Cytherella rwhatleyi
In lateral view, RV and LV oval – sub-rectangular; 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 medium-sized, shallow, punctae present on almost entire valve surface except by the adductor muscle scar and ventral – anteroventral areas. Genital lobe proximally subcircular, with “beak-shaped” distal process, which is convex anteriorly and concave posteriorly. HP very elongated and relatively thin, with “heart-shaped” proximal lobe, and subtriangular distal lobe. ber). 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).
Antennula robust, with 7 podomeres, podomere 3 subtriangular; Base of antenna with barbed dorsal margin; endopodite podomere 1 with 6 (3 ventral plus 3 distal) modified setae, which lack any kind of pore indicative of chemical reception. Coxa of mandibula with 2 endites finely denticulate distally; approximatelly 60 comb setae. Endites of maxillula with numerous setae and barbae. Fifth limb strongly sexually dimorphic, endopodite well developed, hook-shaped in male and reduced in female. Sixth limb also strongly sexually dimorphic, endopodite well developed, hook-shaped in male and absent in female. Furcae a pair of lamella bearing 9 to 11 feathered setae plus 1 reduced seta. Male copulatory limb very elongated and relatively thin, with “heart-shaped” proximal lobe, and subtriangular distal lobe. Genital lobe proximally subcircular, with “beak-shaped” distal process, which is convex anteriorly and concave posteriorly. Trunk with 11 segments, males bearing several short setae and females bearing long setae. Male copulatory limb inserted in segments 5 to 7 (segment I most posterior, following Tsukagoshi et al. 2006), genital lobe inserted in segments 5 to 8.
In lateral view, RV and LV oval – sub-rectangular; 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 medium-sized, shallow, punctae present on almost entire valve surface except by the adductor muscle scar and ventral – anteroventral areas. Genital lobe proximally subcircular, with “beak-shaped” distal process, which is convex anteriorly and concave posteriorly. Hemipenis very elongated and relatively thin, with “heart-shaped” proximal lobe, and subtriangular distal lobe.
Cytherella santosensis Bergue et al. 2007 om the Late Quaternary Santos Basin (SW Atlantic, off Southeastern Brazil).
Holotype: RV L 1.03mm, H 0.58mm, LV L 1.02mm, H 0.53mm.
Paratypes: adult 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; (A-1) RV L 0.85 – 0.90mm, H 0.54 – 0.58mm; (A-?2) RV 0.72mm, H 0.42mm.
The types of Cytherella serratula (Brady, 1880) (Fig. 9) from West Indies (713m depth) can be differentiated from Cytherella rwhatleyi, 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 Cytherella rwhatleyi.
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 Cytherella rwhatleyi.
Cytherella rwhatleyi 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 2070m)
(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.
Cytherella hemipuncta Swanson, 1969 described from the Miocene of New Zealand present irregularly spaced punctae, which are larger than the punctae of Cytherella rwhatleyi.
Cytherella rwhatleyi 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 can be distinguished from the Cytherella species 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 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.
Majoran & Dingle (2001a) recorded Cytherella sp. from the Southwestern South Atlantic (Deep-Sea Drilling Project /Ocean Drilling Program sites 329, 513 and 699) (fig. 1.13). Cytherella rwhatleyi 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 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 deep-water currents.
For the soft part anatomy, I follow Horne et al., 2002 (Horne DJ, Cohen A, Martens K. 2002. Taxonomy, morphology and biology of Quaternary and living Ostracoda. In: Holmes JA, Chivas AR, editors. The Ostracoda. Applications in Quaternary Research. Washington, DC: American Geophysical Union. p 5-35.).
We use the following terms for the limbs/furca from anterior to posterior with alternative names in parenthesis:
antennula (antenna I, Aa, AI, first antenna)antenna (antenna II, AII, Au, second antenna)mandibula (mandible, Md)Maxillula (first maxilla, maxilla I, maxillule, MxI, Mxu)Fifth limb (ApV, Appendage V, first thoracic leg, maxilla, maxilla I, MxI, Mxu, maxilliped, clasper (for males), P1, second maxilla, walking leg)Sixth limb (ApVI, Appendage VI, first thoracic leg, second thoracic leg, P2, walking leg)Seventh limb (ApVII, Appendage VII, cleaning limb, P3, second thoracic leg, third thoracic leg, walking leg)Male copulatory limb (eighth limb, hemipenis, uropod). Whether the Male copulatory limb is homologous to a crustacean limb remains controvertial.Furca (caudal rami, Fu, furcal rami, uropods). The homology of the podocopan furca (anterior to the anus) to a myodocopan furca (posterior to the anus) remains controversial. Similarly, the homology of the ostracod furca to the furca of other crustaceans remains controvertial.
