Descriptions and Biological Notes on Three Unusual Mantellid Tadpoles (Amphibia: Anura: Mantellidae) from Southeastern Madagascar

Home , Mantellidae, Mantidactylus, Mantidactylus guttulatus

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 119(3):418^25. 2006. Descriptions and biological notes on three unusual mantellid tadpoles (Amphibia: Anura: Mantellidae) from southeastern Madagascar

Ronald Altig and Roy W. McDiarmid* (RA) Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi 39762 U.S.A., e-mail: [email protected]; (RWM) Patuxent Wildlife Research Center, National Museum of Natural History, Washington, D.C. 20560-0111 U.S.A., email: e-mail: [email protected]

Abstract.•The morphologies of three unusual tadpoles from slow- flowing, sandy-bottomed, rain forest streams in southeastern Madagascar are described. The large oral apparatus of the tadpole of Boophis picturatus Glaw, Vences, Andreone, and Vallan, 2001 lacks all keratinized structures and has an elaborately-folded lower labium with five, radially oriented, flat- topped ridges. The tadpole of Mantidactylus guttulatus (Boulenger, 1881) lacks all keratinized mouthparts and has three immense papillae where the upper jaw normally occurs. The tadpole of Mantidactylus lugubris (Dumeril, 1853) has an ornate oral apparatus involving greatly hypertrophied derivatives of jaw serrations and unique structures on the lower labium that resemble labial teeth.

The endemic anuran fauna of Mada- in their respective generic and species gascar is dominated by species in the groups. genera Boophis and Mantidactylus (Man- tellidae). Their described tadpoles typi- Materials and Methods cally have a common morphology, (i.e., 3-8 upper labial tooth rows, commonly The oral terminologies of Altig & three lower tooth rows, usually emargin- McDiarmid (1999) and the staging table ate oral disc with a dorsal gap in the of Gosner (1960) are used. Muscles of the marginal papillae, sinistral spiracle, dex- oral apparatus were viewed with trans- tral vent, and dorsal eyes). Thus, the mitted polarized light (e.g., Carr & Altig collection of three tadpoles with bizarre 1991), and translucent tissue was stained oral structures from streams in the with Crystal violet to increase contrast. vicinity of Ranomafana, Fianarantsoa Formalin-preserved specimens were criti- Province, was completely unexpected. cal-point dried, sputter coated with gold- These tadpoles have characteristics that paladium, and viewed with a Ziess SMT considerably expand our understanding Stereoscan 360. Measurements were made of the diversity of tadpole oral morphol- with an ocular micrometer (0.1 mm), and ogy. The larvae also show extremes in those involving the spiracular aperture, modifications of typical oral morphology eyes, and nares were made from the and differ strikingly from known tadpoles centers of those structures. Body terminus was defined as the junction of the posterior body wall with the axis of the tail myotomes. Gut contents of one Corresponding author. species were boiled in nitric acid to isolate VOLUME 119, NUMBER 3 419

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Fig. 1. Left, lateral views of tadpoles of (A) Boophis picturatus, (Stage 37, 35 TL, USNM 563654), (B) Mantidactylus guttulatus (Stage 27, 29.4 TL, USNM 563657), and (C) M. lugubris (Stage 30, 30.7 TL, USNM 563659). the diatoms. All specimens were collected identical to the sequence of adults posi- by RA from 15-30 Dec 1991 from small tively identified as Boophis picturatus streams and rivers in Ranomafana Na- Glaw et al., 2001 (ZSM 672/2003; Gen- tional Park, ca. 6 km west of Ranoma- bank accession AY848610; M. Vences, fana, Fianarantsoa Province, Madagas- pers. comm.). car, and representative samples are Twenty-two specimens (USNM 563652- deposited in the collections of the Na- 54) in Gosner Stages 25-46 were avail- tional Museum of Natural History able for study. Measurements (mm) of (USNM). a Gosner Stage 37 specimen (USNM 563654) are: 35 total length (TL), 13 Tadpole Descriptions body length, 22 tail length, 4.4 tail muscle height at base, 3 tail muscle Boophis picturatus Glaw, Vences, width at base, 2.4 maximum dorsal fin Andreone, & Vallan, 2001 height located 13 from body terminus, Figs. 1A, 2A, D 1.4 maximum ventral fin height located Our