Clelia bicolor ( Peracca 1904 )

Scott Jr., Norman J., Giraudo, Alejandro R., Scrocchi, Gustavo, Aquino, Aida Luz, Cacciali, Pier & Motte, Martha, 2006, The Genera Boiruna And Clelia (Serpentes: Pseudoboini) In Paraguay And Argentina, Papéis Avulsos de Zoologia 46 (9), pp. 77-105 : 86-88

Clelia bicolor ( Peracca 1904)

Oxyrhopus immaculatus ; Peracca, 1895: Chaco, Argentina

Oxyrhopus bicolor Peracca, 1904: Original description, type locality: North of Santa Fe, Argentina

Clelia bicolor ; Bailey, 1970: Argentina and Paraguay

Clelia bicolor ; Abalos & Mischis, 1975: Argentina

Clelia bicolor ; Talbot, 1979: Paraguay

Clelia bicolor ; Yanosky, 1989a,b: Formosa, Argentina

Clelia rustica ; Yanosky, 1989a,b: Formosa, Argentina (see Scrocchi & Giraudo, 2005)

Clelia bicolor ; Bergna & Álvarez, 1990: Northeastern Argentina

Clelia bicolor ; Scrocchi & Viñas, 1990: Argentina

Clelia bicolor ; Cei, 1993: Northwestern and eastern Argentina

Clelia bicolor ; Yanosky et al., 1993: Formosa, Argentina

Clelia rustica ; Yanosky et al., 1993: Formosa, Argentina (see Scrocchi & Giraudo, 2005)

Clelia bicolor ; Giraudo & Contreras, 1994: Departmento Ñeembucu, Paraguay

Clelia bicolor ; Álvarez et al., 1996: Corrientes, Chaco, and Formosa, Argentina

Clelia bicolor ; Couturier & Faivovich, 1996: Santa Fe, Argentina

Clelia bicolor (part.); Aquino et al., 1996: Paraguay

Clelia bicolor ; Yanosky et al., 1996: Formosa, Argentina

Clelia rustica ; Yanosky et al., 1996: Formosa, Argentina (see Scrocchi & Giraudo, 2005)

Clelia bicolor ; Zaher, 1996: Paraguay and Argentina

Clelia bicolor ; Giraudo & Arzamendia, 1997b: Santa Fe, Argentina.

Clelia bicolor ; Cacivio, 1999: Misiones, Argentina

Clelia bicolor ; Leynaud & Bucher, 1999: Gran Chaco

Clelia bicolor ; Cabrera, 2001: Interior Argentina

Clelia bicolor ; Giraudo & Scrocchi, 2002: Argentina

Clelia bicolor ; Giraudo, 2002: Northeastern Argentina

Clelia bicolor ; Álvarez et al., 2002: Chaco, Formosa, and Corrientes, Argentina

Clelia bicolor ; Arzamendia & Giraudo, 2002: Santa Fe, Argentina

Clelia bicolor ; Álvarez et al., 2003: Corrientes, Argentina

Clelia bicolor ; Motte et al., 2004: Paraguay

Clelia bicolor ; Scrocchi & Giraudo, 2005: Formosa, Argentina

Taxonomic History – The taxonomic history of C. bicolor is less confused than that of the other species. Since its original description from north of Santa Fe, Santa Fe Province, Argentina ( Peracca 1904), it does not appear to have been recorded in the study area under any other specific name, except for Yanosky (1989a,b) and Yanosky et al. (1993, 1996). Because of the location and the low number of ventrals, Peracca (1895) appears to have also had an earlier specimen from Resistencia, Chaco Province, Argentina.

Diagnosis – Clelia bicolor in the study area can be distinguished from all other Boiruna and Clelia by the low number of ventral scales (163-187; Appendix 4, Fig. 4). Its gray or brown dorsum is never as dark as that of C. clelia , C. plumbea , and Boiruna . Except for the lateral tips of the ventrals, the venter of C. bicolor is always clear ivory. In C. bicolor of all sizes, the border between the dark dorsal head coloration and the lighter supralabials is sharp and distinct at the dorsal edge of the supralabial row (photographs in Cei, 1993; Giraudo, 2002). The general coloration of C. bicolor is similar to that of C. quimi ; however, the color transition on the side of the head is more gradual in C. quimi , and the dark dorsal color extends further onto the supralabials (see illustration in Franco et al., 1997).

