Daphnia (Ctenodaphnia) chevreuxi Richard, 1896

Kotov, Alexey A., Garibian, Petr G., Neretina, Anna N. & Marrone, Federico, 2022, A redescription of the Mediterranean endemic cladoceran Daphnia chevreuxi Richard, 1896 (Cladocera: Daphniidae), Zootaxa 5125 (2), pp. 205-228 : 207-221

publication ID	https://doi.org/ 10.11646/zootaxa.5125.2.6
publication LSID	lsid:zoobank.org:pub:D17504C7-0C95-41D6-A1B3-22591D98E497
DOI	https://doi.org/10.5281/zenodo.6425547
persistent identifier	https://treatment.plazi.org/id/03E74374-FA4E-FFF0-FF72-FEDC581CF835
treatment provided by	Plazi
scientific name	Daphnia (Ctenodaphnia) chevreuxi Richard, 1896
status

Treatment

Daphnia (Ctenodaphnia) chevreuxi Richard, 1896 View in CoL

( Figs. 1–14 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14 )

Daphnia chevreuxi Richard, 1896 View in CoL : P. 206–209, Pl. 20, Figs. 10–11 View FIGURE 10 View FIGURE 11 ; Pl. 21, Fig. 4 View FIGURE 4 ; Pl. 23, Fig. 18; Pl. 24, Fig. 4 View FIGURE 4 . Gauthier, 1928: P. 44–45, Fig. 15A–H. Petkovski, 1970: P. 139–142, Figs. 1–7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 . Flössner, 1980: P. 65–67, Fig. 3 View FIGURE 3 . Negrea, 1983: P. 104. Margaritora, 1983: P. 58–62, Fig. 37. Margaritora, 1985: P. 116–119, Figs. 49A–H. Glagolev and Alonso, 1990: P. 159–162. Glagolev, 1995: P. 53, Pl. 41, Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 . Benzie, 2005: P. 125–128, Figs. 343–352. Kotov et al. 2010: P. 201, Fig. 117: 5–9. Korovchinsky et al., 2021: P. 138–140, Fig. 41: 10–14.

Daphnia psittacea Baird, 1850 View in CoL in Stephanides 1948: P. 7–8, Pl. 9, Fig. 9–13 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 View FIGURE 13 .

? Daphnia byzantina Muckle, 1951 : P. 373–374, Fig. 2a–g View FIGURE 2 .

Type locality. « Algérie: Environs de Bòne (Guerrah El M’Krada, bord du lac Fetzara, marais des Kharézas, et abreuvoirs des environs de Bòne)» ( Richard 1896).

Type material. Syntypes. Many parthenogenetic, ephippial females and males in samples DGF 730 and DGF 767, “ Environs de Bòne , Abreuvoir”; DGF 779, “ Environs de Bòne. Dans une abreuvoir”, DGF 783; “ Environs de Bòne ”; DGF 761, “Guerrah el M’Krada. Eau legerement salee”; DGF 797 “Au bord du Guerrah el M’Krada”, all from Algeria .

Other material studied here. Italy: Sicily. Many males, ephippial and parthenogenetic females from a swamp (37.85847°N, 12.92082°E), Margio di Gallitello (Calatafimi), coll. by F. Marrone in 02.03.2014, AAK M-5314. Parthenogenetic females from the GoogleMaps same locality, coll. by Marrone in 30.11.2018, AAK M-6906. Many males, ephippial and parthenogenetic females from a pond (37.87225°N, 14.67638°E), Stagno di C. da Buffali (Nebrodi, Cesarò), coll. by F. Marrone in 16.05.2018, AAK M-6932. GoogleMaps Many males, ephippial and parthenogenetic females from the same locality, coll. by F. Marrone on 19.05.2021, AAK M-6941. GoogleMaps Few juvenile females from Gorgo di Gaetanello (37.88559°N, 13.36919°E), coll. by F. Marrone in 08.03.2009, AAK M-5317. GoogleMaps Parthenogenetic females from a pond (37.97351°N, 13.4936°E), Pozze di Bosco Tumminia (Bolognetta), coll. by F. Marrone in 09.11.2018, AAK M-6938. GoogleMaps Many males, ephippial and parthenogenetic females from a pond (38.02833°N, 13.32666°E), Gorgo di Rebuttone (Altofonte), coll. by F. Marrone in 19.02.2021, AAK M-6943. GoogleMaps Parthenogenetic females from a pond (38.10313°N, 12.67736°E), Gorgo di Baglio Cofano (Monte Cofano), coll. by F. Marrone in 19.12.2019, AAK M-6928. GoogleMaps Parthenogenetic females from the same locality, coll. by F. Marrone in 11.12.2019, AAK M-6946 GoogleMaps . North Macedonia. Many males, ephippial and parthenogenetic females from Slavej (41.3°N, 21.4°E) coll. by T. Petkovski in 25.05.1985, GLAG040 GoogleMaps .

