Maraura macracantha ( Smirnov and Timms, 1983 )

Sinev, Artem Y. & Shiel, Russell J., 2008, Redescription of Alona macracantha Smirnov and Timms, 1983 and its assignment to Maraura gen. nov. (Cladocera: Anomopoda: Chydoridae), Journal of Natural History 42 (45 - 46), pp. 2809-2824 : 2812-2818

publication ID	https://doi.org/ 10.1080/00222930802361048
persistent identifier	https://treatment.plazi.org/id/29079E54-C915-FFDD-6C3A-FDE3FC1AFA14
treatment provided by	Carolina
scientific name	Maraura macracantha ( Smirnov and Timms, 1983 )
status

Treatment

Maraura macracantha ( Smirnov and Timms, 1983) View in CoL

Alona macracantha in Smirnov and Timms, 1983, p. 48, Figure 54; Griggs, 2001, pp. 150–157, Figures 4.23–4.30.

Type location

Lake Cawndilla [misspelled in Smirnov and Timms (1983) as Cowndilla], Menindee Lakes, New South Wales, Australia, 32 ° 289S, 142 ° 159E.

Holotype

Female, Australian Museum, P31298.

Paratypes

Female, Zoological Museum of Moscow State University, 3095; female, Zoological Museum of Zoological Institute , St Petersburg , 3096.

Studied material

Eighteen females from Lake Numalla in Currawinya National Park via Hungerford, SW Queensland, Australia, 28 ° 449S 144 ° 189E, collected by B. V. Timms, April 2002 .

Diagnosis

As for genus.

Description

Parthenogenetic female. In lateral view, body is suboval, of moderate height (body height/body length about 0.58–0.63 in adults), with maximum height at the middle ( Figures 1A View Figure 1 , 2A View Figure 2 ). In dorsal view, the body is moderately compressed laterally. Dorsal margin evenly curved. Posterodorsal and posteroventral angles broadly rounded. Posterior margin weakly convex. Posteroventral corner of valves with about 50 very short setules of similar size, not organized into groups. A row of about a hundred very short setules along posterior margin on inner side of carapace. Ventral margin ( Figure 1B View Figure 1 ) almost straight, with about 50 setae, about 15 anteriormost setae long, next 10–12 setae very short, posteriormost 25 setae of moderate length, with length of setae increasing posteriorly. Anteroventral angle rounded. Carapace covered by prominent sculpture, polygonal in ventral part and linear in dorsal part.

Head of moderate size, triangular–round in lateral view. In lateral view rostrum does not appear especially elongated, protruding downwards. Ocellus large, almost twice as large as eye. Distance from tip of rostrum to ocellus 1.5 times larger than that between ocellus and eye. Head shield widening distally, with maximum width behind mandibular articulation ( Figures 1C View Figure 1 , 2C View Figure 2 ), covered by polygonal sculpture, less prominent than that of the valves. In dorsal view, rostrum narrow and elongated, with a distinctive rim at the tip ( Figure 2B View Figure 2 ). Posterior part of head shield broadly rounded, posterior margin with three or four pairs of symmetrically spaced notches. Three narrowly connected major head pores of equal size ( Figures 2D,E View Figure 2 and 3A,B View Figure 3 ). PP about 0.5 IP. Lateral head pores located in small depressions at about 1.5 IP distance from midline, at the level of the anterior pore.

Labrum of moderate size, labral keel wide, rounded, with rounded apex ( Figure 3D,E View Figure 3 ). Anterior margin of keel regularly convex or slightly wavy, posterior margin convex or with notch in the middle, without clusters of setules.

Postabdomen ( Figures 1D,E View Figure 1 and 2F,G View Figure 2 ) short, of moderate height, length-toheight ratio about 2.5. Ventral margin almost straight. Dorsal margin weakly convex in preanal part, concave in anal part, and convex in postanal part. Distal part of postabdomen obliquely truncated, so postanal part of dorsal margin comes to base of claws. Distal part of dorsal margin twice as long as preanal, with anal and preanal portions subequal in length. Preanal and postanal angles weakly defined.

