Elpidium alarconi Mesquita-Joanes, Gálvez, Palero & Rueda, 2025, sp. nov.
Creators: name: Mesquita-Joanes, Francesc
name: Gálvez, Ángel
name: Palero, Ferran
name: Rueda, Juan
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Ostracoda
Podocopida
Limnocytheridae
Elpidium
Elpidium alarconi

description: Elpidium alarconi sp. nov.
Figs 1, 2, 3, 4, 5, 6, 7
Type locality.
Rancho Baiguate (La Joya Sector, Jarabacoa, República Dominicana) 19°6'49"N, 70°37'8"W, 530 m a. s. l., sampled on 7/2/2019 and 12/4/2021 by J. Rueda and P. Alarcón. Tank bromeliads growing at the base of several tree trunks in a secondary natural forest, with a wide cover, and presence of domestic animals (horses, dogs) in the vicinity, near the Baiguate River.
Type material.
Holotype • 1 adult ♂; soft parts dissected and stored on a permanent microscopic slide, valves dry in a micropaleontological slide (MUVHNZY 0021). Allotype • 1 adult ♀; soft parts dissected and stored on a permanent microscopic slide, valves dry in a micropaleontological slide (MUVHNZY 0022). Paratypes • 10 adult ♂♂ and 17 adult ♀♀. Six of the males (MUVHNZY 0023 - MUVHNZY 0026, MUVHNZY 0035, MUVHNZY 0036) dissected and stored as the holotype, valves coated and used for SEM; one male (MUVHNZY 0027) used in toto for SEM, after applying critical-point drying (CPD), and stored in a micropaleontological slide; another male (MUVHNZY 0039) with valves untreated and bodies (CPD and coated) in a micropaleontological slide. Seven females (MUVHNZY 0028 -0033, MUVHNZY 0037) dissected and stored as the holotype, valves coated and used for SEM; another female (MUVHNZY 0038) with valves untreated and bodies (CPD and coated) in a micropaleontological slide. Two adult males and six females stored in toto in ethanol 96 % (MUVHNZY 0034). Soft body remains of three adult females used for DNA extraction stored in ethanol (codes MUVHNZY 0040 -0042).
Diagnosis.
Elpidium species of intermediate size (~ 700–800 μm), with a dark-colored carapace. Females slightly longer and wider than males, and with a truncate posterior margin in dorsal view; males with a barely obtuse posterior margin. Valves (quasi-) symmetric in dorsal view. Surface of valves covered with minute and shallow pits. LV embracing RV along all free margins. Hinge protodont, with a strongly built bar in the RV, including one (proto-) tooth at each extreme of the bar. LV with a hinge groove. A 1 apparently six-segmented (i. e., segments 4 a and 4 b partially separated). DL of male Hp with a long digital expansion, CoP L-shaped, with tip not subdivided, and LR very slender (thinner than CoP), L-shaped and with a pointed tip.
Description.
Male. Adult shell large (L> 0.7 mm), according to size groups established for limnocytherids s. l. by Gidó et al. (2007), but of intermediate size compared to other Elpidium species. Cp subovate in dorsal and ventral view (Fig. 1 A, B). Maximum width slightly displaced to posterior part, at ~ 45 % of total length. Cp in dorsal view: anteriorly pointed, barely acute; posteriorly bluntly pointed, obtuse, with more rounded outline than anterior margin. Valves almost symmetrical in dorsal view; LV slightly longer and embracing RV along all free margins (Fig. 1 B). Valves elongate in lateral view (Fig. 1 C, D), posterior margin broadly rounded, anterior margin infracurvate, i. e., narrowly rounded towards anteroventral region. Maximum length at ~ 33 % of maximum height. Ventral margin slightly convex in lateral view, flat in ventral (Fig. 1 B) and frontal (Fig. 5 A) views. Surface of valves smoothly punctate, overall covered with minute foveolae and sparsely with normal (type- A 2) pores, many of which hold a sensory seta (Fig. 1 A, C, D, I – K). These foveolae more conspicuous, denser, and deeper near anterior margin of valves, in a narrow beak-like zone (Fig. 1 K). This zone partially corresponds internally to the area of the inner lamella between outer margin and selvage (Fig. 1 E, F). Calcified inner lamella wider anteriorly (~ 12 % of valve L) than posteriorly (6 % of valve L). Selvage strongly built in the RV (Fig. 1 F, H), anteriorly positioned approximately half way between anterior margin and inner margin of calcified inner lamella. Hinge protodont, sensu Danielopol et al. (2014). RV dorsally with a hinge bar (Fig. 1 H), showing anterior and posterior prototeeth. LV with a hinge groove (Fig. 1 G), anteriorly with enlarged socket. Both valves antero-ventrally with selvage protruding towards external margin, building the typical funnel-like structure of Elpidium ostracods at mouth position. Four large adductor muscle scars (Fig. 1 F, L) aligned in a slightly oblique row (leaning 30 ° from vertical axis towards anterior part, from top to bottom), located just in front of central area of valves. Three of these scars elongate, bottom one subovate. Another smaller, rounded scar situated in front of top one of the four central muscle scars. Both valves postero-ventrally with a row of submarginal (type- A 2) pores and setae located in the peripheral part of the marginal infold (Fig. 1 I, J). Carapace colored dark brown.
