Elpidium cordiforme, Pereira & Rocha & Martens & Pinto, 2023

Pereira, Julia S., Rocha, Carlos E. F., Martens, Koen & Pinto, Ricardo L., 2023, Six new species of Elpidium Müller, 1880 (Podocopida: Limnocytheridae) from Eastern Brazil, Zootaxa 5258 (1), pp. 1-38 : 10-15

Elpidium cordiforme n. sp.

Figs. 5–8

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Diagnosis. Medium-sized Elpidium (length of male = 886 µm; length of female = 911 µm), with carapace elongated (width/length ratio = 0.8; height /length ratio = 0.5). Surface brownish with sparse setae, normal pore canals and subtle ornamentation. Left valve overlapping right one. Strong sexual dimorphism: posterior contours in dorsal and ventral views rounded with subtle beak in males, markedly invaginated in females. Ventral surface flat. In dorsal and ventral views, carapace symmetric. In right lateral view, external flange outstanding, dorsal margin arched, ventral margin nearly straight, postero-ventral region angulated. Hinge bar long (more than 2/3 of length of dorsal margin); anterior proto-tooth smooth and thin; posterior proto-tooth thin and slightly crenulate. Copulatory process on hemipenis without differentiation of distal glans and ejaculatory duct, with distal region curled, apex thin and elongated. Distal lobe elongated (basis width/lobe length ratio = 0.5) with rounded apex and long basal (finger-type) digital expansion, giving a distinct bi-lobed impression; dorsal seta reaching about half-length of distal lobe. Lower ramus with apex triangular and acuminate.

Etymology. The specific epithet “cordiforme” is a reference to the heart-shaped contour of the carapace in dorsal and ventral views.

Type Material. Holotype: a dissected male ( MZUSP 40282 ) with valves dried and coated for scanning electron microscopy stored in a micropaleontological slide and appendages mounted in a sealed slide with glycerin.

Allotype: a dissected female ( MZUSP 40283 ) stored like the holotype.

Paratypes: a male ( MZUSP 40290 ) dissected and stored like the holotype; three males ( MZUSP 40287 , MZUSP 40288 , MZUSP 40289 ) and three females ( MZUSP 40284 , MZUSP 40285 , MZUSP 40286 ) dried and coated for scanning electron microscopy stored in micropaleontological slides; males (~96) and females (~117) ( MZUSP 40291 ) kept whole in a vial with 70% ethanol .

Type Locality. Tank-bromeliads from Domingos Martins, Espírito Santo, Brazil. Approximated geographic coordinates: 20º24′55.2″ S, 40º51′45.7″ W. Material collected on Nov. 11, 2006, by Carlos E. F. Rocha .

Description of the male.

Measurements. L: 886 µm; W: 744 µm; H: 483 µm.

Carapace ( Figs. 5A–F ). Medium-sized (L = 886 µm). Surface with sparse setae, normal pore canals and subtle ornamentation. In dorsal and ventral views ( Fig. 5A–C ), posterior contour rounded with subtle beak. In dorsal view, carapace symmetric. In ventral view, ventral surface flat. In right lateral view ( Figs 5E–F ), left valve overlapping right one in dorsal and anterior margins; posterior margin subtly angulated; carapace elongated (height/length ratio = 0.5); external flange outstanding on anterior region; dorsal margin arched; ventral margin nearly straight.

Left valve ( Fig. 5G–I ). In internal view with flange present along antero-ventral region, absent along ventral and posterior regions. Selvage well marked along anterior region, forming narrow bow funnel-shaped structure in oral region, subtly in ventral region, running along valve margin at posterior end. Calcified inner lamellae and vestibules narrow on both anterior and posterior region.

Right valve ( Fig. 5J–L ). In internal view with flange present along anterior, ventral and posterior margins, discontinued by bow funnel-shaped structure in oral region; broad along anterior; narrow, filled with sparse setae along posterior margin. Selvage well marked from the anterior to posterior tooth, forming bow funnel-shaped structure in oral region. Calcified inner lamella narrow anteroventrally, very narrow medio-ventrally and posteroventrally. Vestibule narrow in both anterior and posterior regions. Hinge bar long, more than 2/3 of length of dorsal margin. Anterior and posterior teeth thin; posterior one slightly crenulate.

Hemipenis ( Fig. 7D ). With broad, rounded and sclerotized muscular body. Main elements: copulatory complex (cop plus LR) and DL; cop without differentiation of distal glans and ejaculatory duct, curled near distal region, with apex thin and elongated. LR with thin basis: apex triangular and acuminate. DL elongated (basis width/lobe length ratio = 0.5) with rounded apex: digital expansion well-developed, giving a clear bi-lobed impression; ds slender, reaching about DL mid-length; fl with pair of setae and numerous pseudochaetae.

