Temnocephala amatoi, Seixas & Amato & Amato, 2020

Seixas, Samantha A., Amato, Suzana B. & Amato, José F. R., 2020, Temnocephalan epibionts (Platyhelminthes, Temnocephalida) on mollusks from Pantanal wetland, Brazil, Zootaxa 4858 (3), pp. 341-357 : 344-354

Temnocephala amatoi sp. nov. Seixas & Amato

( Figs 2C, 2 H–I, 3C, 4D–F, 5M–Q, 6E–F, 7E–F)

Description. Based on 61 collected specimens: 32 specimens mounted in toto (25 adults and 7 juveniles); 4 specimens mounted on stubs for SEM; 11 extracted cirri mounted in Faure; 18 specimens measured: External characteristics. Body, without tentacles ( Figs 2C , 4D and 6E ) 1402–2686 (2004, 346) long, 849–1698 (1261, 272) wide; adhesive disk ventral, subterminal, partially covered by body 276–573 (449, 95) long, 336–691 (566, 109) wide; disc peduncle 158–375 (259, 63) long; ratio between total body length/adhesive disk length 4.5:1. Two EPs, longer than wide ( Figs 4D and 4E ); external margin reaching ventrolaterally the margin of body ( Fig. 4F ); left plate 186–196 (190, n = 3, 5) long, 97–150 (115, n = 3, 30) wide; right plate 162–185 (173, n = 2, 16) long, 80–106 (93, n = 2, 19) wide; ratio between total body length, without tentacles/length of EPs 10.5: 1; ratio between total body width/width of the EPs 11:1. Nephridiopore (excretory pore) in the anterior half of the plate ( Fig. 4E ). Red pigmentation of the eyespots present (observations made on live specimens). Digestive system. Pharynx 296–454 (377, 46) long, 138–414 (276, 80) wide, with a small anterior sphincter and a larger posterior sphincter ( Figs 2C and 6E ); esophageal glands surrounding esophagus at base ( Fig. 3C ); and a saccular intestine ( Figs 2C and 6E ). Glands. Rhabditogen glands dense, numerous and with granular appearance 40–72 (54, 11) in diameter, forming bunches (average 24 cells) in lateral fields of body ( Fig. 3C ), extending from the beginning of intestinal sac to the anterior testes, ducts inconspicuous. Two pairs of Haswell glands ( Fig. 6E ), in front of the brain transverse band, diameter of the largest cell 52–82 (72, n = 15, 8). Disc glands ( Fig. 3 C—white arrows) 50–77 (56, 8) in diameter, between adhesive disc and genital complex forming two lateral bunches extending from posterior testes to margin of adhesive disc, including two pairs of large, round and more central paranephrocites ( Fig. 3 C—asterisks), 72–105 (90, n = 5, 12) in diameter. Reproductive system. Female. Vitellaria arborescent and slender; vesicula resorbens large and usually full of sperm ( Figs 2H and 7E ), 65–242 (148, 51) long, 90–255 (176, 54) wide; wall thickness 2–12 (5, 2); four seminal receptacles ( Figs 2H and 7E ) 15–35 (26, n = 16, 6) long; a large and ovoid ovary 87–205 (149, 36) long, 55–155 (90, 24) wide; long vagina with a weak muscular wall, distal portion with slight thickening of the muscular wall ( Figs 2H and 7E ), 57–137 (106, n = 17, 24) long, 30–80 (47, n = 17,12) maximum width; a single and asymmetrical vaginal sphincter ( Figs 2H and 7E ), 30–72 (47, 11) in total diameter, diameter of anterior portion 10–17.5 (15, n = 11, 3), diameter of posterior portion 20–32.5 (25, n = 11, 3); eggs not observed. Male. Four ovoid testes ( Figs 2C and 6E ), located two by two on each side of the body; right anterior testis 145–345 (250, n = 11, 69) long, 140–275 (193, n = 11, 42) wide; right posterior testis 210–445 (302, n = 11, 73) long, 200–350 (239, n = 11, 41) wide; left anterior testis 130–350 (247, n = 11, 62) long, 160–260 (197, n = 11, 36) wide; left posterior testis 190–475 (313, n = 11, 85) long, 215–320 (258, n = 11, 38) wide; a long and thin seminal vesicle ( Figs 2I and 7F ) 177–312 (231, n = 11, 53) long, 32–95 (60, n = 11, 19) wide; wall thickness 2–5 (4, n = 11, 1); a large prostatic bulb with thick muscular wall ( Figs 2I and 7F ), 90–250 (158, n = 16, 49) long, 57–125 (99, n = 16, 22) wide; wall thickness 2–7 (6, n = 17, 2); a well defined prostatic vesicle with abundant prostatic secretion ( Fig. 2I ). Cirrus short and curved in the distal portion ( Figs 5M , 6F and 7F ) 140–202 (164, n = 11, 16) long; shaft 105–137 (123, n = 11, 9) long, shaft base 105–135 (119, n = 11, 9) wide; introvert 33–42 (37, n = 11, 3) long, 17–22 (21, n = 11, 2) wide at base; maximum introvert width at level of swelling, 17–27 (23, n = 11, 3). Introvert swelling with approximately 22 longitudinal rows of spines with 13 spines each ( Fig. 5 N–Q). Spines with a narrow base, longer on the base of the introvert 8–10 (9, n = 4, 0.9) and smaller in the distal portion 3.3–4.7 (3.8, n = 10, 0.4) ( Fig. 5P ). Ratio between total body length, without tentacles/total length of cirrus 12: 1; ratio between total length of cirrus/maximum width of shaft’s base 1.3: 1; ratio between total length of cirrus/total length of introvert 4.5: 1.

