Schatz, Heinrich ¹

¹✉ c/o Institute of Zoology, Leopold-Franzens-University of Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.

2024 - Volume: 64 Issue: 2 pages: 463-479

ZooBank LSID: B0B75F63-404D-41F2-9926-ACA5D7172324

Original research

Keywords

Abstract

Introduction

The oribatid mite taxon Ceratozetoidea Jacot, 1925 is very rich in species, and representatives of this superfamily are found in all zoogeographical realms. They are organized in ten families (Schatz et al. 2011, updated): Ceratokalummidae Balogh, 1970; Ceratozetidae Jacot, 1925; Chamobatidae Grandjean, 1954; Euzetidae Grandjean, 1954; Humerobatidae Grandjean, 1971; Maudheimiidae Balogh & Balogh, 1984; Punctoribatidae Thor, 1937; Onychobatidae Luxton, 1985; Ramsayellidae Luxton, 1985; Zetomimidae Shaldybina, 1966. In the course of investigating oribatid mites on the Galapagos Islands (Schatz 1998) six Ceratozetoidea species have been recorded. Of these, two species of Cultrobates (Fam. Ceratokalummidae) were recently described (Schatz 2023), descriptions of further species in that family are in preparation.

On the Galapagos Islands, two species of the family Ceratozetidae were recorded, Ceratozetes sp. and Porozetes sp. Detailed morphological examinations revealed that the specimens of Ceratozetes sp. belong to an undescribed species of this genus, while the single specimen of the other species, previously incorrectly listed as ''Porozetes sp.'' is Humerobates rostrolamellatus Grandjean, 1936 (Fam. Humerobatidae). Both species are presented respectively described here.

The genus Ceratozetes was proposed by Berlese (1908) with Oribata gracilis Michael, 1884 as type species. The distribution of the genus is cosmopolitan, the majority of the known species occur in the Holarctic realm. As Seniczak et al. (2017) stated, the definition for Ceratozetes is interpreted differently in the literature. The generic diagnosis proposed by Behan-Pelletier (1984) is formulated more broadly and includes (among other character states) species with 10 or 11 pairs of notogastral setae, rostrum with or occasionally without lateral teeth and median tooth, and with truncated or long lamellar cusps. In contrast, Pavlichenko (1994) and Subías (2022) consider Ceratozetella Shaldybina, 1966 as separate taxon for Ceratozetidae species with 10 pairs of notogastral setae, lamellar cusps with dens, and larvae with 3 large, segmentally arranged shields. The presence or absence of the notogastral seta c₃ in the context of the mosaic distribution of other morphological characters in the species of these taxa suggests a close relationship between these species, and like Seniczak et al. (2017), I follow the broader generic definition of Ceratozetes proposed by Behan-Pelletier (1984), as do Weigmann (2006); Behan-Pelletier and Eamer (2009); Seniczak et al. (2016) (see Remark #1).

The genus Humerobates was proposed by Sellnick (1928) with Notaspis humeralis (Hermann, 1804) as type species. Nevertheless, this was a misidentification by Sellnick. Grandjean (1936), after collecting in the surroundings of Strasbourg (where Hermann made his collections) considered the species of Hermann as Diapterobates, and humeralis in the sense of Sellnick and auct. as another species which he renamed Humerobates rostrolamellatus. The ICZN established Humerobates rostrolamellatus Grandjean, 1936 as the type species of Humerobates (Norton 1985; ICZN 1987). Humerobates rostrolamellatus is widely distributed and was recorded in the Palaearctic, Nearctic and Afrotropical realms as well as on Indomalayan islands in the Western Pacific Ocean and Polynesia. A previous finding of this species in the Neotropical realm is uncertain (see Remark #4).

Material and methods

Most of the material from the Galapagos Islands was collected during several expeditions to all the major and most of the minor islands of the archipelago by Heinrich and Irene Schatz in the years of 1985–1988 (Schatz 1998), supplemented by further collections by Sandra Abedrabbo, Harald E. Pehofer, and the group of Leon Baert, Konjev Desender, and Jean-Pierre Maelfait. The Galapagos material was collected more than 30 years ago. Due the age of the preseerved material and the difficulty of obtaining suitable preservation fluid on the remote archipelago at that time, several individuals are now in bad condition or damaged. Although this allows morphological studies, it is questionable whether this material is still suitable for molecular analyses. Details of samples are given in the respective records of the species.

