Old World-New World differentiation of so-called “circumtropical” taxa: the case of rare genus Grimaldina Richard, 1892 (Branchiopoda: Cladocera: Macrothricidae)

Abstract

The Cladocera (Crustacea: Branchiopoda) is an ancient group of predominantly freshwater microscopic invertebrates. During the last three decades a cosmopolitanism paradigm in the biogeography of these animals is gradually being replaced by a concept of continental endemism. Current morphological and molecular genetic data demonstrate that many Holarctic taxa actually represent sibling species groups with localized distributions. Similarly, some circumtropical cladocerans are poorly studied and must be considered using the same concept. Grimaldina Richard, 1892 (Cladocera: Macrothricidae) is an example of such taxon. Since the first description time, this genus was considered as monotypic, including a single species Grimaldina brazzai Richard, 1892, distributed in tropical regions all around the World, but being rare everywhere across its distribution range. We carefully examined specimens of Grimaldina from different tropical water bodies, redescribed morphology of G. brazzai based on new material from Africa, supplemented the genus diagnosis, and demonstrated that G. brazzai is limited to the Old World (Africa and Asia). Population from New World tropical regions are described as Grimaldina freyi sp. nov., based on material from the collection of Prof. Dr David G. Frey and named in his honor. It clearly differs from G. brazzai in: (1) antenna II with longest endopod seta bearing more densely set spinulae and (2) limb V medial portion with a smaller ratio of seta 2 to seta 3. These traits in G. freyi sp. nov. are presumably plesiomorphic, while G. brazzai has more apomorphies. Divergence between American (G. freyi sp. nov.) and Old World (G. brazzai) populations could be related to the ancient vicariant events (Gondwana breakup) or to more recent trans-continental dispersal events.

Cladocera (Crustacea, Branchiopoda) of a temporary shallow pond from northern Colombia

“…ODL and IDL of trunk limb I with one and three setae respectively (Fig. 6A), trunks limb II-V undistinguishable from description of Neretina & Kotov, 2017, the latter one ( Fig. 6B) with round and ovoid preepiodite and epipodite respectively, the outer exopod with a setulated seta reaching beyond the preepipodite (Fig.…”

“…13D-E) vs. 4 in G. brazzai (Neretina & Kotov 2017, figs 6D-E), (3) the setullated seta on outer exopod of trunk limb V goes beyond the preepipodte in G. freyi (Fig. 6B, Neretina & Kotov 2017, fig 13C) whereas in G. brazzai the setullated seta reaches the half of preepipodite (Neretina & Kotov 2017, fig 6C); (4) the basal segment of antenna II of G. freyi male bears one long seta (Fig. 5E) vs. 3 setae in G. brazzai (Kořínek 1984, plate XXVI, fig 6); (5) the IDL of trunk limb I of G. freyi male bear 3 setae vs. 1 seta in G. brazzai (Kořínek 1984, plate XXVI, fig.…”

“…In our study it was collected in October and November Genus Grimaldina Richard, 1892 12. Grimaldina freyi Neretina and Kotov, 2017 Synonymy: Grimaldina brazzai Richard in Sars 1901: . 28-31, pl.…”

“…Body length of female is between 700 -714 μm, and male is 546 μm This genus is composed by two species: G. brazzai Richard, 1892 and G. freyi, which are superficially similar; nevertheless they can be separated by: (1) (2) the ratio of seta 2/seta 3 length on the inner distal portion of exopod of the fifth thoracic limb is about 2 in G. freyi (Fig. 6C, Neretina & Kotov 2017 figs. 13D-E) vs. 4 in G. brazzai (Neretina & Kotov 2017, figs 6D-E), (3) the setullated seta on outer exopod of trunk limb V goes beyond the preepipodte in G. freyi (Fig.…”

“…6C, Neretina & Kotov 2017 figs. 13D-E) vs. 4 in G. brazzai (Neretina & Kotov 2017, figs 6D-E), (3) the setullated seta on outer exopod of trunk limb V goes beyond the preepipodte in G. freyi (Fig. 6B, Neretina & Kotov 2017, fig 13C) whereas in G. brazzai the setullated seta reaches the half of preepipodite (Neretina & Kotov 2017, fig 6C); (4) the basal segment of antenna II of G. freyi male bears one long seta (Fig.…”