Schistorchis, Luhe, 1906

Blend, Charles K., Karar, Yasser F. M. & Dronen, Norman O., 2017, Revision of the Megaperidae Manter, 1934 n. comb. (Syn. Apocreadiidae Skrjabin, 1942) including a reorganization of the Schistorchiinae Yamaguti, 1942, Zootaxa 4358 (1), pp. 1-44 : 33-39

Genus Schistorchis sensu stricto Lühe, 1906

(Syns. Megacreadium Nagaty, 1956 ; Schistorchis [ Schistorchis ] Lühe, 1906; Schistorchis [Alloschistorchis] Yamaguti, 1970)

Diagnosis: Body elongate to sub-rectangular; maximum breadth at or posterior to mid-body level. Tegument aspinose. Eye-spot pigment present or absent. Forebody short, about 1/5 to 1/3 of body length. Pre-oral lobe present, often conspicuous. Oral sucker spherical to somewhat longitudinally elongate-oval, cellular/glandular, subterminal, large, “complex” type with circumoral muscles indented anteriorly in variant degrees, musculature localized immediately around mouth as partial U-shaped muscular sphincter half-encircling oral aperture posteroventrally. Ventral sucker pre-equatorial, spherical, smaller than oral sucker (i.e. less than 1/2 its dimensions). Prepharynx absent. Pharynx transversely oval, rarely longitudinally elongate, at times inconspicuous, weakly developed. Esophagus very short, often inconspicuous. Intestinal bifurcation in posterior 1/2 of forebody. Caeca two, wide, long, open via separate ani at posterior end of body. Testes 5−13 (11 most common) in number, arranged medially or submedially in 2−3 rows, smooth to slightly indented, sub-globular to sub-oval to irregular, separated to contiguous or nearly so, post-ovarian, in middle 1/3 of body. Post-testicular region long, occupying posterior 1/5 to 1/2 of body length. Seminal vesicle saccate, clavate to pyriform to oval, large, extends some distance into hindbody. Pars prostatica tubular to oblong, distinct, combines with distal portion of metraterm to form hermaphroditic duct which itself is short, small, and extends anterodorsal to ventral sucker. Prostatic cells well-developed, free in parenchyma. Genital atrium distinct. Genital pore median to ventro-submedian (sinistral) in forebody, either immediately anterior to ventral sucker aperture or at level close to anterior margin of sucker. Ovary spherical to elliptical, smooth, in hindbody, dextral to almost median (rarely submedian sinistral), pre-testicular and either separated from or contiguous with anteriormost testes. Canalicular seminal receptacle oval to elongate-oval, either sinistrolateral to ovary or anterior to it. Mehlis’ gland either directly lateral or anterolateral to ovary. Laurer’s canal present, opens dorsally. Vitellarium follicular; distributed anteriorly in region between testes to mid-pharynx level, runs uninterrupted within lateral to submedian regions of worm to posterior extremity, confluent in posttesticular region; follicles profuse, small or large, lateral, dorsal and ventral to caeca. Uterus pre-ovarian, intercaecal. Metraterm distinct. Eggs relatively numerous, operculate, oval. Excretory vesicle I-shaped, narrow to wide, median, extends anteriorly to level of anteriormost testes in middle 1/3 of body; primary excretory ducts (i.e. collecting tubules) cross caeca ventrally and run into forebody as far as oral sucker; excretory pore terminal. In intestine of marine teleosts ( Tetraodontiformes ) in Indian and Pacific Oceans and Red Sea.

Type-species: Schistorchis carneus Lühe, 1906 (Syns. Pleorchis oligorchis Johnston, 1913 ; Schistorchis oligorchis [ Johnston, 1913] Yamaguti, 1942).

Key to species of Schistorchis sensu stricto Lühe, 1906 a

1a. Egg size 140 × 90 µm; anterior extent of uterus to level of pharynx; two anterolateral circumoral lobes present......................................................................... Schistorchis tetrodontis ( Nagaty, 1956) n. comb. (Syn. Megacreadium tetrodontis Nagaty, 1956 ) ( Fig. 19 ).

1b. Egg size less than 90 × 55 µm; anterior extent of uterus to level of or near anterior margin of ventral sucker; single anterolateral circumoral lobe present, indented anteriorly to varying degrees............................................... 2.

