Cytherella rwhatleyi, Brandão, Simone N., 2008

Brandão, Simone N., 2008, First Record of a living Platycopida (Crustacea, Ostracoda) from Antarctic waters and a Discussion on Cytherella serratula (Brady, 1880) *, Zootaxa 1866, pp. 349-372 : 351-361

Cytherella rwhatleyi sp. nov.

( Figs. 1–8 , Tabs. 1 , 2 , 4)

Etymology. In honour of Dr. Robin Whatley, who published many studies on fossil and recent ostracods.

Material. 207 live specimens (64 adult males, 124 adult females, 15 (A­1), 1 (A­?2) + 3 specimens), 1 female RLV, 1 female RV.

Holotype – 1 adult male (SNB 0131), EASIZ II, # 89, ZMH K­ 41280.

Paratypes – 15 adult males, 10 adult females, 3 (A­1), (SNB 0 0 18, 0132­4), 1 adult female RV, EASIZ II, # 89, ZMH K­ 41282; 1 adult male (SNB 0135), 4 adult females (SNB 0136), EASIZ II, # 107, ZMH K­ 41283; 1 adult male (SNB 0159), 1 adult female (SNB 0158), ANDEEP III, # 57 – 2, ZMH K­ 41284; 1 adult male (SNB 0169), 1 adult female (SNB 0168), + 2 adult and 1 juvenile specimens, ANDEEP III, # 153 – 4, ZMH K­ 41285; 15 adult males (SNB 0170), 14 adult females, 8 (A­1) (SNB 0 688, 0690­1), 1 (A­?2) (SNB 0689), ANDEEP III, # 153 – 7 – E, ZMH K­ 41286; 28 adult males, 81 adult females, 4 (A­1), 1 female RLV, ANDEEP III, # 153 – 7 – S, ZMH K­ 41287; 2 adult males (SNB 0693­4), 13 adult females (SNB 0 692, 0697­ 0701), ANDEEP III, # 153 – 8, ZMH K­ 41288.

Distribution. Northeastern Weddell Sea and Southwestern Scotia Sea, Antarctic Region of the Southern Ocean, 938 and 2069m.

V Measurements ( Fig. 2 ). Holotype—RV L 1.03mm, H 0.58mm, LV L 1.02mm, H 0.53mm; Paratypesadult male RV L 1.01–1.08mm, H 0.57–0.61mm; adult females RV L 1.00– 1.11mm, H 0.58–0.65mm; (A­1) RV L 0.85 – 0.90mm, H 0.54 – 0.58mm; (A­?2) RV 0.72mm, H 0.42mm.

Diagnosis. In lateral view, RV and LV oval – sub­rectangular; very wide rim present on entire valve margin in males, but only on anterodorsal to ventral areas of valves in females; anterior margin more broadly rounded than posterior; pronounced selvage present, with shorter and longer radial setae. Lateral surface with medium­sized, shallow, punctae present on almost entire valve surface except by the adductor muscle scar and ventral – anteroventral areas. Genital lobe proximally subcircular, with “beak­shaped” distal process, which is convex anteriorly and concave posteriorly. HP very elongated and relatively thin, with “heart­shaped” proximal lobe, and subtriangular distal lobe.

Fossil records included only for the Antarctic region, for other regions only recent and subfossil records represented. 1 — Cytherella corpusculum Swanson et al. 2005 , Recent; 2 — Cytherella hermargentina Whatley et al. 1998 , subfossil; 3 — Cytherella hiatus Swanson et al. 2005 , Recent; 4 — Cytherella intonsa Swanson et al. 2005 , Recent; 5 — Cytherella permutata Swanson et al. 2005 , Recent; 6 — Cytherella pleistocenica Bergue et al. 2007 , Late Quaternary; 7 — Cytherella plusminusve Swanson et al. 2005 , Recent; 8— Cytherella punctata Brady, 1865 , Recent???; 9— Cytherella santosensis Bergue et al. 2007 , Late Quaternary; 10— Cytherelloidea megaspirocostata Majoran & Widmark, 1998 , Upper Cretaceous (from Fauth et al. 2003); 11 — Grammcythella dyspnoea Swanson et al. 2005 , Recent; 12 — Inversacythella tanantia Swanson et al. 2005, Recent ; 13–17 — Cytherella spp. (as C. serratula (Brady, 1880)) , Paleocene to Recent; 18— Cytherella spp.—as C. cavernosa , C. cingulata , C. polita , C. punctata , and C. pulchra from the first report on the Challenger expedition ostracods ( Brady 1880), Recent; 19–26 — Cytherella spp., Upper Cretaceous to Recent; 27 — Cytherelloidea sp., Late Cretaceous to Oligocene; 28 — Cytherella rwhatleyi sp. nov., Recent.

