Bryocyclops maewaensis, Watiroyram & Brancelj & Sanoamuang, 2012

Watiroyram, Santi, Brancelj, Anton & Sanoamuang, La-orsri, 2012, A New Bryocyclops Kiefer (Crustacea: Copepoda: Cyclopoida) From Karstic Caves In Thailand, Raffles Bulletin of Zoology 60 (1), pp. 11-21 : 12-20

publication ID	https://doi.org/ 10.5281/zenodo.4509245
persistent identifier	https://treatment.plazi.org/id/03FB87B4-FFF0-FF9C-FC36-42F9430EFB37
treatment provided by	Carolina
scientific name	Bryocyclops maewaensis
status	sp. nov.

Treatment

Bryocyclops maewaensis , new species

( Figs. 2–6 View Fig View Fig View Fig View Fig View Fig )

Type locality. — Tham Nam Phar Ngam cave is located in Mae Wa National Park (Lampang Province, northern Thailand) (17°28'46.4"N, 99°10'03.2"E). The cave is about 300 m long, with horizontal galleries only and 1–3 m high. The entrance is under a high cliff, at an elevation of 260 m a.s.l. In a permanently dark section, there are three Buddha statues, each of them with a concrete-pool (volume of about 5 to 10 L) in front of them. Pools are filled with water dripping from the cave roof. Those pools were designed as the type locality. The largest pool on the floor was 20 cm deep, 40 cm wide, and 60 cm long, with a water temperature of 20.1°C, pH 8.9, and a conductivity of 685 μS cm–1 GoogleMaps .

Material examined. — Holotype: adult female, completely dissected, semi-permanent slide in glycerol, sealed with nail varnish (cat. no.: NHM 2011.2072). Collected 20 Mar.2008.

Allotype: adult male, completely dissected and mounted on a slide in glycerol and sealed with nail varnish (cat. no.: NHM 2011.2073). Collected 20 Mar.2008. Paratypes: three females and three males (stored in 70% ethanol), same locality and date (cat. no.: NHM 2011.2074–2079); two females and two males (cat. no.: KKU- COP-2008, 001–004). Additional material: specimens from pool on muddy floor (12 females and 7 males; cat. no.: KKU-COP-2009, 001–019) and concrete-pool (21 females and 13 males; cat. no.: KKU-COP-2009, 020–054) on type locality collected on 5 Oct.2009; 7 females and 5 males (cat. no.: KKU-COP-2009, 055–067) from pool on muddy floor in Tham Phar Ngam cave collected on 6 Oct.2009. All specimens collected by first author ( SW) .

Description. — Female ( Figs. 2–4 View Fig View Fig View Fig ), body length, measured from tip of rostrum to posterior margin of caudal rami, 350–470 μm, (mean: 420 μm; n = 10), colourless. Prosome moderately slender, dorso-ventrally flattened; cephalothorax wider than rest of body ( Fig. 2A View Fig ). Naupliar eye not discernible. Cephalosome (incl. rostrum), pedigers 2–5, genital double-somite, urosomites, and anal somite (incl. anal operculum) covered with light spots. Cephalosome with dorsal cuticular pores postero-laterally. Posterior margins of cephalosome and pedigers 2–4 with dorsally irregularly serrated hyaline frills. Genital double-somite ( Fig. 2 View Fig B–E) symmetrical, slightly expanded anteriorly, about 1.2× as wide as long, with irregularly serrated posterior fringes on dorso-ventral margin, latter ornamentation also on two subsequent urosomites. Genital double-somite with pair of dorsal sclerotized and rounded structures accompanied by three minute spinules on inner margin; single copulatory pore ventrally. Anal somite ( Fig. 2B, C, E View Fig ) with transverse row of spinules along posterior margin on dorso-ventral surface.

Anal operculum ( Fig. 2A, B, E View Fig ) prominent, ovate, irregularly serrated along distal margin, overreaching posteriorly to approximately 1/2 of caudal rami length. Caudal rami ( Fig. 2B, C View Fig ) asymetrically conical, each about twice as long as wide, with dorsal longitudinal keel along distal 1/3 of its length. Inner margin smooth. Lateral seta (II) bare, slightly shorter than caudal ramus, inserted at about the middle of its length. Dorsal seta (VII) bare, longer than caudal ramus, inserted at distal end of the keel. Outermost terminal seta (III) pinnate, slightly longer than dorsal seta, with spinules at insertion point on ventral side. Outer terminal seta (IV) about 3× as long as caudal ramus, about distal two-thirds with hairs on both margins, breaking plane not visible. Inner terminal seta (V) approximately 5× as long as caudal ramus, distal two-thirds with same arrangement of hair-like structures as on outer terminal seta, with no discernible breaking plane. Innermost terminal seta (VI) bare; relatively long, reaching 1/2 length of caudal ramus.

