Macroscapha falcis
Carapace large (for the genus); lateral outline subtrapezoidal, slightly sinuous, rectilinear; dorsal angle quite conspicuous; posterodorsal margin of LV conspicuously sinuous; posterior angle acute in RV, more obliquely rounded in LV; ventral margin slightly sinuous; anterior margin narrowly rounded. Vestibules wide; zone of concrescence fairly narrow; radial pore canals straight. In all specimens studied herein, LV larger than, and overlapping, RV anterodorsally, posterodorsally, and ventrally. Females higher in relation to length than males.
Antennula and antenna with slender podomeres and setae. Podomeres II and III of antennula fused, no suture visible. Length of podomere IV of antenna less than two times length of podomere III. Exopodite of mandibula with one reduced and seven medium sized setae. Vibratory plate of maxillula with one short and two long strahlen plus around 15 feathered setae, basal endite with two ventral setae; other endites without basal setae. Exopodite of fifth limb with three proximal setae and seven distal setae; podomere V of female fifth limb (= palp podomere IV) with short and thick terminal claws, dorsal one shortest, medial and dorsal ones long, subequal. Male fifth limb very asymmetrical, right appendage with one very long, and thick modified seta (= peg), plus one short, modified seta (= peg), and one short, simple seta on podomere II (palp podomere I); podomere III smoothly curved; left appendage with two short, modified setae (= pegs), and one short, simple seta on podomere II (palp podomere I); podomere III pointed at 90°. Podomere VI of sixth limb with one very short and one short setae, and one long claw. Furca with barbed, symmetrical, with thick rods; terminal setae thick and short; slight suture between terminal setae and rods. Male copulatory limb very high in relation to length and strongly curved; copulatory process trisegmented, proximal element thick, robust, rod-shaped; weakly sclerotized, large, irregularly shaped medium element; and a hook-shaped terminal element, distal tip of posterior ramus of hook sinuous. Zenker’s organ with robust central tube and medium-sized terminal bulb; vas deferens arranged in few loops, which are shorter than the length of the chitinous tube.
Carapace large (for the genus); lateral outline subtrapezoidal, slightly sinuous, rectilinear; anterior and posterior margins narrowly rounded. In all specimens studied herein, LV larger than, and overlapping, RV anterodorsally, posterodorsally, and ventrally.
Podomere V of female fifth limb (= palp podomere IV) with short and thick, terminal claws, dorsal one shortest, medial one longest. Furca with symmetrical rods. Male copulatory limb very high in relation to length in lateral outline; copulatory process trisegmented, with hook-shaped terminal element; distal tip of posterior ramus of hook sinuous. Zenker’s organ with robust central tube and medium-sized terminal bulb; vas deferens arranged in few loops, which are shorter than the length of the chitinous tube.
Macroscapha falcis is most similar to the species included in the informal group Macroscapha tensa-opaca (see below).
Valve measurements: Holotype, RV L 2.28 mm, H 0.84 mm; LV L 2.30 mm, H 0.86 mm. Paratypes, A F LV 2.29–2.34 mm, H 0.83–0.87 mm; A M LV 2.32–2.48 mm, H 0.80–0.87 mm; (A–1) LV 1.75–1.92 mm, H 0.62–0.70 mm; (A–2) LV L 1.40–1.42 mm, 0.50–0.51 mm.
The informal species group Macroscapha tensa-opaca includes the following species: Mh. opaca Maddocks, 1990, Mh. cactus Brandão, 2010, Mh. falcis Brandão, 2010, and three new but unnamed species (Mh. tensa was considered a nomen dubium).
This species group is characterized by:
(1) an elongate, often rectilinear outline, with acutely pointed posterior angle;
(2) podomeres IV and V (= palp podomeres III and IV) of the female fifth limb present medium-sized, thick claws;
(3) symmetrical furcal rods;
(4) ‘reverse’ valve overlap; the LV is larger than and overlaps the RV ventrally, antero-, and posterodorsally. Noteworthly, in only the adult and juvenile females of Mh. opaca from the Ross Sea (stations ‘H in 4’ and ‘H in 5’), the right valves are always larger than and overlap the left valves;
(5) the hemipenises are subtrapezoidal with a copulatory process composed of three segments, the most proximal one is elongate, fairly straight, and quite invariable amongst species; the second and third segments are shorter and vary greatly in shape. These two latter segments are the most important characters differentiating amongst the species of the informal group Macroscapha tensa-opaca.
