Southern Cuba Research Articles

Integrating classification and regression learners with bioimpedance methods for estimating weight status in infants and juveniles from the southern Cuba region

ObjectiveThe search for other indicators to assess the weight and nutritional status of individuals is important as it may provide more accurate information and assist in personalized medicine. This work is aimed to develop a machine learning predictions of weigh status derived from bioimpedance measurements and other physical parameters of healthy younger volunteers from Southern Cuba Region.MethodsA pilot random study at the Pediatrics Hospital was conducted. The volunteers were selected between 2002 and 2008, ranging in age between 2 and 18 years old. In total, 776 female and male volunteers are studied. Along the age and sex in the cohort, volunteers with class I obesity, overweight, underweight and with normal weight are considered. The bioimpedance parameters are obtained by measuring standard tetrapolar whole-body configuration. The bioimpedance analyser is used, collecting fundamental bioelectrical and other parameters of interest. A classification model are performed, followed by a prediction of the body mass index.ResultsThe results derived from the classification leaner reveal that the size, body density, phase angle, body mass index, fat-free mass, total body water volume according to Kotler, body surface area, extracellular water according to Kotler and sex largely govern the weight status of this population. In particular, the regression model shows that other bioparameters derived from impedance measurements can be associated with weight status estimation with high accuracy.ConclusionThe classification and regression predictive models developed in this work are of the great importance to assist the diagnosis of weigh status with high accuracy. These models can be used for prompt weight status evaluation of younger individuals at the Pediatrics Hospital in Santiago de Cuba, Cuba.

The role of various physiological and bioelectrical parameters for estimating the weight status in infants and juveniles cohort from the Southern Cuba region: a machine learning study

ObjectiveThe search for other indicators to assess the weight status of individuals is important as it may provide more accurate information and assist in personalized medicine.This work is aimed to develop a machine learning predictions of weigh status derived from bioimpedance measurements and other physical parameters of healthy infant juvenile cohort from the Southern Cuba Region, Santiago de Cuba.MethodsThe volunteers were selected between 2002 and 2008, ranging in age between 2 and 18 years old. In total, 393 female and male infant and juvenile individuals are studied. The bioimpedance parameters are obtained by measuring standard tetrapolar whole-body configuration. A classification model are performed, followed by a prediction of other bioparameters influencing the weight status.ResultsThe results obtained from the classification model indicate that fat-free mass, reactance, and corrected resistance primarily influence the weight status of the studied population. Specifically, the regression model demonstrates that other bioparameters derived from impedance measurements can be highly accurate in estimating weight status.ConclusionThe classification and regression predictive models developed in this work are of the great importance for accessing to the weigh status with high accuracy of younger individuals at the Oncological Hospital in Santiago de Cuba, Cuba.

Tectono-structural characterization and favorable sectors for hydrocarbons in the western basins of southern Cuba from non-seismic exploration methods

Las cuencas sedimentarias constituyen un objetivo tradicional de la exploración de petróleo y gas en todos los territorios. La cartografía de sus espesores sedimentarios es un elemento esencial por considerar, pero no siempre se dispone de esta información por la limitación en el volumen y calidad de los trabajos sísmicos y de perforación realizados. Las cuencas sedimentarias al sur del archipiélago cubano tienen un basamento magnético integrado por secuencias de rocas volcánicas con ofiolitas. La cartografía de los espesores sedimentarios y la composición del basamento pueden establecerse a partir del procesamiento e interpretación de los datos de campos potenciales. Se utilizó un enfoque integrado que consideró la determinación de la profundidad al basamento magnético y el modelado físico-geológico 2D de campos potenciales. Se utilizaron complementariamente, métodos morfométricos a partir del Modelo de Elevación Digital 90 × 90 m. El objetivo principal de la investigación fue caracterizar desde el punto de vista tectono-estructural las cuencas occidentales del sur de Cuba y el objetivo específico fue establecer los sectores favorables para hidrocarburos, básicamente, a partir de la espectrometría aérea con rayos gammas en sectores terrestres. El campo de las profundidades al basamento magnético (datos magnéticos y de pozos) se aproximó a los límites conocidos de las cuencas. El modelado físico-geológico 2D de campos potenciales por el perfil de estudio confirmó el modelo geológico de partida. Las localidades más promisorias para hidrocarburos correspondieron al pozo Taco Taco n.o1 (Cuenca Los Palacios) y los pozos someros La Paila y El Sulfuroso y los pozos Madruga (Cuenca Vegas).

