Malawidopsis ruwaydae, Jacobs & Martens, 2022
Jacobs, Bram & Martens, Koen, 2022, An endemic species flock of Cypridopsinae (Crustacea, Ostracoda) from the ancient Lake Malawi (Africa), with the description of a new genus and three new species, Zootaxa 5100 (3), pp. 301-348 : 317-324
treatment provided by
gen. et sp. nov.
Malawidopsis ruwaydae gen. et sp. nov.
2002 cypridopsinae n.gen. sp. I. n.sp.: Martens, table 6.
2014 Cypridopsine sp. I: Blome et al., 193, table 4.
2014 Cypridopsine Genus X gen. nov. spec. I sp. nov.: Jacobs, 70–77, figs 8–12.
Etymology. The first author (BJ) dedicates this new species to his first daughter, Ruwayda Ageno Jacobs.
Diagnosis. Cp elongated and sub-rectangular in lateral view, greatest height situated well in front of the middle, dorsal margin straight over more than half the length. In dorsal view, Cp slender and elongated, with slightly rounded lateral edges, greatest width in the middle. Valves smooth, set with dispersed pits. RV largely overlapping LV on all sides, especially anteriorly.
RV with large inner list, running along the anterior, ventral posterior margins, this list not running parallel to the valve margin. LV without inner lists. No significant sexual dimorphism in valve shape and size.
Second Mx1 palp segment in males 4x as long as basal width, 3x in females.
Prehensile palps strongly asymmetrical, with Rpp being the largest. Lpp with elongated first segment, with two sensory organs implanted well away from the apex; second segment, curved, but with short distal part and with distal margin almost straight. Rpp with first segment less elongated, and with pointed sensory organ also situated away from the apex; second segment very large, stout and elongated. Hp with ms slightly asymmetrically produced towards the ventral side; ls a strongly protruding, asymmetrically triangular and ventrally acutely pointed lobe.
Measurements (all in µm. See Table 3 View TABLE 3 for all specimens measured with SEM)
Holotype male (INV.159019) RV: L = 510, H = 256. LV: L = 479, H = 253.
Allotype female (INV.159011) RV: L = 513, H = 271. LV: L = 494, H = 256.
Type material. Holotype: Male (nr INV.159019), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.
Allotype. Female (nr INV.159020), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.
Paratypes from the type locality. Four males dissected and stored the same way as the holotype ( INV.159021, 159023, 159026, 159028) and seven females, four dissected and stored the same way as the holotype ( INV.159022, 159024, 159025, 159027) and three stored as carapaces in micropalaeontological slides after use for SEM ( INV.159029–159031) .
Other material investigated. Lake Malawi, Mbamba Bay, Malawi, 11°20’42.6”S 34°49’37.7”E, sample LM/99/II/02 collected by KM on 23.3.199 9 by dredge at 4–8 m on fine sand and at 7–10m on coarse sand, and by PONAR grab at 100 m on compact mud GoogleMaps .
Lake Malawi, Metangula, Mozambique, sample LM/99/I/02, collected by KM on 31.3.199 9 by PONAR grab at 31 m on compact sand (12°38’31.9”S 34°46’41.3”E) GoogleMaps and sample LM/99/I/03 collected by KM on 23.3.199 9 by PONAR at 103 m on fine compact sand (12°38’19.1”S 34°46’24.8”E) GoogleMaps
Description of male. Cp in lateral view elongated and sub-rectangular ( Fig. 8E View FIGURE 8 ), anterior side rounded and produced towards the ventral side; posterior margin widely rounded, greatest height situated well in front of the middle; dorsal margin straight over more than half its length, that part weakly sloping towards the posterior side; RV strongly overlapping LV on all sides, especially anteriorly. External valve ornamentation set with spaced pits and isolated stiff setae.
Cp in dorsal and ventral views ( Figs. 8G–J View FIGURE 8 of female) slender and elongated, with slightly rounded lateral margins, greatest width in the middle. In both valves ( Figs. 8A, B View FIGURE 8 ) as from greatest height, dorsal margin sloping in a straight line towards the caudal side; ventral margin slightly curved in the middle; anterior and posterior calcified inner lamella broad, anterior one more so. Central muscle scars ( Fig. 8F View FIGURE 8 ) slightly deviating from the typical cypridopsine pattern, with five central scars, anterior one single, three scars in the middle row, posterior scar subdivided in two; two anterior mandibular scars large.
LV ( Fig. 8A View FIGURE 8 ) without inner lists; but with a submarginal anterior and posteroventral selvage.
RV ( Fig. 8B View FIGURE 8 ) with large anterior, ventral and posterior inner list, situated well away from the valve margin and not running parallel to it; selvage submarginal along part of anterior margin.
A1 ( Fig. 9A View FIGURE 9 ) as typical of the subfamily: uniramous and consisting of seven segments. First segment large and stout, with two ventro-apical setae of unequal length and one shorter dorsal seta (not drawn here, missing in this specimen). Second segment smaller, subquadrate, and with one apical seta on the dorsal side; Rome organ inconspicuous. Third segment with one long (dorsal) and one short (medial) apical setae. Fourth segment with two short setae and two long natatory apical setae. Fifth segment with one short and three long natatory setae. Sixth segment with four long natatory setae. Seventh segment with three long natatory setae and a shorter seta, about one third the length of the natatory setae, apical aesthetasc Ya missing.