Diagnosis. Adult parthenogenetic female with body high for the subgenus (body height/length without shell spine = 0.56–0.62). Head shield with projected, angled-rounded fornices, a median anterior projection of carapace especially short for the subgenus, it penetrates only to about 1/5–1/6 of length of the head shield. Postabdomen obviously tapering distally. Numerous small anal teeth of subequal size located on anal portion, this row continues more laterally on preanal portion where it is accompanied by groups of smaller spinules. The first (proximal) and second pectens on outer face of postabdominal claw consisting of relatively strong teeth (the longest ones approximately as long as claw diameter); the third pecten consisting of somewhat shorter spines. Antenna I as a minute conical tubercle with nine terminal aesthetascs; tips of aesthetascs not projected beyond tip of rostrum. Limb I with accessory seta; outer distal lobe bearing a long seta distally armed with short setules, and a short second seta; inner distal lobe with a single, long anterior seta 1 armed distally with short setules. Limb II with inner-distal lobe bearing a thin, stiff anterior seta with length 3/4 of soft seta length, armed with minute setules distally. Limb V with exopod supplied with two distal setae and a large lateral seta.

Ephippium dark brown, elongated, bean-like; two eggs with axes located at a very acute angle or almost parallel to the dorsal margin; anterior processes present, postero-dorsal portion of valves (with shell spine) initially incorporated into ephippium. Sculpture of ephippium as a network of small protuberances having smooth tips oriented somewhat posteriorly.

Adult male with head having anteriormost extremity completely occupied with a very large optic vesicle; a shallow post-ocular depression present. Abdomen with a shallow mound on basal segment, other segments without projections. Postabdomen tapering distally, its distal portion bent, ventral margin convex; gonopore opens subdistally, any genital papilla absent. Few anal teeth present only in basal portion of anal margin. Antenna I long, somewhat bent; length of flagellum less than half body antenna I length; distal segment of flagellum covered with short setules. Limb I with inner distal lobe bearing a single long seta (1) and a rudimentary seta 1’. Limb II inner distal portion with seta 1 remarkably stronger as in female, slightly bent and asymmetrically setulated, with a blunt tip. Limb V as in female.

Size of parthenogenetic females 0.9–3.8 mm, adult males 1.1–2.4 mm.

Redescription. Adult parthenogenetic female. General. Body almost transparent, high for the subgenus (body height/length without shell spine = 0.56–0.62), subovoid in lateral view, with maximum height in middle of valves ( Figs. 1A View FIGURE 1 , 2A–B View FIGURE 2 , 3A–B View FIGURE 3 ). Dorsal margin slightly convex. Postero-dorsal angle with a moderately developed to long caudal spine projected posteriorly and somewhat dorsally ( Figs. 1A View FIGURE 1 , 2A–B View FIGURE 2 , 3A–B View FIGURE 3 , 4A View FIGURE 4 ), ventral margin regularly convex.

