Tunicate tails, stolons, and the origin of the vertebrate trunk

Tunicates are primitive chordates that develop a transient 'tail' in the larval stage that is generally interpreted as a rudimentary version of the vertebrate trunk. Not all tunicates have tails, however. The groups that lack them, salps and pyrosomes, instead have a trunk-like reproductive stolon located approximately where the tail would otherwise be. In salps, files of blastozooids are formed along the sides of the stolon. The tail and caudal trunk in more advanced chordates could have evolved from a stolon of this type, an idea referred to here as the 'stolon hypothesis'. This means the vertebrate body could be a composite structure, since there is the potential for each somite to incorporate elements originally derived from a complete functional zooid. If indeed this has occurred, it should be reflected in some fashion in gene expression patterns in the vertebrate trunk. Selected morphological and molecular data are reviewed to show that they provide some circumstantial support for the stolon hypothesis. The case would be stronger if it could be demonstrated that salps and/or pyrosomes are ancestral to other tunicates. The molecular phylogenies so far available generally support the idea of a pelagic ancestor, but offer only limited guidance as to which of the surviving pelagic groups most closely resembles it. The principal testable prediction of the stolon hypothesis is that head structures (or their homologues) should be duplicated in series in the trunk in advanced chordates, and vice versa, i.e. trunk structures should occur in the head. The distribution of both rhabdomeric photoreceptors and nephridia in amphioxus conform with this prediction. Equally striking is the involvement of the Pax2 gene in the development of both the inner ear and nephric ducts in vertebrates. The stolon hypothesis would explain this as a consequence of the common origin of otic capsules and excretory ducts from atrial rudiments: from the paired rudiments of the parent oozooid in the case of the otic capsule (these express Pax2 according to recent ascidian data), and from tubular rudiments in the stolon in the case of the excretory ducts.     

Jet propulsion in salps (Tunicata: Thaliacea)

This paper describes the locomotion of salps by jet propulsion, from a combination of measurements of chamber pressures, static thrust, and electromyographic activity, with kinematic records of free-swimming and tethered salps. From such measurements, estimates are made of the thrust exerted, the drag incurred, and the work performed by single salps, and by chains of linked individuals. It is concluded that salp jet propulsion is a more economical process than is jet propulsion in other animals.     

Factors affecting the drinking behavior of black howler monkeys (Alouatta pigra)

Water is essential for animals, and is particularly critical for thermoregulation. Animals obtain water from three main sources, free water, water contained in food, and water produced in the body during metabolism. Howler monkeys (Alouatta spp.) spend a small proportion of their time drinking water and some populations have not been observed drinking, suggesting they obtain most of their water requirements in food or by metabolism. However, when howler monkeys have been observed drinking there is evidence suggesting the drinking is associated with low precipitation, temperature, and fruit consumption, and high mature leaf consumption, although it remains unclear which factors determine drinking by this genus. In this study we tested the hypothesis that drinking by howler monkeys results from increased hydration requirements in drier climates and from lower consumption of foods rich in water (e.g., new leaves, fruit). We tested this hypothesis by comparative analysis of 14 groups of Yucatán black howler monkeys (A. pigra) living under different climatic conditions. From April 2005 to November 2008 we collected a total of 3,747.2 focal observation hours of the feeding and drinking behavior of 60 individuals, with data on ambient temperature and rainfall. Individuals spent more time drinking when they lived in habitats with higher maximum temperature and when they consumed more mature leaves. For this species, therefore, drinking seems to be linked to heat stress and a low availability of water in ingested food.     

Antarctic krill (Euphausia superba Dana) eat salps

 Feeding behaviour of Antarctic krill (Euphausia superba) on salps was observed in shipboard experiments during the 1994/1995 Kaiyo Maru Antarctic Ocean research cruise. The feeding rate was more than 0.5 salp/krill per day. When offered ethanol extracts of four prey types, salps, phytoplankton, krill and polychaetes, krill preferred the salp extracts. This evidence implies that the substances extracted from salps were most attractive to krill. These results might indicate a tight ecological relationship between krill and salps. Received: 24 May 1995/Accepted: 8 October 1995     

Pickle barrels as enrichment objects for rhesus macaques.

