Elpidium oxumae, 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 : 3-10

Elpidium oxumae n. sp.

Figs. 1–4

urn:lsid:zoobank.org:act:DA198C66-0CA0-4961-B0C9-B2CB1845BF4C

Diagnosis. Large-sized (length of male = 1007 µm; length of female = 1085 µm) species with rounded carapace (width/length ratio = 0.8; height/length ratio = 0.7). Brownish surface with sparse setae, normal pore canals and subtle ornamentation. Right valve overlapping left one. Sexual dimorphism pronounced: in dorsal and ventral views, posterior contour narrowly rounded in males, truncated in females. Ventral surface flat. In dorsal and ventral views, carapace symmetric on posterior contour morphology and greatest width. In left lateral view, external antero-ventral flange on left valve largely protruding; dorsal margin greatly arched, with greatest height in the middle; ventral margin almost straight. Hinge bar long (= length of dorsal margin) and crenulate along posterior third; anterior and posterior proto-teeth well-developed. Copulatory process on hemipenis without differentiation of distal glans and ejaculatory duct, hook-like; distal lobe elongated (basis width/length ratio = 0.4) with rounded apex and medial vestigial digital expansion; dorsal seta slightly longer than half the length of the distal lobe; lower ramus sinuous with acuminate apex.

Etymology. The species is named after Oxum, a deity considered queen of freshwaters according to afrobrazilian religions Umbanda and Candomblé. Although widespread in Brazil, these religions are particularly common in Bahia State, where the species was found.

Type Material. Holotype: a dissected male ( MZUSP 40271 ) 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 40272 ) stored like the holotype.

Paratypes: a male ( MZUSP 40277 ) and a female ( MZUSP 40273 ) dissected and stored like the holotype; three males ( MZUSP 40278 , MZUSP 40279 , MZUSP 40280 ) and three females ( MZUSP 40274 , MZUSP 40275 , MZUSP 40276 ) dried and coated for scanning electron microscopy stored in micropaleontological slides; males (~14) and females (~28) ( MZUSP 40281 ) kept whole in a vial with 70% ethanol .

Type Locality. Tank-bromeliads from Reserva Biológica da Peninha, S„o Francisco do Paraguaçu, Bahia, Brazil. Approximated geographic coordinates: 12º45′40.7″ S, 38º 52′ 16.5″ W. Material collected on July 25, 2007, by Carlos E. F. Rocha .

Description of the male.

Measurements. L: 1007 µm; W: 849 µm; H: 752 µm.

Carapace ( Fig. 1A, B, D ). Large (L = 1007 µm), with dorsal margin rounded and strongly arched. Surface with sparse setae, normal pore canals and subtle ornamentation. In dorsal and ventral views ( Figs. 1A, D ), carapace symmetric; posterior contour narrowly rounded. In ventral view, ventral surface flat. In left lateral view ( Fig. 1B ), right valve overlapping left one along all margins; carapace rounded in lateral view (height/length ratio = 0.7); anterior flange on left valve large.

Left valve internal view ( Fig. 1H–J ). Flange present along anterior, ventral and posterior margins, discontinued by bow funnel-shaped structure in the oral region; posterior flange with sparse setae and subtle inner list. Selvage well-developed along three sides of the left valve: weakly inwardly displaced along posterior and ventral margin, more strongly inwardly displaced along antero-ventral margin. Vestibule narrow in both, anterior and posterior regions. Hinge bar long (= length of dorsal margin); anterior proto-tooth thinner than posterior one; posterior prototooth pronounced. Muscle scars consisting of four spots, stacked in a slightly antero-ventral direction, the dorsal three spots elongated, the most ventral scar rounded and by far the smallest.

Right valve internal view ( Fig. 1E–G ). Anterior flange narrow, posterior flange absent. Selvage well-inwardly displaced along anterior margin, slightly along ventral margin, and almost nonexistent along caudal margin; both anterior and posterior regions with strong inner list, anterior one along selvage, forming a crenulate bow funnelshaped structure narrow in oral region. Calcified inner lamella present in anterior, ventral and posterior regions; Vestibule narrow in both, anterior and posterior regions. Muscle scars consisting of four spots, stacked in a slightly antero-ventral direction, the dorsal three spots elongated, the most ventral scar rounded and by far the smallest.

Antennula ( Fig. 2A ). Five-segmented. First segment slightly longer than wide and with a subapical expansion carrying numerous pseudochaetae on antero-dorsal margin. Second segment the longest, with numerous dorsal pseudochaetae and one long ventral plumose seta, sub-basically inserted and reaching mid-length of fourth segment. Third segment sub-quadrate, with a single dorso-apical seta reaching mid-length of fourth segment. Fourth segment long, partially subdivided in the middle, with two subequal dorso-medial setae, and one ventro-medial seta approximately equally long (all on segment 4a), and with three dorso-apical setae (two sub-equal and one long) and one long ventro-apical seta (on segment 4b). Fifth (terminal) segment short and narrow, apically with short Ya and three setae: two short and sub-equal and one longer, more than twice the length of Ya.

