Extremalona timmsi, Sinev & Shiel, 2012

Sinev, Artem Y. & Shiel, Russell J., 2012, Extremalona timmsi gen. nov., sp. nov., a new cladoceran (Cladocera: Anomopoda: Chydoridae) from an acid saline lake in southwest Western Australia, Journal of Natural History (J. Nat. Hist.) 46 (45 - 46), pp. 2845-2864: 2849-2858

publication ID

http://doi.org/ 10.1080/00222933.2012.727215

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scientific name

Extremalona timmsi

sp. nov.

Extremalona timmsi   sp. nov.

( Figures 2–5 View Figure 2 View Figure 3 View Figure 4 View Figure 5 )

Type locality

A lake at Guest Road , Grass Patch, 79 km north of Esperance, Western Australia, Australia 33 ◦ 06 ′ S, 121 ◦ 44 ′ E ( Figure 1 View Figure 1 ). Samples collected by Brian Timms on 12 March 2007 GoogleMaps   .


Parthenogenetic female from the type location, deposited in Western Australian Museum, slide C47938 View Materials .  


Ephippial female, male and ephippium from the type location, deposited in Western Australian Museum, slide C47938 View Materials ; parthenogenetic female, three ephippial females, two males, juvenile male of instar II from the type locality, presently in the first author’s personal collection, AYS-AU-011   .

Several ephippial females from the type location, two males and one juvenile male of instar II were dissected and not kept afterward.


The species name honours the species collector, the prominent Australian limnologist Brian Timms.


As for genus.


Parthenogenetic female. Preserved specimens of intense yellow-brown colour. In lateral view ( Figure 2A View Figure 2 ), body irregular oval, moderately high, with maximum length at posterodorsal angle. Maximum height at the middle of the body in adults, height/ length ratio about 0.7. Dorsal margin convex, posterodorsal and posteroventral angles broadly rounded. Posterior margin weakly curved. Anteroventral angle rounded. carapace covered by weakly defined longitudinal lines with dense fine striae between them.

As only two parthenogenetic specimens were present in our material, detailed morphology was studied for ephippial females, which did not differ from parthenogenetic ones in morphology of head pores, postabdomen and head and thoracic limbs in the family Chydoridae ( Smirnov, 1971)   .

Ephippial female ( Figures 2B, C View Figure 2 , 3A, B View Figure 3 ) with body as high as in parthenogenetic female, dorsal outline highly arched, posterodorsal angle of valves obtuse, posterior margin of valves straight, ventral margin of valves less convex than in parthenogenetic female. Ephippium very dark brown to black, non-transparent, without distinctive sculpture. Posterodorsal angle with about 20–25 short setules of similar size, passing into a row of about 100 setules along the posterior margin ( Figure 2D View Figure 2 ), at some distance from the margin on inner side of carapace. Ventral margin almost straight, with about 50 short setae. Anteroventral angle rounded. carapace covered by weakly defined longitudinal lines with dense fine striae between them.

Head is set relatively high for Aloninae   , tip of rostrum located at half-height of the body. In lateral view head small, low triangular-round, rostrum short, directed forward and downward. Eye larger or equal to ocellus. Distance from tip of rostrum to ocellus about 1.5 times that between ocellus and eye.

Head shield relatively narrow, with maximum width behind mandibular articulation, covered by same striae as valves ( Figure 2E View Figure 2 ). Rostrum short, broadly rounded. Posterior part of head shield protruding, posterior margin of head shield broadly rounded. Three narrowly connected major head pores of same size ( Figures 2F View Figure 2 , 3C View Figure 3 ) evenly spaced. PP about 1.0–1.2 times IP. Lateral head pores elongated, located about 1.1–1.2 times IP distance from midline, at the level of the middle major head pore.

Labrum ( Figure 2G–I View Figure 2 ) with elongated, narrow oval keel (height/width ratio about 2.5), with rounded apex. Anterior margin of keel convex, posterior margin convex or straight without clusters of setules. Several specimens in the studied material had abnormal labral keels ( Figure 2J, K View Figure 2 ).

Thorax twice as long as abdomen, dorsal surface of abdominal segments not saddle-shaped. No abdominal joint.

