Centromerus mariannae Slowik 2018, new species
Creators: name: Slowik, Jozef
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Linyphiidae
Centromerus
Centromerus mariannae

description: Centromerus mariannae Slowik, new species
Fig. 8–11.
Centromerus sp. (van Helsdingen 1973)
Centromerus sp. #1 (Crawford 1988)
urn:lsid:zoobank.org:act: 6279732C-C947-490A-8854-15A7875C53E8
Types. Holotype Male: USA. Alaska. Prince of Wales Island, Staney Creek, 55.79726°N, 133.1363°W, 50 m elv., 14–30 May 2010, coll: J. Stockbridge, C. Bickford, thinned 2nd growth, pitfall 3, UAM: Ento:225490.
Paratypes measured. USA. Alaska. 1 female, Prince of Wales Island, Hatchery Ck. 2, 55.89356°N, 132.9437°W, 134 m elv., 28 May 2010, coll: J. Stockbridge, C. Bickford, unthinned 2nd growth, Berlese, UAM: Ento:225476; 1 female, Prince of Wales Island, Hatchery Ck. 4, 55.88285°N, 132.89795°W, 82 m elv., 14 May–30 May 2010, coll: J. Stockbridge, C. Bickford, unthinned 2nd growth, pitfall 3, UAM: Ento:225483; 1 female, Prince of Wales Island, Coffman Cv, 55.98053°N, 132.8607°W, 78 m elv., 28 May–10 June 2010, J. Stockbridge, C. Bickford, unthinned 2nd growth, pitfall 3, UAM: Ento:225493; 1 female, Prince of Wales Island, Coffman Cv, 55.9795°N, 132.86256°W, 67 m elv., 38864, J. Stockbridge, C. Bickford, thinned 2nd growth, Berlese, UAM: Ento:225486; 1 female, Prince of Wales Island, Coffman Cv, 55.98053°N, 132.8607°W, 78 m elv., 10–30 June 2010, J. Stockbridge, C. Bickford, unthinned 2nd growth, pitfall 2, UAM: Ento:225499; 1 male, Prince of Wales Island, Staney Ck., 55.79726°N, 133.1363°W, 50 m elv., 27 April–15 May 2010, Jill Stockbridge, thinned 2nd growth, pitfall 4, UAM: Ento:225466; 1 male, Prince of Wales Island, Hatchery Ck. 4, 55.88433°N, 132.89734°W, 82 m elv., 27 April–15 May 2010, Jill Stockbridge, thinned 2nd growth, pitfall 4, UAM: Ento:225467; 1 male, Prince of Wales Island, Luck Point, 55.98261°N, 132.77986°W, 205 m elv., 18 May–2 June 2010, J. Stockbridge, C. Bickford, thinned 2nd growth, pitfall 2, UAM: Ento:238876; 1 male, Prince of Wales Island, Staney Ck., 55.87126°N, 133.06697°W, 72 m elv., 11 May–22 May 2010, J. Stockbridge, C. Bickford, clearcut/ecotone, pitfall 4, UAM: Ento:225474; 1 male, Prince of Wales Island, Staney Ck., 55.79901°N, 133.11782°W, 41 m elv., 27 June-14 July 2010, J. Stockbridge, C. Bickford, old growth, pitfall 2, UAM: Ento:225500; 2 females, Prince of Wales Island, Staney Creek, 55.79723°N, 133.13467°W, 63 m elv., 10 June 2010, coll: J. Stockbridge, C. Bickford, 2nd growth, Berlese, UAM: Ento:225494; 1 male, Prince of Wales Island, Staney Ck., 55.79726°N, 133.1363°W, 50 m elv., 14–30 May 2010, Jill Stockbridge, C. Bickford, thinned 2nd growth, pitfall 2 UAM: Ento:225489 (DNA Barcoded, bin = BOLD: AAU6230).
Specimen notes. Holotype deposited at UAM. Two pairs of paratypes deposited each at UWBM and the Royal British Columbia Museum. All other paratypes deposited at UAM. An additional 493 specimens were examined and are located at UAM. http://arctos.database.museum/saved/Centromerusnsp.
Etymology. The specific epithet refers to the late Marianne E. Parker (Hippisley) Clark who collected beetles in the Terrace area of British Columbia. She sent her spiders to J. H. Emerton in the early part of the 20th century and is responsible for the specimen originally illustrated and mentioned by van Helsdingen (1973). A historical character in the area, she originally was interested in minerals and bryophytes until she lost her right arm in a gun accident in 1911 and focused instead on beetles.
Diagnosis. Male C. mariannae can be separated from all other Centromerus species in the Pacific Northwest by the small size (1.86–1.94 mm), the presence of a row of denticles along the medial ridge of the paracymbium (Fig. 8), and a single thorn-like spur at the base of the radix and the lamella characteristica (Fig. 9). It may be separated from C. longibulbus (Emerton), which may be encountered along the Eastern edge of the species distribution, which has a single large point on the medial ridge of the paracymbium, and a different shaped radix with a broad projection at the base of the radix and lamella (van Helsdingen 1972, figure 20). It may be separated from C. sylvaticus (Blackwall), a Holarctic species, which is much larger, 2.5–3 mm total length, and has a different radix shape, with a curved anterior portion and a long extended basal fork which curves around towards the paracymbium (van Helsdingen 1973, Figure 29).
