Anelosimus biglebowski Agnarsson, n. sp.
Creators: name: Agnarsson, Ingi
name: Zhang, Jun-Xia
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Theridiidae
Anelosimus
Anelosimus biglebowski

description: Anelosimus biglebowski Agnarsson n. sp.
(Figs 5A–C, 6A–F, 7A–G)
Additional material examined
7♂, 18 Ψ; Same data as holotype. 27♂, 62Ψ: Tanzania, Tanga, Lushoto District, Mazumbai Forest Reserve. 4º49’S 38º29’E, 1650–1730 m, 18.ix.1995.
Diagnosis
Males can be distinguished from most Anelosimus species by the narrow spiraling embolus, and from other species of the filiform embolus clade by its long embolus spiral (except A. sulawesi which is longer), and the shape of embolus base (Figs 5A, 6B–C). Females are readily separated from most Anelosimus by the large size of the spermathecae relative to the epigynal plate. Very similar to A. dude, but the opisthosoma is generally more sharply pigmented, with much contrast between the dark gray and white patterns. The epigynum is slightly more sclerotized, thus the spermathecae are not as clearly visible through the cuticle as in A. dude, furthermore the genital opening is narrower in respect to spermathecae than in A. dude (Figs 5B–C, E–F). To reliably separate these species it is best to clear the epigynum and look at the details of the copulatory ducts. In A. biglebowski the copulatory ducts are longer have more complicated pathways than in A. dude which has relatively short ducts.
Description
Male (holotype): Total length 1.90. Prosoma 0.95 long, 0.80 wide, brown, cephalic area and a narrow rim around the edge of prosoma slightly darker. Sternum 0.55 long, 0.50 wide, light brown with a narrow darker rim. Opisthosoma 1.00 long, 0.80 wide, with Anelosimus pattern, a dark dorsal longitudinal notched fovea, bordered by white. Colular setae smaller than in most other Anelosimus and may be difficult to see under a dissecting microscope. Eyes subequal in size about 0.07 diameter. Clypeus height about 2.6 times AME diameter. Leg I femur 1.25, patella 0.30, tibia 1.10, metatarsus 0.80, tarsus 0.50. Femur I about 5 times longer than wide. Legs pale yellow with distal half of femur I and distal tip of tibia I darker. Tips of femur and tibia of other legs slightly darkened. 2–5 trichobothria dorsally on tibia, 2–4 on tibia I–III, 4–5 on tibia IV. 2 prolateral and 1 retrolateral trichobothria on palpal tibia. Stridulatory pick row on opisthosoma nearly straight, consisting of approximately eight modified setal bases (Fig. 7C). Epiandrous gland spigots in two clearly separate groups of 6–7 fusules (Fig. 7B).
Palpal organ as in Figures 5A, 6A–F.
Female (paratype): Total length 2.00. Prosoma 0.90 long, 0.75 wide, brown, cephalic area and a narrow rim around the edge of prosoma slightly darker. Sternum 0.60 long, 0.50 wide, brown, slightly darker than male, with a narrow darker rim. Opisthosoma 1.20 long, 0.95 wide, dark gray with a dorsal longitudinal notched fovea, bordered by white. Colular setae smaller than in most other Anelosimus and may be difficult to see under a dissecting microscope. Eyes subequal in size about 0.07 diameter. Clypeus height about 2.6 times AME diameter. Leg I femur 1.05, patella 0.25, tibia 0.90, metatarsus 0.75, tarsus 0.45. Femur I about 5 times longer than wide. Legs pale brown with distal half of femur I and II darker brown and distal tip of femur III and IV and tibia I–IV also darker. 2–5 trichobothria dorsally on all tibia, 2–4 on tibia I–III, 4–5 on tibia IV. 2 prolateral and 1 retrolateral trichobothria on palpal tibia.
Epigynum as in Figures 5B–C, 7A.
Va r i a t i o n
Variation in coloration of opisthosoma of both sexes (in alcohol) is large and ranges from grayish with a dull fovea to dark gray with a fovea bordered with sharp white. Similarly prosoma may be pale orange to darkish brown. Leg coloration ranges from yellow to brownish. Male total length from 1.80–2.10, femur I from 1.15–1.40, female total length from 1.85–2.15, femur I from 0.95–1.20. Embolus varies considerably in length, orientation of embolus base, how tightly it spirals and the exact location within the palpus. Generally if the embolus is fairly short it will be tightly coiled and embolus base oriented upwards, if embolus is long it is often more tightly coiled and base is facing downwards. This variation seems to be continuous and although extremes are easy to separate, intermediates of all kinds exist indicating an intraspecific variation rather than the existence of two (or more) species. Both extremes were frequently found in the same sample. Similarly, in the female genitalia the size of the genital opening and in particular the size of the spermathecae is very variable. However the pathways of the copulatory ducts are similar in all specimens and different than in A. dude.
Distribution
Only known from the type locality.
Natural history
Most specimens were collected by canopy fogging, but a few by sweeping vegetation, in a mid elevation rainforest (about 1500–1730 m). The species was more common in samples from 1650–1730 m than samples from 1515 m and was absent in samples from 1370 m. Although sympatric with A. dude over part of its range this species seems to prefer slightly higher altitude than A. dude. Although weak evidence, the sex ratio of collected specimens (about 2.5 female per male) does not suggests these animals have strongly skewed sex ratios, and are thus unlikely to be permanently social.
Phylogenetics
Anelosimus biglebowski has been included in several phylogenetic analyses, as Anelosimus sp. 1 (Agnarsson 2003, 2004) and Anelosimus sp. 2 Tanzania (Agnarsson 2005, 2006). All analyses place A. biglebowski sister to A. dude, together sister to a large clade of species from the Americas, Europe, South Africa and Madagascar (Fig. 1). This large clade is termed the ‘curved SPR clade’ in Agnarsson (2006), referring to one of its most conspicuous synapomorphies, distinctly curved row of stridulatory picks on the male opisthosoma (compare Figs 7C, 9E of A. biglebowski and A. dude to Figs 13F, 16E–F of A. kohi and A. nelsoni, two members of the curved SPR clade.
description: Published as part of Agnarsson, Ingi & Zhang, Jun-Xia, 2006, New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism, pp. 1-34 in Zootaxa 1147 on pages 8-13, DOI: 10.5281/zenodo.172074