Alona martensi, Sinev, Artem Yu, 2009

Sinev, Artem Yu, 2009, Cladocerans of the Alona affinis (Leydig, 1860) group from South Africa, Zootaxa 1990, pp. 41-54 : 42-49

Alona martensi sp. n.

Listed as A. cf. affinis in Sinev, 2008; as Alona sp. n in Smirnov, 2008.

Type location: Republic of South Africa, KwaZulu-Natal province, Giant Castle, The Lakes (29°14'31"S 29°33'2"Е), altitude: 1950 m.a.s.l. 26.03.1995.

Holotype: parthenogenetic female, preserved in 80% ethanol, ZMMU, Ml-51.

Paratypes. Repubic of South Africa, KwaZulu-Natal province: 8 parthenogenetic females, 6 juvenile females of instar II, 2 juvenile females of instar I, from type location, preserved in 80% ethanol, ZMMU, Ml- 52; over 100 females, ephippia and exuvia Lakes Cave Tarn 1, Cobham (29°39'50"S 29°18"47'E), 11.11.1996, NNS 2002-038; over 50 parthenogenetic females from Crane Tarn 5A (small pool), Cobham (29°42'52"S 29°19'26"E), 16.02.1998, NNS 2002-011; over 50 parthenogenetic females from Crane Tarn 3, Cobham (29°42'44"S, 29°19'19"E), 16.02.1998 NNS 2002-010; ephippium and exuvia from Lakes Cave Tarn 3, Cobham, (29°39'50"S, 29°18'47"E), 20.03.1996 NNS 2002-023; 2 parthenogenetic females, numerous exuvia and ephippia from Lakes Cave Tarn 1, Cobham (29°39'50"S 29°18'47"E), 20.03.1996 NNS 2002-021; several exuvia and ephippia from Lakes Cave Tarn 2, Cobham (29°39'50"S 29°18'47"E), 20.03.1996 NNS 2002- 022; 1 parthenogenetic female, numerous exuvia and ephippia from Lakes Cave Tarn 7, Cobham (29°39'53"S 29°18'54"E), 11.11.1996 NNS 2002-043; 12 parthenogenetic females, numerous exuvia and ephippia from The Lakes 2, Giant Castle (29°14'21"S 29°33'2"E) 16.03.1996 NNS 2002-017; over 50 parthenogenetic females from The Lakes 1, Giant Castle (29°14'34"S 29°32'59"E), 26.03.1995 NNS 2002-079; over 50 parthenogenetic females from The Lakes 1, Giant Castle (29°14'34"S 29°32'59"E) 16.03.1996 NNS 2002-015; 1 parthenogenetic female, numerous exuvia and ephippia from The Lakes 3, Giant Castle (29°14'32" S 29°33'1" E), 0 6.11.1996 NNS 2002-030; 4 parthenogenetic females, numerous exuvia and ephippia from Crane Tarn 1, Mzimkhulwana (29° 42'48" S 29°19'26" E), 21.03.1995, NNS 2002-058; numerous exuvia from Crane Tarn 2, Mzimkhulwana, (29°42'45" S, 29°19'19" E), 21.03.1995, NNS 2002-059. Lesotho: parthenogenetic female and head shield from Tarn 2 below Devil's Knuckles, Sehlabathebe, (29°51'23"S 29°7'35"E 15.11.1996), NNS 2002-050; 4 parthenogenetic females, numerous exuvia, Tarn 6, Sehlabathebe, (29°51'43"S, 29°7'24" E), 15.11.1996, NNS 2002-052.

Etymology: the species is named in honour of its collector, Dr. Prof. Koen Martens.

Diagnosis: Female. Among the largest species of Alona , length of adult 0.84-1.17 mm. Body regular oval, of moderate height, moderately compressed laterally. Maximum height in the anterior third of body, length about 1.6 times maximum height. Dorsal margin convex, postero-dorsal and postero-ventral angles broadly rounded. Postero-dorsal angle with 4-5 groups of large setules, with 4-6 setules in each. Ventral margin with 70-90 setae. Head shield with posterior margin ending in acute angle, rostrum short and broadly rounded. Two major head pores with a narrow connection between them. PP about 2.5-3 IP. Minute lateral head pores located 1.5 IP distance from midline, at level of anterior major head pore. Labrum of moderate size, shape of labral keel varies greatly, keel wide, with a blunt apex of variable shape. Anterior margin of keel convex, posterior margin irregular, in some specimens notched, with 1-2 clusters of setae.