Bibliographical Sources: 1, 3–5, 7, 11, 12— from Jellinek & Swanson (2003) and Swanson et al. (2005); 2 —from Bergue et al. (2007), Whatley & Cusminsky (2002), and Whatley et al. (1996, 1997,1998); 6, 9, 17 —from Bergue et al. (2007); 8— from Chapman (1919); 10— Cytherelloidea megaspirocostata Majoran & Widmark, 1998 , Upper Cretaceous (from Fauth et al. 2003); 13 —from Brady 1880; 14 —Quaternary, from Dingle et al. (1990); 15 —Eocene, from Majoran & Dingle (2002); 16 —Palaeocene to Oligocene, Majoran & Dingle (2002); 18 —Recent, Brady, 1880; 19 —Oligocene, from Dingle & Majoran (2001); 20 —Upper Cretaceous, from Fauth et al. (2003); 21 —Quaternary, from Dingle et al. (1990); 22 —Eocene, from Majoran & Dingle (2001b); 23 —subfossil, from Mazzini (2005); 24 —Late Cretaceous, from Majoran et al. (1997); 25 — Peypouquet & Benson (1980); 26 —subfossil, from Whatley et al. (1997, 1998); 27 —Eocene to Oligocene, from Majoran & Dingle (2002); 28 —Recent, herein.

Station Polarstern Project Date Time Latitude Longitude Depth Gear Sediment

(m)

Expedition S begin S end W begin W end

NI—no information available. For other abbreviations see Material and Methods.

Description. In Lateral view, RV and LV oval to sub­rectangular; very wide rim present on entire valve margin in males, but only on anterodorsal to ventral areas of valves in females (because of the posterior inflated form due to the brood chamber); dorsal margin fairly straight; ventral margin slightly concave in females and concave in males; anterior margin more broadly rounded than posterior. Pronounced selvage present, with shorter and longer radial setae. Lateral surface punctate, punctae medium­sized, shallow, and present on almost entire valve surface except by the adductor muscle scar and ventral­anteroventral areas; one to three slight, small tubercles (related to muscle insertions on interior surface of valves) present on mid­dorsal area of lateral surface. Maximum height anterior to midlength; in males greatest length at mid­height, and greatest width at mid length; in females, greatest length inferior to mid­length, and greatest width posterior to mid­length. Few, very long setae arising from carapace posterior; shorter, simple or feathered setae arising from simple, “bean­shaped” to circular, lateral pore canals. RV slightly larger and overlaping LV mid­dorsally. In dorsal view, males with sinuous outline (due to wide rim), females with subtriangular outline (due to brood chamber). Adductor muscle scars composed by 2 vertical rows, each with six scars, plus one dorsal scar. Sexual dimorphism pronounced; females higher in relation to length and wider than males; female with inflated posterior (=brood chamber) without limen (ridge or elevation forming the anterior boundary of brood chamber). Females brooded from 0 to 6 eggs, with a maximum of 3 eggs per valve ( Fig. 6, Tab. 2 ), in average 3.6 eggs / female; exact position of single eggs in brood chamber also varied (ventral, medial or dorsal).

