Taxonomía de onicóforos de Santander, Colombia y termogravimetría, calorimetría de barrido diferencial y espectroscopía infrarroja de la secreción adhesiva (Onychophora: Peripatidae)

Abstract

Onychophoran worms are terrestrial organisms that have changed relatively little since the mid-Cambrian. We collected Macroperipatus geagy in coffee plantations at "Hacienda El Roble", Santander, Colombia, and here redescribe the species based on 15 individuals. A digital three-dimensional reconstruction of the ventral side of the body indicates that the primary and accessory papillae lack a defined distribution pattern. Diagnostic characters: one main tooth and one accessory tooth in the outer jaw, and one main tooth, one accessory tooth and seven denticles in the internal jaw. Measurements: length (X=45.66 mm; SD=26.10), weight (X= 0.95 g; SD= 2.21) and number of lobopods (X= 28.13 pairs; SD= 1.30). We present a taxonomic key for six species of Macroperipatus. The liquid adhesive secretion lost 60% of the initial weight at 70 °C (solid: 13% close to 90 °C). The stability phase of the liquid secretion was within 90-280 °C (100 °C -205 °C in the solid secretion). The starting degradation temperature of the sample was 355 °C. Heat flow changes in the solid and liquid secretions were confirmed by the sample behavior during thermogravimetric analysis. The percentage of β sheets calculated by infrared spectrum was 59%. In comparison with Nephila spiders, the onychophoran secretion lost more weight and entered the phase of degradation at lower temperatures. This secondary structure of proteins gives the onychophoran adhesive secretion a tensile strength and extensibility similar to those of the silk produced by spiders for prey-capture.