Ascarophis morronei, Aguilar-Aguilar & Ruiz-Campos & Martorelli & Montes & Martínez-Aquino, 2019

Aguilar-Aguilar, R., Ruiz-Campos, G., Martorelli, S., Montes, M. M. & Martínez-Aquino, A., 2019, A New Species Of Ascarophis (Nematoda: Cystidicolidae) Parasitizing Clinocottus Analis (Pisces: Cottidae) From Baja California, Mexico, Journal of Parasitology (J. Parasitol.) 105 (4), pp. 524-532 : 525-528

Ascarophis morronei n. sp.

( Figs. 1–3 )

General: Filiform medium-size nematodes. Two lateral amphids. Oral opening elongated along the dorsoventral axis and surrounded by 4 reduced submedial labia and 2 lateral pseudolabia, each one with a prominent conical tooth-like structure on its anterior surface. Four slender cephalic papillae located ventro- and dorsolaterally. Two lateral amphids. Mouth followed by buccal capsule and esophagus divided into muscular and glandular region. Deirids small, bifurcated, asymmetrically situated anterior to level of nerve ring. Excretory pore posterior to level of nerve ring. Nerve ring encircling the muscular esophagus near anterior end. Tail of both sexes conical, with rounded tip bearing a minute rounded apical projection.

Male (based on 7 specimens): Body 6.56–7.59 (7.15 ± 0.53) mm long, maximum width 78.1–105.9 (89.1 ± 18.3). Buccal capsule (vestibule) 121.7–130.8 (126.4 ± 3.8) long. Muscular esophagus 172.1–200.1 (187.9 ± 14.34) long, glandular esophagus 1.32–1.46 (1.39 ± 0.09) mm long. Nerve ring 162.7–168.4 (165.6 ± 2.5), deirids 130.1–136.6 (133.8 ± 3.3)/132.3 ± 138.3 (135.5 ± 3.04), and excretory pore 251.1–295.4 (263.7 ± 27.6) from anterior end of body. Four pairs of subventral preanal papillae. Five pairs of postanal papillae, second pair lateral, remaining pairs subventral. A pair of small phasmids situated ventrally, near to the end of the body. Conspicuous ventral cuticular ridges (area rugosa). Left spicule 438.2–490.6 (471.8 ± 29.2) long, right spicule 80.8–106.9 (89.4 ± 10.1) long. Length ratio of spicules 1:4.6–5.7 (1:5.2 ± 0.6). Tail conical, with rounded tip bearing a very minute rounded apical projection.

Female (based on 9 gravid specimens): Body 11.39–15.31 (12.49 ± 1.88) mm long, maximum width 112.8–229.9 (157.1 ± 54.3). Buccal capsule (vestibule) 125.4–142.3 (135.7 ± 7.6). Muscular esophagus 369.2–438.7 (393.2 ± 31.9) long. Glandular esophagus 1.37–1.83 (1.6 ± 0.19) mm long. Nerve ring 170.9–190.7 (182.1 ± 8.1), deirids 133.9–157.5 (144.5 ± 8.6)/147.1–154.7 (151.9 ± 4.3), and excretory pore 239.7–288.8 (270.1 ± 26.5) from anterior end of body. Tail conical, with rounded tip bearing a minute rounded apical projection. Anus, 71.1–82.5 (78.9 ± 4.5) from posterior end of body. Uterus amphidelphic. Vulva postequatorial situated 7.1– 9.4 (8.3 ± 1.2) mm from anterior extremity, at 60–61% of body length. Mature (larvated) egg oval, bearing small knob with 2–3 large filaments on 1 pole. Size of eggs 37.2–39.3 X 19.6–21.3 (38.6 ± 0.8 X 20.6 ± 0.7).

Molecular data: A total of 8 SSU assembly sequences (forward and reverse) were obtained from 4 adult Ascarophis specimens (2 males and 2 females) from C. analis . Sequences of SSU gene fragments were obtained with 676 base pairs (bp). Nucleotide sequence variation in the SSU alignment from dracunculids to the phylogenetic reconstruction had 532 conserved sites, 50 variables sites, 28 parsimony-informative sites, and 22 singleton sites .

