Schusteria bruneiensis Ermilov & Marshall, 2026, sp. nov.
Year: 2026
Type: article
Abstract: Schusteria bruneiensis sp. nov. (Figs 11A–C; 12A–D; 13A, B; 14A, B; 15A–I; 16A–D; 17A–D; 18A, B; 19A–D; 20A–C; 21A–H) Type material. Holotype (male) and three paratypes (two males and one female): Brunei, Sengkurong, Empire Hotel, 4°58 ’ N, 114°51 ’ E, natural rocky shore, open ocean, benthic substratum with Saccostrea scyphophilla oysters in the shade, 10 June 2025 (collected by David J. Marshall). The holotype is deposited in the Senckenberg Museum of Natural History, Görlitz, Germany. Three paratypes are deposited in the University of Tyumen, Tyumen, Russia. All specimens are preserved in 70% ethanol with a drop of glycerol. Additional material. Four adults (collected from the type locality) were used for SEM. Two deutonymphs and one tritonymph were collected from the type locality. Sixteen adults, two protonymph, one deutonymph, and one tritonymph: Brunei, Jerudong, Pantai Jerudong, 4°57 ’ N, 114°50 ’ E, artifical rocky shore, open ocean setting, benthic substratum is Succostrea echinata oysterbed on pier wall, May 2023 (collected by David J. Marshall). Six adults and one tritonymph: Brunei, Pantai Tungku South, 4°58 ’ N, 114°51 ’ E, artifical rocky shore, open ocean setting, benthic substratum is Succostrea echinata oysterbed on breakwater, 13 October 2022 (collected by David J. Marshall). All specimens (preserved in 70% ethanol with a drop of glycerol) are in the personal collection of the first author. Diagnosis (adult). Body length 315–353. Body cerotegument heterogeneous, represented by large and small tubercles. Genital plates and region nearly depression of epimere I covered with large, dense cerotegumental tubercles forming clusters. Lamellae well-developed and distant from each other. Lamellar seta longer than rostral and interlamellar setae. Bothridial seta clavate/fusiform, barbed. Anterior margin of notogaster straight. Fifteen pairs (c 3 present) of notogastral setae short, setiform, smooth. Adoral seta or 1 slightly phylliform, while or 2 nearly acicular. One pair of anal and two pairs of adanal setae present. Adanal lyrifissure slightly oblique. Leg trochanters III and IV anterodorsally with triangular process. Description of adult. Measurements. Body length 345 (male holotype), 315, 345 (male paratypes), 353 (female paratype). Body width 210 (female holotype), 210 (male paratypes), 217 (female paratype). Integument (Figs 15A–D, I; 16A–D; 17A–D; 18A, B). Body color brown. Surface microporose and partially microsculptured with simple and oblong microtubercles (visible under high magnification in dissected specimens and via SEM; Fig. 18B). Prodorsum, notogaster, podosomal region, and anogenital region covered with distinct layer of heterogeneous cerotegument, represented by large and small tubercles, and partially obscured by dirt. Large cerotegumental tubercles forming clusters on genital plates and near depression of medial region of epimere I (Fig. 15C, D). Prodorsum (Figs 11A, C; 15A, B, E; 16A, C, D; 17A–C). Rostrum rounded, with narrow depression behind rostral margin (Fig. 16D). Transverse furrow (often appearing as ridge in dorsal view) between rostral and lamellar setae present (Figs 15A; 16A, C, D; 17A). Lamella well developed, located dorsolaterally, reaching insertion of lamellar seta. Rostral (9–11), lamellar (15), and interlamellar (9–11) setae