Postabdomen of moderate length and width, narrowing distally, length about 2.5 times height. Distal margin from almost straight to weakly convex, distal angle not strongly protruding and rounded. Dorsal margin straight in postanal portion and weakly concave in anal one, with distal part about 2.5 times longer than preanal one, postanal portion 2.6-2.8 times longer than anal one. Preanal angle well expressed, postanal angle not defined. Postanal margin with 15-17 well-developed, single sharp denticle each with 1-6 spinules along anterior margin. Postanal portion with 11-14 broad lateral fascicles, posteriormost setae of each fascicle longest, just reaching beyond base of marginal denticles. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine long and slender, about 0.3-0.45 of the claw length.

Antennule with nine terminal aestetascs and a cluster of 4-6 long setules at anterior face. Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Seta arising from basal segment of endopodite thin, reaching end of endopodite. Spine on basal segment of exopodite 1.5 times shorter than middle segment. Spines on apical segments shorter than apical segments.

Thoracic limb I with accessory seta slightly shorter than ODL seta. IDL with three setae. 1st IDL large, claw-like, strongly curved, longer than 2nd seta, two other setae armed with setules in distal part. Exopodite of limb III with seven setae, seta 3 longest. Exopodite IV with six setae. Exopodite V with four setae. Epipodites IV and V with projections longer than exopodite itself. Limb present VI.

Male unknown.

Differential diagnosis. A. martensi sp. n. is a typical member of the affinis -group of the genus Alona and has all distinctive characters of the group – large size, two major head pores, claw-like first IDL seta, which clearly separates it from all species of Alona not belonging to the affinis -group. It differs from other species in the group by the short spine of the basal segment of exopodite of antenna (in all other species it is equal or longer than middle segment of exopodite, in A. martensi sp. n. it is less than 2/3 the length of the middle segment). A. martensi sp. n. also differs from A. affinis , A. kendallensis and A. ossiani by the postabdomen narrowing distally and a high IP/PP ratio (2.5-3 in A. martensi sp. n., less than 2 in other species). Differences between A. martensi and A. affinis are summarised in Table 1.

Description. Parthenogenetic female. In lateral view, body subrectangular, low in juvenile females ( Fig.1 A, D), oval, of moderate height in adults ( Fig. 1 F), moderately compressed laterally. Maximum height in the anterior third of body. In adults length about 1.6 times maximum height. Dorsal margin convex, postero-dorsal and postero-ventral angles broadly rounded. Posterior margin weakly convex. Postero-dorsal angle with 4-5 groups of large setules, with 4-6 setules in each, length of setules in groups increase posteriorly ( Fig. 2 A-B). A row of 70-90 setules along posterior margin on inner side of carapace, these setules not organized into groups. Ventral margin weakly convex to straight, with 70-90 setae. Antero-ventral angle rounded. Carapace ornamentation weakly developed longitudal lines and dense longitudal striae.

Head relatively small, triangle-round in lateral view. In lateral view rostrum protruding downwards. Ocellus small, eye two times larger than ocellus. Distance from tip of rostrum to ocellus subequal to that between ocellus and eye.

Head shield with maximum width behind mandibular articulation, covered by fine striae. Rostrum short and rounded ( Fig. 1 B, E, G). Posterior margin as prominent, acute distal angle. Two major head pores with a narrow connection between them ( Fig. 1 C, I, H). Anterior pore smaller than posterior one, in juvenile females size of pores larger than in adults. PP about 1 IP in instar I juvenile females, about 1.5 IP in instar II juvenile females, 2.5–3 IP in adults. Lateral head pores located in small depressions about 1.5 IP distance from midline, at level of anterior major head pore. Around head pores striae absent

Labrum of moderate size ( Fig. 2 C–D). Shape of labral keel varies greatly, keel wide, with a blunt apex of varied shape. Anterior margin of keel convex, posterior margin irregular, frequently (in about half of specimens) notched, with 1–2 clusters of setae.

Thorax two times longer than abdomen. Dorsal surface of abdominal segments not saddle-shaped. No abdominal projections.

Postabdomen of moderate length and width, narrowing distally, length about 2.5 height ( Fig. 2 E–F). Ventral margin straight. Basis of claws bordered from distal margin by clear incision. Distal margin from almost straight to weakly convex, distal angle rounded. Dorsal margin straight in postanal portion and weakly concave in anal one, with distal part about 2.5 times longer than preanal one, with postanal portion 2.6–2.8 times longer than anal one. Preanal angle well expressed, postanal angle not defined. Preanal margin almost straight.

