Dermopristis pterophilus Ingelbrecht, Morgan and Martin

Ingelbrecht, Jack, Morgan, David L., Lear, Karissa O., Fazeldean, Travis, Lymbery, Alan J., Norman, Bradley M. & Martin, Storm B., 2022, A new microbothriid monogenean Dermopristis pterophilus n. sp. from the skin of the Critically Endangered green sawfish Pristis zijsron Bleeker, 1851 (Batoidea: Pristidae) in Western Australia, International Journal for Parasitology: Parasites and Wildlife 17, pp. 185-193 : 188-191

3.2.1. Dermopristis pterophilus Ingelbrecht, Morgan and Martin n sp

3.2.1.1. Taxonomic summary. Type-host: Pristis zijsron Bleeker, 1851 (Batoidea: Pristidae ), green sawfish.

Type-locality: Ashburton River mouth (21 ◦ 41 ′ 38 ′′ S, 114 ◦ 55 ′ 01 ′′ E) .

Other localities: Hooley’ s Lagoon (21 ◦ 40 ′ 35 ′′ S, 114 ◦ 59 ′ 06 ′′ E), Hooley’ s Creek (21 ◦ 41 ′ 08 ′′ S, 115 ◦ 02 ′ 08 ′′ E), and Four Mile Creek (21 ◦ 40 ′ 59 ′′ S, 115 ◦ 03 ′ 22 ′′ E), Onslow region , Western Australia .

Site of infection: Attached to skin, overwhelmingly on or immediately adjacent to fin bases, especially pelvic fins (including genital area), moderately so on pectoral and dorsal fins, less so around caudal fin, isolated infections elsewhere on dorsal and ventral body surface, no infections anterior to gills on the head or rostrum.

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Prevalence and intensity: 16 of 26 P. zijsron (62%); mean intensity 4.81 (95% CI 1–13).

Type-specimens: Holotype WAM V10840 (ventral wholemount, lactophenol) collected April 25, 2021 on a female P. zijsron 2524 mm total length (TL), in the Ashburton River mouth. Nine paratypes WAM V10841–10849 (nine adults): V10841 (ventral wholemount, Semichon’ s acetocarmine, methyl salicylate) and V10842 (wet mount) collected December 17, 2020 on a male P. zijsron of 751 mm TL (Hooley’ s Lagoon, Ashburton River delta), V10843 (wet mount) collected April 25, 2021 on a female P. zijsron of 1266 mm TL (Ashburton River mouth), V10844–10849 (V10844-10847 wet mounts; V10848 ventral wholemount, Semichon’ s acetocarmine, methyl salicylate; V10849 ventral wholemount, Hoyer’ s solution, Semichon’ s acetocarmine) collected April 25, 2021 on a male P. zijsron of 2595 mm (Ashburton River mouth). Material collected by DLM, TF and KOL.

Representative DNA sequences: Five identical replicates of partial 28S rDNA (GB OM320818), and two identical replicates each of H3 (GB OM320819) and EF1α (GB OM320820).

ZooBank registration: The LSID for D. pterophilus is: lsid:zoobank.org: act: BCB37141-9764-42C9-BCD7-3AA7E491DA96.

Etymology: The specific epithet pterophilus is a compound masculine adjective from Greek πτερον, pteron (wing) and φ ί λος, philos (having affinity for), after the affinity of this parasite to attach proximal to the host fins.

3.2.1.2. Description. Based on seven adult ventral wholemounts including one holotype ( Fig. 2 , Fig. 3 ) and three paratypes; WAM V10840 and V10841 , V10848 and 10849 ( Fig. 4 , Fig. 5 ). Whole animal dimensions based on seven wholemounts and 35 wet mounts, organ dimensions based on three to seven wholemounts and, for germarium, also one wet mount. Measurements are in micrometres (μm) with length followed by width, and range followed by mean in parentheses .

