Oligogonotylus andinus, Vélez-Sampedro & Uruburu & Lenis, 2022

Velez-Sampedro, Veronica, Uruburu, Monica & Lenis, Carolina, 2022, Morphological, molecular, and life cycle study of a new species of Oligogonotylus Watson, 1976 (Digenea, Cryptogonimidae) from Colombia, ZooKeys 1115, pp. 169-186 : 169

Oligogonotylus andinus sp. nov.

Diagnosis.

Adult with longitudinal row of three or four sucker-like gonotyls. Vitelline follicles extending between level of pharynx and anterior margin of ovary and occupying 25-38% of body length.

Cercaria description

(Figs 2A , 3A ). Pleurolophocercous type. Cercaria elongate, 149 (114-190) long by 82 (72-100) wide. Oral sucker 35 (18-46) long by 30 (24-34) wide, with three or four anterior rows of hook-like spines. Eyespots anterior to penetration glands. Pharynx located between eyespots. Esophagus and ceca undifferentiated. Penetration glands in middle body; seven pairs lead to exterior in four ducts running parallel to oral sucker in two bundles on each side. Rudimentary ventral sucker in middle body. Cystogenic glands on lateral margins of body. Excretory vesicle bilobed delimited anteriorly by primordial ventral sucker and posteriorly by insertion of tail. Tail longer than body with lateral fin, 294 (274-316) long by 22 (18-26) wide.

Metacercaria description

(Figs 2B , 3B, C ). Encysted form spherical with thin cyst wall of variable thickness occupying entire cyst cavity (Fig. 3B ). Cyst 281 (247-327) long by 193 (136-223) wide. Unencysted forms covered with numerous, simple, single-pointed tegumental spines which are smaller and less dense posteriorly. Oral sucker (Os) large, subterminal, 79 (58-98) long by 67 (50-84) wide. Ventral sucker (Vs) just pre-equatorial to equatorial, 53 (34-70) long by 49 (34-66) wide, smaller than oral sucker; Os/Vs (ratio) 1:0.7 (1:0.6-1:0.8) long by 1:0.7 (1:0.6-1:0.9) wide. Pharynx large, 43 (36-48) long by 38 (30-46) wide. Esophagus short; ceca wide, reaching middle hindbody. Remnants of eyespots at pharyngeal level. Genital primordium indistinct, posterior to ventral sucker. Excretory vesicle large, Y-shaped, with large lateral branches reaching anteriorly to level of ventral sucker and with short posterior duct opening at excretory pore.

Adult description

(Figs 3D , 4A-F ). Body oval to elongate-oval, widest at ovarian level, 517 (271-821, n = 21) long by 248 (167-335, n = 21) wide. Anterior and posterior ends of body rounded. Tegument spinose, with spines becoming shorter and less dense in posterior region. Remnants of eyespots diffuse and scattered at pharyngeal level. Oral sucker rounded, subterminal, without circumoral crown of spines, 106 (84-128, n = 21) long by 110 (66-144, n = 21) wide. Prepharynx short or inconspicuous, 18 (12-28, n = 9) long by 24 (16-28, n = 6) wide, with small extramural glands. Pharynx large, 59 (30-86, n = 18) long by 50 (26-70, n = 18) wide. Esophagus 40 (10-70, n = 13) long. Intestinal bifurcation immediately anterior to ventral sucker. Ceca reach just into post-testicular zone; distance from cecal extremities to posterior end of body 86 (60-114, n = 10). Longitudinal row of 4 (3-4, n = 17) sucker-like gonotyls located between mid-level of pharynx and anterior margin of ventral sucker, increasing in size from anterior to posterior. Ventral sucker rounded, pre-equatorial, 79 (56-100, n = 21) long by 78 (52-104, n = 21) wide, enclosed in ventrogenital sac, smaller than oral sucker; Os/Vs (ratio) 1:0.74 (1:0.61-1:0.88, n = 21) long by 1:0.72 (1:0.60-1:0.83, n = 21) wide; Os-Vs distance 112 (40-178, n = 15). Genital pore close to anterior margin of ventral sucker. Testes two, rounded to oval, in tandem, intercecal, in mid hindbody: anterior testis 72 (20-120, n = 20) long by 82 (50-112, n = 20) wide; posterior testis 80 (50-140, n = 21) long by 81 (46-140, n = 21) wide. Seminal vesicle tubulosaccular, undivided, mostly posterolateral to ventral sucker, 95 (30-128, n = 10) long by 82 (48-120, n = 11) wide. Cirrus sac and cirrus absent. Ovary lobed, median, post-equatorial, intercecal, between ventral sucker and posterior testis, partially overlaps anterior testis, 74 (38-108, n = 17) long by 90 (30-120, n = 17) wide. Seminal receptacle median, ovoid, dorsal, anterolateral to ovary, and ventral to vitelline duct, 65 (40-94, n = 11) long by 59 (40-82, n = 11) wide. Ootype posterolateral to ovary (on right side in type specimen and three paratypes, on left side in three other paratypes). Vitelline follicles small, irregular in shape to oval; arranged in lateral fields partly overlapping ceca or extracecal. Vitelline fields not confluent, extending from mid of pharynx to anterior region of ovary, occupying 32% (0.25-0.38, n = 15) of body length. Uterus in hindbody with several loops, passes medially between ovary and ventral sucker and forward to genital pore. Eggs small, 21 (18-24, n = 57) long by 10 (10-12, n = 57) wide. Excretory pore terminal. Excretory vesicle Y-shaped.

