Research Article |
Corresponding author: Moisés Gallas ( mgallas88@gmail.com ) Academic editor: Ana Maria Leal-Zanchet
© 2019 Moisés Gallas, Cláudia Calegaro-Marques, Suzana B. Amato.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gallas M, Calegaro-Marques C, Amato SB (2019) First report of Rhabdochona acuminata (Nematoda, Rhabdochonidae) in Astyanax aff. fasciatus (Characiformes, Characidae) from Lake Guaíba, southern Brazil. Neotropical Biology and Conservation 14(4): 479-488. https://doi.org/10.3897/neotropical.14.e49025
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Specimens of Rhabdochona (Rhabdochona) acuminata (Molin, 1860) were collected in Astyanax aff. fasciatus (Cuvier, 1819) from Lake Guaíba, municipalities of Guaíba (30°08.28'S, 51°18.53'W) and Barra do Ribeiro (30°17.11'S, 51°18.01'W), southern Brazil. In the present study, the prevalence of R. (R.) acuminata was low (1.43%) when compared to other studies performed with Astyanax spp. from Brazil. The specimens of R. (R.) acuminata showed some morphological differences (mainly the deirids) that have not yet been reported for the species. This is the first report of R. (R.) acuminata from Lake Guaíba, filling a gap of occurrence of this nematode in South America.
Espécimes de Rhabdochona (Rhabdochona) acuminata (Molin, 1860) foram coletados em Astyanax aff. fasciatus (Cuvier, 1819) do Lago Guaíba, municípios de Guaíba (30°08.28'S, 51°18.53'W) e, Barra do Ribeiro (30°17.11'S, 51°18.01'W), no sul do Brasil. No presente estudo, a prevalência de R. (R.) acuminata foi baixa (1,43%) quando comparada com outros estudos realizados com espécies de Astyanax no Brasil. Os espécimes de R. (R.) acuminata apresentaram algumas diferenças morfológicas (principalmente nos deirídeos) que não haviam ainda sido registradas para esta espécie. Este é o primeiro registro de R. (R.) acuminata para o Lago Guaíba, contribuindo para o conhecimento da distribuição deste nematoide na América do Sul.
Characid, morphology, nematode, spirurid, taxonomy
Caracídeo, espirurídeo, morfologia, nematoide, taxonomia
The subfamily Rhabdochoninae was proposed to group nematodes belonging to the genera Rhabdochona Railliet, 1916, Cystidicola Fischer, 1798 and Spinitectus Fourment, 1883 (
The genus Rhabdochona was proposed to accommodate Dispharagus denudatus Dujardin, 1845 (= Rhabdochona denudata (Dujardin, 1845) Railliet, 1916), a parasite of Scardinius erythrophthalmus (Linnaeus, 1758). Until now, 98 to 104 species were described for this genus, presenting a wide geographical distribution (
In the systematic of the genus Rhabdochona, the following subgenera have been proposed: Filochona Saidov, 1953, Rhabdochona Railliet, 1916 and Globochona Moravec, 1972 (
In the Neotropical Region, 12 species have been reported belonging to the subgenus Rhabdochona (
The nematode species R. (R.) acuminata was described by Molin in 1860 as Spiroptera acuminata in Brycon falcatus Müller & Troschel, 1844 from specimens collected by Natterer in 1826 in the state of Mato Grosso, Brazil (
Rhabdochona (R.) acuminata was redescribed by
Seventy specimens of Astyanax aff. fasciatus (Cuvier, 1819) were collected with seine nets between March 2012 and December 2013 from Lake Guaíba, municipalities of Guaíba (30°08.28'S, 51°18.53'W) and Barra do Ribeiro (30°17.11'S, 51°18.01'W), State of Rio Grande do Sul, Brazil. Procedures of transportation and host identification were made according
Measurements are shown in micrometers (µm) unless otherwise stated. The parameters reported are range followed by mean ± standard deviation, and sample size between parenthesis. Photomicrographs were taken with a Zeiss Axiolab microscope with phase contrast. Line drawings were made with a drawing tube mounted on a Nikon E-200 microscope, scanned and prepared using CorelDraw X4 and Adobe’s Photoshop CS2. Ecological parameters follow
Figs
Description based on 10 specimens. Small to medium nematodes with transverse striated cuticle. Oral aperture oval, with four papillae, two ventral and two dorsal. Vestibule elongated, dilated anteriorly to form a funnel-shaped prostom. Prostom anteriorly armed with 14 longitudinal projections similar to teeth in the inner surface. Prostom with basal tooth. Simple deirids, anterior to the nerve ring and the excretory pore. Esophagus divided in muscular and glandular portions, of which the muscular is the smaller portion. Tail of both sexes conical, sharply pointed.
