjato, 18.XI.1995; UMMZ 214588, same locality and collectors, 19.XI.1995; UMMZ 214589, PN d’Andohahela, Parcel 1, 15 Km NW of Eminiminy, 1440 m, leg. A. P. Raselimanana & J. B. Ramanamanjato, 24.XI.1995; UMMZ 214590, PN d’Andohahela, Parcel 1, 20 Km SE of Andranondambo, leg. A. P. Raselimanana & J. B. Ramanamanjato, 2.XII.1995; UMMZ 214591–214592, PN d’Andohahela, Parcel 1, 20 Km SE of Andranondambo, 1600–1660 m, leg. A. P. Raselimanana & J. B. Ramanamanjato, 2.XII.1995; UMMZ 217629, Ampamakiesiny Pass, leg. C. J. Raxworthy, 26.XII.1990; ZSM / FGZC 2437, 2439, 2489–2491, 2494, 2495, Andohahela National Park, 1600–1700 m, leg. P. Bora, 28.I. 2005; ZSM / FGZC 2532, Andohahela National Park, 1600–1700 m, leg. P. Bora, 30.I.2005.

Original name. Rhacophorus microtis Guibé, 1974 .

Diagnosis. A medium sized Mantidactylus , adults up to 60 mm SVL ( Tab. 1 ). Fingers with large and sub­triangular expansions. Hands not webbed. Toes with sub­triangular dilatations smaller than fingers. Feet totally webbed. Femoral glands absent. Sub­articular tubercles small. Inner and outer metatarsal tubercle absent. Tibio­tarsal articulation of appressed hindlimb reaching tip of snout or beyond. Vomerine teeth present. Head quite flattened, with prominent nostrils. From above the head profile is rounded, larger than longer, reaching the point of maximum width at the level of the eye. Tympanum ovoid, very small and rather indistinct, much narrower than terminal expansions of fingers. Skin from finely granular to granular on back, smoother on belly. Cloaca simple to tubular. In males sometimes the cloaca is overhung by a bilobed epidermic flap. In life, greyishbrown or light brownish on back with darker dots that mimic the colouration of the stone on which it lives. Transverse darker bands are present on upper part of fore­ and hindlegs.

The warts of the dorsal skin are evident and rounded, and with a lighter top. Finger and toe expansion are white, with a median longitudinal darker ridge. Eye brownish­yellowish with golden glitterings. Sub­horizontal black pupilla. Outer perimeter of the iris black. Belly dirty whitish shading to yellowish, except area near cloaca, which appears lighter.

Distribution. (1) Chaînes Anosyennes (TT); (2) Andohahela RN 11, Parcel 1 (20 Km SE of Andranondambo); (3) Andohahela RN 11, Parcel 1 (unnamed site); (4) Ampamakiesiny, Pass. Altitude range: 1100–1800 m a.s.l.

Eggs and tadpoles. Just laid eggs were observed on 2–3 December 1995 at Andohahela (20 Km SE of Andranondambo) by A. P. Raselimanana (Nussbaum et al. 1999). They were laid in a jelly mass on stones above water level, usually above areas where it hunts or reposes. One individual (undetermined sex) was observed as resting with the eggs after they were deposited (A. P. Raselimanana, pers. comm.). Eggs are quite large and quite blackish in colour: one dissected female (UMMZ 198418) revealed 42 eggs, with a mean diameter of 3.18 ± 0.25 mm.

Habits. According to the original notes by Ch. P. Blanc, the holotype MNHN 1080 and one paratype MNHN 1081 were found within vegetation next to a stream, while another paratype MNHN 1082 was found within moss percolated by water. A. P. Raselimanana (pers. comm.) observed the species at Andohahela, between 990 and 1500 m of elevation (apparently most abundant at about 1100 m). Individuals were observed within and along some streams with large boulders. They preferred boulders along small waterfalls 0.50 to 3.0 m in height. Frogs usually adhered to stones, by flattening their body and with spread legs. These habits were confirmed by, P. Bora, F. Glaw and M. Vences, who found the species at Andohahela, at about 1600–1700 m of altitude. So far, no acoustic behaviour is known.

Sexual dimorphism. Adult males smaller than females. The body size in males ranged 34.30–55.80 mm (mean ± SD = 41.30 ± 6.03 mm, n = 17), and 37.20–48.40 mm in females (44.40 ± 5.25 mm, n = 10). There is no evident sexual difference in overall coloration. The only apparent dimorphic feature between some males and females is the morphology of the cloacal opening. In likely immature or reproductively inactive individuals, the cloaca is a simple terminal slit, as in most other Mantidactylus species. In adult females (most likely in reproductive season), the cloaca is tubular and curved downwards. In adult males the cloaca is similarly directed downwards, while the opening is overhung by a skin flap, sometimes bilobed. Considering the habitat where the species lives (fast streams), we suspect that the cloacal morphology is functional in regards to the egg laying in running waters. During egg deposition the male and female cloacae are likely juxtaposed, thus forming a nearly closed structure which allows for more efficient fertilization. A somehow similar structure was observed for Boophis albilabris and B. occidentalis , two species that like M. microtis frequent fast running streams ( Cadle 1995, Andreone et al. 2002). Although Guibé (1974) and Blommers­Schlösser & Blanc (1991) indicated the presence of a vocal sac we were unable to detect it in the analysed M. microtis specimens. We suspect that their note was based upon the analysis of a series housed in Paris (MNHN 1975­2636 / 2649 and 2651 /2655). These animals, coming from “Andohahelo” (a misspelling for Andohahela), and collected by J. Arnoult (in January 1954), are badly conserved and were likely not well fixed. For this the skin of these specimens is loose, and especially the throat is so relaxed that may have given the aspect of a vocal sac. In specimens more recently collected (e.g., those from UMMZ and ZMS series) there is no evidence of this structure.