The soil and organic litter samples from the Galapagos Islands were extracted in the Charles Darwin Research Station in Galapagos with a modified Tullgren–Berlese extraction apparatus (details see Schatz 1998). For microscopic studies the specimens were mounted in lactic acid on temporary cavity slides for illustration, and subsequently preserved in ethanol. Drawings were made with a camera lucida attached to a transmission light microscope ''Nikon Eclipse E400″. Each measured parameter was oriented to the particular optimal parallax-free perspective. Measurements of total body length was done in lateral view, from the tip of the rostrum to the posterior edge of the notogaster. Body width refers to the maximal width of notogaster in dorsal aspect. Measurements indicated are ranges between maximum and minimum value, mean in parentheses; all measurements are given in micrometers (μm). Females are recognizable by the presence of ovipositor and/or eggs, males by the small spermatopositor under the genital plates (Grandjean 1956). The terminology of morphological features used in this paper follows that of Grandjean (summarized by Travé and Vachon 1975; Travé et al. 1996; Norton and Behan-Pelletier 2009).

In the text and figures the following abbreviations were used: Prodorsum: rostral (ro), lamellar (le), interlamellar (in), bothridial (bs), exobothridial (ex) setae, genal tooth (gt), tutorium (tu), dorsosejugal porose area (Ad), dorsophragma (Dp), pleurophragma (Pp). Notogaster: porose areas (Aa, A₁ , A₂ , A₃ ), notogastral setae (c₂, c₃ , l-, h-, p-series), lyrifissures (ia, im, ip, ih, ips), opisthonotal gland opening (gla). Gnathosoma: subcapitular setae (a, m, h), axillary saccule (as), adoral setae (or), cheliceral setae (cha, chb), Trägårdh's organ (To), palp setae (sup, inf, d, l, cm, acm, lt, vt, ul, su), solenidion (ω), postpalpal seta (pps). Epimeral, lateral podosomal regions: pedotecta I, II (PtI, PtII), humeral porose areas (Ah, Am, Ai), custodium (cus), discidium (dis), circumpedal carina (cp), epimeral setae (1a–1c, 2a, 3a–3c, 4a–4c). Anogenital region: genital, aggenital, anal, adanal setae (g₁–g₆ , agg, an₁, an₂, ad₁– ad₃ ), adanal lyrifissure (iad), preanal organ (po), postanal porose area (Ap). Legs: leg setae (ft, tc, it, p, u, a, s, pv, pl, d, l, v, bv, ev, parentheses refer to a pair of setae), solenidia (ω₁ , ω₂ , φ, φ₁ , φ₂ , σ), famulus (ɛ), porose area (pa).

Taxonomy

Family Ceratozetidae Jacot, 1925

Genus Ceratozetes Berlese, 1908

Type species: Oribata gracilis Michael, 1884

Ceratozetes yupanqui n. sp.

ZOOBANK: 9A29CE80-4A9A-44AC-91F5-B6A3BBC3F664

Ceratozetes sp.: Schatz 1998, p. 387.

(Figs 1–5)

Diagnosis

Adults of Ceratozetes yupanqui n. sp. differ morphologically from their congeners by the following combination of characters: Body size: 470–570 x 320–405. Rostrum flattened and broadened. Lamella broadened plate, without translamella, cusp triangular. Bothridial seta with clavate head. Tutorium with long free protruding tip. Exobothridial seta long. Pteromorph immovable. Ten to eleven pairs of notogastral setae, seta c₃ sporadically present as alveolus or as short seta, four pairs of small porose areas on notogaster, postanal porose area present. Circumpedal carina, custodium and triangular discidium present. Epimeral setal formula 3–1–3–3, genito-anal setal formula 6–1–2–3. Tarsi on legs heterotridactylous.

Description of adult

Measurements — Females (n=15): L 500–(520)–570, W 350–(380)–405, males (n=8): L 470–(490)–500, W 320–(345)–390.