In order to evaluate the phylogenetic position of Ascarophis morronei n. sp., a Bayesian phylogenetic analysis was undertaken using 4 individuals of the new species, plus 2 other Ascarophis species (i.e., Ascarophis adioryx Machida, 1981 and Ascarophis arctica Polyansky, 1952 ), 1 for the genus Metabronema , 1 for Neoascarophis , 1 for Cystidicoloides , 1 for Cystidicola , 1 for Spinitectus , 1 for Salmonema , and 1 for Capillospirura , all them considered as members of the family Cystidicolidae ; furthermore, also included were 4 taxa of Acuariidae , 3 of Physalopteridae , 1 of Rhabdochonidae , and 1 of Philometridae as outgroups. The SSU tree clearly shows that all samples of A. morronei conform a monophyletic clade (PP 0.95); these samples are sister to the clade including A. arctica and Cystidicola farionis Fischer, 1798 (with high nodal support values, PP 0.95); however, the phylogenetic relationship between A. arctica and C. farionis lacks nodal support value. Capillospirura sp. is the sister group of both clades, with high nodal support values (PP 0.95). Only 1 clade (monophyletic group with PP 0.95), with 4 representatives from Cystidicolidae family, was recovered, i.e., Capillospirura sp. , A. arctica , C. farionis , and Ascarophis morronei n. sp. ( Fig. 4 ). The genetic distance values of A. morronei n. sp. in comparison to those taxa included in the ‘‘ Cystidicolidae clade’’ were 1.72% to A. arctica , 2.07% to C. farionis , and 2.24% to Capillospirura sp. , whereas for other members of Cystidicolidae the distance values were 2.93% to A. adioryx , 3.97% to Cystidicoloides vaucheri Petter, 1984 , 3.10% to Neoascarophis longispicula Moravec and Klimpel, 2009 , 3.79% to Spinitectus carolini Holl, 1928 , 3.45% to Salmonema ephemeridarum (von Linstow, 1872) , and 2.41% to Metabronema magnum (Taylor, 1925) . The genetic distance values of Ascarophis morronei n. sp. to the Acuariidae taxa ranged from 2.41 to 2.76%; furthermore, the distance of this new species to members of Physalopteridae varied from 2.76 to 3.10%, and finally to R. mazeedi Prasad and Sahay, 1965 (Rhabdochonidae) , the distance value was 3.79% ( Table I ).

Taxonomic summary

Type host: Clinocottus analis (Girard, 1858) ( Scorpaeniformes : Cottidae ).

Type locality: Punta Morro at Todos Santos Bay, Ensenada, Baja California, Mexico (31°51 ′ 41 ′′ N, 116°39 ′ 57 ′′ W) .

Site of infection: Stomach wall.

Deposition of specimens: Holotype CNHE 11124 (male); allotype CNHE 11125 (female); paratypes CNHE 11126 and CRPH N0001 .

ZooBank Registration: urn:lsid:zoobank.org:act:DA7011D4-EA10-45F1-A13D-E259D571E672

Etymology: This species is named in honor of Dr. Juan Jose´ Morrone, in recognition of his significant contribution to the knowledge of the patterns of biodiversity in Latin America.

Remarks

The genus Ascarophis includes more than 40 species parasitic as adults in the gastrointestinal tract of marine and estuarine fishes (Moravec and Justine, 2007). Ferrer et al. (2005) considered 34 valid species, dividing them in 3 groups by the presence (or lack) of egg filaments. Eight additional species, Ascarophis tropica (Solov’eva, 1996); Ascarophis chilensis (Muñoz, Gonzaĺez and George-Nascimento, 2004) ; Ascarophis maulensis (Muñoz, González and George-Nascimento, 2004) ; Ascarophis carvajali Muñoz and George-Nascimento, 2007 ; Ascarophis draconi Muñoz and George-Nascimento, 2007 ; Ascarophis richeri Moravec and Justine, 2007 ; Ascarophis longiovata Moravec and Klimpel, 2009 ; and Ascarophis scatophagi Moravec, Yooyen and Sanprick, 2018 , have been later described or transferred to the genus Ascarophis , and characterized considering the morphological and morphometrical variation of the cephalic structures, eggs, and spicules ( Muñoz et al., 2004; Muñoz and George-Nascimento, 2007; Moravec and Justine, 2007, 2009, Moravec and Klimpel, 2009; Pereira et al., 2013; Moravec et al., 2018).