Similar species. Mantidactylus microtis differs from M. microtympanum (which has a somehow similar colouration) in having a smaller size and more slender habitus, and for the skin texture, which is more granular, and the belly colour, which is more uniformly whitish or greyish, while in M. microtympanum there are several spots on the throat. The head of M. microtis is more flattened and more roundish seen from above than in M. microtympanum , in which the snout is pointed. Furthermore, the nostrils are more relevant when seen from the profile. Mantidactylus microtis is also similar in overall habits and morphology to M. lugubris , which is smaller at adult size (around 30–45 mm), has a blackish or black and greenish banded colouration (mostly greyish with darker spots and dots in M. microtis ), relevant femoral glands (absent in M. microtis ), and a pointed snout.

Furthermore, Mantidactylus lugubris emits trilling vocalisations, while M. microtis is not yet known to vocalise.

Figures

FIGURE 1. Mantidactylus microtis. Live individual from Andohahela, 20 Km SE of Andranondambo (photo by A. P. Raselimanana).

FIGURE 2. Mantidactylus microtis. Live individual from Andohahela, unnamed site (photo by F. Glaw and M. Vences).

FIGURE 3. Mantidactylus microtis. Preserved specimen from Parc National dAndohahela, Parcel 1, 13.5 Km NW of Eminiminy, 1100 m (UMMZ 214577): A, dorsal side; B, ventral side.

FIGURE 4. Details of the cloaca in a Mantidactylus microtis: A, male (UMMZ 214578); B, female (UMMZ 214577). The arrow indicates the bilobed flap typical of most males.

Tables

TABLE 1. Morphometric data for Mantidactylus microtis and M. microtympanum. For abbreviations see Material and Methods. Values are provided as mean ± standard deviation (at 0.1 mm). Minimum and maximum values are given between parentheses.

Species	Mantidactylus microtis	Mantidactylus microtympanum
Sex	Males Females	Males Females
No. of measured specimens	17 10	28 12
SVL	41.3 ± 6.0 44.4 ± 3.4 (34.3–55.8) (37.2–48.4)	52.9 ± 5.6 75.7 ± 10.7 (40.6–64.2) (61.5–96.2)
HW	15.3 ± 2.1 16.4 ± 1.2 (13.2–20.8) (14.6–17.6)	19.7 ± 4.2 29.1 ± 7.5 (13.6–29.7) (11.9–49.5)
HL	13.8 ± 2.0 14.9 ± 1.3 (11.8–19.7) (12.8–16.7)	17.3 ± 3.2 25.4 ± 5.0 (12.0–28.8) (17.8–36.5)
ED	6.0 ± 0.7 6.3 ± 0.6 (5.23–7.70) (5.63–7.76)	8.1 ± 0.9 10.6 ± 1.3 (6.13–10.15) (8.70–13.69)
END	3.6 ± 0.5 4.09 ± 0.5 (2.8–5.0) (3.2–4.8)	4.6 ± 0.7 6.4 ± 0.9 (3.1–6.5) (5.3–8.3)
NSD	2.7 ± 0.6 2.9 ± 0.5 (2.0–4.5) (2.2–4.0)	4.2 ± 0.7 6.1 ± 1.1 (3.1–5.9) (3.7–8.3)
NND	4.5 ± 0.8 5.1 ± 0.7 (2.7–5.6) (3.9–6.5)	5.7 ± 0.9 6.9 ± 1.2 (3.1–7.9) (5.0–9.3)
IED	5.8 ± 0.8 6.1 ± 0.5 (4.5–7.6) (5.6–7.1)	6.2 ± 0.8 8.39 ± 1.3 (4.2–8.4) (6.2–10.5)
TD	1.6 ± 0.2 2.0 ± 0.4 (1.2–2.0) (1.4–2.7)	2.3 ± 1.1 3.0 ± 0.9 (1.3–7.8) (2.0–4.9)
HAL	13.6 ± 1.4 15.0 ± 3.4 (11.5–16.4) (12.1–24.1)	15.9 ± 2.1 21.4 ± 3.0 (11.4–21.2) (17.2–27.6)
FORL	19.6 ± 2.0 21.7 ± 1.9 (15.8–24.3) (19.0–24.3)	23.5 ± 3.1 33.4 ± 4.0 (15.6–29.2) (28.6–40.6)
FOL	20.0 ± 3.9 21.4 ± 4.0 (16.7–29.4) (18.1–31.2)	27.0 ± 3.2 36.2 ± 5.4 (20.4–33.8) (23.7–45.8)
FOTL	28.1 ± 4.6 30.7 ± 1.2 (17.3–38.5) (28.8–32.4)	35.4 ± 5.0 49.4 ± 4.5 (21.8–44.7) (43.3–56.5)