Lingulitrema, Dronen & Blend & Mohammed & Bannai, 2021

Dronen, Norman O., Blend, Charles K., Mohammed, Essa T. & Bannai, Majid, 2021, Reconsideration of the species assigned to Faustula Poche, 1926 (Digenea: Microphalloidea) with the proposal of five new genera in the Faustulidae Poche, 1926, Zootaxa 5027 (2), pp. 231-253 : 245-246

Lingulitrema n. gen.

( Fig. 9 )

Type species: Lingulitrema hilsai ( Kumar & Agarwal, 1984) n. comb. Type and only species.

(Syn. Faustula hilsai Kumar & Agarwal, 1984 )

Diagnosis: Body lingulate, anterior extremity broadens posteriorly, widest at one-quarter of distance from anterior end, gradually narrows posterior to midlevel of body to form rounded posterior end; tegument aspinose. Forebody occupies less than one-half of body length. Oral sucker described as terminal; shown as subterminal in fig. 2A of Kumar & Agarwal (1984). Ventral sucker muscular, spherical to round, anterior to midlevel of body, noticeably larger than oral sucker. Prepharynx absent. Pharynx muscular, elliptical to round. Esophagus relatively short to moderately long. Intestinal bifurcation about midway between pharynx and ventral sucker. Ceca relatively long, surpass midlevel of body posteriorly. Testes 2, entire, symmetrical, near midlevel of body. Cirrus sac claviform, lies lateral to right margin of ventral sucker, terminates some distance posterior to it; sac encloses a relatively long, tubular pars prostatica surrounded by numerous prostatic cells and somewhat saccate, laterally-placed S- shaped seminal vesicle. Genital pore postbifurcal, median to submedian (shown as distinctly submedian, near left cecum in figs. 2A & B of Kumar and Agarwal 1984), sinistral. Ovary posttesticular, slightly sinistral, 5–6 ovarian lobes. Laurer’s canal not observed. Seminal receptacle unknown. Uterus largely posterior to gonads, fills most of posttesticular space; metraterm present. Vitellarium, 1 field per side, composed of numerous follicles extensively distributed in lateral fields between midlevel of esophagus and posterior margin of ovary. Eggs small, operculate. Excretory vesicle Y-shaped, extent of excretory arms unknown; excretory pore terminal.

Etymology: The genus is named based on the tongue-shaped body of the type species (Linguli; Latin for tongue) within the faustulid trematodes (trema).

Remarks: Apparently unaware of the description of the original F. hilsai by Rizvi (1971; see fig. 3), Kumar & Agarwal (1984) described a second species which they also named F. hilsai (see figs. 2A, B, C of Kumar & Agarwal 1984). WoRMS (2021a) considers F. hilsai Kumar & Agarwal, 1984 a synonym of F. hilsai Rizvi, 1971 (both described from T. ilisha [Syn. Hilsa ilisha ] collected from Uttar Pradesh, India); however, although both F. hilsai Rizvi, 1971 and F. hilsai Kumar & Agarwal, 1984 are about the same size (1,450 ‒1,850 vs 1,300 ‒1,500 long), F. hilsai Kumar & Agarwal, 1984 differs from F. hilsai Rizvi, 1971 by having a shorter forebody (approximately 430, 29% vs 740‒910, 49‒51% of body length); the testes positioned posterior to the ventral sucker vs flanking the ventral sucker; a longer cirrus sac (340–360, 24–27% vs 190–250, 13–14%); a median ovary with 5–6 ovarian lobes vs a distinctly submedian ovary with 8 or more ovarian lobes; a somewhat larger postovarian space relative to body length (440, 32% vs 435, 24%); larger eggs (30–50 × 20–30 vs 20 × 12) and F. hilsai Kumar & Agarwal, 1984 has more extensive vitelline fields (ranging from the midlevel of the esophagus and surpassing the testes posteriorly, reaching to the level of the posterior aspect of the ovary vs ranging from about the level of the intestinal bifurcation to near the level of the posterior aspect of the testes, but not approaching the level of the ovary). We therefore consider F. hilsai Kumar & Agarwal, 1984 to be distinct from F. hilsai as originally described by Rizvi (1971). Faustula hilsai Rizvi, 1971 shares a striking similarity to F. basiri . Both have a similar body form; a long esophagus; a ventral sucker that is at the midlevel of the body providing for an unusually long forebody; a large rounded to somewhat pyriform cirrus sac lying immediately anterior to the ventral sucker, enclosing a somewhat Faustula -like cirrus apparatus with a tubular pars prostatica and convoluted seminal vesicle both surrounded by numerous large glandular cells; a similar vitellarium pattern; testes that are anterolateral to the ventral sucker; a multilobed ovary (8 or more lobes) that is a short distance posterior to the ventral sucker and slightly sinistral to the midline of the body; and both have basically equivalent measurements, morphometric ratios and morphometric percentages (see Table 1). In our opinion, F. hilsai as originally described by Rizvi (1971) should be synonymized with F. basiri . Additionally, as F. hilsai Kumar & Agarwal, 1984 is established as a species distinct from F. hilsai Rizvi, 1971 , we propose Lingulitrema to accommodate F. hilsai Kumar & Agarwal, 1984 as Lingulitrema hilsai . Lingulitrema hilsai differs from species of Faustula by having an extensively elongate, lingulate body form; an oral sucker described as terminal (appears to be slightly subterminal in fig. 2A of Kumar & Agarwal 1984); testes that are located posterior to the ventral sucker near the midlevel of the body or a little more posterior; a distinctly submedian genital pore; a relatively long, tubular pars prostatica surrounded by numerous prostatic cells and a distinctive laterally-placed, S-shaped seminal vesicle vs a short pars prostatica with few prostatic cells and a long tubular seminal vesicle that spirals through the posterior two-thirds of the cirrus sac and is at least partially embedded in numerous large glandular cells; an ovary with 5–6 lobes vs 8 or more lobes generally seen in species of Faustula and F. hilsai Kumar & Agarwal, 1984 was originally described as having a smooth (aspinose) body. It should be noted that it has been our experience that species of Faustula tend to be somewhat fragile and that the tegumental spines are easily dislodged during routine handling and/or fixation; therefore, the presence or absence of body spines may not be a reliable characteristic in some cases in this genus. It also should be noted that we cannot be completely sure that the lateral placement of the seminal vesicle is not fixation-induced.

Figures

FIGURES 9–10. Diagrammatic illustrations of faustulids (ventral views): 9. Lingulitrema hilsai (Kumar & Agarwal, 1984) n. comb. based on Kumar & Agarwal (1984); representative of Lingulitrema n. gen. 10. Varanasifaustula indica (Agarwal & Verma, 1981) n. comb. based on Agarwal & Verma (1981); representative of Varanasifaustula n. gen.