Ityphilus cf. taeniaformis ( Lawrence, 1960 )

Ityphilus cf. taeniaformis ( Lawrence, 1960)

Figs 19 View Figure 19 , 20 View Figure 20 , 21 View Figure 21 , 22 View Figure 22 , 23 View Figure 23

Examined material.

NHMUK 015991468 , 1 ♂, Aldabra , 21. 03. 1974., V. W. Spaull leg.

Description.

Head and antennae. Antennae conspicuously claviform in shape, medially weakly geniculate, with articles IX – XIV widened (Figs 19 A View Figure 19 , 20 A, C View Figure 20 ). Articles IX and XIII with clusters of type c sensilla (sensu Pereira 2017) on the distal edge of the dorsal side (Fig. 19 C, D View Figure 19 ). Article XIV with two lateral clusters of sensilla basiconica and a small number of spear-shaped sensilla at its apex (Fig. 19 B View Figure 19 ). Head approximately as wide as forcipular tergite, 1.14 × broader than long. Curved sulcus near posterior margin. Chaetotaxy of head as in Fig. 20 B View Figure 20 .

Mandibles. Dentate lamella with seven denticles, only six conspicuous in lateral view. Pectinate lamella with approximately 22 hyaline projections (Fig. 21 A View Figure 21 ).

Labrum and clypeus. Clypeus with a pair of postantennal setae, a cluster of seven medial setae and one prelabral seta. Lateral pieces of labrum narrow, conspicuously sclerotised, lacking any fringes or projections. Medial piece contiguous with clypeus, poorly sclerotised, membranous and lacking conspicuous hairs or projections.

Maxillae. First maxillae with evident, triangular coxal projections, each bearing one sensillum. Telopodites bearing one sensillum each, conspicuously larger than coxal projections and partly covering them (Fig. 21 B View Figure 21 ). Lappets absent. Second maxillary coxosternite with evident but incomplete medial suture, extending for half of its length (Fig. 21 C View Figure 21 ). Each side of the suture bearing one sensillum. Telopodite stout, terminating in large pretarsus. Second maxillary pretarsus spatulate, lateral edges densely fringed (Fig. 21 D, E View Figure 21 ).

Forcipular segment. Exposed face of forcipular coxosternite 2.2 × broader than long (Fig. 22 A View Figure 22 ). Chitin lines present, reaching the condyles. Forcipular trochanteroprefemur 1.25 × longer than broad. Calyx of venom gland elongated, ovoid in shape (Fig. 22 C View Figure 22 ). All forcipular articles without denticles (Fig. 22 B View Figure 22 ). Internal margin of tarsungulum smooth. Extended, forcipules do not reach the anterior margin of the head.

Trunk. 75 leg-bearing segments. Pore fields located on raised areas in the middle of all metasternites excluding those of leg-bearing segments 1, 74, and 75. Shape of pore field oval, medially constricted and anteriorly bordered by a line of setae (Fig. 22 D View Figure 22 ). Colour of pore field bluish grey, conspicuously pigmented relative to surrounding cuticle. Despite the faded colour of the ethanol-preserved specimen, pigmentation of the pore field is conspicuous and the trunk is generally greenish grey in appearance.

Ultimate leg - bearing and postpedal segments. Intercalary pleurites separated from ultimate pretergite by evident sutures. Ultimate metasternite trapezoidal, 1.3 × longer than broad. Coxopleura each with two distinct coxal organs, partially covered by the ultimate metasternite (Fig. 23 A View Figure 23 ). Entire ventral side of ultimate leg-bearing segment covered in setae. Ultimate leg telopodite composed of seven articles, all distinctly thickened. Pretarsus absent (Fig. 23 B View Figure 23 ). Metatarsus with a small spine subapically. Intermediate sternite indistinct. First genital sternite with straight posterior margin. Gonopods uni-articulate, flanking penis (Fig. 23 C View Figure 23 ).

Remarks.

