Bryocyclops jayabhumi, Watiroyram, 2021

Watiroyram, Santi, 2021, 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, Zoosystematics and Evolution 97 (1), pp. 97-109 : 97

publication ID	https://dx.doi.org/10.3897/zse.97.52354
publication LSID	lsid:zoobank.org:pub:C786D024-63D4-474C-8F54-A9101E246312
persistent identifier	https://treatment.plazi.org/id/8A037BC7-5D7F-4EC3-961B-EA1A6F9897F8
taxon LSID	lsid:zoobank.org:act:8A037BC7-5D7F-4EC3-961B-EA1A6F9897F8
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Bryocyclops jayabhumi
status	sp. nov.

Treatment

Bryocyclops jayabhumi View in CoL sp. nov. Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6

Type locality.

A rimstone pool that is close to an entrance (see site description) in the Prakai Phet Cave (Fig. 1 View Figure 1 ), Thung Luilai Subdistrict, Khon San District, Chaiyaphum Province, north-eastern Thailand; coordinates of cave entrance: 16°29'03"N, 101°47'05"E, altitude: 573 m above sea level.

Material examined.

Holotype: one adult female dissected and mounted on one slide (NHMUK 2020.48); allotype: one adult male dissected and mounted on one slide (NHMUK 2020.49); paratypes: one adult female dissected and mounted on one slide (NPU 2020-001), three adult females and three adult males preserved in 70% ethanol (NHMUK 2020.50-55), three adult females and three adult males preserved in 70% ethanol (NPU 2020-002). All specimens were collected from the type locality on 9 October 2017 by the author.

Etymology.

The species name is taken from the Sanskrit words ‘jaya’ and ‘bhumi’, meaning 'land of victory’ or ‘Chaiyaphum’ in Thai, referring to the Chaiyaphum Province, where the new species was collected.

Description.

Adult female. Habitus (Fig. 2A View Figure 2 ) cyclopiform (n = 5). Body length, excluding caudal setae, 340 μm, with prosome/urosome ratio of 1.6. Body surface ornamented with refractile points (not figured). Nauplius eye indiscernible. Prosome with length/width ratio of 1.9. Posterior margins of prosomites with smooth hyaline fringe. Cephalothorax completely fused, with several pairs of sensilla scattered dorsally on surface; pedigers 2-3 with pair of sensilla dorsally; greatest width at anterior part of cephalothorax (Fig. 2B, C View Figure 2 ). Urosome length 130-151 μm; length/width ratio of 2.2 (n = 5). Genital double-somite (Fig. 2C, D View Figure 2 ) enlarged; anterior slightly wider than posterior; 1.3 times as wide as long (n = 5), with transverse sclerotised suture indicating ancestral segmentation; with pair of dorsal sclerotised rounded structures and P6 dorsolaterally; posterior margin with slightly irregular serrated hyaline fringe. Copulatory pore (Fig. 3I View Figure 3 ) behind one-half length of segment; copulatory duct narrow, short, strongly sclerotised. Seminal receptacle with anterior expansion at about one-half length of anterior portion; lateral arm narrow, slightly posteriorly curved. Urosomites 3-4 (Fig. 2E, G View Figure 2 ) shorter than wide, 1.6 times as long as wide (n = 5); ornamented with transverse row of shallow pits dorsolaterally; narrow serrated hyaline fringe. Anal somite (Fig. 2E, G View Figure 2 ) short, 1.6 times as long as wide (n = 5); two dorsal sensilla at base of anal operculum; transverse row of spinules distally on ventral and dorsolateral side. Anal operculum (Fig. 2E View Figure 2 ) well developed, extended to tip of caudal ramus; triangular, acute tip; free margin smooth. Caudal ramus (Fig. 2E, G View Figure 2 ) asymmetrically conical, about 1.5 times as long as wide, with dorsal longitudinal keel. Lateral seta (II) bare, slightly shorter than caudal ramus, inserted at one-half of caudal ramus length. Outermost terminal seta (III) bipinnate, longer than caudal ramus, with spinules at insertion point on ventrolateral side. Outer terminal seta (IV) bipinnate, about 4.0 times as long as caudal ramus, with fracture plane. Inner terminal seta (V) bipinnate, about 6.0 times as long as caudal ramus, with fracture plane. Innermost terminal seta (VI) bare; short. Dorsal seta (VII) bipinnate, about 2.0 times as long as caudal ramus, inserted at distal end of longitudinal keel.

Antennule (Fig. 3A View Figure 3 ). Eleven-segmented, not reaching posterior margin of cephalothorax, ornamented with refractile points. Armature formula as follows: 6.2.5.2.0.2.3.1+A.2.2.6+A; all setae smooth; aesthetascs slender, fused basally with seta as acrotheck.