identification of these tadpoles is 11.2 from body terminus, 8.8 body width based, in part, on data derived from located 7.5 from snout, 6.3 body height a molecular survey of Malagasy tadpoles located 7.9 from snout, 1.7 eye diameter, (e.g., Thomas et al. 2005). A tadpole with 0.8 pupil diameter, 4 interorbital dis- the morphology described here matched tance, 0.4 narial diameter, 2.5 internarial the mitochrondrial 16S RNA sequence of distance, 2.1 snout to naris, 4.3 snout to a tadpole from Ranomafana (ZSM 821/ eye, 7.5 snout to spiracle, 3.4 naris to 2004; Genbank accession DQ367352) eye, and 4.5 transverse diameter of oral which had more than 456 base pairs disc. Other major characteristics are: oral 420 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Fig. 2. Oral apparatus of (A) Boophis picturatus (transverse oral disc width = 4.5 mm), (B) Mantidactylus guttulatus (2.7), (C) M. lugubris (3.1) and (D) surface epithelial cells on the labial ridges of Boophis picturatus (scale bar = 20 am) and labial tooth-like structures on the lower labium of M. lugubris at (E) low (scale bar = 89 am), and (F) high (scale bar = 31 |j,m) magnifications. disc large, ventral, and nonemarginate diameter vent tube lies totally to the right with complicated folds in the lower of the ventral fin, and its ventral wall is labium; marginal papillae tiny, uniserial, large (2.5 mm long). and complete around disc; eyes dorsal; The jaws lack keratinized sheaths; in spiracle sinistral; vent dextral; dorsal fin profile the suprarostral is medially convex terminating at dorsal extent of body; (0.2 mm measured longitudinally), and neuromasts not visible; and all kerati- the infrarostrals are broadly U-shaped. nized mouthparts absent. At rest, the large upper labium is some- The body is slightly depressed and flat what bowl-shaped and nearly overhangs ventrally; the buccopharyngeal area con- the mouth (Fig. 2A); typical submargi- stitutes ca. 28% of the ventral body nal papillae are lacking. A single, sagit- length. The snout is broadly rounded in tal, low-profile ridge and two pairs of dorsal view, and the nares have a pro- lateral ones extend radially from the nounced pigmented rim with a slight mouth for most of the length of the dorsal protuberance. The low fins termi- labium but are not easily visible without nate in a point (Fig. 1A). The spiracular staining; the cell margins (Fig. 2D) are tube has a short medial wall. The large- well defined by intervening crevices that VOLUME 119, NUMBER 3 421 abound with microvilli. At low magnifi- tail musculature; the ventral fin and entire cations, the cell surfaces appear slightly ventral surface are nonpigmented and rougher than the surroundings; at higher transparent. The coloration provides magnifications the surfaces are uniquely amazing camouflage against the sandy textured. substrate. Tadpoles resting in shallow A Gosner Stage 40 specimen (37.5 TL) depressions in the sandy bottom could has six myotomes in the rectus abdominis not be seen even in 3-10 cm of water (1- in parallel-sided bands. Fibers of the first 2 m wide). three myotomes are tightly packed and This tadpole surely is one of the most the myosepta are closed; more anterior specialized foragers among known frog bundles have fewer fibers and open larvae. Tadpoles of B. picturatus were myosepta. The musculus mandibulolabia- found only in a short (•10 m) section of lis superior is absent, and the musculus a shallow, low gradient stream dubbed mandibulolabialis inferior is present as Sand Creek about 0.6 km (by trail) NE of a small bundle beneath the most lateral the Research Camp. Live and preserved part of the longitudinal ridges on the specimens (examined at 50 X) contained lower labium. Buccopharyngeal papillae nothing but large sand grains; no organic include a small, medially located hemi- material was visible. The dry mass of sand spherical flap with a crenulate edge, (0.63 g) taken from the gut of a Gosner a profusion of tightly spaced buccal floor Stage 36 (40.8 TL) individual was 30% of and buccal roof arena papillae with the intact wet mass (2.1 g) of the tadpole. ornate, papillate tips, and a cluster of Fifteen of the largest sand grains (x = 4.1 tightly spaced, similarly shaped papillae ± 0.7 mm longest dimension) made up between the infrarostral