See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/342468496 Population density, microhabitat use, and size characteristics of Pseudothelphusa dugesi, a threatened species of freshwater crab from Mexico (Brachyura: Pseudothelphusidae) Article in Invertebrate Biology · June 2020 DOI: 10.1111/ivb.12295 CITATIONS READS 0 365 3 authors, including: Elsah Arce Uribe Universidad Autónoma del Estado de Morelos 18 PUBLICATIONS 21 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Living food culture used in aquaculture View project All content following this page was uploaded by Elsah Arce Uribe on 02 July 2020. The user has requested enhancement of the downloaded file. Received: 23 September 2019 | Accepted: 6 May 2020 DOI: 10.1111/ivb.12295 ORIGINAL MANUSCRIPT Population density, microhabitat use, and size characteristics of Pseudothelphusa dugesi, a threatened species of freshwater crab from Mexico (Brachyura: Pseudothelphusidae) Domínguez Emmanuel Carlos Paniagua1 | Uribe Elsah Arce2 | Diego Alfonso Viveros- Guardado1 1Facultad de Ciencias Biológicas, Universidad Autónoma del Estado de Abstract Morelos, Cuernavaca, México The brachyuran crab Pseudothelphusa dugesi, or cangrejito barranqueño, is an en- 2 Laboratorio de Acuicultura, Departamento dangered species endemic to Cuernavaca, Morelos, in central Mexico. Individuals of de Hidrobiología, Centro de Investigaciones Biológicas, Universidad Autónoma del P. dugesi inhabit freshwater springs, which are affected by human actions through Estado de Morelos, Cuernavaca, México wastewater drainage, eutrophication, exploitation, and invasive predators such as Correspondence rainbow trout (Oncorhynchus mykiss). In this study, we evaluated the population den- Elsah Arce Uribe, Laboratorio de sity, microhabitat use, and size characteristics of P. dugesi. Sampling was conducted Acuicultura, Departamento de Hidrobiología, Centro de Investigaciones in May, July, and December of 2018 and March of 2019, during the dry and rainy Biológicas, Universidad Autónoma del seasons in a natural protected area, the Barranca de Chapultepec. Population den- Estado de Morelos, México. 2 2 Email: [email protected] sity was 0.082 crabs/m , female density was 0.052 crabs/m , and male density was 0.112 crabs/m2; ovigerous females were not observed. Males were more abundant than females; the female: male ratio was 1:2.14. Males and females had similar cara- pace widths and lengths, left and right chelae lengths, and mass. Individuals of P. dug- esi were found mostly under or between rocks and under leaf litter. Individuals were more active at night. An understanding of the biology and population characteristics of P. dugesi will help conservationists to develop protective measures and a conserva- tion strategy for this endangered Mexican freshwater crab species. KEYWORDS Barranca de Chapultepec, conservation, endemic crab, freshwater, stream 1 | INTRODUCTION it is important to quantify population density, microhabitat use, and size structure of individual crab species. Large decapod crustaceans Freshwater ecosystems around the world are threatened by human are an important component of freshwater ecosystems because activities including pollution, eutrophication, exploitation, and inva- they process organic matter, prey on small invertebrates and fish, sive species (Friberg et al., 2011; Gherardi, Barbaresi, & Salvi, 2000; and are preyed upon by a variety of vertebrates (Lee, 1998; Penha- Smith, 2003). Declines of amphibians (Kupferberg et al., 2012), Lopes et al., 2009; Poon, Chan, & Williams, 2010). fish (Olden, Hogan, & Vander, 2007), and crabs (Dudgeon, 2003; The brachyuran crab Pseudothelphusa dugesi RATHBUN 1893 Marijnissen, Michel, Clearly, & McIntyre, 2009) have been reported (cangrejito barranqueño) is endemic to Cuernavaca, Morelos, in worldwide. Native and endemic freshwater crabs are particularly central Mexico (Villalobos, 2005). It inhabits freshwater springs, vulnerable to these threats because of their possible limited distri- some of which have been altered by human impacts, such as water bution (Marijnissen et al., 2009). To fully understand this problem, pollution (drainage of wastewater, solid waste) and non-native Invertebrate Biology. 2020;00:e12295. wileyonlinelibrary.com/journal/ivb © 2020, The American Microscopical Society, Inc. | 1 of 6 https://doi.org/10.1111/ivb.12295 2 of 6 | PANIAGUA DOMÍNGUEZ ET AL. FIGURE 1 Pseudothelphusa dugesi, ventral view. A. Female. B. Male. CL, carapace length; CW, carapace width; CHL, chela length invasive predators such as rainbow trout, Oncorhynchus mykiss 2.2 | Field sampling and morphometric (WALBAUM 1792) (unpublished data). Pseudothelphusa dugesi is measurements ranked as “In danger of extinction” on the Mexican list of endan- gered species (NOM-059;SEMARNAT, -2010). However, because Five sites along the main stream (Site 1, 18°54′44.784′′N, basic knowledge of the ecological characteristics and population 99°12′34.081′′W; Site 2, 18° 54′45.724″N, 99°12′34.041″W; biology of this species are lacking, it is listed as “Data deficient” Site 3, 18°54′58.518″N, 99°12′30.114″W; Site 4, 18°55′6.892″N, on the IUCN Red List (Cumberlidge, 2008). This missing knowl- 99°12′34.898″W; Site 5, 18°55′9.617″N, 99°12′33.224″W) were edge limits the prediction of human impacts on the species and randomly selected on a map of the park, and at each site we sampled its habitats, so its vulnerability to human impacts cannot be a 5-m2 (5 × 1 m) transect five times over a 24-hr period (at 01:00, assessed. 