Temnocephala monticellii, León & Rudolph & Volonterio, 2020

León, Rodrigo Ponce De, Rudolph, Erich H. & Volonterio, Odile, 2020, On a new Temnocephala (Platyhelminthes) from Southern Patagonia (Chile, Argentina), with a redescription of T. chilensis and some systematic and biogeographical insights *, Zootaxa 4852 (3), pp. 383-395 : 385-388

Temnocephala monticellii n. sp. Ponce de León, Rudolph & Volonterio

( Figs. 1–2 ; Tables I, II)

Material studied. Twenty-three whole mounts, 24 dissections of the reproductive complex and mounts of 11 eggs made with material found on Aegla alacalufi Jara and López, 1981 ( Decapoda, Anomura , Aeglidae ) from Burritos River (43°24’S; 72°21’W), Palena Province, X Región (also known as ‘Región de los Lagos’), Chile (coll. Erich Rudolph, 21 January, 1999).

Holotype. Whole mount, deposited in the CHFC (Universidad de la República), Montevideo, Uruguay ( CHFC / AP 11511 ).

Paratypes. Whole mounts ( CHFC / AP 11512–11534 ), mounts of dissections of the reproductive complex ( CHFC / AP 11535–11558 ) and eggs ( CHFC / AP 11559 ), deposited in the CHFC (Universidad de la República), Montevideo, Uruguay .

Etymology. The specific epithet is given in honor of the late Professor Dr. Francesco Saverio Monticelli (1863- 1928), for his pioneer contribution to the systematics and taxonomy of Neotropical temnocephalans.

Description. Body length excluding length of tentacles 1,285.7 µm (Table I). Maximum width 960.9 µm, at level of anterior testes ( Fig. 1A ). Eyes red. Eight Haswell cells. Circular sucker, diameter 405.4 µm; sucker peduncle diameter 245.8 µm. Abundant sucker glands at level of posterior testes. Ratio total body length to sucker diameter 3.2:1 (Table II). Paranephrocyte pattern: 4 large cells at level of testes; a pair located close to posterior region of anterior testes, and another pair close to posterior region of posterior testes ( Fig. 1A ). Oval pharynx; longitudinal axis 327.2 µm, transverse axis 432.0 µm; posterior sphincter larger than the anterior one, and a wide pharyngeal lumen. Intestinal sac with 4–5 lateral folds, usually forked distally.

TABLE I. Ranges, standard deviations (SD) and sample sizes of the measurements of Temnocephala monticellii n. sp. whose means are provided in the text. All measurements are given in micrometers.

Testes elliptical, anterior testes length 149.5 µm, width 117.7 µm. Posterior testes length 232.8 µm, width 157.9 µm. Seminal vesicle length 128.7 µm, width 60.5 µm, joined to contractile vesicle polarly ( Fig. 1B ). Contractile vesicle length 87.4 µm, width 75.7 µm. Penial stylet total length 185.6 µm, basal width of the shaft 60.1 µm, distal width of the shaft 18.3 µm, frequently with a sub-distal swelling 23.9 µm in width ( Fig. 2A ). Introvert length 35.0 µm, width 31.8 µm, with at least 54 symmetrical spine-like projections ( Fig. 2B ). Each spine-like projection with 6–7 internal spines. More proximal internal spines increasingly longer ( Fig. 2A ). Ratio penial stylet length to basal width 3.3:1, penial stylet length to contractile vesicle length 2.4:1, non-everted introvert diameter to penial stylet basal width 0.5:1.

Ovary length 115.6 µm, width 83.9 µm. Vagina muscularized, with symmetrical distal sphincter ( Fig. 1B ). Seminal receptacle diameter 19.4 µm; resorbens vesicle diameter 134.8 µm. Glandular cells surrounding the proximal end of the vagina, with ducts that open into its lumen ( Fig. 1B ). Eggs elliptical and devoid of a polar filament ( Fig. 2C ), pedunculated, deposited on coxal region and between eyes of host; egg length 558.4 µm, width 330.8 µm.