Postabdomen ( Figures 3D View Figure 3 , 4A, B View Figure 4 ) slightly curved, narrowing distally, with broadly rounded dorsodistal angle. Length about 3–3.5 times height. Ventral margin weakly convex. Basis of claws bordered from distal margin by clear incision. Distal margin almost straight. Dorsal margin with distal part about 1.3–1.5 times longer than preanal one, with postanal portion half length of anal portion. Postanal portion of distal margin weakly convex, anal portion concave. Preanal angle well defined, prominent, postanal angle not defined. Preanal margin slightly concave. Postabdomen with 10–12 clusters of marginal setules, decreasing in size basally, along preanal and anal margin, even in preanal portion these clusters are similar to lateral groups of setules. In preanal portion each cluster consists of two to seven setules, length of longest setules in postanal clusters little less than width of base of postbdominal claw. Lateral fascicles of setules numerous, spaced irregularly; main row consists of 9–11 broad fascicles, additional smaller fascicles located above the main row in postanal portion and basal part of anal portion. Several rows of setules in preanal portion of postabdomen close to preanal angle. First setules in postanal fascicles thicker than others. Postabdominal claw curved, of moderate length, about two-thirds the length of preanal portion of postabdomen. Basal spine thin, about 0.3 times length of claw, a cluster of long setules located near its base.

Antennule ( Figure 4C View Figure 4 ) comparatively large and broad, reaching the tip of rostrum, without clusters of setules at anterior face. Length/width ratio about 2. Antennular sensory seta slender, about two-thirds length of antennule, arising at two-thirds distance from the base. Nine aesthetascs, three of them 1.3–1.4 times longer than others, as long as of antennule, others of similar size. All aesthetascs projecting beyond anterior margin of head shield.

Antenna short ( Figure 4D View Figure 4 ). Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0- 0-1. Basal segment robust, branches short and stout. Basal segment of endopodite 1.5 times and two times longer than middle and apical parts of same branch, respectively; basal segment of exopodite three times longer. Seta arising from basal segment of endopodite thin, as long as endopodite itself. Seta arising from middle segment of endopodite slightly smaller than apical setae. Apical setae of similar size and thickness. Spine on basal segment of exopodite about two-thirds length of middle segment. Spine from apical segment of exopodite about two-thirds length of this segment. Spine from apical segment of exopodite about half length of this segment.

Thoracic limbs: five pairs. Epipodites of all limbs not clearly separated from the main body of the limb, without any projections.

Limb I ( Figure 4E, F View Figure 4 ) of moderate size. ODL with exceptionally long seta, more than three-quarters length of limb body. Accessory seta about one-quarter length of ODL seta. IDL with three setae, seta 1 well-developed, sharp and slender, about onethird length of ODL seta. Setae 2 and 3 of similar shape, armed with thin setules in distal part, about two-thirds and three-quarters length of ODL seta, respectively. Endite 3 with four setae of similar length. Endite 2 with three setae of different length, longest of them (seta e) as long as IDL seta 3, two others much shorter. Endite 1 with two distally setulated two-segmented setae (g, h) and a long flat seta (i). No naked inner setae and sensillae found on endites 1 and 2. Six rows of thin long setules on ventral face of limb. Two ejector hooks of similar size. Maxillar process not found.

Limb II ( Figure 5A View Figure 5 ). Exopodite elongated, with minute seta; eight scraping spines ( Figure 4J View Figure 4 ), evenly increasing in length distally, scrapers 5 and 6 armed with more robust setules than others. A small inner seta is located near the base of scraper 1. Distal armature of gnathobase with four elements. Filter plate with seven setae, two posteriormost considerably shorter than others.

Limb III. Exopodite ( Figure 5B View Figure 5 ) of irregular shape, with six setae. Seta 3 being longest, armed with thin setules. Setae 4–6 of same morphology and similar size, plumose in distal part, evenly decreasing in size basally. Seta 4 about two-thirds length of seta 3, seta 6 about half length of seta 3. Seta 1 about one-quarter length of seta 3, seta 2 very short. Distal endite ( Figure 5C View Figure 5 ) with three setae and two small sensillae between their bases, two distalmost setae (1–2) slender, with distal parts unilaterally armed with denticles; basalmost seta (3) with shortened distal portion, bilaterally armed with long setules. Basal endite with four setae, increasing in size in basal direction. Gnathobase not clearly separated from basal endite. Four inner setae of similar size ( Figure 5D View Figure 5 ), a small sensillum near the base of distalmost seta. Distal armature of gnathobase with four elements. The first one elongated, cylindrical sensillum, second thin, bent seta, others two short spines. Filter plate III with seven setae.

Limb IV. Exopodite ( Figure 5E View Figure 5 ) as broad oval lobe with six plumose setae. Seta 1 very broad, longest, setae 2 and 3 about three-quarters length of seta 1, setae 5 and 6 about two-thirds length of seta 1, seta 6 about half length of seta 1. Inner lobe of limb IV with four setae ( Figure 5F, G View Figure 5 ). Distalmost scraping seta (1) short, with broad base, three flaming-torch setae (2–4) strongly decreasing in size basally. Sensillum elongated. Three inner setae increasing in size basally. Gnathobase with two-segmented seta, and a small hillock distally. Filter plate with five setae.

