Scotiazetes bidens Wallwork 1966

Scotiazetes bidens Wallwork, 1966

(Figs 5, 6)

Diagnosis. Body size: 398–448 × 215–265. Rostrum with two incisions, rostrum quadrangular between incisions. Rostral, lamellar and interlamellar setae comparatively long, setiform, barbed. Bothridial seta short, with minute stalk and globular, barbed head. Tutorium with elongate trapezoid cusp, truncate or dentate apically. Four pairs of small, rounded notogastral porose areas. Notogastral, epimeral and anogenital setae of medium length, setiform, roughened or barbed.

Supplementary description of adult. Measurements. Body length: 398–448 (12 specimens, nine males and three females); notogaster length: 298–332 (12 specimens); notogaster width: 215–265 (12 specimens). Females larger than males: 431–448 × 249–265 versus 398–415 × 215–232.

Integument. Body color brown. Body surface and legs densely microporose (visible only under high magnification in dissected specimen). Lateral part of notogaster under posterior part of pteromorph with small tuberculate region. Dorsal side of tutorium striate.

Prodorsum (Figs 5A, C; 6A). Rostrum with two incisions, median part quadrangular. Lamella (77–90) about 1/2 length of prodorsum. Lamellar cusp comparatively long (24–28), truncate. Translamella (24–28) weakly developed. Tutorium (including cusp 94–102 long), elongate trapezoid, truncate or with one to four small teeth apically. Genal tooth fused to the rostrum. Rostral, lamellar and interlamellar setae (32–36) setiform, barbed; insertion of rostral seta removed from tutorial cusp. Bothridial seta (20–24) with minute stalk and larger, globular, barbed head. Bothridium with broad lateral scale, covered (except scale) by anterior notogastral margin. Exobothridial seta (16–20) setiform, slightly barbed. Dorsosejugal porose area poorly observed, diffuse. Dorsophragmata separated, mutual distance 8–12, but located close to each other.

Notogaster (Figs 5A, C; 6B). Anterior margin slightly convex medially. Pteromorph broadly rounded laterally. Four pairs of rounded porose areas (all 10–12). Ten pairs of notogastral setae (p 1 –p 3, 16–20; others 20–28) setiform, roughened. Lyrifissures and opisthonotal gland opening distinct.

Gnathosoma. Subcapitulum longer than wide (94–102 × 69–77). Subcapitular setae (a, 16; m and h, 20) setiform, slightly barbed. Adoral seta (12) setiform, barbed. Palp (69–73). Postpalpal seta (6) spiniform. Axillary saccule (6) distinct, elongate. Chelicera (94–102) with two setiform, barbed setae (cha, 45–49; chb, 28–32).

Epimeral and lateral podosomal regions (Figs 5B, C). Epimeral setae 1a, 2a, 3a, 14–16; others 16–20) setiform, median setae distinctly barbed, lateral setae slightly barbed to roughened. Humeral porose area Am poorly visible, diffuse; Ah represented by small saccule. Custodium (16–20) acuminate. Discidium triangular. Circumpedal carina long, connected with custodium.

Anogenital region (Figs 5B, C). Genital (12–14), aggenital (16–20), anal (16–20), and adanal (16–20) setae setiform, roughened. Adanal lyrifissure located close and parallel to anal plate. Preanal organ goblet-like.

Legs. Median claw distinctly thicker than lateral claws, all slightly barbed dorsally. Porose area present dorsoparaxially on femora I–IV and on trochanters III, IV and proximoventrally on all tarsi. Formulas of leg setation and solenidia: I (1-5-3-4-18) [1-2-2], II (1-5-3-4-15) [1-1-2], III (2-2-1-3-15) [1-1-0], IV (1-2-2-3-12) [0-1-0]; homology of setae and solenidia as indicated in Table 2. Seta s on tarsus I eupathidial. Seta l’ absent on femur III; setae l’ and v’ absent on tarsus I.

See Table 1 for explanations.

Material examined. Twelve specimens (nine males and three females): South Georgia, Stromness Bay, Husvik, Tonsberg, sample of Racomitrium austrogeorgicum from rocky scree above Lake, 18.I.1996 (collected by R. J. Arnold).

Remarks.

1. Wallwork (1966) gave no habitat data for the specimens of Scotiazetes bidens he examined and described from South Georgia. He included Scotiazetes in the family Ceratozetidae (but with hesitation). He suggested similarity with Punctoribatidae (= Mycobatidae), because of the anterior notogastral tectum. His placement of Scotiazetes in Ceratozetidae went unchallenged by subsequent authors (e.g., Starý & Block 1998; Subías 2004). In the present study of possible close relatives of Hogsbackia gen. nov. we show the clear presence of a posterior notogastral tectum in S. bidens, a character state absent in all Ceratozetidae (Ermilov et al. 2015). Based on the presence of the posterior notogastral tectum and a well-developed anterior notogastral tectum we transfer Scotiazetes from Ceratozetidae to Punctoribatidae.

2. Subías (2004) considered Ceratozetes aragonensis Pérez-Íñigo Jr., Herrero & Pérez-Íñigo, 1988 as a member of Scotiazetes and included it in the subgenus Scotiazetes (Guatemalozetes). We have not seen specimens of C. aragonensis, but the description and illustrations indicate that the posterior notogastral tectum is absent. We suggest retention of this species in Ceratozetes pending further studies.

3. Subías (2004) considered Porozetes cuspidatus Covarrubias, 1967 a member of Scotiazetes. In contrast, he placed other species of Porozetes Hammer, 1962, including the type, P. polygonalis Hammer, 1962, as a subgenus of Sphaerozetes Berlese, 1885. Porozetes cuspidatus is incompletely described by Covarrubias (1967), and many important morphological traits are unclear, other than the presence of hinged pteromorphs, which are absent from Scotiazetes. Thus, we do not include this species in Scotiazetes.

4. Subías (2004) included the genus Guatemalozetes Mahunka, 1980 (see also Behan-Pelletier & Ryabinin 1991; Behan-Pelletier & Eamer 2008) as a subgenus of Scotiazetes, without justification. We reject this status, because these genera clearly differ, e.g., by structure of the posterior notogastral tectum (overlapping medially in Guatemalozetes, complete in Scotiazetes), notogaster length to width ratio (1.5: 1 in Guatemalozetes versus 1.3: 1 in Scotiazetes), octotaxic system (3 pairs of porose areas in Guatemalozetes, 4 pairs in Scotiazetes) and the presence of the axillary saccule (absent in Guatemalozetes, present in Scotiazetes).

5. In both Hogsbackia africaensis sp. nov. and Scotiazetes bidens the genal tooth is fused to the lateral margins of the rostrum, so that only the carina of the tooth is evident. This is an unusual expression of this character state in Ceratozetoidea, where a distinct genal tooth is present in all genera, other than some species of the ceratozetid Melanozetes Hull, 1916, and the punctoribatid genera Nuhivabates Niemi & Behan-Pelletier, 2004, and in Antarctozetes mariehammerae Ermilov, Minor & Behan-Pelletier, 2019, Africoribates ornatus Evans, 1953 and A. amorphus Ermilov, Sidorchuk & Rybalov, 2011. As noted by Behan-Pelletier and Walter (2013) polarity of the genal tooth in poronotic Brachypylina is contentious, but, whether plesiomorphic or apomorphic, its modification in Hogsbackia gen. nov. and Scotiazetes is apomorphic.