Paracyclopina orientalis Lindberg 1941

Paracyclopina orientalis (Lindberg, 1941)

(Figs. 2–8)

Synonymy. Cyclopetta orientalis Lindberg, 1941 (female): 87–88, Fig. 1 a–h; Lindberg, 1946 (male) (no Fig.): 84-85; Dussart & Defaye, 2001: 114, 230, Fig. L84; Dussart & Defaye, 2006: 9.

Paracyclopina orientalis ( Lindberg, 1941): Boxshall & Jaume, 2012: 44.

Material examined. Female (MNHN-IU-2013-11848) and 1 male (MNHN-IU-2013-11849), dissected on 3 slides each; 1 female and 1 male (MNHN-IU-2013-11850), whole-mounted on 1 slide each; 1 female, 1 male and 1 female juvenile (fifth copepodid stage), dissected on 3 slides each, in senior author’s personal collection; River Godavari at Angara village (water temperature 23°C; pH 7.5; 16o45′19.3″N, 81o54′07.6″E; elevation 34 m) in East Godavari District, Andhra Pradesh, South India. 24 January 2008; Coll. V. R. Totakura.

Redescription of adult female. Total body length, measured from base of rostrum to posterior margin of caudal rami (excluding caudal setae), 398–462 Μm (n = 3). Naupliar eye absent. Body (Fig. 2 a) cyclopiform, robust, somewhat compressed dorso-ventrally, and prosome-urosome boundary well demarcated at podoplean position. Prosome/urosome ratio 1.2 and greatest body width at posterior end of cephalothorax. Body length/width ratio 2.7. Prosome comprising cephalothorax and 4 pedigerous somites. Cephalothorax 2.2 times as wide as genital double-somite and not produced postero-laterally. Rostral projection (Fig. 4 a) broadly triangular and furnished with 2 ventral sensilla. Free pedigerous somites with straight postero-lateral corners, but fourth pedigerous somite with rounded lateral margins. Pseudosomite between prosome and urosome short. Fifth pedigerous somite slightly wider than genital double-somite and with oblique lateral margins (Fig. 2 a). Cephalothorax (Fig. 2 a) 0.7 times as long as its greatest width, about 25% of total body length; ornamented with several small sensilla, as illustrated; hyaline fringe moderately developed dorsally and smooth. First pedigerous somite free but partly concealed by posterior extension of dorsal cephalic shield. Free pedigerous somites 1–4 with narrow and smooth hyaline fringe each mid-dorsally (not on later margins) and ornamented with sensilla on dorsal surface, as illustrated. Hyaline fringe on fifth pedigerous somite smooth dorsally and ventrally and ornamented with 4 sensilla. Genital doublesomite subcylindrical in dorsal (Figs. 2 a, 3a) and ventral views (Figs. 2 b, 3b), proximally dilated, 1.2 times as long as wide and with a small indentation on either side at about midlength (details of genital apparatus could not be depicted because of unexpected difficulties with slide preparation). Hyaline fringe of genital double-somite and next 2 urosomites with finely serrulate margin both dorsally and ventrally (Fig. 3 a, b). Anal somite (Figs. 2 a, 3a, b) ornamented with row of dorsal and ventral spinules on distal margin, about as long as wide. Anal operculum (Fig. 2 a) moderately developed, close to anterior margin of anal somite, smooth, 53% of somite’s width, ornamented with 2 moderately long sensilla at base of anal operculum. Anal sinus widely open, unornamented.

Caudal rami (Figs. 2 a, 3a, b) parallel and close to each other and about as long as anal somite; each ramus 2.6 times as long as maximum width, ornamented with a ventral row of spinules on distal margin (Fig. 3 b) and armed with 6 setae; dorsal seta 0.4 times as long as principal outer apical seta, inserted at distal fifth of ramus length and uniarticulate at base; lateral seta slender, moderately strong, arising from about midlength of outer margin of ramus and about as long as ramus; outermost apical seta about as long as ramus, slightly shorter than innermost seta and inserted on small projection. Principal apical setae with breaking planes. Inner seta 1.6 times as long as outer seta, and 5.5 times as long as caudal ramus. Innermost apical seta slightly longer than caudal rami. All caudal setae plumose.

