Euconchoecia chierchiae Müller, 1890

Graves, Carol, 2011, Redescription of Euconchoecia chierchiae Müller, 1890 and Euconchoecia aculeata (Scott, 1894) (Halocyprididae: Ostracoda) from the Atlantic, and descriptions of two novel species of Euconchoecia Müller 1890, from the Gulf of Oman, Journal of Natural History 45 (31 - 32), pp. 1937-1981 : 1942-1949

publication ID	https://doi.org/ 10.1080/00222933.2011.573100
persistent identifier	https://treatment.plazi.org/id/016887A7-CD62-6E19-FE64-FB19CB7AFAC3
treatment provided by	Felipe
scientific name	Euconchoecia chierchiae Müller, 1890
status

Treatment

Euconchoecia chierchiae Müller, 1890 View in CoL

( Figures 1–6 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 , 21A,B View Figure 21 )

Euconchoecia chierchiae Müller, 1890: 277 View in CoL , Pl. XXVIII, fig. 1–10. Brady, 1902: 190, Pl. XXIV, fig. 9–15. Vavra, 1906: 29, Pl. 1, fig. 1–6. Skogsberg, 1920: 740, fig. CXLVIII– CLI. Deevey, 1968: 116, fig. 62. Poulsen, 1969: 38, fig. 12, 13. Tseng, 1969: 2, fig. 1. George, 1977: fig. 1, 2.

Paraconchoecia oblonga Cleve, 1900: 40 View in CoL .

Material

The material is not “ type ” material, but material collected from Discovery station 8281 (see above). Permanent preparations of dissected specimens used to prepare the illustrations in this paper have been deposited at the Natural History Museum, London: registration number BMNH 2009.316 for the female and BMNH 2009.317 for the

male. Registration numbers BMNH 2009.318 – 327 are for the 32 females and 9 males retained in 80% ethyl alcohol .

Description

A full redescription is merited because this is the type species for the genus. The meristic characters of the carapaces of both sexes, the frontal organs, first and second antennae, mouthparts and limbs are listed in Tables 2–9, together with comparative data for the other species examined: E. aculeata Scott 1894 , and the two new species from the Gulf of Oman .

Female

Carapace ( Figure 1A, B View Figure 1 ). Mean length 1.24 ± 0.05 mm (n = 32). Carapace of exemplar specimen ( Table 2) with length 1.28 mm, height 0.56 mm and breadth 0.50 mm. Height: length ratio 43.8%, breadth: length ratio 39.1%. Carapace unsculptured. In lateral view slightly elongate: maximum height just posterior to mid-length. Ventral margin curves smoothly into posterior margin. Posterior dorsal corner of both valves furnished with a small spine. Spine slightly smaller on left valve. Dorsal margin arcs anteriorly up towards dorsal end of hinge between carapace valves. Both rostra curve ventrally, the left rostrum is the longer and more pointed. The “asymmetrical” glands open at a similar height on posterior margin of each valve just below spine at posterior dorsal corner.

Frontal organ ( Table 2; Figure 1C View Figure 1 ). Frontal organ fused into a single slender structure with rounded end that is just shorter than A1 and 18.9% CL.

First antenna ( Table 3 Figure 1C View Figure 1 ). With five segments, but suture between fourth and fifth segments ill-defined. Limb length ∼ 31% CL. Fourth segment with ∼ 24 thin walled bundle setae all 17% CL. Fifth segment with four more unequal setae; a-seta quite short 5.1% CL; b-seta 9.4% CL; c-seta 17.2% CL; d-seta 13.9% CL.

Second antenna ( Table 3; Figure 1D View Figure 1 ). Protopodite 27.7% CL. Length of first exopodite segment ∼ half protopodite. Most swimming setae similar in length to protopodite, all but the shortest terminal seta have long hairs distally. Endopodite ( Figure 1E View Figure 1 ) with short, pointed, bare a- and b-setae. There are no c-, d- or e-setae. The f- and g-setae, respectively, 26.6% CL and 44.9% CL. The i-seta 13.3% CL, but h- and j-setae are absent.

Mandible ( Table 4; Figure 2A,B View Figure 2 ). Coxale toothed edge of pars incisiva has two large and 10 small smooth teeth. Distal tooth list slightly narrower with two large tusklike teeth and 10 small smooth teeth. The proximal tooth list very narrow, with two large and five small teeth. Outer margin of toothed edge of basal endite with a large dagger-shaped tooth, a slightly smaller, rounded, tubular tooth and six subserrate teeth. Two spinose setae are inserted laterally on basal endite. Exopodite represented by moderately long plumose seta inserted on outer margin of basis. First endopodite segment with one short, bare, subterminal, dorsal seta and three finely spinose ventral setae. Second segment with one ventral and two dorsal setae, all finely spinose. Third segment with seven spinose terminal setae; one very long and robust.

Maxilla ( Table 4; Figure 2C View Figure 2 ). Basal segment with five anterior, one lateral and four posterior setae. Distal segment comparatively short and wide with six terminal claw setae, the posteriormost is longest, anterior claw with secondary spines.

Fifth limb ( Table 5; Figure 2D View Figure 2 ). Ventrally basale with five (2+1+2) setae all with secondary spines; laterally two plumose setae, dorsally a single long spinose seta – the remnant of the exopodite. First segment with two ventral setae and one dorsal seta, all spinose. Second segment with three unequal, curved terminal claw setae; middle claw the longest 5.7% CL.

