Chrysso intervales, Gonzaga & Leiner & Santos, 2006

Gonzaga, Marcelo O., Leiner, Natália O. & Santos, Adalberto J., 2006, On the sticky cobwebs of two theridiid spiders (Araneae: Theridiidae), Journal of Natural History 40 (5 - 6), pp. 293-306 : 296-300

Chrysso intervales new species

( Figures 2–7 )

Type material

Male holotype from Parque Estadual Intervales, Ribeirão Grande , State of São Paulo, 24 u 169S, 48 u 259W, 10 March 2005, M. O. Gonzaga and N. Leiner coll., in IBSP 52232 . Female paratype from the same locality and collectors, 20 March 2005, in IBSP 52233 .

Diagnosis

Chrysso intervales shares with several other species currently assigned to Chrysso the abdomen with a posterior hump and the male palpus with a large subtegulum, a retrolaterally positioned tegulum, and a long embolus and conductor ( Figures 2–4 , see also Levi 1962). The males can be distinguished from other species by the cymbium which is narrower in the apical half, the embolus with a large base and a thin apex, and the presence of two small sclerites close to the subtegulum ( Figures 3, 4 , see comments below). Females can be recognized by the epigynum which is widely excavated medially, and with a ventrally projecting posterior margin ( Figures 5, 6 ). The internal female genitalia shows two spermathecae close to the copulatory openings, which are located at the anterior corners of the medially excavated area ( Figure 5 ), and a long, sinuous and posteriorly closed cavity ( Figure 6 ).

Comments

Judging by their position, at least one of the small sclerites in the male palpus is certainly a median apophysis; the other is probably homologous to the radix of other species of Chrysso ( Levi 1962) . The radix is currently recognized as a structure exclusive to Araneidae ( Griswold et al. 1998) , and the sclerites commonly referred to as a radix in theridiid palps are certainly homologous to other structures, mainly the Theridiid Tegular Apophysis (see Agnarsson 2004). In the case of C. intervales , it is possible that the two sclerites are actually part of a median apophysis with two large branches, deeply connected inside the bulb, as occurs in Chrysso nigriceps ( Agnarsson 2004, Figure 39B).

Description

Male (holotype). Carapace oval, orange. Thoracic groove longitudinal, conspicuous. Anterior median eyes subequal to other eyes, 2.0 diameters apart, 1.0 from anterior lateral eyes. Posterior median eyes 2.0 diameters apart, 1.5 from posterior laterals. Lateral eyes contiguous. Clypeus orange. Chelicerae, labium, and endites cream coloured. Chelicerae with two posterior teeth. Sternum orange. Palpi cream coloured, cymbium brown. Legs cream, metatarsi and tarsi orange. Legs III and IV with a retrolateral dusky stripe on the apical half of femur, patella, and tibia. Abdomen white dorsally, covered with dark grey spots and with a black posterior mark. Epigastric plate and spinnerets orange. Total length 2.6. Carapace 1.0 long, 1.0 wide. Femur I 1.8, tibia-patella 1.6, metatarsus 1.5, tarsus 0.9. Tibia-patella II 1.1, III 0.8, IV 1.3. Abdomen 1.6 long, 1.0 wide. Cymbium narrowed apically, folded over the fovea. Subtegulum large, with the prolateral posterior corner unsclerotized ( Figure 3 ). Tegulum restricted to the retrolateral side of the bulb, with sperm duct visible by transparency ( Figure 4 ). Theridiid tegular apophysis not visible. Conductor hyaline, wrapping the embolus apex. Embolus base large, partially hidden under the tegulum ( Figure 3 ).

Female (paratype). Carapace oval, cream coloured, with pars cephalica orange. Anterior median eyes subequal to other eyes, 1.0 diameters apart, 0.5 from anterior laterals. Posterior median eyes 2.0 diameters apart, 1.0 from posterior laterals. Lateral eyes contiguous. Clypeus, chelicerae, labium, and endites orange. Chelicerae with two teeth on posterior margin. Sternum cream, palpi orange. Legs orange, with a retrolateral dark stripe on apical fourth of femur and patella IV. Abdomen cream, with a dorsal longitudinal band of dark grey spots and a median and a lateral pair of white spots on anterior and posterior thirds. Spinnerets cream. Total length 3.6. Carapace 1.0 long, 1.1 wide. Femur I 2.1, tibiapatella 2.0, metatarsus 1.6, tarsus 1.4. Tibia-patella II 1.3, III 0.9, IV 1.4. Abdomen 2.6 long, 1.7 wide. Copulatory openings in the lateral corners of the epigynum, marked by discrete sclerotized rims ( Figure 5 ). Copulatory ducts short, with copulatory openings almost directly connected to spermathecae. Spermathecae spherical, fertilization ducts thin, medially directed and gently curved ( Figure 7 ).

