Macromckenziea giambonini
Description. Carapace medium-sized for the genus, non-equilateral, elongate in lateral outline, narrow zone of concrescence with straight radial pore canals, calcified inner lamella narrow. Greatest height at midlength in RV and anterior to mid-length in LV. Length approximately 2.3 times maximum height. RV larger than LV. Anterior margin of both valves narrowly rounded, dorsal margin gently arched, posterior margin rounded, ending in 90º posterior angle. Ventral margin straight in RV, and slightly concave in LV. Anterodorsal margin fairly straight in RV, slightly concave in LV. Antennula robust, thick, tapering, with 7 podomeres; Podomere II and III flexibly articulated. Antenna compact, thick-proportioned, tightly curled, with 6 podomeres; podomere IV short and thick. Mandibula with a broad masticatory jaw armed with one dorsal, conical tooth followed by four tricuspidate teeth and several setae. Maxillula with three slender endites, each armed distally with a dense fringe of subequal claws, ventral endite with 2 proximal setae on ventral margin, other 2 endites without proximal setae; vibratory plate with 1 strahlen and ~14 to ~17 feathered setae; palp slender, flexible; podomeres I and II fused, dorsal seta of podomere I absent). Exopodite of female fifth limb with 7 setae; podomeres IV and V with long and thin setae, mid-distal seta conspicuously longer than other 3 setae. Podomere IV and V of sixth limb short; podomere VI elongate, with 2 subequal, medium-sized, distal claws and one short distal seta. Seventh limb thin and small; podomere V with 2 ventrodistal, medium-sized setae, the most ventral one shortest; and with one very short reflexed-seta. Furca very small, each rod flexible and bearing 2 tiny proximal setae and one terminal, short seta.
Abbreviations: LV, left valve; RV, right valve.
Carapace medium-sized. In lateral view, elongate; with slightly arched dorsal margin; and straight (RV) or slightly concave (LV) ventral margin; posterior margin pointed at 90°. Zone of concrescence very narrow with short, straight radial pore canals. Podomeres I of maxilla I without seta. Podomere V of female appendage V with very long mid-distal seta. Furca reduced, with 2 rods, each rod flexible and bearing 2 tiny proximal setae and one terminal, short seta.
Few COI, ITS and 16S sequences were obtained by myself and collaborators and will be soon available in the GenBank.
Valves of females of Macromckenziea giambonini Brandão, 2010 are very similar to the valves of males of Macromckenziea glacierae Maddocks, 1990.
Holotype, A F, RV L 1.56mm, H 0.68mm; LV L 1.54mm, H 0.64mm.
Paratypes, A F, RV, L 1.56-1.60mm, H 0.68-0.70mm; (A-1) RV, L 1.34-1.38mm, H 0.56-0.60mm.
Macromckenziea giambonini Brandão, 2010 fits well in the description of the genus Macromckenziea except for the furca, which is more similar to the genera Macrocypris Brady, 1868 and Macropyxis Maddocks, 1990. In Macromckenziea giambonini the furca is less reduced than the furca of the other species in Macromckenziea. In this character, Macromckenziea giambonini Brandão, 2010 differs from all other species of Macromckenziea, for which the appendages have been figured-Macromckenziea glacierae, Macromckenziea ligustica and Macromckenziea siliquosa (Maddocks 1990. Fig. 46.20-34). Additionally, Macromckenziea australiana, Macromckenziea glacierae, Macromckenziea gregalis, Macromckenziea porcelanica, and Macromckenziea swansoni are more subtriangular, higher in relation to length than Macromckenziea giambonini Brandão, 2010 Furthermore, Macromckenziea glacierae presents a more pointed posterior angle than Macromckenziea giambonini Brandão, 2010 Macromckenziea ligustica and Macromckenziea siliquosa have more sub-parallel ventral and dorsal margins, more straight dorsal margin and more sinuate ventral margin than Macromckenziea giambonini Brandão, 2010 The valves of Macromckenziea sp. 3 from Maddocks (1990: 56), which was recorded from the Drake Passage (240m), are very similar to the Macromckenziea giambonini Brandão, 2010, but smaller (gray triangle in Fig. 7), with a slightly more truncated anterior margin, and its antenna I is more robust, with the podomeres wider in relation to length than in Macromckenziea giambonini Brandão, 2010 Macropyxis andreseni and Macropyxis sonneae, from the Pacific Sector of the Southern Ocean, present similar carapace outlines, but are higher in relation to length, and present well developed furca, while in Macromckenziea giambonini Brandão, 2010 the furca is reduced.
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, 2(0/.2), 3(.1/.1.), 4(.1/.1.), 5(.1/.1), 6(.2/.3), 7(0/0:3-4). Antenna 1(0/0:1), 2(0/0:1), Exopodite (0/0:2,1r), 3(0/5.:5), 4(.2/.1c:3), 5(0/.1,1c:1.3c), 6(0/0:4c,1s). Mandibula 1(0/5t,+5:.1.), 2(0/.2), Exopodite (0/0:5), 3(0/5:1), 4(5/4), 5(.2./0:3). Maxillula I vibratory plate (1re,~14-16), palp 1+2(4/0), 3(0/0:5). Female fifth limb 1, Exopodite (.3./0:4), 2, 3, 4(0/1), 5(0/0:3). Sixth limb 1(0/.1), 2(.1/.1.1.1), 3(0/.1), 4(0/.1), 5(0/.1), 6(0/0:2c,1). Seventh limb 1+2(.1/.1), 3(0/1), 4(0/1), 5(0/1), 6(0/0:1.1r,1). Furca 1(0/0:1.2r).
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)
8 live specimens:
Holotype: 1 A F (SNB 0030) (soft parts in glass slide, valves in micropalaeontological slide), EASIZ II, # 107, ZMH K-40809.
Paratypes: 3 A F (SNB 0029, 0031, 0032) (valves in micropalaeontological slide, soft parts in glass slide) and 4 (A-1) (in alcohol 90%), EASIZ II, # 107, ZMH K-40810.
A, adult; (A-1), last juvenile instar; F, female; H, Height; L, length; LV, left valve; RV, right valve; SNB, specimen number as catalogued by the Brandão, S. N. (throught 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); #, station number.
In honour of Diego Giambonini for his immense support.
Recent. Eastern Weddell Sea, Atlantic Sector of the Southern Ocean, from 924 to 934m.
Brandão, S. N., in press. Macrocyprididae (Ostracoda) from the Southern Ocean: taxonomic revision, macroecological patterns, and biogeographical implications. Zoological Journal of the Linnean Society.