Chaetacis bandeirante, Magalhães, Ivan L. F. & Santos, Adalberto J., 2011

Magalhães, Ivan L. F. & Santos, Adalberto J., 2011, Two new species and taxonomic notes on the Neotropical spiny orb-weaving spiders Micrathena and Chaetacis (Araneae: Araneidae), with remarks on the development of Micrathena excavata, Zootaxa 2983, pp. 39-56 : 49-53

Chaetacis bandeirante new species

Figures 20–41

Type material. Holotype: male from Usina Hidrelétrica Engenheiro Sérgio Motta, Presidente Epitácio [21º45’S 52º05’W, 310 m], São Paulo, Brazil, Equipe IBSP coll., 16/I–13/II/1999, deposited in IBSP 23255. Paratypes: female from the same locality ( IBSP 160897); two males and four females from the same locality ( IBSP 160898); one male and two females from Base de Pesquisa do Instituto Brasileiro de Desenvolvimento Florestal, Poconé [16º15’S 56º37’W, 142 m], Mato Grosso, Brazil, U.A. Drumond coll., 16/II/1984 ( MZSP 11443); two males and two females from Passo do Lontra, Corumbá [19º0’S 57º39’W, 118 m], Mato Grosso do Sul, Brazil, J. Raizer et al. coll, IV/1998 ( UFMG 4889); one female from Nhecolândia [19º14’S 57º02’S, 86 m], S. Haris coll., 11/XI/1987 ( MNRJ 14587).

Etymology. The specific name honors the bandeirantes, scouts responsible for exploring the interior of Brazil between the 16th and 18th centuries, particularly the regions where C. bandeirante has been recorded.

Diagnosis. Males differ from other species of the genus by the structure of the palp: the tegular projection is strongly bent towards the tibia, almost at a square angle relative to the embolus ( Figs. 22 , 39 ), and the paracymbium retrolateral lobe is large and undulated, with a distinct shape ( Figs. 23 , 40 ). Males also differ from those of C. picta (C.L. Koch) and C. aureola , but not from those of C. necopinata , by having a straight tibia I and seven pairs of abdominal spines ( Figs. 20, 21 ). Females differ from sympatric C. aureola and C. picta by the shape of the abdomen, which is more trapezoidal and elongated ( Fig. 25 ), rather than squarish, and by the cephalic tubercles, which are more spiniform ( Figs. 25, 26 , 33, 34 ), rather than a low tubercle with denticles; it differs from these two species and from C. necopinata by the structure of the epigynum in posterior view ( Figs. 29, 31 , 37 ), which has the sides slightly indented laterally, and by the spermathecae, which are straight with a posterior bend, almost L-shaped ( Figs. 30, 32 , 38 ). Also, C. picta is 12-spined, whereas C. bandeirante is 14-spined ( Fig. 26 ).

Description. Male (holotype). Carapace, chelicerae, legs and abdomen orange brown. Endites, labium and sternum orange brown, darker than carapace. Carapace with a round thoracic groove, one pair of dimples, two pair of sulci, two faint tubercles posterior to the eyes and tiny denticles on the edge of the thoracic area ( Fig. 21 ). First coxa without hook. First tibia straight and with some strong macrosetae, not otherwise modified; other legs without strong macrosetae ( Fig. 20 ). Abdomen rectangular, widest posteriorly, with seven pairs of spines. First, third and fourth pairs of spines orange brown, the remaining black ( Fig. 21 ). Total length, 3.52. Carapace 1.51 long, 1.0 wide at its widest point. Abdomen 1.96 long. Length of first femur, 1.11; patella, 0.42; tibia, 0.9; metatarsus, 0.89; tarsus, 0.42. Second femur, 1.11; patella, 0.37; tibia, 0.81. Third femur, 0.78; patella, 0.26; tibia, 0.46. Fourth femur, 1.24; patella, 0.33; tibia, 0.74; metatarsus, 0.78; tarsus, 0.37. Palp without terminal or paramedian apophysis. Embolus long, sclerotized and slightly curved posteriorly. Conductor with a sclerotized apex, a membranous, digitiform lobe that holds the embolus, and a membranous basal projection. Median apophysis lightly sclerotized, except for a basal sclerite next to the radix, which is dark and tooth-shaped. Tegular projection short and strongly bent towards the tibia ( Figs. 22 , 39 ). Paracymbium with a rounded dorsal lobe and a bifid retrolateral lobe which is highly sclerotized and has a scaly surface ( Figs. 23 , 40 ).