Taxonomic summary. Type host. Pomacea scalaris (d’Orbigny, 1835) ( Gastropoda, Caenogastropoda, Ampullariidae ).

Type locality. Ypiranga Farm , Poconé, Mato Grosso, Brazil .

Site of infestation. Adults and juveniles in mantle cavity, eggs not observed.

Other helminth specimens examined. Temnocephala iheringi , Temnocephala haswelli , and Temnocephala rochensis from P. canaliculata— specimens deposited in the ‘Coleção Helmintológica do Laboratório de Helmintologia da UFRGS’, Porto Alegre, Rio Grande do Sul, Brazil, and ‘Colección de Invertebrados, División Zoologia Invertebrados; Museo de La Plata ( MLP)’, La Plata, Argentina: MLP-He 3118 (Arroyo Miguelin, Punta Lara); MLP-He 3119 and 3121 (Canteras de Berisso, Los Talas, Berisso); MLP-He 3120 (Arroyo Doña Flora, Ensenada, Buenos Aires, Argentina).

Helminth specimens deposited. ‘ Colección de Invertebrados , División Zoologia Invertebrados, Museo de La Plata ( MLP)’, La Plata, Argentina: MLP-He 7694 (HOLOTYPE) and MLP-He 7695 (paratypes: three specimens in toto and two cirri) .

Etymology. Named in honor of our late friend and colleague Dr. José Felipe Ribeiro Amato (01/03/1944 – 09/01/2018), who devoted part of his career to studying and teaching biology, taxonomy and systematics of the temnocephalids.

Remarks. The specimens of Temnocephala amatoi sp. nov. have a short cirrus with a curved distal portion (approximately 40 o) ( Figs 5M and 6F ). The introvert is narrow and spines are longer on the base and smaller on the distal portion ( Fig. 5P ). A long vagina with a thin muscular wall whose distal portion, a small one with a slightly thicker muscular wall, is easily confused with the sphincter. A single and asymmetrical vaginal sphincter, which is smaller in the anterior portion and that according to the angle, may appear almost symmetrical ( Figs 2H and 7E ). Two pairs of paranephrocytes and large and conspicuous rhabditogen glands ( Fig. 3C ). EPs elliptical, longer than wide, with the external margin reaching ventrolaterally the margin of body, excretory pore in the anterior portion of the plate ( Fig. 4E ).

