Phylogeny and historical biogeography of the cave-adapted shrimp genus Typhlatya (Atyidae) in the Caribbean Sea and western Atlantic

Aim To infer phylogenetic relationships among five species of the cave‐adapted shrimp genus Typhlatya in order to test competing hypotheses of dispersal and colonization of the disjunct cave localities occupied by these five species. Location Typhlatya species are found in caves and anchialine ponds across the northern margin of the Caribbean Sea, along the Mediterranean and Adriatic coasts and on oceanic islands in the Atlantic and eastern Pacific oceans. This study focuses on five species, one from Bermuda, one from the Caicos Islands and three from the Yucatan Peninsula of Mexico. Methods Partial sequences (c. 1400 bp) from the mitochondrial cytochrome b, 16S rDNA and COI genes were obtained from representative samples of the five species. Phylogenetic inference was carried out with maximum parsimony and maximum likelihood analyses. Parsimony networks were constructed for the Bermudian species Typhlatya iliffei and one Yucatan species Typhlatya mitchelli, to determine the degree of connectivity among populations inhabiting different cave systems. Results All three land masses were recovered as monophyletic. The two insular marine species from Bermuda and the Caicos Islands formed a clade, while the three continental freshwater species from the Yucatan Peninsula formed another. Within both Bermuda and the Yucatan, shared haplotypes were found in different cave systems, suggesting recent or ongoing gene flow among populations in both locales. Main conclusions The two insular marine Typhlatya species originated from an ancestral marine population, possibly already cave‐adapted, that is suggested to have colonized the Caicos Islands and subsequently dispersed to Bermuda via the Gulf Stream. Divergence estimates suggest that colonization occurred before the formation of present‐day anchialine cave habitat, which did not form on either island until the late Pliocene to early Pleistocene. Divergence estimates also indicate that the Yucatan freshwater species split before the formation of freshwater cave habitat in the Yucatan. These species could have inhabited crevicular marine habitats before the late Pliocene/early Pleistocene in the Yucatan or elsewhere in the Caribbean, and subsequently migrated to freshwater caves once they formed.     

Phylogeny and systematics of Aphroditiformia

Aphroditiformia represents one of the most successful radiations of annelids, and is therefore an interesting model to understand morphological and functional evolution. Previous phylogenetic analyses yielded most families as monophyletic but excluded anchialine and interstitial species while failing to recover relationships within Sigalionidae. Here we address these shortcomings through the analysis of four molecular markers and 87 morphological characters sampled across 127 species under the assumptions of parsimony and model‐based methods. Of the 34 newly sequenced taxa, five anchialine and 24 interstitial species were included, with increased representation of Sigalionidae. An additional 28 elusive Sigalionidae taxa were included, represented only by morphological partitions. Molecular and morphological partitions were evaluated under exhaustive sensitivity analyses, testing the effects of alignment algorithms and optimization criteria on tree topologies. Our trees congruently recovered six clades corresponding to the families within Aphroditiformia: Acoetidae, Aphroditidae, Eulepethidae, Iphionidae, Polynoidae and Sigalionidae, respectively. An anchialine polynoid lineage was nested among strictly deep sea species, and interstitial pisionids and pholoids formed two independent clades nested within Sigalionidae. Additionally, Sigalionidae resulted in four clades, defined by combinations of apomorphies, and hereby we propose the subfamilies Pelogeniinae, Pholoinae, Pisioninae, Sthenelanellinae, as well as the provisionally included polyphyletic Sigalioninae.     

Fatty acid synthesis in the brown fat and liver of foetal and newborn rabbits (Short Communication)

The postnatal fall in fatty acid synthesis in the liver and brown fat of newborn rabbits is accompanied in both tissues by a decrease in the capacities of the enzymes of fatty acid synthesis and an apparent increase in the degree of inhibition of one or more of these enzymes.     

Evolution of cave suspension feeding in Protodrilidae (Annelida)

Protodrilidae belongs in a lineage that until now entirely consisted of deposit‐feeding, highly adapted interstitial annelids. Except for a pair of anterior palps, all protodrilids lack appendages, parapodia and chaetae; and have slender bodies adapted to glide between the sand grains by ciliary motion. The first exception to these characteristics is Megadrilus pelagicus n. sp. inhabiting the water column of the anchialine La Corona cave system in Lanzarote. Its morphology and evolutionary history are here investigated by combining observations from in vivo video recordings and advanced microscopy with phylogenetic analyses. Our studies revealed a unique pelagic, suspension feeding behaviour attained by its long ciliated palps in combination with an autopomorphic dorsal ciliated keel and several longitudinal and transverse ciliary bands. Phylogenetic analyses recovered Megadrilus pelagicus n. sp. nested within Protodrilidae indicating that its unique traits are derived within the family. These traits are traced in the tree topologies in correlation to cave colonization. The evolution of these traits can be functionally explained by the different demands of a pelagic suspension feeding strategy compared to the ancestral deposit‐feeding guild of the family. The origin of this suspension feeding strategy was presumably favoured by the partial isolation of the anchialine ecosystem, connected to the sea only through the highly porous volcanic subterranean bedrock. This crevicular connection limits the amount of predators and turbulence in the cave, but allows continuous water flow into the system carrying organic particles, which is the main source of food when photosynthetic primary production does not occur and sedimentation is limited. These conditions may select for pelagic suspension feeding as the most feasible life‐strategy in anchialine caves, which the dominance of pelagic, suspension feeding crustaceans and annelids in anchialine cave assemblages may also reflect. For species of ancestrally deposit‐feeding lineages entering the cave system, such as the annelid families Protodrilidae and Nerillidae, an adaptive‐shift from interstitial to crevicular habitats seemingly correlates with dramatic morphological changes and speciation. The dramatic changes observed in these primarily interstitial lineages compared to their relatives, point to alternative adaptive evolutionary pathways related to ecological fitness contrary to the previously proposed theories focusing on geological or stochastic processes.