Southern Caribbean Neogene palaeobiogeography revisited. New data from the Pliocene of Cubagua,Venezuela

Based on new data from the Pliocene gastropod assemblage of Cubagua Island, Venezuela, the palaeobiogeography of the southern Caribbean is reviewed. The data obtained from the southern Caribbean assemblages demonstrate a highly endemic fauna along the northern coasts of South America, distinct from that found in the neighbouring Isthmian region to the west, which has probably been in place since at least the early Neogene. These assemblages are characterised by a relative stability at generic level, but an extremely high turnover rate at specific level. The name Colombian–Venezuelan–Trinidad Subprovince is chosen over Puntagavilanian Subprovince and chorotypes and chronotypes are selected for the Gatunian Province and the Colombian–Venezuelan–Trinidad Subprovince.     

Abundance of Lytechinus variegatus (Echinoidea: Toxopneustidae) in the island of Cubagua, Venezuela

The sea urchin roe is among the highest valued seafood items in the world. Increasing demand has extended this fishery worldwide and cases of overfishing have been detected in some countries. On the eastern coast of Venezuela some species of sea urchin, such as Lytechinus variegatus, are consumed as food but studies to determine the abundance and size do no exist. Between February 1998 and April 1999 six sampling stations (depth under 5 m) in Cubagua island (perimeter 25 km) were visited in 11 occasions to study the population density of L. variegatus, with a 0.25 m2 quadrat thrown eight times over seagrass (Thalassia testudinum) beds. Temperature was determined on site, and water samples for salinity and dissolved oxygen concentration were collected. Each specimen was measured and returned to the sea. Diameter range was 8.6 to 74.2 mm (n=3 404) and mean size 26.56-55.34 mm. On the northern coast density varied from 2 to 23 urchins/m2; on the eastern coast from 15 to 82/m2 and from 21 to 58/m2 on the southern coast. On the north coast the seagrass beds are scarce.     

Demography of two lemming species on Bylot Island, Nunavut, Canada

Lemmings play a key role in the tundra food web and their widely reported cyclic oscillations in abundance may have a strong effect on other components of the ecosystem. We documented seasonal and annual variations in population density, reproductive activity, survival, and body mass of two sympatric species, the brown (Lemmus trimucronatus) and collared lemmings (Dicrostonyx groenlandicus), over a 2-year period on Bylot Island, Nunavut, Canada. We live trapped and marked lemmings on two grids throughout the summer and we estimated demographic parameters using three different capture–recapture methods. All three methods are based on robust estimators and they yielded similar population density estimates. The density of brown lemmings declined markedly between the 2 years whereas that of collared lemmings was relatively constant. For brown lemmings, 2004 was a peak year in their cycle and 2005 a decline phase. Density of brown lemmings also decreased during the summer, but not that of collared lemmings. The recruitment of juvenile brown lemmings in the population increased during the summer and was higher in the peak year than in the year after, but no change was detected in collared lemmings. Survival rates of both species tended to be lower during the peak year than in the following year and body mass of brown lemmings was higher in the peak year than in the following year. We conclude that both changes in adult survival and juvenile recruitment occur during the population decline of brown lemmings.     

