Euconchoecia hormuzensis, Graves, 2011

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 : 1970-1976

Euconchoecia hormuzensis sp. nov.

( Figures 16–20 , 21G,H )

Type material

Permanent preparations of the dissected holotype and allotype used in this description are deposited at the Natural History Museum, London, registration number BMNH 2009.342 for the holotype (female) and BMNH 2009.343 for the allotype (male). Registration numbers BMNH 2009.344 – 353 are for the 48 female and 36 male paratypes retained in 80% ethyl alcohol .

Etymology

The specific name refers to the type locality close to the Gulf of Hormuz .

Description

The meristic characters of the carapaces of males and females, and the frontal organs, first and second antennae, mouthparts and limbs are listed in Tables 2 to 9 together with comparative data for the other species described here.

Female

Carapace ( Figure 16A,B ). Mean length measured 1.04 ± 0.05 mm (n = 48). Carapace of holotype ( Table 2) with length 1.00 mm, height 0.42 mm and breadth 0.40 mm. Height: length ratio 42.0%, breadth: length ratio of 40.0%. Carapace unsculptured. In lateral view slightly elongate: maximum height just anterior to mid-length. Ventral margin curves smoothly. 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 and are of the same length. 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 16C ). Frontal organ fused into a single slender structure with a rounded end that is slightly longer than A1 and 20.3% CL.

First antenna ( Table 3; Figure 16C ). With five segments, but suture between fourth and fifth segment ill-defined. Limb length is ∼ 37% CL. Fourth segment with ∼ 24 thin walled bundle setae all 16.3% CL. Fifth segment with four more setae of different lengths; a-seta quite short 3.8% CL; b-seta 5.5% CL; c-seta 17.0% CL; d-seta 13.5% CL.

Second antenna ( Table 3; Figure 16D ). Protopodite 30% CL. Length of first exopodite segment approximately half length of protopodite. Swimming setae shorter in length than protopodite, all but shortest have long hairs distally. Endopodite ( Figure 16E ) with short, pointed, bare a- and b-setae. There are no c-, d- or e-setae. The f- and gsetae respectively 24.0% CL and 43.5% CL. The i-seta is long 11.5% CL, but h- and j-setae are absent.

Mandible ( Table 4; Figure 17A,B ). Coxale toothed edge of pars incisiva has two large and 10 small smooth teeth. Distal tooth list narrower with two large tusk-like teeth and 10 small smooth teeth. 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 triangular teeth. Two spinose setae are inserted laterally on basal endite. Exopodite represented by moderately long plumose seta of moderate length 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 17C ). 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 17D ). Ventrally basale with five (2+1+2) setae all with secondary spines; laterally 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 spinose, terminal claw setae; longest middle claw 5.5% CL.

Sixth limb ( Table 5, Figure 17E ). Basale with one proximal, two medial ventral spinose setae and a distal plumose seta, laterally a plumose seta and dorsally a terminal spinose exopodal 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 8.5% CL.

Caudal furca ( Table 5; Figure 17F ). Seven pairs of claw setae diminish in size dorsally; longest claw 12.0% CL. All have secondary spines along the trailing edges. Dorsal to the paired spines is a small unpaired seta with bilateral secondary spines. Between the first and second pair of claw setae is a verruciform process.

Male

Carapace ( Figure 18A,B ). Mean length measured 1.00 ± 0.03 mm (n = 36). Allotype ( Table 6) with length of 0.98 mm, a height of 0.40 mm and breadth of 0.40 mm. Height: length ratio 40.8%, breadth: length ratio 40.8%. Carapace unsculptured. In lateral view 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 carapace hinge between carapace valves. Both rostra curve ventrally, the left 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 6, Figure 18C ). Frontal organ fused into a single slender structure with a rounded end that is slightly longer than A1 and 21.1% CL.