Body dorsoventrally flattened, oval to almost round, broadest at level of gonads in mid-body, longer than wide with length 1.02–1.69 (1.26) times width, 2456–5570 (3863) × 2114–4521 (3085). Tegument without strong, transverse, ventral ridges. Haptor small, almost terminal, roughly circular, 124–332 (228) × 163–297 (209); inner cavity 55–172 (124) × 63–179 (105); sclerites absent; no host denticles observed. Eyes absent. Mouth anterior, sub-terminal, inconspicuous; buccal cavity deeply infolded. Pharynx prominent, somewhat cruciform polypoid, with approximately 14–22 anterior, apparently retractable, digitiform papillae projected into lumen. Prominent muscle fibres apparently associated with pharynx run posterolaterally length of body to near haptor. Isolated, irregular bladder either side of pharynx. Oesophagus absent or indiscernible from gut.

Gut dendritic, blind, thin, unpigmented, sometimes inconspicuous or obscured by vitellarium, bifurcates posterior to pharynx into roughly equal gut-trees; main arms gently sinusoidal, run posteriorly either side of and constrain gonadal and terminal genitalia zones; major gut sub-

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trees six, arise from main gut arms, extend outwards to edge of vitelline follicle field near to body margin, collectively fill much of available body area; first major sub-tree arises immediately after main gut bifurcation, runs anteriorly either side of pharynx; second major sub-tree arises at about level of male genital pore; third major sub-tree arises anterior to germarium; fourth major sub-tree arises at about level to first third of testes; fifth major sub-tree arises at about level to second third of testes; sixth major sub-tree continues from posterior end of main gut arm, extends posteriorly; minor gut sub-trees (not reaching edge of vitellarium near to body margin) arise between second and third, third and fourth, and fifth and sixth major sub-trees; inward gut diverticula include one long diverticulum either side protruding between germarium and either testis and reaching posteriorly to midway along inner testis margin and meeting (but not joining) medially, and two lateral diverticula anterior to germarium on either side, with or without minor branching, reaching close to midline, on right associated with right vitelline reservoir, on left dorsal to vas deferens; minor protrusions from left main gut arm invade inwards into terminal genitalia zone between first and second major sub-trees; no diverticula invading testicular material observed.

Testes two, opposite, with crenulated margins, situated at about second third of body, roughly of equal size; left testis 391–862 (606) × 298–821 (548); right testis 399–798 (598) × 339–892 (623); testicular muscle columns prominent, numerous. Post-testicular zone 23–38 (31) % of body length, 686–1770 (1211) long. Vasa efferentia narrow, arise from ventral testicular surface, multiple and apparently unequal (three associated with right testis and two with left in holotype, Fig. 3 ), short, connect to form a single duct which connects with vas deferens at level of posterior margin of germarium. Vas deferens prominent, proximal part densely coiled between germarium and genital pores, constrained laterally between vagina and left main gut arm, crosses midline dorsal to vagina, uterus, and distal tubular region of male tract, broadens distally to form thin-walled seminal vesicle immediately prior to proximal end of tubular male reproductive tract. Male reproductive tract tubular with thick walls and voluminous lumen, apparently constrained by thin membranes, surrounded by gland cells, bipartite: proximal part glandular, dextro-submedial, roughly longitudinal, 303–631 (509) × 112–256 (160); distal part tubular, semi-transverse, crosses midline, similar size to proximal part, 334–751 (593) × 87–292 (185) ( Fig. 4 ). Male pore ventral, sinistro-submedial, enclosed by main gut arms. Male copulatory organ apparently absent; no sclerites associated with terminal male genitalia. Spermatophores present in five specimens, four in one ( WAM V10849 ), two in one ( WAM V10848 ; subsequently dislodged during mounting), and one in three (not lodged, observed from wet mounts), fusiform capsule, attached to ventral surface adjacent to genital pores; capsule (excluding stalk) 270–374 (338) × 50–62 (56) .

Germarium medial, in mid-body, anterior to and of similar size to testes, roughly rhomboid, with lobulated margin, tapers anteriorly to give rise to oviduct, 244–729 (491) × 344–983 (714). Vagina singular, sinistro-submedial, apparently opens close to male pore, widens proximally to form seminal receptacle. Seminal receptacle oval, sinistro-submedial, anterior to germarium, 124–244 (183) × 54–150 (102). Vitellarium extensive, comprised of two fields of follicles; fields separate anterior to germarium, confluent posterior to germarium, united by transverse ducts; vitelline reservoirs two, anterior to germarium, right always prominent, left sometimes inconspicuous or obscured by vas deferens, give rise to branched vitelline ducts; vitelline ducts apparently follow gut closely, extend anteriorly only to second major gut sub-tree; vitelline follicles small, compact, dense, dispersed extensively throughout body, extend near to body margins, excluded from around pharynx, mouth and haptor, excluded from zone between main gut arms anterior to germarium. Oviduct short, simple, roughly medial. O¨otype prominent, tetrahedral, sinistro-submedial, adjacent and similar in size to seminal receptacle, 126–345 (261) × 70–161 (109). Uterus short, simple, continues anteriorly from o¨otype alongside vagina, apparently

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opens adjacent to male pore and vaginal pore. Eggs not observed in any specimen.

