Thomas M. Iliffe

Pancrustacean Phylogeny in the Light of New Phylogenomic Data: Support for Remipedia as the Possible Sister Group of Hexapoda

Remipedes are a small and enigmatic group of crustaceans, first described only 30 years ago. Analyses of both morphological and molecular data have recently suggested a close relationship between Remipedia and Hexapoda. If true, the remipedes occupy an important position in pancrustacean evolution and may be pivotal for understanding the evolutionary history of crustaceans and hexapods. However, it is important to test this hypothesis using new data and new types of analytical approaches. Here, we assembled a phylogenomic data set of 131 taxa, incorporating newly generated 454 expressed sequence tag (EST) data from six species of crustaceans, representing five lineages (Remipedia, Laevicaudata, Spinicaudata, Ostracoda, and Malacostraca). This data set includes all crustacean species for which EST data are available (46 species), and our largest alignment encompasses 866,479 amino acid positions and 1,886 genes. A series of phylogenomic analyses was performed to evaluate pancrustacean relationships. We significantly improved the quality of our data for predicting putative orthologous genes and for generating data subsets by matrix reduction procedures, thereby improving the signal to noise ratio in the data. Eight different data sets were constructed, representing various combinations of orthologous genes, data subsets, and taxa. Our results demonstrate that the different ways to compile an initial data set of core orthologs and the selection of data subsets by matrix reduction can have marked effects on the reconstructed phylogenetic trees. Nonetheless, all eight data sets strongly support Pancrustacea with Remipedia as the sister group to Hexapoda. This is the first time that a sister group relationship of Remipedia and Hexapoda has been inferred using a comprehensive phylogenomic data set that is based on EST data. We also show that selecting data subsets with increased overall signal can help to identify and prevent artifacts in phylogenetic analyses.

Marine lava cave fauna: composition, biogeography, and origins.

An assemblage of endemic cavernicolous marine invertebrates, including taxa found on both sides of the Atlantic Ocean of great phylogenetic age or with affinities to deep sea organisms, inhabits the Jameos del Agua cave, a sea waterflooded Holocene lava tube cave on Lanzarote in the Canary Islands. This marine cave contains both relicts from Tethyan times, such as an apparently new crustacean family belonging to what had been the monotypic class Remipedia, and relicts of groups that are now common only in the deep sea as well as species that occur outside the cave.

Annual and lunar reproductive rhythms of the sea urchin, Diadema antillarum (Philippi) in Bermuda

In the tropical Atlantic echinoid, Diadema antillarum in Bermuda, the gonads grow mainly in spring when sea temperatures are increasing, and spawning occurs from early summer to early winter. Peak spawning appeared to be in early summer and late fall. Gametogenesis is closely synchronized among different individuals and there is a well-defined lunar rhythm. Oocytes grow mainly between the first and third lunar quarters, and the animals spawn near the time of the new moon. Lunar synchrony, coupled with a spawning pheromone, may serve to maximize success of fertilization, while the restricted annual reproduction may maximize larval survival.

Mictocaris halope, a new unusual peracaridan crustacean from marine caves on Bermuda

ABSTRACT A new family, Mictocarididae, is proposed for Mictocaris halope, a new genus and species of peracarid crustacean from 4 marine caves on Bermuda. The Mictocarididae do not fit into any known peracaridan order, and a new order, Mictacea, is erected for it and for the Hirsutiidae of Sanders, Hessler, and Garner, 1985 (preceding paper in this journal) by Bowman et al., 1985 (immediately following paper). Mictocaris differs from Hirsutia in possessing eyestalks and a rostrum, an anteriorly rounded labium, marginal setae on the mandibular palp, nonsetose oostegites arising medially, and a pereiopod 2 that is not enlarged.

Two new genera of Calanoida and a new order of Copepoda, Platycopioida, from marine caves on Bermuda

Abstract The new cope pods were taken in inland marine caves. Erebonectes nesioticus is a calanoid and considered to belong to the Epacteriscidae and characterized by a 27-segmented 1st antenna of the female, essentially unmodified mouthparts and 3-segmented rami of all legs of both sexes, however, with strongly modified exopods of the 5th legs of the male. Paracyclopia naessi is a calanoid and belongs to the Pseudocyclopiidae and resembles Pseudocyclopia, but has 24-segmented 1st antennae of the female, a different setation of the endopods of the 1st legs, and simple uniramous 5th legs of the male. Antrisocopia prehensilis is a platycopiid with geniculate 1st antennae on both sides of the male, with both sexes having essentially similar 5th legs and 5-segmented urosomes. Platycopia and Antrisocopia are considered to represent a new order, the Platycopioida, separate from the Calanoida within the gymnoplean lineage. Antrisocopia and Erebonectes can be regarded as ‘living fossils,’ and it is possible that ...