Head with a short, rounded rostrum ( Figs. 1B View FIGURE 1 , 2C–D View FIGURE 2 , 3C–D View FIGURE 3 ); posterior margin of head slightly concave, without a projection, pre-rostral fold not expressed; antero-ventral margin usually almost straight, but rarely slightly concave; maximum body anterior extremity lies somewhat dorsally to body longitudinal midline. Head without any pre-ocular and post-ocular depressions, a very shallow depression present in posterior head portion, but this is not a border between head and valves. Any helmet fully absent in the adults. Compound eye relatively small, ocellus minute. Head shield with projected, angled-rounded fornices; the median anterior projection of carapace especially short for the subgenus since it penetrates only to about 1/5–1/6 of length of the head shield ( Fig. 2E–F View FIGURE 2 ). Labrum as a fleshy lobe with a large distal plate ( Fig. 5A View FIGURE 5 ).

Carapace in general semi-ovoid, the free edge uniformly convex. A group of relatively long setae in middle of its ventral margin ( Fig. 4A–C View FIGURE 4 ); short setae at postero-ventral and posterior margin, with setules between them ( Fig. 4D–F View FIGURE 4 ).

Abdomen with the first (proximalmost) abdominal segment with a relatively short (but longer than postabdominal claw) process, slightly bent anteriorly; the second segment with a long process (also longer than postabdominal claw) bent posteriorly; the third segment with a massive process; the fourth process small. All processes covered by rows of minute setules ( Figs. 1C–D View FIGURE 1 , 4G–I View FIGURE 4 ).

Postabdomen elongated, obviously tapering distally. Postanal margin straight, preanal and postanal angle smooth. Numerous small anal teeth of subequal size located on anal portion, this row continues more laterally on preanal portion where it is accompanied by groups of smaller spinules ( Figs. 1C, E View FIGURE 1 , 4 View FIGURE 4 G-H). Postabdominal seta as long as preanal margin, its distal segment somewhat shorter than proximal segment. Postabdominal claw regularly bent, with a pointed tip. On its outer side, along the dorsal margin there are three pectens: the first (proximal) and second pectens consisting of relatively strong teeth, the longest ones about as long as the diameter of the claw base; the third pecten consisting of somewhat shorter spines, not reaching tip of claw ( Figs 1E View FIGURE 1 , 4J View FIGURE 4 ).

Antenna I as a minute conical tubercle with nine terminal aesthetascs; tips of aesthetascs not projected beyond tip of rostrum; antennular sensory setae small, arising from base of mound of antenna I and projecting beyond the mound ( Fig. 5A–B View FIGURE 5 ).

Antenna II relatively long ( Fig. 5C–D View FIGURE 5 ); coxal portion with two short setae ( Fig. 5 View FIGURE 5 E-F); basal segment distally with a short anterior spine ( Fig. 5D View FIGURE 5 : arrow) and a longer posterior seta ( Fig. 5G View FIGURE 5 : arrow). A spine on second exopod segment short ( Fig. 5D View FIGURE 5 : arrow). Antennal formula: setae 1–1–3/0–0–1–3. Length of apical setae approximately equal to the length of the branches.

Maxilla I as a projection bearing three longer and a single shorter seta ( Fig. 6A View FIGURE 6 ).

Limb I with accessory seta ( Fig. 6C View FIGURE 6 : acs). Outer distal lobe ( Figs 1F View FIGURE 1 , 6B–D View FIGURE 6 : odl) cylindrical, with a long seta distally armed with short setules, and a short second seta. Endite 5 = inner distal lobe ( Fig. 6C View FIGURE 6 : idl) with a single, long anterior seta 1 armed distally with short setules. Endite 4 with a long anterior seta ( Fig. 6C View FIGURE 6 : 2) and two posterior setae (a–b). Endite 3 with a long anterior seta ( Fig. 6C View FIGURE 6 : 3) and two posterior setae (c–d). Endite 2 with a relatively short anterior seta ( Fig. 6C View FIGURE 6 : 4) and four posterior setae (e–h). Endite 1 = gnathobase fully absent. Two ejector hooks of different length ( Fig. 6C View FIGURE 6 : ejh).