setiform, thin, smooth. Bothridial seta (34–37) clavate/fusiform, with densely barbed head. Bothridium with lateral incision and triangular tubercle filling space of this incision (Fig. 17C). Exobothridial seta (5) acicular. Notogaster (Figs 11A, C; 15A, B; 16A, C, D; 17B, D). Anterior margin of notogaster distinct medially, straight. Lenticulus diffuse (Fig. 15A). Region between anterior margin of notogaster and setae of c -series slightly depressed (Fig. 16A, C, D). Fifteen pairs (c 3 present) of notogastral setae (19–24) setiform, smooth. Opisthonotal gland opening and all lyrifissures slightly visible. Gnathosoma (Figs 12A–D; 15C, H). Subcapitulum size 86–90 × 67–71. Anterolateral part of rutellum quadrangular (visible under high magnification in dissected specimens, in intact specimens it may illusionary appearing triangular). Subcapitular seta m (26) setiform, roughened, setae a (19) and h (26) setiform, smooth. Adoral seta or 1 (11–15) slightly phylliform, seta or 2 (5–7) nearly acicular. Palp length 64–71, setal formula 0-2-1-3- 9(+1ω). Postpalpal seta (2) spiniform. Chelicera length 71–82, setae (cha 22–26; chb 15–19) setiform, barbed. Epimeral and lateral podosomal regions (Figs 11B, C; 15C, D; 16B–D). Medial region of epimere I distinctly depressed. Epimeral setal formula 2(1)-0-1-1, seta 1c represented by alveolus, sometimes completely reduced, seta 1b (49–53) setiform, smooth, setae 3b and 4a (both 11) acicular. Pedotectum I represented by small lamina. Discidium large, triangular. One pair of lateral podosomal tubercles simple. Anogenital region (Figs 11B, C; 15B, D, I; 16B, C; 18A). Anogenital setal formula 3-0-1-2. Genital (11), anal (5–7), and adanal (7) setae acicular. Adanal seta ad 1 located posterolateral, ad 2 located lateral to anal aperture, sometimes asymmetrically (Fig. 15I). Adanal lyrifissure slightly oblique, located anterolateral to anal aperture. Legs (Figs 13A, B; 14A, B; 15F, G; 16A–D; 17A; 18B). Claw of all tarsi strong, barbed on dorsal side and with one tooth mediobasally (Figs 15G; 18B). Porose area on segments not visible. Trochanters III and IV anterodorsally with triangular process (Fig. 15F). Formulas of leg setation and solenidia: I (0-3-2-3-18) [1-2-2], II (0-3-2-3-15) [1- 1-1], III (1-2-1-2-13) [1-1-0], IV (1-2-1-3-12) [0-1-0]. Homology of setae and solenidia indicated in Table 2. Notes: Explanations see in Table 1. Setae are listed only for the instar in which they first appear, but setae and solenidia (except ω 2 on tarsus I) listed for the PN first form in the LA (Norton 1977). Description of nymphs. Measurements. Total length of PN 195, 210 (n=2), DN 255–270 (n=3), TN 300–345 (n=3). Maximum width of PN 105, 131 (n=2), DN 150–165 (n=3), TN 195–210 (n=3). Integument (Fig. 21A–H). Body color light brown to brown. Gastronotum, epimeral region, and anogenital region partially plicate. Prodorsum, notogaster, podosomal region, and anogenital region covered with distinct layer of heterogeneous cerotegument, represented by large and small tubercles. Prodorsum (Figs 19A, B; 20A, C; 21A–C, G, H). Relatively short, about 1/2 length of gastronotic region (in lateral view). Rostrum rounded. Anterodorsal part (anteromedial to bothridium) with longitudinal, faint ridge (most likely, vestigial lamella). Rostral (PN 5, DN 5–7, TN 7–9), lamellar (PN 9, DN 9–11, TN 11–15), interlamellar (PN 5, DN 5–7, TN 9–11), and exobothridial (PN 4, DN 4–5, TN 5–7) setae