Taxonomic summary

Disposition of types. Holotypic male form I: TL 39.0 mm, TCL 17.6 mm; cave at Sótano de La Lucha (17°03’46” N, 93°53’23” W), Ocozocuautla, Chiapas, Mexico; 25 April 2012; colls. A. Gómez, F. Álvarez, J.L. Villalobos, S. Rodríguez, L. García; CNCR 26741. Allotypic female: TL 53.2 mm, TCL 26.8 mm; same locality, date and collectors as holotype; CNCR 26741. Morphotypic male form II: TL 44.6 mm, TCL 22.0 mm; same locality, date and collectors as holotype; CNCR 26741.

Paratypes. Two females, TL 53.2, 41.4 mm, TCL 24.6. 18.9 mm; same date, locality and collectors as holotype; CNCR 35720.

Type locality. Small ponds in total darkness in the cave that leads to Sótano de La Lucha, Ocozocuautla, Chiapas, Mexico; 546 m asl.

Etymology. This species is dedicated to the memory of Adán Gómez González, outstanding biologist and friend, whose untimely passing away has been felt deeply.

Remarks

Procambarus adani new species, is the 15^th cave inhabiting Procambarus species from Mexico (see ^{Mejía-Ortíz et al., 2003}). This group of species show varying degrees of adaptation to cave life and are distributed from Tamaulipas to Chiapas. The occurrence of several species within this group in caves seems to be accidental, as they do not show any obvious adaptations to this environment and they also occur in epigean environments (e.g., Procambarus cuetzalanae Hobbs, 1982; P. cuevachicae Hobbs, 1941; P. ortmanni Villalobos, 1949; P. pilosimanus; P. toltecae Hobbs, 1943; P. villalobosi Hobbs, 1969; P. xochitlanae Hobbs, 1975). In other cases, there is some degree of elongation of appendages, loss or reduction of pigmentation together with epigean occurrences (e.g., Procambarus mirandai, P. sbordonii) making it difficult to define the precise habit of the species. Several species are clearly stygobitic as they occur only in caves, are unpigmented, their appendages elongated and their eyes reduced but with remnants of pigments: Procambarus rodriguezi Hobbs, 1943; P. oaxacae oaxacae Hobbs, 1973; P. oaxacae reddelli Hobbs, 1973, and P. cavernicola Mejía-Ortiz, Hartnoll & Viccon-Pale, 2003. Only 2 species, however, P. xilitlae Hobbs & Grubbs, 1982, from Hoya de las Guaguas, Aquismón, San Luis Potosí and P. adani new species, described herein, have completely reduced eyes, devoid of cornea and all other visual elements, presenting a blunt ocular peduncle (^{Mejía-Ortíz et al., 2003}).

Several characters, in addition to the obvious adaptations to cave life, separate P. adani new species, from other Procambarus species from Chiapas. Regarding the external morphology, the new species has prominent spines on the anterior tip of the postorbital margin, a straight suborbital margin of the carapace, and a relatively wide areola (Fig. 2). The first pleopod bears a longer and slender mesial process than those of the other 4 species from Chiapas; and the lateral shoulder, in cephalic view, is straight towards the central portion of the pleopod, not rounded (Fig. 3) as in P. mirandai, P. llamasi (^{Villalobos, 1983}, plates 48, 52), and P. pilosimanus (Fig. 4).

Another 2 stygobitic species from the neighboring State of Oaxaca, Procambarus oaxacae oaxacae and P. oaxacae reddelli also deserve to be compared with the new species described herein. Regarding the external morphology, P. adani is more similar to P. oaxacae reddelli due to an acute acumen, and the presence of postorbital, branchiostegal and cervical spines (^{Hobbs, 1973}). Other external characters (e.g., epistome, shape of chelae) are similar in the 3 species; however, the morphology of the first pleopods easily differentiate all of them. ^{Hobbs (1973)} considered P. oaxacae oaxacae and P. oaxacae reddelli to be related to P. rodriguezi from Veracruz, and now with the description of P. adani the group of 4 stygobitic species align along a north-south axis in the Isthmus of Tehuantepec, a region that has been recognized as a complex mosaic where several freshwater decapod groups (e.g., crayfish, palaemonid shrimp, pseudothelphusid crabs) show a high diversity of cave adapted forms (^{Álvarez & Villalobos, 2016b}; ^{Álvarez et al., 2020}; ^{Hobbs, 1973}).

