Elephantis natalensis ( Bouvier, 1925 ) Castelin & Marquet & Klotz, 2013

Castelin, Magalie, Marquet, Gerard & Klotz, Werner, 2013, Elephantis, a new genus for Caridina natalensis Bouvier, 1925 from eastern rivers of Madagascar, Zootaxa 3702 (6), pp. 573-586 : 577-583

Elephantis natalensis ( Bouvier, 1925) comb. nov.

( Figs. 2–4 , color plate 1 )

Caridina natalensis comb. nov. Richard & Clark, 2009: 22 –25, figs 7, 8.

Caridina africana De Man in Weber, 1897: 170 –174, fig.2; Lenz, 1912: 5.

Caridina africana forme natalensis Bouvier, 1925: 214 .

Caridina nilotica Barnard, 1950: 662 .

Material examined: 100 specimens from Madagascar, totalling 22 males, 52 ovigerous females and 26 non ovigerous females. One non ovigerous female cl 6.7 mm; 18 ovigerous females cl 5.8–8.8 mm; one male cl 4.4 mm (Station 1) ( MNHN -IU-2009-2682 ), coll. P. Bosc, H. Grondin & P. Valade, 01. May 2004 . One male cl 4.1 mm (Station 1) ( MNHN -IU-2009-2689 ), coll. P. Bosc, H. Grondin & P. Valade, 01. May 2004 . 12 ovigerous females cl 5.3–6.1 mm; 2 males cl 4.5 and 5.0 mm (Station 2) ( MNHN -IU-2009-2683 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . One male cl 3.9 mm (Station 2) ( MNHN -IU-2009-2691 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . 3 ovigerous females cl 5.0– 5.5 mm; 4 males cl 3.0– 4.5 mm (Station 3) ( MNHN -IU-2009-2684 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . One male cl 4.4 mm, (Station 3) ( MNHN -IU-2009-727 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . 2 ovigerous females cl 6.0 and 6.1 mm (Station3) ( MNHN -IU-2009- 728 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . 2 ovigerous females cl 6.0 and 6.1 mm (Station 3) ( RMNH. CRUS.D.55046 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . 2 ovigerous females cl 6.1 and 6.5 mm (Station 3) ( OUMNH. ZC.2012-05-005 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . One non ovigerous female cl 6.7 mm (Station3) ( MNHN -IU-2009-2688 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . One male cl 4.8 mm (Station3) ( OUMNH. ZC.2012-05-065 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . One male cl 4.7 mm (Station3) ( RMNH. CRUS.D.55047 ), coll. P. Bosc, H. Grondin & P. Valade, 08. May 2004 . 18 non ovigerous females cl 4.0– 5.9 mm; 3 ovigerous females cl 4.6–5.2 mm; 5 males cl 3.4–4.1 mm (Station 4) ( MNHN -IU-2009-2685 ), coll. E. Feunteun & T. Robinet, 03. July 2008 . 2 non ovigerous females cl 4.1 and 4.7 mm; one male cl 3.0 mm (Station 5) ( MNHN -IU-2009-2686 ), coll. H. Grondin, G. Marquet & T. Robinet, 08. May 2010 . 3 non ovigerous females cl 3.4–4.0 mm; 8 ovigerous females cl 5.6–6.4 mm; 2 males 3.1 and 4 mm (Station 6). ( MNHN -IU- 2009-2687 ), coll. H. Grondin, G. Marquet & T. Robinet, 21. May 2010 . One ovigerous female cl 5.3 mm (Station6) ( MNHN -IU-2009-2690 ), coll. H. Grondin, G. Marquet & T. Robinet, 21. May 2010 . One ovigerous female cl 6.1 mm, one non ovigerous female, two males cl 4.3 and 4.6 mm (Station6) (coll. WK 54- 11), coll. H. Grondin, G. Marquet & T. Robinet, 21. May 2010 .

Description. Cephalothorax and cephalic appendages. Carapace length 3.1–8.8 mm. Rostrum ( Figure 2A ) slightly sigmoid, pointed, unarmed near tip, reaching to mid-length of second segment of antennular peduncle or slightly beyond this segment, 0.39–0.48 (median 0.46) times as long as carapace. Rostrum formula 0–2 + 9–13 / 2– 5. Inferior orbital angle fused with a strong antennal spine. Pterygostomian angle blunt. Eyes well developed with cornea globular. Antennular peduncle 0.50–0.62 (median 0.56) times as long as carapace, first segment 2.55–2.88 (median 2.65) times as long as second segment, second segment 1.46–1.73 (median 1.61) times length of third segment. Stylocerite reaching to 0.84–0.93 (median 0.88) times of basal segment of antennular peduncle. Scaphocerite ( Figure 2C ) 2.52–3.30 (median 2.82) times as long as wide.

