Bryocyclops muscicoloides, Watiroyram, 2018

Watiroyram, Santi, 2018, Two new species of the genus Bryocyclops Kiefer, 1927 (Copepoda: Cyclopoida: Cyclopidae) from southern Thailand, Raffles Bulletin of Zoology 66, pp. 149-169 : 151-159

Bryocyclops muscicoloides , new species

( Figs. 2–7 )

Type locality. Khao Plu cave in Wat [=temple] Tham Khao Plu located in Chumko Subdistrict , Pathiu District , Chumphon Province, southern Thailand ( Fig. 1A, 1B ). The coordinates of the entrance are 10°43′49.06′N, 99°19′12.52′E; altitude 27 m a.s.l. The cave is about 50 m long and situated on a small hill, with a single pool filled exclusively with dripping water in the dark zone. The type locality was made by a mixture of stone and cement in order to collect the dripping water for observance. The water temperature during sampling was 24.0°C, pH 7.8, and conductivity was 310 μS cm−1 .

Material examined. Holotype: an adult female was dissected and mounted on a slide in glycerol and sealed with nail polish, NHMUK 2017.503 . Allotype: an adult male was dissected and mounted on a slide in glycerol and sealed with nail polish, NHMUK 2017.504 . Paratypes: three undissected females (one female with egg sacs) and males were preserved by 70% ethanol in a 1.5 mL microtube, NHMUK 2017.505 – 510 ; three undissected females and males were preserved by 70% ethanol in a 1.5 mL microtube, NPU 2017.002 . Additional materials: four undissected females and males were mounted on SEM Stub ( NPU 2017.002 S) .

All specimens were collected from Khao Plu cave by author on 25 November 2016.

Diagnosis. Adult female: anal operculum is ovate, and serrated. P1–P4 show acute projection on distal margins, without inner coxal seta, P1 has an inner basal spine. P1–P3 have two-segmented Enp and Exp, P4 has one-segmented Enp and two-segmented Exp. Setal and spine formula are present on swimming legs: Exp-2 P1–P4 as 5.5.5.4 and 3.3.3.3, respectively; Enp-2 P1–P3 as 3.3.5 and 1.1.1, respectively. Enp P4 has four setae and one spine, without spiniform process on the segment.

Adult male: P1, P2, Exp P3-P4 are the same as in females. Enp-2 P3 has three pinnate and one smooth seta. The transformed spine has a well-produced, outstretched part tapering distally and located slightly above the middle of the spine. P4 Enp is two-segmented, and Enp-1 has one inner pinnate seta and one spiniform process on the inner distal margin; Enp-2 has three pinnate setae and one spiniform spine, without a spiniform process.

Description. Female ( Figs. 2 , 3 ), body length: 550–625 μm (mean: 610 μm; n = 10), preserved specimens are colourless. Naupliar eye not discernible. Cephalosome wider than rest of body, with transverse scar indicating the fusion region of cephalosome and pediger 1 ( Figs. 2A , 3A, 3B ). Cephalosome, pedigers 2–5, genital double-somite, urosomites and anal somite (incl. anal operculum) covered with fine refractile points. Posterior dorsal margins of cephalosome and pedigers 2–4 with smooth hyaline membrane, and with a serrated transverse row of dorsal hyaline frills above its posterior margin; pediger 5 with small serrated hyaline frill. Genital double-somite and urosomite 2–3 with irregularly serrate hyaline membrane on entire posterior margins; with a transverse row of small grooves on dorso-lateral surface ( Figs. 2A , 3C, 3D ). Genital double-somite symmetrical, about 1.5 times wide as long; with a pair of dorsal sclerotised; single copulatory pore situated ventrally near middle of segment. Anal somite ( Figs. 2 A–C, 3C) with strong spinules along entire posterior margin.

Anal operculum ( Figs. 2C , 3C ) ovate, coarsely serrated along its free margin, reaching beyond the middle of caudal ramus length, with a pair of small sensillum above the base.

Caudal rami ( Figs. 2A , 3C ) symmetrical sub-rectangular, about 1.3 times long as wide. Dorsal keel long, orientated nearly the entire caudal ramus length. Seta I absent, seta II-V pinnate. Lateral seta (II) shorter than the caudal ramus, inserted at about mid-length of caudal ramus. Outermost terminal seta (III) longer than dorsal seta, about 1.5 times as long as caudal ramus with strong spinules near its insertion on lateral and ventral views. Seta IV and V with fracture plane: outer terminal seta (IV) and inner terminal seta (V) about 4.0 and 6.0 times as long as caudal ramus, respectively. Innermost terminal seta (VI) thin and bare, shorter than 1/2 of caudal ramus. Dorsal seta (VII) articulated and bare, about 1.2 times as long as caudal ramus, inserted on distal end of keel with tiny spinules at insertion.