06:00, 11:00, 15:00, and 19:00 hr). Thus, we made a total of 100 Here we evaluate population density (crabs/m2), microhabitat use, sampling surveys: one transect per site, sampled five times during and size characteristics of P. dugesi in the Barranca de Chapultepec a 24-hr period, in each of 4 months, following methods of Taggart, natural protected area, which is a stream in Cuernavaca, Mexico. O´Clair, Shirley, and Mondragon (2004). The activity of the crabs was However, since P. dugesi also inhabits other springs in Cuernavaca, recorded, with a crab considered to be active if found foraging (walk- Mexico, future studies will be required for these other areas. This ing) (Green, 1997). All rocks, leaves, and crevices were searched for is especially important because other streams are affected by even crabs, and the microhabitat in which the crabs were found was re- greater human impacts than the Barranca de Chapultepec study corded. Crabs density was calculated as crabs/m2 for each month area (personal observations). In this first evaluation, we aimed to and time of day (Somers & Nel, 1998). Crabs were collected by provide ecological information to inform the development of a con- hand and placed in a transparent 5-mm mesh container (25 L) that servation strategy for this endangered Mexican freshwater crab allowed spring water to flow through it. Crabs were weighed on a species. digital plate balance (OHAUS, 0.01 mg accuracy). For morphologi- cal measurements, each crab was photographed from above in ven- tral view in the same position to avoid errors associated with the 2 | METHODS orientation of the crab. The size of each feature was determined with Image J software to reduce the stress on the crab associated 2.1 | Study area and water conditions with making measurements (De La Torre, Arce, Luna-Figueroa, & Córdoba-Aguilar, 2018). Carapace width (CW) and length (CL), and The urban park Barranca de Chapultepec is a natural protected area right and left chela lengths (CHL; Figure 1) of each crab were meas- located in Cuernavaca, central Mexico (between 18°55′09″ and ured in Image J. The sex of the crabs was determined by the shape of 18°54′30″N, and between 99°12′33″ and 99°12′39″W). The park the abdomen (González-Pisani, Barón, & López, 2017; Figure 1). On has a freshwater spring that originates from a stream 1,466 m above completion of morphometric measurements, all crabs were returned sea level (SEMARNAT, 2014). Sampling was conducted during the to the stream. rainy season (May and July of 2018) and the dry season (December of 2018 and March of 2019) (Martínez-Garza, Osorio-Beristain, Valenzuela-Galván, & Nicolás-Medina, 2011). The mean depth of the 2.3 | Statistical analysis water column, water temperature, oxygen concentration, pH, and total dissolved solids at each collection site were recorded using a Data normality was confirmed using Shapiro–Wilk's test. Water multiparameter meter (HANNA, HI 9829). conditions and water depth from each month and each site were PANIAGUA DOMÍNGUEZ ET AL. | 3 of 6 TABLE 1 Analysis of variance of the physical and chemical and distribution of juveniles (Martinez, 2001), crabs need protection characteristics of the water among sites from hydrodynamic forces that are too strong (Arce & Alcaraz, 2011), Mean ± SD df F P and also need shelter to hide from predators (Arce & Alcaraz, 2013; Moksnes, Pihl, & Van Montfrans, 1998; Richards, 1992). For P. dug- DO (ppm) 4.8 ± 1.5 4 0.57 .72 esi, it is likely that the leaf litter and rock crevice microhabitats pro- pH 7.9 ± 1.1 4 1.23 .30 vide this protection. The use of these microhabitats is also seen in T (°C) 16.4 ± 0.2 4 1.62 .16 other species, such as Pachygrapsus crassipes (RANDAL 1840), in which TDS (ppm) 74.4 ± 9.0 4 0.26 .93 crabs use rocks as shelter to protect themselves from hydrodynamic Z (cm) 27.1 ± 16.8 4 20.81 .00 forces (Lau & Martinez, 2003), and Uca mjoebergi RATHBUN 1924, in Abbreviations: DO, dissolved oxygen; T, temperature; TDS, total which crabs seek rocks as refuge to avoid predation (Reaney, 2007). dissolved solids; Z, depth. In the urban park Barranca de Chapultepec, we observed non-na- tive rainbow trout, O. mykiss, which can be a predator of P. dugesi compared using ANOVA. Population density was compared among (unpublished data). Thus, refuges are indispensable for the protec- microhabitats, and among months using ANOVA.