Myrmecotypus mboitui, Pett, 2021

Pett, Brogan L., 2021, Description of a new species of Myrmecotypus (Araneae: Corinnidae Castianeirinae), the first of its genus known from Paraguay, with an updated key to species, Zootaxa 4999 (1), pp. 77-86 : 79-84

Myrmecotypus mboitui sp. nov.

http://zoobank.org/627346e8-3f20-4de6-825d-60fd95f0f7ed

Figs 3–11

Type material. Holotype ♂ from PARAGUAY: Ñeembucú, Estancia Santa Ana (-26.8456°, -58.0309°), 61 m a.s.l., 7–13.II.2020, pitfall traps in grassland, Humid Chaco ecoregion, leg. B.L. Pett & R. Wyer (CIPLT-Ar 301).

Paratypes: PARAGUAY: Ñeembucú, Estancia Santa Ana, 3–9.XII.2019, Pitfall traps, “Hygrophilous forest edge”, leg. B.L. Pett & R. Wyer , 1♀ (CIPLT-Ar 303); Same locality, 30.I–6.II.2020, Pitfall traps, “Grassland”, leg. B.L. Pett & R. Wyer, 2♀ (CIPLT-Ar 300) .

Other material examined. PARAGUAY: Ñeembucú, Estancia Santa Ana , 3–9.XII.2019, Pitfall traps, “Edge”, leg. B.L. Pett & R. Wyer, 1♀ (CIPLT-Ar 306) .

Etymology. The species epithet refers to the Guaraní mythological figure, Mbói tu’ĩ, the second cursed child of Tau and Kerana, protector of wetlands and swamps, who takes the form of an enormous serpent with a parrot’s head (Mbói = parrot, tu’ ĩ = snake). Reference is made to the discovery of this species in a wetland region.

Diagnosis. Within Myrmecotypus , M. mboitui sp. nov. shares an elongated and constricted abdomen ( Fig. 4 ) with only M. mazaxoides and M. lineatus (Emerton, 1909) (cf. Reiskind 1969: 309, figs 154, 155, male unknown; Perger & Dupérré 2021: figs 2, 3). These three species also share a broad carapace index and subequal eyes. Males of the new species are easily recognised by characters of the male palp, with the largest pair of RTAs known in the genus (in ventral view), and an embolus with four and a half coils ( Figs 9–11 ). Females have COs that are situated just anterolaterally of the ST II ( Figs 12, 13 ). Additionally, specimens of M. mboitui sp. nov. have a distinctly orange-tinted carapace (especially in females), that is unique in the genus.

Females of M. mboitui sp. nov. can be readily distinguished from those of M. lineatus by tibia I ventral spination 3-2 ( Reiskind 1969) (2- 2 in M. lineatus ), coxae II–IV pale (all coxae pale in M. lineatus ), weakly constricted abdomen (strongly constricted in M. lineatus ), and position of COs slightly anterolateral to the spermathecae (posterior in M. lineatus ).

Myrmecotypus mboitui sp. nov. shares further characteristics with M. mazaxoides : tibia I ventral spination 3-2, two promarginal teeth and one retromarginal tooth, and size of female dorsal sclerite, as well as sexual dimorphism of the coxal colouration (II and III pale in male, II–IV pale in female) ( Figs 3 , 7 ). These two species can be reliably separated on the basis of genitalic characters: males of M. mboitui sp. nov. with two large pointed RTAs; the dRTA more distally oriented, with a tip recurving very weakly back towards the palp, almost tooth-like, and the vRTA projected disto-laterally at 10:30 position (in M. mazaxoides the RTA are substantially smaller, with the dRTA pale, with a translucent border, and the vRTA stub-like). The embolus of M. mboitui sp. nov. has four and a half coils (in M. mazaxoides there are only three coils), and the embolic base is more basally situated in M. mboitui sp. nov. (vs more distal in M. mazaxoides ). The dorsal abdominal sclerite of males also appears shorter in M. mboitui sp. nov., with the posterior 1/5 th of the dorsum exposed, while in M. mazaxoides the sclerite almost covers the entire dorsal surface of the abdomen. Females may be separated by the CO’s situated only slightly antero-laterally to the ST II, with relatively shorter CDs (vs COs anterior to ST II, with much longer CDs in M. mazaxoides ).

Notes. Whilst the general colouration of the carapace is orange-tinted in M. mboitui sp. nov. (including in fresh specimens, i.e. the orange colouration is not a result of ethanol storage) and much darker brown to black in M. mazaxoides , this character is tentatively assigned as diagnostic. Castianeirines are known to exhibit some colour polymorphisms (e.g. Haddad & Louw 2012; Sankaran et al. 2015), but this has not been reported for Myrmecotypus before. This may be due to the specific rather than general mimicry exhibited by Myrmecotypus , potentially constraining any intraspecific colour variation.Additionally, one female was not designated as a paratype, due to having the abdomen and carapace detached, as well as the legs dissected; this specimen is depicted in Figs 7 and 8 .

