Cypris pretusi Mesquita-Joanes, Aguilar-Alberola, Palero & Rueda, 2020

Mesquita-Joanes, Francesc, Aguilar-Alberola, Josep A., Palero, Ferran & Rueda, Juan, 2020, A new species of Cypris (Crustacea: Ostracoda) from the Iberian Peninsula and the Balearic Islands, with comments on the first ostracod named using the Linnean system, Zootaxa 4759 (1), pp. 113-131 : 118-120

Cypris pretusi Mesquita-Joanes, Aguilar-Alberola, Palero & Rueda sp. nov.

( Figs. 5–7 )

Type locality. Rambla de Orduña, a tributary of Palància river, El Toro municipality, Castelló Province, Spain ( Table 1).

Type material. Holotype: A female from Rambla Orduña, with soft parts mounted on a microscope slide in Hydromatrix®. Valves, coated for SEM, stored in a micropalaeontological slide (MUVHNZY0005).

Paratypes: Three females (MUVHNZY0006, MUVHNZY0007, MUVHNZY0008) from Bassa s’Enclusa , Minorca. Soft parts mounted on microscope slides in either Hydromatrix ® or glycerin, and valves stored dry in micropaleontological slides. Three more females from Bassa s’Enclusa in toto in ethanol in a small vial (MUVHNZY0009), and other three females in toto from R. Orduña in a micropaleontological slide (MUVHNZY0010) .

Repository: The holotype and all paratypes are deposited in the Museum of Natural History of the University of Valencia ( MUVHN), Burjassot, Spain. Other individuals from the same sites as the holotype and paratypes and from additional sites ( Table 1) are stored in the ostracod collection of F. Mesquita at the “Cavanilles” Institute of Biodiversity and Evolutionary Biology of the University of Valencia, Paterna, Spain .

Derivation of name. Specific epithet dedicated to Dr. Joan Lluís Pretus (Dep. Ecology, Univ. of Barcelona), who collected the samples from s’Albufera des Grau. We dedicate this species to him, not only because of providing the samples, but also for his dedication to the knowledge and preservation of aquatic environments and their inhabitants.

Abbreviated diagnosis. Intermediate-sized (~ 1.9 mm long) species of the genus Cypris . Cp subovate in dorsal view, relatively elongated and slender compared to other members of the genus. Posterior margin of valves with a row of small subequal denticles. Frontal edge of the Cp beak-shaped, without conspicuous spines. Swimming setae on the An2 not reaching the tips of the terminal claws.

Description of adult female (males unknown). Cp ( Fig. 5 , Table 2): L c. 1.7–2.0 mm. RV front edge protruding and embracing LV, producing in dorsal view a beak-like shape. LV anteriorly conspicuously shorter than RV. Each valve postero-ventrally with a row of small pointed denticles on their external margin. These denticles are larger and less numerous in the RV, and smaller but in higher numbers in the LV, although they can be difficult to observe or almost absent on the LV. Both valves with a distinct postero-dorsal angle in lateral view. Largest H located slightly in front of mid-length. Valves widest just before or at mid-length and covered with short setae. External surface of valves with small, reticulated-like pits, more conspicuous near the valve margins. Selvage inwardly displaced from the valve margin in the RV, both at the posterior and anterior parts, only slightly but variably displaced at the anterior part of the LV, and peripherally located at its posterior part.

An1 ( Fig. 6 ) very similar to that of the type species of the genus. Rome organ small and bottle-shaped on the ventral edge of the second articulated segment. Dorsal seta on the third segment hirsute. Y a one third of its length longer than the shortest seta on the last (seventh) segment.

An2 natatory setae ( Fig. 6 ) not reaching the tips of the terminal claws. Longest seta of the exopod almost as long as the corresponding endopod segment, reaching the base of the set of swimming setae.

Md-p ( Fig. 6 ) with four subapical setae on the outer edge of the third podomere. The branchial plate (exopod) has six relatively weak setae of unequal length.

Mx palp ( Fig. 7 ) with distal podomere rectangular, more than 2x as long as wide; the first podomere with 5 apical plus 2 dorsal subapical setae, one of the dorsal subapical setae about half as long as the others. Third endite with two serrated Zahnborsten. Exopod (branchial plate) with 19+6 setae.

L5 ( Fig. 7 ) with endopod (palp) carrying three apical setae of unequal length (1 short, 1 long, 1 intermediate); respiratory plate with 5 long and 1 short rays; protopod with 2 a -setae, 1 b and one d -seta, apart from an apical brush of c. 13 subequal setae plus a shorter one closer to the d -seta.

