Spinacopia ningalooi, Karanovic, 2012

Karanovic, I., 2012, Two new Sarsiellinae (Ostracoda: Myodocopa) from Ningaloo Reef (Western Australia), with a cladistic analysis of the subfamily and keys to genera, Journal of Natural History 46 (37 - 38), pp. 2285-2327 : 2291-2300

Spinacopia ningalooi sp.nov.

( Figures 1–5 )

Material examined

Holotype female with two eggs (dissected on one slide, shell on scanning electron microscope stub, WAM C49454), two paratype females, one with three eggs, the other with two eggs (one dissected on one slide, shell on the micropalaeontological slide, WAM C49455, other kept in alcohol, WAM C49456) from site ARMS-1, NR10-012, Ningaloo Reef, 22 ◦ 46 ′ 8.832 ′′ S, 113 ◦ 42 ′ 16.488 ′′ E, bottom – rock, depth 13 m, 17 May 2010.

Diagnosis

A Spinacopia species , with a relatively prominent, pointed caudal process, and no anterior incisures. Shell harshly ornamented with large fossae and long surface bristles some with bulbous bases. Only prominent, and sometimes those with bulbous base, bristles present on the surface. No gelatinous coating on the surface. Posterior infold typical for the genus, but with addition of several short, strong and some bifurcate extensions situated ventrally to the dorsal row of bristles. Only one bristle present antero-distally on the fused third and fourth segments of the A1. Endopod A2 one-segmented, with one basal and no apical bristles. Only two bristles present on the terminal segment of the A2. Exopod Md completely reduced. Exopod Mxl with three bristles. Endopod of L5 with two bristles. Endite on L6 with three bristle and with a group of 14 bristles distally. L7 with only one pair of the bell-bearing bristles proximally and with three teeth on the each side of the terminus. UL with six claws, all strongly serrated. Lateral eyes present.

Etymology

The species is named after the Ningaloo Reef, from where it was collected.

Description

Female. Carapace oval in lateral view with greatest height situated posteriorly ( Figures 1A,B ; 2A,C ). Dorsal margin almost flat with the exception of the large postero-dorsal bulge, which slightly extends valve dorsal margin. Ventral margin of the bulge rounded. Anterior and ventral margins evenly and broadly rounded. Caudal process relatively short, situated postero-ventrally ( Figures 1C ; 2B,D ), and projecting past valve edge, and with distal margin rounded. Surface of the shell ornamented with large and irregularly shaped fossae ( Figure 1A ). Anterior and ventral margins of valves with many bristles, some fairly long, some slender and some with broad base. Infold of the LV ( Figure 2D ) with row of eight weakly pappose bristles laying more in dorsal part, and five additional spine-like structures, which are extensions of the infold, no additional bristles present on the inner margin. Infold on the RV ( Figures 1C,E ; 2B ) with seven weakly pappose bristles ( Figure 1E ) in a row and four additional extensions which on RV are distally branched ( Figure 1D ), few additional small bristles present more ventrally on the inner margin ( Figure 1F ). Flange on the valves well developed along dorsal, anterior and ventral margins. Length of valves with caudal process equalling 0.89 mm, height of the valves equalling 0.66 mm.

A1 ( Figure 3A ). With four proximal segments distinct, and segments 5–8 partially or completely fused. First segment bare. Second segment with one bare dorso-distal bristle that almost reaches distal end of the third segment. Third “segment” represents the third and fourth segments fused carrying four bristles; a dorsal and a ventral bristle inserted proximally and a dorsal and a ventral bristle inserted distally. All bristles bare. Both proximal bristles reach distal end of the same segment, dorso-distal one reaching two-thirds of following segment, whereas ventro-distal extends well beyond end of A1. Sensory bristle on the fifth segment long and bare, with pointed tip. This segment fused with the sixth segment, is which indicated by a very short bristle inserted above the abristle. Seventh segment with bristles a-, b-, and c-. The a-bristle short and bare, the b-bristle long with a blunt tip and with a short sensory-like filament on its proximal part, the c-bristle long and with a pointed tip and a sensory-like filament positioned proximally. Segment eight carries bristles d-, e-, f- and g-, all bare and only e-bristle shorter than others. Only d-bristle with pointed tip. Bellonci organ ( Figure 3B ) on its first third with one suture. Both eyes present, medial being slightly larger and with brownish pigment,?each lateral eye with about five omatidia.

