NEW RECORD OF CHACO TUCUMANA GOLOBOFF, 1995 (ARANEAE, PYCNOTHELIDAE) IN ARGENTINA

Introduction[Up]

The family Pycnothelidae Chamberlin, 1917 was recently revalidated by Opatova et al. (‍2020) to accommodate taxa formerly belonging to a diverse mix of nemesiid subfamilies (‍Raven, 1985). The family has a distribution that includes Africa, Australia, South America and New Zealand (‍World Spider Catalog, 2022). Until to date, the family contains 15 genera and 137 described species (‍Montes de Oca et al., 2022; ‍World Spider Catalog, 2022). Spiders belonging to this family can be distinguished by the combination of the following characters: presence of small to large, yellow pallid, soft, developed intercheliceral tumescence covered with few to many setae; cymbium lacking dorsal spines; patella III with 1–1–1 prolateral spines; bipectinate tarsal claws; male tarsi flexible; short spinnerets; tarsal organ located on apical central region; presence of tarsal scopula and absence of claw tufts (‍Goloboff, 1995; ‍Montes de Oca et al., 2022)

The genus Chaco Tullgren, 1905 was established based on C. obscura Tullgren, 1905 from Salta province, northern Argentina. The genus currently includes 12 species, six from Argentina, two from Brazil, two from Chile and two from Uruguay (‍Goloboff, 1995; ‍Montes de Oca & Pérez-Miles, 2013; ‍Ferretti, 2014; ‍Indicatti et al., 2015). Chaco comprises species characterized by four short spinnerets, males with low distal spur on prolateral tibia I bearing three or more spines and absence of inferior claw on all tarsi; females are characterized by having a patterned carapace and legs, no pumpkiniform spigots; absence of inferior tarsal clow and absence of scopula on anterior tibiae (‍Goloboff, 1995). All the species of the genus for which data exist live in burrows, closed with a trapdoor.

In a recent survey in Salta and Tucumán provinces, northern Argentina, we recorded individuals of C. tucumana Goloboff, 1995. Thus, in the present work, we present a new record of C. tucumana for Argentina along with an identification, illustration of morphological characters and a distribution map of the geographic range of the species.

Material and methods[Up]

Spiders were captured during the day by carefully searching the substrate for potential trap doors. Photographs of the female (habitus) and habitat were taken with a Sony DSC-Hx200v. Specimens are deposited in the arachnological collection of CERZOS-Universidad Nacional del Sur (Buenos Aires, Argentina). Spermathecae were dissected and photographed in dorsal view. Photographs were taken with a MShot digital camera mounted on a Leica S APO stereomicroscope. Images were stacked by the image stacking software Helicon Focus 7. The distribution maps were made using the free software QGis (www.qgis.org). The shape file of the Biogeographic provinces for Argentina was obtained from Arana et al. (‍2017).

Results and discussion[Up]

Chaco tucumana Goloboff, 1995

Figs. 1–3

Material examined

TUCUMÁN, Tafí Viejo department, El Cadillal, Aguas Chiquitas, on the banks of the Río Loro (26°36’57.1” S, 65°11’3” W), 22 April 2022, Nicoletta, Panchuk, Schwerdt, Ferretti cols., 1 female (UNS-M0789). SALTA, Guachipas department, Guachipas (25°31’35.2” S, 65°30’28.5” W), 23 April 2022, Nicoletta, Panchuk, Schwerdt, Ferretti cols., 1 female (UNS-M0790).

Identification

Specimens were identified as Chaco tucumana based on the dark uniform color (abdomen with light brown spots) (Figs. 1A–D), fovea procurved (Fig. 1A), labium with two cuspules (Fig. 1F), the flexible anterior female tarsi (Fig. 2A), the dense scopulae on posterior tarsi (Fig. 2B) and spermathecae without basal protuberance and short ducts (Fig. 2C).

Natural history

The spiders constructed burrows with a door (Figs. 3B–C, F–G). The burrows found were not branched, in contrast to what was reported by Goloboff (‍1995), but our observations are scarce. Goloboff (‍1995) reports that the trapdoor has a hinge articulating loosely and sometimes consisting only of a few silk threads and it does not fit inside the burrow mouth instead being generally larger than the burrow opening and lying on the edges of the burrow mouth. In Tucumán province, the door of the specimen found was similar to that reported by Goloboff (‍1995), with few threads holding the door (Fig. 3C) and not fitting tightly in the burrow mouth (Figs. 3B-C). The specimen (Fig. 3D) was collected at almost vertical banks (Fig. 3A) at the foot of a large tree. In contrast, the specimen from Salta province was collected in a burrow constructed close to a rock (Fig. 3F–G) up on a hill slope, in a drier soil (Fig. 3E) and with the hinge articulating more firmly with dense silk (Fig. 3G). In addition, the upper portion of the burrow was noticeably prolonged (Fig. 3G), an aspect similar to that reported for C. tigre Goloboff, 1995 (‍Goloboff, 1995: figs 151–152) in contrast to the general burrow shape of C. tucumana.

Distribution

Previously known from Catamarca, Santiago del Estero and Tucumán provinces (Fig. 4).

New distribution record: SALTA, Guachipas department, Guachipas locality (25°31’35.2” S, 65°30’28.5” W) (Fig. 4).

The new record at Salta province (unusual type of burrow) belongs to the Chacoan Biogeographic province (‍Arana et al., 2021) (Fig. 4B) and the Dry Chaco ecoregion (Fig. 4C), while the typical burrows of C. tucumana were observed in the Yungas Biogeographic province and ecoregion (Figs. 4B–C). Maybe those differences in burrow types are associated with the environmental conditions of the different habitats, being the Chacoan records represented by drier sites than the Yungas. Although Goloboff (‍1995) did not state about the burrows found for some juveniles presumably of C. tucumana inhabiting Colonia Dora, Santiago del Estero, it is expected that those would present the same burrow architecture of the female from Salta, because both areas fit the environmental conditions of the Dry Chaco.