Postabdomen provided with four to six short, slender marginal denticles, single or with one additional denticle behind, on postanal margin, and with five or six clusters of marginal denticles and setules on anal margin ( Figure 1F View Figure 1 ). Two distalmost clusters consisting of two or three short denticles, similar to postanal denticles, other clusters of five to eight setules. About 10 lateral fascicles of setules, postanal fascicles with thick and long distalmost setula, longer than marginal denticles. Several additional fascicles of very short setules present in postanal part above the main row of fascicles.

Postabdominal claw ( Figures 1G View Figure 1 , 2G View Figure 2 ) weakly curved, of moderate length, equal in length to preanal portion of postabdomen. Basal spine very long, sinuous, about half the length of the claw itself.

Antennule ( Figure 3E View Figure 3 ) long, narrow, not reaching the tip of the rostrum, with five transverse rows of short setules at anterior face. Antennular seta thin, of about one-third the length of the antennule, arising at two-thirds the distance from the base. Nine terminal aesthetascs of different length, the longest of them about half the length of the antennule.

Antenna ( Figures 1H View Figure 1 , 2H View Figure 2 ) relatively short. Antennal formulae, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Branches short, with numerous clusters of long setules. Basal segments of both branches 1.5 times longer than middle and apical segments. Seta arising from basal segment of endopodite a little longer than endopodite. Seta arising from middle segment of endopodite of same size as apical setae. Apical setae of both branches not differentiated. Spine on basal segment of exopodite of same length as middle segment. Spines on apical segments longer than segments bearing them.

Mandible of usual morphology for the subfamily. Maxillae ( Figure 1I View Figure 1 ) with three densely setulated setae directed towards its base, one of them one-third the length of the others.

Thoracic limb I ( Figure 3F View Figure 3 ). Epipodite globular, without finger-like projection. Accessory seta absent, conical hillock located in place of it. ODL seta long, with short robust setules ( Figure 3G View Figure 3 ). IDL with three setae and two or three clusters of setules on ventral face, seta 3 longest, subequal to ODL seta, seta 2 slightly shorter than seta 3, both with thin setules in distal part. IDL seta 1 slender and sharp, three times shorter than seta 3. Endite 3 with four setae subequal in length. Endite 2 with three setae setulated in distal part, longest of them subequal in length to ODL seta. Endite 1 with two two-segmented setae, both setulated in distal part, and very small naked setae on anterior face of limb. Six rows of long setules on ventral face of limb. Two ejector hooks, one a little larger than the other.

Thoracic limb II subtriangular ( Figure 3H View Figure 3 ). Exopodite narrow, elongated, of irregular shape, with slender setae two times shorter than the exopodite itself ( Figure 3J View Figure 3 ). Eight scraping spines, scrapers 1–5 long, increasing progressively in length distally, scrapers 3 and 5 significantly thicker than the others, armed with strong denticles. Scrapers 6–8 short, subequal in length. Distal armature of gnathobase with four elements. Filter plate II with seven setae, the posteriormost member considerably shorter than the others.

Thoracic limb III ( Figure 3I View Figure 3 ). Epipodite not clearly separated from the main body of the limb, without projection. Exopodite with seven setae, seta 3 being longest, length of setae 6 and 4 about one-half and one-third the length of seta 3, respectively, other setae short. Distal endite with 3 setae subequal in length, and a small sensillum. Two distalmost setae curved, sharp, without denticles in distal part; basalmost seta geniculated, with thin setules. Basal endite with four stiff setae, feathered in distal part, increasing in size in the basal direction. Four soft setae increasing in size basally, an elongated sensillum near the basalmost soft seta ( Figure 3K View Figure 3 ). Distal armature of gnathobase with four elements – an elongated sensillum narrowing distally, a geniculated seta, and two short spines. Filter plate III with seven setae.

Thoracic limb IV ( Figure 3L View Figure 3 ). Epipodite not clearly separated from the main body of the limb, without projection. Exopodite rounded, with six plumose setae, seta 3 being longest, setae 1, 2 and 5 subequal in length, less than half the length of seta 3, setae 6 and 4 very short. Inner portion of limb IV with four setae ( Figure 3M View Figure 3 ). Scraping seta long, slender, flaming-torch setae of similar shape, decreasing in size basally, each armed with about 10 setules distally. A small sensillum between bases of the middle and basalmost flaming-torch setae. Large sensillum retort-like. Three soft setae increasing in size basally. Gnathobase with a short two-segmented seta and a small hillock distally. Filter plate with five setae.

