Sessiluncus oculatus Vitzthum, 1935

Kazemi, Shahrooz, Nasr, Abdelrady Korashy, Ramadan, Mahmoud Mohamed & Klompen, Hans, 2021, Review of the genus Sessiluncus (Acari: Mesostigmata: Ologamasidae), description of male and redescription of female of Sessiluncus aegypticus, and notes on some morphological characters of the genus, Zootaxa 5061 (2), pp. 271-299 : 291

Sessiluncus oculatus Vitzthum, 1935

( Figures 45–56 )

Sessiluncus oculatus Vitzthum, 1935: 150 .

Sessiluncus oculatus .— Bhattacharyya, 1965: 151; 1977: 47; Lee, 1970: 178; Castilho et al. 2016: 101 .

Sessiluncus oculatus was described based on one male specimen collected in Hawaii by Vitzthum (1935). Thirty years later, Bhattacharyya (1965) reported this species from India, described its female, and redescribed the male. Both of these authors placed this species in the family Parasitidae . In this paper, this species is reported for the first time from Panama based on one female specimen deposited at the Acarology Laboratory of the Ohio State University. Although this specimen was not in good condition, a comparison of the morphological characters of this specimen with the original description and redescription of S. oculatus clearly indicated their conspecificity. Given the lack of data on several diagnostic characters and the discrepancies between our observations and the original description and redescription of S. oculatus , including the number of setae on the dorsal shield, we herein present an updated diagnosis of that species.

Diagnosis (female). Dorsal shield with 35 (36?) pairs of setae, heterogeneous in shape and size; elongate setae slightly flattened near the tip ( Figure 46 ); length ratio of Z5 / J5 = 7–8.5 ( Figure 52 ); glandular opening gd8 absent, gd9 present ( Figures 45 , 52 ). Presternal plates free. Sternal shield sculptured with large suboval ornamentations; sternal setae subequal in length, lightly barbed ( Figures 47 , 52 ). Seta st5 finely barbed. Ventrianal shield markedly wider than long, length/width ratio = 0.8 ( Figure 52 ). Poststigmatic region of peritrematal shield well developed, wide, obliquely truncate, extending beyond coxa IV ( Figures 49 , 52 ). Peritreme straight, extending to anterior level of coxa II ( Figure 52 ). Anterior margin of gnathotectum with a widely triangular, short medial projection, flanked by one pair of short lateral prongs ( Figure 53 ). Corniculus with an inner tooth ( Figure 55 ); setae h1–h3 and pc barbed; posterior lateral transverse ridges connected to deutosternal groove smooth ( Figure 54 ). Movable and fixed digits of chelicera with three teeth ( Figure 56 ). Tibia IV with 8 setae (1, 1/1, 3/1, 1). Trochanter IV with one large hatchet-like projection and one small protrusion dorsally ( Figures 49–50a, b ); femora III–IV each with one finger-like projection ( Figures 49, 50a, 51 ); ventral seta on genu III inserted on a small protrusion ( Figure 51 ).

Material examined. One female specimen, Panama (no further collection information), OSAL 0017119.

Note. This species was originally described from Hawai ( Vitzthum 1935), and was subsequently reported from India ( Bhattacharyya 1965), and now from Panama. These geographical data are unusual, suggesting a pantropical distribution. The Panama record would also make S. oculatus the first Sessiluncus species reported from the Americas. The original description of the species and its redescription show fewer than 30 pairs of setae on the adult male and female dorsal shield. However, examination of the specimen at hand indicated that the species has 6–7 additional pairs of short setae on the marginal areas of the shield ( Figure 52 ). In his complementary description of S. oculatus, Bhattacharyya (1965) illustrated the exopodal strips fused to the ventrianal shield in both sexes (figures 2B, 3B). This does not match with the original description of the species or our observation on the Panama specimen.

Figures

FIGURE 52. Sessiluncus oculatus Vitzthum. Female, ventral idiosoma.

FIGURES 45–51. Sessiluncus oculatus Vitzthum, female. 45. Dorsal shield, posterior region; 46. Shape of some setae on dorsal shield; 47. Sternal shield, median region, and anterior region of epigynal shield; 48. Tarsus; 49. Trochanters and femora III & IV; 50a, b. Trochanter IV; 51. Femur and genu III. Arrows show cuticular projections.

FIGURES 53–56. Sessiluncus oculatus Vitzthum. Female. 53. Gnathotectum and posterior narrow sclerotised band; 54. Subcapitulum; 55. Dorsal (inner) view of hypostome; 56. Chelicera, lateral view.