AI robust, with 7 podomeres, podomere III subtriangular; chaetotaxy 1(0/.3.1.1), 2(.1r/.3), 3(.1/1r), 4(.3/ 0:1,1,1), 5(0/0:2,1), 6(. 1m,1r/0:2l), 7(0/0: 3m,0­1r. 1m). Base of AII with barbed dorsal margin; endopodite podomere I with 6 (3 ventral plus 3 distal) modified setae, which lack any kind of pore indicative of chemical reception; chaetotaxy—Coxa (.1.1/0), Basis (0/.2­3), Exopodite I (0/0: 4­5), Exopodite II (.0­1./0:7), Endopodite I (0/3r.:6­7.5­6,3r), Endopodite II+III (.1­2.1­2/.1), Endopodite IV (0/.1.:3). Coxa of Md with 2 endites finely denticulate distally; approximatelly 60 comb setae; chaetotaxy—Exopodite (4), Endopodite I (0/0:3). Endites of MxI with numerous setae and barbae; MxI chaetotaxy—Coxa (.1/0), Base (0/.11.4,~50c), Exopodite (~30), Endopodite I (.1­2/.1.1.1.1.), Endopodite II (0/0:3­4). ApV strongly sexually dimorphic, endopodite well developed, hook­shaped in male and reduced in female; chaetotaxy of ApV of male—Endite (7­8,0­1r), Exopodite (~20), Endopodite I (0/.2.1­2), Endopodite II (0/.1­2.1­2.2­3), Endopodite III (0/.1:1,1­ 2). ApVI also strongly sexually dimorphic, endopodite well developed, hook­shaped in male and absent in female; chaetotaxy of ApVI of male—Exopodite (~13), Endopodite I (0/.1.1.), Endopodite II (.1l/.1.1.1), Endopodite III (0/.1:3); chaetotaxy of ApVI of female—Exopodite (~7). Fu a pair of lamella bearing 9 to 11 feathered setae plus 1 reduced seta. HP very elongated and relatively thin, with “heart­shaped” proximal lobe, and subtriangular distal lobe. Genital lobe proximally subcircular, with “beak­shaped” distal process, which is convex anteriorly and concave posteriorly. Trunk with 11 segments, males bearing several short setae and females bearing long setae. HP inserted in segments V to VII (segment I most posterior, following Tsukagoshi et al. 2006), genital lobe inserted in segments V to VIII.

A, C, E, G, I, K, RV ev; B, D, F, H, J, L, LV ev; M, RV and LV dv; N, RLV dv; O, RLV vv; P, adductor muscle scars.

A, B, paratype adult female (ZMH K­41282, SNB 0018); C, D, paratype adult female (ZMH K­41283, SNB 0136); E, F, paratype adult female (ZMH K­41285, SNB 0168); G, H, M, holotype adult male (ZMH K­41280, SNB 0131); I, J, paratype adult male (ZMH K­41283, SNB 0135); K, L, paratype adult male (ZMH K­41286, SNB 0170); N, paratype adult female (ZMH K­41288, SNB 0696); O, paratype adult female (ZMH K­41288, SNB 0695). Scale bars: A­O, 500µm; P, 20 µm.

A, C, G, LV iv; B, D, H, K, RV iv; E, I, RV ev; F, J, LV ev; L, ornamentation of medio­dorsal area of external surface of RV; M, long setae and ornamentation on posterior of RV; N, chitin mesh of outer lamella; O, detail of a muscle scar; P, Q, selvage iv; R, chitin fibres beneath the endocuticule of the outer lamella; S­U, sensilla.

A, B, paratype adult male (ZMH K­41282, SNB 0133); C, D, paratype adult female (ZMH K­41282, SNB 0018); E, F, paratype (A­1) (ZMH K­41286, SNB 0688); G, H, paratype (A­1) (ZMH K­41286, SNB 0691); I, J, S, T, paratype (A­?2) (ZMH K­41286, SNB 0689); K, P, paratype adult female (ZMH K­41286, SNB 0692); L, paratype adult male (ZMH K­41286, SNB 0170); M, paratype adult female (ZMH K­41283, SNB 0136); N, O, Q, R, paratype adult female (ZMH K­41288, SNB 0697); U, paratype adult female (ZMH K­41283, SNB 0136). Scale bars: A­K, 500µm; L, P, 50 µm; M, 100 µm; N, 500 nm; O, 5 µm; Q, S­U, 10 µm; R, 1 µm.

Remarks. Several specimens from the ANDEEP # 153­7 were parasited by?fungi and?bacteria ( Fig. 6.L­ N).

The types of Cytherella serratula ( Brady, 1880) ( Fig. 9 ) from West Indies (713m depth) can be differentiated from Cytherella rwhatleyi sp. nov., because the last species has a more quadrate outline, with straighter posterodorsal margin, punctuate external surface (anteriorly and posteriorly) and do not present small tubercles in the posterior part of valves.

The only other known recent Subantarctic (Atlantic Sector) species, Cytherella hermargentina Whatley et al. 1998 (Fig. 1.2 herein), is comparatively higher with more rounded outline than the new species.