Variation

Females, total length 3.8–4.6, carapace width 1.0–1.2 (N 510).

Etymology

The specific name is a noun in apposition taken from the type locality.

Distribution

Known only from the type locality.

Additional material examined

Brazil: São Paulo: Ribeirão Grande, Parque Estadual Intervales , February 2004, M. O. Gonzaga coll., nine females ( IBSP 52234 ) .

Remarks

We did not find any specimens of H. longicauda or C. intervales at the sites located away from the rivers. However, both species were especially abundant at site 7 and were also present on other sites located close to the water courses ( Table I). The measurements at site 7 showed that the relative humidity in that area remained constantly high (.90%), even during the winter (dry season) ( Figure 8 ). In addition, our measurements at the other sites indicate that relative humidity is generally higher close to the rivers (Table II). One-tailed Fisher’s exact tests comparing the presence of each species at humid versus dry places showed that preference for humid areas was significant ( H. longicauda , P 50.03; C. intervales , P,0.01).

Webs of H. longicauda and C. intervales were always under large more or less horizontal leaves (X¯¡SD5343.6¡ 276.9 cm 2, n 523 for H. longicauda ; X¯¡SD5465.6¡ 299.7 cm 2, n 518 for C. intervales ). The webs consisted of an area with a relatively high thread density close to the spider’s resting position, and several more or less vertical threads extending to other leaves directly below ( Figures 9–12 ). The distance between the upper and the lower leaves to which the web was attached was higher in C. intervales (X¯¡SD529.5¡ 8.5 cm, n 518) than in H. longicauda (X¯¡SD521.0¡ 8.4 cm, n 523) (t test, t 523.18, df539, P 50.003). The webs of both species consisted entirely of viscid silk lines.

The density of viscid droplets was slightly higher on the threads located close to the spider’s position (X¯ 1 ¡SD58.1¡1.29 droplets per 0.5 mm of thread) than in the middle segment between the two leaves (X¯ 2 ¡SD57.0¡0.94) in H. longicauda (paired t test, t 521.88, df59, P 50.047). The same pattern was observed in C. intervales (X¯ 1 ¡SD57.5¡1.83 droplets per 0.5 mm of thread, X¯ 2 ¡SD56.5¡1.98; paired t test, t 521.82, df511, P 50.048). The mean diameter of droplets did not differ between the two areas of the webs in either H. longicauda (X¯ 1 ¡SD520.6¡ 6.9 mm and X¯ 2 ¡SD520.0¡ 1.9 mm) or C. intervales (X¯ 1 ¡SD531.9¡14.0 mm and X¯ 2 ¡SD533.8¡ 11.4 mm).

Most prey items intercepted by the webs of both spider species were Diptera , especially small (mean body length¡SD 55.1 mm ¡0.9, n 56) tipulids. These tipulids were frequently found resting on the bottom surface of the same leaf types used by H. longicauda and C. intervales at site 7. The relatively higher diversity of prey types found in webs of H. longicauda is probably a consequence of the higher number of items found on the webs of this species (60 against only nine in webs of C. intervales ). Prey captured by H. longicauda included the harvestman Jussara sp., ants, moths, beetles, wasps, and other insects (Table III).

We found 33 spiders attacked by fungi at site 7, all of them on the inferior surface of leaves ( Figure 13 ). From these we identified 14 females and seven males of H. longicauda . Considering the total number of uninfected males and females, the number of females attacked represent at least 9.4% of total (probably more if we suppose that some of the unidentified cadavers were also individuals of H. longicauda ). The number of adult males attacked represent 19.4% of total. The fungus on the cadaver of one H. longicauda female was identified as Gibellula pulchra Cavara, 1894 (Hyphomycetes) .

Figures

Figure 8. Relative humidity (black dots) and temperature variation (white dots) at the margin of Mirante River (site 7) from August 2003 to June 2004.

Figure 13. Specimens of Helvibis longicauda attacked by fungi. (A) A female attacked by the hyphomycete Gibellula pulchra; (B) another female showing a relatively initial stage of infection in the abdomen. Scale bars: 2 mm.

Figures 2–7. Chrysso intevales n. sp. (2–4) Left male palpus, prolateral, ventral, and retrolateral views, respectively. (5, 6) Female epigynum, ventral and lateral views, respectively. (7) Female internal genitalia, dorsal view. C, conductor; Co, copulatory openings; E, embolus; Es, spermatheca; M, median apophysis; St, subtegulum; T, tegulum. Scale bars: 0.1 mm.

Figures 9–12. Photographs of webs and details of viscid silk lines. (9, 10) Webs of Helvibis longicauda mature females: (A) a viscid line collected in the denser area around spider resting position; (B) a viscid line which was extended until the lower leaf. (11, 12) Webs of Chrysso intervales mature females and detail of a viscid line at the mid-point between the upper and the lower leaves. Scale bars: 5 cm.