Eutichurus ibiuna Bonaldo, 1994

Laborda, Álvaro & Simó, Miguel, 2015, Description of the female of Eutichurus ibiuna Bonaldo, 1994 (Araneae: Eutichuridae) with notes on natural history and sexual behavior, Zootaxa 4021 (4), pp. 591-596 : 591-595

Eutichurus ibiuna Bonaldo, 1994

Figs 1– 4

Eutichurus ibiuna Bonaldo, 1994: 125 , figs 62–64 (male holotype from Ibiúna , São Paulo, Brasil, IV.1975, J. Talarico leg., deposited in IBSP 2750/16268, not examined).

Material examined. URUGUAY. Cerro Largo: Rute 26, approximately 12 km from Arroyo Bañado de Medina, on a road sign (S32.3654°, W54.4756°), 15.III.2013, M. Simó and Á. Laborda, 1 female (FCE-Ar 4707). Treinta y Tres: Quebrada de los Cuervos, near the park-rangers’ house, under the bark of an Eucalyptus tree, with ootheca (S32.9070°, W54.4463°), 15.XII.2013, Á. Laborda, 1 female (FCE-Ar 4809); same locality (bred in the laboratory, offsprings of female FCE-Ar 4809), 6 males, 6 females (FCE-Ar 6203–6214).

Diagnosis. Males of E. ibiuna differ from those of E. luridus Simon, 1897 by the presence of a simple RTA and from those of other species of Eutichurus with simple RTA by the embolus with a retrolateral apical process ( Bonaldo 1994) ( Fig. 1 A). In females, the shape of the epigynum of E. ibuna resembles those of E. ferox Simon, 1897 , E. silvae Bonaldo, 1994 and E. tropicus (L. Koch, 1866) , but can be distinguished from those of E. ferox and E. tropicus by the presence of the atrium groove, and from that of E. silvae by the atrium as long as wide and the posterior plates more laterally expanded ( Fig. 1 D).

Description. Female (FCE-Ar 4809). Coloration: prosoma caramel-colored with slightly darker ocular region ( Fig. 2 B); chelicerae dark brown, with three equal sized teeth on the retromargin and five on promargin, second basal tooth larger; labium and endites dark brown, sternum brown; legs beige yellowish; opisthosoma yellowish. Legs spination: Ifemur d 1-1 or 0-1, p 1ap; tibia v 0-p1-0; metatarsus v 2 -p1- 1. II— femur d 1-1, p 1ap; metatarsus v 2 -p1-1 or 2-0- 1. III— femur d 1-1-1 or 1-1-0, p 1-1 or 1-2, r 0-0-1 or 1-1-1; tibia v p1-2-0 or p1-p1-p1, p 1-1, r 1-1 or 0-1; metatarsus v 2- 2 -1 or 2-r1-1, p 1-1-1-2 or 1-1-2, r 1-1-2 or 2ap. IV— femur d 1-1, p 1-1 or 0-1 r 1ap; tibia v p1-2-0, p 1-1, r 1-1; metatarsus v 2-2 -1, p 1-1-2, r 1-1-2. Measurements. Total length 13.73; prosoma (length/width) 6.00/5.20; opisthosoma (length/width) 7.73/5.33; sternum (length/width) 2.67/2.27; labium (length/width) 1.20/1.07; clypeus height 0.13. Posterior lateral spinnerets: basal article 0.80, distal article 1.60. Eyes: anterior row 2.48, posterior 2.76; diameters and interdistances: AME 0.36, ALE 0.28, PME 0.20, PLE 0.24, AME–AME 0.28, AME–ALE 0.44, PME–PME 0.60, PME– PLE 0.68. Chelicerae (length/width): 3.33/1.60. Legs: I—femur 4.53/ patella 2.13/ tibia 4.00/ metatarsus 4.13/ tarsus 1.73/ total length 16.53; II—4.13/2.13/4.00/3.73/1.60/15.59; III—3.20/1.60/2.40/2.80/1.33/11.33; IV—4.67/2.00/3.60/ 4.13/1.73/16.13. Epigynum ( Fig. 1 D, E): atrium subsquared, as long as wide, with a medium longitudinal groove; anterior lobes as long as wide, with squared apex; posterior plates wider than longer, non fused; spermatheca anteriorly prolonged, with a short stalk widened at the apex. Male ( Figs. 1 A, B, C; 2A): described by Bonaldo (1994: 125).