cartilages. The 54% of the weight of the gut contents, longest buccal floor arena papillae are and many of the remaining grains were positioned laterally and lack ornamented not especially small. The sizes and distri- tips. Two large lingual papillae with large, bution of sand grains suggest that this clavate, papillate heads are arranged tadpole ingests grains in a relatively transversely on the oval tongue anlage narrow range. Whether the tadpoles feed and bordered posteriorly by four smaller preferentially in a part of the stream but similarly structured papillae. where currents have sorted the substrate In life the tadpoles are nearly trans- by relative grain size, or whether they parent with a blotched pattern of mela- selected a narrow range of grain sizes nophores and gold to silver iridophores. from among those available is not known. Patches of iridophores positioned in For several reasons, we believe the former layers deeper than the skin form spots is true. Tadpoles were found only where on the dorsolateral body wall adjacent to the sandy substrate was relatively coarse, the base of the tail musculature and below and grains in the gut were of similar size. the eye. In preservative, the body of the The guts of several other kinds of tadpole is colorless, except for scattered tadpoles from other microhabitats on dots and small blotches of melanic the same stream typically contained dark, pigment in the skin and deeper layers; organic debris. Second, these tadpoles dark pigment is concentrated over the were never found in microhabitats where brain and dorsolaterally in the abdominal tadpoles of other species were common or wall directly behind the front limbs. The over substrates of finer or coarser sand dorsum of the tail muscle has 4-5 diffuse than in the stream center. Examinations bands, and the more prominent anterior of the gut contents revealed diatoms in band slants anteriorly. Small, scattered eight genera, but at least 90% were species black blotches occur on the dorsal fin and of Eunotia (Eunotiaceae), a pennate form 422 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON that prefers acidic, oligotrophic waters. istics are: oral disc ventral, nonemargi- Because diatoms and other microalgae nate, and transversely oval; eyes dorsal; inhabit interstices among sand grains spiracle sinistral; vent dextral; dorsal fin where light can penetrate, it seems likely terminating 1.0 mm before dorsal body that moderately large grains match that terminus; ventral fin terminating at body; size and that the tadpoles feed in portions neuromasts not visible; and keratinized of the stream where diatoms are readily mouthparts absent. available and easily harvested. Three immense, flexible, slightly Observations of specimens feeding in curved, thorn-shaped papillae extend the lab showed the lower labium extend- from the region where the upper jaw ing distally and laterally so that the sheath normally occurs and lie in the sausage-shaped ridges separate in a radial spaces between the folds of the lower pattern; during closure, the disc forms labium. The larger central papilla is ca. pleats as it retracts proximally and 0.6 mm. A similar papilla is situated medially. At rest, the pleats on the lower lateral to the bases of the outside mem- labium are arranged so that the two bers of the trio. The oral disc (Fig. 2B) parasagittal ridges lie next to each other has prominent, widely spaced, uniserial, and cover a depression in which the marginal papillae (16 per mm ventrally) sagittal ridge sits. that become less prominent or form wavy crenulations dorsolaterally. A dorsal me- Mantidactylus guttulatus dian gap occurs in the marginal papillae. (Boulenger, 1881) Spine-like, submarginal papillae are Figs. IB, 2B abundant and diverse; they include ca. 20 papillae that lie in a transverse line Several species in this group (subgenus anterior to the three large papillae, a large, Mantidactylus) likely occur near Rano- basally-trifid, lateral papillar unit on each mafana, and these tadpoles were identi- side of the mouth, many smaller papillae fied tentatively by comparing the patterns scattered across the lower labium, and 5- of hand and foot webbing and the 6 large papillae that project from near the distinctive femoral gland of a stage 