Multitestis paramagnacetabulum, Bray, Rodney A., Cribb, Thomas H. & Justine, Jean-Lou, 2010

Bray, Rodney A., Cribb, Thomas H. & Justine, Jean-Lou, 2010, Multitestis Manter 1931 (Digenea: Lepocreadiidae) in ephippid and chaetodontid fishes (Perciformes) in the south-western Pacific Ocean and the Indian Ocean off Western Australia, Zootaxa 2427, pp. 36-46 : 42-44

Multitestis paramagnacetabulum n. sp.

( Figs 9–10 )

Type-host: Platax orbicularis (Forsskål) , orbicular batfish (juv) ( Ephippidae ).

Site: Intestine.

Type-locality: Ningaloo Reef, Western Australia (22°42’S. 113°40’E, April, 2000).

Prevalence: 1 of 2 (50%).

Voucher specimens: Holotype QM G 231079, paratypes QM G 231080 – 231085, BMNH 2010.2.10.1-5.

Description: Based on 11 specimens. Measurements in Table 2 . Soma almost circular but with slightly protuberant anterior region, short posterior dorsosubterminal ‘tail’. Tegument spinous throughout most of soma; spines minute, not detected on ‘tail’. Oral sucker subterminal, cup-shaped. Ventral sucker large, oval, aperture in form of depressed central region along length of sucker. Prepharynx short. Pharynx subglobular. Oesophagus short. Intestinal bifurcation in posterior forebody. Caeca arcuate, reaching around body parallel to margin, terminating blindly fairly close to posterior extremity of soma, not extending into ‘tail’, termination often obscured by vitelline follicles.

Testes 11, oval, in 2 rosette-like clusters, ventral and overlapping caeca in region between mid-ventral sucker and mid-hindbody, poral field with 6 testes; aporal field with 5. External seminal vesicle saccular, posterodorsal to cirrus-sac. Cirrus-sac claviform, passing transversely dorsal to anterior part of ventral sucker. Internal seminal vesicle oval. Pars prostatica oval or bipartite, lined with anuclear cell-like bodies. Ejaculatory duct long, relatively wide. Genital atrium large, pocketed. Genital pore sinistral, bifurcal, ventral to left caecum.

Ovary multilobate, just posterior to ventral sucker, median. Canalicular seminal receptacle oval, dorsal to ovary. Laurer’s canal not detected. Uterus initially passes posteriorly over ventral surface of ovary, reaches to about mid-hindbody, then passes anteriorly over ventral surface of ovary and into space between ovary and ventral sucker. Eggs relatively few, weakly tanned, operculate. Metraterm muscular, wide, shorter than cirrussac. Vitellarium follicular; dorsal field almost continuous in soma, absent in around edge of worm, anterior to level of pharynx and in median region from mid-ventral sucker posteriorly; not reaching into tail.

Excretory pore dorsally subterminal, on ‘tail’. Excretory vesicle I-shaped, initially narrow, widens in posterior soma, mostly obscured by other internal organs, extent not detected.

Discussion. The worms from Ningaloo are similar to those described by Mamaev (1970) and Bray & Cribb (2003) as Multitestis magnacetabulum , but differ consistently in the testes always being situated a little more posteriorly ( Fig. 9 ). Both Mamaev (1970) and Bray and Cribb (2003) stated that the testicular follicles are lateral to the ventral sucker, whereas in the Ningaloo specimens the testes are mostly in the hindbody, although overlapping the ventral sucker. This means that the post-testicular region is relatively shorter in the Ningaloo specimens. Giving dimensions is a problem as the specimens illustrated in detail by Mamaev (1970) lack the distinctive tail-like appendage which always occurs in well-fixed specimens of this species. Mamaev (1970) gives outline illustrations of the shapes taken up by this species, including specimens with ‘tails’, indicating that the fixation method he used often caused contraction or distortion. Nevertheless several dimensions can be quoted from our own measurements (Bray & Cribb 2003 and original data) to indicate the distinctness of the specimens from Ningaloo: pre-testicular distance (34–43% of body length vs 17–27% (our data) and 34–37% (from Mamaev’s illustrations of tailless specimens)), post-testicular distance (22–33% of body-length vs 37–51% (our data) and 21–26% (from Mamaev’s illustrations of tailless specimens)). Measurements of these worms are included in Table 2 where they are compared with a series of measurements taken from M. magnacetabulum from Platax teira from Heron Island and New Caledonia. The specimens from Ningaloo, Heron Island and New Caledonia were fixed in the same way, so the slight differences found can be considered genuine local variation.

