Paragrillotia apecteta, Beveridge & Justine, 2007

Beveridge, Ian & Justine, Jean-Lou, 2007, Paragrillotia apecteta n. sp. and redescription of P. spratti (Campbell & Beveridge, 1993) n. comb. (Cestoda, Trypanorhyncha) from hexanchid and carcharhinid sharks off New Caledonia, Zoosystema 29 (2), pp. 381-391 : 383-386

Paragrillotia apecteta n. sp.

( Figs 1 ; 2 )

MATERIAL EXAMINED. — Holotype from spiral valve of Hexanchus nakamurai, Baie du Santal, Lifou , New Caledonia, 20°53’30’’S, 167°01’60’’E, depth 298-397 m, coll. J.-L. Justine, 26.I.2002 ( MNHN JN 01F1 ). — Same data, 3 paratypes, on 5 slides ( MNHN JN 01F2 -JN 01F6).

ETYMOLOGY. — The species name, apecteta , is derived from the Greek apectetos, meaning unkempt or uncombed and alludes to the complex array of hooks on the external surface of the tentacle.

DESCRIPTION

Based on 4 immature specimens with up to 11 segments.Small cestodes, up to 25 mm long, maximum width 550. Scolex acraspedote, 4.3-5.4 (4.9, n = 4) mm long; maximum width in pars bulbosa, 760-940 (810, n = 4); 2 oval bothria with thickened margins and median indentation in posterior margin; pars bothrialis 940-1020 (980, n = 4) long; pars vaginalis 2.10-2.95 (2.63, n = 4) mm long; tentacular sheaths straight in anterior part of pars vaginalis, coiled in posterior part; bulbs elongate, 1.6-2.0 (1.81, n = 4) mm long, width 260-340 (300, n = 4); bulb length:width ratio 1:5.2-7.4 (6.3, n = 4); prebulbar organ and glands within bulb absent; retractor muscle inserts in mid-region of bulb, continued posteriorly on internal surface of bulb by row of cells; pars post-bulbosa absent; mean scolex ratio (pars bothrialis:pars vaginalis: pars bulbosa) 1:2.7:1.8.

Tentacles with slight basal swelling; everted tentacles up to 1100 long, 170-240 (200, n = 5) in diameter at base, 140-170 (160, n = 5) in diameter in metabasal region. Tentacular armature heteroacanthous, heteromorphous; hooks hollow; hook rows appear to begin on internal surface, terminate on external surface of tentacle. Distinctive basal armature present; initial 2 rows of hooks slender, elongate on internal surface, diminishing in size towards external surface; third row of hooks with characteristic, enlarged hooks of unusual shapes; principal rows commence at fourth row; on external surface, hook rows more numerous than on internal surface at base, hooks of external surface sagittate, 18-53 (39, n = 5) long, base 5-15 (9, n = 5) wide; hooks become smaller distally; at level of hook row 3 on external surface, hooks small, uncinate, arranged in compact array, approximately 12 rows long and 6 columns wide. Hook rows of metabasal region consist of 7 hooks; space present between hook files 1(1’) on internal surface; hooks 1(1’) large, robust, uncinate with elongate base, 105-125 (112, n = 5) long, base 80-90 (84, n = 5) long; hooks 2(2’) similar in shape but smaller, 78- 93 (82, n = 5) long, base 50-55 (53, n = 5) long; hooks 3(3’) erect, broadly falcate, with narrower base 75-123 (102) long, base 20-33 (31, n = 5) long; hooks 4(4’) slender, falcate with narrow base, 78-115 (96, n = 5) long, base 20-28 (24, n = 5) long; space frequently present between hooks 4(4’) and 5(5’); hooks 5(5’) slender, variable in length, 68-165 (114, n = 5) long, base 18-35 (26, n = 5) long; hooks 6(6’) slender, shorter, 58-125 (82, n = 5) long, base 10-25 (17, n = 5) long; hooks 7(7’) slender, much shorter than hooks 6(6’), 29-38 (33, n = 5) long. Two or 3 rows of intercalary hooks, with 4-6 hooks in first 2 rows and up to 4 hooks in third row, if present; intercalary hooks begin at level of hooks 4(4’), continue just beyond hooks 6(6’); intercalary hooks 35-88 (69, n = 5) long, base 10-28 (16, n = 5) wide. External surface of tentacle with chainette of tiny hooks present in middle of surface with one or more chainette elements per principal row of hooks; chainette hooks uncinate 10-15 (13, n = 5) long, base 3 (3, n = 5) wide.

Segments craspedote, largest mature segment 2.57 mm long, maximum width 520; genital pores lateral, alternate irregularly, in posterior half of segment margin, 1050 (41%) from posterior end. Hermaphroditic sac 180-250 (220, n = 2) long, width 60-88 (74, n = 2); testes numerous, c. 400, filling entire medulla, with c. 50 testes posterior to ovary; testes confluent anterior to uterus; arranged in single layer, 43-60 (48, n = 5) in diameter. Ovary not fully developed, bi-lobed in dorso-ventral view, well anterior to posterior margin of segment. Uterus median, tubular, extends from ovarian isthmus to anterior quarter of segment. Vitelline follicles circumcortical.Ventral osmoregulatory canal c. 30 in diameter; canals on each side of segment joined by transverse canal at posterior margin of segment.

REMARKS

The species described herein is allocated to the genus Paragrillotia on the basis of possessing two bothria, a distinctive basal armature, rows of intercalary hooks and a chainette in the centre of the external surface of the tentacle. The species resembles the type species, P. similis , in having 6 or 7 hooks per principal row, with 6 in P. similis and 7 in P.apecteta n. sp. (compared with 10 in P. spratti ) but differs in having more intercalary hooks, with 4-6 hooks in the first two rows and up to four hooks in third row, if present. By contrast, in P. similis , the first intercalary row consists of four hooks and the second row of one hook. In addition, the basal armature differs in lacking the enlarged hooks seen on the external surface of the tentacle of P. similis .

The description of the new species is limited by the immaturity of the specimens available and by their contracted nature. The tentacular armature appears to begin on the internal surface of the tentacle and terminate on the external surface, but this is difficult to determine and needs to be confirmed from additional collections. In addition, the terminal genitalia were not fully developed and it was not possible to determine whether a cirrus sac or an hermaphroditic sac was present. As congeners have an hermaphroditic sac, the same term has been applied in P. apecteta n. sp.

Figures

FIG. 1. — Paragrillotia apecteta n. sp. from Hexanchus nakamurai Teng, 1962: A, external surface of tentacle, metabasal region; B, antibothrial surface of tentacle, metabasal region of tentacle with hooks of chainette shown as solid hooks; C, bothrial surface, basal region of tentacle; D, basal region of tentacle, antibothrial surface. Scale bar: 100 µm.

FIG. 2. — Paragrillotia apecteta n. sp. from Hexanchus nakamurai Teng, 1962: A, scolex; B, mature segment; C, hooks of principal rows. Scale bars: A, B, 100 µm; C, 10 µm.