Taxonomic summary.

Type specimens. Holotype: permanent slide; CCH.116: 170. Paratypes: permanent slides; CCH.116: 171 to 178.

Type locality.

Colombia - Antioquia • Sopetrán, La Mirandita village; 6°30'42.0"N, 75°45'22.6"W; fishponds at 750 m a.s.l., February 2020, V. Vélez-Sampedro and C. Lenis leg.

Type hosts.

Andinoacara latifrons (Steindachner, 1878) ( Actinopterygii: Cichlidae ).

Other hosts.

Cercariae in Aroapyrgus colombiensis Malek & Little, 1971 ( Gastropoda, Cochliopidae ); metacercariae in Poecilia caucana (Steindachner, 1880) ( Actinopterygii, Poeciliidae ).

Prevalence

[N (%)]. Cercariae 451 (2.0%); metacercariae 105 (38.1%); juveniles/adults 22 (100%).

Intensity

[mean (range)]. Cercariae 8.6 (2-19); metacercariae 8.3 (5-14); juveniles/adults 41.1 (5-108).

Abundance

[mean]. Cercariae (0.2); metacercariae (3.1); juveniles/adults (39.3).

Site in hosts.

Cercariae in hepatopancreas; encysted metacercariae in muscle; adults in medial region of large intestine.

Etymology.

The specific epithet ( Oligogonotylus andinus ) refers to the geographic distribution of the hosts, which are endemic to the Andes.

Figures

Figure 2. Micrographs of different stages of Oligogonotylus andinus sp. nov. A, B cercariae emerged from Aroapyrgus colombiensis, as temporary mounts C encysted metacercaria from Poecilia caucana, as a temporary mount D unencysted metacercaria isolated from P. caucana, as a permanent slide E, F paratype specimens, as temporary mounts G holotype adult specimen, isolated from A. latifrons, as a permanent slide. Scale bars: 20 μm (A, B); 20 μm (C, D); 100 µm (E-G).

Figure 3. Developmental stages of Oligogonotylus andinus sp. nov. A pleurolophocercous cercaria emerged from Aroapyrgus colombiensis B encysted metacercaria isolated from the muscle of Poecilia caucana C unencysted metacercaria isolated from P. caucana D holotype, adult isolated from the large intestine of the trans-Andean cichlid Andinoacara latifrons. Scale bars: 20 μm (A); 20 μm (B, C); 100 µm (D).

Figure 4. Paratypes of Oligogonotylus andinus sp. nov.; adults at different degrees of maturity A specimen in partly lateral orientation with the first eggs in utero; gonotyls were not observed B, D-F specimens with the seminal receptacle visible (left on B and F, right on E and D) and four gonotyls A, C, D, F specimens with the vitelline duct visible A, D, E specimens with the seminal vesicle dorsal to the ventral sucker. Scale bars: 100 μm (A-F).