Procambarus pilosimanus (^{Ortmann, 1906})

Figs. 5, 6

Figure 5 SEM micrographs of first left pleopod of a male form I of Procambarus pilosimanus from El Carrizal Lake, Lagunas de Montebello National Park, La Trinitaria, Chiapas (16°06’37” N, 91°43’38” W; 1,500 m asl): A, caudal view; B, cephalic view; C, lateral view; D, mesial view. 

Figure 6 Chela of Procambarus pilosimanus: A, El Carrizal Lake, Lagunas de Montebello National Park, La Trinitaria, Chiapas; B, Gruta de Zapaluta, La Trinitaria, Chiapas. Scale bar = 3 mm. 

Cambarus (Procambarus) pilosimanus ^{Ortmann, 1906: 6}, Fig. 2.

Cambarus pilosimanus ^{Pearse, 1911: 110}.

Procambarus pilosimanus ^{Hobbs, 1942: 342} [by implication].-- ^{Villalobos, 1955: 231}, pls. 53, 54; 1983: 220, pls. 53, 54.

Procambarus pelosimanus ^{Creaser, 1962: 7} [erroneous spelling].

Procambarus (Austrocambarus) pilosimanus ^{Hobbs, 1972: 6}; ^{1974: 45}, fig, 182; ^{1989: 53}.

Procambarus pilosimanus ^{Crandall & De Grave, 2017: 635}.

Material examined. Two form I males, TL 47.8, 57.0 mm, TCL 24.7, 27.5 mm; 1 ovigerous female, TL 50.4 mm, TCL 25.7 mm, 60 eggs approximately, 1.5-2-6 mm in diameter, plus 16 juveniles; 29 April 2009; pond by El Carrizal Lake, Lagunas de Montebello National Park (16°06’37” N, 91°43’38” W; 1,500 m asl), La Trinitaria, Chiapas, Mexico; colls. E. Torres, J.L. Villalobos, F. Álvarez; CNCR 25397. One form I male, TL 67.1 mm, TCL 35.5 mm; 1 female, TL 64.7 mm, TCL 34.0 mm; 3 February 1986; La Trinitaria Cave (16°05’54” N, 92°02’45” W; 1,542 m asl), La Trinitaria, Chiapas, Mexico; coll. R. Medellín; CNCR 12319. Three females, TL, 30.6-39.9 mm, TCL 16.0-21 mm; 4 form II males, TL 27.4-40.0 mm, TCL 14.6-20.5 mm; 25 November 2008; pond at km 184 Comitán-La Trinitaria highway, La Trinitaria, Chiapas, Mexico; colls, E. Torres, J.L. Villalobos, F. Álvarez; CNCR 25431. Two form I males, TL 44.2-62.6 mm, TCL 18.0-31.3 mm; 3 females, TL 39.5-47.8 mm, TCL19.3-21.8 mm, plus 6 juveniles; 6 December 1949; Villa de las Margaritas, 18 km ENE from Comitán, Chiapas, Mexico; coll. A. Villalobos; CNCR 1390. One form I male, TL 51.5 mm, TCL 25.5 mm; 1 female, TL 49.5 mm, TCL 23.6 mm; 1 form II male, TL 40.8 mm, TCL 19.4 mm; 3 June 1950; Villa de Las Margaritas, 18 km ENE from Comitán, Chiapas, Mexico; coll. A. Villalobos; CNCR 1391. Four form I males, TL 57.5-71.6 mm, TCL 28.6-36.2 mm, plus 1 male and 3 females; 24 November 1950; Gruta de Zapaluta, La Trinitaria, Chiapas, Mexico; coll. A. Villalobos; CNCR 1389.

