Onychophoran worms are ancient predators that can only live in moist microhabitats and hunt for small invertebrates at night (mostly insects, myriapods, spiders and crustaceans, Read & Hughes, 1987; Monge-Nájera, Barrientos & Aguilar, 1993). However, many spiders are agile and dangerous to onychophorans, and probably they are not frequent prey (Read & Hughes, 1987; Dias & Lo-Man-Hung, 2009); furthermore, some spiders can kill and eat onychophorans (Franco & Monge-Nájera, 2016). Here we report an onychophoran feeding on a spider in Panama.

The observation was made on July 18, 2017, at 10:21 pm, in Sierra Llorona Private Reserve, Colón, Panama; 9,35863°-79,70287°; 491 masl; Premontane Very Moist Forest; precipitation: 3000 a 3500 mm (Autoridad Nacional del Ambiente de Panamá, 2010).

On a mossy rock at the edge of a creek, the first author found an onychophoran feeding on a spider, which was still moving its legs slowly ( Figure 1). That same night he saw four more onychophorans in understory vegetation, but none were feeding. The worm was about 7 cm long and the spider about 4cm long. For future reference, we propose the common name of "Sierra Llorona Leather-Brown Collared Onychophoran" for this species (Sosa-Bartuano, Monge-Nájera & Morera-Brenes, 2018).

The spider seemed to be a ctenid; the family Ctenidae has at least 16 species in Panama (Quintero, 2005). They do not build webs and include aggressive and poisonous species that hunt at night among soil vegetation. These are dangerous spiders and perhaps the onychophoran found a weakened individual and secured it with adhesive, but it is also possible that the worm killed a healthy spider thanks to its stealth hunting behavior (Morera-Brenes & Monge-Nájera, 2010).

We thank Diomedes Quintero and William Eberhard for information on the behavior and possible identity of the spider.

EDITED BY CAROLINA SEAS

Fig 1.
Onychophoran found feeding on a spider in Sierra Llorona, Colón, Panamá (July, 2017). Photographs by Jesse Ashcroft and M. González.

References

Autoridad Nacional del Ambiente de Panamá. (2010). Atlas Ambiental de la República de Panamá. Panama: Gobierno de Panamá.

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Read, V. S. J., & Hughes, R. N. (1987). Feeding behaviour and prey choice in Macroperipatus torquatus (Onychophora). Proceedings of the Royal Society of London B: Biological Sciences, 230(1261), 483-506. doi: 10.1098/rspb.1987.0030

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