Rostrum ( Fig. 4A ) fused to cephalosome, free margin round, unornamented.

Antennule ( Figs. 3A , 4B ) short, reaching about 1/2 of cephalosome, 11-segmented. Setal formula on each segment as follows (A = aesthetasc): 6.2.5.2.0.2.3.1+A.2.2.7+A. All setae smooth.

Antenna ( Fig. 4C ) four-segmented, comprising coxobasis and three-segmented Enp. Coxobasis with bare seta on distal inner corner. Enp-1 with smooth seta on distal inner margin plus row of spinules on outer margin. Enp-2 with five smooth setae: three lateral and two apical setae. Enp-3 with seven smooth setae on distal end: one inner, four apical and two outer setae.

Mandible ( Fig. 4D ) short and robust, with five strongly chitinised teeth on gnathobase plus a smooth seta on innermost margin. Mandibular palp reduced, with one bare seta.

Maxillule ( Fig. 4E ) with praecoxa, coxobasis and onesegmented Enp. Praecoxal arthrite with four strong apical claws fused to arthrite base, with one strong spine, four short and smooth setae and one spinulate seta on frontal side. Coxobasis with one spiniform and two smooth setae. Exp reduced into one smooth seta. Enp with three smooth setae.

Maxilla ( Fig. 4F ) with praecoxa, coxa, basis, and twosegmented Enp. Praecoxal endite with two apical setae. Coxa with one seta at near middle of inner margin and two setae on distal endite. Basis with two claw-like expansions plus one seta at insertion. Enp-1 with one seta and Enp-2 with three thin setae and one robust seta.

Maxilliped ( Fig. 4G ) syncoxa and basis with two and one spiniform setae, respectively, each with a row of strong spinules on inner margin. Two-segmented Enp, Enp-1 with spiniform seta. Enp-2 reduced, with two smooth setae.

Armament of legs 1–4 as follows (legend: outer-inner seta/ spine; outer-apical-inner; Arabic numerals indicate setae; Roman numerals indicate spines):

P1 ( Fig. 5A ) intercoxal plate with acute projections on distal margin. Coxa without seta on inner corner. Basis with bare, slender outer seta and robust, stout inner spine with a cluster of spinules at spine insertion. Two-segmented Exp and Enp. Exp-1 smaller than Exp-2, with outer spiniform spine. Exp- 2 twice as long as wide with three outer spiniform spines, two apical pinnate setae and three inner pinnate setae. Enp-1 with one inner pinnate seta with spiniform process at distal outer corner. Enp-2 with three subequal pinnate setae and one spiniform spine; one outer seta located between two spiniform processes, one apical spine and one apical seta, and one inner seta.

P2 ( Fig. 5B ) intercoxal plate, coxa, basis, and Exp similar to P1, but basis without spine on inner margin. Two-segmented Enp, and Enp-1 slightly smaller than Enp-2. Enp-1 with one inner pinnate seta and spiniform process at distal outer corner. Enp-2 with four subequal elements: one apical spiniform spine and three pinnate setae (outer seta located between two spiniform processes, apical seta and inner seta).

P3 ( Fig. 5C ) intercoxal plate, coxa, basis, Exp, and Enp-1 similar to P2. Enp-2 with one apical spine and five pinnate setae: shortest outer seta located between two spiniform processes, three inner setae about as long as spine and longest apical seta.

P4 ( Fig. 5D ) intercoxal plate with acute projections on distal margin. Coxa without inner seta. Basis with slender outer seta. Two-segmented Exp, Exp-1 with outer spiniform spine and Exp-2 with three outer spiniform spines, two apical pinnate setae and two inner pinnate setae. One-segmented Enp, with one spine and four pinnate setae; outer seta about as long as two inner setae, apical one longest, about 3.0 times as long as spine.

P5 ( Figs. 2C, 2D , 3E ) completely fused to somite, with three pinnate setae: outermost seta longest, inserted on small prominence; middle and innermost seta directly inserted on somite, former seta shorter than latter one.

P6 ( Figs. 2C , 3D ) reduced to simple plate on genital doublesomite laterodorsally, with two minute spinules and short pinnate seta.

Adult females each have a pair of egg sacs, each with three large eggs.

