Genus level molecular phylogeny of Aegisthidae Gisbrecht, 1893 (Copepoda: Harpacticoida) reveals morphological adaptations to deep-sea and plagic habitats.

BACKGROUND: The family Aegisthidae is known as typical component of deep-sea hyperbenthic waters that gradually colonized other marine environments. The phylogenetic relationships within this family have been examined here including hyperbenthic, planktonic, benthic forms and two associated Aegisthidae species. RESULTS: Ninety four specimens belong to 14 genera were studied using 18S and 28S rRNA and COI mtDNA. Bayesian analysis supports the monophyly of 10 genera whereas Andromastax, Jamstecia, Nudivorax and Aegisthus revealed to be paraphyletic. The first offshoot of the phylogenetic tree is a clade consists of the undescribed genus Aegisthidae gen.1 sister to the two monophyletic genera Cerviniella and Hase, whereas the other Cerviniinae members (represented by Cervinia and Expansicervinia) assemble a monophylum, sister to the hyperbenthic and planktonic aegisthid genera, resulting in the paraphyly of the subfamily Cerviniinae. Hence, we defined the new subfamily Cerviniellinae subfam. nov. encompassing the three benthic genera Cerviniella, Hase and Eucanuella. The subfamily Cerviniinae has been re-defined to include Cervinia, Expansicervinia and Paracerviniella. Members of the subfamily Pontostratiotinae were clustered into two clades, one consists of the genus Stratiopontotes sister to an undescribed genus + Cerviniopsis and Siphonis. The second contains Pontostratiotes sister to the members of the planktonic subfamily Aegisthinae, resulting in the paraphyly of the Pontostratiotinae. Therefore, the Pontostratiotinae has been re-defined to include only members of the genus Pontostratiotes; whereas the subfamily Cerviniopseinae has been re-erected and re-defined containing Stratiopontotes, Cerviniopsis, Siphonis, Aegisthidae gen. 2, Herdmaniopsis, Hemicervinia and Tonpostratiotes. Within this subfamily, the associated Siphonis clusters as sister to the Cerviniopsis represents an example of convergent evolution in which the possession of a stylet-like mandible and an oral cone reminiscent of the Siphonostomatoida. The planktonic Aegisthus, Andromastax, Jamstecia, Nudivorax and Scabrantenna confirm the monophylom Aegisthinae, sister to the Pontostratiotinae. CONCLUSIONS: Our DNA based phylogeny reveals the deep-sea origin of Aegisthidae by placing benthic Aegisthidae gen.1 and Cerviniellinae subfam. nov. as the most basal lineages. Secondary adaptations to hyperbenthic and planktonic realms, as well as associated lifestyle were discovered here by the derived positions of Pontostratiotinae, Aegisthinae and Siphonis respectively.

Molecular evidence for the retention of the Thaumatopsyllidae in the order Cyclopoida (Copepoda) and establishment of four suborders and two families within the Cyclopoida.

The classification of the Thaumatopsyllidae within the Copepoda has been an issue of ongoing discussion since the discovery of Thaumatopsyllus paradoxus G.O. Sars, 1913 from the Norwegian coast. The family has been formally placed in the Monstrilloida, the Cyclopoida and even in its own order, the Thaumatopsylloida, based on different morphological criteria. We examined for the first time, the phylogenetic position of the Thaumatopsyllidae using gene sequences of 28S and 18S rRNA, as well as COI mtDNA, obtained from two thaumatopsyllid species occurring off the coast of southern California. We also fortuitously explored the phylogenetic relationships of the Cyclopoida in more detail than Khodami et al. (2017) by including a wider sample of key families such as the Erebonasteridae and Gisellinidae. Both Maximum Likelihood and Bayesian analyses revealed the Thaumatopsyllidae is nested in the Cyclopoida and is related to the marine Speleoithonidae. In addition, 16 families of the Cyclopoida are supported to be monophyletic, but surprisingly, the Cyclopidae is paraphyletic. The Cyclopicinidae is the first monophyletic offshoot of the cyclopoid tree, followed by two derived clades. The first clade contains a monophylum consisting of the Schminkepinellidae + Giselinidae which is sister to a clade including the monophyletic Erebonasteridae and all other poecilostome families. The second clade is divided into two main, well-supported family clusters. One includes the Cyclopidae encompassing two subfamilies (Eucylopinae and Cyclopinae), but unexpectedly the parasitic Lernaeidae cluster as a sister-group to the brackish water Halicyclops (subfamily Halicyclopinae) and the Euryteinae is the sister to all the rest of Cyclopidae s. l., making the Cyclopidae paraphyletic. To resolve this conundrum, we erected two families, Euryteidae and Halicyclopidae. The Cyclopidae s. str. retains the subfamilies Eucyclopinae and Cyclopinae, although our phylogeny does not support the reciprocal monophyly of these subfamilies. Our results support the gradual invasion of fresh water by the four families in this cluster. The highly supported monophyletic marine Euryteidae is the first offshoot followed by the brackish-water, free-living Halicyclopidae and the freshwater, parasitic Lernaeidae. The Cyclopidae fulfilled the colonization of freshwater bodies. The other clade of families comprises 12 monophyletic families recovered by our analysis, including the Pterinopsyllidae (at first offshoot), the Smirnovipinidae sister to the Hemicyclopinidae + Psammocyclopinidae, the Thaumatopsyllidae + Speleoithonidae, an undescribed family sister to the Archinotodelphyidae + Notodelphyidae and the Cyclopinidae sister to the Oithonidae + Cyclopettidae. We propose suborder ranks for each of the four main phylogenetic subdivisions of the Cyclopoida. These are named Cyclopicinida, Ergasilida, Cyclopida and Oithonida after the type genus of the oldest described family in the respective group.

