Coronatella (Ephemeralona) striolata ( Sars, 1916 )
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publication ID |
https://doi.org/10.11646/zootaxa.5659.2.7 |
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publication LSID |
lsid:zoobank.org:pub:99BAEEC0-9E90-4ABE-84ED-BEF9D951AD6E |
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persistent identifier |
https://treatment.plazi.org/id/0E6687ED-FFB3-FF82-FF71-FD06135CFEFC |
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treatment provided by |
Plazi |
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scientific name |
Coronatella (Ephemeralona) striolata ( Sars, 1916 ) |
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Coronatella (Ephemeralona) striolata ( Sars, 1916)
( Fig. 1 View FIGURE 1 )
Sars 1916: 333–334, Plate XXXIX, fig. 4, 4a ( Alona ); Smirnov, 2008: 48 ( Alona ).
Type locality. Green Point Common, near Cape Town, Western Cape Province, Republic of South Africa .
Type material. Lectotype. parthenogenetic female on slide GOS F9199 on G.O. Sars collection, labelled “ Alona striolata, Green Point Common , South Africa ” deposited at Zoological Museum of Oslo University.
Paralectotypes. three parthenogenetic females and three ephippial females on the same slide.
Other material studied. 9 parthenogenetic female on slide GOS F 9200 in G.O. Sars collection, labelled “ Alona striolata , Cape of Good Hope”, deposited at Zoological Museum of Oslo University; 2 parthenogenetic females, 9 ephippial females, 5 adult males, 2 juvenile males of instar II, 1 juvenile male of instar 1 on slide GOS F 9189 in G.O. Sars collection, labelled “ Alona elegans , Cape of Good Hope”, deposited at Zoological Museum of Oslo University .
The slides in Canada balsam are rather thick, and it was impossible to use high magnification of optical microscope for examination. Many structures, for example, lateral groups of setulae on postabdomens, remain obscure.
Description. Parthenogenetic female. In lateral view, body ovoid, strongly compressed laterally, low in juveniles ( Fig. 1A View FIGURE 1 ), moderately high in adults ( Fig 1B–C View FIGURE 1 ). Maximum height before the middle of body. Height-length ratio about 0.65 in adults. Dorsal margin evenly convex, postero-dorsal angle weakly defined, postero-ventral angle rounded. Posterior margin almost straight, ventral margin almost straight, antero-ventral angle rounded. Postero-ventral angle without denticles. Carapace at small magnification appears to be covered by densely spaced longitudinal lines ( Fig. 1D View FIGURE 1 ).
Head relatively small, triangular-round in lateral view, rostrum short, pointing downward. Eye very large, two–three times larger than ocellus. Distance from the tip of rostrum to the ocellus greater than that between the ocellus and the eye. Head shield covered by same sculpture as valves. Three connected head pores. Labrum ( Fig. 1E–F View FIGURE 1 ) relatively large, labral keel very wide (height/width ratio about 1.25), with a broadly rounded apex. Anterior margin of keel convex.
Thorax two times longer than abdomen. Dorsal surface of abdominal segments not saddle-shaped. No abdominal projections.
Postabdomen ( Fig. 1G–H View FIGURE 1 ) of moderate length and width, with almost parallel margins in anal portion, strongly narrowing in postanal portion, with broadly rounded distal angle. Length about 2.5 height. Ventral margin convex. Basis of claws bordered from distal margin by clear incision. Distal marginal convex. Dorsal margin with distal part 1.8–2 times longer than preanal one; anal portion longer than postanal. Postanal portion weakly convex to almost straight; anal portion weakly concave. Preanal angle weakly defined, postanal angle not defined. Postanal margin ( Fig. 1H View FIGURE 1 ) with 6–7 clusters of 2–4 elemental marginal denticles, decreasing in size basally. Length of longest elements less than width of postabdominal claw base. Anal margin with 4–5 groups of setulae. Postabdominal claw weakly curved, of moderate length, as long as preanal portion of postabdomen. Basal spine long and thin, about 0.3–0.35 of length of claw.
Antennule narrow elongated, almost reaching tip of rostrum.
Antenna short ( Fig. 1I View FIGURE 1 ). Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basipodite robust, branches short and stout. Basal segments of both branches almost two times longer than middle and apical segments. Seta arising from basal segment of endopodite thin, longer than endopodite. Seta arising from middle segment of endopodite as long as shortest apical setae. Both apical segments with one shorter and two longer setae of similar thickness. Spine on basal segment of exopodite about 2/3 length of middle segment. Spines from apical segments as long as respective apical segments.
Thoracic limbs: five pairs. Morphology of thoracic limbs similar to that of other species of subgenus Ephemeralona .
