Mazax akephaloi, Perger & Pett, 2022

Perger, Robert & Pett, Brogan L., 2022, Mazax akephaloi sp. nov. - a new Neotropical spider species resembling ‘ headless’ Ectatomma ants (Araneae: Corinnidae: Castianeirinae), Zootaxa 5150 (4), pp. 579-590 : 582-586

publication ID	https://doi.org/ 10.11646/zootaxa.5150.4.6
publication LSID	lsid:zoobank.org:pub:D2F51EDC-7929-4112-93DF-A69983BFF4A4
DOI	https://doi.org/10.5281/zenodo.6638462
persistent identifier	https://treatment.plazi.org/id/5D2AC71C-FF83-FFF0-FF4E-F487F653FB57
treatment provided by	Plazi
scientific name	Mazax akephaloi
status	sp. nov.

Treatment

Mazax akephaloi View in CoL sp. nov.

urn:lsid:zoobank.org:act:3EEEAAC0-7000-4A34-BBD7-CA2D4E2609DE

Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Type material. Holotype ♂: BOLIVIA: Santa Cruz department, Santa Cruz de la Colina, Urubo, 17.760833°S, 63.24°W, 432 m a.s.l., 21–28.XII.2019, leg. R. Perger, edge of Chiquitano forest (ZMH-A0015362). GoogleMaps

Allotype ♀: same data as for preceding ( CBF).

Paratypes: 1♂, same data as for preceding (ZMH-A0015360) ; 6♂ 10♀, same data as for preceding ( CBF) ; 3♂ 4♀, Santa Cruz department, La Guardia, 17.8830°S, 63.3177°W, 480 m a.s.l., 9.IX.2015, leg. R. Perger, edge of Chiquitano forest ( CBF). PARAGUAY GoogleMaps : 1♂, Alto Paraguay department, Parque Nacional Defensores del Chaco, Misión Cué, Tribu Nueva , 20.1227°S, 60.3246°W, 6.IX.1982, leg. J.A. Kochalka ( MNHNP: IBNP-JAK-CR 000.00.2.717) GoogleMaps ; 1♂; Presidente Hayes department, 25 Laguas , 22.924°S, 59.486°W, 11–12.XII.1983, leg. J.A. Kochalka ( MNHNP: IBNP-JAK-CR 000.00.2.719) GoogleMaps .

Other material examined. 1 subadult ♂: PARAGUAY: Parque Nacional Defensores del Chaco , Misión Cué, Tribu Nueva, 20.1227°S, 60.3246°W, 1–6.IX.1982, leg. J.A. Kochalka ( MNHNP: IBNP-JAK-CR 000.00.2.718) GoogleMaps .

Diagnosis. Mazax akephaloi sp. nov. can be separated from all known congeners by a combination of the following characters: tibia I ventral spination 5– 4 in males (5 at prolateral margin) and 5– 5 in females, feathery setae on carapace, and embolus sub-apical with spatulate extension (males of all known congeners have the embolus tapering evenly, either twisted or straight, see Reiskind (1969)). Females can be diagnosed by a combination of lung-shaped ST II and slightly undulating CDs.

White feathery setae on the carapace are only shared with M. pax (tibia I spination 3–3) and M. ramirezi (tibia I spination 4–4) ( Reiskind 1969). Mazax spinosa (Simon, 1898) and M. xerxes Reiskind, 1969 have a tibia I ventral spination of 5–5, but no feathery setae on the carapace ( Reiskind 1969).The lung-shaped ST II of females of M.akephaloi sp. nov. are only shared with M. ramirezi (CDs more twisted) and the nearly straight CDs with M. chickeringi Reiskind, 1969 (ST II globose), but neither have both characters combined ( Reiskind 1969; Rubio & Danişman 2014).

Remarks. Apochinomma acanthaspis and A. armatum possibly belong to Mazax but were not included in the most recent taxonomic works on this genus ( Reiskind 1969; Rubio & Danişman 2014). The types of both species were not available for study. The type of A. armatum was likely destroyed in a recent fire (A. Kury, unpublished data) and the type of A. acanthaspis is likely lost (C. Rollard, personal communication). According to the original descriptions and illustration by Simon (1896), the holotype female of A. acanthaspis has a considerably less pronounced abdominal constriction and flatter ventral sclerite, lacks the first pair of abdominal setae (present in M. akephaloi sp. nov.), and has the metatarsus I with spine formula 3–3 (2– 2 in M. akephaloi sp. nov.). The female holotype of A. armatum has a tibia I spine formula of 2–2 and whitish coxae II–III ( Mello-Leitão 1922) ( M. akephaloi sp. nov. with tibia I with spine formula of 5– 5 in females and brownish coxae).