Male ( Figs. 3 F–I, 6) smaller than female. Body length, excluding caudal setae, 460–550 μm (mean: 530 μm; n = 10). Body shape similar to female, except in genital segment and urosomal segmentation (i.e. the males have one more urosomite). Antenna and mouthparts (not figured), caudal rami ( Fig. 6 ), P1 ( Fig. 7A ), P2 ( Fig. 7B ), P3–P4 exopods ( Figs. 7C, 7D ) and P5 ( Fig. 6D ) similar to those in female.

Anal operculum ( Figs. 3G , 6B, 6D ) slightly shorter than in female, about mid-length of caudal ramus.

Antennule ( Fig. 4H ) 15-segmented, geniculate. Setal formula as follows (A = aesthetasc, S = spine): 8+2A.3.2.2+A.1.2.2.1+A.2.2.S.1+A.S.1.8+A. All setae smooth.

P3 ( Fig. 7C ) two-segmented Enp, proximal segment smaller than distal one. Enp-1 with inner pinnate seta and spiniform process on distal outer margin. Enp-2 with small outer pinnate seta between two spiniform processes, apical transformed spine and apical bare seta and two inner pinnate setae. Transformed spine with outstretched part tapering distally and well-produced, located slightly above the middle of spine; with several strong spinules on its outstretched part.

P4 ( Fig. 7D ) two-segmented Enp. Enp-1 with inner pinnate seta and spiniform process on inner distal margin. Enp-2 with one outer pinnate seta, one apical spine and pinnate seta, and one inner pinnate seta.

P6 ( Figs. 3I , 6C ) reduced to simple plate, with two equal pinnate setae and one longer pinnate seta.

Variability. Not observed.

Etymology. The specific name muscicoloides , formed with the Latin suffix “- oides ” for resembling, refers to the similarity of the new species with B. muscicola . The species epitheton is a masculine singular adjective.

Remarks. Bryocyclops muscicoloides , new species, fits to the generic characters as the P5 is completely fused to the fifth thoracic somite, with three setae, P2–4 have no inner coxal seta, the intercoxal plate of P4 has acute protuberances on the distal margin, and the male P3 Enp-2 has a transformed spine. The new species is similar to the members of Group II sensu Lindberg (1954) (except that P1 coxa has no inner seta in B. muscicoloides , new species) in the following characters: (1) sexual dimorphism occurs on P3 Enp-2 and P4 Enp-2, (2) P1 basis has an inner spine, (3) intercoxal plates of P1–P4 have acute protuberances on the distal margin, (4) the setal and spine formulae of P1–P4 Exp-2 are 5.5.5.4. and 3.3.3.3, respectively and (5) the P4 of female has two-segmented Exp and one-segmented Enp, and there are two-segmented Exp and Enp in the male ( Lindberg, 1954; Watiroyram et al., 2015a).

Currently, Group II consists of five species: B. bogoriensis ( Menzel, 1926), B. muscicola ( Menzel, 1926) , B. fidjiensis Lindberg, 1953 , B. caroli Bjornberg, 1985 , and B. campaneri Rocha & Bjornberg, 1987 ( Reid, 1999) . The new species is most similar to B. muscicola from Indonesia ( Menzel, 1926; Bjornberg, 1985; Rocha & Bjornberg, 1987; Watiroyram et al., 2015a). Apart from the group characteristics as previously mentioned, they share some affinities in the posterior margin of the urosome and anal operculum serrated, the female Enp P4 has four setae and one spine; the setal formulae on Enp-2 P1 and P 3 in female have four and six elements, respectively, and Enp-2 P1 of males has four elements. Bryocyclops muscicoloides , new species, differs markedly from B. muscicola in the following characteristics: in both sexes, P1 has no inner coxal seta (present in B. muscicola ) and Exp-2 P2–P3 have normal setae (each with two blunt setae in B. muscicola ); in males, the transformed spine on Enp-2 P3 shows the outstretched part gradually tapering to the tip, which is located above the middle of its length (semi-circular and located at about halfway along the length in B. muscicola ); in female, Enp P4 has no spiniform process on the outer margin (present in B. muscicola ). Regarding species descriptions by Reid (1999), the other differences between the species are (a) the prosome and urosome have refractile points including anal operculum (only prosome in female and included urosomite 2 in male with respective characters in B. muscicola ), (b) caudal ramus has spinules at the insertion of dorsal seta, and (c) caudal ramus of male has dorsal keel (both absent in B. muscicola ).

Bryocyclops muscicoloides , new species, differs from B. bogoriensis in that the female of the new species has three setae on P2 Enp-2 but there are five setae in B. bogoriensis; P4 Enp has no spiniform process on the outer margin of B. muscicoloides , new species, whereas it is present in B. bogoriensis; and apical seta are longest in the new species but are almost as long as the distal inner seta in B. bogoriensis. The transformed spine on the male P3 Enp-2 has an outstretched part gradually tapering to the distal end, but it is rounded in B. bogoriensis.