Paralytic shellfish poisoning (PSP) in Margarita Island, Venezuela

A severe outbreak of Paralytic Shellfish Poisoning (PSP) occurred in Manzanillo and Guayacán, northwestern coast of Margarita Island, Venezuela, between August and October 1991. A bloom of dinoflagellates including Prorocentrum gracile, Gymnodinium catenatum and Alexandrium tamarense seemed to be responsible for this outbreak. Levels of PSP toxins in mussels (Perna perna) exceeded the international safety limit of saxitoxin, 80 microg STX/100 microg meat. PSP toxin values varied between 2548 and 115 microg STX/100 g meat in Manzanillo, and between 1422 and 86 microg STX/100 g meat in Guayacán. At both locations, the highest levels were detected in August, when 24 patients exhibited typical symptoms of PSP toxicity after consuming cooked mussels (16 required hospitalization). A high pressure liquid chromatographic (HPLC) procedure was recently used on the 1991 samples. The major toxin detected in samples of both locations was decarbamoyl saxitoxin (dcSTX), but low concentrations of saxitoxin were also found in Manzanillo samples. Gonyautoxins GTX1, GTX2 and GTX3 were detected only at Guayacán, while in both locations, decarbamoylgonyatouxin (dcGTX2,3) toxins were detected. These findings represent the first time that causative toxins of PSP in Venezuela have been chemically identified, and confirm the presence of dcSTX and dcGTX in mussels from the Caribbean Sea. The presence of dcSTX and dcGTX in shellfish is indicative that Gymnodinium catenatum was a causative organism for outbreak of PSP.     

Stable periodic solutions for two species,density dependent coevolution

This paper studies a four dimensional system of time-autonomous ordinary differential equations which models the interaction of two diploid, diallelic populations with overlapping generations. The variables are two population densities and an allele frequency in each of the populations. For single species models, the existence of periodic solutions requires that the genotype fitness functions be both frequency and density dependent. But, for two species exhibiting a predator-prey interaction, two examples are presented where there exists asymptotically stable cycles with fitness functions only density dependent. In the first example, the Hopf bifurcation theorem is used on a two parameter, polynomial vector field. The second example has a Michaelis-Menten or Holling term for the interaction between predator and prey; and, for this example, the existence and uniqueness of limit cycles for a wide range of parameter values has been established in the literature.     

Diameter-weight relationship and chromatic proportion of the sea urchin Lytechinus variegatus (Echinoidea: Toxopneustidae) in the islands of Margarita and Cubagua, Venezuela

In Margarita and Cabagua Islands, Venezuela, the sea urchin Lytechinus variegatus is consumed as food but few studies concern its biology. Between January 1999 and September 2000, 25 localities of Margarita and Cubagua islands we visited to determinate the relationship between diameter and weight of living urchins according to their coloration green or white. A total of 5 066 urchins (3 421 captured in Margarita and 1 645 in Cubagua) were measured. There is no significant difference in the weight-diameter relations of green or white sea urchins of both islands. The weight-diameter equation is P = 0.00246 D252. Utilizing a quadrant (0.5 x 0.5 m) monthly samples of urchins living in a 2 m2 of surface were taken to estimate the abundance of the specimens according their color (N = 6 948 urchins). The green urchins were more abundant than the white urchins, in a 3:2 proportion.     

Epidemiological and immunological aspects of human visceral leishmaniasis on Margarita Island,Venezuela

Sixty-five patients were diagnosed with visceral leishmaniasis (VL) on Margarita Island in the decade from 1990 to1999; 86.2% were <= 3 years old. All were leishmanin-negative at diagnosis. Evaluation of 23 cured patients in 1999 revealed that 22/23 had converted to leishmanin-positive; five had persisting antibodies to rK39 antigen, with no clinical evidence of disease. Leishmanin tests were positive in 20.2% of 1,643 healthy individuals from 417 households in endemic areas. Of the positive reactors, 39.8% were identified in 35 (8.4%) of the households, 15 of which had an antecedent case of VL, a serologically positive dog or both. Weak serological activity to rK39 antigen was detected in 3 of 488 human sera from the endemic areas. The presence of micro-foci of intense peri-urban transmission and the apparent absence of other Trypanosomatidae causing human disease offer a unique opportunity for the study of reservoirs, alternative vectors and evaluation of control measures on the Island.     

