Boholina parapurgata, Boxshall, Geoff A. & Jaume, Damià, 2012

Boxshall, Geoff A. & Jaume, Damià, 2012, Three new species of copepods (Copepoda: Calanoida and Cyclopoida) from anchialine habitats in Indonesia, Zootaxa 3150, pp. 36-58 : 45-54

Boholina parapurgata n. sp.

( Figs. 5–10 )

Type material. Holotype female, 7 paratype females, 5 paratype males collected from sinkholes on the coast at the edge of Walengkabola village (5º 11.052’ S 122º 35.159’ E), Muna Island, Indonesia, on 18 September 2007 by G.A. Boxshall and D. Jaume. Registration numbers: holotype female [ MZB.Cru Cop.105], 3 paratype females and 3 paratype males [ MZB.Cru Cop.106] in Museum Zoologicum Bogoriense, 4 paratype females and 2 paratype males in Natural History Museum, London [ BMNH 2011.1172-1177].

Etymology. The name of the new species alludes to its close resemblance to Boholina purgata Fosshagen & Iliffe, 1989 .

Description of adult female. Body ( Fig. 5 A) with a mean length of 0.78 mm (range 0.74 to 0.83 mm, based on 7 specimens). Prosome 5-segmented, comprising cephalosome, first to third free pedigerous somites and double somite consisting of completely fused fourth and fifth pedigerous somites; prosome reaching maximum width at rear of cephalosome; postero-lateral corners of second and third pedigerous somites forming acute posteriorlydirected points ( Fig. 9 B); postero-lateral corners of posterior double-somite rounded, symmetrical. Nauplius eye lacking. Ratio of prosome to urosome length about 3:1. Urosome with only 3 obvious segments ( Fig. 5 B) but 4- segmented, comprising genital double-somite and 2 free abdominal somites plus hoop-like anal somite (arrowed in Fig. 5 D) largely telescoped within preceding second free abdominal somite and entirely concealed beneath extensive somitic hyaline membrane. Genital double-somite ( Fig. 5 C) symmetrical, widest about at mid-length; posterior border ornamented with smooth hyaline membrane dorsally and strongly dentate hyaline membrane ventrally ( Fig. 5 C); genital openings paired, located close together on mid-ventral surface; seminal receptacles paired, located lateral to and posterior to genital openings; 2 pairs of sensillae present, one pair positioned adjacent to medial margin of gonopores, second pair located ventro-laterally near posterior margin of double-somite. First and second free abdominal somites subequal in length; first with smooth hyaline membrane all around posterior margin, second with posterior margin hyaline membrane expanded mid-dorsally to form double-pointed flap functioning as pseudoperculum concealing anal opening. Anal somite extremely short, concealed within posterior rim and hyaline membrane of second free abdominal somite.

Caudal rami ( Fig. 5 A–B) about 1.5 times longer than wide (measured from base to level of insertion of distal seta IV), with pointed dorsal process in middle of distal margin ( Fig. 5 B, D); caudal setae II to VII present (seta I lacking); seta II spiniform, seta III about half length of seta VI, seta V longer than seta IV, both plumose; dorsal seta VII short, plumose; slight asymmetry noted with short row of tiny setules present distally on inner margin of left ramus.

Rostrum weakly developed ( Fig. 10 A) as triangular area of cuticle tapering back from broad base at junction with frontal margin of dorsal cephalic shield to narrow rounded tip between bases of antennules; pair of long sensillae in middle third of rostrum.

Antennules ( Fig. 6 A) symmetrical, extending almost to end of prosome; 24-segmented with all articulations expressed, except between segments II–IV and XXVI–XXVIII; segment 8 double comprising ancestral segments X and XI, but with articulation incompletely expressed. Armature formula as follows: segment 1 (ancestral segment I) 1 seta + 1 aesthetasc; segment 2 (ancestral segments II–IV) 6 setae + ae; segment 3 (V) 2 + ae; segment 4 (VI) 2; segment 5 (VII) 2 + ae; segment 6 (VIII) 2; segment 7 (IX) 2 + ae; segment 8 (X–XI) 3 + 2 ae; segment 9 (XII) 1 seta; segment 10 (XIII) 1 + ae; segment 11 (XIV) 1 + ae; segment 12 (XV) 1 + ae; segment 13 (XVI) 1 + ae; segment 14 (XVII) 1 seta; segment 15 (XVIII) 1 + ae; segment 16 (XIX) 1 seta; segment 17 (XX) 1 seta; segment 18 (XXI) 1 + ae; segment 19 (XXII) 1 seta; segment 20 (XXIII) 1 seta; segment 21 (XXIV) 1 + 1; segment 22 (XXV) 1 + 1+ ae; segment 23 (XXVI) 1 + 1; apical segment 24 (compound XXVII–XXVIII) 5 + ae.