Taxonomic affinites. The female reproductive system of Temnocephala epibiont’s species on mollusks is generally conspicuous (except in T. lamothei and T. euryhalina ) ( Damborenea & Brusa 2008; Seixas et al. 2015a). Volonterio (2007) proposed that a series of characters be added to those normally presented in the characterization of Temnocephala species, among them, the number and shape of the vaginal sphincter(s). All the species of Temnocephala on molluks have a single vaginal sphincter ( Damborenea & Brusa 2008; Seixas et al. 2010b, c; Garcés et al. 2013; Seixas et al. 2015a). Temnocephala rochensis , T. colombiensis and T. euryhalina have a symmetrical vaginal sphincter. However, similar to T. amatoi sp. nov., T. iheringi and T. haswelli have an asymmetrical one. The vaginal sphincter in the later three species has a smaller anterior portion, but the total diameter is smaller in by Seixas et al. (2010a) from Pomacea canaliculata . Measurements are in micrometers (μm).

T. amatoi sp. nov. (47 µm on average in T. amatoi sp. nov., 60 µm on average in T. iheringi and 86 µm on average in T. haswelli ). Details of the vaginal sphincter of T. lamothei were not presented by the authors, but it is probably symmetrical as we can see in the illustration provided ( Damborenea & Brusa 2008, Figure 2 ). Based on cirrus length, the species of Temnocephala epibiont on mollusks could be classified into two groups: The ‘large cirrus’ group that comprises T. rochensis (243 µm on average), T. haswelli (215 µm on average), and T. colombiensis (213 µm on average). The ‘small cirrus’ group, along with T. amatoi sp. nov. (164 µm on average): T. euryhalina (124 µm on average), T. lamothei (167 µm on average), and T. iheringi (190 µm on average) ( Damborenea & Brusa 2008; Seixas et al. 2010b, c; Garcés et al. 2013; Seixas et al. 2015a). The introverts of the other three species of the ‘small cirrus’ group are unique, T. iheringi has a swollen introvert (35 µm wide at inflation on average) with approximately 20 rows of seven long spines per row and T. euryhalina has a simple introvert (32 µm wide at inflation on average) with approximately 28 rows of five thin spines only at the tip followed by a smooth region ( Seixas et al. 2015a). Also, between these species, T. lamothei is the most similar to T. amatoi sp. nov., both have a curved cirrus with similar total length. The introvert of T. amatoi sp. nov. is narrow (23 µm wide at inflation on average) with approximately 22 rows of 13 spines each, longer on the base of the introvert (9 µm on average) and smaller on the distal portion (3.8 µm on average), while the introvert of T. lamothei is not swollen with an oblique proximal margin, marked with a thickened oblique ring. The only two rows of 45–50 thin spines (5–7 µm), both inner and outer the margin of the introvert, also differentiate the species from T. amatoi sp. nov. ( Damborenea & Brusa 2008).

Figures

FIGURE 2. Adult specimens. Scale bars = 1 cm. (A) Temnocephala iheringi from Marisa planogyra. (B) T. iheringi from Pomacea maculata. (C) Temnocephala amatoi sp. nov. D and E. Partial reproductive system of T. iheringi from M. planogyra. (D) Female. Scale bar = 50 μm. (E) Male. Scale bar = 100 μm. F–G. Partial reproductive system of T. iheringi from P. maculata. (F) Female. Scale bar = 50 μm. (G) Male. Scale bar = 100 μm. (H–I) Partial reproductive system of T. amatoi sp. nov. Scale bar = 100 μm. (H) Female. (I) Male. (anterior (avs) and posterior (pvs) portions of the vaginal sphincter, cirrus (c), genital atrium (ga), ovary (ov), prostatic bulb (pb), prostatic secretions (ps), prostatic vesicle (pv), seminal receptacles (asterisk), seminal vesicle (sv), vagina (va), and vesicula resorbens (vr)).

FIGURE 3. Juvenile specimens showing glands. Scale bars = 150 μm. (A) Temnocephala iheringi from Marisa planogyra, ventral view, showing rhabditogen glands (head arrows), and a pair of paranephrocytes (arrows). (B) T. iheringi from Pomacea maculata, ventral view, showing rhabditogen glands (head arrows), esophageal glands (eg), and a pair of paranephrocytes (arrows). (C) Temnocephala amatoi sp. nov., dorsal view, showing rhabditogen glands (head arrows), disk glands (arrows), esophageal glands (eg), and two pairs of paranephrocytes (asterisk).