L6 (walking leg; Fig. 7 ) with d 1 seta about 2x as long as d 2. f-seta reaching the distal edge of the last segment. Seta h 1 thin and smooth, not claw-like.

L7 (cleaning leg; Fig. 7 ) without special features, similar to type species.

CR slender, with s a seta more than half the length of the s p seta. Claws thin and long, almost completely straight. Attachment distally bifurcated.

Interpopulation variability. Differences in Cp size between populations and instars are shown in Table 2. Cp L and H larger in the continental than in the island population. Anterior selvage of LV not largely displaced inwardly in the specimens from Palància river ( Fig. 5 ), deviating from the diagnosis of the genus; more clearly displaced in the Minorca specimens.

Ecology and distribution. The species is only known from two areas, one on the Eastern Iberian Peninsula, and the other in the island of Minorca. In the first case, it was found in two headstreams and the main channel of River Palància, a relatively small Mediterranean river suffering strong variations in flow discharge between seasons, some of its headstreams drying out in summer. In Minorca, the species was collected from a temporary pond in the Natural Park s’Albufera des Grau. Table 1 provides a summary of main characteristics of the sites and their environment.

Differential diagnosis. The most similar species to C. pretusi sp. nov. is the type species of the genus C. pubera . Even though C. pubera attains a slightly larger size, both have a very similar internal structure of the valves. They differ however in the presence in C. pubera of some larger spines on the posterior edge of the valves, plus a row of conspicuous denticles in the anterior part. On the other hand, C. pretusi sp. nov. has no apparent or just tiny denticles in the anterior part, and those at the posterior edge are all small and subequal. Furthermore, in C. pubera both valves have a similar non beak-like shape at their frontal end (although it can show slightly beak-shaped carapaces; Martens 1990: Fig. 4C ), but are asymmetrical and more clearly beak-like in C. pretusi sp. nov. This character makes the new species similar to C. decaryi , but this species has a higher W:L and H:L ratio than C. pretusi sp. nov. (W:L= 0.69-0.77 in C. decaryi vs. 0.55-0.56 in C. pretusi sp. nov.; H:L= 0.61-0.67 in C. decaryi vs. 0.53-0.61 in C. pretusi sp. nov.; C. decaryi data from Martens, 1990). In addition, the postero-ventral calcified inner lamella of LV and the postero-ventral fused zone of RV are wider in C. pretusi sp. nov. than in C. decaryi . The soft part anatomy of C. pretusi sp. nov. is very similar to C. pubera , but the swimming setae on the second antennae are a bit shorter (not reaching the tips of the terminal claws) in the new species.

Figures

FIGURE 4. Page 198 of Müller (1776), where he introduces the ostracod species name Cypris pubera for the first time and synonymizes it with Linnaeus’ Monoculus conchaceus.

FIGURE 5. Scanning electron micrographs (A-K) and drawings (L–N) of shells and valves of Cypris pretusi sp. nov. A–B: dorsal (A) and ventral (B) view of whole specimens from R. Palància (A: MUVHNZY0000, B: MUVHNZY0001). C: dorsal view of a specimen from Minorca (MUVHNZY0002). D–E: Inner view of left (D) and right (E) valves of specimen MUVHNZY0005 from R. Palància. F–G: Inner views of left (F) and right (G) valves of a specimen MUVHNZY0003 from Minorca. H–I: Outer views of right (H) and left (I) valves of a specimen MUVHNZY0004 from Minorca. J: detail of anteroventral part of a female (MUVHNZY0001). K: detail of postero-ventral part of a female (MUVHNZY0001) showing the apparent denticles, larger and less numerous in the right valve. L–N: drawings of left (L) and right (M) valve, and detail of the posterior edge of right valve (N) of a specimen (MUVHNZY0008) from Minorca. Small scale below M=500 µm for A–I, L and M, larger scale=500 µm for N. Scale for J–K indicated as=100 µm.

FIGURE 6. Details of the antennula (An1), antenna (An2), and mandibula (Md) of C. pretusi sp. nov. All drawings from individual MUVHNZY0005, except branchial plate of Md and Ro (MUVHNZY0006).

FIGURE 7. Details of the maxillula (Mx), maxillular branchial plate (Mx bp), 5th limb (L5; maxilliped), 6th limb (L6; walking leg), 7th limb (L7; cleaning leg) and its pincer and caudal ramus (Cr), together with the female genital organ of C. pretusi sp. nov. All drawings from individual MUVHNZY0005, except branchial plates of Mx and L5, detail of the tip of L7 (MUVH- NZY0006) and female genital organ (MUVHNZY0007).