Thoracic limb V ( Figure 3N View Figure 3 ). Epipodite not clearly separated from the main body of the limb, without projection. Exopodite subrectangular, with four plumose setae, their length gradually decreasing from seta 1 to seta 4. Seta 4 with very broad, rounded base. Inner limb portion as wide, rounded lobe, with long setules on the inner margin. At inner face, two setulated distal setae, the distal one long, equal to seta 3 of exopodite, other three times shorter. Filter plate absent.

Thoracic limb VI absent.

Ephippial female. Unknown.

Male. No males were present in the studied material. According to Griggs (2001), the male is similar to the female in the shape of body. Eye larger than ocellus. Postabdomen of similar shape as in female, but postanal portion is shorter than anal. Clusters of short setules in place of marginal denticles. There was no information on the sperm duct location in Griggs’s description ( Griggs 2001). Postabdominal claw smaller than in female, with thinner basal spine.

Size. Length of adult female 0.42–0.51 mm, according to Griggs (2001), length of male about 0.3 mm.

Distribution and ecology

At present, M. macracantha is known from only from three widely separated locations in Australia. The type locality is Lake Cawndilla, Menindee Lakes, NSW (32 ° 289S; 142 ° 159E). Specimens were collected by R.J. Shiel on 22 May 1978. These lakes are shallow (2–3 m deep) pans on the western floodplain of the Darling River, which fills them during peak flows. There was no vegetation at the site of collection, water was turbid and wind stirred. The collection was from a zooplankton tow, which was otherwise dominated by about 20 species of rotifers. Other chydorids in the sample were Pseudomonospilus diporus ( Smirnov and Timms, 1983) , Alona rigidicaudis ( Smirnov, 1971) and Alona cf. rectangula Sars, 1863 . Specimens of Ilyocryptus sp. were also present in the sample, indicating stirred-up sediments. Copepods were the centropagids Boeckella triarticulata (Thomson, 1883) , Calamoecia lucasi Brady, 1906 , and cyclopoid Mesocyclops sp. Water temperature during the sampling was 9.2 ° C, water chemistry was 13.5 mg /l dissolved oxygen, pH 7.5, 10 nephelometric turbidity unit ( Shiel 1981).

The second site is Lake Logue, south-west Western Australia (29 ° 519S; 115 ° 089E); specimens were collected by David Cale on 14 October 2000. It is a big lake (more than 400 ha) in a nature reserve with basically intact vegetation. The lake was filled to a depth of about 3 m during spring 1999, after a long period of low depth (about 0.5 m). The lake was 2.52 m deep during the sampling. As at the previous site, there was no vegetation at the site of collection, water was turbid and wind stirred. Co-occurring taxa with M. macracantha were a diverse suite of cladocerans [ Alona rigidicaudis , Armatalona macrocopa (Sars, 1984) , Leberis diaphanus (King, 1853) , Leydigia sp., Pleuroxus foveatus Frey, 1991 , Pleuroxus inermis Sars, 1986 , Pseudomonospilus diporus , Ilyocryptus smirnov Kotov and Timms, 1998 , Macrothrix breviseta Smirnov, 1976 and Neothrix armata Gurney, 1927 ], rotifers, copepods and ostracods (for a full list of species see Keighery et al. 2004).

The third site is Lake Numalla, Queensland, (28 ° 449S; 144 ° 189E,), from which specimens were collected by Brian Timms in April 2002. This is a large lake (about 3000 ha) with maximum depth about 5 m, located in the Currawinya wetlands and surrounded by temporary pools. Water is fresh but becomes brackish in dry periods when the water level declines, turbid and wind stirred. Salinity at the time of collection was 3.2 g /l. Unfortunately, there are no data about vegetation on the collection site. Co-occurring plankters were rotifers ( Asplanchna , Brachionus , Filinia ), copepods ( Calamoecia , Boeckella , Apocyclops , Cletocamptus ) and a single cladoceran, Moina sp. The lake is also the type location for Ilyocriptus smirnovi (Kotov and Timms, 1998) .

It can be concluded that M. macracantha is a bottom-dwelling species adapted to turbid, wind-stirred waters of the open littoral of shallow permanent lakes.