Limb I with IDL seta 3 as long as ODL seta ( Fig. 1J View FIGURE 1 ); seta 2 slightly shorter than seta 3, seta 1 not observed. Limb III exopodite ( Fig. 1K View FIGURE 1 ) rounded, seta 3 being longest, setae 4, 5 and 6 of about 2/3, 1/2 and 1/4 length of seta 3, respectively (seta 1–2 not observed). Limb IV exopodite ( Fig. 1L View FIGURE 1 ) rounded, with 6 setae, setae 1–3 long, of similar length; seta 4 slightly shorter than seta 3, seta 5 slightly shorter than seta 4; seta 6 two times shorter than seta 5.
Ephippial female ( Fig. 1N–M View FIGURE 1 ) of similar body shape as parthenogenetic female, but with more developed posterodorsal angle of valves, posterior margin of valves straight or weakly concave. Ephippium with egg locules covered by thicker lines than the rest of the valves.
Male. Juvenile males of instar I and II ( Fig. 1O, Q View FIGURE 1 ) and adult male ( Fig. 1S View FIGURE 1 ) have low oval body of similar shape, lower than in female, height/length ratio 0.57. Dorsal margin only weakly curved. Ocellus and eye of same size as in female.
Postabdomen in juvenile males of instar I similar to that of female ( Fig. 1P View FIGURE 1 ), but shorter and higher, sperm duct openings not distinctive, postanal denticles and postabdominal claw of same morphology as in female. In juvenile males of instar II postabdomen ( Fig. 1R View FIGURE 1 ) similar to that of female, but more narrow, sperm duct opening located close to the end of postabdomen, postanal denticles as in female, postabdominal claw shorter than in female, its length less than length of preanal portion of postabdomen. In adult male, postabdomen ( Fig. 1T View FIGURE 1 ) narrow, more strongly narrowing in anal portion, weakly narrowing in postanal portion, with obtuse dorso-distal angle. Ventro-distal angle well-defined, almost straight. Sperm duct openings located ventrally at the end of postabdomen. Postanal angle not defined, preanal angle weakly defined. Distal part of postabdomen 2.2 times longer than preanal. Clusters of short setulae in place of marginal denticles. Postabdominal claw two times shorter than in female, pointed, basal spine long very short.
Thoracic limb I of adult male ( Fig. 1U View FIGURE 1 ) with short U-shaped copulatory hook 1.5 times shorter than limb itself. Copulatory brush present. Ventral face of limb below them with double row of short thick setulae.
Size. In single juvenile female of instar II length was 0.33 mm, height 0.19 mm, in adult parthenogenetic females length 0.38–0.45 mm, height 0.25–0.29 mm. In ephippial females, maximum length 0.46 mm, height 0.31 mm. In single juvenile male of instar I length was 0.26 mm, height 0.16 mm, in single juvenile male of instar II length was 0.28 mm, height 0.18 mm, in two studied adult male, length 0.32 and 0.33 mm, height 0.18 mm in both specimens.
Differential diagnosis: Coronatella (Ephemeralona) striolata shares main diagnostic features of subgenus Ephemeralona (see Sinev 2022b), including sculpturing of the valves as densely spaced lines, seta arising from basal segment of antennal endopodite much longer than endopodite, and setae 2–3 of IDL armed with uniform thin setulae. It clearly differs from all other species of the subgenus in extremely large eye and ocellus in both male and female. C. (E.) striolata have more dense sculpturing of valves than most other species of the subgenus and almost straight posterior margin of valves, characters shared only by C. (E.) vermiculata (see below). C. (E.) striolata also clearly differs from C. (E.) salina , C. (E.) irinae , C. (E.) floessneri (see Alonso1996; Sinev et al. 2009) and C. (E.) vermiculata in long seta 4 of exopodite III (in these species it is 2–3 times shorter than seta 5), and from C. (E.) orellanai (see Alonso 1996) in single row of lateral groups of setulae on postabdomen.
Males of C. (E.) striolata differs from all other species in shape of postabdomen, which is narrow elongated, evenly narrowing distally, with evenly concave anal and postanal portion. Males of most species of the genus have wider postabdomens with parallel margins in anal portion (see Sinev 2022b), similar to that of C. (E.) vermiculata (see below). Asian C. (E). floessneri and C. (E.) irinae (see Sinev et al. 2009) have male postabdomens of somewhat similar to C. (E). striolata shape, but with shorter distal portion, being only 1.5 times longer than preanal portion, stongly narrowing in anal portion, and with postanal margin being parallel to ventral margin.
Distribution. To date this rare species is known only from two locations in Cape peninsula, it is probably an endemic of Cape region of South Africa.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.