A2 ( Figure 4B ). Basis large and bare. Endopod reduced and one-segmented with short and bare proximal bristles, distal bristle missing. Exopod nine-segmented. First segment longest and lacks a medial bristle. Second to eighth segments carrying one bristle each and the bristle on the second segment with a row of short spines proximally and setulae distally. Bristles on each following segment longer and also with proximal spines, and distal setulae. Terminal segment with two bristles, one long with setulae distally, other very short and bare.

Md ( Figure 3C,D ). Coxa very large ( Figure 3C ), with coxal endite bifurcate distally with few stout spines. Ventral margin of coxa with a row of long spine-like bristles, and medially a well-sclerified rod-shaped structure with a row of fine setulae. Basis ( Figure 3D ) with two short and bare dorsal bristles. Ventral margin with three sets of bristles: proximal set consists of one bare bristle and one distally pappose bristle half as long as previous one; medial set consists of three short, bare bristles, one half as long as the other two and situated on the opposite sides of the appendage; the distal set consists of a single, bare, long bristle, almost reaching to distal end of the first endopodal segment. Endopod three-segmented, with three groups of short setulae on its ventral margin (two more proximal groups with two, most distal group with one setula). First endopodal segment medially and dorso-distally with rows of fine setulae. Distal claw on the first segment with one short spinula at its basis. Second endopodal segment with one dorsal short bristle, ventral claw with one spinula at its basis. Terminal segment also with one dorsal bristle and long ventral claw.

Mxl ( Figure 4C,D ). Coxal bristle (cb) short and pappose, dorsal to it is a bunch of hair-like bristles originating from a conical process. Basis with two short, pappose basal bristles (bb). Exopod with two long, pappose bristles. Endopod two-segmented: first segment distally with two strong claws, one on each side (α and β both pappose; second segment with five strong, relatively long and serrated claws and three bristles (two a-bristles and one c-bristle), a-bristles pappose, c-bristle bare. Endite I with total of seven bristles: one claw-like and serrated, one also claw-like but not serrated, and five more bristle-like. Endite II with three distal bristles, one claw-like. Endite III with two strongly serrated claws and four pappose bristles.

L5 ( Figure 3E ). Epipod with 32 bristles. One coxal endite present and with one short and bare bristle. Basis with apparently three endites: endite I clearly divided and with three pappose distal bristles, endite II not clearly separated from endite III and with five bristles: four pappose and one bare; one of the pappose bristles very short and laying on the margin between two endites. Endopod 1 with two long bare bristles based on a small extension, and one short, bare bristle inserted on the lateral side of this protrusion. Endopod 2 clearly marked and with two distal, long and bare bristles. Exopod reduced and represented with one bare bristle.

L6 ( Figure 4A ). Single endite with three short and pappose bristles, distally to which a row of 14 pappose bristles and two plumose posterior bristles. The 14 bristles in this row divided in eight apparent groups: group closest to the endite with two bristles, followed by two groups of two bristles each, than a group of three, then two bristles, and finally three groups of one bristle each. Appendage very hirsute.

L7 ( Figure 5A ). Distal part with opposing combs: one with two teeth and opposite with three teeth. Three bell-like bristles present on each side of the comb. Additional one bell-like bristle on each side of the appendage present more distally.

UL ( Figure 5B ). Each lamella with six claws, all strongly serrated (especially the first, second and third). First claw fused with the lamella, others separate. Third claw much shorter than both its neighbouring claws. “Y”-sclerite ( Figure 5C ) without special characteristics.

Male. Unknown.

Variability

One L6 of the holotype female has only two bristles on the endite.