Clelia bicolor is the smallest species (maximum total length 990 mm; Fig. 3). Clelia bicolor and C. quimi generally have 8 supralabials on each side; the other Clelia and Boiruna generally have 7 (Appendix 1).

A dark dorsal stripe is seen in hatchling C. bicolor , C. quimi , and B. maculata . A white nape band may be distinct in hatchlings or almost lacking.

Description – Descriptions of C. bicolor can be found in Peracca (1904), Scrocchi & Viñas (1990), Cei (1993), Zaher (1996), Franco et al. (1997) and Giraudo (2002). Photographs are in Cei (1993), Giraudo (2002), Scrocchi & Giraudo (2005), and Figure 8.

Clelia bicolor is the smallest of the species under consideration; the smallest and largest of 52 specimens were 179 mm and 990 mm ( Fig. 3). There is no significant difference between the lengths of the sexes (t-test; P>0.91).

Clelia bicolor has fewer ventrals than any other species, but the tail is relatively long, and subcaudal counts overlap those of C. quimi (Appendix 4, Fig. 4). Like C. quimi , and in contrast to the other species, C. bicolor usually has 8 supralabials on each side of the head (Appendix 1). The loreal is normal-sized, usually contacting supralabials 2 and 3 (Appendix 3, Fig. 1D).

The hemipenes of our small sample of C. bicolor have two or three pairs of intrasulcal spines and 25-40 extrasulcal enlarged spines (Appendix 2). They are similar to the photographs in Zaher (1996, 1999).

Adult C. bicolor have a dark, almost black, dorsal head color that contrasts sharply with the ivory-colored supralabials. Except for the side of the head, they are colored much like C. quimi ( Franco et al., 1997, Giraudo, 2002). The dorsal head color extends posteriorly as a dark dorsal stripe 9 scale rows wide. The sides are a dusky tan or gray, paler than the dorsal stripe. Underneath, the body and tail are clear ivory except for the lateral tips of the ventrals and a faint zigzag stripe of dark pigment down the center of the tail.

The largest snakes tend to be paler and more gray than the smaller specimens, which tend to be brown. Clelia bicolor never shows the large, irregular white patches seen in some other species.

Hatchlings have a dark head dorsum, which color extends along the back of the body as an almost black stripe 3 scale rows wide (photograph in Giraudo, 2002). Lateral body scales are orange or red, and the venter is white. They usually have a white or orange collar that starts behind the parietals and extends posteriorly 3-4 scale rows. However even in hatchlings, the collar may be only faintly indicated. The collar is often partially or completely divided by the dark dorsal color; in extreme cases it may be reduced to a pair of white patches on the nape. The collar is gradually lost through ontogeny, although a faint indication may be seen even in some large adults.

Juveniles and young adults are tan laterally, sometimes with a pinkish hue (photograph in Giraudo, 2002). As the snake grows, the dark dorsal color invades the sides, until, in the largest specimens, it extends to the tips of the ventral scales ( Cei, 1993). In the intermediate sizes, the lateral scales become reticulate, similar to the coloration in C. rustica .

Distribution – Clelia bicolor is restricted to the Paraguay- Paraná river drainages in Brazil, Paraguay, and Argentina ( Fig. 9). The presence of C. bicolor in Tucumán Province needs to be confirmed. The locality cited by Zaher (1996; FML 0819) for Escaba, Río Marapa , is probably incorrect; no other specimens have been taken from this well-collected locality. The Horco Molle, Tucumán Province locality ( CENAI 3806) may be correct. Isolated northern records from Jujuy Province have been recently reconfirmed ( INBIAL 312, Jorge Baldo, pers. comm.)

Peruvian records referred to C. bicolor ( Dixon & Soini, 1986; Vanzolini, 1986) probably refer to a different species ( Strussman & Sazima, 1993). The old Butantan record (IB 1818) from Pelotas, Rio Grande do Sul in coastal southern Brazil is probably also incorrect ( Bailey, 1970; Franco et al., 1997). Bailey’s (1970) citation of San Luis Province, Argentina is distant from any other record and needs confirmation (Giraudo, 2002; Giraudo & Scrocchi, 2002).

Most of the habitat of C. bicolor is Chaco, either dry forest or that subject to flooding. The Misiones Province , Argentina record by Cacivio (1999) extended the known range up the Paraná River into an area of transition between Humid Chaco and wet Atlantic Forest .