Alonella dadayi Birge, 1910

Sousa, Francisco Diogo R., Elmoor-Loureiro, Lourdes M. A., Maia, Sarah Souza & Panarelli, Eliana A., 2020, More than just the number of denticles: morphometric and limb variability in Neotropical cladoceran Alonella dadayi (Crustacea: Cladocera: Chydoridae), Zootaxa 4759 (2), pp. 287-299 : 288-297

Alonella dadayi Birge, 1910

( Figs 1-6 )

Leptorhynchus dentifer in Daday (1905) ; Disparalona dadayi in Van de Velde et al., (1978) ; Hollwedel et al. (2003) and Elmoor-Loureiro (1997)

Material Examined. Ceará— Two adult parthenogenetic females from a swamp on Ypioca Farm, São Gonçalo

do Amarante (S 3°34’39’’, W 38°52’31’’), material collected on 19.xii.2007, leg. Maria Beatriz Gomez e Souza ( FDRS 114). Four adult parthenogenetic females from Guaribas Stream , São Gonçalo do Amarante (S 3°33’19”, W 38°52’27”), material collected on 18.xii.2007, leg. Maria Beatriz Gomez e Souza ( FDRS113 ) . Federal District— Three adult parthenogenetic females from Henrique pond, Brasília National Park (S 15°41’18”, W 47°56’26.10”), material collected by GEEA in xii.2009 ( FDRS102 ) . One adult parthenogenetic female from Meandros pond Brasília National Park (S 15°43’29.80”, W 47°58’08.90”), material collected by GEEA in ix.2009 ( FDRS103 ) . Two adult parthenogenetic females from Bonita Pond, Estação Ecológica de Águas Emendadas , Planaltina (S 15°35’22.1”, W 47°41’50.1”), material collected by GEEA on 12.v.2008 ( FDRS110 ) . Ten adult parthenogenetic females from Taquara pond, Planaltina (S 15°38’12.4”, W 47°31’22”), material collected by GEEA on 15.viii.2006, 28.viii.2008 and 06.v.2008 ( FDRS111 , 476-478 ) . Nineteen adult parthenogenetic females from Cedro pond, APA Gama e Cabeça-de-Veado , ParkWay (S 15°53’49.7”, W 47°56’36.6”), material collected by GEEA on 19.ix.2006, 18.ix.2008 and 03.iii.2009 ( FDRS112 , 483-485 ) . Fifteen adult parthenogenetic females from Barraginha pond (S 15°58’12.1’’, W 47°55’58.3’’), material collected by GEEA on 01.ix.2006 ( FDRS481 ) . Thirteen parthenogenetic females from Joaquim Medeiros pond, Planaltina (S 15°38’15.9”, W 47°41’29.5”), material collected by GEEA on 25.viii.2008 ( FDRS482 ) . Fourteen adult parthenogenetic females from Paranoá Lake, Brasília (S 15°43’47”, W 47°52’58”), material leg. Ciro Y. Joko ( FDRS402 , 493 ) . Goiás— Six adult parthenogenetic females from Cabocla Pond, Campo de Instrução de Formosa, Formosa (S 15°48’15”, W 47°14’57.50”), material collected by GEEA in xii.2009 ( FDRS106-107 ) . Two adult parthenogenetic females from a Swamp in the Paranã River Basin, Formosa (S 15°09’ 15.8”, W 47°28’04.7”), material collected by Ciro Y. Joko on 20.xiii.2003 ( FDRS604 ) . Maranhão— Three adult parthenogenetic females from Esperança Pond, Lençóis Maranhenses (S 2°29’4.38”, W 43° 7’42.66”), material collected on 01.vii.2000, leg. Maria José Saraiva Lopes ( FDRS599 ) . Mato Grosso— One adult parthenogenetic female from a first order Stream, Tanguro Farm (S 12°59’35.88”, W 52°20’32.30”), material collected by Thiago Borges Kisaka in viii.2017 ( FDRS536 ) . Twelve adult parthenogenetic females from a dam, Tanguro Farm (S 13°3’25.38”, W 52°23’16.08”), material collected by Thiago Borges Kisaka in viii.2017 ( FDRS536 ) . Two adult parthenogenetic females from a water body along the Transpantaneira road, Poconé (S 16°25’31”, W 56°40’8”), material collected by Lourdes Maria A. Elmoor-Loureiro on 06.ii.1986 ( FDRS605 ) . Mato Grosso do Sul— One adult parthenogenetic female from Nhumirim Farm , Celia’s Bay , Corumbá (S 18°59’49.5”, W 56°38’16.1”), material collected by Valéria Barros on 06.ix.2000 ( FDRS475 ) . Eighteen adult parthenogenetic females from Vereda (S 18°10’59.03”, W 54°53’44.93”), material collected by Adriana M. Guntzel on 10.xii. 2011 ( FDRS572 ) . Minas Gerais— Ten adult parthenogenetic females from Mascates Stream , Serra do Cipó (S 19°24’32.40”, W 43°34’34.68”), material collected by Eliana A. Panarelli on 09.vii.2010. One adult parthenogenetic female from a natural pond, Alto do Caparaó (S 20°25’47”, W 41°51’57”), material collected by Lourdes Maria A. Elmoor-Loureiro on 27.i.1991 ( FDRS597 ) . Paraná— Two adult parthenogenetic females from the Ressaco do Páu-Veio, Paraná River Basin floodplain, Porto Rico (S 22°44’54”, W 53°15’25”), material collected by Lourdes Maria A. Elmoor-Loureiro on 26.iii.2009 ( FDRS595 ) . Pernambuco— Five adult parthenogenetic females from the Dois Irmãos dam, Recife (S 8°00’51”, W 34°56’47.7”), material collected by Lourdes Maria A. Elmoor-Loureiro on 17.i.2000 ( FDRS596 ) . Rio Grande do Norte— Eight adult parthenogenetic females from a pond near the BR101 road, São José do Mipibú (S 06°04’45”, W 35°14’17”), material collected by Lourdes Maria A. Elmoor-Loureiro on 20.vii.1985 ( FDRS603 ) . Rio Grande do Sul— One adult parthenogenetic female from a Pond in the Knorr Park , Gramado (S 29°22’36”, W 50°52’5”), material collected by Lourdes Maria A. Elmoor-Loureiro on 31.x.2001 ( FDRS602 ) . One adult parthenogenetic female from Canal Leste, Taim Ecological Station , Taim (S 32°38’39.5”, W 52°35’04”), material collected by Lourdes Maria A. Elmoor-Loureiro on 29.xii.2001 ( FDRS601 ) . São Paulo— Six adult parthenogenetic females from Fontes do Ipiranga , São Paulo (S 23°38.328’, W 46°37.275’), material collected by Lourdes Maria A. Elmoor-Loureiro on 08.x.2010 ( FDRS598 ) . Tocantins— One adult parthenogenetic female from the Araguaia River, Ximboá (S 6°24’22”, W 48°32’8”), material collected by Lourdes Maria A. Elmoor-Loureiro on viii.2003 ( FDRS600 ) .