Females can be separated from close relatives by the shape of the scape, which is longer than wide with two pair of equally sized lateral lobes (Fig. 11). In C. longibulbus the scape has a single set of lateral lobes (van Helsdingen 1973, Figure 21), and in C. sylvaticus the scape is wrinkled with no lateral lobes (van Helsdingen 1973, Figure 31).
Description. Holotype male. Total length = 1.90 mm; carapace length = 1.0 mm; carapace width = 0.82 mm; L×W ratio 1.21. TmI = 0.51, TmIV absent. Chaetotaxy: FI, 1-1-0-0; FII-IV, 0-0-0-0; PtI-V, 1-0-0-0; TiI-IV, 1-0-0-0; MtI-V, 0-0-0-0. Carapace uniform yellow in color. ALE, PME, PLE similarly sized, AME 2/3 the size of the other eyes, 1/2 eye width apart. Lateral eyes adjacent, PME separated from lateral eyes by almost an eye width. PME 3/4 eye width apart. Clypeus three ALE width. Sternum yellow. Abdomen uniform grey. Legs yellow and unmarked. Three cheliceral promarginal teeth. Cymbium with a basal spur and a bump where the paracymbium sits. Paracymbium robust with a line of small triangular points or denticles running along the medial ridge (Fig. 8). Proximal end wide with a broad distal curve end. Radix with a single thorn shaped spur at the base pointing ventrally. Embolus and lamella characteristica originating from the base of the radix near the basal spur. Embolus proper with a twist about mid-length and two points. Lamella characteristica sickle shaped, broadest in the middle with the distal end transparent (Fig.9). Median apophysis dark pointed sharply towards the lamella characteristica. Median membrane broad and transparent. Sclerite of the median membrane bifurcate.
Female (n = 5). Total length = 1.72 mm; carapace length = 0.82 mm; carapace width = 0.67 mm; L×W ratio 1.21. TmI = 0.46, TmIV absent. Chaetotaxy: FI, 0-1-0-0; FII-IV, 0-0-0-0; PtI-V, 1-0-0-0; TiI-IV, 2-0-0-0; MtI-V, 0-0-0-0. Coloration same as male only the abdomen tends to be slightly lighter in color. Scape bulbus with two basal and two distal lateral lobes (Fig. 11). Scape tip long as the lateral lobes are wide with a prominent scape hook. Spermatheca clearly visible, globular, located near the two basal lobes of the scape, protruding out on the dorsal surface of the epigynum (Fig. 10).
Variation. Male (n = 5). Total length = 1.86–1.94 mm; carapace length = 0.92–1.02 mm; carapace width
= 0.81–0.83 mm. Female (n = 5). Total length = 1.66–1.88 mm; carapace length = 0.79–0.85 mm; carapace width = 0.65–0.69 mm. There is some amount of variation in the size of the basal spur of the cymbium, being much more prominent in some specimens. The number of denticles on the paracymbium is also variable usually from 6–11. The amount the lateral lobes protrude laterally on the scape also shows variation, with the proximal pair sometimes not extending as far laterally as the distal pair.
DNA barcoding. One paratype from UAM (UAM:Ento:225489) was DNA barcoded by Sikes et al. (2017) and falls into BIN BOLD:AAU6230 with 8 other specimens, which is 6.48% distant from its nearest neighbor and shows a maximum within-BIN distance of 1.08%.
Distribution. The species is a common forest floor dweller which has been collected from the Pacific coast inland to the coastal mountains of Washington, up through British Columbia, and into southeastern Alaska. In British Columbia specimens have been collected inland as far as the Rockies. Specimens are collected in pitfall traps and from sifting litter or moss. Mature specimens are usually collected May- June with some additional adults being picked up as late as October in British Columbia.
Discussion. This species was originally illustrated and mentioned by van Helsdingen (1973) of a poorly preserved and damaged male sent to Emerton and found in the MCZ. At the time he realized the novelty of the species, but with only the damaged sample left it to be described at a later time when more samples in better condition could be obtained.
The genus Centromerus shows morphological variation among the species currently included in the genus. This species was included in the cornupalpis -group by van Helsdingen (1973) which includes C. longibulbus which is the nearest congener based on morphology, but it can be identified from the species by the characters mentioned previously. The species is the only member of the West Nearctic Pattern described in Eskov and Marusik (1992). Of the other two Pacific Northwest representatives of the genus, C. longibulbus (Emerton, 1882) and the holarctic C. sylvaticus (Blackwall 1841), this is by far the most commonly collected species of Centromerus.
description: Published as part of Slowik, Jozef, 2018, Tenuiphantes zelatus (Zorsch), T. zibus (Zorsch), and Centromerus mariannae sp. nov. (Araneae: Linyphiidae) in the Pacific Northwest, pp. 1-9 in Insecta Mundi 649 on pages 5-7, DOI: 10.5281/zenodo.3708248