3.2.1.3. Remarks. The new species, Dermopristis pterophilus , is recognisable as a microbothriid by its simple haptor, and as a species of Dermopristis because it has two testes and lacks a male copulatory organ; it is entirely consistent with the revised concept of that genus provided by Whittington and Kearn (2011). Dermopristis pterophilus bears strong resemblance to both previously described species of Dermopristis : D. cairae and D. paradoxus (see Table 1). It is smaller than both those species and can otherwise be reliably distinguished from D. paradoxus only in that it lacks the strong, transverse, ventral tegumental ridges characteristic of that species. It is more easily distinguished from D. cairae by its oval body longer (3863 ± 110 μm) than wide (3085 ± 91 μm) vs an inverted heart-shaped body wider than long; presence vs absence of a seminal receptacle; and the position (terminal vs subterminal) and smaller size of the haptor relative to the body ( Table 1). The new species also differs from D. paradoxus and D. cariae in two fine details of the gut diverticula. First, the gut does not entirely encircle the testes as in both those species, and no diverticula were observed invading the testicular material, whereas these invasions were obvious ventrally in D. cairae and discovered dorsally following targeted sectioning in D. paradoxus ( Whittington and Kearn, 2011) . Second, a minor inward diverticulum of the gut dorsal to the proximal coils of the vas deferens is present but simple, with only two or three short branches in the new material ( Fig. 5 ) vs comparatively dendritic with multiple fine branches in D. cairae .

Figures

Fig. 2. Dermopristis pterophilus n. sp. holotype, ventral perspective. Abbreviations: dr, distal region of tubular male reproductive tract; gm, germarium; h, haptor; mf, muscle fibres; mp, male pore; ph, pharynx; pr, proximal region of tubular male reproductive tract; t, testis; vd, vas deferens; vf, vitelline follicles; vr, vitelline reservoir. Scale bar: 500 μm.

Fig. 3. Dermopristis pterophilus n. sp. holotype, ventral perspective. Abbreviations: b, bladder; bc, buccal cavity; dr, distal region of tubular male reproductive tract; g, gut; gm, germarium; h, haptor; m, mouth; mf, muscle fibres; mp, male pore; o, o¨otype; ph, pharynx; pr, proximal region of tubular male reproductive tract; sr, seminal receptacle; t, testis; vd, vas deferens; ve, vasa efferentia; vf, vitelline follicle; vr, vitelline reservoir. Scale bar: 500 μm.

Fig. 4. Dermopristis pterophilus n. sp. various soft parts, ventral perspective. (A) Reproductive system (excluding testes). (B) Spermatophores. (C & D) Pharynx with papillae retracted vs extended. Abbreviations: dr, distal region of tubular male reproductive tract; gm, germarium; gt1–3, first through third major gut sub-trees; mf, muscle fibres; mp, male pore; o, o¨otype; p, digitiform papillae; pr, proximal region of tubular male reproductive tract; sr, seminal receptacle; sv, seminal vesicle; v, vagina; vd, vas deferens; vid, vitelline duct; vr, vitelline reservoir. Scale bars: (A) 250 μm; (B) 300 μm; (C & D) 100 μm.

Fig. 5. Dermopristis pterophilus n. sp. detail of dendritic gut, ventral perspective. (A) Extensiveness and pattern of gut diverticula with position of the major gut subtrees extending from each side of the main lateral gut arms. (B) Fine details of minor gut diverticula dorsal to the coiled vas deferens. Abbreviations: g, gut; gt1–6, first through sixth major gut sub-trees; o, o¨otype; sr, seminal receptacle; u, uterus; v, vagina; vd, vas deferens. Scale bars: (A) 500 μm; (B) 100 μm.