Description. Parthenogenetic female. General ( Fig. 1 A-D). Body from relatively elongated to short; dorsal margin arched, without a dorsal keel or projections; in both dorsal and ventral views, the body may or not exhibit a moderate lateral compression.

Carapace ( Fig. 1 A-F). Covered by longitudinal lines or hexagons and striae; the anteroventral margin has an evident flange; the ventral margin is almost rounded or with a distinctive rounded angle at 1/3 of the margin’s length. There are 37-48 plumose setae at valve ventral margin (the real number of setae is not represented in the figures); median groups of setae are located exactly at the valve’s margin and are clearly not articulated; the setae of the posterior group are internally articulated. Posterior margin straight, rounded or slightly concave; posterodorsal corner with or without a notch; posteroventral corner rounded which may not have denticles (0-8); when denticles are absent the posterior border bears spinulae, being the proximal ones longer than distal ones; when two or more denticles are present, short spines or setulae might be present between them.

Head ( Fig. 2 A-Q). Rostrum long and curved; its tip might reach the same level as the ventral line of the valve, sharp or bifid, narrow or expanded (in frontal view), about 2.9-3.2 times longer than the antennular body. Ocellus smaller than the eye.

Head shield ( Fig. 2 A-J). Not completely studied. Posterior region triangular-shaped or rounded, covered by striae; two main pores and two very small, closely-set pores between them; these tiny pores are located either at half the distance between the main head pores or near to anteriormost main pore, PP/IP about 0.54.

Labrum ( Fig. 2 A-J). With labral keel elongated, either with or without a notch.

Antenna I ( Fig. 2 N-O). Approximately two times longer than wide, never extending beyond the tip of the rostrum; antennular sensory seta slender, about 1.3-1.6 times shorter than the length of the antennular body, inserted near the apex of the antennular body; nine aesthetascs which do not extend beyond the length of the antennular body.

