Stephanostomum talakitok n. sp. (Digenea: Acanthocolpidae) from the golden trevalley, Gnathanodon speciosus (Perciformes: Carangidae), from Ningaloo Reef, Western Australia Author Bray, Rodney A. Department of Zoology, Natural History Museum, Cromwell Road, London SW 7 5 BD, UK, email: rab @ nhm. ac. uk Centre for Marine Studies and Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland 4074, Australia, email: t. cribb @ uq. edu. au Author Cribb, Thomas H. text Zootaxa 2006 2006-01-05 1104 1 59 68 https://biotaxa.org/Zootaxa/article/view/zootaxa.1104.1.5 journal article 10.11646/zootaxa.1104.1.5 1175­5334 5057663 58BE4677-D010-4239-851F-79ECBBC885C2 Stephanostomum talakitok n. sp. ( Figs 1 –3) Type­host: Gnathanodon speciosus (Forsskål) , Carangidae ; golden trevally. Site: Intestine. Type­locality: Ningaloo Coral Reef , Western Australia ( 22°42S , 113°40E , April, 2000) . Prevalence: 1 of 1 (100%). Intensity: 22. Deposition of specimens: holotype QM G223027 , paratypes QM G223028–223040 , BMNH 2005.10 .28.1–7. Etymology: Talakitok is a Philippine vernacular name for the host­species. Description (Based on 21 whole­mount preparations). Measurements and ratios in Table 1 . Body elongate, narrow, widest in region of testes ( Figure 1 ). Tegument spinous, unarmed patch immediately posterior to oral sucker, spines large and densely packed in forebody, smaller in hindbody, becoming sparse in hindbody, only detectable to level of ovary. Oral sucker terminal, distinctly wider than long. Circum­oral spines in double ring, without distinct ventral hiatus; spines decrease in size markedly towards ventral median line; mid­ventral spine small, pointed ( Figure 2 ). Ventral sucker oval, in anterior third of body. Prepharynx long. Pharynx pyriform. Oesophagus distinct. Intestinal bifurcation in extreme posterior forebody or at level of anterior margin of ventral sucker. Caeca long, narrow, form uroproct. FIGURES 1–3. Stephanostomum talakitok n. sp. 1. Ventral view of holotype, with uterus and cirrus­sac in outline only. 2. Anterior extremity showing circum­oral and body spines. 3. Terminal genitalia, lateral view. Abbreviations: ej, ejaculatory duct; pp, pars prostatica; sv, seminal vesicle. Scale­bars: 1, 1mm; 2, 3, 200 µ m. TABLE 1. Dimensions of Stephanostomum talakitok n. sp.

Measurement, count or ratio descriptor	Measurement, count or ratio
Overall dimensions	2,962–4,437 (3,707)
Width as % of length	8.6–11.2 (10.2) %
Body­spines: anterior mid­ventral	16–18 long
Body­spines: longest	31–32 long
Oral sucker	65–115 × 169–209 (89 × 186)
Oral sucker length as % of body­length	1.9–3.0 (2.4) %
Circum­oral spine counts	34–40 (36)
Circum­oral spines: antero­ventral	18–30 (23)
Circum­oral spines: postero­ventral	14–28 (21)
Circum­oral spines: antero­dorsal	39–62 (52)
Circum­oral spines: postero­dorsal	36–57 (48)
Ventral sucker (VS)	135–190 × 125–183 (161 × 151)
VS length as % of body­length	3.9–5.0 (4.4) %
Sucker­length ratio	1:1.3–2.2 (1.8)
Sucker­width ratio	1:0.74–0.92 (0.81)
Forebody	783–1,146 (957) long
Forebody as % of body­length	23.5–29.7 (25.8) %
Hindbody (HB)	2,044–3,105 (2,590) long
Hindbody as % of body­length	66.5–72.2 (69.8) %
Prepharynx	422–764 (574) long
Prepharynx length as % of body­length	12.1–19.8 (15.5) %
Pharynx	156–198 × 94–159 (178 × 126)
Pharynx length as % of body­length	4.4–5.4 (4.8) %
Oesophagus	45–140 (86) long
Intestinal bifurcation to ventral sucker	0–37 (23)
Anterior testis	384–645 × 154–250 (492 × 204)
Anterior testis as % of body­length	12.0–14.5 (13.3) %
Posterior testis	404–609 × 182–234 (543 × 215)
Posterior testis as % of body­length	13.3–17.0 (14.7)%
Distance between testes (DBT)	0
DBT as % of body­length	0 %
Post­testicular region (PTR)	138–294 (223)
PTR as % of body­length	4.6–7.6 (6.0) %
Cirrus­sac (CS)	694–1,290 × 91–126 (1,101 × 108)

......continued on the next page TABLE 1 (continued)

Measurement, count or ratio descriptor	Measurement, count or ratio
Cirrus­sac length as % of body­length	23.1–34.1 (29.7) %
Distance from anterior end of CS to VS	Anterior end of CS always dorsal to VS
Distance from posterior end of CS to VS	507–857 (727)
Above dimension as % of VS to Ovary	56.0–76.3 (65.6) %
Length of internal male duct	777–1,344 (1,171)
Seminal vesicle (SV)	295–721 (599) long
SV as % of internal male duct	37.9–56.7 (50.8) %
Pars prostatica (PP)	181–322 (261) long
PP as % of internal male duct	15.3–27.9 (22.4) %
Ejaculatory duct (EJ)	242–364 (311)
EJ as % of internal male duct	23.0–34.2 (26.8) %
Genital atrium	13–125 (61) long
Ovary	139–226 × 108–150 (185 × 126)
Ovary length as % of body length	4.6–5.5 (5.0)%
Ovary to ventral sucker (Ov­VS)	890–1,308 (1,112)
Ov­VS as % of body­length	27.5–32.1 (30.0) %
Ovary to anterior testis (Ov­AT)	0 (11 specimens), 5 (1), 91 (1)
Ov­AT as % of body­length	0 (11 specimens), 0.1 (1), 2.0 (1) %
Eggs	52–68 × 31–46 (63 × 38)
Anterior limit of vitellarium to VS	294–494 (372)
Above dimension as % of HB­length	9.8–17.0 (14.4) %

Testes 2, oval, entire, tandem, contiguous. Post­testicular region short. Cirrus­sac elongate, coiled ( Figure 3 ), reaches well into hindbody; anterior extremity dorsal to ventral sucker. Seminal vesicle saccular, oval, undivided, often coiled anteriorly. Pars prostatica long, narrower distally, lined with anuclear cell­like bodies, surrounded by gland­cells. Ejaculatory duct long, wide, lined with closely packed small cupolas, with round bases seen as circles on wall of duct, with distinct naked region distally. Genital atrium short, never reaching into hindbody. Genital pore median, slit­like, immediately anterior to ventral sucker. Ovary oval, entire, almost always contiguous with anterior testis, occasionally slightly separated. Mehlis' gland antero­dorsal to ovary. Laurer's canal opens dorsally in region of ovary. Uterine seminal receptacle in proximal uterus. Uterus narrow, intercaecal, preovarian. Eggs large, tanned operculate. Metraterm slightly shorter than cirrus­sac, lining unarmed. Vitellarium follicular, overlaps posterior end of cirrus­sac; fields confluent ventrally and dorsally to uterus, lateral to and slightly overlaps gonads, confluent dorsally and ventrally in post­testicular region. Excretory pore terminal. Anterior extent of vesicle not detected, even in immature specimens.