Antenna ( Fig. 2B ). Protopodite two-segmented: ring-shaped coxa plus long and arched basis with long dorsoapical pseudochaetae. Exopodite consisting of a short plate, carrying a long, two-segmented spinneret seta, second segment of this seta inserted perpendicularly on tip of longer first segment. Endopodite three-segmented. First segment rectangular, about 1.5 times as long as basal width, with a long ventro-apical seta, reaching end of second segment; dorsally with three well-delimited groups of pseudochaetae. Second segment about five times as long as basal width, with a continuous dorsal row of pseudochaetae; a short Y and a subequal seta inserted along midventral margin; sub-apically with two thin dorsal setae, one about half the length of the other and ventroapically with a biserrate claw, more than twice as long as the third segment. Third (terminal) segment small, sub-quadrate with vestigial seta and hyaline formation plus two thin apical biserrate claws and one subapical pectinate claw with a row of strong teeth.

Mandible, with coxa ( Fig 2D —illustration of a female specimen) and a palp ( Fig. 2E ). Coxa long, internally with eight strong teeth, plumose and thin seta, three interdental setae, one modified, spoon-shaped (X1) and two thin with usual apex (X2, X3), three interdental spines and a single plumose sub-apical seta. Palp four-segmented, with basis and three endopodal segments. Basis set with two large, plumose setae, one about half the length of the other, and a respiratory plate (the exopodite) with three long and broad setae plus one short reflexed seta, all set with setules. First endopodal segment with two setae, one long, plumose and one short. Second endopodal segment with five setae, three long ones and two thin ones, the latter subequal in length. Third endopodal (terminal) segment small, sub-quadrate, with three apical setae, two long of similar length and one shorter than the other two.

Maxillula ( Fig. 2F —illustration of a female specimen). Consisting of a basis, a large respiratory plate, three endites and a one-segmented palp. First endite with three subequal, slender setae. Second and third endites each with three subequal, slender setae and two spatulate claws. Palp with four pseudochaetae rows (not visible on the appendage illustrated, but confirmed present for the species), vestigial seta and two long, slender apical setae. Respiratory plate (exopodite) with 16 rays plus one reflexed seta, all set with setules.

First thoracic limb ( Fig. 3A ). Basis broad and slightly arched with one ventral plumose long seta, two short ventro-apical setae and a single long dorsal seta (exopodite?) reaching second endopodial segment. Endopodite three-segmented. First segment the longest with numerous pseudochaetae on both, dorsal and ventral margins and one stout ventro-apical seta reaching tip of second endopodial segment. Second segment with length greater than width and without setae. Third segment with length similar to that of second endopodial segment and without setae, but with distal claw long and arched, swollen basis carrying a vestigial seta.

Second thoracic limb ( Fig. 3B ). Larger than first thoracic limb. Basis with ventral medium-sized plumose seta, single ventro-apical long plumose seta and one dorsal (exopodite?) long plumose seta. First endopodial segment with ventro-apical seta longer than second endopodial segment. Second and third segment subequal and without setae. Distal claw on third segment longer and slightly more arched than equivalent claw on first thoracic limb; swollen basis also carrying a vestigial seta.

Third thoracic limb ( Fig. 3C ). Basis broad and slightly arched with two ventral, slender setae: one medial and one apical and a dorsal plumose seta (exopodite?), shorter than exopodite on first and second thoracic limbs. Endopodite three-segmented. First endopodial segment the longest, ventrally with a row of long pseudochaetae, dorso-apical with one group of pseudochaetae and apically with a short row of pseudochaetae and a slender pappose seta longer than the second segment. Second and third endopodal segments shorter than equivalent segments on first and second thoracic limbs, with ventral and apical rows of pseudochaetae and no setae. Distal claw on third segment slender and long, swollen basis also carrying a vestigial seta.

Hemipenis ( Fig. 3D ). With broad, rounded and sclerotized muscular body. Main appendage elements consisting of a copulatory complex (cop plus LR) and a DL; cop hook-like without differentiation between distal glans and ejaculatory duct. LR sinuous with acuminate apex. DL with length greater than width (basis width/lobe length ratio = 0.4), a rounded apex and a medial vestigial digital expansion; ds slender, reaching just over half the length of the DL; fl with two setae and numerous pseudochaetae.

Description of female.

Measurements. L: 1085 µm; W: 957 µm; H: 791 µm.