Antenna II ( Fig. 2 P-Q). Basal segment thick, with a short and thin spine; first exopodite segment longer than the first segment of the endopodite and armed with a seta of similar length or slightly longer than the segment itself. Second exopodite segment with a long seta as long as the longest apical setae; apical spine of the exopodite longer than endopodite apical spine, about 1.8 times longer or similar in length to segment itself. Apical segment armed with a thin and slender seta with about 1/3 the length of the longest apical setae; first endopodite segment armed with a spine about 2.3-2.6 times shorter than the apical spine; apical spine of the endopodite shorter than the segment itself. Antennal formula (exo/endo): spines 001/101, setae 113/003.

Five pairs of thoracic limbs ( Fig. 3 A-L)

Trunk limb I ( Fig. 3 A-D). Epipodite oval, armed with a long, digitiform projection. ODL armed with a short seta and a thin seta longer than (or similar in length to) IDL first seta, the latter serrated or armed with long setulae. IDL (en 4) with one or two groups of short setulae; three setae present, seta 1 about 1.3-2-5 times shorter than the second seta; seta 2 about 1.3 times shorter than the third seta, all armed with long setulae; endite 3 with four setae, posterior setae (a-b) of similar length among themselves, longer or similar in length to the anterior seta 1, seta (c) of similar length to setae (a-b); endite 2 with three posterior setae present (d-f); setae (e-f) similar in length, both setae bearing thin setulae on their lateral face; seta (d) slightly shorter than (e-f); endite 1 with three posterior setae similar in length (g-i), which are bisegmented and densely setulated on the distal part, seta (j) plumose and approximately 2.6 times shorter than seta (i); ejector hooks of similar length among themselves and armed with spines; ventral face of the limb with 7-9 groups of setulae. Gnathobase as a setulated setae.

Trunk limb II ( Fig. 3 E-F). Exopodite short, armed with a seta similar in length to the exopodite itself; inner limb portion armed with eight slender scrapers; setulation on the scrapers are inconspicuous; scraper 1 markedly longer than the others, length of scraper 2 about 0.65 times the length of scraper 1 and similar in length to scraper 3; scrapers 5-7 markedly shorter than scraper 8; scraper 8 about 2.5 times longer than scraper 7; proximal portion of the gnathobase flattened; distal portion armed with three elongated elements, with the first element armed with strong denticles; filter comb with seven setulated setae.

Trunk limb III ( Fig. 3 G-H). Epipodite oval, with a long projection; exopodite rectangular, approximately as long as wide, with four distal and three lateral setae; seventh seta setulated and longer than the sixth and fifth setae; fourth seta setulated, about two times longer than the third seta; third seta setulated and about 1.5 times shorter than the second seta; second seta setulated, longer than the first setae, with about 0.7 times the length of the fourth seta; first seta armed with short setulae; distal endite with three slender setae, seta 2 with about 0.55 times the length of seta 1; seta 3 short, about two times shorter than seta 2; five plumose posterior setae decreasing in length towards the gnathobase (a-e); basal endite with four setae of similar length (4-7); gnathobase armed with a long and cylindrical sensillum; filter comb with eight setulated setae.

Trunk limb IV ( Fig. 3 I-J). Pre-epipodite oval and densely setulated; epipodite oval, with a long projection; exopodite with seven marginal setae; setae 2-7 plumose; setae 5-7 similar in length; setae 4 and 2 relatively long and similar in length; seta 3 about two times shorter than seta 4; seta 1 robust and similar in length to seta 3; distal endite with four setae (1-4), seta 1 scraper-like and with a thin spine at its middle-length, and setae flaming-torchlike with long setulae (3-4); first flaming-torch similar in length to seta 1; basal endite armed with three setulated setae of similar length; gnathobase thick, with two elements, armed with one curved setulated seta which is similar in length to the width of the endite; filter plate with six setae.

Trunk limb V ( Fig. 3 K-L). Pre-epipodite rounded and densely setulated; epipodite oval, with a long projection; exopodite wide, rounded, and armed with four plumose setae and two setulated hillocks implanted near the first seta; first seta about 0.75 the length of the second seta; third and fourth setae similar in length and longer than the other setae of the limb; internal lobe elongated, relatively rectangular and with many setulae; seta 1 setulated, about 1.2 times longer than seta 2; seta 2 laterally armed with thick spinulae; filter comb with four setulated setae, with about 0.7 of length of the internal lobe setae.

Abdomen ( Fig. 4 A-B). About three times shorter than the thorax, five transverse rows of setulae present at its dorsal surface.

Postabdomen ( Fig. 3 A-B). About 2.5-3 times longer than wide, narrowing towards the distal portion., ventral part relatively straight and with two rows of short setulae; preanal part relatively long, angle clearly prominent; anal margin about 0.7-0.85 of length of the preanal margin, armed with a group of 6-8 thin spines and a group of long setulae that exceeds the margin of the postabdomen; postanal margin rounded or straight about 1.7-2 times shorter than the anal margin, armed with 5-8 marginal and long denticles that reach 1/3 of the length of the postabdominal claw. Lateral fascicles might be formed by thin (short or long) spinulae separated in groups; postabdominal setae with about 1/2 the length of the postabdomen, bisegmented, and armed with setulae in the distal segment.