acicular. Bothridial seta (PN 22, DN 22–30, TN 34) clavate/fusiform, with densely barbed head. Gastronotum (Figs 19A–D; 20A–C; 21A–C, G, H). Anterior part of gastronotic region narrowed medially. Posterior part of gastronotum rounded medially. Fifteen pairs of gastronotic setae (h 2 in PN, DN 19–22, TN 22–26; p 1, p 2 in PN 7, DN 9–11, TN 15–19; other setae in PN 13, DN 15–19, TN 19–22) setiform, thin, smooth. Ecdysial cleavage line, opisthonotal gland opening, and all cupules not visible due to plications. Gnathosoma. Subcapitulum size of PN 52–56 × 49–52, DN 64–67 × 56–60, TN 67–71 × 60–64. Subcapitular setae (a of PN, DN, TN 9; m and h of PN 9, DN 11, TN 11) acicular. Adoral seta or 1 (PN 5, DN, TN 7) slightly phylliform, seta or 2 (PN 2, DN, TN 4) acicular. Palp length of PN 45–49, DN, TN 52–56, setal formula in all instars 0-2-1-3-9(+1ω). Length of postpalpal seta of PN, DN, TN 2. Chelicera length of PN 45, DN 49–52, TN 56–60, setae (cha of PN 9, DN, TN 11; chb of PN 5, DN, TN 7) acicular. Epimeral and lateral podosomal regions (Figs 19B, D; 20B, C; 21D–H). Epimeral setal formula in all instars 1-0-1-1, setae (1b in PN 19–22, DN 30, TN 37–31; 3b and 4a in PN 5, DN 7, TN 7–11) acicular. Anogenital region (Figs 19B, D; 20B, C; 21D–H). Ontogeny of genital (PN, DN, TN 5), anal (TN 5), and adanal (DN, TN 7) setal formulas, PN to TN, 1–2–3, 0–0–2, 0–2–2, respectively. All setae acicular. Paraproctal segment (AN) in DN with one pair of alveoli. Adanal cupule present in DN and TN, but poorly visible due to plications. Legs (Fig. 21D–G). Claw of all tarsi strong, barbed on dorsal side and with one tooth mediobasally. Porose area on segments not visible. Formulas of leg setation and solenidia of PN I (0-3-2-3-16) [1-1-2], II (0-3-2-2-13) [1-1-1], III (0-2-1-1-13) [1-1-0], IV (0-0-0-0-7) [0–0–0]; DN I (0-3-2-3-16) [1-2-2], II (0-3-2-2-13) [1-1-1], III (0-2-1-1-13) [1-1-0], IV (0-2-1-1-12) [0-1-0]; TN I (0-3-2-3-18) [1-2-2], II (0-3-2-3-15) [1-1-1], III (0-2-1-1-13) [1-1-0], IV (0- 2-1-2-12) [0-1-0]. Homology of setae and solenidia indicated in Table 2. Remarks. In having two pairs of adanal setae and well-developed lamellae, the adult of S. bruneiensis sp. nov. is similar to that of Schusteria saxea Karasawa & Aoki, 2005 from Japan. However, the new species can be distinguished from the latter by the structure of the anterior margin of the notogaster (straight vs. concave), the presence (vs. absence) of specific tuberculate clusters (including large tubercles on the genital plates and near the depression of the medial region of epimere I), and a longer subcapitular seta h. Juvenile instars of Schusteria were studied in S. littorea Grandjean, 1968 by Grandjean (1968). Additionally, the protonymph of S. melanomerus Marshall & Pugh, 2000 was examined by Pfingstl (2016), and all juvenile instars of S. ugraseni Marshall & Pugh, 2000 were described by Hugo-Coetzee et al. (2022). However, the inclusion of both these species in Schusteria is controversial (Pfingstl et al. 2023). Nymphal instars of all species are generally similar, sharing a plicate gastronotum and ventral side, clavate/ fusiform bothridial seta, and short prodorsal and notogastral setae. Nevertheless, th
Authors: Ermilov, Sergey G., Marshall, David J.
Institutions: University of Tyumen, Universiti Brunei Darussalam
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225642461
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