Laiogonimus tananarivensis ( Deblock & Capron, 1962 ) Fischthal & Thomas, 1968

Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, Zootaxa 5284 (3), pp. 445-495 : 461-463

Laiogonimus tananarivensis ( Deblock & Capron, 1962) Fischthal & Thomas, 1968

( Figs. 14–16 )

(Syns. Astiotrema [Biguetrema] tananarivense Deblock & Capron, 1962 ; Astiotrema tananarivense Deblock & Capron, 1962 ; Laiogonimus vercammengrandjeani Meskal, 1970 n. syn.)

Records. 1. Deblock & Capron (1962); 2. Meskal (1970).

Remarks. Biguetrema was erected by Deblock & Capron (1962) as a subgenus within Astiotrema for the type species Astiotrema (Biguetrema) tananarivense to accommodate specimens collected from the intestine of the Mascarene grass or ridged frog, Ptychadena mascareniensis (Duméril & Bibron) (syn. Rana mascareniensis Duméril & Bibron ) ( Anura : Ptychadenidae ) (type-host), Goudot’s bright-eyed frog, Boophis goudotii Tschudi (Syn. Rhacophorus goudoti Tschudi ) ( Anura : Mantellidae ), and from an unidentified shrub frog, Rhacophorus sp. ( Anura : Rhacophoridae ), from Madagascar. Deblock & Capron (1962) stated that their specimens were morphologically similar to members of Astiotrema except in having four distinct features, the combination of which has not been reported before in Astiotrema or in the closely-related taxa Haplometra Looss, 1899 , Glossidium , Alloglossidium Simer, 1929 , Styphlodora Looss, 1899 , and Paurophyllum Byrd, Parker & Reiber, 1940 . These four features were (i) a cirrus-pouch that extends within the forebody obliquely from the anterior margin of the ventral sucker, (ii) a seminal vesicle folded over itself followed by a spherical pars prostatica, (iii) a pre-bifurcal, sinistral genital pore, and (iv) lateral, mostly extracecal vitellarium composed of 6 to 12 voluminous, massive follicles. In addition, due to the report of Astiotrema trituri Grabda, 1959 (= Neoastiotrema trituri [Grabda, 1959] Tkach, 2008) by Grabda (1959a, 1959b) from an amphibian (i.e., L. vulgaris – see above), Deblock & Capron (1962) erected Biguetrema as a subgenus within Astiotrema . Fischthal & Thomas (1968) excluded A. (B.) tananarivense from Astiotrema and combined it within Laiogonimus as the second recorded species, L. tananarivensis , characterizing it by having testes not completely surrounded by the uterus, a seminal vesicle with one loop, and the oral sucker smaller than the ventral one. Meskal (1970) revised A. (B.) tananarivense and referred to conspicuous differences distinguishing it from Astiotrema in several respects: (i) possessing a cirrus-pouch that does not surpass the level of the mid-ventral sucker posteriorly vs a cirrus-pouch in Astiotrema which extends into the hindbody, reaching the ovarian level posteriorly; (ii) having a distinctly submedian to nearly submarginal genital pore whereas Astiotrema has a median to slightly submedian genital pore; (iii) the cirrus-pouch in A. (B.) tananarivense contains a winding to convoluted seminal vesicle vs a unipartite sacciform one in Astiotrema ; and (iv) an ovary much closer to the ventral sucker than the anterior testis in A. (B.) tananarivense while the ovary is mid-way between the ventral sucker and anterior testis in taxa of Astiotrema . Based on those differential characteristics, Meskal (1970) adopted A. (B.) tananarivense within Laiogonimus , concurring with Fischthal & Thomas (1968) regarding their combination L. tananarivensis . Yamaguti (1971) followed the same approach and synonymized the subgenus, Biguetrema, within Laiogonimus based on their similarities in morphology, host group (anuran amphibians) and locality (both taxa are from Africa, specifically Madagascar and Lake Kivu on the border between the Democratic Republic of the Congo and Rwanda) (see Vercammen-Grandjean 1960; Deblock & Capron 1962). Dhar (1977) considered this species to belong within Astiotrema (i.e., A. tananarivense ), apparently unaware of the synonymy within Laiogonimus . We support the placement of A. (B.) tananarivense within Laiogonimus as L. tananarivensis based on previously explained morphological features and host-parasite data, in addition to the distinctive nature of the vitellarium observed in L. tananarivensis : vitellarium consists of large follicles distributed in two lateral, mostly extra-cecal groups of 6 to 12 follicles per row, extending along ceca between ventral sucker and posterior testis; vitelline follicle numbers usually higher in the left group compared to the right one, while follicle number on the right side varies more than that on the left (see Deblock & Capron 1962).