Limb V ( Figure 5H View Figure 5 ). Exopodite low oval, not divided into two lobes, with four plumose seta. Setae 2, 3 and 4 about two-thirds, one-half and one-quarter length of seta 1, respectively. Inner limb portion an elongated lobe, length about twice width, with setulated inner margin. At inner face, two setae of same size, as long as exopodite seta 3. Filter plate as a single seta, no sensillum-like structure near it.

Male. Juvenile males of instar II ( Figure 2L View Figure 2 ) and adult males ( Figures 2M View Figure 2 , 3F View Figure 3 ) similar in shape and size, small in comparison with females. Body low oval, height/length ratio about 0.6, maximum height before the middle of the body. Ocellus much smaller than eye.

Postabdomen. In juvenile males of instar II ( Figure 4G View Figure 4 ), lower than that of female, with almost parallel margins, with clear step on ventral margin in region of gonopores. Gonopores large, round, located close to ventral margin at three-quarters distance from its base. Armament of postabdomen similar to that of female, but setules in both marginal clusters and lateral fascicles are less numerous. Postabdominal claw same as in female. In adult male, postabdomen short, with almost parallel margins in distal portion, dorsodistal angle broadly rounded ( Figures 3G View Figure 3 , 4K View Figure 4 ). Preanal angle not defined, postanal angle well-defined. Distal part of postabdomens 1.2–1.3 times longer than preanal. Sperm duct openings located almost at the end of postabdomen. Armament of postabdomen similar to that of female, but setules in postanal clusters are somewhat shorter. Postabdominal claw shorter than that of female, about two-thirds of preanal margin length, basal spine of same size as in female.

Antennule. In instar II male antennule slightly broader than in female, with anlage of male seta located opposite the base of antennal seta, aesthetascs same as in female ( Figure 4H View Figure 4 ). In adult male antennule much broader than in female ( Figure 4L View Figure 4 ), with nine terminal and six lateral aesthetascs as long as terminal ones. Male seta arising at one-third antenna length from tip, exceeding one-third of antennule length.

Thoracic limb I. In instar II male, copulatory hook curved ( Figure 4I, J View Figure 4 ). Ventral face of limb with anlage of copulatory brush seta and a peculiar hillock above it, not present in any other instar. IDL with anlage of male seta, other setae same as in female. In adult male, copulatory hook U-shaped ( Figure 3M, N View Figure 3 ). Copulatory brush and copulatory brush seta present. Row of about 40 long, dense setules on ventral face of limb under copulatory brush, endite 3 with several clusters of very long setules. IDL seta 1 thinner than in previous instar, moved to the inner margin of IDL, setae 2 and 3 subequal in length, thinner and shorter than in previous instar, male seta thick, curved, as long as seta 2. Endites with setae same as in female.

Size. In the studied population, length of two adult parthenogenetic females was 0.49 and 0.51 mm, height 0.35 and 0.36 mm, respectively; in ephippial females length 0.44–0.57 mm, height 0.29–0.40 mm; in single instar II male length 0.31 mm, height 0.20 mm; in adult males length 0.33–0.34 mm, height 0.19–0.21 mm.


Extremalona timmsi   sp. nov. is known to date only from the type locality, B.V. Timms’ field sites 4 [Guest Rd (west)] and 5 [Guest Rd (southeast)], without official name, but named from the nearest road, 33 ◦ 06 ′ S, 121 ◦ 44 ′ E and 33 ◦ 08 ′ S, 121 ◦ 49 ′ E, respectively ( Timms, 2009). Guest Rd west was c.3.2 ha when full, 22 cm mean depth, c. 50 cm maximum, pH 3.7–5.8, salinity 11–95 g /l (on two occasions on which Extremalona   gen. nov. was collected: 33–37 g /l), turbidity10–250 NTU. Guest Rd southeast was. 2.6 ha when full, 49 cm mean depth, c. 150 cm maximum, pH 3.7–7.8, salinity 4–182 g /l, turbidity10–130 NTU). Co-occuring acidophile microinvertebrates and macroinvertebrates are tabled in Timms (2009). Extremalona timmsi   sp. nov. is the only species of chydorid recorded from such an environment to date. Co-occurring cladocerans were Daphnia carinata   s.l. in site 5, and Moina cf. australiensis   in both sites 4 and 5 (see table 2 in Timms 2009).












Extremalona timmsi

Sinev, Artem Y. & Shiel, Russell J. 2012

Extremalona timmsi

Sinev & Shiel 2012


Sinev & Shiel 2012

Extremalona timmsi

Sinev & Shiel 2012

Moina cf. australiensis

Sars 1896