Postanal margin with 15–17 well-developed, single sharp denticles, each with 1–6 denticles along anterior margin, size of denticle increasing distally. Length of longest denticles about 1.5 width of base of postabdominal claw, more than 3 times exceding the width of the denticle base.. Anal margin with 3–5 groups of marginal setules. Postanal portion with 11–14 broad lateral fascicles, posteriormost setae of each fascicle longest, not reaching beyond base of marginal denticles. Anal portion with numerous smaller fascicles, spaced irregularly, in several rows. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen ( Fig. 2 G). Basal spine long and slender, about 0.3–0.45 of the claw length.

Antennule ( Fig. 1 J) of moderate size, not reaching the tip of rostrum, with cluster of 4–6 long setules about one third length of antennule at anterior face, and 2 transverse row of very short short setules below it. Antennular seta thin, of about half length of antennule, arising terminally. Nine terminal aestetascs, two of them long and thin, little shorter than antennule itself, other much shorter, about 1/2–1/3 length of antennule. All aesthetascs projecting beyond anterior margin of the head shield.

Antenna relatively short ( Fig. 2 H). Basal segment robust, with short seta between branches, branches relatively short, all segments cylindrical, slender, subequal in length. Seta arising from basal segment of endopodite thin, reaching end of endopodite. Seta arising from middle segment o f endopodite of similar size with apical setae. Spine on basal segment of exopodite significantly shorter than middle segment, less than 2/3 of its length. Spines on apical segments shorter than apical segments.

Mandible of morphology usual for genus. Maxillule ( Fig.1 K) with two setae pointed to its base. Maxilla absent.

Thoracic limbs: six pairs.

Limb I of moderate size ( Fig. 3 A). Epipodite oval, with finger-like projection shorter than epipodite itself. Accessory seta long, only slightly shorter than ODL seta, with long setules in distal part. ODL with one seta. IDL ( Fig. 3 B) with only three setae and several clusters of stiff setules. 1st IDL seta large and broad, claw-like, strongly curved, longer 2nd seta, both 2nd and 3rd IDL setae with an annulus and setules in distal part, 3rd seta slightly shorter than ODL seta, 2nd seta about 2/3 length of 3rd seta. Endite 3 with four setae subequal in length. Endite 2 with two long distally setulated setae, one of them longer than ODL seta, a shorter seta near their base and a naked seta with small sensillum near its base on anterior face of limb ( Fig. 4 A). Endite 1 with two 2-segmented setae, both setulated in distal part, a flat plumose seta pointed the limb base, and a naked seta two times longer than naked seta of endite 2 with small sensillum near its base on anterior face of limb. Sixseven rows of 8–12 thin long setules on ventral face of limb. Two ejector hooks, one 1.5 times shorter than other. Maxillar process elongated, with short setulated in distal part seta ( Fig. 3 C).

Limb II subtriangular ( Fig. 3 D). Exopodite elongated, of irregular shape, setulated distally, with one slen- der seta longer than exopodite itself ( Fig. 4 B). Eight scraping spines or scrapers, three basalmost spines subequal in length, others increasing in length distally. Size of denticles on basal part of spines evenly decreasing from basal to distal spines. Distal armature of gnathobase with four elements, two lateral are minute, pointed, one of the middle elements geniculated, setulated in distal part, other broad, with two rows of denticles. Filter plate II with seven setae, the posteriormost member three times shorter than others.

Limb III: epipodite oval, without finger-like projection ( Fig. 3 E). Exopodite of trapezial shape, with seven setae. Seta 3 longest, setae 6 and 7 subequal in length, about 1/3 length of seta 3, other setae very short. Setae 1–5 plumose, seta 6 with three rows of hard setules in distal part, seta 7 plumose in distal part. Distal endite ( Fig. 4 C) with 3 setae, two distalmost members scraping, slender, sharp, with denticles in distal part, short bottle-shaped sensillum located between their bases; basalmost seta flattened, bilaterally armed with long setules Basal endite with 4 plumose setae increasing in size basally. Four pointed soft setae increasing in size basally, a small bottle-shaped sensillum near the distalmost seta. Distal armature of gnathobase with four elements ( Fig. 4 D). First one an elongated, narrowing distally sensillum, second strongly geniculated seta, third and fourth - spines. Filter plate III with seven setae of equal length.