Etymology. The specific epithet, akephaloi , means "headless ones" (ἀκέφαλοι) in Greek, mythical headless men who were rumored, in antiquity and later, to inhabit remote parts of the world ( Syropoulos 2018). One hypothesis for the origin of the myth of the akephaloi is the observation of the combat tactic of the North African Blemmyae tribe in which they keep their heads pressed close to the chest ( Dijkstra 2013). The epithet refers to the observation that M. akephaloi sp. nov. lack a structure resembling the head of their ant model E. permagnum and have a skull-shaped sternum.

Male holotype. Body length 6.79; carapace length 2.96, width 1.5, carapace index 50.6; cephalic width 0.84, cephalic index 55.85; abdomen length 3.32, maximum width anterior part 1.21, maximum width posterior part 1.39, abdominal index 41.8; dorsal sclerite length 2.66, maximum width same as maximum abdomen width. Eyes: AER 0.55; AME–AME 0.09; AME–ALE 0.02; PER 0.64; PME–PME 0.14; PME–PLE 0.07.

Color and microsculpture. Dorsum dark blackish-brown in life, with purplish tinge when seen in sunlight (color faded to reddish-brown in ethanol; Figs 2A View FIGURE 2 , 3A View FIGURE 3 ); carapace and posterior part of sclerite posterior of constriction weakly shiny, smooth, microsculpture finely reticulate, with evenly distributed, fine pits; petiole and anterior part of sclerite heavily wrinkled and shiny, wrinkles on petiole transverse and on anterior sclerite longitudinal, abdomen posterior of dorsal sclerite glabrous, shiny; legs glabrous, shiny, with regularly arranged narrow, transverse ridges from which emerge setae, dark brown; femora I–II translucent, yellowish to white prolateral to ventrally; tarsi I–IV cream with dark brown tips.

Setation. Dorsum with separate white feathery setae, forming dense transverse band in abdominal constriction; separate, erect, simple, moderately long yellowish-brassy setae all over dorsum, denser and longer on posterior part of abdomen, similar simple and feathery setae on legs. First pair of abdominal setae simple, indistinct, second pair of abdominal spines heavily sclerotized, emerging from two distinct tubercles ( Fig. 4A View FIGURE 4 ).

Carapace. Long pyriform, front slightly convex, cephalic area laterally somewhat narrowed, broadening towards middle, widest in middle, narrowing posteriorly, posterior margin truncate ( Figs 2A View FIGURE 2 , 3A View FIGURE 3 ).

Eyes. Both eye rows slightly recurved, eyes approximately equal, with narrow, slightly darker rings, remaining characters as in genus diagnosis.

Chelicerae. Two teeth on both the pro- and retromargins. Promargin with distal tooth about twice the size of basal tooth. Retromargin with two subequal teeth, slightly smaller than largest promarginal tooth.

Sternum. Skull-shaped, narrowing posteriorly with conspicuous indentation just anterior to coxa III.

Abdomen. Petiole conspicuous, elongated, with anterior margin concave; abdomen roughly obovate, distinctly constricted dorsally and laterally at about middle, anterior part dorsally bulged out to transverse elliptic bead, posterior part orbicular, broader than anterior part; dorsal sclerite completely covering abdomen laterally, sclerite length 80% of abdomen length, slightly convex posteriorly; ventral sclerite not reaching to level of inframamillary sclerite, latter narrow, subrectangular, broader than long ( Figs 2A View FIGURE 2 , 3A View FIGURE 3 ).

Palp. Tibia with two distinct, long setae and several shorter setae, margin distinctly edged, RTA absent; maximum width of tibia 58% of maximum width of bulb when viewed retrolaterally; tarsus with globose genital bulb drawn out into moderately long, broad neck, with short, sclerotized embolus, sub-apical with spatulate extension, embolus ending in pointed tip with apical twist; sperm ducts with two loops, one retrolateral and one median to embolus tube ( Fig. 4 View FIGURE 4 ).