Abdominal somites, telson and uropods. Sixth abdominal somite 0.43–0.51 (median 0.46) times length of carapace, 1.25–1.45 (median 1.40) times as long as fifth somite, 0.79–0.84 (median 0.80) times as long as telson. Telson ( Figures 4 E,F ) 2.72–3.01 (median 2.83) times as long as proximally wide, distal margin convex with median projection, with 4–6 pairs of dorsal spinules and one pair of dorsolateral spinules; distal end with 2 lateral spines and 7–12 long, feathered setae overreaching lateral spines. Preanal carina ( Figure 4D ) rounded, armed with a tooth. Uropodal diaeresis ( Figure 4C ) with 14–18 movable spinules, outermost ones shorter than lateral angle.

Mouthparts and branchiae. Incisor process of mandible ending in irregular teeth, molar process truncated ( Figure 2D ). Lower lacinia of maxillula broadly rounded, upper lacinia elongate, with numerous distinct teeth on inner margin, palp slender with few simple setae at tip ( Figure 2E ). Upper endites of maxilla subdivided, palp slender, scaphognathite tapering posteriorly, fringed with long, curved setae at posterior margin ( Figure 2F ). Palp of first maxilliped ending in a stout semi-triangular extension ( Figure 2G ). Podobranch on second maxilliped well developed. ( Figure 2H ). Third maxilliped with two arthrobranches, ultimate segment distinctly shorter than penultimate segment ( Figure 3A ). First pereiopod with an arthrobranch. Pleurobranchs present on all pereiopods. Well-developed epipods (with hooks on distal end) present on third maxilliped and first 4 pereiopods.

Pereiopods. Chela and carpus of first pereiopod stouter and broader than chela and carpus of second pereiopod ( Figures 3B,C ); chela of first pereiopod 1.71–2.24 (median 1.96) times as long as wide, 1.43–1.56 (median 1.50) times length of carpus; tips of fingers rounded, without hooks; dactylus 0.87–1.14 (median1.99) times as long as palm; carpus distinctly excavated distally 1.22–1.67 (median 1.43) times as long as wide, 0.78–0.86 (median 0.82) times length of merus. Merus 2.18–3.10 (median 2.65) times as long as wide, longer than ischium. Chela of second pereiopod 1.91–2.57 (median 2.30) times as long as wide, 0.92–1.01 (median 0.95) times length of carpus; tips of fingers rounded, without hooks, dactylus 1.18–1.29 (median 1.23) times as long as palm; carpus 2.83–4.33 (median 3.70) times as long as wide, 0.85–0.96 (median 0.95) times as long as merus; merus 3.81–4.89 (median 4.33) times as long as wide, longer than ischium. Third pereiopod moderately strong ( Figures 3 D–F ), sexual dimorphic, dactylus 2.15–2.62 (median 2.37) times as long as wide (terminal claw and spines on flexor margin included), terminating in one large claw with 5 or 6 accessory spines on flexor margin; propodus short, with numerous spinules on posterior margin in males, with few spinules in females, 3.60–7.88 (median 6.38) times as long as wide, 3.25–3.52 (median 3.52) times as long as dactylus; carpus 3.06–3.91 (median 3.40) times as long as wide, 0.67–0.75 (median 0.70) times as long as propodus, 0.52–0.60 (median 0.55) times as long as merus; merus inflated, 3.19–4.38 (median 3.75) times as long as wide, 1.68–1.93 (median 1.80) times as long as carpus, bearing 4–5 strong, apressed movable spinules on posterior margin of outer surface. Ischium without spinule. Fifth pereiopod slender ( Figures 3 H,I ), dactylus 2.32–2.73 (median 2.52) times as long as wide (terminal claw and spines on flexor margin included), terminating in one large claw with 14 spinules on flexor margin; propodus 7.56– 11.35 (median 9.46) times as long as wide, 3.72–3.78 (median 3.75) times length of dactylus, carpus 2.75–4.00 (median 3.38) times as long as wide, 0.62–0.64 (median 0.63) times as long as propodus, 0.69–0.77 (median 0.73) times as long as merus; merus 3.28–5.13 (median 4.30) times as long as wide, 1.30–1.44 (median 1.37) times length of carpus, bearing 2–4 movable spinules on posterior margin of outer surface. Ischium without spinule.