Antenna ( Fig. 6 B) biramous. Coxa short, bearing plumose seta at distomedial angle. Basis with 2 subequal plumose setae on distomedial angle. Exopod 9-segmented, articulation between fourth and fifth segments incomplete, apical segment small: setal formula as follows: 1, 1, 1, 1, 1, 1, 1, 1, 3: all setae plumose; articulations between two to five with spinule rows. Endopod 2-segmented: proximal segment with 2 unequal, naked setae, ornamented with oblique spinule row; compound distal segment expanded into medial lobe bearing 8 setae distally and on outer distal margin, and with distal portion crowned with 6 setae; segment ornamented with small serrated process subdistally on medial margin and adjacent spinule row.

Mandible ( Fig. 6 C) with cutting edge of coxal gnathobase comprising about 10 short, cuspidate or simple teeth plus small dorsal spinulose seta; ventral-most teeth larger. Palp biramous; basis with 4 unequal setae on inner margin, and with spinule row proximally on outer surface. Exopod indistinctly 5-segmented, setal formula 0, 1, 1, 1, 2. Proximal endopodal segment with 4 setae at distomedial angle; distal segment with 10 distal margin setae.

Maxillule ( Fig. 7 A) with praecoxal arthrite carrying 10 marginal spines plus 4 stiff setae on posterior surface. Coxal epipodite with 9 plumose setae; coxal endite with 4 spinulose setae. Basis fused to both rami: armed with 4 spinulose setae on proximal endite; distal basal endite incorporated into segment, with 5 setae; basal exite represented by single vestigial seta. Exopod bearing 10 marginal setae. Endopod with first segment fused to basis, represented by 4 distal margin setae; 2 free segments armed with 4 and 7 setae respectively.

Maxilla ( Fig. 7 B) 6-segmented, comprising praecoxa and coxa, allobasis and 3-segmented free endopod. Armature of praecoxal and coxal endites 5, 3, 3, 3; all setae bilaterally spinulate; distal coxal endite with spinule row. Allobasis with 6 setal elements in total, 4 on produced basal endite, 1 strong and claw-like, plus 2 setae derived from fused first endopodal segment; ornamented with spinule row. Free endopod setal formula: 2, 1, 2; long setae on allobasis and on endopodal segments sparsely spinulate bilaterally.

Maxilliped ( Fig. 7 C) 8-segmented with syncoxa, basis and free 6-segmented endopod. Syncoxa with 1, 2, 2, 3 setae on medial margin lobes; first lobe seta bilaterally spinulate; one seta on second lobe very long and naked, other seta plus setae on third lobe sparsely bilaterally spinulate; fourth lobe setae naked; small patch of denticles present on medial surface of fourth lobe. Basis about as long as syncoxa, armed with 3 plumose setae and carrying row of strong spinules along medial margin of segment. Free endopod setal formula: 2, 4, 4, 3, 3 + 1, 4.

Legs 1–5 ( Fig. 8 A–E) biramous, with 3-segmented rami except endopod 2-segmented in leg 5. Legs with smooth, unornamented intercoxal sclerites, except short spinule rows present on anterior surface of leg 2. Basis of leg 1 with rounded digitiform process distally, arising posteriorly near base of endopod. Armature of legs 1 to 5 as follows:

Outer distal angles of first and second endopodal segments of legs 1 to 4 each drawn out into acute process, particularly marked in legs 1 and 2. Endopod segment 3 with large, acute process at outer distal angle in leg 1 only. Second exopodal segment of leg 1 ( Fig. 8 A) with conspicuous spinulate process distally, in axil of outer spine; third exopodal segment with marginal spinule row on anterior surface. Articulations between endopodal and exopodal segments ornamented with spinule rows. Inner basal seta on leg 1 long, bilaterally spinulate, reaching to base of middle seta on third endopodal segment. Setae on both rami plumose; outer spines on distal exopodal segment of leg 1 flagellate; outer spines on legs 2 to 4 with serrate marginal membrane(s) as figured. Terminal spine on exopod of legs 1 to 3 ornamented with serrate membrane externally and plumose internally, that on leg 4 bilaterally serrate. Leg 4 with inner distal setal element on third exopodal segment 61 μm long, about 1.5 times longer than adjacent terminal spine (41 μm) and shorter than segment (= 70 μm long).