41 base of what appears to be a nonpigmen- individual with syntopic adults. ted, nonkeratinized, nonserrate lower jaw Seven tadpoles in Gosner Stages 25, 27, sheath. and 41 (USNM 563655-57) from the The body is flat ventrally and widest at Sakaroa River were available. Measure- about the plane of the eyes; a constriction ments (mm) of a stage 27 specimen occurs at the spiracular wall. A distinct (USNM 563657) are: 29.4 total length, rim on the posteromedial quadrant of the 10.5 body length, 18.9 tail length, 3 tail narial aperture is absent anterolaterally. muscle height at base, 2.6 tail muscle The tail terminates in a narrow point width at base, 1.4 maximum dorsal fin (Fig. IB). The nonpigmented spiracular height located 11.3 from body terminus, 1 tube has a free, projecting (ca. 0.3 mm) maximum ventral fin height located 13.7 medial wall. The largely nonpigmented from body terminus, 7.3 body width and vent tube attaches to the right side of the 4.8 body height located 5 from snout, 1.5 ventral fin and has a large aperture; dusky eye diameter, 0.7 pupil diameter, 4 in- pigment occurs in the ventral wall near terorbital distance, 0.1 narial diameter, the aperture. 2.5 internarial distance, 1.5 snout to naris, In preservative, the entire, nonpigmen- 4.1 snout to eye, 8 snout to spiracle, 2.6 ted venter is transparent, as is a sizeable naris to eye, and 2.7 transverse diameter area around and anterior to the eye. The of oral disc. Other important character- remainder of the dorsum is crudely VOLUME 119, NUMBER 3 423 blotched with dark pigment. The dorsal width at base, 1.2 maximum dorsal fin fin and tail musculature are patterned height located 13.7 from body terminus, 1 with many distinct, irregular blotches maximum ventral fin height located 16.2 formed from pigment in the skin and from body terminus, 5.9 body width deeper layers near the muscles; the ventral located 4 from snout, 3.8 body height side of the caudal musculature and the located 5.2 from snout, 1.1 eye diameter, ventral fin are nonpigmented. 0.3 pupil diameter, 2.7 interorbital dis- A Gosner Stage 41 specimen (40 TL; tance, 0.09 narial diameter, 1.8 internarial USNM 563656) has the major features distance, 1.1 snout to naris, 2.9 snout to described for the stage 27 specimen, and eye, 6.6 snout to spiracle, 1.7 naris to eye, the oral disc shows no signs of meta- and 3.1 transverse diameter of oral disc. morphic atrophy. Neuromasts are visible Other pertinent characteristics include: near the eye. The area in front of the eye oral disc almost ventral, nonemarginate, is pigmented, the eyes face more laterally, with median dorsal gap in marginal and the nasolacrimal duct projects from papillae; eyes dorsal; spiracle sinistral; the naris to near the front of the eye. The vent dextral; dorsal fin terminating ca. ventral marginal papillae also are larger 4.8 mm posterior to dorsal tail-body (0.2 mm), and those on the lateral parts junction; ventral fin terminating at body; of the disc are more distinct and pointed neuromasts not visible; and labial tooth than in the stage 27 tadpole. A golden tint row formula (LTRF) of 0/3(1). Glaw & on the surface of the distal two-thirds of Vences (1992:167, fig. 80, tad 29) pro- the large, upper, middle papilla suggests vided small line drawings, a black and light keratinization, and the ventral mar- white photograph, and a brief description gin of the oral disc is not folded as orderly of this tadpole based on specimens from as in the smaller specimens. Tolagnaro in southern Madagascar. In Some tadpoles of M. guttulatus were the second edition of their field guide, found in leaf mats in the same small they repeated the drawings and descrip- stream (Sand Creek) in which B. pictur- tion and added scanning electron micro- atus occurred. Those described here were graphs of the mouthparts (Glaw & taken under small, rather dispersed leaf Vences 1994:167, figs. 192, 193, tad 28). mats in the shallows of the Sakaroa The lower labium has widely spaced, River. conical, keratinized structures (12 per mm in left half-row of row P-l) in three rows, each with a median gap (Fig. 2C). These Mantidactylus lugubris (Dumeril, 1853) cones differ in structure and form from Figs. 1C, 2C, E, F typical labial teeth (Fig. 2E, F), and each Six specimens (USNM 563658-60) in