Electrovermis zappum Warren and Bullard, 2019
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publication ID |
https://doi.org/ 10.1016/j.ijppaw.2019.06.008 |
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persistent identifier |
https://treatment.plazi.org/id/03C887E3-FFFD-FF95-FFBC-F461FA9ED896 |
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treatment provided by |
Felipe |
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scientific name |
Electrovermis zappum Warren and Bullard |
| status |
gen. nov. |
3.2. Electrovermis zappum Warren and Bullard View in CoL n. gen. ( Fig. 1−12 View Figs View Figs View Figs )
3.2.1. Diagnosis of adult (based on two stained, whole-mounted specimens and observations of two live adults collected from the heart of the lesser electric ray, N. bancroftii )
Body 1590 and 1780 long, 53 and 55 wide at greatest width, 30 and 32 × longer than wide ( Fig. 3 View Figs ), aspinous. Ventrolateral nerve-cord, primary, and secondary commissure not evident in whole-mount. Mouth 3 in diameter, 9 from terminal end ( Fig. 3 View Figs ). Oesophagus 425 and 500 in total length or 27% and 28% of body length, 11 and 13 in maximum width (at level of pre-caecal dilation); pre-caecal dilation 38 long, 11 wide. Caecal bifurcation 440 and 515 or 28% and 29% of body length from anterior body end; caeca extending posteriad in parallel, asymmetrical, dextral caecum 205 long or 12% of body length, 25 wide or 45% of body width, sinistral caecum 150 long or 8% of body length, 18 wide or 33% of body width, containing granular material within lumen of one individual
( Fig. 3 View Figs ); post-caecal space 975 from posterior margin of the body.
Testis 250 and 325 long or 16% and 18% of body length, 25 and 30 wide or 47% and 55% of body width, 10 and 11 × longer than wide, post-caecal, curving 33 and 34 times ( Fig. 3 View Figs ) widening posterior until narrowing and becoming confluent with vas deferens. ( Fig. 3 View Figs ); post-testicular space 651 long or 37% of body length. Vas deferens 28 and 38 long, 8 and 10 wide, emanating from postero-ventral portion of testis, extending posteriad, looping just before becoming confluent with cirrus-sac. Cirrus-sac 335 long or comprising 19% of body length, max width equaling the width of seminal vesicle, having extremely thin wall approximately <1 thick, including seminal vesicle and cirrus; seminal vesicle 160 and 215 long or 10% and 12% of body length, 23 and 28 wide or 43% and 51% of body width at level of vesicle ( Fig. 3 View Figs ), filling breadth of cirrus sac, extending sinuously posteriad before narrowing and ending 120 from common genital pore. Cirrus extremely long, 140 long or 65% of seminal vesicle length, 4 wide or 14% of seminal vesicle width, extending posteriad, gradually curving before reaching sinistral margin and common genital pore ( Figs. 3 and 4 View Figs ); everted cirrus 15 long or 11% of total cirrus length. Common genital pore 288 or 16% of body length from posterior end of body, bordering sinistral body margin, 45 from dextral body margin ( Fig. 3 View Figs ).
Ovary medial, lobed, 43 and 58 long or 3% of body length, 23 and 30 wide or 43 and 55% of body width at level of ovary, 1.9 × longer than wide, immediately post-testicular. Oviduct and oötype indistinct. Vitellarium having follicles compacted in dense lobules, distributed throughout entire body; common collecting duct indistinct. Uterus extending directly posterior 75 and 122 long before looping back anteriad, displaying marked constriction 140 from posterior end, expanding for 100 as uterine seminal receptacle (resembling seminal vesicle), before sharply turning sinistral creating constriction just posterior to common genital pore before returning anterior, eggs observed in adult specimens ( Figs. 3 and 4 View Figs ); total ascending portion 281 and 358 long or 18% and 20% of body length, 16 and 23 wide, with wall <1 thick, extending anteriad and dorsal to cirrus and posterior region of seminal vesicle before coursing sharply back posterior to form descending portion; descending portion short, 94 and 140 long or 30% and 42% of ascending uterus length, 15 and 21 wide, ( Figs. 3 and 4 View Figs ). Uterine eggs 43 in length or 31% of descending uterus length, 10 in width or 67% of descending uterus width, containing a large oval shell with a spheroid body 7 in diameter, surrounded by several smaller, dense lipid-like bodies ( Figs. 3 and 4 View Figs ). Excretory bladder indistinct.
3.2.2. Description of sporocyst and cercaria (based on seven fixed, whole-mounted cercariae, 10 specimens prepared for SEM, and live cercariae collected and photographed from Donax variabilis )
Sporocyst spheroid, thin-walled, enveloping 5–7 (5 ± 0.8, 21) cercariae, germ sacs present, 88–140 (114 ± 12, 21) in diameter ( Figs. 5 and 6 View Figs ). Rediae not observed.