Leg 5 ( Fig. 8 E) biramous, with 3-segmented exopod and 2-segmented endopod, intercoxal sclerite smooth and unornamented. Basis of leg 5 with small, acute process located on posterior surface near base of exopod and with large pore on anterior surface. Exopod longer than endopod: tip of endopod reaching beyond level of proximal outer spine on third exopodal segment; distal endopodal segment 2.6 times longer (42 μm) than wide (16 μm). Outer spines on exopod each with serrate membrane bilaterally. Terminal spine on exopod with serrate membrane externally and finely serrate membrane internally, terminal spine (53–57 μm) about 1.2 times longer than inner distal spine (41–47 μm), and longer than segment (44–48 μm). First and second exopodal segments each ornamented with pore on anterior surface at origin of outer spine.

Description of adult male. Body ( Fig. 9 A, B) length ranging from 0.66 to 0.71 mm, with a mean of 0.69 mm (based on 4 specimens). Prosome 5-segmented as in female: maximum width at level of first pedigerous somite; postero-lateral corners of second and third pedigerous somites (arrowed in Fig. 9 B) forming acute posteriorlydirected points, as in female. Ratio of prosome to urosome length about 2.4:1. Urosome 5-segmented ( Fig. 9 C); comprising genital somite and 3 free abdominal somites plus hoop-like anal somite largely telescoped within preceding second free abdominal somite and entirely concealed beneath somitic hyaline membrane, as in female. Genital somite slightly asymmetrical, with single gonopore opening posterolaterally on left side; genital and first to third free abdominal somites similar in length, although often variably telescoped within preceding somite; each with hyaline membrane around posterior border, except membrane lacking ventrally on genital somite. Anus opening terminal, located between caudal rami, concealed beneath pseudoperculum formed by hyaline membrane on third free abdominal somite.

Caudal rami ( Fig. 9 A, C) symmetrical, about 1.7 times longer than wide and bearing distal spinous process dorsally, as in female. Caudal seta I absent; caudal setae II–VII, as in female.

Antennules short, asymmetrical. Left antennule non-geniculate, 24-segmented as in female and extending almost to posterior end of prosome. Right antennule ( Fig. 10 B) geniculate, 22-segmented. Armature as follows: segment 1 (ancestral segment I) 2 setae + aesthetasc; segment 2 (corresponding to compound ancestral segments II–IV) 6 + 2 ae; segment 3 (V) 2 + ae; segment 4 (VI) 2; segment 5 (VII) 2 + ae; segment 6 (VIII) 2; segment 7 (IX) 2 + ae; segment 8 (X) 1 seta; segment 9 (XI) 1 + ae; segment 10 (XII) 1; segment 11 (XIII) 1 + ae; segment 12 (XIV) 1 + ae; segment 13 (XV) 1 + ae; segment 14 (XVI) 2; segment 15 (XVII) 2; segment 16 (XVIII) 1 + ae; segment 17 (XIX) 1 modified, fused spine; segment 18 (XX) 1 modified, fused spine + 1 seta; segment 19 (XXI– XXIII) 2 setae + ae; segment 20 (XXIV–XXV) 2 + 2 + ae; segment 21 (XXVI) 1 + 1, segment 22 (XXVII– XXVIII) 5 + ae.

Leg 5 ( Fig. 10 C) strongly asymmetrical; coxae and intercoxal sclerite fused to form common base. Left leg biramous: basis with slender outer basal seta located on posterior surface; exopod 3-segmented; first segment with long (63 μm), bilaterally serrate outer spine; second segment modified, bearing strongly reflexed spine on outer margin; third segment highly transformed bearing multiple short processes and one long, naked, modified setal element. Right leg biramous, basis with slender outer basal seta located on posterior surface; exopod unsegmented; segment with 2 outer spines (proximal spine 33–35 μm, distal spine 62–63 μm in length) and terminal spine 34–35 μm long, plus a short spine vestige located subdistally towards the medial surface; endopod forming an elongate lobe, about 61 μm long, by 17–18 μm wide (3.6 times longer than wide); armed with 2 slightly sigmoid spines, apical spine 17–19 μm long, subapical spine 12–13 μm ( Fig. 10 C).