Additional material examined. Two form I males, TL 63.1, 48.0 mm, TCL 31.1, 22.7 mm; 1 form II male, TL 42.0 mm, TCL 20.1 mm; 2 females, TL 54.7, 52.2 mm, TCL 27.0, 25.5 mm; 7 April 1986; Tziscao Lake, Lagunas de Montebello National Park (16°04’59” N, 91°40’28” W; 1,485 m asl), La Trinitaria, Chiapas, Mexico; coll. J.L. Villalobos; CNCR 5580. One form I male, TL 36.0 mm, TCL 15.6 mm; 2 form II males, TL 42.4, 37.5 mm, TCL 20.1, 19.0 mm; 1 ovigerous female, TL 47.3 mm, TCL 27.0 mm, with about 40 eggs; 7 April 1986; río Paso del Soldado, rancho San Rafael del Arco, Lagunas de Montebello National Park (16°07’23” N, 91°42’47” W; 1,520 m asl), La Trinitaria, Chiapas, Mexico; coll. J.L. Villalobos; CNCR 5580. Three form I males, TL 64.5, 57.5, 43.4 mm, TCL 31.0, 25.5, 20.5 mm; 24 September 2013; river 4 km E of Tziscao, Lagunas de Montebello National Park (16°06’02” N, 91°37’18” W; 1,500 m asl), La Trinitaria, Chiapas, Mexico; colls. J.L. Villalobos, E. Moreno, J.C. Ojeda, F. Álvarez; CNCR 28382.

Remarks

Procambarus pilosimanus is, until now, an unusual widespread species occurring from central Guatemala to several localities in southern Chiapas, Mexico (Fig. 1). Due to the lack of reference material and to an apparent variable morphology of these crayfishes with pubescent chelae, the identity of several populations within this complex has been problematic. The type specimens were collected by Bocourt in “Coche, près de la rivière de Coban, Guatemala”, and deposited in the Natural History Museum of Paris. The specimens were examined and described as Cambarus (Procambarus) pilosimanus by ^{Ortmann (1906)}. Regarding the exact type locality of the species ^{Ortmann (1906)} stated the following: “I have not been able to locate this place, nor a river “Coban”; but Coban is the well-known capital of the province of Alta Vera Paz. The river at Coban is called Rio Cahabon. Coban, Alta Vera Paz, is the locality for a species of Cambarus mentioned by Huxley (1878)”. ^{Ortmann (1906)} also mentioned another specimen from an unidentified locality in “Belize, British Honduras”, that is still pending for confirmation, and if found would expand the range of the species considerably. ^{Villalobos (1955}, ¹⁹⁸³⁾ reported several localities in Chiapas for P. pilosimanus around the city of Comitán, in Gruta de Zapaluta and Villa de Las Margaritas, based on specimens that are deposited in the CNCR. We now add samples from El Carrizal Lake, within the “Lagunas de Montebello” National Park.

From the specimens examined we can conclude the following. The gonopod morphology of form I males is relatively constant in all the samples and corresponds to the drawings presented by ^{Villalobos (1983; plate 54)} from specimens of Gruta de Zapaluta, Municipality of La Trinitaria, Chiapas (Fig. 5). In caudal view, the size and shape of the mesial process, the broadly rounded distal margin of the lateral shoulder; in mesial view, the cephalic shoulder poorly developed, strongly inclined and the shape and size of the central projection, of the males with pubescent chelae and the figures of ^{Villalobos (1983; pg. 253}, plate 54, Figs. 2, 6) are similar, but with differences in the central projection: centrocaudal process fused or not, cephalic process small or absent and with or without superior spinule. In regards to the external morphology, there is noticeable variation in the number of cervical and branchiostegal spines, and in the length/height proportion and presence of pubescence in the chelae (Table 1). It is interesting to note that in the same area between La Trinitaria and “Lagunas de Montebello” National Park, different morphologies of the chelae can be found, even within the same population. The chelae that are somewhat elongated (> 4 times as long as high) are not pubescent, while the shorter more robust ones are (Fig. 6).

In particular, the populations of Gruta de Zapaluta, Villa de Las Margaritas, Laguna de Tziscao and Río Paso del Soldado, Chiapas, the last 2 within the “Lagunas de Montebello” National Park, seem to have different morphologies of the chelae with the gonopod showing slight variations from the typical P. pilosimanus described by ^{Ortmann (1906)}. Over the years, from the first samples collected in the area in 1950, until very recently, the 2 types of organisms continue to be present in the area. The more conservative conclusion is that 2 different morphs are occurring sympatrically in the area, one occupying an area from Villa de Las Margaritas to the northern section of the “Lagunas de Montebello” National Park, and with some overlap, a second one occurring towards the southern section of “Lagunas de Montebello” National Park. These observations clear out the confusion of finding in the same general area 2 types of crayfish, sometimes in the same microhabitat. It remains to be determined if there is 1 or more new species to be described from the area.