FIGURE 4. Scanning Electron Microscopy of adult specimens, dorsal view. A and B. Temnocephala iheringi from Marisa planogyra. (A) Right dorsolateral ‘excretory’ syncytial plate (head arrows) and nephridiopore (n). Scale bar = 100 μm. (B) Higher magnification of the right plate, showing nephridiopore (n), and the limits of the plate (head arrows). Scale bar = 50 μm. (C) Temnocephala iheringi from Pomacea maculata, showing right ‘excretory’ syncytial plate (head arrows) and nephridiopore (n). Scale bar = 50 μm. D, E and F. Temnocephala amatoi sp. nov. (D) Dorsolateral ‘excretory’ syncytial plates (head arrows) and nephridiopore (n). Scale bar = 100 μm. (E) Higher magnification of the right plate, showing nephridiopore (n), and the limits of the plate (head arrows). Scale bar = 20 μm. (F) Ventrolateral limits of the right plate (head arrows), and nephridiopore (n). Scale bar = 50 μm.

FIGURE 5. Photomicrographs of cirri, seen with Nomarski’s DIC microscopy. A–F. Temnocephala iheringi from Marisa planogyra. (A) Entire cirrus, showing the thickening ring on the base of the swelling (white head arrows), the proximal limit of introvert (arrow), and the shaft rim (black head arrows) typical of adult worms. Scale bar = 25 μm. (B–F) Introvert seen in different focusing planes, from the top of the internal surface to mid-section, showing the thickening ring on the base of the swelling (head arrow). Scale bars = 10 μm. G–L. Temnocephala iheringi from Pomacea maculata. (G) Entire cirrus, showing the thickening ring on the base of the swelling (white head arrows), the proximal limit of introvert (arrow), and the shaft rim (black head arrow). Scale bar = 25 μm. (H–L) Introvert seen in different focusing planes, from the top of the internal surface to mid-section, showing the thickening ring on the base of the swelling (head arrow). Scale bars = 20 μm. M–Q. Temnocephala amatoi sp. nov. (M) Entire cirrus, showing the proximal limit of introvert (arrow), and the shaft rim (head arrows). Scale bar = 5 μm. (N–Q) Introvert seen in different focusing planes, from the top of the internal surface to mid-section, showing the proximal limit of introvert (arrows) and the longer (black head arrow) and smaller (white head arrow) spines on the introvert. Scale bars = 10 μm.

FIGURE 6. Diagrams of adult specimens. A and B. Temnocephala iheringi from Marisa planogyra. (A) Incomplete diagram. Scale bar = 250 μm. (B) Diagram of cirrus. Scale bar = 25 μm. C and D. Temnocephala iheringi from Pomacea maculata. (C) Incomplete diagram. Scale bar = 250 μm. (D) Diagram of cirrus. Scale bar = 10 μm. E and F. Temnocephala amatoi sp. nov. (E) Incomplete diagram. Scale bar = 250 μm. (F) Diagram of cirrus. Scale bar = 20 μm. (adhesive disk (ad), anterior testes (at), brain transverse band (b), excretory vesicle (ev), Haswell glands (hg), intestine (i), mouth (m), pharynx (ph), posterior testis (pt), proximal limit of the introvert (arrow), thickening on the base of the introvert (head arrow), vitelline glands (vg), and tentacles (t)).

FIGURE 7. Diagram of partial reproductive system of adult specimens. Scale bars = 50 μm. A and B. Temnocephala iheringi from Marisa planogyra. (A) Female. (B) Male. C and D. Temnocephala iheringi from Pomacea maculata. (C) Female. (D) Male. E and F. Temnocephala amatoi sp. nov. (E) Female. (F) Male. (anterior (avs) and posterior (pvs) portions of the vaginal sphincter, cirrus (c), genital atrium (ga), ovary (ov), prostatic bulb (pb), prostatic secretions (ps), prostatic vesicle (pv), seminal receptacles (sr), seminal vesicle (sv), vagina (va), vasa deferentia (vd), and vesicula resorbens (vr)).