Other appendages as in Elpidium oxumae n. sp. ( Figs. 6A–F , 7A–C ).

Description of female.

Measurements. L: 911 µm; W: 797 µm; H: 553 µm.

Carapace ( Fig. 8 A-E). Medium-sized (L = 911 µm). Strong sexual dimorphism: posterior contour in dorsal and ventral views markedly invaginated; major width displaced posteriorly due to brooding chamber. In right lateral view, left valve overlapping right one along dorsal and anterior margins; dorsal margin arched; ventral margin nearly straight. In anterior region, external flange pronounced; postero-ventral margin strongly angulated.

Antenna, terminal segment ( Fig. 6C ). As in the male, except for the presence of three biserrate claws instead of two biserrate and one pectinate claws.

Abdomen ( Fig. 7E ). End of body rounded and large, with spine-like seta, and genital and furcal lobes. Spinelike seta stiff, in dorso-medial position; gl rounded, rigid, and with trabeculae internally; fl rounded but not rigid, with three equal-length pappose setae and numerous pseudochaetae.

Other appendages as in Elpidium oxumae n. sp. ( Figs. 6A, D–F , 7A–C ).

Differential diagnosis. Elpidium cordiforme n. sp. is morphologically quite distinct from all other Elpidium species described so far, both in carapace and the male sexual appendage. Females exhibit a singular invagination at the posterior end of carapace, forming a heart-shape in dorsal and ventral views. Besides this, the postero-ventral margin is angular in right lateral view, instead of the general rounded shape commonly observed. Main structures of hemipenis (DL, cop and LR) are also unique. Cop exhibits coils near distal region, a peculiar shape so far. DL, in particular, has a rounded apex and quite long finger-like expansion, giving a bi-lobed impression. Elpidium merendonense also presents a somewhat similar digital expansion.

Distribution. The species is currently known solely from tank-bromeliads in the type locality.

Remarks. The sexual dimorphism in the posterior part of the carapace is very pronounced in this species, to the extent that there might be some doubt whether or not males and females described here are indeed conspecific. However, based on the co-occurrence of the sexes we here maintain that they do belong to the same species.

Figures

FIGURE 5. Elpidium cordiforme n. sp., male, carapace. A—dorsal view (paratype, MZUSP 40289); B—dorsal view, detail of posterior region (paratype, MZUSP 40289); C—ventral view (paratype, MZUSP 40287); D—right lateral view (paratype, MZUSP 40288); E—right lateral view, detail of posterior region (paratype, MZUSP 40288); F—right lateral view, detail of anterior region (paratype, MZUSP 40288); G—left valve, internal view (holotype, MZUSP 40282); H—left valve, detail of posterior region (holotype, MZUSP 40282); I—left valve, detail of anterior region (holotype, MZUSP 40282); J—right valve, internal view (holotype, MZUSP 40282); K—right valve, detail of anterior region (holotype, MZUSP 40282); L—right valve, detail of posterior region (holotype, MZUSP 40282). Scale bars: A–D, G, J—200 µm; E, H, I, K, L—100 µm; F—50 µm.

FIGURE 6. Elpidium cordiforme n. sp.,A, B, D–F, male, C, female, appendages.A—antennula (paratype, MZUSP 40290); B— antenna (paratype, MZUSP 40290); C—antenna, terminal segment (allotype, MZUSP 40283); D—mandible, coxa (paratype, MZUSP 40290); E—mandible, palp (paratype, MZUSP 40290); F—maxillula (paratype, MZUSP 40290). Scale bars: A, B, D, E—0.05 mm; C—0.2 mm; F—0.1 mm.

FIGURE 7. Elpidium cordiforme n. sp., A, C, D, male, B, E, female, appendages. A—first thoracic limb (paratype, MZUSP 40290); B—second thoracic limb (allotype, MZUSP 40283); C—third thoracic limb (paratype, MZUSP 40290); D—hemipenis (paratype, MZUSP 40290); E—abdomen (allotype, MZUSP 40283). Scale bars: A–C—0.05 mm; D—0.2 mm; E—0.1 mm.

FIGURE 8. Elpidium cordiforme n. sp., female, carapace. A—right lateral view (paratype, MZUSP 40285); B—right lateral view, detail of posterior region (paratype, MZUSP 40285); C—right valve, detail of anterior region (paratype, MZUSP 40285); D—dorsal view (paratype, MZUSP 40286); E—ventral view (paratype, MZUSP 40284); F—left valve, internal view (allotype, MZUSP 40283); G—right valve, internal view (allotype, MZUSP 40283); H—right valve, detail of anterior region (allotype, MZUSP 40283); I—right valve, detail of posterior region (allotype, MZUSP 40283). Scale bars: A, D–G—200 µm; B—100 µm; C, H, I—50 µm.