Flagellotrema amphitrite, Hall, Kathryn A. & Cribb, Thomas H., 2008

Hall, Kathryn A. & Cribb, Thomas H., 2008, Revision of Flagellotrema Ozaki, 1936 (Digenea, Gyliauchenidae Fukui, 1929), including the description of two species from acanthuroid fishes from the Great Barrier Reef, Queensland, Australia, Zootaxa 1718, pp. 1-35 : 9-12

Flagellotrema amphitrite n. sp.

( Fig. 3 )

Type-host: Prionurus maculatus Ogilby, 1887 , Acanthuridae ; yellowspotted sawtail.

Site: intestine.

Type-locality: Heron Island, Great Barrier Reef, Queensland, Australia (23°27'S 151°55'E)

Prevalence: Total prevalence (P. m a c u l a t u s, Heron Island) 1 of 1 (100%).

Intensity: Data not recorded.

Deposition of specimens: Holotype QM G222219 (coll. C.B. Chambers, 16 Feb. 1999); paratypes QM G222220–222222 (coll. C.B. Chambers, 16 Feb. 1999).

Etymology: This species is named after Amphitrite , the Greek goddess of the sea. Amphitrite was believed to be a nereid and, as the wife of Poseidon, was the Queen of the Sea.

Description. Based on 33 (17 mature and 16 immature) specimens. Measurements in Table 3 . Body elongate, fusiform, distinctly curved dorsoventrally; pale orange in life. Tegument smooth. Ventral sucker round, posterior, not ventrosubterminal. Pharynx pyriform, ventrosubterminal, larger than ventral sucker; fleshy preoral lip, prominent, massive. Oesophagus long, with 2 loops in figure-8 formation ( Fig. 3 ); first loop anticlockwise, crosses midline; second loop clockwise, immediately anterior to first loop; posterior thick-walled chamber absent; invested with glands along entire length. Oesophageal bulb well-developed, spheroid, smaller than pharynx, approximately half length of ventral sucker. Intestinal bifurcation immediately posterior to oesophageal bulb; caeca 2, blind, occupy approximately 1/4 of body length; gastrodermis very thick.

Testes 2, entire, ovoid, diagonal, in posterior 1/3 of body, sometimes contiguous in mature specimens. Cirrus-sac encased in muscular capsule. Seminal vesicle partially external to cirrus-sac, bipartite; anterior portion globular, internal to cirrus-sac, connected to posterior portion via short, narrow duct, surrounded by muscular capsule contiguous with cirrus-sac; posterior portion elongate, external to cirrus-sac. Va s a e ff eren t ia arise ventromedially from testis, proceed anteriorly, unite to form vas deferens, which swells immediately into seminal vesicle. Pars prostatica large, cylindrical; prostate gland cells external to cirrus-sac, very dense. Cirrus-sac prominent, median, generally posterior to caeca, sometimes overlapping posterior margin, globular; ejaculatory duct long, convoluted within cirrus-sac, with distal expansion, eversible. Genital atrium large, regular, with cilia-like lining. Genital pore, round, at level of termination of caeca.

Ovary entire, generally intertesticular, dextral, not contiguous with testes; oviduct associated with swollen insemination chamber. Canalicular seminal receptacle prominent, saccular, posterodorsal to ovary. Mehlis’ gland anterodorsal to ovary, overlies ootype. Laurer’s canal proceeds anterodorsal from intersection of oviduct and seminal receptacle, exits immediately anterodorsal to ovary. Ootype anterior to ovary. Uterus entirely pre-ovarian, coiled in median field. Opening of uterus unspecialised, enters genital atrium sinistral to cirrussac. Vitellarium follicular; follicles restricted from level of oesophagus to immediately anterior to testes, form distinctive X-shaped distribution in ventral field, dorsal field resticted to intercaecal field; vitelline ducts proceed posterolateral from termination of fields, unite in midline to form subtriangular vitelline reservoir immediately sinistrodorsal to ovary. Eggs large, tanned, operculate, apparently unembryonated in utero.

Excretory vesicle elongate, saccular. Excretory pore subterminal, opens on prominent, large papilla. Primary collecting ducts arise anterolaterally. Lymph system not observed.