Ring width,climate and wood density relationships in two long-lived Tasmanian tree species

The great majority of dendroclimatological work in Australia has thus far relied on ring-width chronologies only. We report novel results from a pilot study that show the potential to develop density-based climatically sensitive chronologies from two long-lived conifers endemic to Tasmania: Pencil Pine and Celery Top Pine. Cross-dating of average ring density profiles within each of the two sites examined was comparable with the better replicated ring-width chronologies from the sites. Cross-dating potential for maximum density was also indicated. Correlations between density and climate for both species were stronger and more persistent across a window of several months than correlations between ring width and climate. These stronger correlations suggest that temperature reconstructions based on average density may be possible. The ability to develop high resolution temperature-sensitive chronologies would allow for spatial comparisons across regions such as Tasmania that are affected by multiple broad-scale climate systems. A particularly novel result was the finding that maximum density was significantly related to stream-flow at the end of the growing season. Further work is required to assess the potential to reconstruct temperature, and to reconstruct stream-flow for important Tasmanian catchments over the past 500–800 years.     

Natural dispersal to sub-Antarctic Marion Island of two arthropod species

Distinguishing between species that are recent natural colonists, recent anthropogenic introductions, or previously unknown, but long-term resident native species, is a challenge for those who manage the conservation of the Antarctic region. Here, we report the discovery of two new arthropod species on sub-Antarctic Marion Island—Nabis capsiformis Germar (Heteroptera: Nabidae) and Tetragnatha sp. (Araneomorphae: Tetragnathidae). On the basis of their habitat use, dispersal abilities, historic biodiversity survey records, and limited information on genetic diversity, we conclude that the colonization events were natural.     

Population dynamics of two snail species,Planaxis sulcatus and Cerithium moniliferum,and their trematode species at Heron Island,Great Barrier Reef

Summary The population dynamics of the prosobranch snail Planaxis sulcatus and its trematode parasites on 600 m of beachrock on the southern side of Heron Island, Great Barrier Reef, were studied. Populations of Planaxis show little mixing, due to lack of long-distance movements. From March 1973 to June 1975, an increase in the numbers of small and medium-sized snails occurred, but the biomass (dry tissue weight) of the snail population did not change. Snails were infected with one species of Aspidogastrea and six species of cerariae. Infections with cercariae did not significantly affect the relative weight of the snails. Multiple infections were random, i.e. neither negative nor positive interactions between trematode species could be demonstrated. Proportions of uninfected snails and snails infected with various trematode species remained more or less constant from July 1973 to February 1975.The population dynamics of the prosobranch snail Cerithium moniliferum and its 11 species of cercariae and one species of Aspidogastrea in a small area at Heron Island were studied. Numbers of large snails decreased and numbers of small snails increased from August 1973 to June 1975. The biomass of the Cerithium population increased only slightly. Prevalence of infection changed significantly only in large snails.Infections of Cerithium moniliferum and Peristernia australiensis with an aspidogastrid species decreased strongly from January 1971 to March/April 1972 and had not recovered by mid 1975.Seasonal fluctuations could not be demonstrated for any of the snails or parasites.The data for Planaxis suggest equilibrium conditions and saturation of the habitat.     

New species from the summit of Cerro Guaiquinima,Venezuela

Three new species,Lubaria szczerbanii (Rutaceae),Croton guaiquinimae (Euphorbiaceae), andStomatochaeta colveei (Asteraceae), are described from the summit of Cerro Guaiquinima, Venezuela. The generic affinities betweenLubaria andMyllanthus, and betweenStomatochaeta andStenopadus are discussed.     

Occurrence and Distribution of Stony Corals in the Gulf of Cariaco,Venezuela

Occurrence and distribution of stony corals (Milleporina and Scleractinia) in the Gulf of Cariaco were investigated quantitatively using skin-diving methods. Unusual temperature conditions due to cold upwelling limit coral growth to a depth of 15 m. A clear vertical zonation of species was observed, with five zones, in order of increasing depth, dominated by Porites porites, Millepora complanata, Siderastrea siderea, Dichocoenia stokesi, and Solenastrea hyades. Twenty-one species of scleractinians and three species of hydrocorals have so far been found in the gulf. Of the total area covered by corals, over 50% is inhabited by Siderastrea siderea, Millepora spp., and Porites porites. A horizontal zonation of the littoral was established based on species composition and density of the coral cover.     