Remarks. The family Boholinidae and the genus Boholina were established by Fosshagen & Iliffe (1989) on the basis of two new species discovered in a brackish pool in San Vincente Cave on Bohol Island in the Philippines. In the original description, the urosome of the females and males were described as 3- and 4-segmented respectively ( Fosshagen & Iliffe 1989). We find that the anal somite has been overlooked in both sexes and this has been verified by examination of the types of B. crassicephala Fosshagen & Iliffe, 1989 (Reg. No. BMNH 1989.58–67). It is represented by a short hoop of cuticle, which lies more-or-less completely telescoped within the preceding free abdominal somite. The presence of the extensive hyaline membrane around the entire posterior margin of that somite adds to the concealment. A similarly tiny and concealed anal somite was noted for genera such as Edaxiella Fosshagen, Boxshall & Iliffe, 2001 , Oinella Fosshagen, Boxshall & Iliffe, 2001 and Gloinella Fosshagen, Boxshall & Iliffe, 2001 within the closely related Epacteriscidae ( Fosshagen et al. 2001) .

Both sexes of the type species, B. crassicephala , were fully described in 1989 but the description of the second species, B. purgata Fosshagen & Iliffe, 1989 , focused only on differences and several illustrations were provided to facilitate comparison of key characters between the two species. The species differed in several fine scale characters: the most important of which were, the posterior angles of the tergites on the second and third pedigerous somites are rounded in B. crassicephala but pointed in B. purgata , the lengths of the antennules relative to the prosome, and the armature of the male leg 5. On the exopod of the right leg 5 of the male there are four strong spines in B. crassicephala but only three strong spines plus a vestige in B. purgata . In all of these characters the new species closely resembles B. purgata .

The new species can be distinguished from B. purgata by the length and shape of the endopod of the female leg 5. In the former the distal tip of the endopod extends beyond the level of the origin of the proximal spine on the outer margin of the third exopodal segment, and the distal endopodal segment is 2.6 times longer than wide, whereas in the latter the distal tip only extends as far as the articulation between second and third exopodal segments and the distal endopodal segment is only 1.1 times longer than wide. Also in the female leg 5, the terminal spine on the exopod is longer than the segment in the new species but shorter than it in B. purgata .

The differences between the males are similarly fine scale: the unsegmented endopod of the right leg 5 of the male is 2.6 times longer than wide in B. purgata and the outer margin is evenly convex so the maximum width is about at mid-length, whereas in the new species the endopod is 3.6 times longer than wide and the maximum width is in the distal third. This endopod bears two slender setae in the former species but two sigmoid spines in B. parapurgata n. sp.

Such fine scale differences are sometimes difficult to interpret. Little is known about variability in Boholina and, like Paracyclopina , the genus appears to prefer low salinity, brackish waters. We consider that the B. parapurgata population from Muna ( Indonesia) and the B. purgata population from Bohol ( Philippines) are distinct species, but we strongly recommend sampling at suitable intermediate locations to search for additional Boholina populations.

Figures

FIGURE 5. Boholina parapurgata n. sp., adult female. A, habitus, dorsal; B, urosome, dorsal; C, genital double-somite and first free abdominal somite, ventral view showing paired gonopores and internal paired seminal receptacles (dotted lines); D, posterior end of urosome, showing reduced, hoop-like anal somite (arrowed) entirely telescoped within preceding somite and concealed by extensive intersomitic membrane, dorsal. Scale bars: A = 250 μm, B = 100 μm, C, D = 50 μm.

FIGURE 6. Boholina parapurgata n. sp., adult female. A, antennule; B, antenna; C, mandible. Scale bars: A = 100 μm, B, C = 50 μm.

FIGURE 7. Boholina parapurgata n. sp., adult female. A, maxillule; B, maxilla; C, maxilliped. All scale bars = 50 μm.

FIGURE 8. Boholina parapurgata n. sp., adult female. A, leg 1, anterior; B, leg 2, anterior; C, leg 3, anterior; D, leg 4, anterior; E, leg 5, anterior. All scale bars = 50 μm.

FIGURE 9. Boholina parapurgata n. sp., adult male. A, habitus, dorsal; B, habitus lateral, showing pointed angles to tergites of pedigerous somites (arrowed); C, urosome, ventral: Scale bars: A, B = 250 μm, C = 100 μm.

FIGURE 10. Boholina parapurgata n. sp., adult female. A, rostrum, ventral; adult male. B, geniculate right antennule; C, leg 5, posterior: All scale bars = 50 μm.