Two breeding groups of rhesus monkeys (Macaca mulatta) housed in outdoor enclosures on Key Lois island were observed for 84 hours. Instantaneous scan sampling of a focal animal was used to gather data to test hypotheses concerning frequencies of agonistic and affiliative behaviors as well as differential use of pickle barrels as enrichment objects. Type of barrel used, behavior, and age/sex class of the animal were noted. Barrels were arranged three ways: unattached, on a swivel, and stationary. The behaviors of animals in an enriched environment were compared with control condition animals, which did not have pickle barrels. Animals in an enriched environment accounted for 60.8% (n = 56) of total affiliative contact, 62.2% (n = 399) of total social grooming, and 26% (n = 5) of total agonistic noncontact. A total of 134 scans of barrel use were observed. Analyses of the data showed that swivel and stationary barrels were used the most (55% of all scans of barrel use). Yearlings, juvenile females, and old males used barrels most often (82.8% of all scans of barrel use), although they constituted only 39% of the enriched environment population. In this study, pickle barrels provided enrichment for young and old animals of both sexes.     

Fatal Asphyxiation in Two Long-Finned Pilot Whales (Globicephala melas) Caused by Common Soles (Solea solea)

Long-finned pilot whales (Globicephala melas) are rare visitors to the southern North Sea, but recently two individual strandings occurred on the Dutch coast. Both animals shared the same, unusual cause of death: asphyxiation from a common sole (Solea solea) stuck in their nasal cavity. This is a rare cause of death in cetaceans. Whilst asphyxiation has been reported in smaller odontocetes, there are no recent records of this occurring in Globicephala species. Here we report the stranding, necropsy and diet study results as well as discuss the unusual nature of this phenomenon. Flatfish are not a primary prey species for pilot whales and are rarely eaten by other cetaceans, such as harbour porpoises (Phocoena phocoena), in which there are several reports of asphyxiation due to airway obstruction by soles. This risk may be due to the fish’s flexible bodies which can enter small cavities either actively in an attempt to escape or passively due to the whale ‘coughing’ or ‘sneezing’ to rid itself of the blockage of the trachea. It is also possible that the fish enter the airways whilst the whale is re-articulating the larynx after trying to ingest large, oddly shaped prey. It is unlikely that the soles entered the airways after the death of the whales and we believe therefore that they are responsible for the death of these animals.     

Zooplankton feeding ecology: clearance and ingestion rates of the salps Thalia democratica, Cyclosalpa affinis and Salpa cylindrica on naturally occurring particles in the Mid-Atlantic Bight

Aggregate stages of the salps Thalia democratica, Cyclosalpaaffinis and Salpa cylindrica collected by SCUBA diving in theMid-Atlantic Bight were fed with naturally occurring food assemblages.This is one of the few studies where salps have been fed withnatural food assemblages. The estimated clearance rate for allspecies based on disappearance of chlorophyll varied from 82to 444 mL individual^–1 day^–1. Cell counts showedthat T. democratica mostly ingested carbon from autotrophicnanoflagellates and autotrophic dinoflagellates. Ingestion byS. cylindrica was primarily on larger prey, such as dinoflagellates,while C. affinis ingested auto- and heterotrophic nanoflagellates.All main prey types ingested by salps corresponded to thosethat contributed most to biomass at each experimental station.Thus, salps fed on naturally occurring particles primarily inproportion to prey biomass and to their mechanical capacityto be retained and ingested. Feeding by salps on dinoflagellatesand ciliates implies that they may act not only as potentialcompetitors with microzooplankton, but also as consumers ofthem.     