Antenna (Fig. 3B View Figure 3 ). Four-segmented, coxobasis with one distomedial seta. Enp-1 unarmed. Enp-2 with five distomedial setae. Enp-3 with seven apical setae, both ornamented with spinular row along lateral margin. All setae smooth.

Mandible (Fig. 3C View Figure 3 ) with six strongly-chitinised teeth; dorsal seta on gnathobase. Palp reduced to one bare seta.

Maxillule (Fig. 3D View Figure 3 ) with three strongly-chitinised teeth on precoxal arthrite; four bare setae and one pinnate seta on inner margin. Coxobasis with three bare setae distally. Exp reduced to one bare seta. Enp with three bare setae.

Maxilla (Fig. 3E View Figure 3 ) with precoxal endite with two pinnate setae. Coxa with two endites: proximal endite with one bare seta; distal endite with two bare setae. Basis with two strong claw-like expansions, bare seta close to its base. Two-segmented Enp: Enp-1 with one bare seta; Enp-2 with three bare setae.

Maxilliped (Fig. 3F View Figure 3 ). Four-segmented; syncoxa with transverse row of spinules and two pinnate setae. Basis and Enp-1-2 with one, one and two smooth setae, respectively.

P1-P4 (Fig. 4A-D View Figure 4 ). P1-P3 with two-segmented Exp and Enp; P4 with two-segmented Exp and one-segmented Enp. Armature formula (seta in Arabic numerals and spine in Roman numerals from outer-inner or outer-apical-inner margins) as follows:

	Coxa	Basis	Exp	Enp
P1	0-0	1-I	I-0; III-2-3	0-0; 1-I+1-0
P2	0-0	1-0	I-0; III-2-3	0-0; 1-I+1-0
P3	0-0	1-0	I-0; III-2-3	0-0; 1-I+1-0
P4	0-0	1-0	I-0; III-2-2	0-I+1-0

P1 (Fig. 4A View Figure 4 ). Intercoxal sclerite with acute distal margins. Coxa without inner seta. Basis with bare, slender outer seta and robust inner spine; setules on inner distal corner. Exp-1 with outer spine. Exp-2 with three spines on outer margin; two apical setae; blunt seta and two normal setae on inner margin. Enp-1 without seta on inner margin. Enp-2 with apical seta and spine; additional seta on outer margin.

P2-P3 (Fig. 4B, C View Figure 4 ). Intercoxal sclerite, coxa, basis similar to P1, but basis without inner spine. Exp-1 with outer spine. Exp-2 with three outer spines, apical normal seta and blunt seta, inner blunt seta and two normal setae. Enp-1 without inner seta. Enp-2 with apical seta and spine; additional seta on the outer margin.

P4 (Fig. 4D View Figure 4 ). Intercoxal sclerite with acute distal margins. Coxa without inner seta. Basis with slender outer seta. Two-segmented Exp. Exp-1 with outer spine. Exp-2 with three outer spines, apical normal seta and blunt seta, inner blunt seta and normal seta. One-segmented Enp, oval; with two apical pinnate setae, both shorter than segment.

P5 (Figs 2F View Figure 2 , 4E View Figure 4 ). Completely fused to somite ventrolaterally, with one long and two short pinnate setae. Proximal (dorsal) seta arising from lateral prominence; slender, longer than 4.0 times of the remaining setae; distal (ventral) setae strong, subequal in length.

P6 (Fig. 2H, I View Figure 2 ). Reduced to semi-circular plate, with three short elements: anterior seta articulated, two posterior setae fused to plate. Posterior seta as long as anterior one. Middle seta spiniform, shortest.

Egg sac (Fig. 3G View Figure 3 ). Two large eggs attached ventrally to segment, with an average egg diameter of 60 μm.

Spermatophore (Fig. 3H View Figure 3 ). The spermatophores are generally bean-shaped.

Adult male. Body length (Fig. 5A View Figure 5 ), excluding caudal rami, 320-335 µm (mean 330 µm, n = 5); smaller than female. General segmentation and ornamentation (Fig. 5A-D View Figure 5 ) similar to female. Genital somite and urosomite 3 not fused as in female, 1.8 times as long as wide (n = 5). Anal operculum (Fig. 5B, D View Figure 5 ) as in female, but shorter.

Antennule (Fig. 5E View Figure 5 ). Fifteen-segmented, geniculate. Armature formula as follows: 7+3A.4.2.2+A. 1.2.1.2.A.2.1+Sp.0.1.1.8+A.