A2 ( Figs. 9D, E View FIGURE 9 ) as typical of the subfamily, with one two-segmented protopodite, a reduced exopodite and a large three-segmented endopodite. Protopodite with 2+1 ventral setae. Exopodite with two small and one long setae. First segment of endopodite large, with one medio-ventral aesthetasc Y, large, with swollen distal part and almost reaching tip of segment, one ventro-apical seta and five long natatory setae, reaching beyond tips of end claws, and one shorter (dorsal) accompanying seta. Second segment with two medio-dorsal setae and two medio-ventral t-setae; distally with large claws G1, G2 and z1, short setae z2 and z3; and long seta G3, the latter reaching as far as claw GM. Terminal (third) segment with long and stout claw GM, claw Gm reduced to a seta and the aesthetasc y3 with its accompanying seta fused at its base, this seta slightly longer than the aesthetasc; seta g absent.
MdCox ( Fig. 9B View FIGURE 9 ) slender and of normal anatomy. Md-palp ( Fig. 9C View FIGURE 9 ) four segmented. First segment ventrally with two plumose setae s1 and s2, a long and smooth accompanying seta and a minuscule alpha-seta. Second segment dorsally with two setae (one long and one shorter) and ventrally with a bundle of two long and smooth setae, one shorter and hirsute seta and a slender and hirsute beta-seta, c half the length of the accompanying hirsute seta. Third segment with four long medio-dorsal setae, all smooth, medio-apically with four setae, two long and smooth in the middle, one ventral seta shorter but also smooth, medio-dorsal gamma seta stout and hirsute; ventro-apically with one long and one short setae, both smooth. Terminal (fourth) segment apically with three claws and two setae.
Mx1 with three endites, a two-segmented palp ( Fig. 10C View FIGURE 10 ) and a respiratory plate (not shown). First endite with two small basal bristles and c 8 short apical setae (exact number uncertain). Second endite with c 6 subequal apical setae. Third endite with two large tooth-bristles, set with small teeth, and four further setae; laterally with one hirsute seta, the latter unusually long (reaching beyond tips of apical claws). Palp two-segmented, first segment long and dorso-apically with four long and slender setae, one shorter subapical seta; second segment cylindrical and elongated, more than three times as long as basal width, apically set with six setae, three of these slightly claw-like.
T1 with endopodites as prehensile palps. Lpp ( Fig. 10E View FIGURE 10 ) the smallest, with elongated first segment with two ventral sensory organs inserted above the middle of the segment; second segment hook-like, with short distal part, distal margin almost straight. Rpp ( Fig. 10F View FIGURE 10 ) with broader and shorter first segment, with ventral sensory organ spine-like, inserted well away from the apex; second segment broader and stout, with broad distal part nearly straight. Protopodite ( Fig. 10D View FIGURE 10 ) elongated, with two proximal setae (b and one additional seta, or the two alpha-setae) and c 8 apical plumose and one shorter smooth setae (exact number uncertain).
T2 (walking leg— Fig. 10B View FIGURE 10 ) with seta d1 missing, and medium length seta d2 on knee-segment. Segments and end claws stout and robust, as typical of the subfamily, with penultimate segment divided.
T3 (cleaning leg— Fig. 10A View FIGURE 10 ) with three setae on the basal segment; one ventro-apical seta in the second segment; third and fourth segment fused with an apical pincer, this segment with one medio-ventral seta f as usual, and with an additional medio-dorsal seta F.
CR, as usual for cypridopsines, missing in the male.
Rake-like organ (not shown) apically with 7–8 teeth.
Hp ( Fig. 10G View FIGURE 10 ) with lobe ms slightly asymmetrically produced towards the ventral side; lobe ls a strongly protruding, asymmetrically triangular and ventrally strongly pointed lobe; bursa copulatrix strong and distally with a bifurcated appearance.
Zenker organ stout and solid, with c 13 spinose whorls.
Description of female. Valves ( Figs. 8C, D, G–J View FIGURE 8 ) as in the male.
A2 ( Figs. 11D, E View FIGURE 11 ) with usual sexual dimorphism in apical chaetotaxy: penultimate segment with three large claws (G1–3, G2 the largest) and three long subapical z-setae (z1–3) and a ventro-apical aesthetasc y2. Terminal segment with large claw GM, small claw Gm and aesthetasc y3 fused at its base with its accompanying seta; seta g missing. Penultimate segment also with two medio-ventral t-setae.
Mx1 ( Fig. 12C View FIGURE 12 ) with second palp segment c 3 times as long as basal width.
T1 ( Fig. 12D View FIGURE 12 ) with endopodite palp short, set with three setae, one long, one short and 11 of intermediate length, the shortest not hirsute. Protopodite elongated, with one proximal seta (b) and c 6 apical plumose and three shorter smooth setae (exact number uncertain).
CR ( Figs. 12E, F View FIGURE 12 ) with elongated base and with parallel sides, length c 4x basal width; apical seta long, c 2.5–3 times length of base; lateral seta short.
Differential diagnosis. This species can be distinguished from its congeners, including the as yet undescribed ones, by the sub-rectangular shape of the valves and the smooth valve surface which is set with spaced pits and isolated stiff setae. From the other two species of which the soft parts are here described, the present species can be distinguished by very pointed shape of the ls of the Hp and by the morphology of both prehensile palps, especially the large and robust second segment of the Rpp.
Inverness Museum and Art Gallery
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