Affinities

The new species differs from the other 14 species in the genus by having spine-like, bifurcate extensions on the posterior infold on both valves, in addition to the normally developed, strong, pappose and more dorsally situated bristles. In all the other species only the dorsal bristles are present. The second character differentiating the new species is the morphology of the endopod of A2. In Spinacopia ningalooi sp. nov., the endopod is uniquely one-segmented, and without an apical bristle. In all other species the endopod is two-segmeted and carries one or more apical bristles. In addition, S. ningalooi has only a single bristle on the first segment of the endopod of A2, whereas most of the other species have either two or three. The new species is most closely related to S. crux Kornicker, 1995 , S. ilex Kornicker, 1995 and S. syrinx Kornicker, 1995 , all described from the Australian continental slope ( Kornicker 1995b), and has only six, instead of seven, claws on the UL. They also all have only one bristle antero-distally on the fused third and fourth segments of the A1, a character that is also shared by S. sandix Kornicker, 1995 and S. trox Kornicker, 1995 , from the same region ( Kornicker 1995b). In all these five Australian species the exopod of the Md in females is reduced (absent in S. ningalooi ); in all the other species, including S. rex Kornicker, 1995 from the south Australian continental slope, the exopod is present as a clearly defined segment carrying one or two bristles. Spinacopia rex differs from all the other species described from the south Australian continental slope in having two pairs of bell-bearing bristles proximally on the L7 (the others have a single pair); it shares this character with S. bisetula Kornicker, 1969 and S. sandersi Kornicker, 1969 , which are described from Madagascar and Bermuda, respectively ( Kornicker 1969). The other Spinacopia species have more than two pairs of these bell-bearing bristles. The majority of Spinacopia species lack lateral eyes, but they are present not only in the new species but also in S. crux , S. ilex and S. sandix .

Key to species of Spinacopia Kornicker, 1969 (modified after Kornicker 1975, 1995b)

1. Three bristles present antero-distally on the fused third and fourth segments on A1......................................... S. menziesi Kornicker, 1969 Fewer than three bristles antero-distally on the fused third and fourth segments of A1............................................................. 2

2. Two bristles present antero-distally on the fused third and fourth segments of A1...................................................................... 3 One bristle antero-distally on the fused third and fourth segments of A1.. 10

3. Shell with one or several longitudinal ridges.............................. 4 No longitudinal ridges present........................................... 5

4. UL with eight claws........................... S. antarctica Kornicker, 1970 UL with seven claws............................... S. torus Kornicker, 1970

5. Surface of the shell with prominent fossae......... S. mastix Kornicker, 1975 Fossae if present very small.............................................. 6

6. Some small fossae present on the surface................................. 7 Surface of the shell smooth.............................................. 8

7. First segment of endopod A2 with three bristles...... S. rex Kornicker, 1995 First segment of endopod A2 with two bristles... S. sandersi Kornicker, 1969

8. L of carapace greater than 2.5 mm .................. S. octo Kornicker, 1970 L of carapace less than 2.2 mm ........................................... 9

9. Ventral margin of postero-dorsal bulge with long hairs forming row......................................................... S. bisetula Kornicker, 1969 Hairs along ventral margin of postero-dorsal bulge not longer than those on reminder of bulge.............................. S. variabilis Kornicker, 1969

10. Endopod of A2 with apical bristles...................................... 11 Endopod of A2 without apical bristles.................. S. ningalooi sp. nov.

11. Carapace longer than 1.4 mm ....................... S. trox Kornicker 1995 Carapace shorter than 1.3 mm .......................................... 12

12. Radial ribs present on the shell................... S. sandix Kornicker, 1995 Radial ribs absent...................................................... 13

13. Lateral eye absent................................ S. syrinx Kornicker, 1995 Lateral eye present..................................................... 14

14. A1 with ventral spines on second and fourth segments.......................................................................... S. ilex Kornicker, 1995 A1 without ventral spines on second and fourth segments..................................................................... S. crux Kornicker, 1995

Figures

Figure 1. SEM photographs, Sarsiella ningalooi sp. nov., female, holotype: A – LV, lateral view from the outside; B – RV, lateral view from the inside; C – RV, caudal infold; D – RV, ventral part of the posterior infold; E – RV, detail of the bristles on the posterior infold; F – RV, bristles on the postero-ventral part.

Figure 2. Sarsiella ningalooi sp. nov., Female, Holotype: A – RV, inside view; B – RV, posterior infold; C – LV, inside view with one egg; D – LV, posterior infold. Scales = 0.1 mm.

Figure 3. Sarsiella ningalooi sp. nov., Female, Holotype: A – A1: B – Bellonci organ, lateral and medial eye; C – Coxa of Md; D – Md without coxa: E – L5. Scales = 0.1 mm.

Figure 4. Sarsiellani ningalooi sp. nov., Female, Holotype: A – L6; B – A2; C – Exopod and endpod of Mxl; D – Coxa and endites on the Mxl. Scales = 0.1 mm.

Figure 5. Sarsiella ningalooi sp. nov., Female, Holotype: A – distal part of the L7; B – right UL; C – posterior part of the body and Y-sclerite. Scales = 0.1 mm.