Integument — Body colour light brown, notogaster, epimeral, ventral, genital, anal plates finely granulated. Distal surface of tutorium, pedotecta I and II striated. Pteromorphs longitudinally lightly striated.

Prodorsum — Rostrum flattened and broadened, laterally on both sides a mediad curved chitinous buckle. In lateral aspect, tip of rostrum forming a ventrally open tunnel. Lamella distally broadened, without translamella, cusp triangular, length ~60, with short lateral tooth adjacent to insertion of lamellar seta. Prodorsal setae setiform with small bristles, all directed anteriad, rostral seta (ro, 80–90) inserting underneath tip of tutorium. Lamellar seta (le, 80–85) inserting on inner edge of cusp. Insertion of interlamellar seta (in, ~130–140) on anterior margin of notogaster, distance between insertions 85–100. Bothridium cup-shaped, with three scales, medial scale pointed, directed anteromediad towards lamellar edge, bothridial seta (bs) of medium length (stem 40–50, head ~30), directed laterad or anterolaterad, head clavate, slightly thickened (width ~5–8), dorsally spoon-shaped indentation with small bristles. Tutorium long and narrow blade (tu, 110–130) with free protruding tip anterodistally (40–50). Genal tooth (gt) large, distally attenuating. Dorsosejugal porose area (Ad) posterior to insertion of in, small, oval (~20 x 6). Internal apophyses hardly visible, dorsophragmata (Dp) small, between dorsosejugal porose areas, pleurophragmata (Pp) larger, posterior to bothridia. Exobothridial seta long (ex, 40–50), ventral to posterior end of bothridium.

Notogaster — Oval, about 1.20–1.30 x longer than wide. Anterior margin projecting anteriad. Pteromorph immovable, edge curved ventrad. Ten pairs of notogastral setae, setiform (~45–55, c₂ longest, 60–65) with short bristles. Additionally, alveolus of seta c₃ present in some specimens (Figs 1A, 3A), rarely evident as thin and short seta (5–8, Fig. 3B) (see Remark #1). Four pairs of small porose areas, Aa largest (15–20 x 7–10), oval, directed anterocentrad, A1 oval (12–15 x 6–8), A2, A3 round to oval (5–7). Lyrifissures distinct, best visible in lateral view, ia situated posterior to c₂ , im posterior to la, ip anterior to p₂ , ih lateral to h₃ , ips anterior to p₃ . Opisthonotal gland (gla) opening distinct, located near lp.

Gnathosoma — Subcapitulum diarthric, mentum large (~100 x 70–80). Subcapitular setae h (30–35), m (25–30), a (~15), attenuating with very short bristles. Adoral setae on conical lips, smooth (or, 6–8). Axillary saccule posterior to seta m, oval elongated (as, 6–8 x 3). Chelicerae chelate-dentate, size (n=10) 130–140 x 45–50. Cheliceral setae attenuating with small bristles, cha (40–45) inserting paraxially near dorsal margin, directed anteriad, chb (25-30) inserting abaxially. Length of movable digit ~35. Trägårdh's organ (To, 50) inserting paraxially. Palp (75–80) with long femur and long tarsus, setal formula 0–2–1–3–9 (+ solenidion ω), setae with short bristles. Length of ω 12, attached to eupathidial seta acm. Postpalpal seta spiniform (pps, 4).

Lateral aspect of podosoma — Pedotectum I (PtI) large, pedotectum II (PtII) small scale posterior to trochanter II. Discidium (dis) triangular, projecting laterally. Circumpedal carina (cp) merging into custodium. Custodium (cus) with long free acute tip extending anterior of pedotectum II. Humeral porose areas Am (~20 x 10), Ah (~15–20 x 10) indistinct, oval to round, Ai small (~10–12 x 8), ventral to bothridium.

Epimeral region — Apodemes I complete and fused medially, apodemes II and III as well as sejugal apodemes medially incomplete. Epimeral setal formula 3–1–3–3, all setae setiform with very short bristles, length 25–35.