Figures

FIGURES 7 – 10. 7 – 8. Multitestis magnacetabulum Mamaev, 1970 ex Platax teira, Heron Island. 7. Ventral view, uterus in outline, vitellarium omitted. 8. Ventral view, vitellarium and outline of suckers only. 9 – 10. Multitestis paramagnacetabulum n. sp. ex Platax orbicularis, Ningaloo. 9. Ventral view of holotype, uterus in outline, vitellarium omitted. 10. Ventral view of holotype, vitellarium and outline of suckers only. Scale-bars: 7, 8, 500 µm; 9, 10, 200 µm.

Tables

TABLE 2. Dimensions and ratios of Multitestis magnacetabulum and M. paramagnacetabulum n. sp.

Species	Multitestis magnacetabulum	Multitestis magnacetabulum	Multitestis paramagnacetabulum n.sp.
Host	Platax teira	Platax teira	Platax orbicularis
Locality	Heron Island	New Caledonia	Ningaloo
n	18	1	11
Length	636–1,351 (874)	781	520–625 (603)
Width	570–957 (722)	748	419–621 (500)
Forebody	217–366 (277)	295	176–219 (202)
Pre-oral lobe	8–18 (11)	7	0–5 (2)
Oral sucker	98–148 × 118–168 (114 × 140)	136 × 155	68–92 × 85–109 (75 × 97)
Prepharynx	0	0	7–21 (15)
Pharynx	57–99 × 60–103 (74 × 80)	100 × 122	45–60 × 55–71 (52 × 63)
Oesophagus	0–17 (2)	0	0–28 (11)
Intestinal bifurcation to ventral sucker	64–172 (118)	90	0–56 (15)
Vitellarium to ventral sucker (V-VS)	117–221 (163)	201	74–132 (92)
Ventral sucker (VS)	141–225 × 192–318 (175 × 250)	182 × 267	87–142 × 141–186 (103 × 157)
Cirrus-sac	205–347 × 58–140 (255 × 86)	274 × 82	196–293 × 60–88 (253 × 75)
Extent of external seminal vesicle into hindbody (EESSH)	0	0	0–78 (35)
VS to Ovary	0	0	0–36 (9)
Ovary	88–184 × 102–219 (126 × 162)	98 × 132	46–131 × 83–149 (88 × 120)
Testicular field Distance between testicular fields	222–407 × 164–330 (290 × 228) 102–275 (155)	254–276× × 226–236 158	151–229 × 99–205 (186 × 147) 115–232 (147)
Post-testicular region	247–642 (383)	301	121–207 (158)
Post-caecal length	120–310 (215)	?	146–159 (152)
Eggs	49–58 × 20–31 (54 × 25)	52 × 27	49–62 × 28–39 (57 × 34)
Width as % of body-length	71–94 (84)	96	78–93 (83)
Forebody as % of body-length	27–37 (32)	38	30–39 (34)
Sucker-length ratio	1:1.36–1.70 (1.53)	1:1.3	1:1.2–1.9 (1.4)
Sucker-width ratio	1:1.6–1.9 (1.8)	1:1.7	1:1.5–1.8 (1.6)
Pharynx: oral sucker ratio	1:1.5–2.0 (1.8)	1:1.3	1:1.4–1.6 (1.5)
VS-Ovary as % of body-length	0	0	0–5.4 (1.5)
EESVH as % of VS-Ovary	N/A	N/A	N/A
Post-testicular region	37–51 (43)	39	22-33 (26)
Cirrus-sac length% of body-length	25–34 (30)	35	36–46 (42)
Pre-vitelline distance % of body- length	10–17 (13)	12	14–22 (18)
Testicular field length% of body- length	30–38 (34)	33–35	24–35 (31)
Pretesticular distance% of body-length	17–25 (22)	27	34–43 (38)
Post-uterine distance% of body-length	22–40 (30)	20	17–29 (24)