Triops

Abstract: We used three molecular markers to investigate populations of Triops granarius from a study area in western Morocco that had a north-south span of approx. 434 km, the most distant populations situated at more than 470 km distance from each other. Previous studies had already investigated two Triops granarius populations from this region and revealed their affiliation to the major phylogenetic lineage that includes Triops cancriformis. By contrast, based on the geographic position of the type locality and the morphology of the type, Triops granarius s.s. likely belongs to a clade that forms the sister group to American and Australian Triops, i.e. including Triops longicaudatus and Triops australiensis. In the present study a second, hitherto unknown phylogenetic lineage was discovered among Moroccan populations of Triops granarius s.l. Our phylogenetic analyses show that both Moroccan lineages of Triops granarius s.l. represent a pair of genetically and morphologically well differentiated sister species that should be separated from Triops granarius. We therefore formally describe them as two new species, Triops maximus sp. nov. and Triops multifidus sp. nov. The early larval stages of both species show a peculiar morphology with 10 to 15 setae on the exopodite of the 2nd antenna. The number of these setae was generally thought to span five to seven in Notostraca. Despite the fact that the antennal setae form a central part of the main locomotory organ in early instars, we found their number to vary by up to two between body-sides of single individuals.

Abstract: We present an updated taxonomic account of a few of the large branchiopod species present in the collections of the Yale Peabody Museum of Natural History. Our study shows that the Artemia species in the collections is not Artemia salina given the presence of spines at the base of the penis and its frontal knob morphology. This population cannot be assigned to any particular species due to lack of comparative material of other Artemia species and therefore, now reduces the authentic distribution record of Artemia salina to just one in the subcontinent. The morphology of eggs taken from the Streptocephalus longimanus allotype is distinct from what has been described later by having lower number of polygons on the egg surface. The gross morphology of the Triops cancriformis from Punjab, Pakistan resembles those of the Kashmir population from India except for its larger size. Based on the morphological comparison, we show that Eocyzicus deterrana is indeed synonymous to E. hutchinsoni. This work further changes the total species tally of large branchiopods from 44 of the Indian subcontinent to 45.

Abstract: Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats worldwide. Often cited as prime examples of evolutionary stasis, surviving representatives closely resemble fossils older than 200 mya, suggestive of an ancient origin. Despite significant interest in the group as ‘living fossils’ the taxonomy of surviving taxa is still under debate and both the phylogenetic relationships among different lineages and the timing of diversification remain unclear. We constructed a molecular phylogeny of the Notostraca using model based phylogenetic methods. Our analyses supported the monophyly of the two genera Triops and Lepidurus, although for Triops support was weak. Results also revealed high levels of cryptic diversity as well as a peculiar biogeographic link between Australia and North America presumably mediated by historic long distance dispersal. We concluded that, although some present day tadpole shrimp species closely resemble fossil specimens as old as 250 mya, no molecular support was found for an ancient (pre) Mesozoic radiation. Instead, living tadpole shrimp are most likely the result of a relatively recent radiation in the Cenozoic era and close resemblances between recent and fossil taxa are probably the result of the highly conserved general morphology in this group and of homoplasy.