Distribution and length composition of lemon sharks (Negaprion brevirostris) in a nursery ground in southern Cuba

Characterization of essential habitat for sharks is a key requirement for effective conservation of shark populations. In Cuba, shark essential habitat is largely undocumented. Here we present the first study of a shark nursery area in Cuban waters, for the lemon shark. Nursery areas for lemon sharks are typically surrounded by mangroves and contain sandy substrate where the young can feed, grow, move, and eventually disperse from the area. We conducted our study in Cuba’s La Salina Wildlife Refuge during 2015–2019, to understand the role this refuge might play as a lemon shark nursery area, by documenting the distribution and length structure of juveniles. Our results indicate that juvenile lemon sharks are present throughout much of the refuge with no clear pattern of aggregation by size. The size range of all juveniles captured was 39.8–108.0 cm precaudal length (PCL) with a mode in length-class 70.0–75.0 cm PCL. The mean size and weight of all individuals during the study period was 75.8 cm PCL and 5.5 kg, respectively. We infrequently observed neonates in May, June, and September with size range 39.8–55.5 cm PCL. Enforcement of management regulations, difficult access to the refuge for fishers and other user groups, and isolation from human settlements are factors that help maintain nearly pristine conditions in La Salina Wildlife Refuge. The size/age structure of lemon sharks likely represents a population unaltered by human influence. We recommend our study be expanded to contribute to shark conservation and management as outlined in Cuba’s National Plan of Action for sharks.

Increasing marine ecosystems conservation linking marine protected areas and integrated coastal management in southern Cuba

The southern archipelagos of Cuba comprise important ecosystems of mangrove, seagrass beds, and coral reefs of regional significance. Biodiversity and fisheries stocks in this area experienced a severe decline due to a combination of factors (overfishing, habitat degradation, climate change). This work presents the main impacts of the project “Southern Archipelagos”, led by the National Center of Protected Areas of Cuba and funded by GEF, between 2009 and 2015 and the trends of the indicators of success. The project contributed to the conservation of marine biodiversity in Cuba through the creation of 12 new marine protected areas (MPAs). “Southern Archipelagos” facilitated the inclusion of the new and existing MPAs in Integrated Coastal Management Zones (ICMZs), thus contributing to buffering the impacts of productive activities and strengthening the integration between the conservation and productive sectors. Studies were conducted to characterize the MPAs and monitoring programs for priority species and ecosystems were implemented, increasing the knowledge available for decision-making about marine species and ecosystems in the region. To guarantee the financial sustainability of MPAs, a strategy for sustainable tourism was developed and a series of studies on the economic value of the goods and services offered by ecosystems were conducted. Different training programs for local leaders, MPAs workers and workers of productive sectors were organized. Sustainable productive alternatives were implemented in several communities diversifying the economic activities of local people. As a result, revenues from a representative sample of 12 MPAs of the project increased in the two currencies that are managed in Cuba.