Female (paratype, IBSP 160897). Carapace, chelicerae, labium and sternum dark brown. Endites light brown. Clypeus and legs yellow. Carapace almost glabrous, with a few setae on denticles, a pair of short, yellowish white, spiniform tubercles posterior to the eyes, a circular thoracic fovea, a pair of dimples, two pair of sulci and a high thoracic region ( Figs. 25 , 33, 34 ). Abdomen orange brown with dark markings, subtrapezoidal in form and with seven pairs of spines. Second, fifth, sixth and seventh abdominal spines with dark-colored apices ( Figs. 25, 26 ). Abdominal setae with wide and excavated bases ( Fig. 35 ). Total length, 5.81. Carapace 2.18 long, 1.57 wide at its widest point. Abdomen 3.85 long. Length of first femur, 1.7; patella, 0.63; tibia, 1.29; metatarsus, 1.22; tarsus, 0.54. Second femur, 1.62; patella, 0.59; tibia, 1.11. Third femur, 1.2; patella, 0.39; tibia, 0.68. Fourth femur, 2.28; patella, 0.50; tibia, 1.2; metatarsus, 1.29; both tarsi IV are missing. Epigynum. Epigynal bulge a conical structure, drawn out ventrally ( Figs. 28 , 36, 37 ), slightly indented on sides ( Figs. 29, 31 , 37 ). Copulatory openings small and concealed beneath the lateral plates, which are drawn out posteriorly, forming two keels ( Figs. 36, 37 ). Fertilization ducts short and anteriorly directed, united by a membrane ( Fig. 38 ). Spermathecae reniform, with a short bend on the posterior end ( Figs. 30, 32 , 38 ), and covered with tiny holes, probably glandular openings, visible only under scanning electron microscopy ( Fig. 38 ).

Variation. Some females, especially the ones coming from Xavantina, Mato Grosso, have only six pairs of spines, the third one lacking. These specimens from Xavantina are probably members of this species, but no males have been found to confirm the identification. The shape of the epigynal bulge, especially in posterior view, is variable, but always laterally indented; spermathecae shape is slightly variable. Most males have abdomen homogeneously colored, others have a pattern of dark, dorsal markings resembling that of the females. Males (N=10) vary in total length from 3.3 to 3.59 (mean=3.48); carapace length varies from 1.44 to 1.66 (mean=1.52). Females (N=17) vary in total length from 5.04 to 5.79 (mean=5.45); carapace length varies from 1.86 to 2.19 (mean=2.06).

Notes. Males and females were collected together in three localities: Presidente Epitácio, São Paulo; Poconé, Mato Grosso; and Corumbá, Mato Grosso do Sul. This species appears to be very abundant wherever it occurs, with many individuals collected from each locality.

Natural history. This species has been collected in pantanal (Central Brazil’s floodplains) areas in Poconé, Mato Grosso and Corumbá, Mato Grosso do Sul; it seems to inhabit low elevation habitats (below 400 m).

Distribution. Central Brazil, in states of Mato Grosso, Mato Grosso do Sul and western São Paulo ( Fig. 41 ).