Anogenital region — Genito-anal setal formula 6–1–2–3, all setiform, roughened or with very short bristles. Three pairs of anterior genital setae situated side by side on anterior thickening of genital plates, genital and anal setae ~20. Aggenital and adanal setae ~30. Anterior adanal setae ad₂ , ad₃ situated in paraanal, ad₁ in postanal position. Adanal lyrifissure (iad) short, adjacent and parallel to anal plates, level with their anterior third. Postanal porose area small, elongate (Ap, ~45–50 x 8).

Legs — Legs of medium length (50–65% of body size), length (with claws) of leg I 280–330, II 280–320, III 270–310, IV 300–350. All legs heterotridactylous, with stronger median and thin lateral claws. Setal formula of legs (trochanter to tarsus, famulus included, solenidia in parentheses): leg I 1–5–3(1)–4(2)–20(2), leg II 1–5–3(1)–4(1)–16(2), leg III 2–3–1(1)–3(1)–15, leg IV 1–2–2–3(1)–12. All femora thickened ventrally, trochanters III and IV with a dorsal blade each. Setae l″ on genua and tibia of setae I and II as well as setae l′ on setae III and IV thicker than other setae, rather spiniform (40–55) with short bristles. Other setae setiform with short bristles, setae (pv) and (a) on tarsi I-IV with longer bristles. Setae d on femora unilaterally ciliate. Solenidion φ₁ on tibia I 120–140, φ on tibia II 80–100, σ on genu I ~40, on genu II ~30. Position, length and designation of setae and solenidia as indicated in Figs 4 and 5. Large porose areas (pa) on all femora in paraxial position (40–55 x 10–15, ~40–60% of femur length) and on trochanters III, IV.

Immatures

Unknown.

Sexual dimorphism

Females larger than males, ranges slightly overlapping. Length of female genital plates (n=15) 60–75. Most females with internal ovipositor, two specimens with six or seven large eggs, size of eggs (n=13) 135–160 x 60–90, shape oval. Length of male genital plates (n=8) 55–60, longitudinal cross section of spermatopositor 20–25. Apart from differences in body size and size of genital plates, no external sexual dimorphism could be observed.

Type locality – Material examined

Galapagos Islands, Isabela Island, Sierra Negra, west of Villamil, near the site of the ''muro de las lagrimas'', arid zone, open bushland with Opuntia insularis, Zanthoxylum fagara, Croton scouleri var. scouleri, Heliotropium angiospermum, in dry to moist decayed cactus litter under Opuntia insularis (8 Feb. 1987, 30 m a.s.l., 0°57.96′ S, 91°00.88′ W, leg. H. Schatz). Holotype female, six paratypes (two females, four males). Additionally, several specimens from other sites and islands were used for measurements and morphological analyses.

Type deposition

The holotype and six paratypes from the type locality, preserved in ethanol, are deposited in the collection of the Senckenberg Museum, Görlitz, Germany (SMNG). Additional material is deposited in the collection of the author, which will finally also be placed in the Senckenberg Museum, Görlitz.

Etymology

The specific epithet yupanqui is a noun in apposition and refers to the tenth Inca emperor Túpac Inca Yupanqui (governing 1471–1493). According to an unconfirmed legend he led a voyage of exploration into the Pacific around 1480. He is said to have visited islands he called Niñachumbi (''Island of Fire'') and Auachumbi (''Outer Island''), perhaps two of the Galapagos Islands, but other authors suggest that the voyage went as far as Easter Island or islands in French Polynesia (Bericat 2020). The voyage is mentioned in the History of the Incas by Pedro Sarmiento de Gamboa (1572), but some historians are skeptical that the voyage ever took place (https://en.wikipedia.org/wiki/Topa_Inca_Yupanqui ).

Records from the Galapagos Islands

H. and Irene Schatz coll., unless other collector names given.

A total of 147 adult specimens of Ceratozetes yupanqui n. sp. was found on five islands of the Galapagos archipelago (Fig. 6). No morphological differences between the populations on different islands and sites were observed.

Isla Fernandina — Western part of the island, moist (Psychotria) zone – Elfin Forest / Fern-sedge zone: at ''Green crater'', in dry to moist leaf litter and pieces of wood under Tournefortia pubescens (15 March 1985, 550 m a.s.l., 1 adult).