A new species of a phyllophorid holothurian from southern Africa

A new species of a phyllophorid holothurian, Neothyonidium arthroprocessum, is described from the shallow waters of False Bay, South Africa. The new species is distinct from other phyllophorids in possessing peculiar narrow transverse slits in the body wall, a calcareous ring with joined posterior processes to the radial plates, and short thick perforated rods as body wall deposits. The diagnosis of the genus Neothyonidium is amended to accommodate the new species.     

Chemical composition of the essential oils of two Alpinia species from Hainan Island, China

The essential oils of two Alpinia species, ie. A. hainanensis and A. katsumadai, from Hainan Island, China were analyzed by using GC-MS. The major constituents in the leaf oil of A. hainanensis were ocimene (27.4%), beta-pinene (10.1%), 9-octadecenoic acid (6.5%), n-hexadecanoic acid (5.8%), 9,12-octadecadienoic acid (5.4%), and terpinen (4.3%). The oil constituents obtained from the flowers of A. hainanensis were ocimene (39.8%), beta-pinene (17.7%), terpinene (5.5%), p-menth-1-en-ol (4.9%), caryophyllene (4.9%), and phellandrene (4.4%). In A. katsumadai, the major constituents in the leaf oil were p-menth-1-en-ol (22.0%), terpinen (19.0%), 4-carene (9.1%), 1,8-cineole (8.3%), and camphor (5.6%). The major constituents in the flower oil were p-menth-1-en-ol (21.3%), 1,8-cineole (20.2%), terpinen (12.6%), phellandrene (7.0%), 4-carene (6.4%), and beta-pinene (5.2%).     

Cannibalistic interactions in two co-occurring decapod species: Effects of density, food, alternative prey and habitat

Cannibalism is a potentially important factor in the regulation of populations in a range of habitats. The intensity of this biotic factor may be determined by both intra and interspecific interactions. Cancer pagurus and Porcellana platycheles are two co-occurring decapods on Atlantic rocky shores. In laboratory mesocosms, we investigated intra and intersize class cannibalistic and interspecific predatory behaviours in those species. We addressed the effects of prey and predator densities, food, starvation, alternative prey and habitat type. No agonistic behaviour was noted in P. platycheles, suggesting a non-aggressive co-existence between gregarious individuals. Predation of C. pagurus on P. platycheles was intense, possibly accounting for the spatial segregation observed in the natural environment. Cannibalism among C. pagurus juveniles was low and only on vulnerable prey (i.e. at moulting), suggesting a non-aggressive co-existence among juveniles. However, intersize class cannibalism in C. pagurus was intense (ontogenetic shift), possibly reflecting the juvenile-adult segregation in the natural environment. Prey and predator densities, food and habitat type strongly influenced this behaviour. Possible interference among cannibals was noted, with lower prey consumption at high predator density. Food supply alone had more effect on cannibalistic rate than did alternative prey (P. platycheles) and predator starvation. Structurally complex habitats (small pebble and Fucus serratus habitats) yielded higher prey survival than the sandy habitat, and the behaviours of both prey and cannibals reflected the small-scale spatial distribution of individuals in the wild. Intersize class cannibalism and interspecific agonistic relationships may account for the intertidal distribution of crab species at low tide.     

Infection density of Wolbachia and incompatibility level in two planthopper species, Laodelphax striatellus and Sogatella furcifera

Wolbachia, a bacterial endosymbiote of arthropods, causes cytoplasmic incompatibility (CI) in many insect species. CI traits were studied in two planthopper species, Laodelphax striatellus and Sogatella furcifera, and Wolbachia densities in these planthopper species were calculated by quantitative PCR methods. The CI level of L. striatellus was quite high and even aged males strongly caused CI. In contrast, S. furcifera showed partial CI, and males lost their ability to cause CI with age. Wolbachia infecting these two planthopper species were the same with respect to the nucleotide sequences of Wolbachia genes, 16S rDNA, ftsZ gene, groE genes, and wsp gene. Two methods for quantitative PCR, one using a DNA sequencer and the other a real-time sequence detection system, were established to calculate the amount of Wolbachia in the planthoppers. The density of Wolbachia in S. furcifera males was quite low. The difference in CI levels between the two planthopper species seems to be due to different amounts of Wolbachia infecting males.     

