Metasarsiella caleyi, 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 : 2301-2308

Metasarsiella caleyi sp.nov.

( Figures 6–10 )

Material examined

Holotype female with three eggs (dissected on one slide, shell on scanning electron microscope stub, WAM C49457), one paratype with three eggs (dissected on one slide, shell on the micropalaeontological slide, WAM C49458) 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

Metasarsiella species prominently ornamented, with one bristle antero-ventrally on the fused segments three and four of the A1. Second segment of A2 endopod completely reduced. Three teeth present on each side of the comb on the terminus of L7. One bell-bearing bristle on each side of the L7 proximally. Medial eye present.

Etymology

The species is named after Dr Julian Caley from Australian Institute of Marine Science.

Description

Female. Carapace oval in lateral view with prominent caudal process orientated posteriorly ( Figures 6A,B ; 7A,B ; 8A ). Posterior process situated near middle of posterior margin and projecting past valve edge, and with distal margin almost straight. One ridge lying just within valve extending along ventral, posterior and dorsal margin. This ridge with several projections: one postero-medially and two dorsally. Surface of the shell ornamented with very large and irregularly shaped fossae ( Figure 6D ). Anterior and ventral margins of valves with many bristles (not shown on the Figure 7A,B ), some fairly long, some slender and some with broad base. Ventral and anterior margins of the valves evenly and broadly rounded, whereas dorsal margin uneven because of the projections of the ridge. Same margin clearly inclined in antero-dorsal part. Infold of the LV ( Figures 6E,F ; 8B ) with five small and bare bristles lying medially and two pappose bristles inserted postero-distally. Infold on the RV ( Figure 8C ) with medially four bare bristles, and postero-distally two pappose bristles. Flange on the valves well developed along dorsal, anterior and ventral margins. Length of valves with caudal process 0.81 mm, height of the valves 0.62 mm. Adductor muscle scars obscure ( Figure 6C ).

A1 ( Figure 9A ). With four proximal, distinct segments, and segments 5–8 partly or completely fused. First segment bare. Second segment with one bare dorso-distal bristle reaching last third of the third segment. Third segment representing fused third and fourth segments and together carrying two dorsal and two ventral bristles. One dorsal and one ventral bristle inserted proximally on the segment, and one dorsal and ventral bristle inserted distally. All bristles bare. Both proximal bristles short and extend only just beyond distal end of the third segment. Dorso-distal bristle very short and not reaching one third of the fourth segment, while ventro-distal bristle long and reaching distal end of the following segment. Sensory bristle on the fifth segment long and bare, with pointed tip. This segment fused with the sixth segment, which is represented with a very short bristle inserted above the a-bristle. Seventh segment with bristles a-, b- and c-. The first one short and bare, b-bristle also relatively short and bare, with blunt tip; c-bristle long and bare with pointed tip. Segment eight with bristles d-, e-, f- and g-, all bare and almost subequally long, d- and e-bristles with blunt tips, other with pointed ones. Bellonci organ constricted medially but without a clear suture, reaching end of the third segment of A1. Both medial and lateral eyes present, medial eye is much larger and with brownish pigment,?each lateral eye with about nine omatidia ( Figure 9A ).

A2 ( Figure 9B ). Basis large and bare. Endopod reduced and one-segmented with two short and bare proximal bristles. Exopod nine-segmented. First segment longest and with a single medial, short bristle. Segments 2–8 carry bristles; the bristle on the second segment with a row of short spines proximally and setulae distally. Bristles on successive segments longer and also with proximal spines, and distal setulae. Terminal segment with two bristles, one long and only distally covered with setulae, other very short and bare.

Md ( Figure 10C ). Coxa with a row of long hair-like bristles all situated along a strongly sclerified structure. Basis lacks bristles on the dorsal margin but carries three short, bare bristles along the ventral margin. Exopod completely reduced, not even bristles present. Endopod three-segmented; each segment carrying ventro-distal, long and strongly sclerified claw. Second claw slightly serrated along its dorsal margin and terminal segment with a small spine-like bristle on basis of the claw. None of segments with any spine-like bristles on the dorsal margin.

Mxl ( Figure 9C,D ). Coxal bristle (cb) short and pappose, basal bristle (bb) also short and pappose. Exopod with two bare bristles. Endopod two-segmented: first segment distally with two strong claws, one on each side (α and β) both marginally serrated; second segment with five strong, short and serrated claws and three bristles (two a-bristles and one c-bristle), a-bristles pappose, c-bristle bare. Endite I with four strong claws (one lateral, three distal) and two spine-like bristles. Endite II with four three strong distal spines and one lateral spine-like, pappose bristle. Endite II with five strong spines.