Remarks. Among the species of Temnocephala hosted in Aegla , only T. monticellii n. sp., T. chilensis and T. dionii share a very wide introvert more than 20 µm in diameter and with spines of different size. The everted and non-everted introverts of T. monticellii n. sp. and T. chilensis have a somewhat similar shape, but in T. chilensis the introvert is clearly asymmetrical in both the everted and non-everted conditions, with the spines on the longer side of the introvert being longer than those on the shorter side (see description of T. chilensis below), whereas in T. monticellii n. sp. both introvert and spines are symmetrical around the longitudinal axis of the former ( Fig. 2 A–B). Temnocephala monticellii n. sp differs from T. dionii in that the latter has a groove between the shaft and the introvert of the penial stylet, whereas in specimens of the former the shaft narrows gradually for most of its length and then usually expands sub-distally forming a swelling that encompasses the distal portion of the shaft and the proximal portion of the introvert ( Fig. 2A ). Furthermore, in the eggs of T. chilensis and T. dionii there is a sub-polar filament which is absent in T. monticellii n. sp. The new species results morphologically similar with part of the material studied by Wacke (1905) (with a symmetric introvert and eggs without a sub-polar filament) and with the specimens found on Aegla riolimayana from Limay river (Neuquén Province, Argentina), assigned to T. chilensis by Damborenea (1991, 1992) (with a symmetric introvert and a sub-distal expansion of the shaft).

On A. alacalufi and A. manni from the Burritos River (Osorno Province, Chile), and on A. riolimayana from the Ñireco stream (Neuquén Province), T. monticellii n. sp. and T. chilensis were found to be syntopic sensu Rivas, 1964, or synhospitalic sensu Eichler, 1966 (two or more related species living together on the same individual host, time and geographic locality).

Diagnosis. Temnocephala monticellii n. sp. is characterized by having a straight or only slightly curved penial stylet, 140–242 µm in length, frequently with a sub-distal swelling in the shaft; a symmetric and wide introvert (25–38 µm in diameter) that has at least 54 symmetrical spine-like projections, each bearing 6–7 internal spines; a seminal vesicle that opens polarly into the contractile vesicle; a vagina with a symmetrical sphincter; a pair of paranephrocytes located at the level of the posterior side of the anterior testes, a second pair at the level of the posterior side of the posterior testes, and eggs without a polar filament.

Distribution. Type locality and host. Palena Province, X Región (also known as ‘Región de los Lagos’), Chile: Aegla alacalufi Jara and López, 1981 ( Decapoda , Aeglidae ) from Burritos River (43°24’S; 72°21’W), 21 January 1999. Site of infection: body surface, mainly on coxa and eye peduncles. Collector: Erich Rudolph.

Additional localities and hosts in Chile. Palena Province, X Región: Aegla manni Jara, 1980 from Burritos River (43°24’S; 72°21’W), 21 January 1999. Valdivia Province, X Región: Aegla abtao Schmitt, 1942 , A. manni and Samastacus spinifrons (Philippi, 1882) from Ranco Lake (40°11’S; 72°22’W), 20 August 1988. Collector: Erich Rudolph.

Additional localities and hosts in Argentina. Neuquén Province: Aegla riolimayana Schmitt, 1942 from Arroyo Ñireco (41°04’S; 71°08’W), 10–21 January 1991 . Río Negro Province: Samastacus spinifrons from Puerto Pañuelo (41°03’S; 71°31’W) , Nahuel Huapi Lake, Bariloche, and 1.5 km east from Bariloche (41°07’S; 71°18’W), 31 January 1983. Collector: Rodrigo Ponce de León.

Figures

FIGURE 1. Temnocephala monticellii n. sp. (A) Whole specimen in ventral view. Bar = 500 µm. Arrowheads, right-side paranephrocytes. (B) Main reproductive organs in ventral view, drawn from a dissection. Bar = 100 µm. Abbreviations: at, atrium; cv, contractile vesicle; ev, excretory vesicle; go, gonopore; hg, Haswell’s glands; in, intestine; ov, ovary; ph, pharynx; ps, penial stylet; rv, resorbiens vesicle; sg, sucker glands; sp, sphincter; sr, seminal receptacle; su, sucker; sv, seminal vesicle; te, testes; tg, tentacular glands; vg, vagina; vi, vitellaria.

FIGURE 2. Temnocephala monticellii n. sp. (A) Non-everted penial stylet in lateral view. Bar = 50 µm. (B) Fully everted introvert. Bar = 25 µm. (C) Egg. Bar = 250 µm.