Extreme tadpoles II: the highly derived larval anatomy of Occidozyga baluensis (Boulenger, 1896), an obligate carnivorous tadpole

Abstract

Tadpoles of Occidozyga species have been reported to be carnivorous, feeding on insects and other tadpoles. We present photographic evidence for the previously undocumented larval feeding behavior in O. baluensis. Furthermore, we present a detailed anatomical description of the skull, cranial musculature, and gross gut morphology based on three-dimensional reconstructions from serial sections and lCT imagery. The cranial anatomy of larval O. baluensis is highly derived in many characters, with respect to taxa outside the genus Occidozyga, most notably the palatoquadrate and hyobranchial apparatus, that play a major role in tadpole feeding. A large larval stomach was present in the specimens examined, indicative of a macrophagous carnivorous mode of feeding. Because of the relatively small oral orifice, relatively large-sized food items found in the larval stomach, and the tunnel-like arrangement of structures that form the buccal cavity, we hypothesize that suction feeding utilizing strong negative pressure is employed by this species. Furthermore, we propose that force, rather than speed, is the main characteristic of their feeding. The unique features of the study species substantially expand the known morphospace for tadpoles, particularly among the Acosmanura (Pelobatoidea, Pelodytoidea, and Neobatrachia). Except for Microhylidae, acosmanurans previously described possess limited innovative larval morphologies. Larval carnivory has evolved convergently several times in distant anuran clades and shows structural, behavioral, and functional differences in the known examples.

Deconstructing cartilage shape and size into contributions from embryogenesis, metamorphosis, and tadpole and frog growth

“…Most tadpoles have a mobile suprarostral cartilage in the upper jaw and an infrarostral in the LJ that is of similar shape and size to the MC but aligned more laterally, anterolaterally or dorsomedially than the MC to complement the suprarostral (Pusey, 1938;Haas, 1999;Rocek, 2003;Haas et al 2006Haas et al , 2014. Xenopus tadpoles are distinguished by having their upper jaw skeleton comprised of a broad, immobile suprarostral plate, the edge of which remains straight and does not align with the curving LJ until late tadpole stages (Trueb & Hanken, 1992).…”

“…Having multiple periods of development and growth suggests more opportunity for phylogenetic diversification. Indeed, amphibian PA elements show pronounced interspecific differences in PA skeletal shape that arise during metamorphosis as well as embryogenesis (Smith, 1920;Wilder, 1925;Ruibal & Thomas, 1988;Haas et al 2006Haas et al , 2014Ziermann et al 2013). Further, the embryonic repatterning of certain larval elements and the metamorphic appearance of a new adult element have been identified as key innovations in salamander evolution (Wake, 1982;Alberch & Gale, 1986;Alberch, 1987).…”

Chemical composition of food induces plasticity in digestive morphology in larvae ofRana temporaria

“…Digestive plasticity is suggested to correlate with digestion efficiency (Sibly, 1981) and thus is likely to affect different processes important in nutrient uptake, such as the storage of food before assimilation (McDiarmid and Altig, 1999;Haas et al, 2014), and an increase in nutrient assimilation via increased gut passage time and intestinal surface area. The latter is particularly important, as digestion in tadpoles is supported by microbial fermentation of intestinal bacteria (Altig and Johnston, 1989).…”

“…Studies on the influence of chemical composition of food on other parts of the digestive system that are relevant for food storage before the gut passage (i.e. the larval stomach, Manicotto glandulare; McDiarmid and Altig, 1999;Haas et al, 2014) or on the efficiency of food uptake via the intestinal surfaces (i.e. microvilli; Shi and Ishizuya-Oka, 1996;McDiarmid and Altig, 1999) are so far lacking.…”

Der Filterapparat der Kaulquappen

“…Bei ihnen sind die Anteile von Mundhöhle und Filterapparat unterschiedlich reduziert und die muskulo‐skeletale Anatomie ist verändert. Die Carnivorie entstand unabhängig in sieben Evolutionslinien innerhalb der Anuren . Mundfeld und Hornscheiden können evolutiv zurückgebildet sein (Abbildung c).…”