Rostrum ( Fig. 3F View Fig ) fused to cephalothorax, as long as width in frontal view, with parallel margins, blunt, anteriorly rounded; with pair of circular pores; dorsal surface smooth.

Antennule ( Fig. 3A View Fig ) relatively short, 11-segmented, not reaching posterior margin of cephalothorax; with refractile points on external surface (as on somites). Setal formula from base to tip as follows: 6.2.5.2.0.2.3.1+A.2.1+A.7+A. All setae slender.

Antenna ( Fig. 3B View Fig ) 4-segmented, comprising coxobasis and three-segmented endopodite. Exp absent. Endp-1 laterally with row of spinules; one inner seta at 2/3 of its length. Endp-2 with five smooth setae (three lateral, one subapical and one apical); with a row of spinules on outer margin. Endp-3 with seven terminal setae; with a row of spinules on outer margin.

Mandible ( Fig. 3E View Fig ) short, robust, with three strongly chitinized teeth on gnathobase; with short, smooth dorsal seta. Mandibular palp reduced to one bare and short seta inserted directly on gnathobase.

Maxillule ( Fig. 3D View Fig ) with robust praecoxa, coxobasis and 1- segmented Endp. Praecoxal arthrite with three strong apical spines fused to arthrite base; with six armature elements along inner margin, proximally one pinnate, others smooth. Coxobasis with two setae distally on basal endite: one slender and smooth, other one strong and pinnate. Exp represented by single smooth seta on outer surface of coxobasis. Endp with three slender and smooth setae.

Maxilla ( Fig. 3C View Fig ) 5-segmented, with praecoxa, coxa, basis, and 2-segmented Endp. Praecoxal endite with two plumose setae. Proximal coxal endite with single plumose seta; distal coxal endite highly mobile, with one smooth and one plumose setae. Basis with typically two claw-shaped expansion, densely serrate along concave margin; with one small seta at base of distal claw. Endp-1 with one smooth seta. Endp-2 with one smooth seta and two strong setae.

Maxilliped ( Fig. 3G View Fig ) 4-segmented, composed of syncoxa, basis and 2-segmented Endp. Syncoxa and basis with a row of spinules on outer margin. Syncoxa with one pinnate and one smooth seta. Basis with one unipinnate seta, accompanied with a row of long spinules at proximal inner margin. Endp-1 with one unipinnate seta at inner margin. End-2 with small segment plus two smooth setae.

P1 ( Fig. 4A View Fig ) with 2-segmented Exp and 2-segmented Endp. Endp smaller than Exp. Intercoxal sclerite with acute projection on distal margin. Coxa with one slender inner seta; with row of spinules laterally and pointed process laterodistally. Basis with slender outer seta and strong, robust inner spine with cluster of spinules at insertion point; setules on distal inner corner. Inner and outer margin of Exp and Endp, respectively, with setules. Exp-1 smaller than Exp-2; with outer spine. Exp-2 with two spines along outer margin, plus one spine and one seta apically, four setae along inner margin. Endp-1 and Endp- 2 with row of long spinules along outer margin. Endp-1 with one seta on inner margin. Endp-2 with one seta on inner margin, one spine and one seta terminally, one seta on outer margin.

P2 ( Fig. 4B View Fig ) similar to P1, but coxa without inner seta; basis without inner spine. Intercoxal sclerite with acute projection on distal margin. Exp and Endp-1 similar to those in P1. Endp-2 with one seta on outer margin, one spine and one seta terminally, two setae along inner margin; row of long spinules along outer margin.

P3 ( Fig. 4C View Fig ) coxa without inner seta, basis with slender outer seta. Intercoxal sclerite with acute projection on distal margin. Inner and outer margin of Exp and Endp, respectively, with setules. Exp similar to those in P2. Two distal-most setae on inner margin of Exp-2 blunt. Endp-1 similar to those in P2. Endp-2 with one seta on outer margin, one spine and one seta terminally, three setae along inner margin.