Swanson et al. (2005) described seven new species and two new genera of Cytherellidae from the Tasman Sea and from the Indic / Pacific sector of the Southern Ocean (Fig. 1.1, 3, 4, 5, 6, 8, 9). Five of these species belong to the genus Cytherella : C. hiatus Swanson et al. 2005 , C. intonsa Swanson et al. 2005 , C. corpusculum Swanson et al. 2005 , C. plusminusve Swanson et al. 2005 , C. permutata Swanson et al. 2005 . These last five species lack wide rim on the lateral surface of valves, an important diagnostic character of the new species decribed here.

Cytherella rwhatleyi sp. nov. differs from the Cytherella species recorded by Whatley & Coles (1987) (as C. serratula ) from the Quaternary of North Atlantic (Deep Sea Drilling Project, site 607, 3427m) (Fig. 6.7), in ornamentation (punctuation on the entire valve surface versus tubercles just on the posterior), and shape of the dorsal margin (fairly straight versus slightly convex), and the posterior margin (steeper dorsally versus subhemispherical).

Dingle et al. (1989, 1990) also reported [sic] C. serratula from Southeastern Atlantic (1000 to 2070 m) (Fig. 1.10) and Mazzini (2005) illustrated a similar species from Emerald Basin (Southern Ocean, Indic – Pacific Sector) ( Fig. 1 . 18). Both species lack surface punctation, are much higher in relation to length, and present more broadly rounded RV and more narrowly rounded posteroventral margin than C. rwhatleyi sp. nov.

Cytherella hemipuncta Swanson, 1969 described from the Miocene of New Zealand present irregularly spaced punctae, which are larger than the punctae of Cytherella rwhatleyi sp. nov. Cytherella rwhatleyi sp. nov. is similar in shape to C. cf. hemipuncta Swanson, 1969 recorded by Ayress (1995) from the Eocene of New Zealand, but the latter lacks the wide rim on the lateral valve surface.

Cytherella rwhatleyi sp. nov. can be distinguished from the Cytherella s pecies recorded by Majoran & Dingle (2002) from the Maud rise (Weddell Sea) (Fig. 1.14), owing to the more subquadrate outline and relatively straight dorsal margin of the former.

Cytherella sp. 4796 from the Oligocene of Victoria Land Basin, Antarctica (77S, 63E) (Dingle & Majoran, 2001) (Fig. 1.11) has a more rounded outline than the new species described herein.

The oldest record of a cytherellid in Antarctica dates from the Campanian (Upper Cretaceous) of James Ross Island, where Fauth et al. (2003) recorded two undescribed Cytherella species (Fig. 1.12). Cytherella sp. 1 resembles C. rwhatleyi sp. nov in outline, but the former has a more concave ventral margin, whereas the outline of C. sp. 2 is much more rounded than that of the new species. Furthermore, both cretaceous species lack the conspicuous rim of C. rwhatleyi sp. nov.

Majoran & Dingle (2001a) recorded Cytherella sp. from the Southwestern South Atlantic (Deep­Sea Drilling Project /Ocean Drilling Program sites 329, 513 and 699) (fig. 1.13). Cytherella rwhatleyi sp. nov. has a more quadrate outline and straight dorsal margin, while C. sp. ( Majoran & Dingle 2001a, pl. 1.6) is more rounded with a convex dorsal margin.

Cytherella pleistocenica Berge et al. 2007 differs from the new species described herein by the absence of the wide rim of valves.

Cytherella rwhatleyi sp. nov. is very similar to Cytherella santosensis Bergue et al. 2007 described from the Late Quaternary Santos Basin (SW Atlantic, off Southeastern Brazil) in the presence of the wide rim on the anterior, ventral and posterior areas of the valve surface (Fig. 1.20), but the outline of the former species is more equilateral, with less broadly rounded anterior margin. Furthermore, the centrodorsal area of lateral surface is more steeply elevated and the ornamentation is stronger in C. rwhatleyi than in C. santosensis . The similarity between these two spp. (valve outline, wide rim, and punctate lateral surface), one in the Southern Ocean, the other occurring in the Southwestern Atlantic demonstrates a possible migration route, made facilitated by the deep­water currents. A large quantity of the deep waters in the world has its origin in the Weddell Sea, where the new sp. described herein occurs. There the surface water is cooled and sinks to the ocean bottom, migrating then northwards in the Atlantic, Pacific and Indic Oceans ( Tomczak & Godfrey 2002). Otherwise it seams that the velocity, and probably also the frequency, in which the migration occurs is not high enough to maintain the genetic flux between two populations, one in the South Atlantic and the other in the Weddell Sea. As a consequence of that, allopatric speciation occurred and we observe similar but easily differentiable species, one in the Atlantic and the other in the Weddell and Scotia Seas.