Punica granatum L. (pomegranates) from early Roman contexts in Vindonissa (Switzerland)

At the later legionary camp of Vindonissa, early Roman (Augustan-Claudian) structures were excavated during a rescue excavation between 1996 and 1998. In phase 2 (10 B.C. until 0), seven in situ carbonised wooden barrels, dug into the ground, were found. They belonged to a rather large building which was most probably used as storage facility. Two of the barrels contained, in the bottom layers, several hundred seeds and pericarp fragments of Punica granatum L. (pomegranates). A large number of other "exotic" plant taxa such as olive, walnut, pine, pistacio, peach, cherry (and probably date) were also found in rather large quantities. Above all, the finds of pomegranates are unique: they are the first finds of this Mediterranean fruit in regions north of the Alps. The origin, use, and other archaeological finds of the pomegranate in the Roman period are discussed. A comparison with other early Roman spectra shows that such large quantities of "exotic" useful plants are mainly present at larger military sites like the legionary camps of Novaesium or Oberaden. It must also be suggested that the pre-camp phases in Vindonissa already had a military charaeter, although this is not at all clear from the other archaeological finds. The precise role of the site is still a matter of debate. Received November 22, 2001 / Accepted February 19, 2002     

Spatial distributions and population dynamics of two salp species, Ihlea racovitzai and Salpa thompsoni, in the waters north of Lützow-Holm Bay (East Antarctica) during austral summers of 2005 and 2006

Information on the sequences of generations and reproductive states of salps in the Southern Ocean is essential for an improved understanding of salp population growth, although changes in distribution patterns of two species of salps, Salpa thompsoni and Ihlea racovitzai, in the Southern Ocean have the potential to alter the Southern Ocean ecosystem. We used stratified, quantitative sampling from the surface to 2,000 m depth with an RMT 8 net in January of 2005 and 2006 to determine the distribution and population structure of salps in the north of Lützow-Holm Bay, East Antarctica. Ihlea racovitzai occurred in both 2005 and 2006, but S. thompsoni was found only in 2005. Ihlea racovitzai occurred abundantly along the ice edge where Antarctic Winter Water was well developed, whereas S. thompsoni was more abundant at northern stations affected by warm Modified Circumpolar Deep Water. Small solitary stages of I. racovitzai dominated in 2005, but they had declined significantly by 2006. The S. thompsoni population was composed of small immature aggregates and mature solitary stages, suggesting that the solitary stages were reproducing. We did not find mature aggregate and immature solitary stages in the present study and thus suggested that S. thompsoni was unable to complete its life cycle in the north of Lützow-Holm Bay because of failure of sexual reproduction in the aggregate stage. The S. thompsoni population was therefore probably transported to our study area by advection.     

Proximity of krill and salps in an Antarctic coastal ecosystem: evidence from penguin-mounted cameras

Antarctic krill (Euphausia superba) and salps (mainly Salpa thompsoni) are main components of Southern Ocean ecosystem, but little is known about their coastal distribution at a fine scale (<1 km). We deployed miniaturised cameras on breeding chinstrap (n = 9 birds) and gentoo penguins (n = 9 birds) in the Antarctic Peninsula region and obtained 2,333 krill images, 93 salp images and 609 sea floor images from 1,843 dives. 51.2 % of penguin dives that had salps present in the images occurred near the dives with krill images (within 5 min). The vertical distribution of salp images showed overlap with the upper depth zone of krill images. While 16.3 % of dives with krill images were associated in time with the sea floor, only 1.2 % of dives with salp images did. These results revealed close proximity between krill and salps within the penguin’s foraging range in an Antarctic coastal ecosystem. These results also imply that krill patches were common in both pelagic and benthic habitat, whereas salps were common mainly in pelagic habitat. If the effects of deployments are similar between the years or regions, inter-annual or regional comparison using the penguin-mounted camera will be valid for characterising prey environment in the penguin foraging area.     

Junctional complexes of the branchia and gut of the tunicate,Pyrosoma atlanticum (Pyrosomatida,Thaliacea)

Summary The branchia of pyrosomes has been found to be like that of ascidians in that it shares with the latter, besides the presence of peribranchial chambers, stigmata bordered by clusters of seven rows of flattened cells, each bearing a single row of long cilia. The intercellular junctions between ciliated cells of the branchial basket and between the cells lining the gut, in pyrosomes, have been studied in thin sections and by freeze-fracture. In both tissues tight and gap junctions are present, but the former are much more extensive in the gut. The gap junctions in the branchial basket exhibit some atypical features. Moreover, although there are extensive zonulae adhaerentes between the ciliated cells of the branchial basket, there are none between the epithelial cells of the intestinal tract. This feature of the branchiae, together with the alignment of their cells into highly ordered rows of seven cells, are similar to those found in some groups of ascidians. The evolutionary relationships between pyrosomes and the aplousobranch ascidians are considered in the light of these results.     