P4 ( Fig. 4D View Fig ) coxa without inner seta; basis with slender outer seta. Intercoxal sclerite with acute projection on distal margin. 2-segmented Exp and Endp. Endp smaller than Exp. Exp-1 and Endp-1 similar to that of P3. Exp-2 with two outer spines, one spine and one seta terminally and three setae along inner margin; inner margin with a row of long spinules. Endp-2 slightly larger than Endp-1, with spiniform seta on outer margin, one spine and one spiniform seta terminally, spiniform seta on inner margin.

P5 ( Fig. 2F View Fig ) with basal segment completely fused to fifth thoracic somite; with three slender setae. Proximal segment represented by single slender naked seta on low prominence. Distal segment with two naked setae; inner seta about twice as long as outer one.

P6 ( Fig. 2D View Fig ) reduced, fused, forming simple cuticular plate; inserted latero-dorsally on genital double-somite, with two minute spines ventrally and one short seta dorsally.

Adult female with a pair of egg sacs, each contains two large eggs.

Male ( Figs. 5 View Fig , 6 View Fig ), slightly smaller than female; body length, excluding caudal setae, 340–450 μm (mean: 380; n = 10). Body shape generally similar to female, except for genital section ( Fig. 5A View Fig ). Antennae, mouthparts, P1 ( Fig. 6A View Fig ), P2 ( Fig. 6B View Fig ), P3–P4 exopods ( Fig. 6C, D View Fig ) as in female. Anal operculum ( Fig. 5A, B View Fig ) slightly longer than in female, more or less triangular shape with rounded tip. Caudal rami similar to female, but lacking dorsal keel.

Antennule ( Fig. 5E View Fig ) 15-segments. Setal formula as follows: 7+2A.4.2.4+A.4.1+A.1.1+A.3.1.1.1+A.1.4.6+A. Seta on segment 9 stout. Segment 12 with strong spinules distally. All setae smooth, segments 9 and 12 with one and two unipinnate setae, respectively.

P3 ( Fig. 6C View Fig ) Endp 2-segmented; proximal segment smaller than terminal one. Outer margin of Endp-1 & Endp-2 setulated. Endp-1 with inner seta. Endp-2 with spiniform terminal seta; two plumose setae along inner margin. Terminal spine modified, with subapical, bulbous, smooth expansion and acute, hooked end. Distance between hooked tip of modified spine and its subterminal bulbous on Endp-2 very short.

P4 ( Fig. 6D View Fig ) Endp 2-segmented; proximal segment slightly shorter than wide. Outer margin of Endp-1 & Endp-2 with setules. Endp-1 with seta on inner margin. Endp-2 with one seta on inner and outer margin; terminally one spine and one seta. Setae soft and longer than in female.

P5 as in female.

P6 ( Fig. 5 View Fig B–D) reduced to simple plate, represented by three bare setae, longer than in female, ventral-most the longest and dorsal-most the shortest.

Etymology. — The new species is named after Mae Wa National Park, the place where it was found for the first time. The name is an adjective agreeing in gender with the (feminine) generic name.

Differential diagnosis and remarks. — With fused P5 to somite bearing it, basis of P2–P4 without inner seta, and with a modified apical spine on the male P3 Endp-2, B. maewaensis , new species, clearly fits in the genus Bryocyclops Kiefer, 1927 , s. str. The armature of the female P1 and P4, the male P3, the setal and spine formula of swimming legs exopods (5.5.5.4. and 3.3.3.3., respectively) allowed us to assign this species to Lindberg’s (1954) group I. This group includes 6 species: B. anninae ( Menzel, 1926) , B. chappuisi Kiefer, 1928 , B. apertus Kiefer, 1935 , B. difficilis Kiefer, 1935 , B. elachistus Kiefer, 1935 , and B. phyllopus Kiefer, 1935 .

Following the key by Monchenko (1972), with an anal operculum with serrated margin, about 1/2 the caudal rami length, the new species is clearly distinguished from B. apertus from Kenya. The other remarkable character is the distance between the hooked tip of the modified spine and its subterminal bulbous on the male P3 Endp-2. The distance in B. maewaensis , new species, is very short compared to that in the males of B. apertus (for details see Fig. 6C View Fig ; Kiefer, 1939: Fig. 105).