Antennule (Fig. 4 b): 17-segmented, extending up to 4/5 of cephalothorax, ornamented with row of spinules proximally on first segment. Setal formula: 3.5.9.2.2.4+aes.2.1.0.1.1.2.1+aes.2.1.3.7+aes. Length ratios of antennular segments along medial axis 1.0: 1.0: 1.4: 0.2: 0.2: 0.9: 0.9: 0.4: 0.6: 0.6: 0.6: 0.6: 0.5: 0.7: 0.5: 0.6: 0.9. Probable segmental homology: segment 1 (I–II) double, segment 2 (III–V) compound, segment 3 (VI–IX) compound, segment 4 (X) free, segment 5 (XI) free, segment 6 (XII–XIV) compound, segment 7 (XV–XVI) compound, segments 8 (XVII) –16 (XXV) all free, and apical segment 17 (XXVI–XXVII) compound.

Antenna (Fig. 4 d): 4-segmented, consisting of coxobasis and 3-segmented endopod. Setal formula of endopod: 1.5.7. Coxobasis 1.8 times as long as wide, armed with 1 short, smooth seta and 1 elongate, bipinnate seta at outer distal corner (perhaps representing exopod), the latter seta 3.1 times as long as the former, and 1 plumose seta at inner distal corner, and ornamented with 1 row of spinules on proximo-ventral surface, 2 rows of spinules on outer margin. First endopodal segment 1.9 times as long as wide, armed with 1 plumose seta at about mid-inner margin, and unornamented. Second endopodal segment shortest, 1.5 times as long as maximum width, armed with 5 unequal setae, as illustrated, and ornamented with 1 row of spinules along outer margin. Third endopodal segment 2.2 times as long as wide, armed with 7 unequal setae and ornamented with 2 rows of spinules on outer margin.

Labrum (Fig. 4 e): subtriangular, with smooth free margin; ornamentation not discernible on ventral surface.

Mandible (Fig. 5 a): coxa 2.1 times as long as wide, with well developed gnathobase having 1 large innermost tooth (on dorsal surface), 3 bifurcate and 4 pointed teeth in a group and moderately long outermost, unipinnate seta on ventral surface. Palp consisting of large basis, 2.2 times as long as wide and 1.9 times as long as exopod, armed with 1 plumose seta on subdistal inner margin and ornamented with 1 row of spinules on mid-outer margin. Exopod 4-segmented, proximal 3 segments with 1 seta each at inner distal corner, and distal segment with 2 apical setae. Endopod 2-segmented, 0.7 times as long as exopod; proximal segment with 2 apical setae and 1 subapical seta; ornamented with long hairs on inner margin; distal segment with 6 unequal simple setae.

Maxillule (Fig. 5 b): biramous, composed of praecoxa and palp. Praecoxal arthrite bearing 4 very strong distal claws and 5 medial elements on ventral side (proximalmost spine longest and pinnate) and 1 distally plumose seta arising from coxal endite. Palp composed of coxobasis, exopod and endopod. Coxobasis subcylindrical, 2.4 times as long as wide, armed with 5 setae (4 simple and 1 stout, pinnate). Exopod 1-segmented, 1.8 times as long as wide, bearing 4 smooth, apical setae. Endopod 1-segmented, 0.9 times as long as exopod, with 2 setae on inner margin, and 5 apical, simple setae; both rami proximally directed.