Limb II with exopodite as an elongated lobe ( Fig. 6E View FIGURE 6 : ext) bearing a soft distal seta, and a large, soft, lateral seta of same size with the former. Inner-distal lobe bearing five setae: four posterior setae ( Fig. 6E View FIGURE 6 : a–d) and a thin, stiff anterior seta (1) with length 3/4 of soft seta length, armed with minute setulae distally. Gnathobase ( Fig. 1G View FIGURE 1 ) with two rows of setae: four anterior setae ( Fig. 6F View FIGURE 6 : 1’–4’), and numerous posterior setae of gnathobasic filter plate.

Limb III with a large, setulated pre-epipodite ( Fig. 7A View FIGURE 7 : pep), ovoid epipodite (epp) and a flat exopodite (ext) bearing four distal setae ( Fig. 7A View FIGURE 7 : 1–4), among them seta 2 longest, distally with short setules ( Fig. 7B View FIGURE 7 ), and two lateral setae ( Fig. 7A View FIGURE 7 : 5–6). Inner-distal portion of limb with endite 5 bearing a single, large anterior seta ( Fig. 7C View FIGURE 7 : 1), armed distally with short setulae and a large posterior seta, bearing long setulae ( Fig. 7C View FIGURE 7 : a); endite 4 with a single setulated anterior seta (2) and a single setulated posterior seta (b) somewhat shorter than anterior seta; endite 3 with a large anterior seta ( Fig. 7C View FIGURE 7 : 3) and two posterior setae; endite 2 with a large anterior seta ( Fig. 7C View FIGURE 7 : 4) and four posterior setae. The rest of the limb inner-distal portion as a singular large lobe, modified gnathobase, bearing numerous posterior soft setae, an anterior seta in its distal corner ( Fig. 7C View FIGURE 7 : 1’) and two very short setae in middle of filter plate ( Fig. 7D View FIGURE 7 : 2’ and 3’).

Limb IV with a large, setulated pre-epipodite (pep), ovoid epipodite (epp) and a wide, flat exopodite (ext), bearing four distal ( Fig. 7E View FIGURE 7 : 1–4) and two lateral ( Fig. 7E View FIGURE 7 : 5–6) setae. Inner-distal portion of this limb with completely fused endites, distally with two setae of unclear homology ( Fig. 7F View FIGURE 7 : 1 and 2); the most part of limb inner margin is a gnathobase filter plate consisting of numerous posterior setae.

Limb V with a large, subovoid epipodite (epp), triangular exopodite (ext) supplied with two distal setae ( Fig. 1H View FIGURE 1 , 7G–H View FIGURE 7 : 1–2), and a large, slightly curved lateral seta (3). Inner limb portion as an ovoid flat lobe, with setulated inner margin and a single, large seta.

Juvenile female. Body more elongated, dorsal margin almost straight, caudal spine longer ( Figs 2G View FIGURE 2 , 3E–F View FIGURE 3 , 8A View FIGURE 8 ). Head relatively large as in adult female, with a rounded rostrum ( Fig. 8B–C View FIGURE 8 ), sometimes with a small pointed helmet ( Figs 2G View FIGURE 2 , 3E View FIGURE 3 ). In instar I, head shield according to Ctenodaphnia - type: median anterior projection from carapace somewhat widened anteriorly, almost touching dorsal organ ( Fig. 8D–E View FIGURE 8 ), instead of Daphnia - type with solely located dorsal organ and absent anterior projection of valves ( Kotov & Boikova 2001).

Ephippial female. Only dorsal carapace portion modified in ephippial female ( Fig. 2C View FIGURE 2 ). Ephippium dark brown, elongated, bean-like ( Figs 2C View FIGURE 2 , 3G View FIGURE 3 ); two eggs with axes located at a very acute angle or almost parallel to dorsal margin; anterior processes present; postero-dorsal portion of valves (with shell spine) initially incorporated into ephippium. Dorsal margin of carapace specially re-enforced ( Fig. 9A–C View FIGURE 9 ). Sculpture of ephippium as a network of small protuberances having smooth tips oriented somewhat posteriorly ( Fig. 9B–D View FIGURE 9 ).