Copepods and ostracods associated with bromeliads in the Yucatán Peninsula, Mexico.

A substantial fraction of the freshwater available in the Neotropical forests is enclosed within the rosettes of bromeliads that form small aquatic islands within a terrestrial landscape. These aquatic oases provide shelter, water, nutrients and resting of aggregation sites for several aquatic organisms, among them crustaceans. However, in comparison with the multitude of studies on open aquatic systems, our knowledge on crustaceans inhabiting semi-terrestrial habitats and phytotelmata is limited and their presence in such environments is poorly understood. The present study was carried out in two natural protected areas of the Yucatán Peninsula aiming to understand the diversity and dispersal strategies of crustaceans living in bromeliads. Sediment and water contained in four species of bromeliads have been collected in order to understand the diversity and dispersal strategies of crustaceans living in such habitats. From a total of 238 bromeliads surveyed, 55% were colonized by crustaceans. Sixteen copepod, three ostracod and one branchiopod species were recorded during this study, however only seven species are considered as true bromeliad inhabitants. Different degrees of association between crustaceans and bromeliad species were assessed with an indicator species analysis, where significant associations were found for all crustaceans. We found significant differences between bromeliad species and reserves and their associated fauna. In order to analyze the genetic diversity of this fauna, we sequenced several individuals of each species with two genetic markers (18S rRNA and COI mtDNA). Bayesian analyses and the Generalized Mixed Yule Coalescent method (GMYC), delimited 7 well supported species. A comparison of the dispersal strategies used by different species, including passive dispersal, phoretic behavior and active dispersal, is included. This study stresses the need of studying meiofauna of phytotelms, which could be used as an indicator of local diversity in Neotropical forests.

Revision of the Remaneicaris argentina-group (Copepoda, Harpacticoida, Parastenocarididae): supplementary description of species, and description of the first semi-terrestrial Remaneicaris from the tropical forest of Southeast Mexico.

Remaneicaris is a species-rich Neotropical monophyletic group, easily recognized by the synapomorphic position of the outer seta of the third exopodite of leg 4, localized at 2/3 of the outer margin. The genus, comprising 35 species in five monophyletic groups, plus R. ignotus and R. meyerabichi, retains an unusual set of plesiomorphic characters. Herein we supplement the descriptions of the species belonging to the Remaneicaris argentina-group, and describe a new species from the tropical forest of Southeast Mexico. The present study extends the geographic distribution of the genus, with the northernmost record until now being from El Salvador. The genus having hitherto been known from interstitial groundwater habitats, this is its first record in epigean semi-terrestrial habitats. Remaneicaris siankaan sp. nov. was found in phytotelmata (bromeliads), leaf litter, moist soil, permanent ponds (known locally as "aguadas"), and temporal and permanent wetlands (savannahs). The new species can be easily characterized by its finely pitted cuticle, the ε (epsilon)-shaped thumb of the male P3 and the bifid accessory spine with distal hyaline inner tip, which precedes the thumb. A new method for the 3D reconstruction of microcrustaceans is described.

On Kiefer's American Eucyclops (Copepoda, Eucyclopinae): redescriptions and comments on the historical records of E. delachauxi, E. prionophorus, E. bondi and E. leptacanthus.

The freshwater copepod genus Eucyclops contains many supposedly cosmopolitan species whose taxonomic status is still under discussion; some of them represent species complexes. The problem is not exclusive to these widespread species; there are several American Eucyclops needing a taxonomic re-evaluation. Based on the examination of Friedrich Kiefer's collection in Karlsruhe, Germany, the type specimens of four American species of Eucyclops (E. delachauxi (Kiefer, 1926), E. prionophorus Kiefer, 1931, E. bondi Kiefer, 1934, E. leptacanthus Kiefer, 1956) were re-examined and redescribed using upgraded descriptive standards. Kiefer's translated descriptions and unpublished original drawings of these species are also presented. Characters like the ornamentation of the antennal basis, ornamentation of intercoxal sclerites of the swimming legs 1-4, length of basipodal seta of leg 1, ornamentation of caudal rami, the presence of aesthetascs and modified setae on the antennules in male, and the structure of the male sixth leg are compared herein to aid a more accurate separation of these American species. A revision of the American records of these species confirms that some are likely to refer to undescribed species. Overall, the diversity of the American Eucyclops appears to be underestimated and certainly deserves further study.

A new species of Metacyclops Kiefer, 1927 (Copepoda, Cyclopidae, Cyclopinae) from the Chihuahuan desert, northern Mexico.

A new species of the freshwater cyclopoid copepod genus Metacyclops Kiefer, 1927 is described from a single pond in northern Mexico, within the binational area known as the Chihuahuan Desert. This species belongs to a group of Metacyclops species with a 3443 spine formula of swimming legs. It is morphologically similar to Metacyclops lusitanus Lindberg, 1961 but differs from this and other congeners by having a unique combination of characters, including a caudal rami length/width proportion of 3.5-3.8, a innermost terminal seta slightly longer than the outermost terminal seta, intercoxal sclerites of legs 1-4 naked, a strong apical spine of the second endopodal segment of leg 1 and one row of 6-8 small spinules at the insertion of this spine. The finding of this species represents also the first record of the genus in Mexico and the third in North America, where only two other species, Metacyclops gracilis (Lilljeborg, 1853)and Metacyclops cushae Reid, 1991 have been hitherto reported. This is also the first continental record of a species of Metacyclops from an arid environment in the Americas. This species appears to be endemic to the Chihuahuan Desert, thus emphasizing the high endemicity of this area.