A, C, modified setae of AII (not aesthetasc); B, AII; D, Md; E, Md endites; F, MxI and female ApV; G, male ApV; H, Fu; I, posterior of female (showing body segementation, posterior dimorphic setae, genital lobe, Fu and eggs); J, genital lobe; K, details of distal part of posterior dimorphic setae (inserted on posterior segments of body); L­N, body posterior and comb setae of specimen parasited by?fungi and?bacteria.

A­F, H, K, paratype adult female (SNB 0698); G, paratype adult male (ZMH K­41288, SNB 0694); I, J, paratype adult female (SNB 0699); L­N, paratype adult female (SNB 0697). All ZMH K­41288. Scale bars: A, E, F, J, K, L, 10µm; B, D, G, H, 50 µm; C, M, 5 µm; I, 100 µm; N, 500 nm.

A, C, RV ev; B, D, LV ev; E, AI, F, AII, G, Md; H, MxI (ventral setae not shown); I, MxI (comb setae not shown); J, female ApVI. A, B, paratype adult female (ZMH K­41284, SNB 0158); C, D, paratype adult male (ZMH K 41284 , SNB 0159); E­G, holotype adult male (ZMH K­41280, SNB 0131); H, I, paratype adult female (ZMH K­41282, SNB 0134); J, paratype adult female (ZMH K­41283, SNB 0136). Scale bars: A­D, 500µm; E­J, 100µm.

A, male ApV; B, male ApVI; C, furca; D, genital lobe; E, Posterior dimorphic setae; F, hemipenis; G, brush­shaped organ. A, B, G, F, holotype adult male (ZMH K­41280, SNB 0131); C­E, paratype adult female (ZMH K­41282, SNB 0134). Scale bars: 100 µm.

Figures

FIGURE 1. Previous records of Platycopida in the Southern Ocean and vicinities.

FIGURE 2. Length: height scatter plot of adult and juvenile valves of Cytherella rwhatleyi sp. nov.

FIGURE 9. Valves of Cytherella serratula (Brady, 1880) (lectotype and paralectotype) and Cytherella sp. Cytherella serratula (Brady, 1880) – Lectotype RV (BM 80.38.113): A, B, posterior ornamentation; C, ev; D, pore canals. Paralectotype LV (BM 80.38.113): LV; E, ev; F, G, posterior ornamentation.

Tables

TABLE 1. Stations with samples containing Cytherella rwhatleyi sp. nov.

89	PS48/ANTXV­3 EASIZ II 0 4.02.98 10:24	73°27.26'	73°27.27'	22°45.67'	22°46.52'	1645	EBS	NI
107	PS48/ANTXV­3 EASIZ II 0 6.02.98 8:24	73°34.77'	73°34.92'	22°38.29'	22°38.89'	938	EBS	fine gravel
57­2	PS67/ANTXXII­3 ANDEEP III 10.02.0 5 18:44	69°24.15'	69°24.63'	5°18.40'	5°19,70'	1812	AGT	NI
153­4	PS67/ANTXXII­3 ANDEEP III 29.03.0 5 08:52	63°19.35'	­	64°36.79'	­	2079	GKG	72% silt, 13% sand, 15% clay
153­7	PS67/ANTXXII­3 ANDEEP III 29.03.0 5 13:33	63°19.83'	63°19.19'	64°36.44'	64°37.52'	2011	EBS	72% silt, 13% sand, 15% clay
153­8	PS67/ANTXXII­3 ANDEEP III 29.03.0 5 16:37	63°19.53'	63°19.06'	64°36.79'	64°37.23'	2069	AGT	72% silt, 13% sand, 15% clay

TABLE 2. Number of eggs brooded by single females of Cytherella rwhatleyi sp. nov. in the different stations.

LV RV # 89	# 107	# 153	Total
0 0 0	0	10	10
0 1 0	0	3	3
0 2 0	0	2	2
1 0 2	1	2	5
1 1 0	0	6	6
1 2 0	1	5	6
1 3 0	0	3	3
2 0 0	0	1	1
2 1 0	1	2	3
2 2 1	0	12	13
2 3 2	0	13	15
3 1 0	0	2	2
3 2 0	0	17	17
3 3 0	0	9	9
Total 5	3	87	95
For abbreviations see Material and Methods.