A 1 (Figs 2 A, 3 A – D). Apparently six-segmented, i. e., with clear separation between segments 4 a and 4 b under standard microscope, but this separation weaker than other segments (Fig. 3 A). Separation not observed under UV-light in a fluorescence microscope, compared to other segmentation (Fig. 3 B). This separation observed only in the internal part of fourth segment under SEM, but not in the external part (Figs 3 C, D, 5 E). First segment trapezoidal, strongly built, dorsally with a subapical subtriangular expansion, partially covered with pseudochaetae. Second segment elongate, more than thrice longer than wide, dorsally covered with pseudochaetae along its margin, ventrally with a long plumose seta, attached slightly behind middle of segment, and reaching mid-length of fourth segment. Third segment rectangular, with a seta at its dorso-apical margin, this seta slightly longer than next segment. Segment 4 a rectangular, ~ 2 × longer than wide, dorsally with two small apical setae (not attaining the middle of next segment) and ventrally one seta as long as next segment. Fifth segment (segment 4 b) dorsally with three apical setae of varied length; longest one attaining one third of Ya aesthetasc, second longer one as long as last segment, smallest one ~ 1 / 2 the length of last segment. Ventrally with a long apical seta, surpassing the middle of Ya aesthetasc. Last (sixth) segment with three apical setae and Ya aesthetasc. One seta as long as Ya, another slightly longer than last two segments, another one slightly longer than last three segments.
A 2 (Fig. 2 B). Protopod two-segmented. First segment short and ring-shaped, second segment elongate and smoothly curved,> 2.5 × longer than wide. Exopod with a very small seta and a spinneret seta, not surpassing tip of claws. First segment of endopod subquadrate, ventrally with an apical long seta, ~ 2 / 3 of the length of next segment. Second endopodal segment elongate, ~ 5 × longer than wide. Ventrally with one small seta and Y aesthetasc, situated slightly in front of mid-length of segment. This small seta slightly shorter than aesthetasc. Another large and thick seta attached to ventro-apical margin, together with a minute seta (Fig. 5 F, as in the female: Fig. 3 E). Dorsally with two subapical short setae, one ~ 1 / 2 the length of the other. Last segment subquadrate, with three claws, shortest and ventral one pectinated with a row of strong teeth (Fig. 5 F). A very small hyaline formation located ventro-apically, at the base of pectinated claw, but together with a minute seta (as in the female: Fig. 3 F).
Md (Fig. 2 C). Coxa slender, with curved posterior half and straight anterior one. Distally with eight teeth, progressively smaller from anterior (dorsal) to posterior (ventral) ones, most of them bicuspidate and / or with adjacent interdental spines and setae (X-setae). Dorsally with large serrate seta, not reaching the base of dorsal teeth. Ventrally with one small plumose seta, slightly longer than ventralmost small tooth. Md-palp four-segmented and curved. First segment (basis) with two ventral plumose setae, one ~ 2 / 3 the length of the other. Dorsally with exopod (respiratory plate) with three broad rays and a small reflected ray. Second segment (first endopodal segment) with two ventro-apical plumose setae, one of them half the length of the other. Third segment subquadrate, ventrally holding an apical long smooth seta, dorsally with three long apical smooth and thin setae, together with a thicker plumose seta, all of similar length. Last segment small and subquadrate, with three terminal thin setae of similar length, one of these claw-like, the other two smooth.