Maintaining social cohesion is a more important determinant of patch residence time than maximizing food intake rate in a group-living primate,Japanese macaque (Macaca fuscata)

Animals have been assumed to employ an optimal foraging strategy (e.g., rate-maximizing strategy). In patchy food environments, intake rate within patches is positively correlated with patch quality, and declines as patches are depleted through consumption. This causes patch-leaving and determines patch residence time. In group-foraging situations, patch residence times are also affected by patch sharing. Optimal patch models for groups predict that patch residence times decrease as the number of co-feeding animals increases because of accelerated patch depletion. However, group members often depart patches without patch depletion, and their patch residence time deviates from patch models. It has been pointed out that patch residence time is also influenced by maintaining social proximity with others among group-living animals. In this study, the effects of maintaining social cohesion and that of rate-maximizing strategy on patch residence time were examined in Japanese macaques (Macaca fuscata). I hypothesized that foragers give up patches to remain in the proximity of their troop members. On the other hand, foragers may stay for a relatively long period when they do not have to abandon patches to follow the troop. In this study, intake rate and foraging effort (i.e., movement) did not change during patch residency. Macaques maintained their intake rate with only a little foraging effort. Therefore, the patches were assumed to be undepleted during patch residency. Further, patch residence time was affected by patch-leaving to maintain social proximity, but not by the intake rate. Macaques tended to stay in patches for short periods when they needed to give up patches for social proximity, and remained for long periods when they did not need to leave to keep social proximity. Patch-leaving and patch residence time that prioritize the maintenance of social cohesion may be a behavioral pattern in group-living primates.     

Genomic approaches to detecting thermal stress in Calanus finmarchicus (Copepoda: Calanoida)

Zooplankton may be subjected to physiological stress as they encounter rapid and large changes in temperature through vertical migration or transfer into different water masses. Induction of one or more heat shock proteins (hsp) is a common protective response to thermal stress in organisms. We looked for evidence for such a response in Calanus finmarchicus. We compared hsp70 expression in copepods exposed to temperature stress with that for non-stressed controls. Partial sequences of the amplified cDNA product were obtained and aligned with known hsp70 sequences to establish the identity of the heat shock protein. In one experiment, animals were transferred from their collection temperature (8 °C) to 20 °C for 30 min, and then returned to 8 °C for 4 h before sampling for gene expression levels. In another, the animals were exposed to 18 °C over 48 h before sampling for molecular analysis. A four-fold induction of hsp70 was measured in both groups of heat shocked animals using quantitative real time polymerase chain reaction (PCR). The experimental temperatures, although high for C. finmarchicus, are within the range of temperatures experienced by this species in their habitat. In addition to confirming an hsp70-mediated response in C. finmarchicus, the findings suggest that a recent history of thermal stress may be assessed in natural populations through a routine molecular assay.     

Cultural transmission of tool use by Indo-Pacific bottlenose dolphins (Tursiops sp.) provides access to a novel foraging niche

Culturally transmitted tool use has important ecological and evolutionary consequences and has been proposed as a significant driver of human evolution. Such evidence is still scarce in other animals. In cetaceans, tool use has been inferred using indirect evidence in one population of Indo-Pacific bottlenose dolphins (Tursiops sp.), where particular dolphins (‘spongers’) use marine sponges during foraging. To date, evidence of whether this foraging tactic actually provides access to novel food items is lacking. We used fatty acid (FA) signature analysis to identify dietary differences between spongers and non-spongers, analysing data from 11 spongers and 27 non-spongers from two different study sites. Both univariate and multivariate analyses revealed significant differences in FA profiles between spongers and non-spongers between and within study sites. Moreover, FA profiles differed significantly between spongers and non-spongers foraging within the same deep channel habitat, whereas the profiles of non-spongers from deep channel and shallow habitats at this site could not be distinguished. Our results indicate that sponge use by bottlenose dolphins is linked to significant differences in diet. It appears that cultural transmission of tool use in dolphins, as in humans, allows the exploitation of an otherwise unused niche.     