Males (n = 3). Body 16.5–18.2 mm (17.6 ± 0.9 mm; n = 3) long, 0.1–0.2 mm (0.14 ± 0.06 mm; n = 3) wide. Prostom 40–42 (41 ± 1; n = 3) long, 27–30 (29 ± 1; n = 3) wide. Vestibule (including prostom) 127–137 (134 ± 6; n = 3) long, 12–15 (14 ± 1; n = 3) wide. Deirids 40–45 (42 ± 2; n = 3) from anterior extremity. Nerve ring and excretory pore 192–232 (206 ± 23; n = 3) and, 330–350 (339 ± 10; n = 3) from anterior extremity, respectively. Muscular esophagus 480–600 (500 ± 92; n = 3) long, 50 wide; glandular esophagus 4.7‒5 mm (4.9 ± 0.1 mm; n = 3) long, 0.12–0.17 mm (0.15 ± 0.03 mm; n = 3) wide. Esophagus length representing 28.12% of total body length (TBL); muscular esophagus corresponding to 10.1% of glandular esophagus. Posterior extremity with 16 pairs of papillae: 10 pairs precloacal, of which the fourth pair (from cloaca to the anterior extremity) is more lateral; six pairs poscloacal, of which the second pair (from cloaca to the posterior extremity) is more lateral. Unequal spicules, the right smaller, 130–142 (136 ± 6; n = 3) long, and the left 395–445 (420 ± 25; n = 3) long. Cloaca 320–440 (391 ± 25; n = 3) from posterior extremity.
Females (n = 7). Body 35.3‒41.8 mm (38 ± 2 mm; n = 7) long, 0.3‒0.4 mm (0.4 ± 0.03 mm; n = 7) wide. Prostom 45–52 (49 ± 2; n = 7) long, 22–37 (30 ± 6; n = 7) wide. Vestibule (including prostom) 135–160 (145 ± 9; n = 7) long, 12–20 (15 ± 3; n = 7) wide. Deirids 32–42 (38 ± 3; n = 7) from anterior extremity. Nerve ring and excretory pore 170‒270 (206 ± 32; n = 7) and 272–312 (299 ± 16; n = 5) from anterior extremity, respectively. Muscular esophagus 550–610 (576 ± 26; n = 7) long, 50–60 (54 ± 5; n = 7) wide; glandular esophagus 2.8–5.9 mm (5.2 ± 1 mm; n = 7) long, 0.1–0.2 mm (0.18 ± 0.04 mm; n = 7) wide. Esophagus length representing 15.4% of TBL; muscular esophagus corresponding 10.9% of glandular esophagus. Amphidelphic uterus and post equatorial vulva, 18.4–22.4 mm (20.8 ± 1.7 mm; n = 5) from anterior extremity. Eggs smooth, nonfilamented and embryonated, 32–37 (36 ± 1; n = 30) long, and 17–22 (19 ± 1; n = 30) wide. Anus 340–420 (370 ± 30; n = 7) from posterior extremity.
