Zoosyst. Evol. 97 (1) 2021, 97–109 | DOI 10.3897/zse.97.52354 A new representative of the genus Bryocyclops Kiefer, 1927 from a karst cave in north-eastern Thailand (Copepoda, Cyclopoida, Cyclopidae) and comments on the generic affinities Santi Watiroyram1 1 Division of Biology, Faculty of Science, Nakhon Phanom University, Nakhon Phanom, 48000, Thailand http://zoobank.org/C786D024-63D4-474C-8F54-A9101E246312 Corresponding author: Santi Watiroyram ([email protected]) Academic editor: Kay Van Damme ♦ Received 23 March 2020 ♦ Accepted 29 August 2020 ♦ Published 3 February 2021 Abstract The seventh Thai species of Bryocyclops Kiefer, 1927 – Bryocyclops jayabhumi sp. nov. – was found in a karst cave in the Chai- yaphum Province of north-eastern Thailand. The new species differs from all previously-known species by the absence of an inner seta on the proximal endopod of the first four swimming legs. Bryocyclops jayabhumi sp. nov. is most similar to B. maholarnensis Watiroyram, Brancelj & Sanoamuang, 2015 – the monotypic species of Group VII, which was previously described from Thailand. However, the new species differs from B. maholarnensis by having the following characteristics: i) posterior margin of urosomites serrated; ii) anal operculum triangular with acute-tip; iii) P1–P4 Enp-1 without an inner seta; iv) armature on the female P2–P3 Enp-2 and P4 Enp; v) a transformed spine on the male P3 Enp-2. In this study, the generic affinity of the genus Bryocyclops Kiefer, 1927 is discussed and redefined, based on the available literature concerning its principle morphology to fill the present knowledge gap about the characteristics of the genus. Key Words cave fauna, epikarst, groundwater, Southeast Asia, Thailand Introduction including Bryocyclops maholarnensis Watiroyram, Brancelj & Sanoamuang, 2015; B. muscicola (Menzel, North-eastern Thailand (locally called ‘Isan’) is located 1926); Elaphoidella bidens decorata (Daday, 1901); and on the Khorat Plateau and encompasses approximate- E. namnaoensis Brancelj, Watiroyram & Sanoamuang, ly 200,000 km2 or one-third of the country (Smith and 2010 (Watiroyram et al. 2017; Watiroyram 2018). Stokes 1997). Its major geographic features are the plains The genus has, so far, been divided into seven species and mountain ranges along the region’s western edge (i.e. groups (I–VII) and four subgenera: Bryocyclops s. str.; Phetchabun Mountain), especially in the Loei, Nong Bua Haplocyclops Kiefer, 1952; Palaeocyclops Monchenko, Lam Phu and Chaiyaphum Provinces. Two faunal groups 1972; and Rybocyclops Dussart, 1982. The latter three (snails and geckos) have been intensively researched have been further split into the three different genera (Kief- in the caves in this area (Ellis and Pauwells 2012; Pau- er 1927; Lindberg 1953, 1956; Monchenko 1972; Dussart wels et al. 2014; Tumpeesuwan and Tumpeesuwan 2014; 1982; Rocha and Bjornberg 1987; Ranga Reddy and De- Tanmuangpak 2015), but few studies have focused on faye 2008; Watiroyram et al. 2015; Fiers and Van Damme aquatic invertebrates, though the region boasts highly di- 2017). Recently, a species of Group II – B. soqotraensis verse, cave-dwelling fauna – especially Copepoda (Wa- Mirabdullayev, Van Damme & Dumont, 2002 – was tiroyram et al. 2015, 2017). To date, four cave-dwelling re-evaluated and given to a new genus: Thalamocyclops copepods have been reported in north-eastern Thailand, Fiers & Van Damme, 2017 (Rocha et al. 1998; Fiers 2002; Copyright Santi Watiroyram. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 98 Santi Watiroyram: Bryocyclops jayabhumi sp. nov. from a cave in north-eastern Thailand Fiers and Van Damme 2017). In addition, Fiers and Van Sampling and specimen preparation Damme (2017) note that the species of Groups I, II and VII (Lindberg 1953; Watiroyram et al. 2015) share gener- Samples were collected using a hand net (60 µm) from ic affinities and a common lineage, but species of Group drip pools on the stalagmites and the cave floor and III (B. constrictus Lindberg, 1947; B. travancoricus Lind- then fixed immediately in ca. 70% ethanol. Adult ani- berg, 1947) and Group IV (B. africanus Kiefer, 1932); mals were picked out and preserved with 70% ethanol Bryocyclops (Palaeocyclops) jankowskajae Monchenko, in 1.5 ml microtube. Adult specimens were dissected 1972 present different lineages that are clearly unrelated to under an Olympus SZ51 stereomicroscope in a mixture Bryocyclops s. str. (Reid and Spooner 1998; Fiers 2012). of glycerol and 70% ethanol (ratio ~ 1:10 v/v). Dis- Based on the available literature and the discovery of the sected specimens were mounted in pure glycerol and new species described herein, this study discusses and up- sealed with transparent nail polish. Permanent slides dates the generic affinity of Bryocyclops Kiefer, 1927. with dissected animals were examined with an Olympus compound microscope (CX31) at 1000× magnification. Pencil