Cletocamptus thailandensis, Boonyanusith & Wongkamhaeng, 2023

Boonyanusith, Chaichat & Wongkamhaeng, Koraon, 2023, A new species of Cletocamptus Schmankevitsch, 1875 (Copepoda, Harpacticoida, Canthocamptidae) from Rayong Province, Eastern Thailand, ZooKeys 1151, pp. 1-29 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.1151.96715
publication LSID	lsid:zoobank.org:pub:4A79044C-AE17-47D1-8661-BFD317A911E8
persistent identifier	https://treatment.plazi.org/id/31517B17-C7FE-484F-B96B-69F54CBA879E
taxon LSID	lsid:zoobank.org:act:31517B17-C7FE-484F-B96B-69F54CBA879E
treatment provided by	ZooKeys by Pensoft
scientific name	Cletocamptus thailandensis
status	sp. nov.

Treatment

Cletocamptus thailandensis sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 (female), 8-11 (male) View Figure 7

Material examined.

Holotype: Thailand • 1 ♀ (adult), 670 μm long; Rayong Province; 12°45'52.96"N, 101°47'55.16"E, 24 m a.s.l.; 19 Jul. 2022; C. Boonyanusith leg.; hand net; completely dissected and mounted on a slide in glycerol and sealed with nail polish; PSUZC-PK2007-01 GoogleMaps . Allotype: Thailand • 1 ♂ (adult), 483 μm long; 22 May 2022; other collection data as for holotype; PSUZC-PK2007-02 GoogleMaps . Paratypes: Thailand • 1 ♀ (adult) and 1 ♂ (adult); same data as for holotype; PSUZC-PK2007-03 and PSUZC-PK2007-04, respectively GoogleMaps .

Additional material.

Thailand • 1 ♂ (adult) , 1 ♀ (adult); same data as for holotype; preserved in 70% ethanol; retained in collection of the first author (CB) .

Diagnosis.

Female: Body fusiform. All abdominal somites with row of moderately long spinules on lateral surface. Anal operculum with two rows of spinules. Caudal ramus ca. 1.7 × as long as wide, with three rows of spinules on inner margin. Antennary exopod with three setae. Mandibular palp with two setae on free segment and one seta arising nearby. Praecoxal arthrite of maxillule with moderately strong, lateral seta. P1Endp-1 reaching distal fourth of Exp-2, with inner seta. Armature complement of Exp-3 and Endp-2, from P1-P4: 4.5.6.5 and 3.3.5.2, respectively. Inner apical seta on P3Endp-3 reaching mid length of outer one. P5 with large notch between baseoendopodal lobe and exopodal one, with six marginal setae on the former and five setae on the latter. P6 reduced to small protuberance with one apical seta on peduncle. Male: Left and right legs of P5 fused at base, with three marginal setae on baseoendopodal lobe and four setae on exopodal one. P6 reduced to simple unarmed plate.

Description of adult female.

Total body length, excluding caudal setae, ranging from 630 µm to 680 µm (mean = 655; n = 4). Habitus tapering posteriorly, with maximum width at posterior fourth of cephalothorax (Fig. 2A, B View Figure 2 ). Rostrum (Fig. 3A View Figure 3 ) well developed, distinct, with broad base and rounded tip; dorsal surface with pair of sensilla; ventral surface with arch row of long spinules subdistally. Prosome ca. 1.1 × as long as urosome (including caudal rami), comprising cephalothorax and three free pedigerous somites (P2-P4-bearing somites). Cephalothorax ca. 1.1 × as long as wide and ca. 0.5 × as long as length of prosome, furnished with numerous pits, with numerous sensilla and with long spinules along margin dorsally and laterally (Fig. 2A, B View Figure 2 ). Dorsal and lateral surfaces of free pedigerous somites with numerous transverse rows of spinules, with stronger spinules and subdistal sensilla near posterior margin; posterior margin with long spinules.

Urosome (Figs 2A, B View Figure 2 , 3B View Figure 3 ) comprising fifth pedigerous somite (P5-bearing somite), genital double-somite, and three free abdominal somites; lateral surface of all abdominal somites with row of moderately long spinules (Fig. 2B View Figure 2 ). Fifth pedigerous somite (first urosomite) with numerous transverse rows of spinules, with spinules and subdistal sensilla near posterior margin; posterior margin with larger spinules dorsally and long spinules laterally. Second and third urosomites fused ventrally forming genital double-somite, ca. 0.6 × as wide as long, with subchitinous rib representing former division of genital somite and first abdominal one and dividing genital double-somite into anterior and posterior portions; dorsal and lateral surfaces of both portions with numerous transverse rows of spinules, with spinules along margin of subchitinous rib and with hair-like spinules near posterior margin of posterior portion; ventral surface with row of spinules medially, with ventral pore beside medial row of spinules (Fig. 3B View Figure 3 ); posterior margin of double-somite with moderately long spinules. Genital field (Fig. 3B View Figure 3 ) with ovipore medially at the middle of genital double-somite. Second and third abdominal somites (fourth and fifth urosomites) with numerous transverse rows of spinules, with hair-like spinules dorsally and sensilla near posterior margin and with moderately longer spinules along posterior margin.