The taxonomy of Ityphilus remains largely unresolved, especially outside of South America, where different authors have disagreed on its relation to Ballophilus , alternatively considering it a different genus ( Attems 1929) or a synonym of Ballophilus ( Verhoeff 1939) . Recent revision of the genus ( Bonato et al. 2007) has maintained the distinction between Ityphilus and Ballophilus , but remarked on the close relationship between the two, and on cases in which the presence of complete or nearly complete chitin lines is doubtful, such as in Ityphilus boteltobogensis ( Wang, 1955) , despite this character being predominantly used to distinguish the two genera. Similarly, several Ballophilus species are described as bearing a cuticular thickening in the usual position of the chitin line ( Demange 1963; Pereira et al. 1997), further confounding the utility of this character in taxonomy within the Ballophilidae . The presence of a median sulcus in the second maxillary coxosternite has been shown to be unreliable in separating Ballophilus and Ityphilus . This character has been described in both Ballophilus ( Ribaut 1914; Pereira et al. 1997) and Ityphilus ( Pereira et al. 2000) , in some cases as incomplete ( Brölemann 1909) (Fig. 21 B, C View Figure 21 ), and is not included in the most recent diagnosis of the latter genus ( Bonato et al. 2007).

Verhoeff (1939) described two Ballophilus species from Mauritius, B. lawrencei Verhoeff, 1939 and B. mauritianus Verhoeff, 1939 . Both are known from single specimens but, according to their original description, compare closely with Ballophilus allauadi Ribaut, 1914 described from Eastern Africa. The Aldabra specimen differs from these species in the presence of pore fields on all but the first and last two leg-bearing segment metasternites (contrasting with the absence of the pore field on the first and the last four metasternites). Additionally, the distal end of the antenna of B. lawrencei is illustrated as markedly less clavate than observed for the Aldabra specimen. Despite this, the Ityphilus specimen collected in Aldabra overlaps in the shape of the metasternal pore field, its position on a raised area and in the relative elongation of the ultimate leg-bearing segment telopodite and the number of leg-bearing segments with B. lawrencei . As all Mauritian Ballophilus species are known solely from their holotypes, it is not possible to comment on intraspecific variability that may account for the overlap in these traits.

Ballophilus maldivensis Pocock, 1906 , described from the Maldives, similarly resembles the Aldabra specimen in the shape of the metasternal pore fields and their pigmentation. The incomplete original description did not allow for comparison of any other putative diagnostic characters beside the number of leg-bearing segments (67 in the female holotype), which is lower than that of the Aldabra specimen (75 in a male). Re-examination of the holotype (Fig. 24 View Figure 24 ), the sole known specimen, revealed several features that further distance it from the Aldabra specimen and bring it closer to the currently accepted diagnosis of Ballophilus . Ballophilus maldivensis lacks chitin lines or any cuticular thickenings near their position (Fig. 24 A, B View Figure 24 ). Other important differences from I. cf. taeniaformis from Aldabra include the absence of the metasternal pore field from the last four leg-bearing segments and a more strongly enlarged ultimate leg telopodite (Fig. 24 D View Figure 24 ).

Lawrence (1960) described three species assigned to Ballophilus from Madagascar, of which Ballophilus taeniaformis Lawrence, 1960 overlaps in nearly all diagnostic traits with the Aldabra material examined, differing only in the number of teeth on the dentate lamella of the mandible (7 in the Aldabra specimen compared to eight or nine in B. taeniaformis ). Lawrence made no comment on the presence or absence of the chitin line on the forcipular coxosternite for the species he assigned to Ballophilus . As noted above, this character has been used to differentiate between the genera Ballophilus and Ityphilus , although its variability as discussed above and the lack of consensus on the status of Ityphilus at the time of Lawrence’s original description of B. taeniaformis prompt us to refer the examined specimen from Aldabra to Ityphilus .

In nearly all characters examined, the singular specimen from Aldabra agrees with the description of Ityphilus melanostigma (Attems 1900) and the subsequent redescription of this species from specimens collected in the Seychelles ( Bonato and Minelli 2010). However, the greatly reduced number of leg-bearing segments (75) relative to the presently known range within I. melanostigma (95–101) suggest specific distinction, as extensive variation in leg-bearing segment number is not generally known from other species of Ityphilus . Other putative differences to the original description of I. melanostigma include the greater relative enlargement of the ultimate leg pair telopodites in the Aldabra specimen, relative to Ityphilus specimens illustrated from the Seychelles ( Bonato and Minelli 2010).