Temnosewellia vietnamensis, Damborenea & Brusa, 2009

Damborenea, Cristina & Brusa, Francisco, 2009, A new species of Temnosewellia (Platyhelminthes, Temnocephalida) ectosymbiont on Villopotamon thaii (Crustacea, Decapoda, Potamidae) from Vietnam, Zoosystema 31 (2), pp. 321-332 : 325-326

Temnosewellia vietnamensis n. sp. ( Figs 1-9 )

TYPE MATERIAL. — Holotype: wholemount specimen ( MNHN HEL 42 ) . Paratypes: 2 specimens sagittaly sectioned, 1 specimen frontally sectioned, 1 cirrus in polyvinyl-lactophenol ( MLP 5744 ) ; 1 specimen transversally sectioned ( MNHN HEL 43 - HEL 50 ) .

TYPE HOST. — Villopotamon thaii Dang & Ho, 2003 . Site: external surface of the carapace.

TYPE LOCALITY. — Stream at Bana Nature Reserve (Quangnam province, Vietnam).

OTHER MATERIAL EXAMINED. — Same data as type material, 3 stained wholemount specimens, 3 wholemount specimens in polyvinyl- lactophenol, unhatched eggs, 3 SEM specimens and 1 cirrus mounted on stubs and coated with gold, and 32 specimens in 70% ethanol ( MLP 5745 , 5746 , 5747 ) ; 8 wholemount specimens ( MNHN HEL 42 ) .

ETYMOLOGY. — The specific name refers to Vietnam, where the specimens were collected.

DESCRIPTION

External characteristics

Body about 2.5 mm (1.8-3.3 mm, 7) long without tentacles, and about 2.0 mm (1.5-2.6 mm, 7) wide; rounded to oval. Black pigment confined to eyes. Posterior adhesive disc pedunculate: disc diameter 809 µm at rim (624-1152 µm, 7), disc peduncle about 339 µm in diameter (240-456 µm, 7) ( Figs 1A ; 2 ; 3B ). Epidermis thin, syncytial and uncilliated. Through SEM and staining with SN the tentacular and peduncular syncytia were evident ( Fig. 3 C-E). The posterior border of the postentacular plate was not evident.

Alimentary system

Mouth mid-ventral, between the first and second quarters of body, surrounded by a muscular sphincter. Pharynx wider than long, 460 µm (340-700 µm, 6) long, 552 µm (440-650 µm, 6) wide, with a large sphincter; esophageal glands at its base. Intestine saccular, with septa (evident in the sections) in adults; intestinal walls very thick.

Paranephrocites not evident.

Excretory system

Excretory pores lateral to mouth, outside the postentacular syncityal plates. Major excretory ducts inconspicuous.

Glands

Rhabdite glands large, numerous, in lateral fields of the body, forming bunches, extending on the sides of the intestinal sac, with conspicuous rhabdite tracts ( Figs 1A ; 2 ). Cyanophilus glands inconspicuous in wholemount specimens, evident in the sections, separated in the parenchyma and located between the rhabdite glands. Two Haswell’s cells in front of the eyes and the brain transverse band, showing little affinity with hematoxylin. Shell gland cells prominent, in lateral fields discharging to gonopore.

Figures

FIG. 1. — Temnosewellia vietnamensis n. sp.: A, drawing of a specimen in ventral view;B, reconstruction of the male and female genital systems.Abbrevations: at, anterior testicle; c, cirrus; e, eye; ea, excretory ampullae;es, ejaculatory sac; g, glands;ga, genital atrium; go, gonopore; hc, Haswell’s cells; i, intestine; o, ovary; pb, prostatic bulb; pt, posterior testicle; rg, rhabdite glands; sgt, shell glands tracts; sr, seminal receptacle; sv, seminal vesicle; v, vitellaria; va, vagina; vr vesicula resorbens. Scale bars: A, 1000 μm; B, 300 μm.

FIG. 2. — Temnosewellia vietnamensis n. sp., photomicrographs of wholemount. Scale bar: 400 μm.

FIG. 3. — Temnosewellia vietnamensis n. sp.: A, B, SEM micrographs of whole specimens;C-E, details of the syncytial plates; F, detail of the gonopore. Black arrowheads show excretory pore, white arrowheads show the border of the postentacular and body syncytial plates. Scale bars: A, 200 μm; B, 500 μm; C, D, 50 μm; E, 100 μm; F, 20 μm.

FIG. 4. — A, B, Temnosewellia vietnamensis n. sp., specimen frontally sectioned showing the arrangement and size of the genital structures, comprised between the posterior testicles, posterior wall of the intestine and the adhesive disc, and the conspicuous vesicula resorbens indenting the intestinal wall. Abbreviations: ad, adhesive disk; c, cirrus; ga, genital atrium; i, intestine, o, ovary; pt, posterior testicle, vd, vasa deferentia; vr vesicula resorbens. Scale bars: 200 μm.

FIG. 5. — Temnosewellia vietnamensis n. sp., egg capsules: A, B, general views (binocular microscope); C-F, details of the opercular plates (SEM). White arrowheads show the opercular plates; black arrowheads show the filament. Scale bars: 100 μm.

FIG. 6. — Temnosewellia vietnamensis n. sp., cirrus, detail of the distal extremity (A) and general view (B). Scale bars: 100 μm.

FIG. 7. — Temnosewellia vietnamensis n. sp., the cirrus introvert observed in different focusing planes with the Nomarski differential interference contrast (DIC) microscopy. Focus series captured from the top left hand corner to the bottom right hand corner. Scale bar: 25 μm.

FIG. 8. — Temnosewellia vietnamensis n. sp., the cirrus introvert observed with the Nomarski differential interference contrast (DIC) microscopy showing the unspined distal region. Abbreviations: s, stylet; si, spined introvert; udr, unspined distal region. Scale bar: 50 μm.

FIG. 9. — Temnosewellia vietnamensis n. sp., cirrus seen with SEM: A, detail of the introvert; B, detail of the thickened ring; C, frontal view of the introvert; D, detail of the rows of spines and their insertion points. White arrowheads show the thickened ring. Scale bars: A, 10 μm; B, 2 μm; C, D, 5 μm.