Ovalona weinecki ( Studer, 1878 ) Damme, Kay Van & Dumont, Henri J., 2008
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publication ID |
https://doi.org/ 10.11646/zootaxa.1960.1.1 |
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persistent identifier |
https://treatment.plazi.org/id/B34587DE-902C-CD76-56F2-F9DAFED8FDF2 |
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treatment provided by |
Felipe |
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scientific name |
Ovalona weinecki ( Studer, 1878 ) |
| status |
comb. nov. |
Ovalona weinecki ( Studer, 1878) View in CoL comb. nov.
Figs 1–2 View FIGURE 1 View FIGURE 2
Alona weinecki Studer, 1878 Alona weinecki Studer, 1878 in Rühe (1914); Frey (1988) non Alona weinecki Dumont & Martens (1996) (See under Distribution) We refer for extensive synonymy lists to Frey (1988) and Pugh et al. (2002; not Alona capensis Rühe, 1914 View in CoL ). Synonymy of Alona bukobensis var. subantarctica Ekman, 1905 View in CoL or Alona subantarctica Ekman, 1905 View in CoL in Sars (1909) and
Frey (1988) is uncertain (See under Remarks). We regard Alona inermis Pesta, 1928 View in CoL here as junior synonym of subantarctica View in CoL (see below).
Type locality. Îles Kerguelen, Sub-Antarctic ( Studer 1878).
Material examined. 60 parthenogenetic females, Heard Island, Antarctica Freshwater Pool, Coll. H.J.G. Dartnall, The Natural History Museum, London, tubes (specimens in ethanol) labeled Chydoridae
1993.62–71; 20 parthenogenetic females, Marion Island, Coll. Marion Island expedition 1965–1966. The Natural History Museum, London, labeled Alona sp. 1969.6.9.566–581 (tubes 2454, 2496).
Redescription of adult parthenogenetic female. Habitus ( Figs 1A–B View FIGURE 1 ). Medium-sized animals, 0.50–0.65mm (specimens from Kerguelen up to 0.8mm in Frey 1988), colourless and transparent. Specimens from Heard Island slightly smaller (0.5–0.6mm) than those from Marion Island (0.55–0.65mm). In lateral view carapace rectangular with arched dorsal margin and low posterodorsal angle ( Fig. 1A–B View FIGURE 1 ). Ventral carapace margin rather concave, with deepest ventral point just before midline ( Fig. 1A View FIGURE 1 ). Posteroventral corner round, without notch ( Fig. 1H View FIGURE 1 ). In dorsal and ventral view, body rather broad. Dorsal keel absent. Head. Ocellus as large as eye ( Fig. 1A View FIGURE 1 ). Head shield not studied. Rostrum blunt and short, aesthetascs projecting beyond its tip ( Fig. 1A View FIGURE 1 ). Three main head pores ( Fig. 1D View FIGURE 1 ) of same size, narrowly connected; small pores closer to main pores than to lateral margin of head shield, at about one IP distance from the midline. Carapace ( Figs 1A–B, 1H View FIGURE 1 ). Ornamentation consisting of parallel, well-developed wide striae, no fine striation; number of lines 20–26 ( Figs 1A– B View FIGURE 1 ). Posterior margin wavy. Marginal setae short and not strongly differentiated into groups. Marginal row of 40–56 setae decreasing in size towards posteroventral corner and followed by small spinules not arranged in groups ( Fig. 1H View FIGURE 1 ), of similar size, with few thicker spines in between. Labrum ( Fig. 1C View FIGURE 1 ). Labral keel in lateral view relatively wide with moderately concave margin and obtuse tip with indentation ( Fig. 1C View FIGURE 1 ). No ventral setules or denticles on labral keel. See also Frey (1988). Mandible relatively strongly developed ( Fig. 1I View FIGURE 1 ), in relation to body size ( Fig. 1A View FIGURE 1 ). Antennules ( Fig. 1E View FIGURE 1 ). About 2.5– three times as long as wide, sensory seta not seen. Fine, long setules on margin. Aesthetascs on third of antennular corm, subequal in length (two little longer). Second antennae ( Fig. 1F View FIGURE 1 ). Coxal setae not studied. Coxal spine large, conical ( Fig. 1F View FIGURE 1 ). Spinal formula 001/101, setal formula 113/003. First exopod seta on antenna long and thick ( Fig. 1G View FIGURE 1 ), reaching beyond last antennal segments; on external side of second exopod segment, group of six to eight fine parallel spinules ( Fig. 1F View FIGURE 1 ). Spine on first endopod segment reaching just beyond second endopod segment; main terminal spines on endo- and exopod well developed, exopod spine just longer than ultimate segment ( Fig. 1F View FIGURE 1 ). Terminal setae subequal in length.