CCAF-DB: the Caribbean and Central American active fault database

Abstract. A database of ∼250 active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the Global Earthquake Model (GEM) Foundation's Caribbean and Central American Risk Assessment (CCARA) project. The dataset is available in many vector GIS formats and contains fault trace locations as well as attributes describing fault geometry and kinematics, slip rates, data quality and uncertainty, and other metadata as available. The database is public and open source (available at: https://github.com/GEMScienceTools/central_am_carib_faults, last access: 23 March 2020), will be updated progressively as new data become available, and is open to community contribution. The active fault data show deformation in the region to be centered around the margins of the Caribbean plate. Northern Central America has sinistral and reverse faults north of the sinistral Motagua–Polochic fault zone, which accommodates sinistral Caribbean–North American relative motion. The Central Highlands in Central America extend east–west along a broad array of normal faults, bound by the Motagua–Polochic fault zone in the north and trench-parallel dextral faulting in the southwest between the Caribbean plate and the Central American forearc. Faulting in southern Central America is complicated, with trench-parallel reverse and sinistral faults. The northern Caribbean–North American plate boundary is sinistral off the shore of Central America, with transpressive stepovers through Jamaica, southern Cuba and Hispaniola. Farther east, deformation becomes more contractional closer to the Lesser Antilles subduction zone, with minor extension and sinistral shear throughout the upper plate, accommodating oblique convergence of the Caribbean and North American plates.

Biología reproductiva de Pterois volitans en la Reserva de la Biosfera Baconao, sur de Cuba

Background: Pterois volitans Linnaeus 1758 is an invasive exotic species established in the Atlantic and Caribbean, threatening the native marine biodiversity. It has led to reduced recruitment and biomass of small reef fish of ecological interest, altering the fish community structure by reducing the number of herbivores. In Cuba, it was first reported in 2007. Goals: This research aims to characterize the reproductive biology of P. volitans in the western part of the Baconao Biosphere Reserve, in southern Cuba. Methods: Sampling was carried out monthly from April 2012 to May 2013 (n = 535 fish). Total length (LT, cm), total mass (MT, g), and weight of the liver, gonads, and abdominal fat were recorded for each individual. To analyze spawning, the gonadosomatic (IG) and hepatosomatic indices (IH) were determined. Results: Mean size and weight of adults were 26.8 cm and 290.9 g, respectively. The size structure revealed that females are dominant in lengths of 22-31 cm, whereas males dominate from 31 cm onwards. The sex ratio was 1:1. IG showed seasonal spawning peaks between March and May 2013. No significant differences were observed amongst monthly means, but IH monthly means and monthly rates of abdominal fat showed significant differences. The size at first maturity was 30.07 cm in males and 26.2 cm in females. Conclusions: The results of this study suggest that the lionfish P. volitans shows an asynchronous reproductive cycle characterized by high gonadal index values during the breeding season and an inverse trend of IH and IF, suggesting that the liver and body fat store nutrients for use in reproduction.

Late Quaternary uplift along the North America-Caribbean plate boundary: Evidence from the sea level record of Guantanamo Bay, Cuba

The tectonic setting of the North America-Caribbean plate boundary has been studied intensively, but some aspects are still poorly understood, particularly along the Oriente fault zone. Guantanamo Bay, southern Cuba, is considered to be on a coastline that is under a transpressive tectonic regime along this zone, and is hypothesized to have a low uplift rate. We tested this by studying emergent reef terrace deposits around the bay. Reef elevations in the protected, inner part of the bay are ∼11–12 m and outer-coast, wave-cut benches are as high as ∼14 m. Uranium-series analyses of corals yield ages ranging from ∼133 ka to ∼119 ka, correlating this reef to the peak of the last interglacial period, marine isotope stage (MIS) 5.5. Assuming a span of possible paleo-sea levels at the time of the last interglacial period yields long-term tectonic uplift rates of 0.02–0.11 m/ka, supporting the hypothesis that the tectonic uplift rate is low. Nevertheless, on the eastern and southern coasts of Cuba, east and west of Guantanamo Bay, there are flights of multiple marine terraces, at higher elevations, that could record a higher rate of uplift, implying that Guantanamo Bay may be anomalous. Southern Cuba is considered to have experienced a measurable but modest effect from glacial isostatic adjustment (GIA) processes. Thus, with a low uplift rate, Guantanamo Bay should show no evidence of emergent marine terraces dating to the ∼100 ka (MIS 5.3) or ∼80 ka (MIS 5.1) sea stands and results of the present study support this.