Taxonomic notes. Reiskind (1969) noted the distinctness gof M. lineatus when transferring this species from Castianeira Keyserling, 1879 to Myrmecotypus . The general habitus of M. mboitui sp. nov. and M. mazaxoides resembles that of species of Mazax and possibly of some Apochinomma Pavesi, 1881 species (for M. mazaxoides , see Perger & Dupérré 2021). Rubio & Arbino (2009) referred to the resemblance between Myrmecotypus and Apochinomma . While the Afrotropical species of Apochinomma have been revised by Haddad (2013), the generic placement of the Neotropical congeners remains uncertain. Rubio & Arbino (2009) questioned whether Apochinomma is present in the Neotropical region, suggesting that some Neotropical species of this genus may belong to Myrmecotypus . From the Neotropics, nine species of Apochinomma have been described, eight from Brazil and one from Guyana ( World Spider Catalog 2021). Apochinomma acanthaspis Simon, 1896 (BL female type 5 mm), A. armatum Mello-Leitão, 1922 (BL female type 5 mm), A. constrictum Simon, 1896 (BL female type 5.2 mm) and A. pyriforme ( Keyserling, 1891) (BL female type 6.7 mm) have an elongated, constricted abdomen. However, A. acanthaspis and A. armatum have the second pair of setae on the dorsal abdominal sclerite sclerotized to spines, indicating that both may belong to Mazax ( Perger & Rubio 2020 a) . Apochinomma constrictum has all of the coxae red-brown and lacks transverse bands of setae, and A. pyriforme can be distinguished by the AME as twice as large as the posterior eyes (PE), the PE larger than the ALE, the PER straight and comparably narrow (typical arrangement for Castianeira ), and the femora II–IV yellow (see Keyserling 1891).

Description. Male (holotype: CIPLT-Ar 301), Figs 3 & 4 .

Colouration: Carapace dark orange to brown with black mottling, almost entirely black laterally and frontally. Short white setae sparse at frontal 1/3 of carapace, moving to relatively uniform frontally. Darkest part of carapace at base of chelicerae. Legs dark orange to brown, granulate, with longitudinal stripes yellow to clear, coxa I dark brown, IV light brown, rest white to yellow. Sternum orange-brown with mottled black patches. Abdomen uniform black, deep red-brown at base. Carapace: Oval, about twice longer than wide. Highest point at fovea and cephalic region, sloping proximally toward base in lateral view. In ventral view, carapace moderately truncated anteriorly, with weak curve around cephalic region. Sternum: Distinctly shield-shaped, dark orange-brown with black mottling, granulated, widest between coxae I and II. Anterior ridge recurved. Eyes: AER recurved, with ALEs nearly touching AMEs. PER nearly straight, with eyes evenly spaced, PMEs smallest. Legs: Femur II, III and IV with strong, long dorsal spine, femur spine IV longer than spine on femur III, that on III longer than on II. Femur I without such a spine. Chelicerae: With small lateral condyle. Two teeth on retromargin, with basal tooth double the size of distal tooth. Promargin with two teeth, distal one larger and basal one much smaller. Abdomen: Substantially longer than wide, dorsal sclerite convex and covering over 2/3 of abdomen, shiny and granulated. Pair of spines at anterior part of sclerite straight to moderately curved backwards. Clear constriction of abdomen around 1/3 of length, substantial when viewed laterally, ring of sparse white longitudinally flattened short setae in area of constriction. Concave subrectangular ventral sclerite covering half of venter, with concentrated patches of short, feathery white setae in lateral anterior corners at margins of epigastric furrow. Abdominal petiole rugose and well sclerotized. Inframamilliary sclerite very small, dark brown, epigastric sclerite anteriorly forming petiole, deep red to black. Palp: Spination: femur = v 2, patella = v 2 pl 1, tibia = v 1 pl 1 with 9 erect setae plv. Tibial spines substantially larger than others, with pl spine about 1.5 times the length of pl ventral spine. Palpal bulb with median basally convoluted loop of sperm duct, as well as a lateral loop close to retrolateral margin of bulb in ventral view. Palpal tibia with two pointed and relatively large retrolateral apophyses, ventral one projected disto-laterally at 10:30 position; dRTA shorter and more distally oriented, with tip recurving back towards palp. Embolus relatively thick, with four and a half coils, giving screw-like appearance.

Leg spination: Leg I: F = pl1 d1, Ti = v = 3-2 (plv 3 rlv 2), mt = 2-2 (plv 2 rlv 2). Leg II: F = d3, Ti = 2-2 (plv2 rlv2), mt = 2-2 (plv2 rlv2) Leg III: F = pl2 d1, P = d1, Ti = pl2 d1 rl1, mt= 2- 2-2 (pl2 rl2 plv2 rlv2) 1 distal whorl, Leg IV: F = d1 pl2, Ti = pl1 rl1 v1 d1 1-1 (plv1 rlv1), mt = d2 2-2 (plv2 rlv2) 1 distal whorl.