The females of the new species also differs from the African B. difficilis , which has a relatively small anal operculum and the innermost terminal seta (VI) of caudal ramus is very short and spiniform. The caudal ramus of B. difficilis has long dorsal seta, bare outermost terminal seta (III), and dorsal keel well developed compared to those in the female of B. maewaensis , new species. Additional differences between both species are also in the armature of P4 Endp- 2 in females, setae are relatively longer in B. difficilis (for details see Figs. 2A, B View Fig , 4D View Fig ; Kiefer, 1939: Figs. 91, 92).

Bryocyclops maewaensis , new species, differs from B. elachistus , another species from Kenya, too. The caudal rami are about twice as long as they are wide in B. maewaensis , new species, but less than 1.7 as long as wide in B. elachistus . Furthermore, in B. elachistus the female P4 Endp-2 bears three long setae and one short spine, vs. three short spiniform setae in the new species. The shape of the anal operculum is triangular in B. elachistus but ovate in the new species (for details see Figs. 2A, B View Fig , 4D View Fig ; Kiefer, 1939: Figs. 85, 86).

There are also differences between the new species and B. chappuisi Kiefer, 1928 , from Java. Bryocyclops chappuisi is one of five south-east Asian species but only three ( B. chappuisi , B. anninae , and B. maewaensis , new species) belong to group I sensu Lindberg (1954). Monchenko (1972) recognised B. chappuisi by having an anal operculum which is triangular and its lateral seta (II) on caudal ramus inserted toward the terminal part, whereas B. maewaensis has a more rounded anal operculum, with lateral seta (II) attached at about 1/2 length of the caudal rami.

The new species closely resembles B. anninae in habitus and cuticular ornamentation, with similar refractile points on prosome and urosome but the pattern is distinctively weaker on the urosome of the new species. The cephalosome has transverse scars indicating fusion line of cephalon and pediger 1; these characters are absent in B. anninae . The new species’ anal operculum differs markedly from B. anninae , which is irregularly acuminate and the free margin is smooth. In the new species pedigers 1–4 have irregularly serrated hyaline frills, present only on pedigers 2–4 in B. anninae . The setation of the caudal ramus is also different between B. anninae and B. maewaensis ; dorsal seta (VII) plumose and very short innermost seta (VI) in B. anninae but dorsal seta (VII) is naked in the new species, and with long innermost seta (VI). The two species differ also in the presence of a discernible fracture plane of the outer terminal seta (IV) of the caudal ramus in B. anninae , which is completely absent in B. maewaensis , new species. P2 and P3 of both species have two blunt setae on Exp-2 but with two additional blunt setae on P4 Exp- 2 in B. anninae (for details see Fig. 4 View Fig B–D; Reid, 1999: Figs. 3 View Fig F–H). P4 Endp-2 of female in B. maewaensis , new species, carries three short spiniform setae, similar in length to the apical spine, whereas in B. anninae there are three long setae. Those three spiniform setae are the most obvious discernible character of the new species. The difference in males between both species is in the anal operculum, which is, according to the original description, very small in B. anninae ( Menzel, 1926) , whereas in the new species, it is considerably larger. The innermost seta (VI) is also very short in the male of B. anninae compared to those in our specimens.

Variability. — No variability was observed, except in body length.

Distribution and ecology. — Bryocyclops maewaensis was found in North (type locality and Tham Phar Nagm cave in Jae Sorn National Park, Lampang Province) and Central Thailand (Tham Pratoon cave, Kanjanaburi Province). This species is at the moment known only from the vadose part with percolating water (e.g., from pools on muddy floor and from different types of water containers collecting exclusively dripping water) indicating their origin from the epikarstic zone of the cave.

Members of genus Bryocyclops are either epigean species, known from several types of semi-terrestrial habitats such as moist mosses, wet leaf litter, bromeliad and other plants’ leaf arm pits (Phytothelmata) or they are subterranean, usually collected from groundwater in alluvium or karstic caves (see Table 1). So far, four species (including the new one) have been described from subterranean habitats; one from well (interstitial aquifers) and three from caves (karstic aquifers). In karstic caves the following species have been found: B. absalomi Por, 1981 , from Soreq cave ( Israel); and B. soqotraensis Mirabdullayev, Van Damme & Dumont, 2002 , from Hoq cave ( Socotra Isl., Yemen). Thus, B. maewaensis is the third cave-dwelling species of the genus and the first one found in Thailandese caves.