Additional material examined. BRAZIL. São Paulo: Presidente Epitácio [21º45’S 52º05’W, 310 m], Usina Hidrelétrica Engenheiro Sérgio Motta, São Paulo, Brazil, Equipe IBSP coll., 16/I–13/II/1999, 5Ƥ ( IBSP 23262); ditto, 43 ( IBSP 23245); ditto, 13 ( IBSP 23246) ditto, 4m 1Ƥ 1 juvenile ( IBSP 23095); Rosana, Primavera [22º34’S 53º03’W, 236 m], Usina Hidrelétrica Engenheiro Sérgio Motta, Equipe IBSP coll., I– II/2000, 11Ƥ ( IBSP 29792); ditto, 10Ƥ ( IBSP 29905); ditto, 3Ƥ ( IBSP 29986). Mato Grosso: Diamantino [14º25’S 56º27’W, 296 m], Paraguai River Spring, H.F. Japyassú coll., 10/III/2002, 1Ƥ ( IBSP 48633); Indiavaí [15º29’S 58º34’W, 215 m], Sítio Dona Júlia, Rio Sepotuba, J. Raizer coll., 01/III/2002, 2Ƥ ( IBSP 49980); ditto, 4Ƥ ( IBSP 48984); Tapirapé River, 1Ƥ( MNRJ 986); Xavantina [14º40’S 52º50’W, 300 m], H. Sick coll., X/1946, 2Ƥ ( MZSP 1230). Mato Grosso do Sul: Corumbá [19º0’S 57º39’W, 118 m], Passo do Lontra, J. Raizer et al. coll., IV/1998, 13 3 Ƥ 1 juvenile ( IBSP 70752); ditto, 13 2Ƥ ( IBSP 70763); ditto, 13 6Ƥ ( IBSP 70765); ditto, 23 1Ƥ( IBSP 70773); ditto, 33 ( IBSP 70783); ditto, 5Ƥ ( IBSP 70803); ditto, 33 4 juveniles ( IBSP 70843); Ivinhema [22º18’S 53º48’W, 362 m], K. Anjos & F. Fattori coll., 2007–2008, 13 ( IBSP 119947).

Figures

FIGURE 41. Geographic distribution records for Micrathena yanomami new species and Chaetacis bandeirante new species, and new records for M. gaujoni, M. ruschii and C. necopinata.

FIGURES 20 – 24. Chaetacis bandeirante new species. 20 – 23, male holotype. 20 – 21, habitus: 20, lateral view; 21, dorsal view. 22 – 23, left palp: 22, mesal view; 23, retrolateral view. 24, male holotype and female paratype (IBSP 160897) drawn to scale to show sexual dimorphism. Abbreviations: BP = basal projection of the median apophysis, C = conductor, CL = conductor lobe, CM = conductor basal membrane, Cy = cymbium, DL = dorsal lobe of the paracymbium, E = embolus, M = median apophysis, R = radix, RL = retrolateral lobe of the paracymbium, Te = tegular projection, Ti = tibia. Scale bars: 20 – 21, 1 mm; 22 – 23, 0.1 mm.

FIGURES 25 – 32. Chaetacis bandeirante new species. 25 – 30, female paratype (IBSP 160897). 25 – 26, habitus: 25, dorsal view; 26, lateral view; 27 – 30, epigynum: 27, ventral view; 28, lateral view; 29, posterior view; 30, dorsal view, cleared. 31 – 32, female paratype (IBSP 29905). 31 – 32, epigynum: 31, posterior view; 32, dorsal view, cleared. Abbreviations: FD = fertilization ducts, LK = epigynum lateral keels, MP = posterior median plate, PB = spermathecae posterior bend, S = spermathecae. Scale bars: 24 – 26, 1 mm; 27 – 32, 0.1 mm.

FIGURES 33 – 38. Chaetacis bandeirante new species. 33 – 37, female paratype (UFMG 4889). 33, female carapace, dorsolateral view; 34, cephalic tubercle, dorsolateral view; 35, abdominal setal bases, ventral view; 36 – 37, epigynum: 36, ventral view; 37, posterior view; 38, female (IBSP 48980), spermathecae, dorsal view. Abbreviations: B = epigynal bulge, CT = cephalic tubercle, Di = dimple, FD = fertilization ducts, Fo = thoracic fovea, LK = epigynum lateral keels, MP = posterior median plate, PB = spermathecae posterior bend, S = spermathecae, SF = stridulating files of the booklung cover. Scale bars: 33, 1 mm; 34, 35, 38, 0.1 mm; 36, 37, 0.2 mm.

FIGURES 39 – 40. Chaetacis bandeirante new species, male paratype (UFMG 4889). 39, male left palp, mesal view; 40, paracymbium, retrolateral view. Abbreviations: BP = basal projection of the median apophysis, C = conductor, CL = conductor lobe, CM = conductor basal membrane, DL = dorsal lobe of the paracymbium, E = embolus, M = median apophysis, R = radix, RL = retrolateral lobe of the paracymbium, Te = tegular projection. Scale bars: 39, 0.2 mm; 40, 0.1 mm.