Herpetology Notes, volume 14: 1133-1136 (2021) (published online on 20 August 2021)

Predation on leptodactylid and hylid frogs by the freshwater crab Dilocarcinus pagei Stimpson, 1861 (Decapoda, Trichodactylidae) in the Brazilian Pantanal

Guilherme Sichieri1,*, Bruna Lopes1, Pedro Henrique A.G. Moura1, Fernando J. Faciole2, Fabiana R. Costa2, and Ivan Nunes1

The order Anura comprises terrestrial, semi-terrestrial, trichodactylid freshwater crab species native to the or fully aquatic frogs and toads (Haddad and Prado, Amazon and lower Paraná River basins and hypothesized 2005) that inhabit all continents except Antarctica (Frost, to have been introduced into the upper Paraná River 2021), and whose distribution is mainly constrained by basin (Magalhães et al., 2005). This species can be the presence of freshwater bodies (Silvano and Segalla, easily identified by a distinct transverse carina along the 2015). The family Hylidae Rafinesque, 1815 includes anterior margin of the third somite (Magalhães, 2003; 735 species (Frost, 2021) that live on tree-branches or Magalhães and Türkay, 2008). Dilocarcinus pagei emerging vegetation, although they can also be found on is abundant in the Brazilian Pantanal and occurs in the soil, especially during the rainy season (Guimarães association with a variety of phytophysiognomies (Rosa and Bastos, 2003; Protázio et al., 2014; Leite-Filho et al., et al., 2009). The diet of D. pagei has been reported to 2015). Members of the family Leptodactylidae Werner, consist mainly of macrophyte remains, and to a lesser 1896 typically reproduce at the margins of permanent extent also of algae, fungi, and invertebrates such as or ephemeral ponds, where they build subterranean microcrustaceans (Williner and Collins, 2002). nests on muddy soil (Prado et al., 2002; Rodriguez et During a fieldtrip on 13 September 2019, we observed a al., 2004). The flooded plains of the Brazilian Pantanal series of predation events by D. pagei on Boana raniceps favour the occurrence of the hylids Boana raniceps (n = 3), Scinax acuminatus (n = 1), and Leptodactylus (Cope, 1862) (Fig. 1A) and Scinax acuminatus (Cope, podicipinus (n = 2). Predated specimens were not 1862) (Fig. 1C), and the leptodactylid Leptodactylus collected, but we collected vouchers of conspecific podicipinus (Cope, 1862) (Fig. 1D) (Seba et al., 2020). specimens found nearby and deposited these at Coleção Freshwater crabs are herbivores, detritivores, or de Anfíbios do Laboratório de Herpetologia (HCLP–A) predators in tropical ecosystems (Marijnissen et al., with accession numbers 178–180 (B. raniceps), 151–153 2009) and in the latter role they prey primarily upon (S. acuminatus), and 232–234 (L. podicipinus). These invertebrates (Klaus and Path, 2011) but also small crab-anuran predation events took place in the territory vertebrates (Hayes, 1983). The Pantanal is one of the of Fazenda Passo da Ema, Poconé Municipality, Mato largest and most biodiverse wetlands on the planet, Grosso State, Brazil (16.5322°S, 56.6856°W, WGS84; covering an area of approximately 160,000 km², of Fig. 2), where the daily temperature ranged from which 140,000 km² are in Brazil (Keddy et al., 2009). 19–31°C and the relative humidity from 40–80%. Dilocarcinus pagei Stimpson, 1861 (Fig. 1B) is a The area consists of a flooded plain, but when water levels are low different frog species seek out the holes and crevasses that become exposed, including holes that may already be occupied by D. pagei (Fig. 1B). 1 Laboratório de Herpetologia, Instituto de Biociências, Whenever these freshwater crabs encountered an Universidade Estadual Paulista, Praça Infante Dom Henrique s/n, Parque Bitaru, São Vicente, São Paulo 11330-900, Brazil. anuran, they seized the frog with their strong chelae 2 Laboratório de Paleontologia de Vertebrados e Comportamento and began to consume their prey. Animal, Centro de Ciências Naturais e Humanas, Universidade Although records of freshwater crabs preying on Federal do ABC, Rua São Paulo s/n, Jardim Antares, São frogs are historically scarce in the literature (Pyke et al., Bernardo do Campo, 09606-045 São Paulo, Brazil. 2013), these encounters have been better documented * Corresponding author. E-mail: [email protected] in the past decade (e.g., Affonso and Signorelli, 2011; © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. Rosa et al., 2014; Schäfer et al., 2019; Wehrtmann et al., 1134 Guilherme Sichieri et al.

Figure 1. Photographs of the flooded plain area at Fazenda Passo da Ema, Poconé Municipality, Mato Grosso State, Brazil, with holes and crevasses in the ground exposed during low water level. Red arrows indicate (A) Boana raniceps, (B) Dilocarcinus pagei, (C) Scinax acuminatus, and (D) Leptodactylus podicipinus. Photos by Ivan Nunes.

2019). Recently, Wehrtmann et al. (2019) reported an the discussed amphibian species (Williner and Collins, individual of the pseudothelphusid crab Ptychophallus 2002; Sant’anna et al., 2014) favours encounters in the uncinatus Campos & Lemaitre, 1999 manipulating and environment, the open burrows built by male crabs feeding on the toad Cruziohyhla calcarifer (Boulenger, (Fernandes et al., 2020) may provide spaces for frogs 1902) with its cheliped. In addition, there are reports of to nest or take shelter, creating additional opportunities predation by Trichodactylus fluviatilis Latreille, 1828 for predatory interactions. on an egg clutch of Bokermannohyla circumdata (Cope, Introduced species such as D. pagei may pose a 1871), and necrophagy on Rhinella ornata (Spix, 1824) threat to the invaded ecosystem by causing declines (Segadilha and Silva-Soares, 2015; Nogueira-Costa in prey populations and changes in the local food web et al., 2016). Dilocarcinus pagei has been previously (Affonso and Signorelli, 2011). Further studies should reported as a predator of different species of frogs, investigate how often D. pagei feeds on frogs and to including leptodactylids (Affonso and Signorelli, what extent that relatively new interaction is affecting 2011). The reproductive behaviour of L. podicipinus of their population in floodplains. depositing eggs in foam nests inside water-filled basins (Prado et al., 2002) may favour its predation by crabs Acknowledgements. We are thankful to C. Canedo for the that also live in those phytotelmic habitats. Boana pre-review. ICMBio provided the collection permit #51898- raniceps and S. acuminatus can be found on the ground 1 to the senior author. Guilherme Sichieri and Bruna Lopes or on emerging vegetation during the reproductive acknowledge the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior and the Fundação de Amparo à season, when males look for perches to vocalize Pesquisa do Estado de São Paulo (20/04903-9), respectively, (Guimarães and Bastos, 2003; Prado et al., 2005), and for scholarship funding. this behaviour may expose them to predation by crabs. Moreover, while the nocturnality of both D. pagei and Predation on Leptodactylid and Hylid Frogs by Dilocarcinus pagei 1135

Figure 2. Map showing the state of Mato Grosso in Brazil and Poconé Municipality (black star).

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Accepted by Gonçalo M. Rosa