Postabdomen ( Figs 1J–K View FIGURE 1 ). Relatively broad, highest at preanal angle, and with rounded dorso-distal margin. Length about two times as long as high. Ventral margin shorter than anal and postanal margin. Anal and postanal margins of similar length and shorter than preanal margin. Anal margin concave, postanal margin convex and tapering distally, distal margin not protruding. Preanal corner strongly developed, triangular, protruding far beyond postanal margin. Marginal denticles in groups of small denticles, arranged in six to seven postanal groups. In populations from Heard Island, distalmost denticle broader. Distal postanal groups consisting of one broader and larger denticle with smaller adjacent spines, those closer to the anal margin in groups of two to four small spines of which distal largest. Lateral fascicles five groups in postanal portion, consisting of five to ten spinules in each group, parallel to each other, slightly increasing in size distally and with slightly longer distal spinule per group. Three to four clusters of marginal denticles and three rows of fascicles in anal portion. Terminal claw ( Figs 1J–K View FIGURE 1 ). Longer than anal margin, evenly curved, implanted with setules along dorsal side. Well developed basal spine, about two times as long as claw width at base and less than half of claw length. Group of four to five short basal spinules ( Fig. 1K View FIGURE 1 ).
First maxilla ( Fig. 2A View FIGURE 2 ). Well developed, with two large setulated setae.
Five pairs of limbs. First limb ( Figs 2B–F View FIGURE 2 ). Epipodite round without long projection. First endite with two marginal setae, second endite with three setae of which two longer (and unequal in length), third endite with four setae ( Fig. 2B View FIGURE 2 ); anterior elements on en1–2 minute ( Fig. 2C View FIGURE 2 ). ODL with one slender seta little longer than largest IDL seta ( Figs 2D–E View FIGURE 2 ); IDL with three setae; armature of two largest IDL setae fine unilateral setulation in distal half, no strong denticles or spines. Accessory seta present near base ODL, relatively short and plumose. Six to seven anterior setule groups with more than five fine setules in each group, not decreasing in size ventrally. Ejector hooks relatively long, of similar size and gnathobase ( Fig. 2F View FIGURE 2 ) elongated with setulated apex. Second limb ( Figs 2G–J View FIGURE 2 ). Exopodite ( Fig. 2H View FIGURE 2 ) oval round, lacking a seta but with rows of minute setules; endites with eight relatively scrapers gradually decreasing in size towards gnathobase, seventh scraper shortest and relatively stouter ( Fig. 2G View FIGURE 2 ). First four scrapers relatively slender and finely setulated, following four thicker and with relatively fewer and thicker denticles; gnathobasic ‘brush’ short and implanted with short spinules, gnathobase with a sensillum and three modified elements, of which first a bent seta, second a plump seta with small denticles in distal half and third a bifid seta; filter comb ( Figs 2G–J View FIGURE 2 ) with seven setae of which only the first shorter (half size of second), with setules implanted around its distal half. Third limb ( Figs 2K–O View FIGURE 2 ). Pre-epipodite round, epipodite round lacking projections; exopodite ( Fig. 2K View FIGURE 2 ) with rectangular corm, implanted with rows of minute denticles on inner side and seven large marginal setae in 2+5 arrangement; first exopodite seta longer than second; third exopodite seta more than two times as long as sixth exopodite seta, fourth and sixth setae subequal, fifth and seventh setae half size of the latter; all these setae plumose, except for sixth and seventh ( Fig. 2L View FIGURE 2 ) which are pappose in proximal half and plumose-serrulate in distal half. External endite ( Fig. 2M View FIGURE 2 ) with three setae (1’–3’) of which first two scraper-like, of similar size and with minute element in between, third (3’) shorter and with long setules; four well developed plumose setae on inner side (1”–4”) of same length; one naked element and four small setulated setae on internal endite ( Fig. 2N View FIGURE 2 ) preceding gnathobase; the latter with a bottle-shaped sensillum and large bent plumose seta with two naked elements at its base ( Fig. 2O View FIGURE 2 ). Filter comb with seven long setae ( Fig. 2M View FIGURE 2 ). Fourth limb ( Fig. 2P View FIGURE 2 ). Pre-epipodite oval, epipodite oval-round, lacking projections. Exopodite square, implanted with rows of minute denticles on inner side and with six marginal plumose setae; third exopodite seta longest, fourth longer than half preceding seta; fifth and sixth setae not narrow as in majority of Aloninae but as thick as other setae; sixth seta shortest, half the size of fifth. Endite with marginal row of four setae, first scraper-like and longer than flaming torch setae, following three ft setae plump with thick base, all of similar size, and one marginal round naked sensillum; gnathobase with one long setae, bent over endite and two reduced naked elements; on inner side, three long plumose setae (1”–3”) gradually increasing in size towards gnathobase and a filter comb with five slender setae. Fifth limb ( Figs 2Q–R View FIGURE 2 ). Pre-epipodite rectangular with round apex and implanted with long setules; epipodite heart-shaped, lacking projections. Exopodite ( Fig. 2Q View FIGURE 2 ) shape broadly oval, about two times as long as wide, with straight expanded margin between setae three and four and implanted with rows of minute denticles on inner side; four exopodite setae, gradually decreasing in size, first (dorsal) longest, oriented dorsally, about as long as exopodite itself; fourth exopodite seta as thick as other setae and similar length of third; inner portion of limb ( Fig. 2R View FIGURE 2 ) with broadly oval inner lobe with long terminal setules; two thick endite setae (1’–2’) of similar size, first slightly longer; behind second endite seta, a small elongated element oriented towards the gnathobase; gnathobase with no elements or setae.
