Myrmecotypus rubioi, Pett & Perger, 2021

Pett, Brogan L. & Perger, Robert, 2021, Contributions to the knowledge of Neotropical Castianeirinae (Araneae: Corinnidae): redescription of Castianeira spinipalpis Mello-Leitão, 1945, with first description of the male, and description of a new Myrmecotypus O. Pickard-Cambridge, 1894 from the Bolivian Moxos plains, Zootaxa 5082 (2), pp. 145-158 : 153-155

Myrmecotypus rubioi sp. nov.

(LSID: urn:lsid:zoobank.org:act:351AA423-91AC-427E-A60C-86BEA6DD2D0A )

Figs 7 , 8

Type material. Holotype ♂: BOLIVIA: Beni department, José Ballivián province, Espiritu (-14.216, -66.666), vegetation, 9.ix.1986, leg. W. Hanagarth & J. Sarmiento ( SMNK-ARA 13318 ).

Other material examined. 1 subadult ♂, 1 subadult ♀: same data as holotype ( SMNK-ARA 13318 ) .

Diagnosis. Myrmecotypus rubioi sp. nov. is distinguished from all other congeners by having tibia I spination of 3-2 and coxa II white (the remaining coxae dark) ( Figs 7A–C ). Additionally, the new species has a unique male palpal embolus with two broad embolic discs basal to embolus tip ( Figs 8A, B ), subapical disc well-sclerotized, forming part of the embolus, turning 1.5 times to a tapered, retrolaterally-directed point; and the RTA sharp, thornlike, ventrally projected ( Fig. 8B ).

Remarks. Rubio & Arbino (2009) and Perger & Rubio (2020a) hypothesized that some Neotropical species of Apochinomma Pavesi, 1881 may belong to Myrmecotypus . Amongst those species, A. formicoides Mello-Leitão, 1939 is the only species with a sub-globose abdomen and light coxa II (remaining coxae dark) ( Mello-Leitão 1939). Unfortunately, the female holotype of A. formicoides was not available for study, and it is probably lost ( World Spider Catalog 2021; A. Kury, pers. comm.). According to the description and illustration that were provided by Mello-Leitão (1939), A. formicoides can be distinguished from M. rubioi sp. nov. by a carapace index of ~42 (59 in the new species), the cephalic area with lateral borders subparallel (narrowing in anterior direction in the new species), and tibia I spination of 3-3 (3- 2 in the new species).

Etymology. The species epithet is a genitive patronym in honour of Argentinian arachnologist, Dr. Gonzalo D. Rubio ( Argentina), for his substantial contributions to the knowledge on Neotropical ant-like spiders.

Description.

Measurements. Total length 3.63. Carapace: length 1.74, width 1.03, index 59, height 0.67. Cephalic region: width 0.62, index 60. Abdomen: length 1.80 (1.89 incl. pedicel), width 1.10, index 58. Sternum: length 0.81, width 0.60, index 74. Chelicerae: length 0.51, width 0.35. Eyes: AME 0.09, ALE 0.06, PME 0.07, PLE 0.06. Legs: I = 3.04 (0.82, 0.32, 0.81, 0.62, 0.47); II = 3.11 (0.81, 0.30, 0.75, 0.67, 0.58); III = 2.73 (0.78, 0.26, 0.68, 0.63, 0.38); IV = 4.25 (1.20, 0.38, 1.04, 1.05, 0.58).

Carapace: Broad oval-shaped dorsally ( Fig. 7A ), subtruncate anteriorly. Deep reddish-brown, with longish simple white hairs laterally and frontally, absent medially. No depression, highest point just posterior to fovea, slope towards cephalic region very gentle, slope posterior towards pedicel abrupt ( Fig. 7B ). Sparse short setae near lateral margins.

Sternum: Concolorous with carapace, roughly shield-shaped, parallel straight lateral margins at region of coxae II ( Fig. 7C ). Short, fine silver setae present, sparse. Anteriorly truncated. Coxae II white, other coxae dark brown, right coxae III with lighter basal 1/3 and may be aberrant.

Eyes: AER weakly recurved, AME about 2x larger than ALEs, ALE and PME clearly the smallest eyes. PER almost straight, weakly recurved in dorsal view, very weakly recurved in frontal view. AME clearly larger than other eyes. Long ocular setae.