row sits atop a flat ridge that is delimited Gosner Stages 25^43 were examined and by crevices rather than being raised above identified by a metamorphic individual the local terrain as with typical labial and figures in Glaw & Vences (1992). tooth ridges. Lateral views of hand-cut Unfortunately, multiple taxa are known sections of the lower labium observed by this name, and the ultimate name to be with polarized light show the cones sitting associated with the Ranomafana popula- slightly within the epithelium, no replace- tion^) will require additional study (M. ment units beneath them, and their ridges Vences, pers. comm.). Measurements lacking the massive amounts of connec- (mm) of a Gosner Stage 30 specimen tive tissue usually seen in tooth ridges. A (USNM 563659) are: 30.7 total length, 9.6 demarcation on the upper third of the body length, 21.1 tail length, 2.8 tail cone may indicate a fracture plane, but muscle height at base, 2.6 tail muscle we have not seen a cone broken at this 424 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON point. The surface of the cone distal to lateral view this tadpole resembles a dark- this line differs from that of the basal two- ly pigmented tadpole of Hyalinobatra- thirds. chium sp. (Centrolenidae). No such ridges or cones occur on the In life, all upper surfaces are uniformly upper labium. The free margin of the black, although at 10X magnification, upper labium stops dorsolaterally, and one can see a sparse but uniform pepper- a series of short, uniserial "marginal" ing of bright green chromatophores papillae situated directly on the surface throughout the dorsum. At about stage of the snout extend medially for a short 40, the chromatophores begin to aggre- distance. The ventral marginal papillae gate to form the transverse body band of are considerably longer than the lateral the adult, and red gills are visible through ones. Two short rows of stubby papillae the skin. The venter is mostly clear of lie immediately lateral to the jaws and pigment, and, except for a general fading appear to interdigitate when the labia to dark brown, no notable color changes come together during closure. occurred in preservative. The plane of the upper jaw is recessed A Gosner Stage 25 (16.9 TL) preserved abruptly from the level of the papillae on specimen agrees with the above descrip- the snout. The margins of the arms of the tion, except that it is more pale and less widely V-shaped upper sheath are slightly uniformly pigmented; row P-3 is only concave, and a single series of long (ca. faintly developed, and the jaw spikes are 0.2 mm medially), slightly flattened, par- less intensely pigmented. In a Gosner allel, straight, lightly keratinized spikes Stage 40 (31.8 TL) specimen, row P-3 is (ca. 22 per mm) project posteriorly from somewhat less prominent, neuromasts are it. The lengths of the spikes decrease visible near the eye, and the throat and laterally, so that a line connecting their belly have a scant suffusion of melano- tips mirrors the outline of the base of the phores. upper jaw sheath. A series of about 54 In a Gosner Stage 26 (37.5 TL) long, recurved spikes (33 per mm) with specimen, a feltwork of fine, criss-crossed rounded front faces project anteriorly and collagen fibers gives a sheen to the throat form the lower jaw armament. Even and anterior part of the belly. The though the basal three-quarters of the musculus mandibulolabialis is absent, jaw spikes are pigmented and project from and the rectus abdominis has six myo- the jaw tissue, there is no indication that tomes with closed myosepta. these spikes are formed of repeating units In the buccopharynx, a small, subrec- like serrations of a typical jaw sheath. Live tangular medial flap with irregular edges tadpoles can open their mouths far is present, and the immense internal naris enough to clear the two sets of spikes. sits in a reverse-comma shaped depres- The track of the lower spikes forms a wide, sion; the anterior end of the pocket is flat-bottomed U-shape, and observations minutely papillate. A slight, U-shaped of live animals suggest that this curvature wall in the prenarial pocket has a minutely can be altered considerably. papillate border. A single, large prenarial The depressed body (Fig. 1C) is flat- papilla and one large, medial and several tened ventrally and is widest slightly smaller, postnarial papillae are visible. A behind the plane of the eyes. The bucco- few buccal floor arena papillae occur in pharyngeal area constitutes ca. 46% of two sparse lines. Two, small, lingual the ventral body length. The low, mostly papillae are arranged transversely and nonpigmented fins join in a rounded lean toward each other. Two transverse point. The sinistral spiracular tube has rows of papillae are positioned directly a short, free medial wall. In dorsal and behind the lower jaw. VOLUME 119, NUMBER 3 425