Postabdominal claw bearing two basal spines, with about 0.23-0.29 of the length of the postabdomen; with a subterminal flagellum. Basal spines naked, distal about 0.19 of length of the postabdominal claw, proximal spine about 2.3-3.5 times shorter than the distal one.

Size. Parthenogenetic female length ranging between 0.37-0.53 mm, height/length ratio ranging between 0.65- 0.7.

Differential diagnosis. Alonella dadayi is recognizable by a series of morphological traits: (1) a long and curved rostrum, (2) postabdomen narrows towards the distal portion, and (3) a markedly concave anal margin. Specifically, A. dadayi differs from A. nana (Baird 1950) in relative length of body and the morphology of the postabdomen. The long and curved rostrum of A. dadayi is markedly different from that of A. excisa (Fischer, 1854) , A. clathratula Sars, 1896 , A. pulchella Herrick, 1884 , A. exigua (Lilljeborg, 1900) , A. breviceps Stingelin, 1905 and A. hampelae Alonso & Kotov, 2017 .

Morphometric Analysis. Three effective principal components (PC) described 97.91% of the total variation in the carapace shape of Alonella dadayi . Regarding the postabdomen, 10 effective principal components (PC) described 98.59% of the shape’s total variation. The reconstruction of the morphometric variation of the carapace and the postabdomen is described by mean values and standard deviation. For the carapace, the PC1 indicated a nonoverlapping of the lines on the anterior part, ventral margin and posterodorsal part ( Fig. 5 ). On the other hand, for the postabdomen, the PC1 indicated a non-overlapping of the lines for the preanal angle, the PC2 reported the same for the anal and preanal margins, and the PC3 also reported the same for the ventral postanal margins ( Fig. 6 ).

Distribution and ecology. It occurs from the Southern part of North America to South America. In Brazil, Alonella dadayi can be considered as the most common species of Chydoridae , inhabiting ponds, dams, lakes, streams and rivers (for a detailed geographic distribution, see Brazilian Cladocera project https:// cladocera .wordpress.com/). It is always associated with fine-particle sediments, organic detritus or macrophytes.

Figures

FIGURE 1. Alonella dadayi Birge, 1910 parthenogenetic female from Pantanal, Brazil (A, C) and Serra do Cipó, Minas Gerais, Brazil (B, D). A-B, habitus. C-D, dorsal view of carapace. E, posteroventral corner of carapace. F, setae of median part of carapace ventral margin non-articulated. G-Z, outline of carapace showing the range of variability. Scale bars = 50 μm (Figs. A-E); 25 μm (Fig. F). Figs. G-Z were not scaled.

FIGURE 2. Alonella dadayi Birge, 1910 parthenogenetic female. A-J, lateral view of head showing the range of variability in curvature and length of rostrum and morphology of labrum. K, frontal view of rostrum. L-M, head pores. N-O, antennae I. P-Q, antennae II. Scale bars = 50 μm.

FIGURE 3. Alonella dadayi Birge, 1910 parthenogenetic female from Pantanal, Brazil.A, trunk limb I. B, idem, arrows showing stiff setae on endites. C-D, idem, showing the variability of ODL and IDL. E, trunk limb II. F, idem, variability in the morphology of scrapers. G, trunk limb III. H, idem, outline of exopodite. I, trunk limb IV. J, idem, outline of exopodite. K, trunk limb V. L, idem, outline of exopodite. Scale bars = 50 μm. Figs. H, J, L were not scaled.

FIGURE 4. Alonella dadayi Birge, 1910 parthenogenetic female from Pantanal, Brazil (A) and Serra do Cipó, Minas Gerais, Brazil (B). A-B, postabdomen. C, outlines represent the range of variability on the shape of postabdomen (not scaled). Scale bars = 50 μm.

FIGURE 5. Reconstruction of carapace variation shape of Alonella dadayi based on the three effective principal components. PC1 = 81.55%; PC2 = 13.85%; PC3 = 2.50%.

FIGURE 6. Reconstruction of postabdomen variation shape of Alonella dadayi based on the ten effective principal components. PC1 = 40.77%; PC2 = 22.80%; PC3 = 14.29%; PC4 = 6.93%; PC5 = 4.17%; PC6 = 3.46%; PC7 =2.27%; PC8 = 1.68%; PC9 = 1.31% PC10 = 0.85%.