Legs: Legs I and II light yellow, with femora I and II with basal 1/3 dark, legs III and IV dark brown to reddish, with basal ½ of patellae III and IV light yellow. Femora with pair of strong dorsal spines, basal one about twice as long and thicker (spines on femora III and IV about ½ femur length). Basal portion of femora with mix of very short fine simple and feathery silver setae, more abundant on F III and IV. Tibia I with 3-2 spines, metatarsus I with 2-2 tibial spines.

Chelicerae: Lighter than carapace, orange. Two small teeth on retromargin, distal one slightly larger, two teeth on promargin, distal one about twice the size of basal tooth, both promarginal teeth larger than retromarginal teeth. One tiny denticle more distal than distal tooth on promargin.

Abdomen: Pyriform, broadest at posterior half, without constriction ( Figs 7A–C ). Deep red, darkest at anterior 1/3. Lateral regions not covered by sclerites, pale orangish-brown. Dorsal sclerite covering 4/5 of dorsum, moderately shiny, with sparse shallow punctures. Short, feathery fine silvery setae throughout, sparser further from anterior portion, long and straight erect simple white setae sparse dorsally, density highest in indistinct band at ¼ abdomen length. Two pairs of thick pedicellate setae, first pair at anterior margin of dorsum, rising at 10’30 position, just posterior to this are a second thicker and spine-like pair, projecting at 1 o’clock position. Venter with sclerite occupying middle ½, barrel-shaped, with wide posterior margins and recurved posterior edge. Small wedge-shaped inframamillary sclerite just anterior to spinnerets. Ventral and inframamillary sclerites light reddish-orange. Wellsclerotized full epigastric sclerite wrapping around pedicel and anterior portion of abdomen. Lateral regions not covered by sclerites, pale orangish-brown.

Palp: Bulb drawn out into long neck that weakly narrows medially before broadening towards apex. Basal ridge of embolic region obvious as retrolateral protrusion, one broad unsclerotized basal embolic disc proximal to sclerotized embolus. Distal sub-apical disc sclerotized and forms embolus, with retrolaterally directed apex, turning 1.5 times. Sperm duct with two median loops and one more distal lateral loop on retrolateral side. Sharp thorn- like ventrally directed RTA. Long prolateral spine on palpal tibia ( Figs 8A, B ).

Leg spination: I: F = d3 pl1, T = plv3 rlv2, Mt = plv2 rlv2; II: F = d2, P = d1, T = rlv2 plv2, Mt = rlv2 plv2; III: F = d2 pl1, P = d1, T = pl2 rl2 plv2, Mt = plv2 rlv2, 1 distal whorl; IV: F = d2, T = pl2 rl2 plv1, Mt = d1 pl2 rl2 plv2 rlv1, 1 distal whorl.

Geographical and ecological distribution. This species is only known from the type locality in Espiritu, José Ballivián province, Beni Department, Bolivia. According to the ecoregion delineation by Olson et al. (2001), the locality is situated in Beni savanna (widely recognized as Moxos Plains Flooded Savannas (see Ibisch & Merida 2003). This savanna is comprised of a mosaic of grasslands, swamplands and forest islands ( Navarro & Ferreira 2011). Based on the approximated GPS data of the collection locality (according to the information by the owner of Espiritu Ranch), it was not possible to determine the accurate ecosystem or habitat associations of M. rubioi sp. nov. Further studies are needed to determine this.

Ant mimicry. In the other Bolivian species of Myrmecotypus , the colour of body parts and the colour and distribution of setae increases the resemblance to specific ant models of the tribes Camponotini or Dolichoderini ( Perger & Rubio 2020a, 2021a). Unfortunately, the live habitus of M. rubioi sp. nov. and co-occurring ants were not documented and the loss of setae due to the storage in ethanol hampered the assessment of mimetic relationships. However, as in other congeners, the body size, sub-oval carapace and abdomen mostly resemble ants of Camponotini or Dolichoderini. Additional field observations are needed to identify potential ant models.

Figures

FIGURE 7. Myrmecotypus rubioi sp. nov., holotype male habitus (SMNK-ARA 13318): A dorsal; B lateral; C ventral. Please note that most setae are broken off due to storage in ethanol. Scale bar = 0.5 mm.

FIGURE 8. Myrmecotypus rubioi sp. nov., male holotype (SMNK-ARA 13318), palp in ventral (A) and retrolateral (B) views. Abbreviations: BR—basal ridge of embolic region, e—embolus, PDe—proximal disc of embolus, RTA—retrolateral tibial apophysis, SaDe—subapical disc of embolus, SD—sperm duct. Scale bar = 0.2 mm.