Isla Isabela – Volcano Wolf — Moist (Psychotria) zone – Elfin Forest / Fern-sedge zone: open forest with Bursera graveolens, Psidium galapageium, Zanthoxylum fagara, in moist decayed leaf litter and humus (23 March 1988, 800 m a.s.l., 15 adults, L. Baert, K. Desender, J.P. Maelfait coll., their loc. #71); ibid., open forest with of Opuntia insularis, Scalesia microcephala, Lantana peduncularis, Zanthoxylum fagara, various fern species and grasses, in moist grass and leaf litter, pieces of wood and soil (23 March 1988, 1425 m a.s.l., 4 adults, L. Baert, K. Desender, J.P. Maelfait coll., their loc. #74).

Isla Isabela – Volcano Alcedo — Arid zone: Northeastern base of the volcano, dry forest with Bursera graveolens, Waltheria ovata, Lantana peduncularis, Castela galapageia, mixed with Opuntia insularis; under Bursera and Waltheria, in dry leaf litter (26 March 1988, 290 m a.s.l., 5 adults); northeastern slope of the volcano, upper Arid zone (at ''first shade tree» Pisonia floribunda), open woodland with Waltheria ovata, Macraea laricifolia (Fig. 7B); under Waltheria, Trema micranta, in dry grass, leaf litter and soil (25 March 1988, ~350 m a.s.l., 6 adults). Moist (Psychotria) zone – Elfin Forest / Fern-sedge zone: Northeastern slope of the volcano, open forest with Darwiniothamnus lancifolius and Scalesia microcephala, in litter under Darwiniothamnus, (25 June 1991, 700 m a.s.l., 51 adults, S. Abedrabbo coll., her loc. #8); ibid., under Pisonia floribunda, Tournefortia pubescens, Mentzelia aspera, ferns, in dead leaves (25 June 1991, 850 m a.s.l., 5 adults, S. Abedrabbo coll., her loc. #6, 7); eastern base of crater, open forest with Bursera graveolens, under Pisonia floribunda, in moist thin moss layer and soil from ground (25 March 1988, 880 m a.s.l., 2 adults); at southern crater rim, Elfin Forest with Scalesia microcephala, Tournefortia rufo-sericea (Fig. 7C), in litter under Scalesia (25 June 1991, 1125 m a.s.l., 6 adults, S. Abedrabbo coll., her loc. #4); ibid., open bushland above fumarole, Elfin Forest with Psychotria rufipes, Scalesia microcephala, Zanthoxylum fagara, Cordia leucophlyctis, Tournefortia rufo-sericea, Panicum glutinosum, Axonopus compressus, Commelina diffusa, Heliotropium sp. (Fig. 7D), under Pteridium aquilinum, in moist decayed fern litter and humus (21 March 1988, 1060 m a.s.l., 1 adult).

Isla Isabela – Volcano Sierra Negra — Arid zone: West of Villamil, near ''muro de las lagrimas'', open bushland with Opuntia insularis, Zanthoxylum fagara, Croton scouleri var. scouleri, Heliotropium angiospermum (Fig. 7A), in dry to moist decayed cactus litter (8 Feb. 1987, 30 m a.s.l., 29 adults); ibid., near Quinta Playa, under Scalesia cordata and Pisonia floribunda, in moist partially-decayed leaf litter (8 Feb. 1987, 30 m a.s.l., 5 adults). Moist (Psychotria) zone – Pasture zone/Pampa: on northeastern crater rim above Volcano Chico, under Darwiniothamnus lancifolius and Zanthoxylum fagara, in dry to moist leaf litter and soil under Sida hederifolia (11 Feb. 1987, 950 m a.s.l., 1 adult); ibid., on southwestern crater rim, Psidium guajava, Borreria laevis, Cyperus brevifolius, Centella asiatica, Sida hederifolia, in moist decayed leaf litter with pieces of wood and soil (11 Feb. 1987, 940 m a.s.l., 1 adult).