Preephippial female. A female transits from parthenogenesis to gamogenesis after two moults. Preephippial (after first such moult) female has an ephippium forming covers of its carapace. As a result, sculpture of future ephippium partly seen through its covers ( Fig. 10A–F View FIGURE 10 ).

Adult male. General. Body elongated, body height/length (without shell spine) about 0.45–0.5; dorsal margin of valves almost straight, elevated above head; no distinct depression between head and valves; postero-dorsal angle distinct, with a relatively long caudal spine ( Figs. 11A–C View FIGURE 11 , 12A View FIGURE 12 ).

Head with a very short, rounded rostrum; its posterior margin straight; ventral margin straight or slightly concave, anteriormost extremity completely occupied with a very large optic vesicle ( Figs 11D View FIGURE 11 , 12B View FIGURE 12 ); a shallow post-ocular depression present. Compound eye especially large, ocellus minute. A short anterior projection from valves ( Fig. 12D View FIGURE 12 ). Fornices well-developed, their tips smooth ( Figs 11D View FIGURE 11 , 12C–E View FIGURE 12 ).

Valve with anterior margin slightly convex, supplied with exactly marginal, relatively short setae ( Fig. 13A–B View FIGURE 13 ); antero-ventral angle prominent anteriorly, supplied with long setae; whole ventral margin with numerous setae located submarginally on inner face of valve. Postero-ventral portion of valve with marginal denticles and short setae located submarginally on inner face of valve; short setules between these setae ( Fig. 13C–D View FIGURE 13 ).

Abdomen with a shallow mound on basal segment, other segments without projections ( Figs 11E View FIGURE 11 , 14A View FIGURE 14 ).

Postabdomen tapering distally, its distal portion bent ( Figs 11E View FIGURE 11 , 14A View FIGURE 14 ); ventral margin convex; preanal margin straight; anal margin depressed; gonopore opens subdistally ( Fig. 11F View FIGURE 11 , 14B View FIGURE 14 ); genital papilla absent. Few anal teeth present only in basal portion of anal margin ( Figs. 11F View FIGURE 11 , 14B View FIGURE 14 ). On outer side of postabdominal claw, the first and second (proximal) pectens consisting of relatively strong teeth; longest teeth shorter than the diameter of the claw base; third pecten consisting of numerous fine setulae not reaching the tip of claw.

Antenna I long, regularly curved ( Figs 11D View FIGURE 11 , 12B View FIGURE 12 , 13E View FIGURE 13 ). Nine short aesthetascs; antennular sensory seta very short, located distally. Length of flagellum less than half body length of the antenna I. The distal segment of flagellum covered with short setules ( Figs. 11G View FIGURE 11 , 13E View FIGURE 13 ).

Antenna II ( Figs 12A View FIGURE 12 , 13F View FIGURE 13 ) relatively larger as compared to female.

Limb I. Outer distal lobe ( Fig. 14C–E View FIGURE 14 : odl) large, bearing a rudimentary seta, a small hillock and a very large seta. Inner distal lobe (idl) with a bent copulatory hook, a single long seta ( Fig. 14 E View FIGURE 14 : 1) and a rudimentary seta ( Fig. 14 E View FIGURE 14 : 1’). Additional seta on endite 4 ( Fig. 14 D View FIGURE 14 : 2’) anterior seta shorter than in female and supplied with longer setules ( Fig. 14 D View FIGURE 14 : 3) while anterior seta longer than in female ( Fig. 14 D View FIGURE 14 : 4).

Limb II. Distalmost endite with seta 1 remarkably stronger than in female, slightly bent and asymmetrically setulated, with a blunt tip ( Figs 11H View FIGURE 11 : arrows, 14F: 1). Limb V as in female ( Fig. 14G View FIGURE 14 ).

Juvenile male II. Body elongated, eye capsule less developed as compared to adult male, posterior incision more protected anteriorly, fornices small; no setules at antero-ventral valve portion, antenna I shorter that in adult male, with shorter flagellum ( Fig. 12F–G View FIGURE 12 ).