Anal somite (Figs 2C View Figure 2 , 3B View Figure 3 ) with pair of dorsal sensilla in front of anal operculum, with numerous paired rows of moderately long spinules on dorsal, lateral, and ventral surfaces as shown, accompanied with two pairs of cuticular pores ventrally. Anal operculum slightly convex, with two rows of spinules.

Caudal rami (Figs 2C, D View Figure 2 , 3B View Figure 3 ) slightly divergent, each ca. 1.7 × as long as wide, with seven setae; ornamentation comprised of three transverse rows of spinules on inner margin, row of spinules dorsally near distal margin, oblique row of strong spinules near insertion of seta IV, row of long spinules ventrally near insertion of seta IV and seta V, and cuticular pore near base of seta II. Seta I inserted ventro-laterally near insertion of rami; seta II and seta III inserted closely to each another at anterior third of ramus; seta IV and V, ca. 0.22 and ca. 0.58 of body length, respectively, with fracture plane in seta V; seta VI slender, inserted on inner distal corner; seta VII biarticulate, inserted at mid length of ramus medially.

Antennule (Fig. 4A View Figure 4 ) six-segmented. First segment with two rows of spinules medially. Fourth segment with aesthetasc on peduncle; aesthetasc slightly elongated,> 45% of length of aesthetasc surpassing the tip of antennule. Ultimate segment ca. 4.5 × as long as wide, with aesthetasc. Aesthetascs fused to seta at base. Armature formula: 1-[1], 2-[9], 3-[6], 4-[1 + (1 + ae)], 5-[1], 6-[9 + (1 + ae)].

Antenna (Fig. 4B View Figure 4 ) biramous, comprising coxa, allobasis, one-segmented Exp, and one-segmented Endp. Coxa short, with arch row of spinules on outer margin. Allobasis with two abexopodal setae. Exp cylindrical, with few spinules subdistally and armed with one lateral seta and two apical setae (one of the apical setae short and slim). Endp club-shaped, with one short seta and two spines medially on inner margin, and five apical setae of which two innermost ones spiniform, two median ones geniculate, outermost one spiniform with two strong spinules half-length of element and bipinnate along distal half; spinule ornamentation comprised of proximal and distal rows of strong spinules, and row of spinules distally.

Mandible (Fig. 4C View Figure 4 ) comprising sclerotized coxal gnathobase and mandibular palp. Coxal gnathobase with two arch rows of spinules as shown; cutting edge with five bicuspidate and multicuspidate teeth, with one pyriform element and pinnate, ventral seta. Mandibular palp one-segmented, with two apical setae, accompanied with one short seta inserted nearby.

Maxillule (Fig. 5A, B View Figure 5 ) comprising robust praecoxa, coxa, and basal complex, the latter composed of basis with Endp and Exp completely incorporated to the latter. Praecoxal arthrite with row of spinules on caudal surface and on lateral margin, armed with surface seta on frontal surface and nine distal elements: seven of which strong, curved spines, subdistal seta slim and pinnate, lateral seta moderately strong and pinnate. Coxa with cylindrical endite bearing two smooth apical setae, and with few spinules. Basis seemingly with three apical setae of which middle robust and pinnate. Endp and Exp completely incorporated to basis, seemingly represented by three setae each.

Maxilla (Fig. 5C View Figure 5 ) composed of syncoxa and allobasis, and Endp fully incorporated to the latter. Syncoxa with two endites, each endite armed with three elements apically, one of which slender. Allobasis drawn out into claw, with one seta basally on caudal surface. Endp completely incorporated to allobasis, represented by three smooth setae.

Maxilliped (Fig. 5D View Figure 5 ) subchelate, three-segmented, comprising syncoxa, basis, and Endp. Syncoxa with curved row of spinules on caudal surface, with one pinnate seta on inner distal corner. Basis with longitudinal row of spinules on frontal and caudal surfaces, and two transverse rows of spinules on outer margin. Endp drawn out into strong claw and armed with one minute seta near base.