Isla Pinta — Upper Arid zone: southern part of the island, forest of Bursera graveolens and Croton scouleri var. scouleri (Fig. 7E), in dry leaf litter, pieces of wood and soil under Darwiniothamnus tenuifolius (2 April 1988, 200 m a.s.l., 3 adults); near eastern crater, open forest with Macraea laricifolia, Darwiniothamnus tenuifolius, Opuntia galapageia var. galapageia, in dry leaf and needle litter under Macraea (31 March 1988, 380 m a.s.l., 1 adult).

Isla Pinzón — Arid zone: Eastern part of the island, under Croton scouleri and Cordia lutea, in moist partially-decayed leaf litter (31 Jan. 1987, 100 m a.s.l., 1 adult); ibid., in dry leaf litter and humus (3 Feb. 1987, 140 m a.s.l., 2 adults); Upper Arid zone, western part of the island, Central valley, Croton scouleri forest with Lantana peduncularis, Acacia macracantha, Cordia leucophlyctis, in dry to moist dead grass litter and humus under Acacia (30 Jan. 1987, 270 m a.s.l., 1 adult); ibid., in dry to moist decayed litter and fine humus under Croton (2 adults); ibid., in dry to moist lichens from barks of Croton (1 adult); ibid., in moist decayed cactus litter under Opuntia galapageia var. macrocarpa (30 Jan. 1987, 290 m a.s.l., 1 adult); southern crater rim of main caldera near summit, Scalesia zone, open bush forest of Scalesia incisa, Croton scouleri, Lantana peduncularis (Fig. 7F), in moist leaf litter and pieces of wood under rock (31. Jan. 1987, 310 m a.s.l., 2 adults).

Isla San Cristóbal — Moist (Miconia) zone / Fern-Sedge zone: shore of lake El Junco (Fig. 7G), in mud among rushes (Eleocharis acutangula) (1. Jan. 1987, 630 m a.s.l., 1 adult, H. E. Pehofer coll.).

Distribution and microhabitats of Ceratozetes yupanqui n. sp.

With one exception, all records of the new species are from the western islands of the archipelago, most from three volcanoes of Isabela Island (V. Wolf, V. Alcedo, V. Sierra Negra), from Pinzón and Pinta. It was found in moister habitats of higher altitudes of the volcanoes in decayed leaf litter and humus, in grass litter, also in the arid lowlands where the species occurs in dry leaf litter of open forests and in decayed cactus litter.

The finding of a single specimen in the mud of the only freshwater lake of Galapagos in the highlands of the easternmost island of San Cristobal is remarkable. One possible explanation for this record is an epizoochorous dispersal by magnificent frigate birds (Fregata magnificens), which constantly come to the lake to preen their feathers and bathe in the lake (own observation, Gerecke et al. 1995). The oribatid mite could have adhered to the plumage of the bird from a nest on the western islands. Transport of mites by birds has been reported at several occasions (e.g. Krivolutsky and Lebedeva 2002, Lebedeva 2012, Lebedeva and Poltavskaya 2013).

Family Humerobatidae Grandjean, 1971

Genus Humerobates Sellnick, 1928

Type species: Humerobates rostrolamellatus Grandjean, 1936 (Notaspis humeralis Hermann sensu Sellnick 1928)

Humerobates rostrolamellatus Grandjean, 1936

Humerobates humeralis Sellnick 1928: p. 11, fig. 13. Humerobates rostrolamellatus Grandjean 1936: p. 77, fig. 8 b; Sellnick 1959: p. 124, fig. 5 a, b; Pérez-Íñigo 1993: p. 162, figs 61 a-c; Weigmann 2006: p. 396, figs 211 h, i. Porozetes sp. Schatz 1998: p. 387.

The species is frequently cited in distribution lists, including studies on arboricolous mites, especially on fruit trees (De Giosa and Barretto 2022), and is used as bioindicator of air pollution (e.g., André et al. 1984). However, few descriptions exist. The single specimen examined from Galapagos is morphologically consistent with the descriptions by Grandjean (1936); Pérez-Íñigo (1993) and Weigmann (2006). Additional morphological features based on the Galapagos specimen are presented here.

Body size — (female). 670 x 450.

