Cheiracanthium ilicis, Morano, Eduardo & Bonal, Raul, 2016

Morano, Eduardo & Bonal, Raul, 2016, Cheiracanthiumilicis sp. n. (Araneae, Eutichuridae), a novel spider species associated with Holm Oaks (Quercusilex), ZooKeys 601, pp. 21-39 : 25-31

Taxon classification Animalia Araneae Eutichuridae

Cheiracanthium ilicis sp. n.

Holotype.

The holotype is a male collected in Spain: Huecas (Toledo), 581 metres above sea level (40.029915°N, 4.226789°W) by E. Morano et al. on 27 May 2013. The specimen is deposited in the collection of Arachnids of the Museo Nacional de Ciencias Naturales(CSIC), Madrid, Spain with the following reference MNCN 20.02/17491.

Paratypes.

2 males and 3 females: same data as the holotype (males: MNCN 20.02/17494 and MNCN 20.02/17496; females: MNCN 20.02/17492; MNCN 20.02/17493 and MNCN 20.02/17495).

Other specimens examined.

Collected in the same village as the holotype but on a different date the following specimens have been studied and deposited in Eduardo Morano’s personal collection: 30 Jan 2013, 6 imm (branches); 26 Feb 2013, 2 imm (branches); 21 Mar 2013, 15 imm (branches) and 1 imm (trunk); 26 Apr 2013, 8 imm (branches) and 3 imm (trunk); 27 May 2013, 4 ♀, 3 ♂, 1 imm (branches); 25 Jun 2013, 3 ♀ (branches) and 1 imm (grass); 19 Jul 2013, 1 ♀, 31 imm (branches) and 2 imm (grass); 23 Aug 2013, 14 imm (branches); 27 Sep 2013, 15 imm (branches) and 5 imm (trunk); 22 Oct 2013, 29 imm (branches) and 9 imm (trunk); 28 Nov 2013, 8 imm (branches) and 10 imm (trunk); 19 Dec 2013, 2 imm (branches).

Etymology.

Most of the individuals of this novel species were collected from Holm oaks Quercus ilex . The Latin name of this oak species ( ilex ) in its singular geni tive form ( ilicis ) has been thus used to name this spider so as to link it to the main habitat it occupies.

Diagnosis.

Cheiracanthium ilicis sp. n. closely resembles Cheiracanthium inclusum and Cheiracanthium mildei but can be distinguished by the structure and morphology of the copulatory organs of both sexes. The palps of Cheiracanthium ilicis sp. n. males have a characteristic bifurcated tegular apophysis (TA; Fig. 1). Females exhibit a wide central septum that separates the copulatory openings, which are laterally opened in both depressions, and a very characteristic loop in the copulatory duct (Fig. 2).

Description.

Male (Holotype). All measurements are given in millimetres. Medium size. Total length: 9.4; dorsal shield lenght: 4.1; anterior dorsal shield width: 1.9; opisthosoma length: 5.0; opisthosoma width: 3.1. Eye diameter. AME: 0.150; ALE; 0.175, PME: 0.200, PLE: 0.225. Distance between eyes: AME - AME: 0.350, AME - ALE: 0.425, PME - PME: 0.225, PME - PLE: 0.275, AME - PME: 0.225, ALE - PLE: 0.05; height from clypeus to AME: 0.1; height from clypeus to ALE: 0.1.

Prosoma. Yellowish, the ocular region is darker. The immatures show a homogeneous pale green colour, changing to yellow as they reach sexual maturity (see Pictures 2 and 3). The dorsal shield has an oval shape, is slightly raised in the ocular region and has a scarcely marked thoracic furrow. The eyes are of similar size and placed in two transversal rows of four eyes each: the posterior row is longer than the anterior one; the anterior row is straight and the posterior one slightly curved; the eyes in the middle of the anterior row are less distant from each other than from the lateral ones. In the posterior row the eyes are almost regularly spaced, in such a way that the distance between the two posterior medium eyes is smaller than with those in the anterior medium eyes. The lateral eyes are very close together. The clypeus is narrower than the diameter of the AME. The labium is elongated and with a blunt end; the maxillas elongated and laterally cleaved; both structures have a light brown-orange colour with the apical ends paler, whitish. The sternum is triangular and orangish. The chelicera are dark brown-orange with a small basal condyle on its external surface. The basal segment does not have any modification and has few teeth on its margins. The promargin has two teeth, the superior one being larger; the retromargin has a decreasing series of three teeth, the first one being larger than the rest. Visualising these teeth is difficult due to the dense brush of hairs that covers them.

Legs. Yellowish and relatively long, ordered according to their length in the following way, 1:4:2:3. The trochanters show a marked external notch. The metatarsus and tarsus have scopulae on the distal portion and the latters have dense tarsal tufts.

Spination (Table 1). The palp is completely spineless as are the leg patellas and tarsus. Usually, the specimens examined have shown two pairs of femoral lateral spines and three pairs of lateral spines in the metatarsus III and IV. There is variability, for instance, in the tibia I, which can bear from nine to 11 ventral spines.

Opisthosoma: Elongated, oval and slightly covered with pubescence, without erect antero-dorsal hairs. It has a uniform creamy colour all over its surface and its dorsum shows just a superficial heart mark, which is creamy or light green in adults and immatures respectively (see Pictures 2 and 3). The spinnerets are formed by two segments. The posterior spinnerets are longer than the contiguous anterior ones and are cone-shaped.