P1-P4 comprised of intercoxal sclerite, praecoxa, coxa, basis, and two rami.

P1 (Fig. 6A View Figure 6 ). Intercoxal sclerite as shown, with two rows of minute spinules on each side. Praecoxa triangular, with spinules along distal margin and on outer distal corner. Coxa rectangular, with one row of spinules medially, with two oblique rows of spinules and with strong spinules on outer distal corner. Basis with integumental pore on frontal surface, with oblique row of spinules and three rows of stronger spinules of which innermost at base of inner spine, median between insertion of rami, outermost at base of Exp; armament comprising outer and inner spines, inner spine reaching distal third of Endp-1. Exp three-segmented, all segments with spinule row on outer margin and outer distal corner; Exp-1 with outer spine; Exp-2 with outer spine and inner seta; Exp-3 with four elements: innermost and inner apical ones slender. Endp two-segmented, reaching tip of Exp; Endp-1 reaching distal fourth of Exp-2, with inner seta; Endp-2 slightly longer than Endp-1, with three elements of which outer apical spiniform.

P2 (Fig. 6B View Figure 6 ). Intercoxal sclerite as shown, bare. Praecoxa with spinules along distal margin. Coxa with row of spinules medially and strong spinules along outer margin. Basis as that of P1 but lacking inner spine and inner distal corner; spinule row between rami with smaller spinules relative to those of P1; with medial pore proximally. Exp three-segmented, with spinule ornamentation as that of P1, additionally with row of spinule on inner distal corner of Exp-1 and Exp-2; Exp-1 with outer spine; Exp-2 with outer spine and inner seta; Exp-3 with five elements (two outer spines, two distal and one inner seta). Endp two-segmented, reaching middle of Exp-2; Endp-1 small, wider than long, with inner spinules; Endp-2 ca. 3.0 × as long as wide, with spinule ornamentation on outer and inner margins, armed with three elements of which outer spiniform and slender.

P3 (Fig. 7A View Figure 7 ). Intercoxal sclerite, praecoxa, coxa, and basis as those of P2. Exp three-segmented; Exp-1 and Exp-2 as those of P2; Exp-3 with six elements (two outer spines, two distal and two inner seta). Endp two-segmented; Endp-1 small, wider than long, with inner spinules; Endp-2 ca. 3.5 × as long as wide, armed with five elements of which outer spiniform and slender, inner apical one reaching middle of outer apical one, two inner ones subequal in length.

P4 (Fig. 7B View Figure 7 ). Intercoxal sclerite, praecoxa, coxa, and basis as those of P2. Exp three-segmented; Exp-1 and Exp-2 as those of P2; Exp-3 with five elements (two outer spines, two distal and one inner seta). Endp two-segmented; Endp-1 small, wider than long, with inner spinules; Endp-2 ca. 2.5 × as long as wide, armed with two apical setae of which outer ca. 2.5 × as long as inner one.

Armature formula of P1-P4 as in Table 1 View Table 1 .

P5 (Fig. 3C View Figure 3 ). Baseoendopod and Exp completely fused basally, with large notch between them; left and right legs completely separated. Baseoendopodal lobe ca. 1.5 × as long as length of exopodal one, with one outer, two apical and three inner setae. Exopodal lobe with five elements accompanied with slender, outer seta of basis; relative length and characteristics of setae on both baseoendopodal and exopodal lobes as shown.

P6 (Fig. 3B View Figure 3 ) reduced to minute prominence, forming simple plate near anterior margin of genital double-somite, with row of minute spinules and one short seta on each side.

Description of adult male.

Body smaller than in female. Total body length, excluding caudal setae, ranging from 483 µm to 505 µm (mean = 493; n = 4). Prosome ca. 1.1 × as long as urosome (Fig. 8A, B View Figure 8 ). Cephalothorax slightly longer than wide, ca. 0.6 × as long as length of prosome. Rostrum (Fig. 8C View Figure 8 ) well developed, distinct, narrower than that of female, with rounded tip; dorsal surface with pair of sensilla, ventral surface with arch row of long spinules subdistally. Ornamentation of cephalothorax and free prosomite as those of female.

