Malawidopsis antoniae gen. et sp. nov.

(Figs. 13–17, 18Q)

urn:lsid:zoobank.org:act: 689D5146-064F-4818-9665-64B321BB21A0

2002 cypridopsinae n.gen. sp. Q. n.sp.: Martens, table 6.

2014 Cypridopsine sp. Q: Blome et al., 193, table 4.

2014 Cypridopsine Genus X gen. nov. spec. Q sp. nov.: Jacobs, 78–86, figs 13–17.

Etymology. The first author (BJ) dedicates this new species to his second daughter, Antonia Amara Jacobs.

Diagnosis. Cp elongated 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 situated slightly in front of the middle. Valves externally strongly reticulated. RV overlapping LV on all sides, especially anteriorly and postero-ventrally.

RV with large inner list, running along the anterior, ventral and posterior margin, this list running more or less parallel to the anterior valve margin, but not to the posterior 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 asymmetrical, with Rpp being largest. Lpp with elongated first segment, with two sensory organs implanted close to the apex; second segment, with elongated distal part, only slightly curved. Rpp with first segment more broad, and with large and pointed sensory organ situated away from the apex; second segment very large, stout and elongated. Hemipenis with ms asymmetrically produced towards the ventral side; ls a strongly protruding lobe, with an expanded and rounded distal part.

Measurements (all in µm. See Table 3 for all specimens measured with SEM)

Holotype male (INV.159032) RV: L = 558, H = 317. LV: L = 530, H = 311.

Allotype female (INV.159033) RV: L = 554, H = 307. LV: L = 526, H = 310.

Type locality (see Table 1 for further information)

Lake Malawi, Domira Bay, Malawi, 13°26’18,4”S 34°22’31,8”E, collected by KM on 25.3.199 9 by PONAR grab at 10 m on coarse sand .

Type material. Holotype: Male (INV.159032), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.

Allotype. Female (INV.159033), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.

Paratypes from the type locality. Eight males dissected and stored the same way as the holotype (INV.159034, 159036–159038, 159041, 159043, 159044, 159054) and 16 females, 13 dissected and stored the same way as the holotype (INV.159035, 159039, 159040, 159042, 159045–159053) and three stored as carapaces in micropalaeontological slides after use for SEM (INV.159055–159057) .

Other material investigated. The species was also found in the following other stations in Lake Malawi:

• 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 .

• Lake Malawi, South East Arm, Malawi, 14°18’23.7”S 35°9’8.9”E, sample LM/99/IV/02 collected by KM on 26.3.199 9 by PONAR grab, at 10 m depth on coarse sand .

Description of male. Cp elongated in lateral view (Fig. 13E), anterior side rounded and produced towards the ventral side; posterior margin widely rounded, almost straight, greatest height situated well in front of the middle; dorsal margin straight over more than half its length, weakly sloping towards the posterior side; RV overlapping LV on all sides, especially anteriorly. External valve ornamentation consisting of a strong network of reticulation (Fig. 13I).

Cp in dorsal and ventral views (Figs. 13G, H of female) slender and elongated, with slightly rounded lateral margins, greatest width slightly in front of the middle.

In both valves (Figs. 13A, B) 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. 13F) slightly deviating from the typical cypridopsine pattern: five central scars, four scars in a vertical anterior row, posterior scar subdivided in two; two anterior mandibular scars large.

LV (Fig. 13A) without inner lists; but with a submarginal anterior and posteroventral selvage. RV (Fig. 13B) with large anterior, ventral and posterior inner list, situated well away from the valve margin, this list running parallel to the anterior valve margin, but not to the posterior one; selvage submarginal along part of anterior margin.

A1 (Fig. 14A) as typical of the subfamily: uniramous and consisting of seven segments. First segment relatively small, compared to the preceding species, with two ventro-apical setae of unequal length and one shorter dorsal seta. 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. 14B, C) 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 slightly swollen distal part and not 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, shortest of all three species described here. Second segment with two medio-dorsal and two medio-ventral setae; distally with large claws G1, G2 and z1, short setae z2 and z3; and long seta G3, the latter reaching beyond 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. 14D) slender and of normal anatomy. Md-palp (Fig. 14E) 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 three setae (two long smooth and one shorter hirsute) 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 and hirsute, medio-dorsal gamma seta stout and hirsute; ventroapically with one long and one short setae, both smooth. Terminal (fourth) segment apically with three claws and two setae.

Mx1 (Fig. 15C) with three endites, a two-segmented palp and a respiratory plate (Fig. 15D). First endite with two 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 dorsoapically with four long and smooth setae, and one small subapical seta; second segment cylindrical and elongated, more than four times as long as basal width, apically set with six setae, three slightly claw-like.

T1 with endopodites as prehensile palps. Lpp (Fig. 15E) the smallest, with elongated first segment with two ventral sensory organs inserted above the middle of the segment; second segment hook-like, with long distal part, distal margin of this segment almost straight. Rpp (Fig. 15F) with broader first segment, with ventral sensory organ very long, spine-like, inserted well away from the apex; second segment broader and stout, with broad distal part tapering towards the apex. Protopodite (Fig. 15G) elongated, c 8 long and one short apical setae (exact number uncertain).

T2 (walking leg— Fig. 15B) 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. 15A) with three setae on the basal segment; one ventro-apical seta on 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, absent in the male.

Rake-like organ (not shown) apically with 7–8 teeth.

Hp (Fig. 15H) with lobe ms asymmetrically produced towards the ventral side, distally broadly rounded; lobe ls a strongly protruding lobe, with an expanded and rounded distal part; bursa copulatrix strong and with bifurcated appearance.

Zenker organ stout and solid, with c 14 spinose whorls.

Description of female. Valves (Figs. 13C, D, G, H) as in the male.

Most soft parts as in the male, without sexual dimorphism: A1 (Fig. 16A), Md (Figs. 16B, C), T2 (Fig. 17A), T3 (Fig. 17B).

A2 (Figs. 16D, E) 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 an 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 present and shorter than accompanying seta of y3. Penultimate segment also with two medio-ventral t-setae.

Mx1 (Fig. 17C) with second palp segment c 3 times as long as basal width.

T1 (Fig. 17D) with endopodite palp short, set with three setae, two long, one short, all three hirsute. Protopodite elongated, with one proximal seta (b) and c 7 apical plumose and two shorter smooth setae (exact number uncertain).

CR (Figs. 17E, F) 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 shape of the valves and the very reticulated external ornamentation. From the other two species of which the soft parts are here described, the present species can be distinguished by the distally expanded and rounded shape of the ls of the hemipenis and by the morphology of both prehensile palps.