First antenna ( Table 7; Figure 18C ). With five well-defined segments. Limb length ∼ 34% CL. Fourth segment with ∼ 24 thin walled bundle setae all 17.1% CL. Fifth segment with five more setae; a-seta 3.7% CL; b-seta 4.6% CL; c-seta 13.8% CL; d-seta 34.2% CL; e-seta 50.0% CL.

Second antenna ( Table 7; Figure 18D ). Protopodite 40.8% CL. Length of first exopodite segment 15.3% CL approximately third protopodite. Most swimming setae are about two-thirds the length of protopodite, all but shortest have long hairs distally. Endopodite with short, pointed, bare a- and b-setae. There a no c-, d- or e-setae. The fseta and g-seta respectively 39.8% CL and 119.9% CL. Right endopodite ( Figure 19B ) with elongated clasping organ in form of hook with a long proximal shank and long curved end piece 6.4% CL. The h-seta is short and curved 2.8% CL; the i-seta 20.7% CL; j-seta 9.7% CL. Left endopodite ( Figure 19A ) “hook” reduced to just basal shank with three setae terminally.

Mandible, maxilla, fifth limb ( Tables 8, 9; Figure 19C,D,E , 20A ). Mandible, maxilla and fifth limb structure and arrangement of setae are same as female.

Sixth limb ( Table 9; Figure 20B ). Basale with five spinose setae, one lateral spinose seta and one bare dorsal exopodal seta. First segment with two ventral setae. Second segment with a single bare seta both ventrally and dorsally. Third segment with three subequal terminal setae, all very long, evenly curved with long hairs distally 34.7% CL.

Caudal furca ( Table 9; Figure 20C ). Structure and arrangement of the furcal claws are same as female; longest claw 14.5% CL.

Intromittent organ ( Table 9; Figure 20C ). The male copulatory appendage is long, 20.9 % CL.

Remarks

Euconchoecia hormuzensis may be regarded as a separate species on the basis of both sexes being markedly smaller in length, breadth and height than the other three species; the height: length ratio in both sexes is approximately 40% and the breadth: length ratio in both sexes is approximately 40%. The spines on the posterior dorsal corner are similar in length and the rostral processes are quite short. The frontal organ is marginally longer than the first antenna in both sexes, whereas in E. chierchiae the frontal organ is shorter and in E. aculeata it is marginally longer in the female, but shorter in the male. In E. omanensis the frontal organ is significantly longer than the first antenna in both sexes. On the second antenna the right shank length, at 6.4%, is greater than the shank length of E. aculeata and E. omanensis , but less than the shank length of E. chierchiae . These differences are sufficient to justify the establishment of a new species.

Figures

Figure 16. Euconchoecia hormuzensis female: (A) lateral view, (B) carapace dissected and viewed dorsally – arrows indicate gland openings, (C) first antenna and frontal organ, (D) second antenna viewed from inside, (E) endopodite viewed from inside.

Figure 17. Euconchoecia hormuzensis female: (A) mandible, coxale not shown, (B) basal endite of mandible, (C) maxilla, (D) fifth limb, (E) sixth limb, (F) caudal furca.

Figure 18. Euconchoecia hormuzensis male: (A) lateral view, (B) carapace dissected and viewed dorsally – arrows indicate gland openings, (C) first antenna and frontal organ, (D) second antenna viewed from inside.

Figure 19. Euconchoecia hormuzensis male: (A) left endopodite viewed from inside, (B) right endopodite viewed from inside, (C) mandible, coxale not shown, (D) basal endite of mandible, (E) maxilla.

Figure 20. Euconchoecia hormuzensis male: (A) fifth limb, (B) sixth limb, (C) caudal furca and intermittent organ.

Figure 21. Euconchoecia. (A) E. chierchiae female, (B). E. chierchiae male, (C) E. aculeata female, (D) E. aculeata male, (E) E. omanensis female, (F) E. omanensis male, (G) E. hormuzensis female, (H) E. hormuzensis male, all viewed laterally.