The new species has a serrated and rounded anal operculum, but this is triangular and smooth in B. fidjiensis . Bryocyclops muscicoloides , new species’ P4 Exp and Enp are two- and one-segmented in female and two-segmented in male, but are one- and two-segmented in both sexes of B. fidjiensis . There are three spines on the distal exopod of P 4 in the new species but four spines on the same segment in B. fidjiensis . Bryocyclops muscicoloides , new species, can be distinguished from B. caroli by P1 of the new species: it has no coxal inner seta, which is present in the later species. The anal operculum is regularly serrated in the new species compared to those in B. caroli . The shape of the female P4 Enp diferentiates the new species from B. caroli by lack of a spiniform process on the outer margin and the transformed spine of male P3 Enp-2 has well-developed outstretched part and acute tip in the new species, while those spine in B. caroli has lessdeveloped outstretched part and blunt tip.

Bryocyclops muscicoloides , new species, is different from B. campaneri in that the new species has no inner coxal seta on P1, which is present in B. campaneri ; the P1 Exp-2 of the new species has five setae compared to four for B. campaneri ; the female P4 Enp of the new species has no any spiniform process and the apical seta is typically longer than the apical spine while those segment in B. campaneri has outer spiniform process and apical seta is slightly longer than the spine; and the transformed spine on the male P3 Enp-2 of the new species has an outstretched part tapering to its tip compared to a semi-circular shape for B. campaneri .

The new species is easily distinguished from Group VII, proposed by a single species ( B. maholarnensis Watiroyram, Brancelj & Sanoamuang, 2015 ) from Thailand, in that the distal Enp of P 4 in B. muscicoloides , new species, has four setae and one spine, as in other members of Group II; however, only two setae are present in B. maholarnensis and P3 Enp-2 of male in B. muscicoloides , new species, have remarkable transformed spine which is normally found in Group II and other Bryocyclops species but is absent in B. maholarnensis . The new species also differs from B. maewaensis Watiroyram, Brancelj & Sanoamuang, 2012 , found in Thailand, by the new species lacking inner coxal seta on P1, P2 Enp-2 of the new species having three setae (compared to four setae in B. maewaensis ), the female P4 Enp being one-segmented and having four setae and one spine in the new species (compared to B. maewaensis being two-segmented and having three setae and one spine on the distal Enp), the male P3 Enp-2 of the new species having a longer distance between its tip and the outstretched part in the new species being smaller and differently shaped to B. maewaensis .

Figures

Fig. 2. Bryocyclops muscicoloides, new species, female. A, habitus, dorsal view; B, genital double-somite and urosome, ventral view; C, pediger 5, genital double-somite and urosome, lateral view; D, P5. Scale bar = 100 µm.

Fig. 3. Bryocyclops muscicoloides, new species, female (A–E) and male (F–I). A, habitus, dorsal view; B, prosome, dorsal view; C, urosome, dorsal view; D, genital double-somite and urosome 2, dorsal view; E, pediger 5 and genital double-somite, ventral view; F, habitus, dorsal view; G, genital somite and urosome, dorsal view; H, pediger 5, genital somite and urosome, ventral view; I, genital somite and urosome 2, ventral view.

Fig. 4. Bryocyclops muscicoloides, new species, female (A–G) and male (H). A, rostrum; B, antennule; C, antenna; D, mandible; E, maxillule; F, maxilla; G, maxilliped; H, antennule. Scale bars = 100 µm.

Fig. 5. Bryocyclops muscicoloides, new species, female. A, P1; B, P2; C, P3; D, P4. Scale bar = 100 μm.

Fig. 6. Bryocyclops muscicoloides, new species, male. A, habitus, dorsal view; B, genital somite and urosome, dorsal view; C, genital somite and urosome, ventral view; D, pediger 5, genital somite and urosome, lateral view. Scale bar = 100 µm.

Fig. 7. Bryocyclops muscicoloides, new species, male. A, P1; B, P2; C, P3; D, P4. Scale bar = 100 μm.

Fig. 1. Sampling localities and habitats for new species in southern Thailand (A–C). A, sampling localities, black circle (l) = Khao Plu cave from Chumphon Province for B. muscicoloides, new species, and black square (N) = Khao Pina cave from Trang Province for B. trangensis, new species; B and C, habitat for B. muscicoloides, new species and B. trangensis, new species, respectively.