Global biodiversity and phylogenetic evaluation of remipedia (crustacea)

Abstract

Remipedia is one of the most recently discovered classes of crustaceans, first described in 1981 from anchialine caves in the Bahamas Archipelago. The class is divided into the order Enantiopoda, represented by two fossil species, and Nectiopoda, which contains all known extant remipedes. Since their discovery, the number of nectiopodan species has increased to 24, half of which were described during the last decade. Nectiopoda exhibit a disjunct global distribution pattern, with the highest abundance and diversity in the Caribbean region, and isolated species in the Canary Islands and in Western Australia. Our review of Remipedia provides an overview of their ecological characteristics, including a detailed list of all anchialine marine caves, from which species have been recorded. We discuss alternative hypotheses of the phylogenetic position of Remipedia within Arthropoda, and present first results of an ongoing molecular-phylogenetic analysis that do not support the monophyly of several nectiopodan taxa. We believe that a taxonomic revision of Remipedia is absolutely essential, and that a comprehensive revision should include a reappraisal of the fossil record.

Figure 1. Habitus of a remipede.

Photograph of a living specimen of Speleonectes tanumekes from the Exuma Cays, Bahamas; asterisks indicate the location of female and male gonopores on trunk somites seven and 14, respectively (Photograph courtesy of J. van der Ham).

Figure 2. 50% majority-rule consensus tree of Remipedia and outgroup taxa based on a Bayesian analysis of CO1 sequence data.

Bayesian posterior probability values of clades are noted at the nodes of the tree. Remipede lineages currently assigned to the family Speleonectidae and Godzilliidae are indicated in blue and red, respectively. Outgroup lineages are indicated in black.

Figure 3. Holotype of Tesnusocaris goldichi (Remipedia, Enantiopoda).

The holotype (catalogue number USNM 124173a) has a length of approximately 77 cm; it was collected by S. S. Goldich (1939) in the Tesnus Formation (Pennsylvanian), West of Rough Creek, Dove Mountain Quadrangle, Brewster County, Texas.

Figure 4. Distributional records of nectiopodan remipedes.

Included in the list are all caves with confirmed occurrence of Remipedia. Type localities for species are indicated by (T) and confirmed additional records by a black dots. Records of Remipedia, which are morphologically similar to the respective species, but either need to be confirmed or may represent cryptic species, are referred to by triangles. Abbreviations: A: Australia; DR: Dominican Republic; ES: Spain; TC: Turks and Caicos; B. H.: Blue Hole; Rd.: Road; Cp.: Cape; P.: Peninsula.

Figure 5. Camera lucida drawing of specimen SDNHM 28852.

Collected by Emerson and Schram (1985) at the type locality of Tesnusocaris goldichi (see Figure 3).

Figure 6. Global distribution of anchialine caves.

Epicontinental anchialine cave systems are indicated by dots and anchialine waters on isolated seamount islands by triangles. Remipedia show a disjunct global distribution pattern, with all known species restricted to epicontinental anchialine caves. The majority of remipede species inhabit the larger Caribbean region (A), including the Yucatán Peninsula, Cuba, the Dominican Republic, the Turks and Caicos Islands and the Bahamas. Isolated species occur in caves on the Canarian Island of Lanzarote (B) and in Western Australia (C). Map (modified) with kind permission of Demis (www.demis.nl).

Figure 7. Map of the larger Caribbean region.

Names of islands and regions, where Remipedia occur are indicated. For detailed information on the distribution of Remipedia see Figure 4. Map (modified) with kind permission of Demis (www.demis.nl).