Supplementary description — Color chestnut brown, surface smooth. Rostrum rounded and slightly protruding in dorsal aspect. Prolamella well visible, anterior tips of prolamellae forming small attenuating teeth laterally. Lamellar cusp short, broader than insertion of lamellar seta. Translamella narrow, continuous. Prodorsal setae setiform with very short bristles, rostral (ro, 130) and lamellar setae (le, 180) directed anteromediad, interlamellar setae longer (in, 200), inserting on anterior margin of notogaster, directed anterolaterad. Bothridial seta (bs) short, with small stem, head almost round (diameter 15–18), spoon-shaped. Tutorium long and small blade (tu, 150), laterally rounded and protruding, anterodistal edge rounded with small tip dorsally (Remark #3). Exobothridial seta long (ex, 60), with very short bristles, insertion posterolateral to bothridium, partially hidden under pedotectum I. Humeral porose area Ai small, oval (15 x 10), anterolateral to bothridium. Notogaster very broad, almost round, convex, anterior margin slightly projecting anteriad. Pteromorph well developed, movable, triangular, radially striated. Notogastral setae very short (6–10), attenuating, inserting in small indentations. Four pairs of oval porose areas, Aa very small and long (10–15 x 50). Postanal porose area small, elongate (Ap, ~10 x 110), hidden under posterior notogastral tectum. Length of epimeral, genital, aggenital, anal setae ~20–30. Epimeral setal formula 3–1–3–3. Setal formula of legs (trochanter to tarsus, famulus included, solenidia in parentheses): leg I 1–5–3(1)–4(2)–20(2), leg II 1–5–3(1)–4(1)–15(2), leg III 2–3–1(1)–3(1)–15, leg IV 1–2–2–3(1)–12. Solenidion φ₁ on tibia I 200, σ on genu I 120. Two eggs, size 220 x 130, 180 x 80, shape oval.

Record from the Galapagos Islands

H. and Irene Schatz coll.

Isla Floreana — Cerro Pajas, southwestern crater rim, moist highland (Fig. 7H): in moist partially-decayed leaf litter from ground in bushy forest under Zanthoxylum fagara, Croton scouleri var. brevifolius (19. Jan. 1987, 550 m a.s.l., 1 adult). (see Remark #4).

Remarks

1. Number of notogastral setae in Ceratozetes yupanqui n. sp.

The occasional presence of the alveolus of seta c₃ in some specimens, even rarely as a thin vestigial seta, supports the generic definition proposed by Behan-Pelletier (1984) which includes species with 10 and 11 notogastral setae in the genus Ceratozetes. To ensure this relationship, a total of 54 individuals (randomly selected from samples with this species from all islands and vegetation belts) were checked for the presence or absence of c₃ . The presence of this alveolus (or seta) in the populations of Ceratozetes yupanqui n. sp. on different islands in Galapagos does not show any correlation with occurrence on islands, altitude, vegetation belt, or sex (Table 1). There is no indication of a possible species splitting on the Galapagos Islands.

2. Morphological differences of Ceratozetes yupanqui n. sp. compared to C. platyrhinus and C. platyrhinoides

Among all Ceratozetes (and ''Ceratozetella'') species previously known only two species have a broadened rostrum without incisions, both reported from South America. Hammer (1958) described Ceratozetes platyrhinus from Bolivia. In 1961, Hammer published an additional record of this species with variations of another specimen from Peru; in the same study she described C. platyrhinoides Hammer, 1961 from Peru, based on a single specimen. The latter species was meanwhile recorded from Antigua, Cuba, Ecuador, Venezuela, but without any further description; Magellozetes mahnerti Mahunka, 1984, described from Paraguay, is considered to be a synonym of Ceratozetes platyrhinoides (Balogh and Balogh 1990; Subías 2022).

Both findings of C. platyrhinus (Hammer 1958, 1961) show morphological differences to C. yupanqui n. sp.: Lamellar cusp triangular and much broader; lamellar seta shorter in the new species; bothridial seta rounded at distal end (vs. smaller and pointed at the tip in C. platyrhinus, see Hammer 1961, her fig. 108c); tutorium with long free protruding tip (vs. short tip in C. platyrhinus, although the free tip in the specimen from Peru is slightly longer, Hammer 1961: p. 113); notogastral setae considerably longer; notogastral porose areas smaller, Aa oval in C. yupanqui n. sp. (vs. almost round in C. platyrhinus).