Antennula - 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,0-1r.1m). Antenna - Coxa (.1.1/0), Basis (0/.2-3), Exopodite 1 (0/0: 4-5), Exopodite 2 (.0-1./0:7), Endopodite 1 (0/3r.:6-7.5-6,3r), Endopodite 2+3 (.1-2.1-2/.1), Endopodite 4 (0/.1.:3). Mandibula - Exopodite (4), Endopodite I (0/0:3). Maxillula - Coxa (.1/0), Base (0/.11.4,~50c), Exopodite (~30), Endopodite 1 (.1-2/.1.1.1.1.), Endopodite 2 (0/0:3-4). Fifth limb of male—Endite (7-8,0-1r), Exopodite (~20), Endopodite 1 (0/.2.1-2), Endopodite 2 (0/.1-2.1-2.2-3), Endopodite 3 (0/.1:1,1- 2). Sixth limb of male - Exopodite (~13), Endopodite 1 (0/.1.1.), Endopodite 2 (.1l/.1.1.1), Endopodite 3 (0/.1:3); Sixth limb of female - Exopodite (~7).
Chaetotaxy formula follows Schornikov and Keyser (2004, The morphology and classification of Paradoxostomatinae (Ostracoda) from the nearshore zone of Madeira and the Canary Islands. Revista Española de Micropaleontologia 36: 57-81.) : "Figures without parentheses = podomeres numbered from proximal to distal; + = junction of podomeres. Figures within parentheses = number of setae: numerator = setae on dorsal margin; denominator = setae on ventral margin; integer figures = lateral, medial or apical armature elements, from dorsal to ventral. Figures within parentheses without indexes = normally development setae; r = rudimentary; c = claw-shaped seta or claws; s = sensory seta; p = plumose seta or ray; re = reflexed seta or ray; a = atriumwards ray; t = tooth or tooth-shaped seta; l or m = lateral or medial seta. A dot indicates the presence of an interval between setae or between podomere ends; a colon indicates apical, lateral or medial setae; hyphen indicates variable elements. Commas are used for the sake of clarity e.g. to separate symbols by unarmed podomeres or setae without indexes."
(see an example of the chaetotaxy formula in the figure "EXAMPLE CHAETOTAXY" in this species page)
207 live specimens (64 adult males, 124 adult females, 15 (A-1), 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 (A-1), (SNB 0018, 0132-4), 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 (A-1) (SNB 0688, 0690-1), 1 (A-?2) (SNB 0689), ANDEEP III, # 153 – 7 – E, ZMH K-41286;
28 adult males, 81 adult females, 4 (A-1), 1 female RLV, ANDEEP III, # 153 – 7 – S, ZMH K-41287;
2 adult males (SNB 0693-4), 13 adult females (SNB 0692, 0697-0701), ANDEEP III, # 153 – 8, ZMH K-41288.
A, adult; (A-1) (A-2) (A-3)..., juvenile stages; F, female; H, Height; L, length; LV, left valve; RLV, subfossil (= without soft parts) closed right and left valves; RV, right valve; SNB, specimen number as catalogued by the Brandão, S. N. (through this number it is possible to assign correctly the valves of a single specimen kept in a micropaleontological slide to their dissected appendages in a glass slide); ZMH, Zoologisches Institut und Museum, University of Hamburg (Germany).
2008 Cytherella rwhatleyi Brandão: 351- 361, Figs. 1-8, Tabs. 1, 2, 4.
In honour of Dr. Robin Whatley, who published many studies on fossil and recent ostracods.
Northeastern Weddell Sea and Southwestern Scotia Sea, Antarctic Region of the Southern Ocean, 938 and 2069m.
Fossils of the order Platycopida (where Cytherella rwhatleyi belongs to) where long used as indicators of watermasses with low oxygen content (the so-called Platycopid Signal). The relative abundances of Cytherella rwhatleyi in recent samples collected from the Southern Ocean suggested that the assumptions on the oxygenation of watermasses needed a reevaluation. After" a critical evaluation of the evidence from modern ostracod biology, ecology and depth distribution" Brandão & Horne (2009. Palaeogeography, Palaeoclimatology, Palaeoecology 283, 126–133) concluded that "that previously published and widely applied calibrations of platycopid abundance against dissolved oxygen levels are inadequately justified by the available data".
Brandão, 2008; Brandão & Horne, 2009 (The Platycopid Signal of oxygen depletion in the ocean: a critical evaluation of the evidence from modern ostracod biology, ecology and depth distribution. Paleogeography, Paleoclimatology, Paleoecology, 283: 126-133. (doi: 10.1016/j.palaeo.2009.09.007)
Brandão, S. N, 2008. First record of a living Platycopida (Crustacea, Ostracoda) from Antarctic waters and a Discussion on Cytherella serratula (Brady, 1880). Zootaxa, 1866, 359–382.
(this publication can be freely downloaded from http://www.mapress.com/zootaxa/2008/f/zt01866p372.pdf)