Urosome (Figs 8A, B View Figure 8 , 9A View Figure 9 ) six-segmented, comprising fifth pedigerous somite, genital somite and four free abdominal somites; lateral surface of all abdominal somites with row of moderately long spinules. Dorsal and lateral surfaces of fifth pedigerous somite with numerous transverse rows of spinules, with spinules and subdistal sensilla near posterior margin; posterior margin with long spinules. Genital somite with numerous transverse rows of spinules, with spinules and subdistal sensilla near posterior margin; posterior margin with larger spinules dorsally and long spinules laterally. Genital opening positioned mid-ventrally near anterior margin of genital somite (Fig. 9A View Figure 9 ). First to third abdominal somites as those of female, but lacking hair-like spinules near posterior margin; spinule ornamentation lesser developed in comparison to those of female, each somite with three medial rows of spinules ventrally. Anal somite (Figs 8D View Figure 8 , 9A View Figure 9 ) as that of female.

Caudal rami (Figs 8D View Figure 8 , 9A View Figure 9 ) as that of female, but inner margin with only two transverse rows of spinules. Seta IV and V, ca. 0.26 × and ca. 0.59 × body length, respectively. Seta VI relatively shorter than that of female.

Antennule (Fig. 9B, C View Figure 9 ) subchirocerate, six-segmented. First segment with two rows of spinules medially. Fourth segment bulbous, with aesthetasc on peduncle. Ultimate segment with two claw-shaped extensions subdistally. Aesthetascs to seta at base. Armature formula: 1-[1], 2-[9], 3-[6], 4-[7 + (1 + ae)], 5-[1], 6-[6 + (1+ae)].

Antenna, mandible, maxillule, maxilla, and maxilliped as those of female.

P1 (Fig. 10A View Figure 10 ) as that of female, except for the projection on inner distal corner of basis.

P2 (Fig. 10B View Figure 10 ) as that of female, except for sexual dimorphic (slightly shorter and stronger) inner seta on Endp-2.

P3 (Fig. 11A View Figure 11 ) as that of female in intercoxal sclerite, praecoxa, coxa, basis, and Exp. Endp three-segmented; Endp-1 short, wider than long; Endp-2 drawn out into apophysis, with row of spinules on outer margin and on frontal surface near base of Endp-3, apophysis surpassing tip of Endp-3; Endp-3 with two apical setae.

P4 (Fig. 11B View Figure 11 ) as that of female.

Left and right legs of P5 (Fig. 10C View Figure 10 ) fused medially at base, with medial notch indicating former separation between them; baseoendopod and Exp fused basally, with large notch indicating division between baseoendopodal and exopodal lobes. Baseoendopodal lobe with three pinnate spiniform setae apically, setae subequal in length; exopodal lobe with spinules at base of outermost apical seta, armed with four elements of which three apical ones pinnate and spiniform, outermost smooth and slender. Smooth soft seta on outer margin of basis, accompanied with row of spinules at base.

P6 (Fig. 9A View Figure 9 ) reduced to simple plate, without armature and ornamentation. Posterior margin smooth.

Etymology.

The species name is a noun proposed to reflect the name of the country, ‘Thailand’, where the new species was encountered. It is in the nominative singular, gender masculine.

Type locality.

The new species was collected from a water body at the base of an isolated limestone mountain (Fig. 1A, B View Figure 1 ) that is the distalmost part of the Cha Moon-Cha Mao Mountain Range in the Gong Din Subdistrict, Klaeng District, Rayong Province, Eastern Thailand. The coordinates of the type locality are 12°45'52.96"N, 101°47'55.16"E. The mountain is located beside a monastery known in Thai as 'Wat Tham Rakang Thong’ (Tham Rakang Thong Monastery). The mountain and the water body are surrounded by a manmade concrete road (Fig. 1C View Figure 1 ), which separates the mountain and the monastery from the mangrove forests. The water is ca. 20 cm in depth and transparent with a brown color. The bottom of the water body is covered by leaf litter and filamentous algae. On the first sampling occasion, the temperature was 27.4 °C, the pH was 5.48, and the dissolved oxygen level was 5.5 mg L-1. The water electroconductivity and total dissolved solids were higher than 3,999 µS cm-1 and 2,000 ppm, respectively. On the second occasion, the temperature was 30.0 °C, the pH was 6.53, the electroconductivity was 2,158 µS cm-1, and the total dissolved solids were 1,080 ppm. The new species was collected with other zooplankton species, such as Phyllognathopus paludosus (Mrazek, 1893), Mesocyclops ogunnus Onabamiro, 1957 (the most dominant), Apocyclops borneoensis Lindberg, 1954, Tropocyclops sp., Nitokra sp., the rotifer of the genus Testudinella Bory de St. Vincent, 1822, the cladoceran of the genus Leberis Smirnov, 1989, and ostracods. Aquatic insects belonging to the order Ephemeroptera and the family Chironomidae were also observed.