L5 ( Figure 10D ). Epipod with 28 bristles. One coxal endite present and with one very short and bare bristle. Basis with apparently three endites: endite I clearly divided and with one bare, distal bristle, endites II and III not clearly separated from the rest of the limb and carrying two terminal bristles each. Endopod also not clearly separated from the basis and with one bare terminal bristle. Exopod represented with one bare bristle.

L6 ( Figure 10E ). Single endite with three short and bare basal bristles, and distally a semi-double row of eight pappose bristles (arranged 1 + 2 + 2 + 1 + 1 + 1) and two plumose posterior bristles. Appendage very hirsute.

L7 ( Figure 10F ). Distal part with opposing combs: one with two teeth the other with three. Two bell-like bristles inserted on the side with two teeth, and three inserted on the side with three teeth. Proximally an additional single bell-like bristle inserted on each side of the appendage.

UL ( Figure 10B ). Lamellae asymmetrical, anterior margin of the right lamella hirsute and posterior end with two spine-like extensions (labelled on the Figure 10B ) not present on the opposite lamella. Other lamella with only short setulae on the anterior margin. Each lamella with six claws, all except the most posterior one with strong secondary teeth along the margin. Claws gradually decrease in length towards posterior end and only the first claw fused with the lamella, other separated from it. “Y”-sclerite distally branching and one of the branches with additional extension on its basis ( Figure 10A ).

Males. Unknown.

Variability

The paratype female has a three bell bearing bristles on each side of the terminus on the L7.

Affinities

The new species is very similar to M. vibex Kornicker, 1991 , described from the Enewetak Lagoon (Marshal Islands) ( Kornicker 1991), both of which are less closely related to M. benthedi Kornicker, 1992 , known from the northeastern Mozambique Channel ( Kornicker 1992). Metasarsiella caleyi sp. nov. differs from M. vibex Kornicker, 1991 by: 1) having fewer bristles on the infolds of the valves; 2) having a shorter dorso-distal bristle on the fused third and fourth segments of the A1; 3) having three ventral bristles on the basis of the Md (cf. five in M. vibex ); 4) the absence of spines on the first and second endopodal segments of Md; 5) the presence of only one, instead of two bristles on the basale endite I of the L5. Both species have three bristles on the endite of the L6, but these bristles are of the same length in M. caleyi , whereas one is considerably longer than the other two in M. vibex . In addition, M. vibex has nine bristles distally on the endite of L6, whereas M. caleyi has eight. On the other hand, M. caleyi differs from M. benthedi by more prominent characters, such as 1) the presence of two bristles antero-distally on the fused third and fourth segment of the A1; 2) the presence of four bell-bearing bristles distally on the L7; 3) having a total of five distal bristles on L5 whereas M. bethedi has two bristles on the basale endite of the L5, and a total of eight distal bristles (some belonging to the endite II, some to endopod); 4) having eight distal bristles on the L6 (cf. nine in M. benthedi ). All three species are shallow-water species associated with coral reefs; both the Australian and the Marshal Islands species were collected at depths of 3–13 m, whereas the species from the Mozambique Channel was collected at 150 m.

Key to Metasarsiella Kornicker, 1991 species

1. Two bristles present antero-distally on the fused third and fourth segments of A1............................................... M. vibex Kornicker, 1991 Only one bristle present.................................................. 2

2. Basis of Md ventrally with five bristles.......... M. benthedi Kornicker, 1992 Basis of Md ventrally with three bristles................... M. caleyi sp. nov.

Figures

Figure 6. SEM photographs, Metasarsiella caleyi sp. nov., Female, Holotype: A – RV, lateral view from the outside; B – LV, lateral view from the inside; C – central scars; D – detail of the surface ornamentation; E – LV, posterior end; F; LV, postero-dorsal infold.

Figure 7. Metasarsiella caleyi sp. nov., Female, Holotype: A – RV, lateral view from the outside; B – RV, lateral view from the inside. Scales = 0.1 mm.

Figure 8. Metasarsiella caleyi sp. nov., Female, Holotype: A – LV, lateral view from the inside; B – LV, posterior end; C – RV, posterior end. Scales = 0.1 mm.

Figure 9. Metasarsiellacaleyi sp. nov., Female, Holotype: A – A1 with Bellonci Organ, medial and lateral eye; B – A2; C – Mxl, part of the basis, endopod and exopod; D – Mxl, basis and endites. Scale = 0.1 mm.

Figure 10. Metasarsiella caleyi sp. nov., Female, Holotype: A – Y-sclerite; B – UL, arrows pointing to the extensions on the posterior end of one lamella; C – Md; D – L5; E – L6; F – distal part of L7. Scales = 0.1 mm.