Maxilla (Fig. 5 c): 6-segmented, consisting of praecoxa, coxa, basis and 3-segmented endopod. Praecoxa well developed, 1.2 times longer than coxa, proximal endite of praecoxa small, armed with 2 bipinnate setae and 1 smooth long seta; distal endite small, with only 1 bipinnate seta. Proximal endite of coxa with 3 bipinnate setae; distal endite elongate, expanded distally and armed with 3 apical, bipinnate setae. Basis drawn out into robust, prehensile claw with serrulate inner margin and armed with 1 small simple seta at base and 1 strong bipinnate seta. Endopod 3-segmented; proximal segment armed with 4 robust, bipinnate setae; second segment with 2 bipinnate setae; distal segment smallest, with 1 unipinnate apical claw and 2 slender and smooth subapical setae.

Maxilliped (Fig. 5 d): 3-segmented, composed of syncoxa (suture between praecoxa and coxa incomplete), basis and 1-segmented endopod. Syncoxa with 4 endites, with 1, 1, 2, and 2 setae, respectively. Basis armed with 1 smooth seta and 1 pinnate seta. Endopod 1-segmented, 1.2 times as long as wide, with 2 subapical and 3 apical, unequal setae.

Legs 1–4 (Fig. 6 a–d): with 3-segmented exopod and endopod; leg 1 relatively short. Hairs present on outer margin of coxa, inner margin of basis and along outer margins of exopod and endopod of all legs, as illustrated. Both rami equal in length on leg 1, but endopod slightly shorter than exopod on legs 2–4. Third exopodal segment spine formula of legs 1–4: 4.4.4.3; setal formula: 4.5.5.5. Intercoxal plate small and unornamented on leg 1 (Fig. 2 c), but large and with 2 transverse rows of spinules (distal row slightly interrupted at middle on leg 2) in anterior view (Fig. 2 e); no ornamentation discernible in posterior view of legs 2–4 (leg 2, Fig. 2 d). All legs with inner distal seta on coxa and outer seta on basis; leg 1 basis with pinnate spine on inner distal margin. Spine and setal formulae as follows (legend: the spines and setae are denoted by Roman and Arabic numerals, respectively; the element or elements on inner margin of any segment are given first, separated by a hyphen from the outer margin element or elements; the armature of the terminal segment of each ramus has three parts separated by commas and are give in the sequence: inner margin, distal margin, and outer margin):

Coxa Basis Exopod Endopod

1 2 3 1 2 3 Leg 1 1-0 I-1 1-I 1-I 3, 1+I, III 1 -0 1-0 3, 2, 1 Leg 2 1-0 0-1 1-I 1-I 4, 1+I, III 1 -0 2-0 3, 2, 1 Leg 3 1-0 0-1 1-I 1-I 4, 1+I, III 1 -0 2-0 3, 2, 1 Leg 4 1-0 0-1 1-I 1-I 4, 1+I, II 1 -0 2-0 2, 2, 1 Leg 5 (Figs. 2 a, 3a–b): baseoendopod fused to the somite and exopod distinct at base. Baseoendopod armed with outer plumose seta, inserted on elongate basal protuberance and ornamented with 1 row of fine ventral spinules at base of exopod. Exopod about twice as long as wide; armature consisting of 3 strong but unequal spines and 1 apical plumose seta; inner apical spine 0.3 times as long as segment and 1.8 times as long as outer apical spine; outer apical spine 1.3 times as long as proximalmost spine; apical plumose seta 1.4 times as long as segment. Ornamentation as illustrated.

Leg 6 (Figs. 2 a, 3a): located dorso-laterally on genital double-somite on a small proximal hump, and as a small plate bearing 2 tiny spinules.

