The anatomy and structural connectivity of the abdominal sucker in the tadpoles of Huia cavitympanum , with comparisons to Meristogenys jerboa (Lissamphibia: Anura: Ranidae)

Abstract

The tadpoles of many anuran amphibians inhabit lotic habitats and evolved oral devices to adhere to the substratum. Although published anatomical descriptions of rheophilous tadpoles exist, little is known about the modifications in gastromyzophorous tadpoles that possess abdominal suckers and live in torrential sections of streams. We describe the gastromyzophorous tadpoles of Huia cavitympanum and Meristogenys jerboa from torrential streams of Borneo, with special attention to the anatomy of their abdominal suckers and their relations to cranial structures and musculature. One cranium of H. cavitympanum and its associated muscles were computer‐reconstructed in three dimensions from serial histological sections. The abdominal sucker and oral sucker comprise a set of muscles and ligaments that attach to internal skeletal structures. Some muscles could be identified to attach directly to soft tissue of the abdominal sucker and most likely contribute to suction. Comparing tadpoles of H. cavitympanum to the closely related gastromyzophorous M. jerboa reveals differences in external and internal features, such as cornu trabeculae fusion and jaw details. Because of phylogenetic uncertainties, it is unclear whether or not this structural complex evolved once or several times convergently in ranids.

Molecular phylogenetic analysis of a taxonomically unstable ranid from Sumatra, Indonesia, reveals a new genus with gastromyzophorous tadpoles and two new species

“…Sumaterana gen. n., Huia, Meristogenys, and Amolops can be distinguish from Chalcorana, Clinotarsus, Hydrophylax, Hylarana, Odorrana, and all other ranids (except, Rana sauteri, Kuramoto et al 1984) by having gastromyzophorous tadpoles. Although R. sauteri has gastromyzophorous tadpoles (Kuramoto et al 1984), Gan et al (2015) pointed out that R. sauteri larvae differs from the gastromyzophorous tadpole of Huia and Meristogenys in significant features of the sucker (see below). Amolops and R. sauteri seem only distantly related to Huia and Meristogenys (Pyron and Wiens 2011; this study), and independent evolution in gastromyzophorous tadpoles must be assumed.…”

“…Their body profile is streamlined with an extended sloping snout. Their adhesive abdominal sucker allows them to cling to rocks even in the fast-flowing, turbulent water of cascades (Nodzenski and Inger 1990, Gan et al 2015. The abdominal sucker occupies almost the entire ventral surface of the body immediately posterior to the oral disk; both act together to press the body to the substrate through suction.…”

“…The sucker has raised thickened lateral and posterior rims that seal against the substrate; the oral disk itself is broadly expanded to almost full body width. On the ventral surface of this sucker, there are spots or bands of brown skin, i.e., keratinized epithelium, probably enhancing friction when the sucker engages with the rock surface (Inger 1985, Gan et al 2015. The tadpoles are able to loosen the suction momentarily to drag themselves forward by action of their strongly developed jaws; algae and other organic rock overgrowth is scraped off by the jaws and keratodont rows of the oral disk while wandering over the rock surface (Inger 1966, AH pers.…”

“…Members of the gastromyzophorous tadpole guild are relatively rare among anurans. They are known only in certain bufonids (e.g., Rao and Yang 1994, Boistel et al 2005, Aguayo et al 2009, Rueda-Solano et al 2015 and some Asian ranids: species of Amolops Cope, 1865, Huia Yang, 1991, Meristogenys Yang, 1991, and Rana sauteri Boulenger, 1909(Kuramoto et al 1984, Yang 1991, Malkmus et al 2002, Ngo et al 2006, Shimada et al 2007, Stuart 2008, Gan et al 2015.…”

The gastromyzophorous tadpoles of Atelopus elegans and A. palmatus (Anura: Bufonidae), with comments on oral and suction structures

“…Only few studies have focused on the structure of the abdominal sucker in these groups. For example, Gan et al [40] presented the detailed structure of the abdominal sucker in Huia cavitympanum. This description shows the structures and muscles, also present in the Atelopus´abdominal sucker but arranged differently.…”