Mx (Fig. 2 D). Elongate, subrectangular protopod. Exopod (respiratory plate) with 16 distal unequal rays and a proximal reflexed ray. Endopod with three endites and a palp. First endite with three subequal setae. Second and third endites each with two spoon-shaped (spatulate), claw-like setae, and three smooth, thin setae. Palp unsegmented, distally with two long plumose setae, longer than tip of endite setae, plus a minute subapical dorsal seta.
T 1 (Figs 4 A, 5 H). Four-segmented. First segment the longest. Ventrally with a large seta, situated well behind mid-length of segment. Dorsally with proximal long seta, slightly surpassing distal margin of segment. Dorso-apically with two subequal knee-setae. Second segment elongate, 6 × longer than wide, ventrally with strong apical seta, as long as next segment. Third segment without setae. Fourth segment with apical claw bearing a minute seta at its swollen base, and as long as third segment.
T 2 (Figs 4 B, 5 H). Larger than T 1 and four-segmented. First segment strong, bearing ventrally a subproximal long setae, attaining distal edge of segment. Dorsally with one medial long seta, surpassing distal margin of segment, and an apical knee-seta, ~ 1 / 2 the length of previous seta. Second segment slender and long, ventrally with apical strong seta, almost as long as next segment. Third segment without setae. Fourth segment similar to previous one but slightly shorter and with an apical claw. This claw as long as third segment, and with a proximal minute seta.
T 3 (Figs 4 C, 5 H). Larger than T 2 and four-segmented. First segment ventrally with a proximal large seta, 2 / 3 as long as segment. Dorsally with a thin medial seta, attaining distal edge of segment, and a small distal knee-seta, ~ 1 / 2 the length of previous seta. Second segment long,> 8 × longer than wide, and with an apical strong seta, ~ 2 / 3 the length of next segment. Third segment devoid of setae and 3 × longer than wide. Last segment similar but slightly smaller than previous one, bearing a very long claw, longer than second segment, and with a minute seta at its base.
Hp (Figs 4 D, 5 A – D). Large sclerotized and muscular body with DL, distal seta, CoP and LR. DL with a long basal digital expansion. Width of DL, including digital expansion, longer than its length. This expansion flexible at its tip, so that in some slide preparations for optical microscopy, it can be distally folded. Distal seta shorter than digital expansion. DL with lateral margins almost parallel in its mid length, but converging in a subtriangular, pointed shape at its distal part (Figs 4 D, 5 B). CoP L-shaped, progressively narrowing towards the tip (Fig. 4 D), without separation between distal glans and ejaculatory duct (Fig. 5 C, D). LR slender, very thin, L-shaped and with a finely pointed tip (Figs 4 D, 5 C, D). Depending on the position of LR in slide preparations for optical microscopy, L-shape might not be seen clearly in one or both hemipenes. A slight difference between left and right LR shape observed in the development of the L-angle, somehow resembling a piolet with a small adze rather than an L (Fig. 5 C, D).
CR with one pair of intermediate-size, plumose setae and numerous pseudochaetae (Figs 4 D, 5 B).
Labrum (Fig. 5 G) large, subquadrate in ventral view. Anteriorly and ventro-laterally with arrays of long pseudochaetae. Posteriorly, near the mouth entrance, with two submarginal pappose setae and a marginal row of short setulae forming an apparently serrated margin.
Description.