(* = incomplete description and/or figures;? = no details available; no. = number) Redescription of adult male. Total body length, excluding caudal setae, 412 Μm. Habitus (Fig. 7 a) slenderer than that of female. Prosome/urosome ratio 1.3, greatest width (148 Μm) at middle of cephalothorax. Body length/ width ratio 3.1. Rostral expansion moderately developed. Cephalothorax 2.3 times as wide as genital somite and representing 31.4% of total body length. Free pedigers 1–3 with almost straight lateral margins, but fourth one with rounded lateral corners. Hyaline fringes of cephalothorax and pedigers 1–3 smooth, slightly produced mid-dorsally and fourth pediger with very narrow hyaline frill, not clearly discernible. Fifth pedigerous somite expanded distally and 0.8 times as wide as genital somite. Pseudosomite between prosome and urosome narrow. Genital somite bulbous, about 0.7 times as long as wide; ornamented with 2 sensilla posteriorly (Fig. 7 a). Anal somite as in female. Spermatophore (Fig. 8 a, b) oval, 1.4 times as long as wide. Caudal rami (Fig. 8 a, b) 2.4 times as long as maximum width. Armature and ornamentation almost as in female.

Antennule (Fig. 7 b, c): 17-segmented, digeniculate, geniculation between segments 10 and 11, and 14 and 15. Setal formula: 4.2.5.1.1.3.3.0.2.1.0.3.0.1.0.2.5+2aes. Segments 3, 4, 5, 7, 8, 11, 14 and 15 with 2, 1, 2, 2, 1, 2, 2 and 2 long bipinnate setae, respectively. First segment ornamented with row of spinules at base; 11th segment plate-like, protruded dorsally (Fig. 7 c). Length ratios of antennular segments along medial axis 1.0: 0.6: 0.3: 0.4: 0.2: 0.2: 0.3: 0.5: 0.7: 0.2: 0.4: 0.8: 0.5: 0.3: 0.8: 1.1: 1.2.

Other cephalic appendages and legs 1–5 as in female.

Leg 6 (Fig. 8 a, b): cuticular plate, fused to somite at base and armed with 2 unequal, plumose setae and 1 acute spinous process; outer seta 1.3 times as long as inner one.

Ecology and distribution. As already pointed out, Paracyclopina is an Indo-Pacific genus. The ecological and geographic distribution of its hitherto known species is as follows:

P. nana Smirnov, 1935: brackish water species and known from Vladivostok, Russia (Smirnov 1935); Japan, South Korea, and China (Tai & Chen 1979; Ueda et al. 2001; Chang 2009).

P. orientalis (Lindberg, 1941): brackish water Indian species so far reported from Puducherry (erstwhile Pondicherry), Mahim, Angara (Lindberg 1941, 1946).

P. intermedia (Sewell, 1924): brackish water Lake Chilka (Sewell 1924) and from both brackish and freshwater conditions of Lake Kolleru (Ranga Reddy & Radhakrishna 1984), both in India.

P. longifurca (Sewell, 1924): same as at P. intermedia.

P. minuta (Sewell, 1934): freshwater conditions of the River Hughli, Calcuttta (now Kolkata), India (Sewell 1934).

P. sacklerae Boxshall & Jaume, 2012: anchialine and brackish habitat on the coast of Muna Island, Indonesia (Boxshall & Jaume 2012).

Lindberg (1941) described the females of Paracyclopina orientalis taken from shallow salty waters near the coast of Puducherry and from a lagoon at Oupalom on the southeast coast India. The males of this species were subsequently collected by Lindberg (1946) from a northwestern costal locality at Mahim in Mumbai (erstwhile Bombay). This shows that the species is distributed along both the southeast and northwest costal places adjacent to the Bay of Bengal and Arabian Sea, respectively. Unfortunately, Lindberg (1941) did not specify whether this species is interstitial or benthic. In the present study, it was collected in brackish interstitial conditions of pits dug out on the sandy bank of the River Godavari, following Karaman & Chappuis method (Chappuis, 1942). Given the fact that all its congeners occur near the bottom, it is difficult to clearly establish whether this is a truly interstitial or epibenthic form. Circumstantial evidence, however, shows that this species is most probably hyporheic because it was accompanied by typically interstitial taxa such as Parvulobathynella distincta Ranga Reddy, Elia & Totakura, 2011, a bathynellacean, Parastenocaris curvispinus Enckell, 1970, a harpacticoid copepod, and other unidentified cyclopoid and harpacticoid copepods.