Photomicrographs of Rhabdochona (Rhabdochona) acuminata (Molin, 1860) from Lake Guaíba, southern Brazil. A. Female anterior end seen with phase contrast, ventral view, showing prostom (pro), vestibule (ve) and deirids (white arrowheads). B. Female anterior end seen with phase contrast, ventral view, showing vestibule (ve), muscular esophagus (me) and nerve ring (nr). C. Female posterior region, lateral view, showing intestine (in) and anus (an). D. Eggs stained with rose bengal. Scale bars: 50 µm (A, B), 100 µm (C), 25 µm (D).
Synonyms: Spiroptera acuminata Molin, 1860, Rhabdochona elegans Travassos, Artigas & Pereira, 1928, Rhabdochona fasciata Kloss, 1966, Rhabdochona australis Kloss, 1966, Rhabdochona siluriformis Kloss, 1966.
Host: Astyanax aff. fasciatus (Cuvier, 1819).
Locality: Municipality of Guaíba, Lake Guaíba (30°08.28'S, 51°18.53'W), RS, Brazil.
Site of infection: Anterior intestine.
Prevalence: 1.43%.
Mean intensity of infection: 13 helminths/host.
Mean abundance of infection: 0.19 helminth/host.
Voucher specimens of helminths deposited: CHIOC 35947.
The measures of R. (R.) acuminata found in the literature until 2002 were compiled and compared by
Comparison of measurements (mm) of male specimens of Rhabdochona (Rhabdochona) acuminata (Molin, 1860) obtained from different studies.
Reference |
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Present study |
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Body length | 8–13 | 8.9 | 4.54–8.78 | 6.3–10.22 | 4.18–9.19 | 4.94–8.24 | 6.1–8.8 | 16.5–18.2 |
Body width | 0.1–0.2 | 0.12 | 0.06–0.12 | 0.08–0.12 | 0.07–0.13 | 0.08–0.11 | 0.09–0.13 | 0.1–0.2 |
Prostom | ‒ | 0.06 × 0.04§ | ‒ | 0.01–0.03 × 0.009–0.015 | 0.01- 0.03 × 0.01–0.02 | 0.01–0.02 × 0.01 | 0.02 × 0.01 | 0.04 × 0.03 |
Vestibule length | 0.1–0.15§ | 0.18 | 0.11–0.14 | 0.12–0.15 | 0.08–0.16 | 0.1–0.14 | 0.12–0.13 | 0.13–0.14 |
Deirids* | ‒ | ‒ | ‒ | 0.01–0.05 | 0.03–0.06 | 0.04–0.07 | 0.02–0.03 | 0.04 |
Nerve ring* | ‒ | 0.24§ | 0.1–0.25 | 0.15–0.21 | 0.13–0.2 | 0.13–0.21 | 0.15–0.17 | 0.2–0.23 |
Excretory pore* | 0.25§ | 0.41§ | 0.26 | 0.24 | 0.17–0.31 | 0.18–0.28 | 0.18–0.19 | 0.33–0.35 |
Muscular esophagus | 0.44–0.47§ | 0.32 | 0.23–0.33 | 0.27–0.36 | 0.2–0.37 | 0.2–0.31 | 0.29–0.35 | 0.48–0.6 |
Glandular esophagus | 4.8–5.2§ | 1.04 | 1.1–1.63 | 1.18–1.96 | 0.85–1.83 | 0.75–1.54 | 1.9 | 4.7–5 |
Right spicule | 0.13–0.14 | 0.14 | 0.07–0.13 | 0.08–0.12 | 0.07–0.1 | 0.07–0.08 | 0.11–0.12 | 0.13–0.14 |
Left spicule | 0.42–0.44 | 0.34 | 0.35–0.49 | 0.56–0.59 | 0.42–0.49 | 0.38–0.43 | 0.37–0.39 | 0.39–0.44 |
Tail length** | 0.35–0.40 | 0.2 | 0.21–0.37 | 0.24–0.37 | 0.25–0.38 | 0.2–0.28 | 0.29–0.3 | 0.32–0.44 |
Comparison of measurements (mm) of female specimens of Rhabdochona (Rhabdochona) acuminata (Molin, 1860) obtained from different studies.