All tadpoles of this widespread species one species and guidance on the system- were collected in December above and atics of a second. M. Sullivan analyzed below Riana Cascade of the Sakaroa the tadpole gut contents and K. Spencer River in Ranomafana National Park. made the drawings. This reach is ca. 5 m wide and 20-50 cm deep and flows at ca. 30 cm/sec. The river Literature Cited is a mosaic of quietly flowing water over a sandy bottom interspersed with riffles Altig, R., & R. W. McDiarmid. 1999. Body plan: of cobble and rock. Specimens were development and morphology. Pp. 24•51 in captured primarily from the upstream R. W. McDiarmid and R. Altig, eds., 2 Tadpoles: the biology of anuran larvae. ends of leaf mats (ca. 0.3-10 m ) that University of Chicago Press, Chicago, Illi- formed immediately below riffles or nois, 444 pp. cascades where the diurnally-active adults Boulenger, G. A. 1881. Description of a new species were abundant. Specimens in a dip net of frog from Madagascar.•The Annals and moved by serpentine undulations of the Magazine of Natural History (5)7:360-361. Carr, K. M., & R. Altig. 1991. Oral disc muscles of body and tail rather than by the rapid anuran tadpoles.•Journal of Morphology tail-beats typical of most tadpoles. Tad- 208:271-277. poles (Gosner Stages 27-30) maintained Dumeril, A. 1853. Memoire sur les Batraciens in containers with fine sand never at- Anoures de la famille des Hylaeformes ou tempted to burrow but always hid under Rainettes, comprenant la description d'un genre nouveau et de onze especes nouvelles.• a leaf. Annales des Sciences Naturelles, Paris (Series The arrangement of the dorsal margin- 3, Zoologie) 19:135-179, plate 7. al papillae, the presence of keratinized Glaw, F., & M. Vences. 1992. A fieldguide to 'teeth' only on the lower labium, the the amphibians and reptiles of Madaga- nature of the tooth ridges, and the scar. Moos-Druck, Leverkusen, Germany, 331 pp. unusual jaw sheaths are unique. The , & . 1994. A fieldguide to the spike-like jaw structures probably act in amphibians and reptiles of Madagascar. a sieving or winnowing action that allows Second edition. Moos-Druck Leverkusen selective gathering of small particles. Very and FARBO, Koln, Germany, 480 pp. specific flow rates may be important, and , , F. Andreone, & D. Vallan. 2001. Revision of the Boophis majori group (Am- whether the tadpoles feed by active buccal phibia: Mantellidae) from Madagascar, pumping or passive filtration (e.g., Oto- with descriptions of five new species.•Zoo- phryne robusta, Wassersug & Pyburn logical Journal of the Linnean Society 133: 1987) is not known. 495-529. Gosner, K. L. 1960. A simplified table for staging anuran embryos and larvae with notes on Acknowledgments identification.•Herpetologica 16:183-190. Thomas, M., L. Raharivololoniaina, F. Glaw, M. We thank P. C. Wright of SUNY- Vences, & D. R. Vieites. 2005. Montane Stony Brook for the opportunity to work tadpoles in Madagascar: molecular identification and description of the larval stages of in the Ranomafana National Park and B. Mantidactylus elegans, Mantidactylus made- Andriamihaja for logistical help. Assis- cassus, and Boophis laurenti from the Andrin- tance was provided to RA by the research gitra Massif.•Copeia 2005:174-183. guides P. Talata, R. Randriamampianona Wassersug, R. J., & W. F. Pyburn. 1987. The and E. Rajeriarison. F. Andreone and J. biology of the Pe-ret' toad, Otophryne robusta (Microhylidae), with special consideration of Faivovich offered helpful comments on its fossorial larvae and systematic relation- an earlier draft of the manuscript. M. ships.•Zoological Journal of the Linnean Vences provided genetic information on Society 91:137-169.