2a. Ovary about 2¯3 times the testes size; seminal receptacle confined to region between ovary and ventral sucker; vitelline folli- cles large, about equal in size to testes............................. Schistorchis paruchini Kurochkin, 1974 (Fig. 20).

2b. Ovary about equal or slightly larger or smaller than testes size; seminal receptacle posterior or lateral to ovary; vitelline follicles noticeably smaller than testes....................................................................... 3.

3a. Testes arranged in either 2 or 3 rows; seminal vesicle neither encroaching nor intervening into space between ovary and ventral sucker (displaced either to right or left of ventral sucker)........................ Schistorchis skrjabini Parukhin, 1963 ( Fig. 21 from Parukhin 1963; Fig. 22 from Hafeezullah 1981).

3b. Testes arranged in 2 rows; seminal vesicle encroaching and/or intervening into space between ovary and ventral sucker............................................................................... Schistorchis carneus Lühe, 1906 (Syns. Pleorchis oligorchis Johnston, 1913 ; Schistorchis oligorchis [ Johnston, 1913] Yamaguti, 1942) ( Fig. 23 from Lühe 1906; Figs. 15–18 from present study).

a Figure(s) listed in parentheses at the end of each couplet are redrawn from the type description as indicated by the authority for each species. Where more than one authority is given or another reference is used (e.g. re-description of species), the source of the figure(s) is also indicated.

Species/ Schistorchis carneus Lühe, 1906 Schistorchis Schistorchis skrjabini Schistorchis Schistorchis carneus Feature tetrodontis Parukhin, 1963 paruchini Lühe, 1906

Nagaty, 1956 n. Kurochkin, 1974

comb.

Reference Lühe (1906) Johnston (1913) Hafeezullah Nagaty (1956) Parukhin (1963) Hafeezullah (1981) Kurochkin (1974) Present study

n = 11 n = 8–11; 1 only (1981) n = 1 n = 8 n = 6 n = 1 n = 18

fully measured n = 2; both

contracted

Host(s) Arothron stellatus Arothron hispidus Arothron hispidus Tetrodon sp. Triacanthus Triacanthus Meuschenia Arothron hispidus (Anonymous) (Linnaeus) (Linnaeus) [Puffer sp.] biaculeatus biaculeatus (Bloch) australis (Linnaeus) [White- (= Tetrodon (= Tetrodon hispidus (= Tetrodon (Tetraodontidae) (Bloch) (= Triacanthus (Donovan) spotted puffer]

stellatus Linnaeus ) [White- hispidus (= Triacanthus brevirostris [Bloch]) (= Navodon (Tetraodontidae) Anonymous) spotted puffer] Linnaeus) [White- brevirostris [Short-nosed australis

[Stellate puffer] ( Tetraodontidae ) spotted puffer] [Bloch]) [Short- tripodfish] [Donovan])

( Tetraodontidae ) ( Tetraodontidae ) nosed tripodfish] ( Triacanthidae ) [Southern

( Triacanthidae ) leatherjacket]

& Abalistes (Monacanthidae)

stellaris (Bloch

& Schneider)

[Starry

triggerfish]

( Balistidae )

Locality Off South Off Queensland, Off Mandapam, Off Ghardaga / Off Vietnam in Off Vellar Estuary at Off Great Off Sharm El-Naga, Modragam Paar, Australia Gulf of Manaar, Hurghada, Egypt South China Sea Parangipettai Australian Bight Makadi Bay, Southern Ceylon Pearl Sri Lanka in Red Sea (=Porto Novo), Hurghada & off Safaga, Banks, Gulf of Coromandal Coast, Egypt, in Red Sea Manaar, Sri Lanka Bay of Bengal

Site of infection Stomach Intestine Intestine Intestine Intestine Intestine Intestine Lower & Mid-Intestine Body length (L) 10,000−15,000 5,000−12,000 5,596−6,000 13,500 2,000−2,300 1,925−6,682 2,900 8,897 (7,160 −11,960) a Body width (W) 4,000−6,000 2,000−5,000 2,076−3,052 4,700 680−860 536−1,966 1,120 3,908 (3,201 −5,140)

