Acanthoplacatus adlardi, Ernst & Jones & Whittington, 2001

Ernst, Ingo, Jones, Malcolm K. & Whittington, Ian D., 2001, A new genus of viviparous gyrodactylid (Monogenea) from the Great Barrier Reef, Australia with descriptions of seven new species, Journal of Natural History 35 (3), pp. 313-340 : 321-323

Acanthoplacatus adlardi sp. nov.

( Figures 3 , 4A ±D)

Type host. Siganus punctatus (Forster, 1801) (Siganidae) .

Type locality. Heron Island , Great Barrier Reef , Queensland, Australia. Site on host. This species was found most frequently on the dorsal ®n (see table 1). Holotype. QM 215973. Paratypes. QM 215974 ±5. Etymology. This species is named to honour Dr Robert Adlard (Queensland Museum), a friend and colleague. Infection details. Prevalence 63%, eight ®sh examined, LCF 173 mm (152± 211 mm); mean intensity 26 (10±55), three ®sh examined, LCF 164 mm (152±180 mm) .

Description. Sclerite measurements taken from 16 worms mounted in Malmberg’s ®xative. Measurements of other organs taken from six whole mounts stained with Ehrlich’s haematoxylin. Numerous live worms examined for structure of soft body organs and excretory system. Total length 279 (245±303, n 5 5), maximum body width 62 (53±80, n 5 6) at level of uterus if embryo present or at level of testis for worms with small embryo (®gure 4A). Hamulus length 37 (35±39, n 5 16); hamulus point length 19 (17.5±20.5, n 5 16); hamulus root length 20.5 (19±22.5, n 5 16); hamulus shaft length 28 (26.5±29, n 5 16). Dorsal root tissue cap length 8 (7.5±8.5, n 5 16), width 4 (3.5±5, n 5 15) (®gure 4D). Ventral bar simple, variable in shape (®gures 3, 4D). Ventral bar 5.5 (4±6, n 5 16) long, 14 (13±16, n 5 16) wide. Ventral bar membrane 17.5 (16±20, n 5 15) long. Total length of ventral bar and membrane 22.5 (21±25, n 5 15). Transition between ventral bar and ventral bar membrane not distinct. Marginal hooks small with hook point extending to, or only slightly past, toe; total length of marginal hook 29 (27±31, n 5 15); length of sickle 4 (3.5±4, n 5 14); length of handle 26 (24±28, n 5 13) (®gure 4B).

Gland cells posterolateral to pharynx range from minimum diameter of 9 (7±12, n 5 6) to maximum of 12.5 (9±15, n 5 6). Anterior lobe of pharynx 26 (24±28, n 5 6) wide, posterior lobe 29.5 (28±42, n 5 6) wide. Gut caeca extend posteriorly lateral to uterus, terminating posterior to testis. Male copulatory organ with one large, two moderate and four small spines (11 21 4) (®gure 4C). Male copulatory organ 11±15 long, 12±13 wide (n 5 2). Developing sclerites of F2 embryos may be visible within large F1 embryos; no sclerites of F3 embryos visible. Oocyte 19.5 (4±34, n 5 5) long, 21 (20±24, n 5 5) wide, contained within ECFR. Testis 14.5 (6±25, n 5 6) long, 14 (8±21, n 5 6) wide. Testis overlaps ECFR dorsally. Five cells surround posterior portion of each gut caecum and single cell lies medially near posterior terminations; cells range from minimum diameter of 11.5 (9±16, n 5 16) to maximum diameter of 15.5 (13 ±18, n 5 6). Two anterior-most cell pairs and posterolateral cell pair ventral to gut. Single medial cell and remaining two cell pairs dorsal to gut (®gure 4A) .

Sclerite size and seasonality. For this species 13 specimens were collected in summer (January 1998) and three specimens were collected in winter (July 1995). The three specimens collected in winter have hamulus length, hamulus point length and total marginal hook length measurements which are slightly greater than the range reported for the summer sample.

Comments. Acanthoplacatus adlardi sp. nov. resembles most closely A. puelli sp. nov., A. shieldsi sp. nov. and A sigani sp. nov. It diOEers from A. sigani sp. nov. as described above for that species. Acanthoplacatu s adlardi sp. nov. can be distinguished from A. shieldsi sp. nov. because it has larger ventral bar total length and ventral bar membrane length (see table 2). Considerable overlap occurs for all 13 sclerite characters between A. adlardi sp. nov. and A. puelli sp. nov. Acanthoplacatus puelli sp. nov. however, has more slender, elongate hamuli, a 11 21 6 sclerite con®guration on the male copulatory organ and obvious depressions anteriorly on the ventral surface of the hamuli.

Figures

FIG. 3. Variation of ventral bar and ventral bar membrane within and between species of Acanthoplacatus gen. nov. Scale bar 5 20 mm.

FIG. 4. Acanthoplacatus adlardi sp. nov. (A) Whole worm drawn from permanent whole mounts, ventral view. Scale bar 5 50 mm. (B) Marginal hook. (C) Male copulatory organ. B±C to the same scale. Scale bar 5 10mm. (D) Hamuli and ventral bar. Scale bar 5 20 mm. pp, pharyngeal processes.