Variation. (range, mean±s.d.) Females (N=5): TL 12.00–13.00, 12.50±0.41; PL 5.30–5.90, 5.70±0.24; PW 4.10– 4.70, 4.38±0.22; Males (N=5): TL 9.90–10.80, 10.18±0.36; PL 5.00–5.50, 5.24±0.24; PW 3.60–4.00, 3.76±0.18.

Distribution. Known from State of São Paulo, Brazil and Departments of Cerro Largo and Treinta y Tres, Uruguay ( Fig. 3 ).

Natural history. We observed at the field and under laboratory conditions that all E. ibiuna individuals, no matter the developmental stage or sex, built a sac-like silken retreat, where they spent most of the time ( Fig. 4 A). This behavior was reported by Bonaldo (1994) who observed young individuals of Eutichurus at the field occupying silken nests inside dead leaves. The construction of retreats is known for other Eutichuridae , such as Cheiracanthium C. L. Koch, 1839 and is also usual in the family Clubionidae ( Dondale & Redner 1982; Pollard & Jackson 1982). At the field, one specimen was found under bark of Eucalyptus sp. near a house and the other was collected at a road sign. Bonaldo (1994) reported specimens of Eutichurus silvae Bonaldo, 1994 , E. valderramai Bonaldo, 1994 and E. lizeri Mello-Leitão, 1938 in human constructions. This suggests that some species of the genus have the ability to inhabit anthropic environments.

Sexual behavior. The male initiated courtship after contacting the female silk, indicated as level 2 in Foelix (2011). The male approached the female sensing the substrate with palps and legs I, while vibrating the abdomen. After contacting the female the mount occurred very quickly. They adopted the typical mating position of wandering spiders, type 3 in Foelix (2011) ( Fig. 4 B). Then the male started to lay silk over the legs I, II and palps of the female ( Fig. 4 C). During mating the male continued vibrating the abdomen. In all cases it was observed that the male inserted a palp two times on a side, and then switched to the opposite side where he performed other two palpal insertions. Mating duration was 53±25 minutes (mean±s.d.; N=3) and always occurred inside or near the female retreat. Bonaldo (1994) reports the occurrence of genital plugs in Eutichurus and Radulphius . We also found plugs in the females collected in the field and in the three that copulate in the laboratory, but the deposition of plugs was not witnessed during the mattings. The bridal veil is defined as the release of silk threads by the male over the female during courtship or copulation ( Bristowe 1958), which is consistent with the observed behavior in this species. Thus, this is the first report of bridal veil in Eutichuridae . It appears to be a widespread behavior in spiders, since it has been reported for several species from different families ( Aisenberg et al. 2008; Schmitt 1992), including other dionychans, as Thomisidae ( Bristowe 1958) . Future studies could be focused in the possible role of this behavior in the phylogeny of spiders.

Figures

FIGURE 1. Eutichurus ibiuna, genitalia: A left palp, prolateral view; B same, ventral view; C same, retrolateral view; D epigynum, ventral view; E cleared vulva, dorsal view. Abbreviations: A = atrium; AE = apical spermatheca; AL = anterior lobe; BE = basal spermatheca; E = embolus; EP = embolar process; FD = fertilization duct; PP = posterior plate; RTA = retrolateral tibial apophysis.

FIGURE 2. Live specimens of Eutichurus ibiuna: A male (FCE-Ar 6204); B female (FCE-Ar 4809).

FIGURE 3. Geographic distribution of Eutichurus ibiuna: literature record = blue circle; new records = red circles.

FIGURE 4. Eutichurus ibiuna, behavior: A juvenile in its silk retreat; B mating position; C couple during mating (note the silk deposited by the male over the female).