Microcycas: An Endangered Genus

Gymnosperms are the plants of always of the great values, they are characterised by the naked seeds without fruits, they have the great evolutionary values, whole gymnosperms are presented by the three lines of the evolution among them cycadales liens of the evolution are the living fossils, whole this liens contains the 11 genera with the very narrow and the restricted kinds of the distribution, they are at the junction of the extinction, among the 11 genera many have the very endemic population in some restricted part of the world, initially they were consumed by the local population for the variety of the purposes but now whole of the order needs the conservation and the protection, according to the IUCN norms and the other means. In this review article we are working on the one of the cycadales entitled as the MICROCYCAS, this is the monotypic genus with the one species termed as the Microcycas calocoma, southern cuba is the endemic point of the Microcycas and now by the IUCN version the species has been declared as the critically endangered.

Features and variability of the Cuban Countercurrent in the Yucatan Basin, Caribbean Sea

The Cuban Countercurrent (CCC), along with the Yucatan Current, forms part of the Yucatan Basin circulation system, but it has not been well described and its connection to the system of currents in the Caribbean Sea has not been studied. Based on altimetry data (1993–2009) and the MERCATOR three-dimensional assimilation model (2007–2009), the CCC was observed flowing ~1000 km from the eastern Yucatan Channel to Jamaica and to have a width of ~150 km. Off southern Cuba, the mean velocity was 0.20 m s–1 at the surface and 0.05 m s–1 at 1000 m depth. The CCC transported ~3.5 Sv when it passed through the Yucatan Channel towards the Caribbean Sea, where ~1.6 Sv was recorded south of Cuba. During its annual cycle, the CCC weakened from December to February (0–250 m) and in the summer its magnitude intensified slightly, reaching 0.35 m s–1 in August, due to the increase in water temperature of the Atlantic warm pool. Consequently, the sea level rose in the center of the Yucatan Basin and the pressure gradient increased along the Cuban coast, producing an increase in zonal velocity (0.1 m s–1) and transport (2–3 Sv; r = 0.90). Its connection to the Caribbean current system demonstrated the importance of its study.

Surface wind variability and its implications for the Yucatan basin‐Caribbean Sea dynamics

Sea surface wind data from the QuikSCAT satellite and two meteorological stations collected over 1 decade (1999–2008) were used to study the dominant time scales of the wind regime in the Yucatan basin. Wind data were used to quantify its implications on regional hydrodynamics by evaluating Ekman pumping and Ekman transport. The annual cycle of surface wind revealed different features than the Caribbean wind regime with a relative wind stress maximum observed in the Yucatan basin in June caused by the Caribbean low‐level jet. The strongest wind stress occurred during November presumably due to the collapse of the Atlantic warm pool. This feature provides new evidence of the importance of local atmosphere‐ocean coupling. Synoptic scale variability was detected during fall and winter, leaving spring and summer almost free from these activities. Empirical orthogonal functions revealed three dominant time scales of variability: an annual scale in mode 1 (46.3% of the total variance), a synoptic scale in mode 2 (27.7%), and a semiannual scale in mode 3 (6.4%). The third mode featured extreme pulses (six tropical storms and nine hurricanes). Ekman transport was found to contribute the most (93%) to total transport, whereas Ekman pumping contributed only 7%. However, upwelling induced by Ekman pumping persisted during some synoptic pulses, underscoring the importance of tropical storms and hurricanes. Offshore Ekman transport over the continental shelf north of the Yucatan Peninsula favored upwelling all year long. Onshore transport toward the coasts of southern Cuba and the eastern Yucatan Peninsula favored downwelling.