Remarks. Paracyclopina was originally established by Smirnov (1935) for the type and only species, Paracyclopina nana Smirnov, 1935. Smirnov (1935) commented on the affinities between P. nana and the two Indian species, viz. Cyclopina intermedia Sewell, 1924 and Cyclopina longifurca Sewell, 1924. Subsequently, Lang (1946) transferred the latter two species and also another Indian species, Cyclopina minuta Sewell, 1934, to the genus Paracyclopina. The validity of these species was confirmed by Lindberg (1952), who also provided a short generic diagnosis, which has been used till date. Ranga Reddy & Radhakrishna (1984) redescribed Paracyclopina intermedia (Sewell, 1924) and Paracyclopina longifurca (Sewell, 1924) based on the material collected from both brackish and freshwater conditions of Lake Kolleru. Martínez Arbizu (2000a) reexamined some of these species and confirmed the validity of the genus. According to World Copepoda database on the genus Paracyclopina (Boxshall 2011), three species (the Russian Paracyclopina pacifica Smirnov, 1935, the Indian Paracyclopina orientalis (Lindberg, 1941), and the Indonesian Paracyclopina sacklerae Boxshall & Jaume, 2012) in addition to the above-mentioned species are also listed as valid, thus bringing the species tally to seven. However, Boxshall & Jaume (2012) did not recognize P. pacifica as a member of Paracyclopina, and provided an identification key only for the remaining six species.

Martínez Arbizu (2000a, b, 2001a, b) split the family Cyclopinidae Sars, 1913 into four families: Cyclopettidae Martínez Arbizu, 2000a, Giselinidae Martínez Arbizu, 2000b, Hemicyclopinidae Martínez Arbizu, 2001a, and Psammocyclopinidae Martínez Arbizu, 2001b. Subsequently, Martínez Arbizu (2006) also added another family Schminkepinellidae Martínez Arbizu, 2006, thus the total number of cyclopinid families going up to seven. However, according to Karanovic (2008), the characters considered by Martínez Arbizu for establishing these new cyclopinid families are ‘unreliable’. Similarly, Boxshall & Jaume (2012) also expressed doubt about the validity of the families because “no comprehensive parsimony-based test of the validity of the new families derived from the breakup of the Cyclopinidae has yet been carried out”.

As for Paracyclopina orientalis (Lindberg, 1941), the original account is rather incomplete in several respects. Hence it is redescribed here based on the present material. The principal morphological characters in which P. orientalis differs from its congeners are given in Table 1. The material under examination closely agrees with the original account of P. orientalis (Lindberg, 1941) except for some minor differences (see below). Surprisingly, this species, as rightly observed by Boxshall & Jaume (2012), has closer affinity with the Indonesian P. sacklerae, than with any of its three Indian congeners, as evident from the strikingly robust terminal spine on the exopod of leg 4 in both sexes and also the presence of three robust spines on the free exopodal segment of the female leg 5.

The present study shows that the endopod of maxilliped in P. orientalis is only one-segmented whereas it is two-segmented in P. sacklerae (see Boxshall & Jaume, 2012: 38, Fig. 2 g), and in P. longifurca and P. intermedia (Ranga Reddy & Radhakrishna, 1984: 34, Pl. 6, Fig. 8). The discrepancies in Lindberg’s (1941) account, due most probably to incomplete depiction, are as follows: i) the first exopodal segment of the mandible is without vs. with a seta; ii) the maxillulary endopod has five instead of seven setae; iii) the one-segmented endopod of maxilliped has six vs. five setae; and iv) leg 5 exopodal segment has longer apical seta, but it is rather short in Lindberg’s figure (1941, Fig. 1 f). As already pointed out, Lindberg (1946) provided no figures for the male of P. orientalis. Hence, it is not possible to make a critical comparison of the present material with Lindberg’s (1941) account of the male.