Male palps (Fig. 1). Most segments are light yellow with only the tarsus being brownish in colour; the tibia shows a curved retrolateral apophysis (RTA) and, in lateral view, it is inclined outwards; the tarsus is longer than the patella and the tibia taken together. The cymbium is elongated with retrolateral dilation, bearing a spur (CS) projected towards the tibia close to its retrolateral apophysis. The embolus is filiform, long and black; it starts on the retrolateral flank, surrounds the base and ends lying on the conductor (C) at the distal end of the palp. This conductor is membranous and with a pointed end. The apex hides the anterior branch of the tegular apophysis (TA). This inner branch is much more sclerotised and has the shape of a dentated disc perpendicularly oriented with respect to the external branch; the external branch of the tegular apophysis is laminar and is spoon-shaped.

Female (Paratypes, n=3). All measurements are given in millimetres. Medium size (ranges and means within brackets). Total length: 8.8-9.7 (9.13); prosoma length: 3.7 -4.2 (4.00); prosoma width: 2.9-3.3 (3.06); opisthosoma length: 4.7-6.0 (5.23); opisthosoma width: 3.8-4.9 (4.30). Eyes diameter. AME: 0.200; ALE; 0.175, PME: 0.200, PLE: 0.175; distance between eyes: AME–AME: 0.300, AME–ALE: 0.325, PME–PME: 0.350, PME–PLE: 0.375, AME–PME: 0.200, ALE–PLE: 0.075, height from clypeus to AME: 0.175, height from clypeus to ALE.

In general, the appearance and colouration of males and females is similar, although the latter are larger and with shorter legs than the slender males. Compared to males, the female dorsal shield is much wider. Eye arrangement is similar in both sexes, but female eyes are a slightly larger. The margins of the chelicera bear 3 teeth (the middle one being larger) in the promargin and two teeth in the retromargin, where the first one is larger. As in the case of males, visualisation is difficult due to the dense brush of hair covering them.

Spination (Table 2). Female palp has a single, simple, straight claw. In the females examined the variability found in the spination patterns is greater than that of the males. In general, the most frequent pattern repeated has been the presence of a single spine on either side of tibias III and IV. Other than this, the spine arrangement is very variable among individuals.

Epigyne (Fig. 2A, B). It is an oval-shaped plate, wider than longer, with a rim resulting from the protrusion of the spermathecae and copulatory ducts. The copulatory openings are placed laterally, protected by the rim, and in the middle zone of a spherical funnel-shaped depression. In some females these depressions were covered by a dark substance that had to be removed in order to examine the morphology of the epigyne (Fig. 2A) (Dondal and Redner 1982). In the centre of the plate a septum separates each of these two depressions. In some specimens, the transparency allows the observation of the lateral section of the copulatory ducts, and also the spermathecae located in the posterior zone of the epigynal rim (Fig. 2B).

Vulva (Fig. 2C). The copulatory ducts start in each depression and go backwards, where they are ventrally curved forming a loop and going towards the spermathecae located behind. These spermathecae are small, almost circular and separated.

Phylogenetic relationships

The sequence of the cythochrome oxidase I gene was identical in the three individuals of Cheiracanthium ilicis sp. n. (GenBank Accession code KX272624). The divergence with respect to the closest species ( Cheiracanthium mildei ) was 7.5% and 11.4% with respect to Cheiracanthium inclusum .

The two gene trees (cox1 and 28SrRNA) showed congruent topologies, what allowed the concatenation of the sequences of both genes. Sequences of both genes were available for all species with the exception of 28SrRNA for Cheiracanthium inclusum . The Bayesian phylogeny combining both genes (Fig. 3) retrieved a clade with a highly supported node (PP=1) that included four species ( Cheiracanthium punctorium , Cheiracanthium inclusum , Cheiracanthium mildei and the new Cheiracanthium ilicis sp. n.); within this group, Cheiracanthium mildei and Cheiracanthium ilicis sp. n. were sister groups (PP=0.86) and Cheiracanthium inclusum was sister to the Cheiracanthium mildei - Cheiracanthium ilicis sp. n. clade. Cheiracanthium mildei - Cheiracanthium ilicis sp. n. (Fig. 3) were also sister-species in the two gene trees.

Habitat distribution and phenology

The novel species of Cheiracanthium was not randomly distributed in the four habitats sampled (Chi=98.59; df=3; P<0.0001). Most of the individuals were collected from Holm oak branches (82.68%) and trunks (15.64%); only three (1.67%) from grass and none from pit-fall traps. All adults were captured from the tree branches but the habitat distribution differences between adults and immatures were not statistically significant (Chi=4.02; df=2; P=0.13). There was a positive relationship between the number of individuals collected from each tree and the surface of its canopy (Fig. 4; Estimate=0.026170; Z=7.894; P<0.001). The positive effects of tree size on Cheiracanthium ilicis sp. n. numbers were independent of the spatial distribution of the trees. The Mantel test demonstrated that the number of individuals collected was not spatially autocorrelated (R=-0.004; P=0.41) and the positive relationship between canopy surface and Cheiracanthium ilicis sp. n. numbers remained significant after checking the Euclidean spatial distance between trees (R=0.30; P<0.01).

We collected individuals of Cheiracanthium ilicis sp. n. all year round, but the numbers were lower in the winter months (Fig. 5). There were significant differences between age classes (Chi=170.79; df=3; p<0.0001), as almost all adults were collected only in the second quarter of the year (spring-early summer).