Female (only sexually dimorphic features described) (Figs 6, 7). Cp slightly longer, distinctly wider, and slightly more asymmetric than male, posteriorly not pointed but truncate or even slightly cordate in dorsal and ventral views (Fig. 6 A, B). These Cp differences between male and female correspond to species group A, according to Danielopol et al. (2014). In lateral external view (Fig. 6 C, D), female valves with a straight ventral margin and a less arched posterior margin than males. In internal view, more developed socket-like hinge structures posteriorly in the inner margin of both valves (Figs 6 E – H, 7 B, C), and posteroventrally wider distance between outer margin and external outline, due to the wider development of valves in this area (Fig. 6 E, F, I, J). Posterior part of female hinge bar also with stronger tooth, coupled to a tooth-like pointed inner margin in RV (Fig. 6 F, H), not observed in male valves (Fig. 1 H).
A 2 (Figs 3 E, F, 4 E). None of the three claws in distal segment pectinated. Y aesthetasc smaller than in male, i. e., of similar length than adjacent seta.
Abdomen (Fig. 7). Centrally with a spine-like seta in dorsal position. Genital lobes semicircular, with internal trabecula and showing internal tubes. CR with two equal adjacent plumose setae in an apical position plus a separate stronger plumose seta, laterally situated, close to genital lobe.
Measurements.
Male. L: 739 μm (671–778, n = 7); W: 559 μm (524–596, n = 5); H: 423 μm (418–430, n = 3). Female. L: 773 μm (711–836, n = 9); W: 645 (556–711, n = 5); H: 422 (373–476; n = 4).
Differential diagnosis.
Other Elpidium species with similar Cp, i. e., with LV embracing RV, symmetric in dorsal view, not ornamented and with sexual dimorphism of group A, include E. bromeliarum, E. pintoi, E. littlei, E. litoreum, and E. purium, but none of these species have a digital expansion at the base of the DL, although E. littlei has some subdigitiform, elongate triangular expansion. The species E. maricaoense and E. merendonense have a similar digital expansion (although smaller than in E. alarconi sp. nov.), but their Cp are asymmetrical in dorsal view. The Brazilian species E. cordiforme has a similar digital expansion, but its Cp is strongly cordiform in dorsal view, and the CoP and LR of Hp are notably different. Another Brazilian species, E. picinguabaense and the Argentinian E. chacoense also have a digital expansion in the DL. However, this expansion is shorter than in the new species. In addition, the female Cp of E. picinguabaense is not posteriorly truncate, but narrowly rounded, and the LR of the Hp is distinctly larger than in E. alarconi sp. nov. The female Cp of E. chacoense is not truncate posteriorly in dorsal view, but barely pointed. Elpidium higutiae, also from Brazil, has a similar Cp shape to E. alarconi sp. nov., and it also has a digital expansion on the DL, but this expansion is shorter than in E. alarconi sp. nov. and its LR is larger and thicker than in the new species. In fact, the very thin L-like shape of the LR in E. alarconi sp. nov. is a unique trait that allows distinction from all other Elpidium species.
Ecology and distribution.
Besides the type locality of Rancho Baiguate, it has also been found in Pinar Dorado Hotel (19°7'2"N, 70°37'58"W), 549 m a. s. l., sampled on 20 March 2018 by J. Rueda and P. Alarcón. This site is in the same municipality of Jarabacoa, but in the Pinar Dorado Sector. Tank bromeliads (possibly of the genus Neoregelia) growing at the base and the trunk of several trees in a relatively anthropized habitat composed of a law garden surrounded by pine trees, with a pool and a bar located nearby. In the type locality, the species was collected from the same type of bromeliads. Paratypes MUVHNZY 0035, MUVHNZY 0036, and MUVHNZY 0037 were collected from this locality; other types were collected in the type locality.
Etymology.
The species is named after Dr. Pedro María Alarcón-Elbal, who organized the sampling campaign in República Dominicana, obtained financial support and encouraged the senior author JR to study the invertebrates of the area.
description: Published as part of Mesquita-Joanes, Francesc, Gálvez, Ángel, Palero, Ferran & Rueda, Juan, 2025, A new species of Elpidium Müller, 1880 (Crustacea, Ostracoda) from Hispaniola, with an updated key to the species of the genus, and its molecular phylogenetic positioning within the Cytheroidea, pp. 75-106 in ZooKeys 1233 on pages 75-106, DOI: 10.3897/zookeys.1233.126611