Size. Parthenogenetic females 0.9–3.8 mm in our material (2.4–3.8 mm according to Benzie, 2005); adult males 1.1–2.4 mm in our material (1.3–1.6 mm according to Benzie, 2005).

Differential diagnosis. Main characteristic traits of this taxon are (1) strongly reduced (almost undiscernible) body of antenna I and (2) a very short median anterior projection of the carapace (its length less than 0.2 of head shield length) ( Glagolev & Alonso 1990; Glagolev 1995; Benzie 2005; Korovchinsky et al. 2021). Among Eurasian species of the subgenus, only D. (C.) chevreuxi and D. (C.) hispanica have an accessory seta on limb I ( Glagolev & Alonso 1990). Moreover juveniles of D. (C.) chevreuxi sometimes bear a small triangular helmet not characteristic of other Eurasian ctenodaphniids.

D. chevreuxi has no: lateral keels on the head shield as D. (C.) magna ; sharp elongated fornices as D. (C.) lumholtzi; dorsal head plate as D. (C.) atkinsoni -group; sharp dorsal keel as D. (C.) hispanica . The most problematic is differentiation between D. (C.) chevreuxi and D. (C.) similis -group, first of all, the former and D. (C.) similis s.str. which is common in southern half of Europe. Female of D. (C.) chevrexi has: (1) more curved dorsal margin; (2) more reduced (almost undiscernible) body of antenna I; (3) longer seta 1’ on gnathobase III (lengh c.a. 0.5 length of seta 4); (4) two well-developed distal setae on exopodite V (while one of them reduced in size or completely absent in in D. similis group). Male has: (1) strongly reduced postanal teeth, (2) regularly curved antenna I; (3) two welldeveloped distal setae on exopodite V.

Distribution and ecology. We have analysed D. (C.) chevreuxi specimens from Algeria, Sicily and North Macedonia. In North Macedonia, the species was found in former clay pits ( Petkovski 1970), but such populations could have been introduced due to human activities, and their native status is questionable.

The taxon was also recorded from mainland Italy ( Margaritora 1983; Margaritora 1985), mainland Greece ( Stephanides 1948; Marrone et al. 2019b), Romania ( Negrea 1983), Bulgaria ( Flössner 1980; Naidenow 1994), Corfu ( Stephanides 1948), Corsica and Sardinia ( Margaritora 1985; Margaritora et al. 1975), Crete ( Marrone et al. 2019b), and the Maghreb (Dumont 1979; Mouelhi et al. 2000), but no samples from these regions have been analysed in the frame of present work. This species is also reported from Israel, although the actual conspecificity of Israeli populations with D. chevreuxi s.str. should be investigated with molecular tools ( Adamowicz et al. 2009). In reality, the taxon could be represented by a series of close species as it is demonstrated for some other Mediterranean endemics (e.g. Marrone et al. 2010).

Actual occurrence of the species in Morocco ( Mouelhi et al. 2000; Ramdani 1988) and Romania ( Negrea 1983) needs to be verified. D. chevreuxi is considered a “circum-Mediterranean” taxon ( Benzie 2005), but its verified distribution ranges from the Maghreb through Italian Peninsula and Tyrrhenian islands to the Balkans, whereas it is absent from Iberian Peninsula ( Alonso 1996), France ( Amoros 1984), Libya, Egypt (Dumont 1979) and Turkey ( Güher 2014). Moreover D. byzantina Muckle, 1951 described from Turkey ( Muckle 1951) is most probably a junior synonym of D. chevreuxi , or a member of the chevreuxi group possibly conspecific with the aforementioned taxon from Israel.

The species is linked with long-lasting and poorly mineralized temporary ponds, located from the sea level up to 1500 m.a.s.l. ( Gauthier 1928; Stephanides 1948; Margaritora 1985; Ghaouaci et al. 2018; Marrone & Vecchioni 2021), in areas characterized by a typical Mediterranean climate ( Peel et al. 2007).