drawings were made with a drawing tube (an Materials and methods Olympus U-Da) mounted on a compound microscope, then the final drawings were scanned for correction in Site description the CORELDRAW 12.0 graphic programme. Specimens for scanning electron microscopy (SEM) were dehydrat- Chaiyaphum Province sits in the westernmost edge of this ed in progressive ethanol concentrations (70%, 80%, plateau, mostly covered by Triassic-Tertiary sedimentary 90%, 95%, 100% and 100% absolute ethanol) for 15 min rocks and Permian limestone (Singtuen and Won-In 2018). each concentration. Specimens were dried in a critical The Prakai Phet cave of Chaiyaphum Province, located in point dryer using liquid carbon dioxide as the exchange the Phetchabun Mountain Range, is made of dolomitic medium. Dried specimens were mounted on stubs using limestone karst formed in the Permian Period and it served adhesive tape under the stereomicroscope. Specimens as a refuge for several Pleistocene mammals (Filoux et were coated with gold in a sputter-coater. The SEM pho- al. 2014). This cave is about 1.5 km long, ending in a 45 tographs were made using a scanning electron micro- m-deep abyss and only 15 m of the cave’s anterior is open scope (LEO 1450 VP). to tourists. The present author visited the cave in the rainy The morphological terminology follows Huys and season once a year – September and October 2017–2019 Boxshall (1991). Specimens were deposited at the Natural – and a single population of the new copepod on the floor History Museum, London, United Kingdom (NHMUK) and stalagmites, which are formed by dripping water, was and the Nakhon Phanom University, Faculty of Science, collected at about 4–5 m from the cave’s entrance (Fig. 1). Thailand (NPU). Figure 1. The sampling site and habitat of B. jayabhumi sp. nov.: A. Sampling site indicated with white circle (○); B. The entrance of the cave; C. Dripping water from the plant roots penetrating from the surface; D. pool on stalagmite. zse.pensoft.net Zoosyst. Evol. 97 (1) 2021, 97–109 99 Abbreviations structures and P6 dorsolaterally; posterior margin with slightly irregular serrated hyaline fringe. Copulatory pore The following abbreviations are used throughout the text (Fig. 3I) behind one-half length of segment; copulatory and figures: duct narrow, short, strongly sclerotised. Seminal recep- tacle with anterior expansion at about one-half length of A aesthetasc; anterior portion; lateral arm narrow, slightly posteriorly Enp endopod; curved. Urosomites 3–4 (Fig. 2E, G) shorter than wide, Exp exopod; 1.6 times as long as wide (n = 5); ornamented with trans- Exp/Enp-n exopodal segment n/endopodal segment n; verse row of shallow pits dorsolaterally; narrow serrated P1–P6 swimming legs 1–6; hyaline fringe. Anal somite (Fig. 2E, G) short, 1.6 times Sp spine/spines. as long as wide (n = 5); two dorsal sensilla at base of anal operculum; transverse row of spinules distally on ven- tral and dorsolateral side. Anal operculum (Fig. 2E) well Taxonomic section developed, extended to tip of caudal ramus; triangular, acute tip; free margin smooth. Caudal ramus (Fig. 2E, G) Order Cyclopoida Rafinesque, 1815 asymmetrically conical, about 1.5 times as long as wide, Family Cyclopidae Rafinesque, 1815 with dorsal longitudinal keel. Lateral seta (II) bare, slight- Genus Bryocyclops Kiefer, 1927 ly shorter than caudal ramus, inserted at one-half of cau- dal ramus length. Outermost terminal seta (III) bipinnate, longer than caudal ramus, with spinules at insertion point Bryocyclops jayabhumi sp. nov. on ventrolateral side. Outer terminal seta (IV) bipinnate, http://zoobank.org/8A037BC7-5D7F-4EC3-961B-EA1A6F9897F8 about 4.0 times as long as caudal ramus, with fracture Figs 2–6 plane. Inner terminal seta (V) bipinnate, about 6.0 times as long as caudal ramus, with fracture plane. Innermost Type locality. A rimstone pool that is close to an entrance terminal seta (VI) bare; short. Dorsal seta (VII) bipinnate, (see site description) in the Prakai Phet Cave (Fig. 1), about 2.0 times as long as caudal ramus, inserted at distal Thung Luilai Subdistrict, Khon San District, Chaiya- end of longitudinal keel. phum Province, north-eastern Thailand; coordinates of Antennule (Fig. 3A). Eleven-segmented, not reach- cave entrance: 16°29'03"N, 101°47'05"E, altitude: 573 m ing posterior margin of cephalothorax, ornamented above sea level. with refractile points. Armature formula as follows: Material examined. Holotype: one adult female dis- 6.2.5.2.0.2.3.1+A.2.2.6+A; all setae smooth; aesthetascs sected and mounted on one slide (NHMUK 2020.48); slender, fused basally with seta as acrotheck. allotype: one adult male dissected and mounted on one Antenna (Fig. 3B). Four-segmented, coxobasis with slide (NHMUK 2020.49); paratypes: one adult female one distomedial seta. Enp-1 unarmed. Enp-2 with five dissected and mounted on one slide (NPU 2020–001), distomedial setae.