Reference |
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Present study |
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Body length | 22–28 | 18 | 12.61–22.3 | 10.7–20.4 | 7.45–16.55 | 5.11–15.2 | 11–14.6 | 35.3–41.8 |
Body width | 0.3 | 0.28 | 0.12–0.29 | 0.09–0.27 | 0.1–0.2 | 0.1–0.2 | 0.17–0.22 | 0.3–0.4 |
Prostom | ‒ | 0.06 × 0.04§ | ‒ | 0.02–0.03 × 0.01–0.03 | 0.02–0.03 × 0.01–0.02 | 0.02–0.03 × 0.01–0.02 | 0.02–0.03 × 0.02 | 0.04–0.05 × 0.02–0.04 |
Vestibule length | 0.1–0.15§ | 0.13 | 0.12–0.16 | 0.14–0.15 | 0.1–0.19 | 0.11–0.15 | 0.11–0.13 | 0.13–0.16 |
Deirids* | ‒ | ‒ | ‒ | 0.06 | 0.04–0.07 | 0.05–0.12 | 0.03–0.04 | 0.03–0.04 |
Nerve ring* | ‒ | 0.24§ | 0.21–0.37 | 0.2–0.27 | 0.13–0.23 | 0.14–0.2 | 0.13–0.22 | 0.17–0.27 |
Excretory pore* | 0.25§ | 0.41§ | 0.28–0.41 | ‒ | 0.17–0.4 | 0.15–0.28 | 0.21–0.27 | 0.27–0.31 |
Muscular esophagus | 0.44–0.47§ | 0.6 | 0.39–0.54 | 0.32–0.47 | 0.22–0.44 | 0.25–0.4 | 0.32–0.45 | 0.55–0.61 |
Glandular esophagus | 4.8–5.2§ | 2.6 | 1.72–5.14 | 1.44–4.41 | 1.05–1.91 | 1.23–1.64 | 2.3–3.8 | 2.8–5.9 |
Vulva** | ‒ | 9.25 | 5.06–11.1 | 4.27–8.19 | 3.35–7.7 | 3.8–7.36 | 5.2–8 | 18.4–22.4 |
Eggs | 0.04 × 0.02 | ‒ | 0.01 × 0.02 | 0.03 × 0.02 | 0.02–0.03 × 0.01–0.02 | 0.02–0.03 × 0.01–0.02 | 0.03 × 0.02 | 0.03–0.04 × 0.02 |
Tail length** | 0.38 | 0.36 | 0.21–0.29 | 0.22–0.24 | 0.17–0.25 | 0.19–0.26 | 0.23–0.24 | 0.34–0.42 |
According to
The morphology of the distal region of the left spicule in the species of Rhabdochona is complex and may present differences according to the position in which it is examined (
The prevalence of R. (R.) acuminata observed in A. aff. fasciatus (n = 70) collected between March 2012 and December 2013 here was extremely low (1.43%) when compared to the prevalence reported in Astyanax bimaculatus (Linnaeus 1758) (41%) (n = 39, between April 2002 and July 2003) and A. fasciatus (36.7%) (n = 79, between April 2002 and July 2003) from the state of Rio de Janeiro (
In Brazil, there are reports of R. (R.) acuminata in the following species of Astyanax: A. bimaculatus, A. fasciatus and Astyanax schubarti Britski, 1964 from the state of São Paulo (
We thank Dra Ana P. S. Dufech for field assistance; the anonymous reviewers for their comments; Dr Philip J. Scholl for reviewing the English version of the manuscript; MG thanks the Brazilian National Research Council (CNPq) for financial support (process #131068/2012-1).