Footnotes: α number of specimens measured, β all ratios are calculated to 2 decimal places.

Molecular data. Sequence data was obtained from 1 specimen for 2 genes: Specimen 1 ( P. maculatus, Heron Island): ITS2 rDNA, 28S rDNA (D1–D3). GenBank accession numbers are in Table 1 .

Comments. Flagellotrema amphitrite is readily distinguished from F. convolutum by the size and shape of the pharynx and the coiling pattern of the oesophagus. The pharynx of F. amphitrite is strongly pyriform and is massive, and much larger than the oesophageal bulb. In contrast, the pharynx of F. convolutum is generally barrel-shaped, although in 1 voucher specimen the pharynx is distinctly pyriform, and only slightly larger than the oesophageal bulb. The oesophagus of F. amphitrite forms a figure-8 coil in the anterior third of the body. This double looping formation is not seen in F. convolutum ; the oesophagus of F. convolutum executes only 1 clockwise loop. Despite the morphological differences between the 2 species, membership of this new species to Flagellotrema is supported by the posterior position of the cirrus-sac, which is almost entirely posterior to the caeca. In some specimens of F. amphitrite , the genital pore lies between the ends of the caeca, however, the position is more posterior than in species of the morphologically similar genus Gyliauchen. Further, in both F. convolutum and F. amphitrite , the ovary is intertesticular. The systematic position of F. amphitrite is further supported by the possession of a prominent excretory papilla in both species here attributed to Flagellotrema . The genus is united by the shared position of the cirrus-sac largely posterior to the caeca, presence of a prominent excretory papilla and the position of the ventral sucker, which although posterior, is not entirely ventrosubterminal.

Figures

FIGURE 3. Flagellotrema amphitrite n. sp. from Prionurus maculatus, Heron Island, Great Barrier Reef, Australia. Holotype. Scale bar = 500 µm.

Tables

TABLE 3. Measurements of Flagellotrema amphitrite n. sp. All measurements are of laterally mounted specimens and are presented in micrometres (µm).

		All specimens			Mature specimens
Variable	n α	Mean Min	Max	n	Mean Min Max
body length	33	1431 592	2768	17	1823 1104 2768
body width	33	401 144	800	17	523 320 800
pharynx length	33	194 77	437	17	257 109 437
pharynx width	33	142 71	263	17	177 116 263
oesophageal bulb length	33	122 64	205	17	143 109 205
oesophageal bulb width	33	141 71	212	17	164 116 212
ventral sucker length	33	232 154	327	17	255 212 327
ventral sucker width	33	206 116	321	17	236 186 321
oesophagus length	32	789 272	1395	16	974 714 1395
caeca length	32	294 141	533	16	360 205 533
length from pharynx to oesophageal bulb	33	287 135	533	17	351 231 533
length from oesophageal bulb to ventral sucker	33	529 173	995	17	672 334 995
anterior testis length	28	130 51	257	15	156 116 257
anterior testis width	28	147 58	250	15	172 109 250
posterior testis length	29	128 51	218	15	152 71 218
posterior testis width	29	139 45	250	15	167 71 250
ovary length	21	100 32	180	16	115 64 180
ovary width	20	105 45	186	15	119 64 186
seminal receptacle length	19	107 39	180	14	120 71 180
seminal receptacle width	14	77 39	103	9	82 58 103
cirrus-sac length	22	200 128	321	13	221 128 321
cirrus-sac width	22	126 77	250	13	153 90 250
egg length	17	70 61	77	17	70 61 77
egg width	17	41 35	51	17	41 35 51
papilla length	22	104 6	315	12	170 35 315
ratio β of pharynx to oesophageal bulb (length)	33	1.52 1.00	2.44	17	1.75 1.00 2.44
ratio of pharynx to ventral sucker (length)	33	0.80 0.44	1.40	17	0.99 0.44 1.40
ratio of oesophageal bulb to ventral sucker (length)	33	0.52 0.42	0.64	17	0.56 0.44 0.64
ratio of caeca to body (length)	32	0.21 0.16	0.29	16	0.20 0.16 0.25