Limb IV: Pre-epipodite setulated; epipodite oval, with finger-like projection longer than exopodite itself ( Fig. 3 F). Exopodite subquadrangular, with six setae. Seta 1 and 2 being longest, equal in length, seta 3 slightly shorter, bend toward inner portion of limb, seta 4 shortest, about half length of seta 1, strongly bend toward inner portion of limb, setae 5–6 subequal in length, between 1/2 and 2/3 length of seta 1. Setae 1–4 plumose, setae 5–6 with short setules. Inner portion of limb IV with four setae and bottle-shaped sensillum ( Fig. 4 E). Scraping seta slender, with broad denticles inn distal part, three flaming-torch seta decreasing in size basally, with 8–10 long setules each. Small sensillum between the bases of middle and basal flamingtorch setae. Three soft setae slightly increasing in size basally. Gnathobase with one long two-segmented seta, a small hillock distally and a spine near its base. Filter plate IV with five setae.

Limb V: pre-epipodite setulated; epipodite oval, with finger-like projection 1.5 times longer than epipodite itself ( Fig. 3 G). Exopodite divided into two lobes, with four plumose setae, seta 1–3 long, subequal in length, seta 4 three times shorter. Inner limb portion as broad rounded lobe, with setulated inner margin. At inner face, two setae densely setulated in distal part, one of them longer than exopodite setae, other three times shorter. Filter plate V with three seta and with two broad based sensilla-like structures between inner face setae and filter plate. This structure was only once reported for species of affinis -group before ( Alonso, 1996: 344, Fig 154L), but after close examination is also found in both European and South African A. affinis sensu stricto.

Limb VI ( Fig. 3 H) elongated rounded lobe with setulated margin, length/width ratio about 2.5.

Ephippial female unknown. Ephippium yellow-brown, without developed egg locules and prominent sculpture.

Male unknown.

Size: In females of first juvenile instar, length 0.64–0.70 mm, height 0.33–0.38 mm, in females of second juvenile instar, length 0.44–0.50 mm, height 0.74–0.87 mm. In adult female, length 0.84–1.17 mm, height 0.55–0.68 mm.

Distribution and ecology: Kwa-ZuluNatal province of Republic of South Africa and Lesoto, the East Escarpment region of the Drakensberg mountains. All localities in a single quadrant between 28° and 29° S, 28° and 29° E, at altitudes between 1950 and 2400 m. The species inhabits small, possibly temporary water bodies – mountain lakes, pools and tarns. Temperature in water bodies at time of sampling varied from 17º to 24º C, pH from 5.8 to 8,2.

Figures

FIGURE 1. Alona martensi sp. n. from Republic of South Africa, Kwa-Zulu Natal Province, Giant Castle, The Lakes, 29 ° 14 ' 31 " S, 29 ° 33 ' 2 " Е: A – C – juvenile female of instar I: A – lateral view, B – head shield, C – head pores; D – E – juvenile female of instar II: D – lateral view, E – head shield; F – K – parthenogenetic female: F – lateral view, G – head shield, H – I – head pores, J – antennule, K – maxillule. Scale bars: 0.2 mm for A – D, D – G, 0.05 mm for C, H – K.

FIGURE 2. Alona martensi sp. n. from Republic of South Africa, Kwa-Zulu Natal Province, Giant Castle, The Lakes, 29 ° 14 ' 31 " S, 29 ° 33 ' 2 " Е, parthenogenetic female: A – B – posterior margin and posteroventral angle of valves, C – D – labrum, E – F – postabdomen, G – postabdominal claw, H – antenna. Scale bars: 0.1 mm.

FIGURE 3. Alona martensi sp. n. from Republic of South Africa, Kwa-Zulu Natal Province, Giant Castle, The Lakes, 29 ° 14 ' 31 " S, 29 ° 33 ' 2 " Е, parthenogenetic female: A – B – limb I in inner and outer view, C – maxillar process of limb I, D – limb II, E – exopodite of limb III, F – exopodite of limb IV, G – limb V, H – limb VI. Scale bar: 0.1 mm.

FIGURE 4. Alona martensi sp. n. from Republic of South Africa, Kwa-Zulu Natal Province, Giant Castle, The Lakes, 29 ° 14 ' 31 " S, 29 ° 33 ' 2 " Е, parthenogenetic female: A – endites of limb I, B – gnathobase of limb II, C – D – inner portion of limb III, E – inner portion of limb IV. Scale bar: 0.05 mm.