Meskal (1970) described the third species within Laiogonimus , L. vercammengrandjeani , for specimens gathered from the small intestine, occasionally rectum, of some anuran amphibians in Ethiopia: the Mascarene grass or ridged frog, P. mascareniensis ; the Erlanger’s grassland frog, Ptychadena erlangeri (Ahl) ( Anura : Ptychadenidae ); Natal dwarf puddle frog, Phrynobatrachus natalensis (Smith) ( Anura : Phrynobatrachidae ); and Angola river frog or common river frog, Amietia angolensis (Bocage) (syn. Rana angolensis Bocage ) ( Anura : Pyxicephalidae ). Laiogonimus vercammengrandjeani was distinguished from L. tananarivensis by possessing an esophagus shorter than the pharynx, slightly larger egg size (30.0–32.8; 31.3 × 12.5 µm in L. vercammengrandjeani v s 24.0 –28.0; 24.5 × 15.0–18.0; 15.5 µm in L. tananarivensis ), slightly smaller suckers ratio (1: 1.20–1.30 in L. vercammengrandjeani v s 1: 1.43 in L. tananarivensis ) and shorter body length (1,350–1,700; 1,508 µm in L. vercammengrandjeani vs 2,99 – 3,800; 3,440 µm in L. tananarivensis ). We believe these variations represent slight allometric changes which can be attributed to one or a combination of several factors, in particular, maturity of the worm, degree of contraction and flattening of the sample(s), fixation-induced variation, host induced variability (i.e., slight difference in egg size) and different treatments of the specimens such as dehydration and staining methods. Accordingly, with given morphological and morphometric measurements, the same host ( P. mascareniensis ), close morpho and nearby localities in Africa ( Ethiopia vs Madagascar); we consider L. vercammengrandjeani a synonym of L. tananarivensis .

Figures

FIGURES 14–16. Intra-specific variation observed in Laiogonimus tananarivensis (Deblock & Capron, 1962) Fischthal & Thomas, 1968. 14. L. tananarivensis (syn. Astiotrema [Biguetrema] tananarivense Deblock & Capron, 1962), ventral view, redrawn from Deblock & Capron (1962, fig. 1). 15. L. tananarivensis (syn. A. [B.] tananarivense), ventral view, redrawn from Deblock & Capron (1962, fig. 2). 16. L. tananarivensis (syn. Laiogonimus vercammengrandjeani Meskal, 1970), ventral view, redrawn from Meskal (1970, fig. 11). Abbreviations:AT, anterior testis; BS, body spines; Ce, cecum; CP, cirrus-pouch; ED, ejaculatory duct; EG, esophageal glands; EP, excretory pore; Es, esophagus; EV, excretory vesicle; GP, genital pore; Me, metraterm; MG, Mehlis’ gland; OC, ôtype complex; OS, oral sucker; Ov, ovary; Ph, pharynx; Pr.Ph, Prepharynx; PP, pars prostatica; PT, posterior testis; SR, seminal receptacle; SV, seminal vesicle; Ut, uterus; VD, vitelline duct; VF, vitelline follicle; VR, vitelline reservoir; VS, ventral sucker. Scale bars: Fig. 14 = 500 µm; Fig. 15 = 1,000 µm; Fig. 16 = 500 µm.