Robust Trapdoor Tarantula Haploclastus validus Pocock , 1899 : notes on taxonomy , distribution and natural history ( Araneae : Theraphosidae : Thrigmopoeinae )

The genus Haploclastus is endemic to India and is represented by six species. One of the species H. validus Pocock, 1899 was described from Matheran and has remained poorly known in terms of its natural history and distribution. During recent surveys the species was for the first time found again since its description nearly 110 years ago. Based on the new material collected it is redescribed and data on its natural history and distribution are added. It is the first record of an Indian theraphosid spider, which closes its burrow with a trapdoor.


INTRODUCTION
The genus Haploclastus is endemic to India and is represented by six species, namely, Haploclastus cervinus Simon, 1892, H. kayi Gravely, 1915, H. nilgirinus Pocock, 1899, H. satyanus Barman, 1978, H. tenebrosus Gravely, 1935and H. validus Pocock, 1899(Siliwal et al. 2005;Siliwal & Raven 2010;Platnick 2011) of which five have been reported from the Western Ghats (Pocock 1900;Gravely 1915Gravely , 1935;;Molur & Siliwal 2004).While conducting surveys in Aarey Milk Colony, Mumbai, authors (RS & ZM) collected specimens of both sexes of the genus Haploclastus.Initially, it was considered a trapdoor spider of the family Ctenizidae due to its trapdoor burrow structure and some morphological characters.After examining the specimens under a stereomicroscope, it was identified as belonging to the genus Haploclastus of the family Theraphosidae based on the presence of a distinct maxillary heel, the apical segments of the PLS being digitiform, the presence of claw tufts and absence of a rastellum (Dippenaar-Schoeman 2002).Members of the genus Haploclastus possess numerous horizontally aligned thorn-like setae arranged in two to three rows above and below the maxillary suture along with long tapering modified setae aligned vertically in a diffuse pattern on the prolateral side of the maxilla which are distinctly present in females.The species of Haploclastus, which had the closest distribution range to Mumbai, was H. validus from Matheran.To confirm this, surveys were carried out in Matheran, Raighad District, Maharashtra, the type locality of H. validus.From Matheran, both male and female specimens belonging to a single Haploclastus species were collected.This confirms that only one species of Haploclastus occurs in Matheran.Moreover, after examining male and female specimens from Matheran, it was clear that the recent synonym of H. robustus with H. validus by Siliwal & Raven (2010) was valid.In addition to this, females and males from both the localities (Matheran and Aarey Milk Colony) shared characters that were found to be common, further supporting that the species from AMC was H. validus.
According to Siliwal & Raven (2010), the type specimens of H. validus is presumed to be either lost or deposited in some European museum.Therefore, redescription of this species based on type specimens is not possible.The original description of the H. validus lacks information on the species natural history, detailed morphometry of legs and structure of genitilia.Molur & Siliwal (2004) coined a common name for this species as 'Strong Large Burrowing Spider' which needs to be changed as this species is now known to be a trapdoor spider and hence, we propose it as 'Robust Trapdoor Tarantula'.

MATERIAL AND METHODS
Specimens were collected during opportunistic surveys in different parts of Maharashtra.Measurements were taken with a Mitutoyo TM Dial Caliper.All measurements are in mm.Spermathecae were dissected and cleared in clove oil.Total length excludes chelicerae.All illustrations were prepared with the help of camera lucida by MS and morphological details were observed under Labomed stereo-binocular microscope.Descriptive style follows the standardized descriptive style provided by Siliwal & Molur (2007, 2009).All specimens are deposited at the Wildlife Information Liaison Development Society (WILD), Coimbatore, Tamil Nadu, India.

Diagnosis
Male -Carapace slightly shorter than metatarsus + tibia of leg I; slightly longer than patella + femur of leg III; considerably shorter than tarsus + metatarsus of leg IV and tibia + patella of leg I. ALE clearly larger than the rest.Embolus broad at base, slightly twisted anteriorly and flatten, flattened end resembles a duck's bill which tapers into a stout point; ventrally with rows of poorly developed keels.

Female
Carapace slightly longer than metatarsus + tibia of leg IV; slightly shorter than twice the length of tarsus + metatarsus of leg II.Fused seminal receptacle; brickshaped structure with the upper edges smooth and rounded rose to form small mounds.
Colour in life (Image 1): Carapace blackish-brown, carapace overall covered with dense silvery curved grey hair radiating from fovea.Abdomen covered with thick mat of brownish-black hair.Femora, patellae and tarsi of all legs covered with brownish hair; metatarsus and tibia of all legs covered with silvery grey hair.
Leg Coxae: Coxal base dorsally easily seen from above.I longest, about 1.23 times longer than II.Coxae IV widest.Coxae I-IV covered with short and long black hair with black bristles with pallid tips; I-II sloping forward and III-IV sloping backwards.
Claws: Paired bare claws on all legs; palp with a single bare claw.
Abdomen pilosity (Fig. 1): Dorsally covered with mat of short brown hair intermixed with long black and pallid hair and ventrally with short and long brown hair with yellow cuticle exposed.Spinnerets (Fig. 7): Two pairs, yellowish brown covered with golden hair.
Male Palp (Image 2, Fig. 9-11): Embolus broad at base slightly twisted forward and flatten, flattened end resembles a duck's bill which tapers into a stout point.Ventrally with rows of poorly developed keels.