Body of cercaria non-acetabulate, apharyngeate, non-ocellate, 73–110 (84 ± 11, 15) long, 20–30 (26 ± 3.4, 15) wide or 2.5–4.8 × longer than wide, with dorsal fin fold ( Figs. 7–9 View Figs View Figs ), having spines distributed along lateral body margin ( Figs. 7 View Figs , 9–11 View Figs ). Spines of lateral body margin protruding from tegument approximately 0.7–1 (8), having pointed tips, distributed in transverse rows along lateral body margin of body; transverse spine rows numbering approximately 21–25 (3) per side of body ( Figs. 7 View Figs , 9–11 View Figs ), each comprising 3–4 spines ( Figs. 9–11 View Figs ), approximately
2.5–3 (9) in breadth. Fin fold extensively membranous vulnerable to fixation artifact, observed intact in live, SEM, and one whole-mounted specimen ( Figs. 7–9 View Figs View Figs ), dorsomedial, 4–13 (11 ± 4.3, 4) in maximum height (in posterior half of body), extending from posterior most concentric spine row of anterior sucker and terminating 8 or 9% of body length from body terminus. Sensory papillae on body circular in shape, approximately <1 in diameter, distributed about body surface ( Figs. 9–11 View Figs ). Anterior sucker 3.5–4 (3) long, 4–4.5 (3) wide, spinous ( Figs. 7 View Figs , 9–12 View Figs ); anterior sucker spines minute, visible with SEM at 8000× magnification only (indistinct in whole-mounted specimens), distributed in concentric rows (cf. spinous anterior sucker of teleost blood flukes), protruding from tegument approximately 0.75–1 (10), forming 6 concentric pre-oral rows ( Fig. 12 View Figs ); mouth <1 in diameter (see Fig. 13 View Figs ).
Tail brevifurcate ( Figs. 7 and 8 View Figs ), comprising a tail stem and a pair of furcae; tail stem 153–265 (227 ± 35, 15) long or 1.9–3.5 × body width or 7.6–13.3 × longer than wide, 18–30 (22 ± 3.2, 15) wide or 0.6–0.8 × body width; base 8–15 (10 ± 3, 15) wide at connection to body; tegument appearing rigid, jagged in live specimens ( Fig. 7 View Figs ), filled with cellular masses and associated nuclei ( Fig. 7 View Figs ); excretory duct running medial along length of tail, bifurcating and extending to tips of furcae, lacking obvious fin fold ( Figs. 7 and 8 View Figs ); furcae asymmetrical, appearing boot-shaped in lateral view ( Fig. 8 View Figs ), lacking fin fold; longest furca 23–45 (35 ± 8, 15) long or 3 × longer than shortest furca, 5–8 (5.8 ± 1.2, 15) wide or 4.1–8.6 × longer than wide; shortest furca 10–15 (16 ± 3.8, 15) long or 30–65% of longest furca length ( Figs. 7 and 8 View Figs ).
3.2.3. Diagnosis of schistosomulum (based on six stained, whole-mounted specimens from the heart of the lesser electric ray, N. bancroftii )
Body 730–1420 (1088 ± 255, 5) long, 38–55 (42 ± 7, 5) at greatest width, 19–33 × longer than wide ( Fig. 1−2 View Figs ), aspinous. Oesophagus 75
and 450 long, 2–7 at greatest width ( Fig. 1−2 View Figs ). Cirrus sac 83 long, 3 wide; seminal vesicle 203 long or 14% of body length, 28 wide or 65% of body width at level of vesicle ( Fig. 2 View Figs ), everted cirrus 13 long, 4 wide.
3.2.4. Taxonomic summary
Type and only reported hosts: Lesser electric ray, Narcine bancroftii (Griffith and Smith, 1834) Carvalho, 2001 ( Torpediniformes : Narcinidae ) and variable coquina clam, Donax variabilis Say, 1822 ( Bivalvia: Cardiida : Donacidae ).
Site in host: Heart lumen ( N. bancroftii ); gonad ( D. variabilis ).
Type locality: Fort Morgan , Alabama (30̊13′30.21″N, 88̊ 0′34.18″W), north-central Gulf of Mexico, USA .
Prevalence and intensity of infection: 14 of 54 (prevalence = 26%) lesser electric rays sampled in September 2012, 2013, October 2014, May 2015, and July 2017 were infected by 1 specimen of E. zappum each (mean intensity = 1.0). Six of 1174 (prevalence = 0.5%) of variable coquina clams had several hundred sporocysts and cercariae.