Female allotype. Body length 6.23; carapace length 3.05, width 1.59, carapace index 52.13; cephalic width 0.89, cephalic index 56; abdomen length 2.58, width 1.58, abdominal index 61.24; dorsal sclerite length (width agrees with abdominal width) 1.26; Eyes: AER 0.58, AME–AME 0.09, AME–ALE 0.04, PER 0.69, PME–PME 0.13, PME–PLE 0.14.

Color, microsculpture, setation, carapace shape and eye characteristics as in male. Abdomen larger, lateral constriction of abdomen much less pronounced as in male (cf. Figs 2 View FIGURE 2 , 3 View FIGURE 3 ), dorsal sclerite suboval, only extending to abdominal constriction, ventral sclerite absent.

Epigyne. ST II large, lung-shaped, about four to five times the diameter of very small circular ST I. CD joins posterior end of ST II, almost straight and projected laterally leading to small oval CO that are posterolateral to ST II. FD arises at anterior margin of ST I ( Fig. 5 View FIGURE 5 ).

Variation. While the abdominal constriction of the male is determined by the shape of the large dorsal sclerite, it varied in females according to the nutritional or reproductive state.

Geographical and ecological distribution. Mazax akephaloi sp. nov. is known from the Bolivian locations of La Guardia and Santa Cruz de la Colina in the Santa Cruz Department and the Paraguayan locations of Misión Cué, Tribu Nueva (Alto Paraguay Department) and 25 Laguas (Presidente Hayes Department). According to the ecoregion delineation by Olson et al. (2001), the locations are situated in the Chiquitano dry forest (Santa Cruz de la Colina), the Chaco dry forest (La Guardia, Misión Cué, Tribu Nueva) and the Humid Chaco (25 Laguas) ( Fig. 1 View FIGURE 1 ).

In Bolivia, individuals of M. akephaloi sp. nov. were observed foraging diurnally on the ground and leaf litter along the edges of Chiquitano forest fragments that were surrounded by Cerrado-like forests and savanna grass ( Fig. 6A View FIGURE 6 ). Despite several surveys employing beating tray sampling and manual search ( Perger & Perger 2017; Perger & Rubio 2018, 2020a, b), the species was not observed in arboreal habitats or in other Bolivian forest ecoregions. Considering the distribution ( Fig. 1 View FIGURE 1 ) and observations in open habitats, this species is likely typical for Chaco dry forests. Mazax akephaloi sp. nov. is the only species of Mazax that is currently known from Bolivia and Paraguay. This species is possibly replaced by M. ramirezi south of the Chaco area in Argentina (Buenos Aires province), making it unlikely that the latter species occurs in Bolivia (as reported by Perger & Perger 2017).

Ant mimicry. Seven ant species - Ectatomma permagnum Forel, 1908 , Acromyrmex sp. , Odontomachus sp. , Camponotus crassus Mayr, 1862 , C. sericeiventris (Guérin-Méneville, 1838) , Neoponera apicalis (Latreille, 1802) and N. villosa (Fabricius, 1804) - with a similar or larger body length than adults of M. akephaloi sp. nov. (body length 6.23–7.24) were found in the investigated ground habitats in the two Bolivian locations. Among the grounddwelling ants, only the two Neoponera spp. , Odontomachus sp. and E. permagnum had an elongated metasoma.

Characters that increased the ant resemblance in M. akephaloi sp. nov., but were not specific for this mimetic species pair (e.g., also found in the mimetic pair N. villosa and Sphecotypus niger (Perger 2021)) , included long, erected yellowish-brassy setae on the abdomen, a horizontal band of hairs increasing the illusion of an abdominal segmentation between the ant post-petiole and tergite IV, and several transversal bulges posterior to the dorsal sclerite resembling the ant tergites ( Fig. 7 View FIGURE 7 ).

Ethological similarities between E. permagnum and M. akephaloi sp. nov., such as relatively slow foraging speed, with frequent stops in which the ants lifted their heads and conspicuously moved their antennae (imitated by the spiders by moving the prolegs in a similar fashion), were also observed in the mimetic pair N. villosa / S. niger (Perger 2021) and appear to be typical for poneromorph ants and their mimetic spiders.