Compared to C. platyrhinoides, the new species differs morphologically by following species-specific characters: lamellar cusp shorter and broader; lamellar seta shorter; bothridial seta round at distal end in C. yupanqui n. sp. (vs. pointed in C. platyrhinoides, Hammer 1961, her fig. 109a; in the possible synonym Magellozetes mahnerti the bothridial seta is also round distally but with more broadened head, Mahunka 1984, his fig. 87); notogastral setae considerably longer; notogastral porose areas smaller and oval, never framed by a chitinous ring in C. yupanqui n. sp. (vs. larger and round in C. platyrhinoides; larger and round and framed by a thick chitinous ring in Magellozetes mahnerti). Noticeable common features of the new species with ''Magellozetes mahnerti'' are the shape of the rostrum tip with downward curved sides and the long free tip of the tutorium (Mahunka 1984, displayed in his fig. 87).

3. Tutorium Humerobates

Sellnick (1959) and Pérez-Íñigo (1993) accentuate the differences in the shape of the tutorium. The distal front and its small tip can be used as species (subspecies) specific character. Ohkubo (1982) points out that this character can also exhibit individual variations within a species. The specimen from Galapagos generally shows the usual shape of the tutorium of Humerobates rostrolamellatus, with very faint tip representing the anterior end of a chitinous thickening in the tutorium.

4. Humerobates species in the Neotropical Realm

From the Neotropical realm only one questionable record of Humerobates rostrolamellatus has been reported so far from Mexico (Hammer 1969, sub Humerobates sp. ?fungorum, found at a plant quarantine station in the U.S.A. and brought with orchids from Mexico). Another species of the genus (Humerobates flechtmanni Pérez-Íñigo & Pérez-Íñigo jr., 1993) is known from Brazil and Venezuela.

Humerobates rostrolamellatus differs from H. flechtmanni by the broader shape of the notogaster (almost round, ratio length/width 1,08 vs. smaller in H. flechtmanni – ratio 1,25, Pérez-Íñigo and Pérez-Íñigo jr. 1993, their fig. 1), translamella (continuous in H. rostrolamellatus from Galapagos vs. interrupted in H. flechtmanni - albeit, in other populations of H. rostrolamellatus the translamella is very faint to interrupted), by the shorter tip of the tutorium, by the shape of notogaster (nearly round vs. much narrower), by the presence of notogastral setae (very short vs. presented only as alveoli in H. flechtmanni), by the shape of the porose area A₁ (oval vs. irregular formed in H. flechtmanni).

The origin of Humerobates rostrolamellatus on the Galapagos Island of Floreana is uncertain. One possible explanation is the introduction by European settlers with agricultural products in the first half of the 20th century (Treherne 1983).

Acknowledgements

The logistic support by the Charles Darwin Foundation, the Charles Darwin Research Station, the Servicio Parque Nacionál Galápagos, Ecuador, and the Institutes of Ecology and Zoology, University of Innsbruck, Austria, is gratefully acknowledged, as are the collecting permits from the authorities of Ecuador. I wish to express my warmest thanks to all friends in Galapagos who made our collecting trips possible, namely Henning E. Adsersen for the memorable excursion to the remote places on the western side of Fernandina, the late Felipe Cruz for the common collecting trip on Cerro Pajas, Floreana, and the late Margaret Wittmer for her hospitality during our stay in Floreana, also to all persons who provided the mite material at my disposal: Sandra Abedrabbo-Randl, Harald E. Pehofer, Léon Baert and his late colleagues Konjev Desender and Jean-Pierre Maelfait, as well as Badamdorj Bayartogtokj and Tobias Pfingstl for their valuable suggestions and comments on the manuscript. Special thank deserves my wife Irene Schatz, who accompanied all steps of this work, from assisting in the field until proofreading of an earlier version of this manuscript.

This publication is contribution number 2629 of the Charles Darwin Foundation for the Galapagos Islands.

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