Chaceus Pretzmann 1965
Creators: name: Campos, Martha R.
name: Puerta, Dario A.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pseudothelphusidae
Chaceus

description: Distribution of the genus Chaceus Pretzmann, 1965
The geographical distributional pattern of the genus Chaceus extends to the eastern and western slopes of the Serranía de Perijá and the Sierra Nevada de Santa Marta, as follows: On the eastern slope, we found the following species: Chaceus caecus Rodríguez & Bosque, 1990, C. motiloni Rodríguez, 1980, and C. turikensis Rodríguez & Herrera, 1994. Chaceus caecus specimens were collected in the Serranía de Perijá of Venezuela, Zulia State, in caves such as the Punto Fijo, El Samán, Los Laureles, El Sumidero at an altitude range between 470 to 900 m, all in Venezuela, associated with caves linked to karst formations in boxed valleys that classify the species as stygobionts. Chaceus motiloni, where the type material was collected in Negro River, Kunaná, Zulia, at an altitude of 1100 m, also found in Punto Fijo cave, but only in part of the cave where light prevails during the day time (the entrance and twilight zones), at an altitude of 590 m, is classified as stygophile species. Chaceus motiloni and C. caecus resemble each other in the shape of the digitiform mesial process and marginal process as a basal triangular spine. The lateral process is orbicular in both cases but shows in C. motiloni as a marked basal constriction, absent in C. caecus (see Rodríguez & Bosque 1990: figs. 3A, B, G). Chaceus motiloni may be considered the most probable sister species of C. caecus (Rodriguez & Bosque, 1990). Chaceus turikensis specimens were collected in the Serranía de Perijá of Venezuela, Zulia State, in Mesa Turik, a flat top mountain, in caves such as Las Lianas, Pared Norte, del Río, Laberinto, and the Apón River, at an altitude range between 1700 to 1800 m. The stygophile characters in C. turikensis are fully developed only in adults and consist of slender pereiopods, chelipeds, and diminished and depigmented corneas (Rodríguez & Herrera 1994). Chaceus turikensis is not restricted to caves, since the crabs collected in the Apón River were epigeous.
Chaceus turikensis was recorded on the eastern slope of the Serranía de Perijá of Venezuela on the Mesa Turik, located at the headwaters of the Apón and Palmar rivers in a series of caves with elevations between 1700 and 1800 m, and unevenness ranging from La Liana cave (30 m) to the Pared Norte cave (160 m), linked to extensive limestone outcrops of the Cogollo Group of the Lower Cretaceous age (Group constituted by the formations Apón—Aptian/ Albian (Sutton 1946) of the formations Lisure—middle to upper Albian, and Maraca—Albian (Rod & Maync 1954). Limestones are linked to karst systems associated with mountain systems of steep slopes and structural profiles with deep valleys and in the Mesa Turik (García et al. 1992). Only the Cogollo Group is present, and the karstification is developed in the Maraca Formation which is the youngest unit of the group. Chaceus guajiraensis is known from the western slope of the Serranía de Perijá of Colombia, in the rural area of Fonseca, in the waterfall Los Saltos at an altitude between 980 and 1320 m. The basalts of the territories are sandstones, siltstones, and limestones intercalated with tuffs, breccias, agglomerates, and rhyolitic to andesitic lavas (J1J2-VCct). These territories seem to be associated with the flanks of a deformation front that generates topographies with excessively steep slopes. Both species were found very close to the dividing line of the eastern (Venezuela) and western (Colombia) slopes of the Serranía de Perijá, at a rough distance of 40 km one from each other. In addition, the prototype specimens were in sedimentary materials of the Jurassic and Lower Cretaceous ages. Chaceus cesarensis Rodríguez & Viloria, 1992, was recorded in the central part of the mountain range and has the highest altitude (2150 m). Chaceus ibiricensis Campos & Valencia, 2004 and C. curumanensis Campos & Valencia, 2004 are distributed in the southern part of the western slope, the first one at an altitude range between 1100 to 1400 m. The second species with unique records from Curumaní is known from an altitude of 100 m (Fig. 4, Table 1).
The establishment of the genus Chaceus in the Sierra Nevada de Santa Marta (SNSM) was probably due to the displacement of a paleo SNSM on the Bucaramanga—Santa Marta fault from the south to the north. This geological movement, with an approximate displacement of 100 km on the fault plane carries the species to the current location in the high mountainous area (Tschanz et al. 1974), allowing the emergence of the species C. pearsei (Rathbun, 1915). Chaceus davidi Campos & Rodríguez, 1984, and C. nasutus Rodríguez,1980. Chaceus pearsei is widely distributed in the SNSM in an altitudinal range of 600 to 1580 m. Chaceus davidi is restricted to the “Ciudad Perdida” area in an altitudinal range between 800 and 1000 m, and C. nasutus registers the highest altitudinal range in the SNSM reaching between 1580 and 3000 m. To date in Colombia, only species from epigean environments have been recorded. It may be due to the lack of explorations in the western slopes of the Serranía de Perijá, particularly because of the public order problems in a large part of this territory.
The stygobiont species may exhibit some differences concerning the stygophile ones, for example, a wider and depigmented carapace; longer and slender pereiopods; reduced length of ocular peduncles that do not fully occupy the orbital cavity; diminished and depigmented corneas (Rodríguez & Bosque 1990).
Key to the species of Chaceus Pretzmann, 1965
1. Lateral process of first male gonopod well developed......................................................... 2
- Lateral process of first male gonopod reduced (Campos 2014: fig. 98D).............................. Chaceus nasutus
2. Lateral process of first male gonopod not overreaching the apex................................................ 3
- Lateral process of first male gonopod reaching or overreaching the apex.......................................... 4
3. Lateral process of first male gonopod rounded or lanceolate in caudal view....................................... 8
- Lateral process of first male gonopod subtriangular or elongated in caudal view.................................... 5
4. Lateral process of first male gonopod with basal semicircular notch on lateral surface (Campos 2014: fig. 90B)...................................................................................................... C. cesarensis
- Lateral process of first male gonopod lacking semicircular notch (Campos 2014: figs. 96D, E).............. C. ibiricensis
5. Mesial process of first male gonopod longer than marginal process.............................................. 6
- Mesial process of first male gonopod as long as marginal process (Campos 2014: figs. 94D, E).................. C. davidi
6. Mesial process of first male gonopod ellipsoidal (Rodríguez & Herrera 1994: fig. 2A)..................... C. turikensis
- Mesial process of first male gonopod cylindrical or finger-like................................................. 7
7. Mesial process of first male gonopod finger-like (Campos 2014: fig. 100E)................................ C. pearsei
- Mesial process of first male gonopod needle-shaped (Campos 2014: figs. 92D, E)...................... C. curumanensis
8. Lateral process of first male gonopod orbicular.............................................................. 9
- Lateral process of first male gonopod lanceolate (Fig. 3B, C)................................... C. guajiraensis n. sp.
9. Lateral process of first male gonopod with marked basal constriction (Rodríguez 1982: figs. 14A, B)........... C. motiloni
- Lateral process of first male gonopod without basal constriction (Rodríguez & Bosque 1990: figs. 3A, B)........ C. caecus
description: Published as part of Campos, Martha R. & Puerta, Dario A., 2023, A new species of freshwater crab of the genus Chaceus Pretzmann, 1965 (Brachyura: Decapoda: Pseudothelphusidae) from La Guajira, including distribution and a key to the species of the genus, pp. 463-472 in Zootaxa 5306 (4) on pages 468-470, DOI: 10.11646/zootaxa.5306.4.4, http://zenodo.org/record/14895620