A new genus and species of a dendrochirotid holothurian from Southern Africa

A new genus and species of a dendrochirotid holothurian, Pawsonellus africanus , from shallow waters off the east coast of Southern Africa, are described. The new genus is compared with several genera within the family Cucumariidae and it is concluded that it is not closely related to any of them. Although its body wall spicules strongly resemble those of Panningia hyndmani (Thompson), notably the typical form described by Madsen (1942), there are several features which suggest that the two species are not congeneric.     

Distribution of inorganic species in two Antarctic cryptoendolithic microbial communities

Chemical differences were noted between two Antarctic cryptoendolithic (hidden within rock) microenvironments colonized by different microbial communities. Microenvironments dominated by cyanobacteria (BPC) had a higher pH (pH 7–8) than those dominated by lichen (LTL) (pH 4.5–5.5). In order to understand the interactions between the microbiota and the inorganic environment, the inorganic environment was characterized. Water‐soluble, carbonate‐bound, metal‐oxide, organically bound, and residual inorganic species were sequentially extracted from rock samples by chemical means. Each fraction was then quantified using inductively coupled plasma atomic emission spectrometry. BPC contained much more water‐soluble and carbonate‐bound Ca and Mg than LTL. Metal‐oxide species of Al, Fe, and Mn were more abundant in LTL than BPC. Metal oxides appeared to be mobilized (in the order Mn > Fe > Al) from the LTL lichen zone but remained immobile in BPC sandstone. The distribution of K and P bound to metal oxide reflected the distribution of iron oxide in LTL, an indication of the importance of iron in controlling the availability of nutrients in this ecosystem. Metal oxides in turn were likely controlled or influenced by organic matter associated with the lichen community. Despite overall depletion of Fe, Al, and K in the lichen zone, SEM X‐ray analysis showed that they were enriched in fungal hyphae. Water‐soluble P was present despite the presence of metal oxides, which sequester phosphate. This has biological relevance since P is an essential nutrient.     

Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Temperate and boreal mammals undergo seasonal changes in pelage that facilitate thermoregulation in winter and summer. We investigated photoperiodic influences on pelage characteristics of male Siberian and Syrian hamsters. Fur density (mg fur/cm2 skin) was measured by weighing the shavings of fur patches removed from the dorsal and ventral surfaces of hamsters maintained in long days (LDs) or transferred to short days (SDs). Patches were reshaved 3 wk later to assess fur regrowth (mg regrown fur/cm2 skin). Fur density was greater in SD than in LD Siberian hamsters after 11 wk of differential phototreatment. The onset of increased fur density in SDs was accompanied by a transient increase in fur regrowth (11-14 wk on the dorsal surface and 7-10 and 11-14 wk on the ventral surface), suggestive of a seasonal molting process. Fur density, body mass, and pelage color of Siberian hamsters returned to values characteristic of LD males after a similar duration of prolonged (>27 wk) SD treatment and appear to be regulated by a similar or common interval-timing mechanism. In Syrian hamsters, dorsal fur density, fur regrowth, and hair lengths were greater in SD than in LD males. Castration increased and testosterone (T) treatment decreased dorsal and ventral fur regrowth in LD and SD hamsters, but the effects of T manipulations on fur density were limited to a decrease in dorsal fur density after T treatment. Decreased circulating T in SDs likely contributes to the seasonal molt of male hamsters by increasing the rate of fur growth during the transition to the winter pelage.