Body W % a 40.0% b 40.0%–41.7% b 37.1%−50.9% b 34.8% b 34.0%−37.4% b 27.8%−29.4% b 38.6% b 44.6%

(37.7%–56.7%) Forebody (FB) L --- --- 1,366 c 3,046 b,c --- 756 −1,058 1,009 c 1,749 (1,445 –2,700)

FB L % a 21.8%–30.0% c 21.0% c 25.1% c 22.6% b,c 23.5% c 15.8−39.3% b 34.8% b,c 19.9%

(14.3%–24.9%)

Oral sucker (OS) L cf. 2,000 −2,500 cf. 1,666 1,207 c 1,800 b,c 280−340 292 c 708 c 1,375 (1,131 –1,760)

OS L % a 14.3%–16.9% c 16.0% c 22.2% c 13.4% b,c 14.0%−14.8% b 15.8% c 24.4% b,c 15.8%

(10.8%–19.0%)

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Species/ Schistorchis carneus Lühe, 1906 Schistorchis Schistorchis skrjabini Schistorchis Schistorchis carneus

Feature tetrodontis Parukhin, 1963 paruchini Lühe, 1906

Nagaty, 1956 n. Kurochkin, 1974

comb.

Reference Lühe (1906) Johnston (1913) Hafeezullah Nagaty (1956) Parukhin (1963) Hafeezullah (1981) Kurochkin (1974) Present study

n = 11 n = 8–11; 1 only (1981) n = 1 n = 8 n = 6 n = 1 n = 18

fully measured n = 2; both

contracted

VS to OV L --- --- 173 c 144 b,c --- 50 c 92 c 475 (163–1,460)

VS to OV L % a 3.0%−6.4% c 2.2% c 3.2% c 1.1% b,c 0.8% c 2.7% c 3.2% b,c 5.2% (2.2%–15.0%)

VS to closest testis L --- --- 405 c 1,015 b,c --- 118 c 231 c 761 (334–1,860)

VS to closest testis L 7.3%–10.6% c 10.2% c 7.6% c 7.5% b,c 3.8% c 6.4% c 8.0% b,c 8.5% (4.5%–19.1%)

%a

Seminal receptacle --- --- 245 c --- --- 56 c 119 c 539 (308–760) [n=15]

(SR) L

SR W --- --- 360 c --- --- 58 c 110 413 (240–590) [n=15]

Testes (T) number 11 (5 left & 6 11 (5 left & 6 right) 11 (5 left & 6 8 (3 left & 5 11 (5 left, 2 11 (5 left, 2 median 11 (3 left, 2 median 11 (5 left & 6 right) right) [n=9]; 8 (3 left & 5 right) c right) median & 4 & 4 right); 11 (5 left & 6 right) [n=16]; 10 (5 left & 5 right) [n=1]; 5 (2 right) & 6 right) c right) [n=1]; 7 (2 left & left & 3 right) [n=1] 5 right) [n=1]

T L --- cf. 476 206−330 426-635 b,c 32−180 133−172 c 60−100 453 (326–664)

T L % a 4.7%–5.5% c 3.7%−4.5% c 3.7%−5.5% b 3.2%−4.7% b,c 1.6%−7.8% b 7.2%–9.3% c 2.1%−3.4% b 5.2% (3.7%–6.4%)

T W 600−1,000 d 476 206−316 400−600 20−120 96−550 60−100 580 (425–1,038)

T:OV L ratio 1:0.59−1.04 c 1:01.25−1.51 c 1:1.25−1.53 b 1:0.79−1.17 b,c 1:0.67−3.00 b 1:0.48–0.63 c 1:2.10−3.50 b 1:1.15 (1:0.91–1.64)

T:OV W ratio cf. 1:1.00 b,d 1:1.20 b 1:1.04−1.47 b 1:0.84−1.27 b,c 1:1.17−5.00 b 1:0.67−1.00 b 1:1.80−3.00 b 1:0.97 (1:0.44–1.44)

Seminal vesicle --- --- 926 c 1,000 280 181 c 200 781 (608–1,280)

(SV) L

SV L % a 10.1%−13.5% c 5.5% c 17.0% c 7.4% b 12.2%−14.0% b 9.8% c 6.9% b 9.0% (5.5%–13.6%)