Antenna, mouthparts, P1 (Fig. 6A View Figure 6 ) and P5 similar to those in female. Sexual dimorphism is observed on P2-P4 and P6 as follows:

P2 (Fig. 6B View Figure 6 ). Intercoxal sclerite with acute distal margins. Coxa without inner seta. Basis with bare, slender outer seta; setules on inner distal corner. Two-segmented Exp, Exp-1 with outer spine. Exp-2 with three outer spines, apical normal seta and blunt seta, inner blunt seta and two normal setae. Two-segmented Enp, Enp-1 without inner seta. Enp-2 with one spine and three pinnate setae (inner, apical and outer setae).

P3 (Fig. 6C View Figure 6 ). Intercoxal sclerite, coxa, basis, Exp similar to P2. with outer spine. Enp-1 without inner seta. Enp-2 with one transformed spine and two pinnate setae (apical and outer setae). Apical transformed spine with hook-like tip bent outwards, medial part slightly swollen, smooth.

P4 (Fig. 6D View Figure 6 ). Intercoxal sclerite with acute distal margins. Coxa without inner seta. Basis with slender outer seta. Two-segmented Exp. Exp-1 with outer spine. Exp-2 with three outer spines, two apical and two inner normal setae. Two-segmented Enp. Enp-1 without inner seta. Enp-2 with two apical pinnate setae.

P6 (Fig. 5B-D View Figure 5 ). Reduced to simple plate, represented by three subequal pinnate setae.

Differential diagnosis.

Bryocyclops jayabhumi sp. nov. can be assigned to the genus Bryocyclops s. str. as it exhibits the following characteristics: i) P5 completely fused to somite, with three elements inserted directly on the thoracic somite; ii) P1-P4 with two-segmented Exp and Enp, except female P4 with one-segmented Enp; iii) P1-P4 intercoxal sclerites with acute free distal margins; iv) P1-P4Exp-2 with spine and setal formula 3.3.3.3 and 5.5.5.4, respectively; and v) sexual dimorphisms on P3-P4, with transformed spine on male P3Enp-2. The new species, therefore, fits into Group VII sensu Watiroyram et al. (2015), because it has two elements on the P4Enp and P1 coxa without inner seta.

Group VII contains two species collected from Thailand - B. jayabhumi sp. nov. and B. maholarnensis Watiroyram, Brancelj & Sanoamuang, 2015. Both species are obviously different from other species due to their P4Enp, which terminates in two elements instead of five elements (when one-segmented) or four elements (when two-segmented). These species could, however, be differentiated from each other by the following characteristics: i) posterior margin of urosomites serrated (smooth in B. maholarnensis ); ii) anal operculum triangular with acute-tip (round in B. maholarnensis ); iii) inner setae on medial margin of P1-P4Enp-1 absent (present in B. maholarnensis ); iv) armature on female P2-P3 (each with three elements in the new species, versus four and two elements, respectively, in B. maholarnensis ); v) armature on female P4Enp (two apical elements in the new species versus one apical and one inner seta in B. maholarnensis ). The male P3Enp-2 of the new species has a well-developed, transformed spine similar to those in B. maholarnensis , but with a swollen medial portion.

The new species shows two remarkable characteristics on its swimming legs and in the urosomal serration in both sexes, which have never been seen in other examples of Bryocyclops s. str. The new species lacks inner distal setae on P1-P4Enp-1 and has a different serrated pattern on urosomites 1-4. The posterior margin on the somites of its congeners have normal serration, with lobes on free margin of hyaline fringe (for example, B. anninae (Menzel, 1926); B. asetus Watiroyram, 2018; B. maewaensis Watiroyram, Brancelj & Sanoamuang, 2012; B. muscicola (Menzel, 1926); B. muscicoloides Watiroyram, 2018; B. trangensis Watiroyram, 2018), versus the new species, which has sparsely indented and a completely smooth hyaline fringe in B. maholarnensis .

Ecology and distribution.

The new species has been found in only one locality, about 140 km away from its most similar species ( B. maholarnensis ). Bryocyclops jayabhumi sp. nov. is so far confined to this locality, while B. maholarnensis has a wide distribution range across Loei and Nong Bua Lam Phu Provinces. Although the salinity of water containing B. jayabhumi sp. nov. was not measured, it is evidently a freshwater species, as its locality is 573 m above sea level and approximately 450 km from the nearest sea. The sampling site, Prakai Phet Cave, is not connected to running water or other groundwater; it is only fed water from the stalactites and tree roots penetrating its ceiling (Fig. 1C View Figure 1 ). No other copepods were found during the study period.