Additionally, Macroscapha falcis sp. nov. (from the eastern Weddell Basin) is very similar to, Mh. solecavai sp. nov. (from the Powell Basin and described below). Otherwise, genetic (S. N. Brandão & I. Schön, unpubl. data) and morphological differences justify the description of both new species. Macroscapha solecavai is smaller (adult LV length from 2.10 to 2.24 mm), more rectilinear in valve outline, and has a more acute posterior angle than Mh. falcis (adult length 2.30 to 2.40 mm) (Figs 47, 48). Furthermore, the hemipenis of the former species is higher in relation to length, and shows a more sinuous distal tip of the posterior ramus of the hook-shaped copulatory process (Figs 44B–C, 52A–D, 52G–K).
The valve lateral outline of Mh. falcis sp. nov. diverges from other previously described Macroscapha species in: (1) it is more subtriangular and rectilinear than Mh. atlantica, Mh. gyreae Mh. heroica, Mh. jiangi, Mh. inaequalis, Mh. inaequata, Mh. marchilensis, Mh. opaca, Mh. sinuata, Mh. rehmi sp. nov., Mh. scotia sp. nov., Mh. turbida, and Mh. walterae sp. nov.; (2) more narrowly rounded anterior margin and more acutely pointed posterior margin than Mh. tensa (based on drawings of the lost lectotype; Maddocks, 1990: figs 14.2, 15.2).
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(0/0:4). Antenna 1(.1/:1), 2(0/ 0:1), Exopodite (0/0:2,1r), 3(0/.6.4), 4[female (.2r./ .2r.1c,2)] [male (.1r./.1r.1c,2mod,1)], 5(0/.1c,1:4c,1), 6(0/0:2c,2). Mandibula 1(.1./4t,+5.), 2(0/.2:1), Exopodite (0/0:1r,7), 3(0/.4:4), 4(.3.2/.4), 5(0/0:3c,3). Maxillula vibratory plate (3re,+16), palp 1(.1/0), 2(.4/0), 3(0/0:6). Fifth limb 1(0/.1:0-1), Exopodite (0/0:3.7), [female 2, 3, 4(0/.1) 5(.1./0:1c,1)]; [male 2(.1r/2mod,1), 3(0/ 0:1mod)]. Sixth limb 1(.2/0), 2(.2.1/.1), 3(.1/.0), 4(.1/0), 5(1,1r/0) 6(0/0:1,2c). Seventh limb 1(0/0:1), 2(.1.1.1/1) 3(.1/0), 4(.1/0), 5(.2/0), 6(0/0:2,1re). Furca 1(0/0:3r.1).
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).
live specimens plus 14 valves.
Holotype: 1 A F (SNB 0854) (soft parts in glass slide, valves in micropalaeontological slide), ANDEEP III, # 74-6-S, ZMH K-41497.
Paratypes:15 A F (SNB 0852-0853), 35 A M (SNB 0100-DNA 3, SNB 0102-0104-DNA 5-7, SNB 0108- DNA 11, SNB 0464-0477-DNA 171-184, SNB 0483- 0494-DNA 190-201) 23 (A-1), 2 (A-2), nine live specimens (SNB 0810-0819), 5 RV, 5 LV, 2 RLV, ANDEEP III, # 74-6-E; 1 A F, 4 (A-1), ANDEEP III, # 74-6-S, ZMH K-41496.
A, adult; (A-1), (A-2), (A-3), juvenile instars; F, female; H, Height; L, length; LV, left valve; M, male; 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); V, valve; ZMH, Zoologisches Institut und Museum, University of Hamburg (Germany); ZMH K-, abbreviation of the Crustacea collection of the Zoologisches Institut und Museum, University of Hamburg (Germany); #, station number.
2010 Macroscapha falcis Brandão: Figs. 43, 44B, 45B, 47D–F, 47Q, 48D–F, 49C–D, 49G–H, 49Q, 51B–E, 52A–D, 52.1.
From the Latin, falcis = hook (name used in apposition) because of the hook-shaped copulatory process of the hemipenis.
Only known from the type locality in the Western Weddell Sea, 1040–1048m. Recent.
Brandão, S. N., in press. Macrocyprididae (Ostracoda) from the Southern Ocean: taxonomic revision, macroecological patterns, and biogeographical implications. Zoological Journal of the Linnean Society.