SV W --- --- 220 c 600 100 111 c 80 511 (312–696)

Pars prostatica L --- --- 238 c --- --- 48 c --- 651 (422–964) [n=14]

Hermaphroditic --- 240 167 c --- --- 20 c --- 304 (213–440) [n=14]

duct L

Pars prostatica: 1:1.61−1.69 c 1:1.98 c 1:0.70 c --- --- 1:0.42 c --- 1:0.48 (1:0.28–0.69)

Hermaphroditic duct [n=14]

L ratio

Pre-oral L --- --- 73 c 180 b,c --- 27 c 85 c 141 (0–248)

Pre-oral L % a 2.8%–6.4% c 2.9% c 1.2%–1.3% b,c 1.3% b,c 3.2% c 1.5% c 2.9% b,c 1.7% (0.0%–3.5%) ……continued on the next page

Figures

FIGURES 19¯20. Schistorchis tetrodontis (Nagaty, 1956) n. comb. and Schistorchis. paruchini Kurochkin, 1974. 19. S. tetrodontis ventral view of adult redrawn from Nagaty (1956, Fig. 2). 20. S. paruchini ventral view of adult redrawn from Kurochkin (1974, p. 67). Abbreviations: An, Anus; Ce, Cecum; EP, Excretory pore; GP, Genital pore; MG, Mehlis’ gland; OS, Oral sucker; Ov, Ovary; Ph, Pharynx; SR, Seminal receptacle; SV, Seminal vesicle; Te, Testes; Ut, Uterus; VD, Vitelline duct; VF, Vitelline follicles; VS, Ventral sucker.

FIGURES 21¯22. Schistorchis skrjabini Parukhin, 1963. 21. S. skrjabini dorsal view of adult redrawn from Parukhin (1963, Fig. 1). 22. S. skrjabini ventral view of adult redrawn from Hafeezullah (1981, Fig. 4). Abbreviations: An, Anus; Ce, Cecum; GP, Genital pore; MG, Mehlis’ gland; Oo, Oötype; OS, Oral sucker; Ov, Ovary; Ph, Pharynx; PP, Pars prostatica; SR, Seminal receptacle; SV, Seminal vesicle; Te, Testes; Ut, Uterus; VD, Vitelline duct; VF, Vitelline follicles; VR, Vitelline reservoir; VS, Ventral sucker.

FIGURE 23. Schistorchis carneus Lühe, 1906. Ventral view of adult redrawn from Lühe (1906, Fig. 11). Abbreviations: Ce, Cecum; EA, Excretory arm/duct; EP, Excretory pore; EV, Excretory vesicle; GP, Genital pore; HD, Hermaphroditic duct; MG, Mehlis’ gland; OS, Oral sucker; Ov, Ovary; Ph, Pharynx; PP, Pars prostatica; SR, Seminal receptacle; SV, Seminal vesicle; Te, Testes; Ut, Uterus; VD, Vitelline duct; VF, Vitelline follicles; VS, Ventral sucker.

FIGURES 15–18. Schistorchis carneus Lühe, 1906 (Megaperidae n. comb.: Schistorchiinae) from the white-spotted puffer, Arothron hispidus (Linnaeus) (Tetraodontidae), from the Red Sea off Egypt. 15. Composite of whole adult specimen, ventral view. 16. Composite of terminal genitalia, ventral view. 17. Composite of proximal female complex, ventral view. 18. Hindbody revealing anterior extent of excretory vesicle and termination of caeca, ventral view. Abbreviations: An, Anus; EA, Excretory arm/duct; Eg, Eggs; EP, Excretory pore; EV, Excretory vesicle; GP, Genital pore; LIC, Left intestinal cecum; Me, Metraterm; MG, Mehlis’ gland; OD, Ovarian duct; Oo, Oötype; OS, Oral sucker; Ov, Ovary; PC, Prostatic cells; Ph, Pharynx; PP, Pars prostatica; RIC, Right intestinal cecum; SR, Seminal receptacle; SV, Seminal vesicle; Te, Testes; Ut, Uterus; VD, Vitelline duct; VF, Vitelline follicles; VR, Vitelline reservoir; VS, Ventral sucker.