Excavatory Cycle of Leposternon microcephalum Wagler, 1824 (Reptilia, Amphisbaenia)

Abstract

SUMMARY:The excavatory movements of the spade-snouted amphisbaenid Leposternon microcephalum (Reptilia, Squamata) was studied with the aid of videofluorscopy (X-ray) techniques. This allows the observation of skull and column movements along tunneling, and a more detailed motion observation, being so a novel approach for amphisbaenian excavatory researches. A single specimen of Leposternon microcephalum was kept in a glass terrarium filled with semoline, and filmed with a scopy (X-ray) machine. Fixed anatomical marks on the head of the specimen were put in drawings from the framed recordings. Selected sequences of the recordings were fragmented in isolated frames for motion observation. The analysis of the recordings revealed a repetitive pattern of excavatory cycles, with retreating and downward bending of the head before its upstroke to compact the substrate tunnel roof. Follows a dropping of the head, which lays over the substrate giving support for the next retreating and downward head bending. This is an essential step that was neglected in earlier cycle descriptions. The initial downward head bending was not previously properly described for spade-snouted amphisbaenians. The excavatory movements of spade-snouted amphisbaenians are usually treated as a two-stepped cycle, but the evidence that this excavatory cycle has three steps is given here.

Body and skull morphometric variations between two shovel-headed species of Amphisbaenia (Reptilia: Squamata) with morphofunctional inferences on burrowing

“…Thus, the descriptions of the locomotor pattern of a single individual may represent the pattern exhibited by its species, making the data relevant to inter-specific comparisons (see Rocha-Barbosa, 1996;Santori et al, 2005;BarrosFilho et al, 2008). Likewise, important studies on Amphisbaenia locomotion were based on a unique individual (e. g. Kaiser, 1955;Gans, 1960;Barros-Filho et al, 2008). Therefore, we believe that the descriptions of the excavatory movements based on a single individual of L.o scutigerum do not limit the comparisons with L.omicrocephalum species.…”

“…This technique, based on X-ray recording, has been used in behavioral studies of fossorial species of amphisbaenians (Barros-Filho et al, 2008;Hohl et al, 2014) and caecilians (Summers and O'Reilly, 1997;Measey and Herrel, 2006, Herrel and Measey 2010, 2012. (2014) to film individuals of L.omicrocephalum, L.oscutigerum was kept in a glass terrarium filled with dry/loose semolina, and with lead markers placed on the outer face of the wall terrarium.…”

“…Thus, the excavatory pattern of L.oscutigerum (n = 37 cycles) was determined and compared inter-specifically with the three-step gait pattern exhibited by L.o microcephalum (n = 132 cycles), according to Barros-Filho et al (2008) and Hohl et alo(2014).…”

“…This is followed by the dropping of the head, returning to the initial static position (Barros-Filho et al, 2008;Hohl et al, 2014).…”

Body and skull morphometric variations between two shovel-headed species of Amphisbaenia (Reptilia: Squamata) with morphofunctional inferences on burrowing

“…In the last 60 years, the locomotor tunneling behavior of L.omicrocephalum has been incidentally studied through visual observations (Kaiser, 1955), motion pictures of the external body (Navas et al, 2004), and the videofluoroscopy technique (Barros-Filho et al, 2008;Hohl et al, 2014). The more recent description of the excavatory cycle of L.omicrocephalum is presented as: (1) initial static position with the gular and anterior body regions lying over the tunnel floor;…”