Ceriodaphnia Dana, 1853

Elías-Gutiérrez, Manuel, Jerónimo, Fernando Martínez, Ivanova, Natalia V., Valdez-Moreno, Martha & Hebert, Paul D. N., 2008, DNA barcodes for Cladocera and Copepoda from Mexico and Guatemala, highlights and new discoveries, Zootaxa 1839 (1), pp. 1-42 : 9-10

Genus Ceriodaphnia Dana, 1853

This genus is one of the most confusing among the Daphniidae . Some species, such as the cornuta - rigaudi complex show morphological diversity, and have broad distributions. We found several morphs belonging to this complex showing deep barcode divergence, but any effort to clarify their relationship to named species will demand barcode and morphological analysis of topotype material. In this regard, we note that C. cornuta was originally described from Australia ( Sars 1885) while C. rigaudi Richard was described from Tonkin ( Vietnam) by Richard (1894b).

One species in our collections showing deep barcode divergence is an unnamed taxon ( Ceriodaphnia sp. ) from intermittent pools in the northern semi-desert regions. It possesses long, thick hairs emerging from the valves and a minute but constant rostral projection. Three more barcode lineages were all identified as Ceriodaphnia cf. rigaudi (named C. cf. rigaudi 1 to 3), due to their lack of any additional projection from the head (except the rostral protuberance) and their rounded fornices, ( C. cornuta invariably possesses spines on its fornices). Figure 1.2 shows that the first cluster is narrowly distributed in the semi-desert regions of northern Mexico, while the second one is restricted to the south, near the coast in the Gulf of Mexico to Guatemala. In this cluster, the morph collected near Lachua Lake ( Guatemala, Alta Verapaz) has a slightly shorter rostrum and lacks hair, while other forms are haired, similar to the variability observed by Berner (1985). The third lineage of C. rigaudi Richard was only found in the Yucatan Peninsula, but because only one specimen gave a good sequence, it is premature to draw any final conclusion. Although all three phenotypes show slight morphological differences from C. rigaudi s. str., there is difficulty in identifying morphological traits that discriminate them because of the high variability within each taxon.

In the northern semi-desert region, we found another species closely related to C. acanthina Ross , described from Manitoba ( Canada), sharing its strong reticulation of the valves and short spinules. Because true C. acanthina , according to several authors, is restricted to the north of the continent, we identify our isolate as C. cf. acanthina .

Another species, closely related to C. laticaudata Müller described from Denmark, was found in ponds on the central plateau in the highlands of Mexico. Despite the geographic separation, our populations shared the projected dorsum of the postabdomen before the anus typical of this species. Similar forms have been found elsewhere, including South America ( Paggi 1986). This form was placed far from another C. cf. laticaudata 1, with a much wider projection from the dorsum of the postabdomen, and with postabdominal claws that are of a more constant length. C. cf. laticaudata 1 was only found in one locality in a semi-desert region in Cuatro Ciénegas. It is important to note that ponds and lakes from this valley are rich in endemics ranging from invertebrates to vertebrates (i.e. Moline et al. 2004; Trapani 2003).

Finally, a highly variable and widely distributed taxon named C. cf. dubia was found from the north of the continent (Pinehurst Lake, Ontario, Canada) to Guatemala (Peten Lake) ( Fig. 1.3 ). Limp & Fernando (1978) named the taxon inhabiting Pinehurst Lake as C. quadrangula (O.F. Müller) , but according to Berner (1992), it is restricted to Newfoundland. In general terms, our Ceriodaphnia shows a different morphology than C. dubia Richard s. str. (sensu Berner 1992), but this material should be compared with topotypes of this species which was originally described from Sumatra by Richard (1894a).

Figures

FIGURE 1. 1.1 Sampling localities for all taxa; 1.2 Distribution of C. rigaudi complex: ⊕ C. cf. rigaudi 1, ∧ C. cf. rigaudi 2, ′ C. cf. rigaudi 3; 1.3 Distribution of C. cf. dubia; 1.4 Moina micrura group: M. cf. micrura 1, M. cf. micrura 2, ® M. cf. micrura 3; 1.5 Arctodiaptomus dorsalis: ℜ A. cf. dorsalis, ρA. dorsalis, A. cf. dorsalis 1 from Lachua Lake, ′ A. cf. dorsalis 2; 1.6 Mastigodiaptomus albuquerquensis: ♦M. albuquerquensis, ⊕ M. cf. albuquerquensis.