Mecistocephalus lohmanderi Verhoeff, 1939

Popovici, George, Edgecombe, Gregory D. & Hall, Daniel W., 2024, New Chilopoda from the Chagos Archipelago, Journal of Natural History 58 (41 - 44), pp. 1885-1915 : 1900-1902

Mecistocephalus lohmanderi Verhoeff, 1939

( Figures 8 , 9 )

Material examined

1 ♀, NHMUK015626353 , Diego Garcia, Plantation Gate, 7.412°S, 72.453°E, leaf litter, 03 July 2022, leg. W. Rabitsch; 1 ♂, NHMUK015619671 , Diego Garcia, below Barton Point, 7.277°S, 72.469°E, leaf litter, 24 June 2022, leg. W. Rabitsch.

Summary description

Habitus. Body length 15 mm (♂), 31 mm (♀). Both with 49 leg-bearing segments. Bright yellow with cephalic shield, antennae and forcipular coxosternite dark red. No dark pigmentation of trunk.

Cephalic plate and antennae ( Figure 8 (A)). Cephalic plate sub-rectangular, 1.8 times longer than wide. Setae only present in the posterior half of the buccae. Spiculum evident, not reduced in size ( Figure 8 (B,C)). Antenna 4.3 times longer than width of cephalic plate.

Clypeus and labrum ( Figure 8 (B,C)). Areolate part of the clypeus 1.3–1.5 times longer than the plagulae; armed with 3 + 3 postantennal and two medial setae. Finely areolate area or insulae absent. Labrum with wide medial part clearly separating the lateral parts. Internal margin of anterior ala longer than internal margin of posterior ala.

Forcipular coxosternite ( Figure 8 (D)). Internal margin of trochanteroprefemur as long as basal width. Trochanteroprefemur armed with two sclerotised tubercles, the distal more prominent. Femoroid and tibia each armed with one sclerotised tubercle. Basal tubercle of tarsungulum reduced in size. Forcipular cerri absent.

Trunk ( Figure 9 (E)). Anterior metasternites with poorly sclerotised mid-longitudinal sulcus. Anterior margins bifurcating at obtuse angle.

Ultimate leg-bearing and postpedal segments ( Figure 9 (A–D)). Posterior margin of ultimate metatergite variably rounded or straight ( Figure 9 (B,C)). Ultimate metasternite sub-triangular to trapezoidal; 1.1 times wider than long. Posterior pillow-like process present ( Figure 9 (A)). Coxopleurae with ca. 15–20 coxal organs opening on the entire ventrolateral surface. Telopodal articles elongate, more densely setose on the ventral side in both the male and female. Gonopods fully developed, conspicuously articulated in male ( Figure 9 (D)).

COI barcode. GenBank accession number PQ165825.

Remarks. The geographically closest sampled localities to the Chagos Archipelago include the Maldives (Inguiradhoo). Mecistocephalus specimens in the NHM collection, labelled as Mecistocephalus insularis Lucas, 1863 , collected during the 1899– 1900 Maldive-Laccadive expedition ( Gardiner 1901 –06), show a great degree of morphological similarity to the Mecistocephalus present on Diego Garcia. Further examination of diagnostic characters revealed that these are consistent with Mecistocephalus lohmanderi , originally described from Mauritius ( Verhoeff 1939), and recently revised based on material from the Seychelles and maintained as a valid species ( Bonato and Minelli 2010).

Mecistocephalus insularis , a problematic and inadequately described taxon, has in past literature been used indiscriminately for Mecistocephalus specimens with 49 leg-bearing segments collected around the Indian Ocean. This species is in urgent need of revision to adequately assess the diversity of African and Southeast Asian members of the genus. In the absence of recently collected specimens from the type locality and a redescription of the type material, questions concerning the morphological variability of Mecistocephalus species as well as their potential for dispersal and introduction to new sites cannot be adequately addressed.

Figures

Figure 8. Mecistocephalus lohmanderi Verhoeff, 1939. NHMUK015626353, except (C) NHMUK015619671. (A) Cephalic plate and antennae, dorsal view. (B) Labrum and clypeus, ventral view, showing spiculum (spi). (C) Labrum and clypeus, ventral view. (D) Forcipular segment, ventral view.

Figure 9. Mecistocephalus lohmanderi Verhoeff, 1939. (A–E) NHM UK015626353; (C,D) NHM UK015619671.(A) Female ultimate leg-bearing segment, ventral view. (B) Female ultimate leg bearing segment, dorsal view. (C) Male ultimate leg-bearing segment, dorsal view. (D) Male ultimate legbearing segment, ventral view. (E) Metasternite of segment 7, ventral view.