Adult male and ephippial female described in Frey (1988). Ephippium dark brown to black ( Rühe, 1914). Our material contained no males or ephippial females.
Differential diagnosis. Ovalona weinecki is closest in morphology to A. meridionalis and, externally, to species of the Alona elegans -group ( A. elegans , A. salina , A. orellanai ). From the majority of other Alona -like chydorids with three main head pores, these differ in a relatively ovoid body shape, short antennules, round posteroventral carapace corner, a broad postabdomen with small postanal marginal denticles, deep preanal portion and rather deep anal margin. In case of Ovalona weinecki , the species can be recognized by 1. a strong wide striation on the valves, 2. large “wedge-shaped” labrum (noted in meridionalis , see Sinev 2006), 3. basal spine on postabdomen twice as long as claw thickness and mostly curved, 4. postabdomen with strongly pronounced preanal corner and anal margin longer than postanal margin and 5. first endopodal antennal spine exceeding second segment and apical endopod spine as long as the final segment. It differs from the close meridionalis in simple lateral head pores, longer terminal claw (longer than anal margin) and basal spine (twice as long as claw thickness) and deeper preanal corner; on limbs, weinecki lacks the first dorsal seta on P1 (first endite) and a seta on exII, which are both present in meridionalis .
Distribution and biology. Ovalona weinecki sensu lato is distributed in islands of Sub-Antarctic and Maritime Antarctic ( Frey 1988; Pugh et al. 2002): Falklands, South Georgia, South Orkneys, South Shetland Islands, Prince Edward Island, Kerguelen, Amsterdam, Marion, Macquarie, Heard Islands, lacking from neighboring continents. Includes all Southern Ocean records of Alona rectangula , which is absent from this region ( Pugh et al. 2002). True Ovalona weinecki may be restricted to the eastern islands in the Southern Ocean. Populations on the Kerguelen, ( Rühe 1914, Frey 1988), identical to ones redescribed here from Marion and Heard and likely the ‘true’ weinecki may belong to a separate species than those from the western islands, see under Discussion. We examined specimens from Easter Island identified as Alona weinecki in Dumont & Martens (1996). Close comparison of postabdomen and limb characters shows that it is far from the latter species complex but a member of the Alona pulchella -group, with South-American affinities. Ovalona weinecki does not occur in Easter Island.
Little is known about its biology, A. weinecki seems to have the general preference of Aloninae for littoral environments in freshwater lakes and ponds. Lives between plants and mud in the littoral, found in streams ( Rühe 1914); mainly in unmodified oligotrophic lakes ( Frey 1988). Paggi (1987) notes filamentous algae ( Spirogyra spp. ) in association with this species on Deception Island. Limbs suggest a soft bottom feeder (no strong scrapers).
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.
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Ovalona weinecki ( Studer, 1878 )
| Damme, Kay Van & Dumont, Henri J. 2008 |
Alona weinecki
| Dumont & Martens 1996 |
Alona inermis
| Pesta 1928 |
Alona capensis Rühe, 1914
| Ruhe 1914 |
Alona bukobensis var. subantarctica
| Ekman 1905 |
Alona subantarctica
| Ekman 1905 |
subantarctica
| Ekman 1905 |
Alona weinecki
| Studer, 1878 Alona weinecki Studer 1878 |