Measurements: Total length 4.84, carapace length 2.14, carapace width 1.09, carapace index 51, carapace height 0.94, cephalic width 0.66, cephalic index 61, abdomen length 2.71 (incl. pedicel), abdomen width 1.04, abdomen index 38. Sternum length 1.09, sternum width 0.68, sternum index 62. Chelicera length 0.52, width 0.26. Legs. I: 1.04, 0.31, 0.83, 0.52, 0.73; II: 0.94, 0.34, 0.89, 0.89, 0.62; III: 0.89, 0.36, 0.52, 0.88, 0.57; IV: 1.46, 0.42, 1.30, 1.46, 0.73. Eyes: AME 0.09, ALE 0.08, PME 0.08, PLE 0.07.

Female (Paratype CIPLT-Ar 303), Figs 5–8 .

Habitus shape, leg formula, spination and general colour pattern as in male, except for light coxa IV (light brown in male). Carapace brighter orange, darker in cephalic area, extensive black patches laterally converging at fovea in ‘V’ pattern, two orange spots at lateral margins of black V in line with leg I. PME small, appearing 3x the distance to PLE as distance between AME and ALE in dorsal view, posterior eyes recurved in dorsal view, with very sparse fine white setae around cephalic area. Abdomen with bronze sheen but primarily grey. Dorsal sclerite small and circular, deep purple with weak brown mottling, covering around ¼ of abdomen length. Three narrow bands of low density short white feathery setae run transversely across abdomen: at site of constriction, 1/3 along dorsal sclerite, and at about 3/4 the length of the abdomen.

Epigyne: External epigynal field wider than long by about 1.5x. Copulatory openings positioned just anterolaterally to ST II. Spermathecae asymmetrical, ST II(L) appears more slanted in comparison to ST II(R), i.e. ST II(R) extends more apically and at steeper angle, whereas ST II(L) posterior edge is more lateral and at point of convergence with ST II(R), and is not as anteriorly produced. Dorsally, cleared epigyne simple, CD barely visible, even under high magnification, very short. FD very small.

Leg spination: Leg I: F = pl1 d1, Ti = v = 3-2 (plv 3 rlv 2), mt = 2-2 (plv 2 rlv 2). Leg II: F = d2, Ti = 2-2 (plv2 rlv2), mt = 2-2 (plv2 rlv2). Leg III: F = pl2 d1, P = d1, Ti = pl2 d1 plv2 rlv1, mt = 2-2-2-2 (pl2 rl2 plv2 rlv2) 1 distal whorl. Leg IV: F = d2 (additional small spines d1 pl1), Ti = pl2 rl1 d1 v1-1-1 (v1 plv1 rlv1), mt = d2 v2-2-2 (v2 plv2 rlv2) 1 distal whorl.

Measurements: Total length 6.15, carapace length 2.54, carapace width 1.26, carapace index 50, carapace height 0.88, cephalic width 0.87, cephalic index 69, abdomen length 3.61 (incl. pedicel), abdomen width 1.57, abdomen index 43, sternum length 1.22, sternum width 0.76, sternum index 62. Chelicera length 0.78, width 0.42. Legs. I: 1.49, 0.47, 1.18, 1.09, 0.88. II: 1.47, 0.46, 1.08, 1.16, 0.76. III: 1.39, 0.42, 1.01, 1.09, 0.54. IV: 2.10, 0.59, 1.64, 1.93, 0.88. Eyes: AME 0.09, ALE 0.08, PME 0.08, PLE 0.08.

Natural history. Specimens were all caught with pitfall traps between December and February. The species is a formicine ant mimic (likely Camponotini) but no data was collected on potential ant models. Interestingly, this is only the second known ground- dwelling congener (alongside M. mazaxoides ).

Figures

FIGURES 3–4. Myrmecotypus mboitui sp. nov. male holotype: 3 Carapace in dorsal view; 4Abdomen in dorsal view. Scale bar = 1mm. Note: anterior abdominal spines broken due to storage.

FIGURES 5–8. Myrmecotypus mboitui sp. nov. female paratype (5, 6) and non-type (7, 8): 5 Habitus in dorsal view; 6 Habitus in lateral view; 7 Carapace in ventral view; 8 Abdomen in ventral view. Scale bar (5) = 1 mm. Note: anterior abdominal spines broken due to storage.

FIGURES 9–13. Copulatory structures of Myrmecotypus mboitui sp. nov. male (9–11) and female (12, 13): 9 Pedipalp, prolateral view; 10 Same, ventral view; 11 Same, retrolateral view; 12 Epigyne, dorsal view; 13 Epigyne, ventral view. Scale bars: 9, 10, 11 = 0.5 mm; 12, 13 = 0.25 mm.Abbreviations: CO = copulatory openings; dRTA = dorsal retrolateral tibial apophysis; E = embolus; FD = fertilisation ducts; SD = sperm duct; ST = spermathecae; vRTA = ventral retrolateral tibial apophysis. Note: Fig. 13 depicts the ventral view of an epigyne that has been very slightly digested in KOH, reducing the high amount of chitinous build up on the COs, to clarify their position and shape.