Malawidopsis stellae, 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 : 309-317

publication ID

https://doi.org/10.11646/zootaxa.5100.3.1

publication LSID

lsid:zoobank.org:pub:8D9244AB-C2E5-4F76-8C9B-30A39DD3679B

DOI

https://doi.org/10.5281/zenodo.6314193

persistent identifier

https://treatment.plazi.org/id/07E7DDBB-C06E-4421-8738-F429CF705DFC

taxon LSID

lsid:zoobank.org:act:07E7DDBB-C06E-4421-8738-F429CF705DFC

treatment provided by

Plazi

scientific name

Malawidopsis stellae
status

gen. et sp. nov.

Malawidopsis stellae gen. et sp. nov.

( Figs. 3–7 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 , 18G View FIGURE 18 )

urn:lsid:zoobank.org:act:07E7DDBB-C06E-4421-8738-F429CF705DFC

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

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

2014 Cypridopsine Genus X gen. nov. spec. G sp. nov.: Jacobs, 61–69, figs 3–7

Etymology. The first author (BJ) dedicates this species to his wife, Stella Ayet Okello.

Diagnosis. Cp elongated in lateral view, anterior side more broadly rounded than posterior one, greatest height situated well in front of the middle. In dorsal view, Cp slender and elongated, with slightly rounded lateral edges, greatest width in the middle. Valves smooth, RV overlapping LV on all sides, especially anteriorly.

RV with large anterior inner list, situated well away from the valve margin. LV without lists or selvages. No significant sexual dimorphism in valve shape and size.

Prehensile palps asymmetrical, with Rpp being largest. Lpp with elongated first segment, with sensory organ implanted well away from the apex, and narrow and sickle shaped second segment, bent over c 180°. Rpp with wider first segment, with subapical, long and pointed sensory organ; second segment larger than in Lpp, even curved and broad. Hp with ms asymmetrically produced towards the ventral side; ls strongly protruding and distally dilating into a hammer-like shape.

Measurements (in µm; see Table 3 View TABLE 3 for all specimens measured with SEM)

Holotype male ( INV.159010) RV: L = 579. LV: L = 551, H = 314.

Allotype female ( INV.159011) RV: L = 567, H = 332. LV: L = 546, H = 304.

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

Type material. Holotype. Male ( NV.159010), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.

Allotype. Female ( INV.159011), with soft parts dissected in glycerine in a sealed slide and valves stored dry in a micropalaeontological slide.

Paratypes from the type locality. Five males, all dissected and stored in the same way as the holotype ( INV.159012-1599015, 159068) and four females, one dissected and stored in the same way as the holotype ( INV. 159069) and three stored as carapaces in micropalaeontological slides after use for SEM ( INV.159016-159018) .

Other material investigated. The species is presently known from its type locality, and from the South West Arm of the lake ( Blome et al. 2014) .

Description of male. Cp elongated in lateral view ( Fig. 3E View FIGURE 3 ), anterior side more broadly rounded than posterior one, greatest height situated well in front of the middle; RV overlapping LV on all sides, especially anteriorly and ventrally. External valve surface smooth, set with small pits and few setae. Cp in dorsal and ventral views ( Figs. 3G–I View FIGURE 3 of female) slender and elongated, with slightly rounded lateral margins, greatest width in the middle.

In both valves, 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. Both valves also internally densely set with pore openings ( Figs. 3A–D, F, J View FIGURE 3 ). Central muscle scars ( Fig. 3F View FIGURE 3 ) as typical of Cypridopsinae , with four central scars, three in an anterior row, posterior scar subdivided in two; two anterior mandibular scars large.

LV ( Fig. 3A View FIGURE 3 ) without lists or selvages, only with traces of a submarginal posteroventral selvage. RV ( Fig. 3B View FIGURE 3 ) with large anterior inner list, situated well away from the valve margin, and traces of ventral inner list towards the posterior side.

A1 ( Fig. 4A View FIGURE 4 ) 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. 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. 3D, E View FIGURE 3 ) 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 and 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 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 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. 4B View FIGURE 4 ) slender and of normal anatomy. Md-palp ( Fig. 4C View FIGURE 4 ) 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 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 and hirsute, 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. 5D View FIGURE 5 ) and a respiratory plate (not shown). First endite with two small setae 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 slender setae and one smaller subapical seta (not drawn); second segment cylindrical and elongated, more than three times as long as basal width, apically set with six setae, three of these slightly clawlike.

T1 with endopodites as prehensile palps. Lpp ( Fig. 5F View FIGURE 5 ) the smallest, with elongated first segment with ventral sensory organ inserted distal of the middle of the segment; second segment sickle shaped, bent over c 180°. Rpp ( Fig. 5G View FIGURE 5 ) with broader first segment, with large ventral sensory organ spine-like, subapically inserted; second segment broader and more stout, less curved than in the Lpp. Protopodite ( Fig. 5E View FIGURE 5 ) elongated, with one proximal seta (b) and c 7 apical plumose setae (exact number uncertain).

T2 (walking leg— Fig. 5C View FIGURE 5 ) 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. 5A View FIGURE 5 ) 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 ( Fig. 5B View FIGURE 5 ) apically with 7–8 teeth.

Hp ( Fig. 5H View FIGURE 5 ) with lobe ms asymmetrically produced towards the ventral side; lobe ls prominently produced, with elongated base and expanded hammer-like distal part; bursa copulatrix resembling a flower with three petals. Zenker organ stout and solid, with c 15 spinose whorls.

Description of female. Valves ( Figs. 3C, D View FIGURE 3 ) and Cp ( Figs 3G–I View FIGURE 3 ) as in the male.

Most soft parts as in the male, without sexual dimorphism: A1 ( Fig. 6A View FIGURE 6 ), Md ( Figs. 6B, C View FIGURE 6 ), T2 ( Fig. 7A View FIGURE 7 ), T3 ( Fig. 7B View FIGURE 7 ), rake-like organ ( Fig. 7C View FIGURE 7 ).

A2 ( Figs. 6D, E View FIGURE 6 ) 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 missing. Penultimate segment also with two medio-ventral t-setae.

Mx1 ( Fig. 7D View FIGURE 7 ) with first palp segment showing subapical seta; second palp segment c 4.3 times as long as basal width.

T1 ( Fig. 7E View FIGURE 7 ) with endopodite palp short, set with three setae, two long, one shorter, all three hirsute. Protopodite elongated, with one proximal seta (b) and c 8 apical plumose setae (exact number uncertain).

CR ( Figs. 7F, G View FIGURE 7 ) with elongated base and with parallel sides, length c 4x basal width; apical seta long, c 2.5 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 smooth external valve surface which lacks significant ornamentation. From the other two species of which valves and soft parts are here described, the present species can be distinguished by the hammer-like shape of ls of the Hp and by the morphology of the prehensile palps, especially of the smaller Lpp.

INV

Inverness Museum and Art Gallery

RV

Collection of Leptospira Strains

KM

Kotel'nich Museum

Kingdom

Animalia

Phylum

Arthropoda

Class

Ostracoda

Order

Podocopida

Family

Cyprididae

Genus

Malawidopsis