Strandesia thomazi, Ferreira & Higuti & Martens, 2020

Ferreira, Vitor Góis, Higuti, Janet & Martens, Koen, 2020, Taxonomic revision of Strandesia s. s. (Crustacea, Ostracoda) from four Brazilian floodplains, with the description of three new species, Zootaxa 4760 (1), pp. 1-74 : 13-18

2. Strandesia thomazi nov. sp.

( Figs. 5–7 )

urn:lsid:zoobank.org:act:7297693B-7495-4652-A34B-E9B04B420A53

2017 Strandesia n. sp. 7—Pereira et al.: 327, Table 2.

Measurements of illustrated specimens (in mm)

L (n=4): 1.110 –1.115, H (n=2): 0.700 –0.760, W (n=2): 0.578 –0.594.

Diagnosis

Cp subovate, with LV anteriorly, ventrally and posteriorly overlapping RV. RV overlapping LV dorsally with a rounded protuberance. LV with internal groove along ventral margin. CpFr asymmetrical, with RV higher than LV. CpD with a blunt anterior rostrum. RV with anterior selvage slightly inwardly displaced. A2 with natatory setae almost reaching tips of apical claws. T2 with d1 seta slightly longer than d2. Caudal ramus slender, its attachment with an oval Triebel’s loop situated in the main branch.

Type locality

Araguaia River floodplain, Montaria I Lake in roots of Paspalum notatum . Coordinates: 13º24’07.9ʺS, 50º43’10.2ʺW, central Brazil.

Type material

Holotype: A female, with soft parts dissected in glycerine in a sealed slide and with valves stored dry in a micropaleontological slide ( MZUSP 40403 ).

Paratypes: Three females dissected and stored as the holotype ( MZUSP 40404 , MZUSP 40405 , MZUSP 40406 ) . Four female carapaces stored dry in micropaleontological slides ( MZUSP 40407 - MZUSP 40410 ) .

Etymology

This species was named in honour of Prof. Dr Sidinei Magela Thomaz (State University of Maringá, Nupélia/PEA, Brazil) for his very significant contributions to the ecology and limnology of Brazilian inland waters and their macrophytes. Prof Sidinei “Nei” Thomaz has been most helpful in establishing ostracod studies at Nupelia and is a close personal friend of KM.

Description of female

LVi ( Fig. 5A, I ) high, with calcified inner lamella relatively wide along anterior margin, narrow along ventral margin and absent on posterior margin; with an anterior inner list; inwardly displaced submarginal selvage; internal groove along ventral margin; greatest height situated in front of the middle.

RVi ( Fig. 5B ) high and with dorsal protuberance; with calcified inner lamella as in LVi, anteriorly and posteriorly with selvage slightly inwardly displaced, greatest height situated slightly behind the middle because of dorsal protuberance.

CpLl and CpRl ( Fig. 5C, D ) subovate; greatest height situated behind the middle; external valve surface set with few pits and setae. CpD ( Fig. 5E ) with LV overlapping RV along the anterior margin; this anterior margin a blunt beak, posteriorly bluntly rounded, also with asymmetrical overlap. CpV ( Fig. 5F, G ) with LV overlapping RV from posterior to anterior margin, centrally with a weak flap-like expansion. CpFr ( Fig. 5H ), with valves asymmetrical, RV higher than LV; LV with ventral projection over RV.

A1 ( Fig. 6A ) with seven segments. First segment with one short subapical seta and two long apical setae; WO small. Second segment wider than long, with one short dorsal seta and a small ventral RO. Third segment with two setae (the smaller almost reaching the tip of the fifth segment). Fourth segment with four setae (two short and two long). Fifth segment with three long and one short setae (twice the length of fifth segment). Sixth segment with four long setae. Seventh segment with one short and two long setae, and one aesthetasc ya, ca. 2x as long as the short seta.

A2 ( Figs. 6B, C ) with protopodite, exopodite and three-segmented endopodite. Protopodite with two ventral setae; and one long ventro-distal seta. Exopodite reduced to a small plate, with one long and two unequal short setae. First endopodal segment with one ventral aesthetasc Y, one long apical seta (reaching the tip of the second endopodal segment), one group of five long and one short swimming setae (the five long setae almost reaching tips of apical claws; the shortest almost reaching the middle of second endopodal segment). Second endopodal segment undivided, with two unequal dorsal setae and a group of four long and unequal ventral setae; apically with three claws, G1 longer, G2 shorter, and G3 slightly shorter than G1, three equally long setae (z1, z2 and z3) and a short aesthetasc y2 ( Fig. 6B ). Terminal segment ( Fig. 6B ) with two claws (one long GM; one short, Gm), an aesthetasc y3 with an accompanying seta (seta longer than aesthetasc), fused over a short distance only, and a fine g-seta, the latter shorter than the accompanying seta and aesthetasc y3.

First segment of Md palp ( Fig. 6 D—chaetotaxy not completely shown) with one long (reaching beyond tip of ss-seta) and smooth α-seta. Second segment ventrally with one long, stout and distally hirsute ss-seta. Penultimate segment laterally with one cone-shaped, stout and distally hirsute γ-seta. Terminal segment sub-rectangular, ca. 1.5x as long as basal width. Md coxa (not illustrated) as typical of the family: elongated with an apical row of strong teeth of variable size, interspaced with some setae.

