Macroscapha solecavai
Carapace quite 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; posterodorsal margin concave; posterior angle acute. 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. Antennula and antenna with relatively long, slender podomeres and setae. Very slight suture between podomeres II and III of antennula visible only ventrally. Length of podomere IV of antenna less than two times length of podomere III. Exopodite of mandibula with one reduced, plus seven medium-sized setae. Vibratory plate of maxillula with two long and one short strahlen, basal endite with two long, ventral setae. Exopodite of fifth limb with three proximal and six to eight distal setae; podomere V of female fifth limb (= palp podomere IV) with short and thick, terminal claws, dorsal one shortest, medial and dorsal ones medium-sized, 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 seta, and one long plus one medium-sized claw. Furca with barbed, symmetrical, with thick rods; terminal setae thick and short; no suture between terminal setae and rods. Hemipenis subtrapezoidal; copulatory process trisegmented, with hook-shaped terminal element; distal tip of posterior ramus fairly straight. Zenker’s organ with robust, fairly thick central tube and medium-sized terminal bulb; vas deferens arranged in few loops, which are shorter than the length of the chitinous tube.
Carapace quite large (for the genus); lateral outline subtrapezoidal, slightly sinuous, especially posterodorsally, rectilinear; anterior and posterior margins narrowly rounded. In all specimens studied herein, LV larger than, and overlapping, RV anterodorsally, posterodorsally, and ventrally. Podomere IV of female fifth limb with short and thick, terminal claws, dorsal slightly shorter, other two claws subequal in length and thickness. Furca with symmetrical rods. Hemipenis subtrapezoidal; copulatory process trisegmented, with hook-shaped terminal element; distal tip of posterior ramus fairly straight. Zenker’s organ with robust, fairly thick central tube and medium-sized terminal bulb; vas deferens arranged in few loops, which are slightly shorter than the length of the chitinous tube.
Several specimens of this species had different regions (COI, ITS and 16S) of their genome sequenced by my self and colleagues. These sequences are available from the GenBank website.
Macroscapha solecavai is most similar to the species included in the informal group Macroscapha tensa-opaca (see below).
V Measurements (Fig. 45.B). Holotype, RV L 2.14mm, H 0.75mm; LV L 2.15mm, H 0.76mm. Paratypes, A F LV 2.10-2.21mm, H 0.76-0.81mm; A M LV 2.10-2.20mm, H 0.74-0.81mm; (A-?1?2) LV 1.64-1.74mm, H 0.60-0.64mm; (A-?3?4) LV L 1.03mm, 0.36mm.
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.
From the other five species of the group Macroscapha tensa-opaca, Macroscapha solecavai (from the Powell Basin, Atlantic Sector of the Southern Ocean) is most similar to Mh. falcis (from the eastern Weddell Basin, also in the Atlantic Sector of the Southern Ocean). These last 2 species differ genetically (Brandão et al., 2010. Circumantarctic distribution in Southern Ocean benthos? A genetic test using the genus Macroscapha (Crustacea, Ostracoda) as a model. Molecular Phylogenetics and Evolution), and morphologically in size and hemipenis. 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). Additonally, 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.
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(0/.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,+10), palp 1(.1/0), 2(.4/0), 3(0/0:6). Fifth limb 1(0/0:1.1), Exopodite (0/0:3.6-8), [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)
35 live specimens plus three valves.
Holotype: 1 A F (SNB 0204) (soft parts in glass slide, valves in micropalaeontological slide), ANDEEP III, # 151-1, ZMH K-41500.
Paratypes: 2 A F (SNB 0563-DNA 270, SNB 0566- DNA 273), 6 A M (SNB 0559-0562-DNA 266-269, SNB 0564-DNA 271, SNB 0565-DNA 272), 3 (A-?1?2) (SNB 0567-DNA 274, SNB 0568-DNA 275), ANDEEP III, # 151-1, ZMH K-41499; 4 A F (SNB 0527-0530), 9 A M (SNB 0514-0522-DNA 221-229), 2 (A-1) (SNB 0531- 0532), 1 A LV, 1 A RV, 1 (A-?3) LV, ANDEEP III, # 151-7-E; 5 A F (SNB 0523-0525-DNA 230-232, SNB 0526), 3 A M (SNB 0511-0523-DNA 218-220), ANDEEP III, # 151-7-S, ZMH K-41498.
A, adult; (A-1), (A-2), (A-3), juvenile instars; DNA, DNA extraction number as catalogued by the Brandão, S. N.; 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); #, station number.
In honour of Prof. Dr Antonio Mateo Solé-Cava (Universidade Federal do Rio de Janeiro, Brazil), for his important contributions to the genetics of marine organisms.
Recent. Powell Basin, Southern Ocean, from 1178 to 1187 m depth.