Carapace ( Fig. 4A–C ). Large (L = 1085 µm), with dorsal margin rounded and strongly arched. Strong sexual dimorphism, with major width displaced posteriorly due to externally visible brooding chamber; posterior contour truncate in dorsal and ventral views. Left lateral view with dorsal margin highly arched, ventral margin straight and right valve overlapping left one along all margins.

Antenna, terminal segment ( Fig. 2C ). Similar to equivalent in males, but with vestigial seta, hyaline formation and three biserrate claws instead of two biserrate and one pectinate claws.

Abdomen ( Fig. 3E ). End of body rounded and large with one stiff, dorso-medial spine-like seta, and genital and furcal lobes. Genital lobe rounded, rigid, with internally trabeculae and muscles; fl rounded but not rigid, with three sub-equal pappose setae and numerous pseudochaetae.

Differential diagnosis. Elpidium oxumae n. sp., E. martensi and E. purperae are the only three Elpidium species with reversed overlap (right valve overlapping left valve) currently known. However, they can be distinguished in several ways. Comparing E. oxumae n. sp. to E. martensi in left lateral view, right valve overlaps left one from anterior to posterior regions throughout the whole dorsal margin extension in E. oxumae n. sp. This characteristic is absent in E. martensi . In addition, the external antero-ventral flange is much more evident in E. oxumae n. sp.; in internal view, the hinge bar is well-developed, with pronounced proto-teeth on E. oxumae n. sp.. Concerning sexual appendages, E. oxumae n. sp. has a DL on the hemipenis somewhat similar to that of E. martensi . However, the cop is shorter and the apex of the LR is much more rounded in E. martensi . All three main hemipenis structures: cop, DL and LR are distinct also from those observed in E. purperae . E. oxumae n. sp. has rounded DL, a LR with acuminate apex and an elongated hook-like cop. E. purperae on the other hand, has a very elongated and acuminate DL, a rounded LR and a short hook-like cop.

Distribution. The species is currently known only from tank-bromeliads in three different locations in the state of Bahia, Brazil: São Francisco do Paraguaçu (type locality), Serra da Jacobina (approximate coordinates 11° 14′ S, 40°30′ W) and Ilhéus (approximate coordinates 14° 47′ S, 39° 02′ W).

Figures

FIGURE 1. Elpidium oxumae n. sp., male, carapace.A—dorsal view (paratype, MZUSP 40280); B—left lateral view (paratype, MZUSP 40278); C—left lateral view, detail of antero-ventral region, showing external flange and ornamentation (paratype, MZUSP 40278); D—ventral view (paratype, MZUSP 40279); E—right valve, internal view (paratype, MZUSP 40277); F—right valve, internal view, detail of antero-ventral region (paratype, MZUSP 40277); G—right valve, internal view, detail of posteroventral region (paratype, MZUSP 40277); H—left valve, internal view (paratype, MZUSP 40277); I—left valve, internal view, detail of antero-ventral region (paratype, MZUSP 40277); J—left valve, internal view, detail of postero-ventral region (paratype, MZUSP 40277). Scale bars: A, B, D, E, H—100 µm; C, F, G, I, J—30 µm.

FIGURE 2. Elpidium oxumae n. sp., A, B, E, male, C, D, F, female, appendages.A—antennula (holotype, MZUSP 40271); B— antenna (holotype, MZUSP 40271); C—antenna, terminal segment (allotype, MZUSP 40272); D—mandible, coxa (allotype, MZUSP 40272); E—mandible, palp (holotype, MZUSP 40271); F—maxillula (allotype, MZUSP 40272). Scale bars: A, B, D–F—0.1 mm; C—0.03 mm.

FIGURE 3. Elpidium oxumae n. sp., A–D, male, E, female, appendages.A—first thoracic limb (holotype, MZUSP 40271); B— second thoracic limb (holotype, MZUSP 40271); C—third thoracic limb (holotype, MZUSP 40271); D—hemipenis (holotype, MZUSP 40271); E—abdomen (allotype, MZUSP 2072). Scale bars: A–E—0.1 mm.

FIGURE 4. Elpidium oxumae n. sp., female, carapace. A—dorsal view (paratype, MZUSP 40276); B—left lateral view (paratype, MZUSP 40274); C—ventral view (paratype, MZUSP 40275); D—right valve, internal view (paratype, MZUSP 40273); E—right valve, internal view, detail of antero-ventral region (paratype, MZUSP 40273); F—right valve, internal view, detail of postero-ventral view (paratype, MZUSP 40273); G—left valve, internal view (paratype, MZUSP 40273); H—left valve, internal view, detail of antero-ventral (paratype, MZUSP 40273); I—left valve, internal view, detail of bow funnel-shaped structure (paratype, MZUSP 40273); J—left valve, internal view, detail of postero-ventral region (paratype, MZUSP 40273); Scale bars: A–D, G—100 µm; E, F, H, J—30 µm; I—10 µm.