Daphnia (Ctenodaphnia)

Damme, Kay Van, 2016, Endemism and long distance dispersal in the waterfleas of Easter Island, Zootaxa 4154 (3), pp. 251-272 : 265-266

Daphnia (Ctenodaphnia) sp.

( Figure 6 )

Material. Images provided by Cañellas-Boltà ( Fig. 6 ); see Cañellas-Boltà et al. (2012). Unidentified record from Rano Raraku Lake sediment core, Easter Island, in Cañellas-Boltà et al. (2012: Fig. 3 n, Cladocera ephippia IBB- 98).

Notes. Unknown Ctenodaphnia species. Small ephippium, length about 650µm, width 250µm ( Fig. 6 ). Major axis of embryo chambers in ephippium (dark pigmented areas) forming not more than a 45° angle with the dorsal ephippial margin. Caudal needle present. Late Pleistocene-Early Holocene (16-8 cal ka BP) subfossil ephippia in Rano Raraku crater lake, Easter Island ( Cañellas-Boltà et al. 2012), likely extinct.

Comments. The two observations of single specimens when re-examining the samples, should not be seen as records and could be potential contaminants. These include a specimen of the C. sphaericus- group and an ephippium of Daphnia (Daphnia) . However, the possibility should not be excluded that more than one cladoceran taxon may occur, or have occurred here (as remains in sediments or in current waterbodies). C. sphaericus , for example, has been mentioned from other Pacific Oceanic Islands (Hawaii; Brehm 1937). A brief update on the microcrustaceans of Easter Island since the first survey by Dumont & Martens (1996), is included in Table 2.

Species Remarks

Cladocera

Daphnia (Ctenodaphnia) sp. Species unknown, extinct; only fossil ephippia1,2 Ovalona pascua sp. nov. Likely endemic, with closest affinities to Neotropical taxa1 Copepoda

Paracyclops chiltoni (Fischer, 1853) Cosmopolitan 3,4

Ostracoda

Cypretta seurati Gauthier, 1929 Circumtropical , circum-mediterranean3,4 Heterocypris incongruens (Ramdohr, 1808) Cosmopolitan 3,4

Sarscypridopsis sp. Subantarctic connection suggested3,4,5 yet detailed affinities unknown. Two, potentially three, new endemic species of this genus have been recently suggested from other Pacific Islands6

Figures

FIGURE 3. Ovalona pascua sp. nov. Adult parthenogenetic female, loc. pool North of Hanga Roa village, West of Easter Island, Chile, coll. by H. J. Dumont and K. Martens, 18. VIII. 1990. Thoracic structures. A, first Limb / P 1, ODL and IDL omitted. B, outer (ODL) and inner distal lobe (IDL). C, second limb / P 2. D – H, third limb / P 3 exopodite (D – E) and endite (F – H). I – K, fourth Limb / P 4 exopodite (I) and endite (J) with flaming torch setae (K). L – M. fifth limb exopodite (L) and inner portion without setules (M).

FIGURE 6. Late Pleistocene-Early Holocene Daphnia ephippia from Easter Island. Daphnia (Ctenodaphnia) sp. Unidentified fossil ephippium from Rano Raraku Lake (IBB- 98 in Cañellas-Boltà et al. 2012; images by N. Cañellas-Boltà, with permission), same ephippium, different illumination. Scale bar 0.5 mm.