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Extreme tadpoles: The morphology of the fossorial megophryid larva, Leptobrachella mjobergi

Biozentrum Grindel und Zoologisches Museum, Martin-Luther-King-Platz 3, Hamburg, Germany.
Zoology (Impact Factor: 1.6). 02/2006; 109(1):26-42. DOI: 10.1016/j.zool.2005.09.008
Source: PubMed

ABSTRACT The bizarre larvae of Leptobrachella mjobergi are fossorial and live in the gravel beds of small streams. These tadpoles are vermiform in body shape. Here we present details on their skeleton and musculature, particularly of the head. The entire cranium and its associated musculature are reconstructed in three dimensions from serial histological sections. The hyobranchial apparatus is highly reduced. The head of the L. mjobergi larva is more mobile than in other anuran species. This mobility can largely be ascribed to the exclusion of the notochord from the cranial base and an articulation of the foramen magnum floor with the atlas of the tadpole. The articulation is unique among anuran species, but design parallels can be drawn to salamanders and the articulation between atlas and axis in mammals. In L. mjobergi, the atlas forms an anterior dens that articulates with the basal plate in an accessory, third occipital articular face. The muscle arrangements deviate from the patterns found in other tadpoles: For instance, epaxial and ventral trunk muscles reach far forward onto the skull. The post-cranial skeleton of L. mjobergi is considerably longer than that of other anurans: it comprises a total of 35 vertebrae, including more than 20 post-sacral perichordal centra. Despite a number of features in cranial and axial morphology of L. mjobergi, which appear to be adaptations to its fossorial mode of life, the species clearly shares other features with its megophryid and pelobatid relatives.

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    • "The presence of keratodonts in the larger Leptolalax tadpoles indicates to some extent a substrate-scraping mode of food intake, while keratodonts are lacking completely in Leptobrachella. In their morphological description of L. mjobergi, Haas et al. (2006) discussed the unique features of the feeding apparatus of this species and speculated that the cup–like oral disc without keratodonts is inconsistent with a substrate–scraping mode of feeding. Leptobrachella brevicrus, Leptolalax dringi and Megophrys dringi are to be regarded as currently considered rare species so far known only from their type localities in the borders of the Gunung Mulu National Park or from a few other sites of northern Borneo (Stuart et al. 2008). "
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    • "We present field-based observations and anatomical evidence to address the questions related to the extent of carnivory in this species and the anatomical features that relate to this feeding mode. Examination of structurally and ecologically extremely aberrant tadpoles (see Haas et al. 2006) has the potential to change our perception of tadpole morphospace (Roelants et al. 2011) and lets us better understand the diversification processes in anuran evolution. "
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