Nasuscoelum pampensis, Santos & Mascarenhas & Müller, 2023

Santos, José Junior Dos, Mascarenhas, Carolina Silveira & Müller, Gertrud, 2023, A new genus and new species of Cyclocoelidae (Digenea), a parasite in spotted rail, Pardirallus maculatus (Gruiformes: Rallidae), in the Pampa biome, southern Brazil, Zootaxa 5319 (1), pp. 120-126 : 123-124

Nasuscoelum pampensis n. sp.

Description: Based on 6 specimens. Large body, total length 15.1 mm ±1.6 (14.1–18.3 mm) and 3.4 mm ±0.5 (2.7–4.1 mm) wide in middle of body. Rudimentary oral sucker poorly developed. Short prepharynx 478.3±89.5 (300–550). Large, round and very muscular pharynx 456.6±66.8 (350–550) long and 578.3±78.9 (500 –700) wide. Esophagus 1,158±119 (1,050 –1,300), longer than prepharynx. Ceca forming cyclocoel, distance from cecal bifurcation to anterior extremity of body 7.6% (6.9%–8.6%) of body length. Genital pore prepharyngeal, at level of anterior of pharynx. Smooth, spherical to subspherical testis in intercecal region of posterior 1/3 of body. Anterior testis 425±221.6 (150–670) long and 413.3±200.8 (220–620) wide. Posterior testis 495±76.9 (360–600) long and 761.6±164.6 (520–1,010) wide. Intertesticular space 1,045.8±108.9 (850–1,150), approximately 6.9% of body length. Relatively small posttesticular space, 650±178.2 (475–875), approximately 4.3% of body length. Cirrus sac 800 (750–850) long [approximately 5.3% of body length] and 140 (120–160) wide, based on 3 specimens. Seminal vesicle unobserved. Smooth and oval ovary situated intertesticularly, in triangle with the testis, 421.7±77.3 (320– 550) long and 428.3±66.2 (340–510) wide. Mehlis’ gland post-ovarian. Uterine seminal receptacle not observed. Laurer’s canal not observed. Vitelline follicles distributed along ceca from level short of distance posterior to the intestinal bifurcation to posterior extremity, confluent posteriorly. Uterus extensive, intercecal. Eggs, 130±5.5 (125– 140) long and 65±4.5 (60–70) wide, in anterior aspect of uterus.

Taxonomic summary

Type host. Pardirallus maculatus (Boddaert) ( Gruiformes : Rallidae ), spotted rail.

Sites of infection. nasal cavity and body cavity.

Type locality. Pelotas (31°44’45.6”S – 52°21’43.3”W), RS, Brazil.

Prevalence. 17.6% (3/17).

Mean intensity of infection. 3.7.

Mean abundance. 0.6.

Intensity. 2–5.

Deposited specimens. Holotype deposited in the CHLAPASIL-UFPel (994). Paratypes deposited in the CHLAPASIL-UFPel (990–993, 995, 996) and in the CHIOC (39749 a, 39749 b, 39750).

Etymology. The specific name derives from the Pampa biome, the geographic area where the host was collected.

Remarks. The new genus and species exhibit characteristics of the subfamily Cyclocoelinae , that is, the intertesticular ovary forms a triangle with the testes, as proposed by Dronen (2007), who used the position of the ovary and testes to classify subfamilies of Cyclocoelidae . Cyclocoelinae genera were reorganized by Dronen & Blend (2015). Their study considered the position of the genital pore and the confluence of the vitelline field to classify genera of this subfamily. Four genera were considered valid: Cyclocoelum Brandes, 1892 in which the genital pore is prepharyngeal and vitelline fields are confluent neither in the posterior nor in the anterior aspect of the body; Selfcoelum Dronen, Gardner & Jiménez, 2006 , in which the genital pore is postpharyngeal and vitelline fields are confluent neither in the posterior nor the anterior end of the body; Circumvitellatrema Dronen, Greiner, Ialeggio & Nolan, 2009 in which the genital pore is postpharyngeal and vitelline fields are confluent both posteriorly at the posterior arch of the cyclocoel and anteriorly near the intestinal bifurcation; and Psophiatrema Dronen & Kinsella, 2009 in which the genital pore is postpharyngeal and vitelline fields are confluent near the posterior end but not confluent anteriorly in the area of the intestinal bifurcation. In this context, Nasuscoelum n. gen. is described as the fifth genus of Cyclocoelinae , whereas Nasuscoelum pampensis n. sp. has a prepharyngeal genital pore, confluent vitelline field in the posterior of the body and a non-confluent one in the anterior region.

Another species of Cyclocoelinae , C. mutabile , is similar to Nasuscoelum pampensis n. sp. However, the difference between both is clear due to the confluence of the vitelline field in the posterior region of Nasuscoelum pampensis n. sp. ( Figs. 1 & 2 ) by comparison with C. mutabile (see fig. 1 of Dronen & Blend 2015), which has non-confluent vitelline fields in the posterior region of the body. In addition, Nasuscoelum pampensis n. sp. exhibits some distinct morphometric differences, such as body width, smaller pharynx and anterior and posterior testes and larger eggs than C. mutabile recorded in other species of Rallidae ( Table 1 ) ( Fernandes 1976; Sitko et al. 2016; Gomez-Puerta et al. 2018).

Figures

FIGURE 1. Nasuscoelum pampensis n. gen., n. sp. parasite of Pardirallus maculatus (Boddaert) (Gruiformes: Rallidae) in southern Brazil. A. Ventral view, pharynx (ph), ceca (c), and uterus (u). B. Anterior extremity, genital pore (gp), and cirrus sac (cs). C. Ovarian complex, ovary (ov), Mehlis’ gland (mg), posterior testis (pt).

FIGURE 2. Nasuscoelum pampensis n. gen., n. sp. parasite of Pardirallus maculatus (Boddaert) (Gruiformes: Rallidae) in southern Brazil. A. Anterior extremity, pharynx (ph), cirrus sac (cs). B. Posterior extremity, ovary (ov), Mehlis’ gland (mg), posterior testis (pt), anterior testis (at).