Mx1 ( Fig. 6 E—chaetotaxy not completely shown) with three masticatory lobes, a two-segmented palp and a large respiratory plate (the latter not illustrated). Basal segment of palp with six apical setae, and one shorter subapical seta. Terminal palp segment elongated, ca. twice as long as basal width, slightly curved and tapering, apically with three claws and three setae. Third endite with two large, distally serrated bristles. Subapical seta on third endite reaching beyond edge of the endite. First endite with two unequal sideways-directed bristles and two unequal basal setae.

T1 protopodite ( Fig. 6F ) with two short a-setae, one distally hirsute b-seta and one longer distally hirsute d-setae, almost twice as long as b-seta. Apically with 10 hirsute setae, subapically with a group of four setae. Endopodite with three unequal long hirsute apical setae (not illustrated).

T2 ( Fig. 7A ) protopodite with seta d1 long and seta d2 shorter, ca. 2/3 of the length of d1. First endopodal segment with one subapical hirsute seta (e). Second endopodal segment medially divided into a- and b-segments; segment “a” with one long apical hirsute seta (f); segment “b” with one shorter seta (g) reaching the tip of the terminal segment. Third endopodal segment with one apical claw (h2) and two setae (one ventro-apical subapical (h1) with 1/4 the length of h2 and one dorso-apical (h3) slightly shorter than h1).

T3 ( Fig. 7 B—chaetotaxy not completely shown) with three segments. First segment with three long setae (d1, d2, dp). Second segment, longer than wide, with one subapical seta (e). Third segment, also longer than wide, with one lateral, hirsute seta (f); distal part of the third segment fused with fourth segment into a modified pincer, with one apical comb-like seta (h2), one small recurved seta, with 1/5 of the length of the comb-like seta and one longer and distally hirsute seta (h3). Small tooth-like structures present at the base of the comb-like seta (arrowed in Figure 7B ).

CR ( Fig. 7C ) slender and curved, with ventral margin weakly serrated, not with distinct groups. Proximal claw 2/3 of the length of distal claw. Proximal seta smooth, ca. 1/3 of length of distal seta.

CR attachment ( Fig. 7D ) stout, with Triebel’s loop oval-shaped, situated in the db; vb long.

Male unknown.

Differential diagnosis

Strandesia thomazi nov. sp. can be distinguished from most other Strandesia species by the rounded dorsal protuberance on the RV and the blunt beak on the anterior end of the carapace in dorsal view. This species is most similar in lateral view to the African S. elatior (Vávra, 1897) , but the carapace in this latter species has no anterior beak in dorsal view. In other species of the genus with a dorsal protuberance on the RV, this structure has a different shape: it has a straight margin and a posterior spine in the African type species of the genus, S. mercatorum . Of other such species, S. bicuspis ( Claus, 1892) has a posteriorly pointed dorsal protuberance, the dorsal protuberance is semirectangular and larger in S. feuerborni Klie, 1932 , small and sub-quadrate in S. pistrix Broodbakker, 1983 , larger in S. evae Gauthier, 1951 and smaller and more symmetrically rounded in the S. cyprinotoides Klie, 1938 . Strandesia thomazi nov. sp. differs from Strandesia galeati nov. sp. in that it is generally higher and less elongated (especially the LV) and that the dorsal protuberance is situated more posteriorly.

Ecology and distribution

Strandesia thomazi nov. sp. was recorded in lentic environments, associated with emergent macrophytes, in the Araguaia River floodplain. This species occurred in slightly acidic environments, with a pH range of 6.2–6.7. Electrical conductivity and dissolved oxygen ranges were 42.3–43.6 µS. cm-1 and 1.9–2.9 mg. L-1, respectively (see Table 1). Distribution: Brazil.

Figures

FIGURE 5 Carapace and valves of Strandesia thomazi nov. sp. A, LVi (MZUSP 40406); B, RVi (MZUSP 40406); C, CpLl (MZUSP 40407); D, CpRl (MZUSP 40410); E, CpD (MZUSP 40408); F, CpV (MZUSP 40409); G, CpV detail of anterior part; H, CpFr (MZUSP 40408); I, LVi detail of posterior part (MZUSP 40409). Scale bars, A-F, H, 500 μm; G, 300 μm; I, 400 μm.

FIGURE 6 Strandesia thomazi nov. sp. A, A1 (MZUSP 40403); B, A2 except last segment (MZUSP 40403); C, A2 last segment (MZUSP 40403); D, Md palp showing α, ss, γ setae (MZUSP 40403); E, Mx1 (MZUSP 40403); F, T1 (MZUSP 40405). Scale bars, 50 μm.

FIGURE 7 Strandesia thomazi nov. sp. A, T2 (MZUSP 40403); B, T3 pincer (MZUSP 40403); C, CR (MZUSP 40403); D, CR attachment (MZUSP 40403). Scale bars, 50 μm.