Sixth limb ( Table 5; Figure 2E View Figure 2 ). Basale with one proximal, two medial ventral spinose setae and a distal plumose seta, laterally a plumose seta and dorsally a terminal spinose seta. First endopodite segment with two ventral setae. Second segment with a single spinose seta both ventrally and dorsally. Third segment with three unequal spinose, terminal claw setae; longest middle claw 10.4% CL.

Caudal furca ( Table 5; Figure 2F View Figure 2 ). Seven pairs of claw setae diminish in size dorsally; longest claw 15.2% CL. All have secondary spines along their trailing edges. Dorsal to Notes: n = 1 for each species

% CL, % of carapace length.

the paired spines is a single seta with bilateral secondary spines. Between the first and second pairs of claw setae is a verruciform process.

Male

Carapace ( Figure 3A,B View Figure 3 ). Mean length 1.24 ± 0.06 mm (n = 9). Carapace of exemplar specimen ( Table 6) with length 1.26 mm, height 0.70 mm and breadth 0.60 mm. Height: length ratio 55.6%, breadth: length ratio 47.6%. Carapace unsculptured. Maximum height just anterior to mid-length. Ventral margin curves smoothly into posterior margin. Posterior dorsal corner of both valves furnished with a small spine. On the left valve the spine is slightly smaller. Dorsal margin arcs anteriorly up towards dorsal end of hinge between carapace valves. Both rostra forward pointing and of the same length. The “asymmetrical” glands open at a similar height on the posterior margin of each valve just below the spine at the posterior dorsal corner.

Frontal organ ( Table 6; Figure 3C View Figure 3 ). Frontal organ is fused into a slender structure with a rounded end, shorter than A1 and 23.2% CL.

First antenna ( Table 7; Figure 3C View Figure 3 ). With five well-defined segments. Limb length ∼ 31% CL. As in the female, fourth segment with ∼ 24 thin walled bundle setae all 17.5% CL. Fifth segment with five more unequal setae: a-seta 8.3% CL; b-seta 18.1% CL; c-seta 38.9% CL; d-seta 42.5% CL; e-seta 65.1% CL.

Second antenna ( Table 7; Figure 3D View Figure 3 ). Protopodite 38.5% CL. Length of first segment of exopodite ∼ half protopodite. Most swimming setae similar in length to protopodite, all but the shortest have long hairs distally. Endopodite with short, pointed a- and b-setae. There are no c-, d- or e-setae. The f- and g-setae respectively 22.4% CL and 79.8% CL. Right endopodite ( Figure 4B View Figure 4 ) with elongated clasping organ in form of hook with long proximal shank and very long curved end piece 9.1% CL. The h-, i- and j-setae attached distally to basal shank, h-seta is short 3.4% CL and curves over bases of other two, i-seta longest 15.9% CL. Left endopodite ( Figure 4A View Figure 4 ) “hook” reduced to just basal shank with three setae.

Mandible, maxilla, fifth limb ( Tables 8, 9; Figures 4C–E View Figure 4 , 5A View Figure 5 ). Structure and arrangement of setae for mandible, maxilla and fifth limb are same as for female.

Sixth limb ( Table 9; Figure 5B View Figure 5 ). Basale with five spinose setae ventrally, one lateral spinose seta and one bare dorsal exopodal seta. First endopodite segment with two ventral setae. Second endopodite segment with a single seta both ventrally and dorsally. Third segment with three subequal terminal setae, very long, evenly curved ventrally with long hairs 28.6% CL.

Caudal furca ( Table 9; Figure 5C View Figure 5 ). Structure and arrangement of furcal claws similar to female. The longest claw is 18.7% CL.

Intromittent organ ( Table 9; Figure 5C View Figure 5 ). Male copulatory appendage is exceptionally long, 27.4% CL.

Remarks

The original description of E. chierchiae by Müller (1890) and subsequent redescription ( Müller 1906) specified a wide size range; females from 1.15 to 1.53 mm and males from 1.15 to 1.45 mm. Size is a significant taxonomic feature of halocyprid ostracods, so a wide range such as this often suggests that there may be more than one species present. The redescriptions of E. chierchiae by Brady (1902) and by Vavra (1906) were considered doubtful by Skogsberg (1920), and the illustration by Skogsberg (1920) of a female specimen in lateral aspect differs from those of Müller (1890, 1906). Euconchoecia chierchiae as described by George (1977) from the Indian Ocean appears very similar to Atlantic E. chierchiae as described by Müller (1890). Deevey (1968) and later Angel (1999) identified and illustrated E. chierchiae from off Bermuda, and recently specimens from waters west of Bermuda have had the cytochrome oxidase type 1 gene (COI) sequenced (Angel, personal communication). However, critical comparisons of these two authors’ descriptions and figures deviate from those of both Müller (1906) and Skogsberg (1920), and the attributions of their specimens to this species remain open to question ( Figure 6 View Figure 6 ). There is a now a need for systematic and molecular studies to clarify the status of this species. Unfortunately, despite the remarkably high abundances of Euconchoecia in tropical waters especially in the Pacific, no sequencing of this genus has been undertaken, and the Gulf of Oman material is unsuitable for molecular sequencing because it was initially preserved in formalin.