Specimens deposited: Holotype ( USNM 1578574 About USNM ), vouchers ( USNM 1578575–1578586 About USNM ), GenBank Nos. (28S: MN244242 and MN244314 ; 18S: MN244243 and MN244244 ; ITS2: MN244245 and MN244246 ).
Etymology: The specific epithet “ zappum ” refers to the electric charge delivered by the lesser electric ray.
3.2.5. Taxonomic remarks
Adults of the new species are most similar to those of aporocotylids that infect batoids ( O. heterovitellatum , M. richardheardi , and O. glaucostegi ( Madhavi and Hanumantha Rao, 1970; Bullard and Jensen, 2008; Cutmore et al., 2018; Table 1) (excluding G. bulbosus ) by having a diminutive anterior sucker that lacks spines, an asymmetrical and inverse Ushaped intestine, a looped testis that is post-caecal, an internal seminal vesicle and cirrus sac, and a post-caecal common genital pore as well as by lacking lateral tegumental spines. Electrovermis zappum differs from O. heterovitellatum by the combination of having a vermiform (vs. fusiform) body, an inverse U-shaped caeca that is smooth (vs. dendritic), and a testis that is post-caecal (vs. intercaecal) and by lacking lateral tubercles and testicular lobes. The new species can be differentiated from M. richardheardi by the combination of having a body that is 32 × longer than wide (vs. 3 × longer than wide), a straight to sinuous oesophagus (vs. sharply curved), a testis that is 10 × longer than wide (vs. 2.7) and consisting of 34 curves (vs. 10), a seminal vesicle occupying 1/2 the body width (vs. <1/4), a uterus that is located dorsal to the posterior-most extremity of the seminal vesicle (vs. flanking the seminal vesicle), and a seminal vesicle and uterus that are sinuous to straight (vs. extensively convoluted). Electrovermis zappum differs from O. glaucostegi , by the combination of having a body that is smaller, by 1/2 that of O. glaucostegi and 32 × longer than wide (vs. 17–28), a testis that is 1/6 of the body length (vs.>1/3) and that has 34 curves (vs. 52), positioned>1/3 from the terminal body margin (vs.>1/6), a seminal vesicle that is>10% of the total body length (vs. 4%) and occupies 1/2 of the body width (vs.>1/4), an obvious cirrus sac enveloping an extremely elongate cirrus that is> 1/2 of the seminal vesicle length, an ovary that is anterior to the seminal vesicle (vs. lateral), a uterus that is posterior to the testis and ovary (vs. overlapping and lateral to both), and a sinuous or straight (vs. convoluted) uterus. The remaining chondrichthyan blood fluke genera ( Hyperandrotrema Maillard and Ktari, 1978 , Chimaerohemecus , Gymnurahemecus , and Selachohemecus Short, 1954 ( Short, 1954; Van der Land, 1967; Maillard and Ktari, 1978; Bullard et al., 2006; Orélis-Ribeiro et al., 2013; Warren et al., 2019)) all include species having large, C-shaped lateral tegumental spines. The new species lacks lateral tegumental spines altogether.
The sporocyst of the new species and that of other aporocotylids infecting bivalves is spheroid ( Figs. 5 and 6 View Figs ), whereas the sporocyst of aporocotylids infecting polychaetes is elongate with tapered (spindleshaped) or rounded ends ( Cribb et al., 2011; Sugihara et al., 2014; Shirakashi et al., 2016; Siegel et al., 2018). We could not discern a morphological difference between the sporocyst of E. zappum and Holliman's (1961) description of the sporocyst of Cercaria asymmetrica Holliman, 1961 . The diameter of the sporocyst of the new species is <1/2 of the maximum size of those infecting Plebidonax deltoides (Lamarck, 1818) . The number of developing cercariae within a sporocyst is likely taxonomically important. The sporocyst of the new species has 5–7 cercariae and that of C. asymmetrica has 4–8.
The cercaria of E. zappum is most similar to C. asymmetrica and the cercaria that infects P. deltoides ( Cribb et al., 2017) in that it is apharyngeate, non-ocellate, brevifurcate, and spinous as well as by infecting a marine bivalve. The new species differs from the cercaria infecting P. deltoides by having lateral body spines ( Figs. 9 and 10 View Figs ). Cribb et al. (2017) did not mention the presence or absence of lateral body spines but they are clearly absent in their SEM images. We did not observe a morphological difference between E. zappum and the description of C. asymmetrica ( Holliman, 1961; to our knowledge no voucher specimen of C. asymmetrica was deposited in a museum). We observed spheroid masses about the distal end of the anterior sucker of the cercaria of E. zappum ( Figs. 9 and 10; 12 View Figs ). At least superficially, these masses resemble those described for A. simplex (see Køie, 1982) and likely comprise secretions from the penetration glands.
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