Ascarophis morronei n. sp. belongs to those groups having egg filaments on a single pole and reduced submedial labia. Among Ascarophis species possessing a single polar knob with filaments ( Ferrer et al., 2005), only Ascarophis mexicana Moravec , Salgado-Maldonado and Vivas-Rodriguez, 1995 and Ascarophis valentina Ferrer, Aznar, Balbuena, Kostadinova, Raga and Moravec, 2005 have reduced labia; of these, the new species is easily distinguished from A. mexicana because this later species is much larger, having a very long left spicule of more than 1 mm long ( Moravec et al., 1995). Ascarophis morronei n. sp. resembles A. valentina in terms of the close ranges for spicules, and sizes of the eggs, that also possess 2 long filaments; however, despite specimens of the new species are slightly smaller than A. valentina , distances from the anterior extremity of nerve ring and excretory pore are comparatively longer. Additionally, esophagus length is consistently shorter in the new species (except for the length of the muscular esophagus of females, which is larger than A. valentina ), and the distance of the vulva from the anterior end is smaller than A. valentina , probably associated with the slightly smaller size of females; furthermore, its position is more anterior (distance of the vulva from anterior end / body length ¼ 60 % ± 0.89 vs. 74% ± 3.0 for A. valentina ). Additional differences between both species are host orders ( Scorpaeniformes vs. Perciformes ) and its very disjunct geographical distribution (Southern California Bight vs. Western Mediterranean, sensu Spalding et al., 2007). All other remaining Ascarophis species with filaments on a single pole ( Ascarophis capelanus Nikolaeva and Naidenova, 1964 , Ascarophis epinepheli Wang, 1984 , Ascarophis filiformis Poljansky, 1952 , Ascarophis minuta Ko, 1985 , Ascarophis morrhuae Van Beneden, 1871 , Ascarophis sebastodis Olsen, 1952 , Ascarophis slanskisi Solov’eva, 1987, Ascarophis extalicola Appy, 1981 , and Ascarophis japonica Zhukov, 1960 ) can be easily differentiated from the new species by having well-developed buccal structures and/or the length of the left spicule ( Ko, 1986; Ferrer et al., 2005). On the other hand, remaining species with reduced labia differ from A. morronei by lack of filaments on the eggs ( A. nasonis Machida, 1981 ), or the presence of filaments on both poles ( Ascarophis ayalai Caballero, 1975 , A. chilensis , A. maulensis , and A. richeri ).

Two species of the genus Ascarophis have been described from fishes of the family Cottidae ( Ferrer et al., 2005) . Ascarophis arctica was recorded from the Fourhorn Sculpin Myoxocephalus quadricornis (L., 1758), from the northern Baltic Sea (Fagerholm and Berland, 1988), and clearly differs of A. morronei n. sp. by the presence of filaments on both poles. Furthermore, A. arctica exhibits a left spicule two times bigger than in the new species. The other species, A. extalicola , was described from the mucosa of rectum and posterior intestine of the Atlantic Cod Gadus morhua (L., 1758), and was also found in the rectum of one longhorn sculpin Myoxocephalus octodecemspinosus (Mitchill, 1814) , from Passamaquoddy Bay, Canada ( Appy, 1981). Both sites of infection inside the host and geographic locations are relevant differences respect to the new species. In addition, A. extalicola exhibits numerous filaments arising from one pole, and the left spicule is smaller than in A. morronei n. sp.

Figures

Figure 1. Ascarophis morronei n. sp. (A) Male. Anterior end (dorsal view). (B) Male. Posterior end (lateral view).

Figure 2. SEM of Ascarophis morronei n. sp. (A) Male. Anterior end (anterolateral view). (B) Male. Anterior end (frontal view). (C) Tail of male (lateral view). (D) Female. Deirid.

Figure 3. Ascarophis morronei n. sp. (A) Female. Anterior end (lateral view). (B) Eggs. (C) Female. Detail of excretory pore (e.p.) aperture in relation with the nervous ring (n.r.). (D) Detail of vulvar region.

Figure 4. Phylogenetic relationships (Bayesian inference) within taxa of the infraorder Spirurimorpha based on small subunits (SSU), showing the position of Ascarophis morronei n. sp. in bold. Filled circles represent Bayesian posterior probability 0.95.