Myodocopa (Crustacea: Ostracoda) as models for evolutionary studies of light and vision: multiple origins of bioluminescence and extreme sexual dimorphism

Abstract

Evolutionists often use phylogeny to examine independent evolutionary events in search of generality. Therefore, groups of organisms rich in such independent character transitions are particularly valuable for the study of evolution. With respect to eyes, vision, and light-related characters, one such group is Ostracoda (Crustacea). Phylogenies of ostracods, derived from DNA sequence data and morphological characters, are presented. These inferred relationships largely agree with previous assessments of ostracod phylogeny, with the exception of paraphyletic Philomedidae. Based on methods of character reconstruction using these inferred relationships, different groups of ostracods probably evolved both bioluminescence and extreme sexual dimorphism (females lack eyes, males have large eyes) multiple times. Furthermore, myodocopid ostracods may have evolved compound eyes independently of other arthropods. For these and other reasons, it is proposed that the Ostracoda are an exceptionally important group for studying the evolution of vision-and light-related characters.

On the phylogenetic position of Pseudophilomedinae within Sarsielloidea (Ostracoda, Myodocopida), with a description of one new Harbansus from Ningaloo Reef and redescription of H. paucichelatus from Yucatan

“…The results of our molecular phylogenetic analyses are in accordance with Oakley (2005), Oakley and Cunningham (2002), and Oakley et al (2012) indicating polyphyly of Philomedidae (Figs. 11, 12).…”

“…In the analysis of 18S, we have chosen three outgroup species, Vargula hilgendorfii Müller, 1986, V. tsujii Baker, 1977, andMelavargula japonica Poulsen, 1962, and only the first one in the molecular analysis of 28S. They belong to the superfamily Cypridinoidea, which has been shown in previous molecular analysis (Oakley 2005;Oakley and Cunningham 2002;Oakley et al 2012) to be the sister taxon of Sarsielloidea. Sequences for all three outgroup species, and another 30 highly similar sequences, all belonging to the superfamily Table 1).…”

“…Recent molecular studies (Oakley 2005;Oakley and Cunningham 2002;Oakley et al 2012) show that the phylogenetic relationships between the three Sarsielloidea families are not resolved, because some Sarsiellidae cluster with some Philomedidae, while other Philomedidae cluster with Rutidermatidae. However, these authors did not discuss morphological characters that may support these phylogenies, but instead call for better taxon sampling.…”

Life in the Underworld: Anchialine cave biology in the era of speleogenomics

“…Stygobitic ostracods are easily distinguishable from epigean representatives by the morphological differences associated with their adaptations to cave life (i.e., smaller size, lack of eyes and pigmentation, Danielopol, 1981). Even though anchialine ostracods have not received much attention from molecular biologists, genetic and genomic/transcriptomic studies of ostracods in other environments have been conducted with great success (Oakley & Cunningham, 2002;Oakley, 2005;Oakley et al, 2013). These studies provide a great basis on which to build upon future investigations of anchialine cave ostracods, which are likely to yield interesting evolutionary insights.…”

Preface: The phylogeny, fossil record and ecological diversity of ostracod crustaceans

“…Two papers in the present volume deal with ostracod eyes. Oakley (2005) uses phylogenies obtained by analyses of DNA sequence data and morphological characters to show that bioluminescence evolved separately in Myodocopida and Halocyprida, and argues that myodocopid compound eyes evolved independently of other arthropod groups. Tanaka (2005) presents a fascinating new study of podocopid median eyes using morphological and histological observations, showing that while they share a basic naupliar eye structure (three ocelli with highly reflective tapetal cells) with maxillopodan groups, ostracods are unique among Crustacea in using parts of the calcite carapace, to which the two lateral ocelli are attached, as refractive cuticular lenses; he further demonstrates that evolutionary changes in podocopid eyes can be tracked in the fossil record by paying attention to the detailed morphology of the eye tubercles and ocular sinuses of ostracod valves.…”