New records of Amphipoda Hyperiidea in associations with gelatinous zooplankton

Associations between Amphipoda Hyperiidea specimens and gelatinous zooplankton such as cnidarians, ctenophores or salps are known in the literature. It is well established that many hyperiids are intimately associated with gelatinous zooplankton during part or all of their life-cycles, and that the associations could be of commensal or of parasitic nature, sometimes very highly species-specific. Although conventional net sampling usually does not preserve evidence of these associations, 12 instances of association (I.A.) were found in nine of the 49 samples collected during the 'FINEP XI Cruise', carried out on the Southeast coast of Brazil (23–28 °S), in January 1980. Lestrigonus bengalensisGiles, 1887 (11 specimens) and Simorhynchotus antennarius(Claus, 1871) (one specimen) were found inside salps and siphonophores. The study of the nature of these associations is essential to the understanding of the evolution of the group.     

Lifestyles of plant viruses

The vast majority of well-characterized eukaryotic viruses are those that cause acute or chronic infections in humans and domestic plants and animals. However, asymptomatic persistent viruses have been described in animals, and are thought to be sources for emerging acute viruses. Although not previously described in these terms, there are also many viruses of plants that maintain a persistent lifestyle. They have been largely ignored because they do not generally cause disease. The persistent viruses in plants belong to the family Partitiviridae or the genus Endornavirus. These groups also have members that infect fungi. Phylogenetic analysis of the partitivirus RNA-dependent RNA polymerase genes suggests that these viruses have been transmitted between plants and fungi. Additional families of viruses traditionally thought to be fungal viruses are also found frequently in plants, and may represent a similar scenario of persistent lifestyles, and some acute or chronic viruses of crop plants may maintain a persistent lifestyle in wild plants. Persistent, chronic and acute lifestyles of plant viruses are contrasted from both a functional and evolutionary perspective, and the potential role of these lifestyles in host evolution is discussed.     

Caloric restriction and the aging process: a critique

The main objective of this review is to provide an appraisal of the current status of the relationship between energy intake and the life span of animals. The concept that a reduction in food intake, or caloric restriction (CR), retards the aging process, delays the age-associated decline in physiological fitness, and extends the life span of organisms of diverse phylogenetic groups is one of the leading paradigms in gerontology. However, emerging evidence disputes some of the primary tenets of this conception. One disparity is that the CR-related increase in longevity is not universal and may not even be shared among different strains of the same species. A further misgiving is that the control animals, fed ad libitum (AL), become overweight and prone to early onset of diseases and death, and thus may not be the ideal control animals for studies concerned with comparisons of longevity. Reexamination of body weight and longevity data from a study involving over 60,000 mice and rats, conducted by a National Institute on Aging-sponsored project, suggests that CR-related increase in life span of specific genotypes is directly related to the gain in body weight under the AL feeding regimen. Additionally, CR in mammals and “dietary restriction” in organisms such as Drosophila are dissimilar phenomena, albeit they are often presented to be the very same. The latter involves a reduction in yeast rather than caloric intake, which is inconsistent with the notion of a common, conserved mechanism of CR action in different species. Although specific mechanisms by which CR affects longevity are not well understood, existing evidence supports the view that CR increases the life span of those particular genotypes that develop energy imbalance owing to AL feeding. In such groups, CR lowers body temperature, rate of metabolism, and oxidant production and retards the age-related pro-oxidizing shift in the redox state.     

Phylogenetics of Stelis and closely related genera (Orchidaceae: Pleurothallidinae)

Stelis, one of the largest genera within Pleurothallidinae, was recently recircumscribed to include a few hundred more species, most of which had previously been assigned to Pleurothallis. Here, a new phylogenetic analysis of Stelis and closely related genera based on DNA sequences from nuclear ITS and chloroplast matK, based on a much larger sample, is presented; it includes more than 100 species assigned to Stelis and covers all proposed groupings within the genus, many of which have not previously been represented. Clades are proposed to enable easier discussion of groups of closely related species; each clade is characterized morphologically, ecologically, and geographically to explain the evidence found in the molecular analysis. Discussion of the evolutionary trends of character states found in the genus in its broad sense is given. The current taxonomy of the group is given and the possible taxonomical implications of the findings presented here are discussed.