Pleopods. Endopod of male first pleopod ( Figure 4A ) trapezoid, widened distally, 1.60–1.64 times as long as distal width (n=2), 0.81–0.90 times as long as exopod, distal margin with long spines, inner margin with few short spinules, appendix interna arising from distal ¼ of endopod, not overreaching distal margin of endopod. Appendix masculina on male second pleopod ( Figure 4B ) club-shaped, longer than endopod in adult males (7.47–8.74 (n=2) times as long as wide, 1.15–1.37 times as long as endopod), armed with a row of strong spines on inner margin and a bottle-brush like spinulation on distal 1/3, appendix interna arising from about 0.4 times length of appendix masculina.

Reproductive biology. Ovigerous females with numerous (1600 eggs counted in one specimen) small eggs; size of undeveloped eggs (without eyes) 0.23–0.24 x 0.37–0.39 mm.

Size. Postorbital carapace length 3.0– 8.8 mm.

Colour pattern. Colours ( Colour plate 1 ) vary and tend to match the substrate the shrimp lives on. The body is either black or brownish with numerous small red dots. In some specimens, carapace and abdomen show blackish and whitish transversal bands. The coloration is lost on preserved animals.

Habitat. All specimens were collected in the lower course of rivers (altitude 5–53 m), in running waters.

Distribution. For the time being, this new genus was found only in South Africa and in the eastern rivers of Madagascar. The small and numerous eggs indicate a prolonged larval development and the habitat (lower course of rivers) suggests the possibility of a wider distribution range in Madagascar as well as in other rivers draining to the Indian Ocean.

Molecular results. Six specimens were successfully sequenced at 16S gene ( Table 2 ). Sequences included 512 bp containing only 2 variable sites. After alignment with atyid sequences from von Rintelen et al. (2012), the 16S dataset of 580 bp included 371 variable sites, of which 317 were phylogenetically informative. After removal of ambiguous blocks, 481 bp of sequence remained to be used in phylogenetic analyses (82% of the original 580 positions), of which 289 bp were variable and 254 bp phylogenetically informative.

Elephantis natalensis comb. nov. sequences were genetically well differentiated from all other sequences included in the analyses. Pairwise K2P genetic distances between E. natalensis and atyid sequences ranged from 9.8 to 33%. Genetic distances between E. natalensis and Caridina -like sequences ranged from 9.8 to 18.7%. Similar genetic distances were obtained when comparing E. natalensis sequences with Atya -like sequences. In the molecular analysis E. natalensis is placed within Caridina sensu lato. Indeed the genus Caridina was considered as polyphyletic in several molecular studies ( Page et al., 2007; von Rintelen et al., 2008, 2012).

Tree topology derived from both NJ and ML analyses using published 16S sequences of atyid freshwater shrimps ( von Rintelen et al. 2012) plus newly produced 16S sequences of E. natalensis (present study) were similar to the 16S topology produced by von Rintelen et al. (2012) ( Fig. 5 ). Therefore we will present only the results obtained for E. natalensis from the ML analysis. The group including Atya -like shrimps and Caridina -like shrimps ( von Rintelen et al, 2012) was found monophyletic (B (NJ analysis) = 79%; B (ML analysis) = 71%). Elephantis natalensis sequences formed a divergent group highly supported by bootstraps analyses (B (NJ analysis) = 100%; B (ML analysis) = 99%).

Figures

COLOUR PLATE 1. Live coloration of Elephantis natalensis comb. nov. A= lateral view (G. Marquet); B= dorsal view (E. Feunteun).

FIGURE 2. Elephantis natalensis comb. nov., male (cl 4.26 mm) (coll. WK 54-11-2): A. cephalothorax, B. antennular peduncle, C. scaphocerite, D. mandible, E. maxillula, F. maxilla, G. first maxilliped, H. second maxilliped.

FIGURE 3. Elephantis natalensis comb. nov., male (cl 4.26 mm) (coll. WK 54-11-2): A. third maxilliped, B. first pereiopod, C. second pereiopod, D. third pereiopod, E. dactylus of third pereiopod, F. inner margin of third pereiopod of male. Female (cl 5.87 mm) (coll. WK 54-11-4): G. inner margin of third pereiopod of female, H. fifth pereiopod, I. dactylus of fifth pereiopod.

FIGURE 4. Elephantis natalensis comb. nov., male (cl 4.26 mm) (coll. WK 54-11-2): A. first pleopod of male, B. second pleopod of male, C. uropodal diaeresis, D. preanal carina, E. telson, F. distal end of telson.

FIGURE 5. Maximum Likelihood tree of atyids, including Elephantis natalensis comb. nov. based on the mitochondrial 16S dataset produced by von Rintenlen et al. (2012). Numbers on branches are from top, NJ and ML bootstrap values. Elephantis natalensis comb. nov. individuals are indicated in red.