Age determination of recent cave deposits using excess 210Pb ‐ A new technique

Cave deposits have been widely used as proxy recorders in deciphering palaeoclimate during the last glacial/interglacial maxima (∼ 120 ka) [Harmon et al., 1975; Atkinson et al., 1978; Goede and Harmon, 1983; Ayliffe and Veeh, 1989]. Palaeoclimatic studies of cave deposits for the past 1–1000 yr time scale require a precise dating technique, that until now has been lacking. Due to the multiple sources of carbon in speleothems, 14C dates obtained for recently deposited calcite are highly variable and thus, 14C dating techniques are not suitable to obtain speleothem ages for the past 1–1000 years. Here, we show for the first time that speleothems contain high concentrations of excess 210Pb and that this 210Pb excess can be successfully employed to obtain growth rates of speleothems deposited during the last 100 years. Of two specimens analyzed, a tubular “soda straw” stalactite yielded a longitudinal growth rate of 1.1 mm/yr, while a normal icicle-shaped stalactite had a lateral growth rate of 0.028 mm/yr. The mass growth rates of these two speleothems (149 and 78 mg/yr respectively) are comparable within a factor of two. Studies of fine-scale variations in the isotopic composition of recent speleothems will help to corroborate the validity of palaeoclimate records obtained using longer lived isotopes and extending back into Pleistocene.

Drawn to the dark side: A molecular phylogeny of freshwater shrimps (Crustacea: Decapoda: Caridea: Atyidae) reveals frequent cave invasions and challenges current taxonomic hypotheses

Atyid freshwater shrimps are globally distributed and form an important part of freshwater ecosystems, particularly in the tropics and subtropics. Despite their widespread distribution and ecological importance, their phylogenetic relationships are largely unresolved. Here we present the first comprehensive molecular phylogeny of the Atyidae investigating the evolutionary relationships among 32 of the 42 genera using mitochondrial and nuclear markers. Our data indicate that the established classification of the Atyidae is in need of substantial taxonomic revision at all taxonomic levels. We suggest a new suprageneric systematization of atyids and discuss problematic issues at the generic level, particularly in the most speciose genus, Caridina. Molecular clock based divergence time estimates for atyids vary widely, but invariably support the assumption that atyids are an ancient freshwater lineage with an origin in the mid-Cretaceous at the very latest. Atyid distribution patterns are the result of instances of both long-distance dispersal and vicariance, depending largely on the reproductive mode of taxa. From an evolutionary perspective, the high frequency of independent origin of both a complete (landlocked) freshwater life cycle and a cave-dwelling mode of life is remarkable and unparalleled among crustaceans.

The Epacteriscidae, a cave-living family of calanoid copepods

Abstract Twelve genera and 20 species of epacteriscids are recorded from marine and anchialine caves in tropical and subtropical waters. Nine genera are new: Eduxiella from Jamaica; Ena111ronia from Lanzarote, the Canary Islands; Balinella, Bojitriella, Bomburiella, Enantronoides, and Oinella from the Bahamas; Gloinella from Cuba; Erebonectes macrochaetus Fosshagen from the Caicos Islands, West Indies is transferred to a new genus Erebonectoides. Six new species of Enantiosis Barr are described, one each from Bermuda, Belize, Galapagos, and Fiji, and two from Palau. Two new species of Epacteriscus Foss hagen arc described from Belize and E. rapax Fosshagen is recorded for the first time in Bermuda. New records of Erebonectes nesioticus Fosshagen are made in Bermuda and a habitat division between three species of Epacteriscus, Enantiosis and Erebonectes from Bermuda is suggested. A phylogenetic analysis of described taxa was performed using PAUP. Based on inferences from this analysis two new subfamilies are proposed: the Erebonectinae (to include Erebonectes and Erehonectoides) and the Epacteriscinae (to include all ten other genera).

Global Biodiversity and Phylogenetic Evaluation of Remipedia (Crustacea)

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.

MICTACEA, A NEW ORDER OF CRUSTACEA PERACARIDA

ABSTRACT A new order, Mictacea, is proposed within the superorder Peracarida for Hirsutia bathyalis Sanders, Hessler, and Garner and Mictocaris halope Bowman and Iliffe. The new order is characterized by a unique combination of characters, most of which are not unique to the Mictacea, but are found in at least one other peracaridan order.