Morphometry of WILD-10-ARA-543:
Total length 26.10.Carapace 14.45 long, 9.11; chelicerae 6.10 long.Sternum: 6.22 long, 5.06 wide.Labium: 2.56 long, 2.16 wide.Abdomen 11.54 long,   Maxillae: Prolateral face with three to four rows of thorn setae intermixed with long spine-like bristles above and below the maxillary suture.Long spine setae scattered above as well as below the thorn rows.Cuspules ca.200 in a triangular patch in the anterior corner.
Sternum: 7.91 long and 5.72 wide.Longer than wide, high at 1/3 region and gradually sloping.Posterior edge acutely sharp, not separating coxae IV.Sternum reddish-brown with a mat of golden short hairs.Long black hair radiating from the marginal area.
Legs: Formula 4123.Leg III clearly thicker than the rest.Metatarsi I 1.09 times longer than tarsi I, metatarsi II 1.22 times longer than tarsi II, metatarsi III 1.40 times longer than tarsi III, metatarsi IV 2.08 times longer than tarsi IV.
Leg coxae: Numerous short scattered spinules on prolateral face of coxae of leg I, II, III and IV.Leg I-III with median narrow light brush, IV glabrous.II-IV with setose mound up from inner corner low mound with few bristles.All retrolaterally lack ventral edge and ventrally with uniform setation.Coxal base dorsally easily seen from above.I longest, about 1.11 times longer than II.Coxae IV widest.Coxae I-IV covered with a mat of golden hair and also with long black hair; I-II sloping forward and III-IV sloping backwards.
Claws: Paired bare claws on all legs; palp with a single bare claw.
Abdomen pilosity: Dorsally covered with a mat of short brown hair intermixed with long black and pallid hair and ventrally with short and long brown hair with yellow cuticle exposed.
Spinnerets: Two pairs, yellowish-brown covered with golden hair.
Spermathecae (Fig. 8): Fused seminal receptacle.A brick-shaped structure with upper edges smooth and rounded, present to form small mounds.

Variations:
Total Abdomen pilosity: Cuticle not visible dorsally in juveniles and sub-adults.Large adults (especially those containing eggs in the body cavity) with cuticle entirely exposed with a fine layer of scattered short golden hair.

NATURAL HISTORY
Matheran is situated at an elevation of 800m and the forest is of semi-evergreen type.The forest in this area is contiguous to that of Prabalgadh and Bhimashankar Wildlife Sanctuary.
Terminalia arjuna, Mallotus philippensis, Albizia amara, Ficus racemosa, Atalantia racemosa, Carvia callosa, Olea dioica, Mangifera indica, Pittosporum dasycaulon and Memycylon umbellatum (Image 6) dominate this area.The temperature fluctuates between 13-34 0 C and the highest rainfall recorded is 850mm.Male specimens of H. validus were commonly encountered during night walks from June to October.A single female was found after excavating a burrow found under a rotting log in a private estate.The habitat at Aarey Milk Colony is highly degraded and altered.The vegetation in the area is of deciduous type and heavily mixed with exotic species.Some of these include Butea monosperma, Tectona grandis, Acacia spp., Ziziphus spp., Pongamia pinnata, Cassia fistula, Mangifera indica, Gliricidia sepium, Delonix regia and Eucalyptus melliodora.
Most of the burrows were found at the base of trees and some in the vicinity of large boulders.All burrows had double door entrances leading to a single tube except for the female found in Bhimashankar, that burrow had a single entrance.The door is made up of a thin layer of silk to which the surrounding soil adheres making the outer layer indistinguishable from its surroundings.The door is usually 'D' shaped or circular, ranging from 10 to 23.62 mm in diameter and 1.80 to 4 mm thick (Image 7).The doors are hinged to the burrow on one side.The burrow is covered with a fine layer of silk.The entrance of the burrow of one specimen from Aarey measured 17.74mm.The burrows are 12 inches to 24 inches deep.The burrow end is slightly wider than the entrance forming a chamber.More than 8-10 burrows can be found at the base of a single tree.
The male from Aarey Milk Colony was found under a rotten tree trunk during the monsoons and the one from Matheran was dug out from its burrow in the month of April along with its exuvia.Both the females were dug out from their burrows.Several burrows at Aarey Milk Colony were excavated.One of the excavated burrows contained a female carrying an egg sac below her chelicerae (Image 8) and the other burrows had only the egg sac silk cover from which juveniles Maxillae (Figs 3 & 6): Prolateral face with randomly arranged long bristles above and below maxillary suture.Cuspules ca.200 in triangular patch in anterior corner.3.82 front length, 4.68 back length, 2.32 wide.Maxillary lyra: No definite shape, small spike setae above and below suture arranged randomly.No ventral brush of lyra.Labium (Fig. 3): 1.45 long, 1.76 wide with ca.220 cuspules restricted to upper region of labium covering ¼ of area.Chelicerae (Figs 4 & 5): Ectal lyrate, grove glaborous; lyra, straight, black spines in 3-4 rows.Promarginal teeth in 2 rows: 11 outer large teeth, 6 small on inner edge adjacent to larger teeth; 50 basomesal teeth in 3-4 rows.Image 1. Haploclastus validus male from Matheran (Raighad District, Maharashtra) Sternum (Fig. 3): 6.22 long, 5.06 wide.Oval, high in centre, sloping gradually, reddish-brown, covered with dense mat of short black hair.Posterior tip sharp but not separating coxae IV.Long black hair radiating margin.

Image 2. Haploclastus validus male palpal bulb. Not to scale
Cuticle not visible dorsally in juveniles and sub-adults.Large adults (especially those containing eggs in the body cavity) with cuticle entirely exposed with a fine layer of scattered short golden hair.

Table 2 . H. validus, measurements of legs and palp of female specimen from Matheran, WILD-10-ARA-1103. Ranges and mean include all female specimens collected from Maharashtra 1103
* -Specimen from Matheran