Cubadeutella cavernicola, a new genus and species of Caprellidae (Crustacea: Amphipoda) from Cuba

Cubadeutella cavernicola new genus, new species, is described based on specimens collected from a cave of southern Cuba, Caribbean Sea. Cubadeutella new genus is close to Deutella, but presents a higher number of plesiomorphic characters: the number of articles in antenna 1 is higher in Cubadeutella (20–22) than in Deutella (7–14); the flagellum of antenna 2 in Cubadeutella is 4 articulate while it is 2-articulate in Deutella and the pereopods 3 and 4 are 4-articulate in Cubadeutella and 1 or 2-articulate in Deutella. Cubadeutella, together with Triantella and Protellina are the only genera in the Caprellinae with the flagellum of antennae 2 more than 2-articulate, and the presence of 4-articulate pereopod 3 and 4 is unique in the Caprellidae.

An Intercomparison of Observational, Reanalysis, Satellite, and Coupled Model Data on Mean Rainfall in the Caribbean

Abstract This study examines the spatial variability of mean annual rainfall in the Caribbean in the satellite era 1979–2000. Intercomparisons of gridded rainfall fields from conventional stations, satellite estimators, reanalysis products, and coupled general circulation models (CGCMs) are made, with a focus on the Antilles island chain and their land–sea transitions. The rainfall products are rated for their ability to capture a number of key features, including (i) topographically enhanced precipitation over the larger western Antilles islands of Cuba, Jamaica, Hispanola, and Puerto Rico; (ii) the rain shadow west of Hispanola; (iii) the two dry zones where SSTs are low: north of Venezuela and north of the Lesser Antilles; and (iv) the wet axis extending north of Trinidad. The various monitoring and modeling systems produce gridded rainfall fields at resolutions from 50 to 280 km, from station reconstructions, satellite estimates, blended and reanalysis products, and CGCM climatologies with respect to surface forcing fields. Wet and dry biases were found in many of the reanalysis and satellite products, respectively—either over the whole Caribbean or in a certain sector. The intercomparison found some measure of consensus, but no single product is without discrepancy. High-resolution passive microwave satellite rainfall estimates [Climate Prediction Center’s multisaltellite passive microwave, IR morphed product (cMOR)] appear “most representative”; however, the climatology is short (2003–07) and the field is generally drier than the consensus. Of the conventional products, decadal variability of climate interpolated rain gauges (DEKL), World Climate Research Programme’s (WCRP) blended rain gauges, the Comprehensive Ocean–Atmosphere Data Set (COADS), and an operational climate anomaly monitoring system of NCEP (CAMS) perform well. Among the satellite estimators, the Global Precipitation Climatology Project’s blended gauge and IR satellite (GPCP) and outgoing longwave radiation (OLR) capture the key features and ocean–island transitions. The Center for Ocean–Land–Atmosphere Studies [COLA; the coupled model, part of the Coupled Model Intercomparison Project (CMIP, phase 3)] and the climate forecast system of the NCEP (CFS) models perform reasonably, but NCAR’s Parallel Climate Model (PCM; the CGCM’s historical run of CMIP3) fares poorly. The version 2 hindcast of the operational Medium-Range Forecast (MRF) weather prediction model (REAN) captures the smaller wet zones and topographically enhanced features, but it does not handle the broad oceanic dry zones well, as the input from the operational climate data assimilation system of NCEP (CDAS) has a wet bias. Of the various key rainfall features, high rainfall over southern Cuba and the rain shadow west of Hispanola are poorly handled by most products. The wet axis north of Trinidad and the dry zone north of Venezuela are well represented in many climatologies.

Tectonic and Kinematic Regime along the Northern Caribbean Plate Boundary: New Insights from Broad-band Modeling of the May 25, 1992, M s = 6.9 Cabo Cruz, Cuba, Earthquake

—On May 25th, 1992, an M s = 6.9 earthquake occurred off the southwestern tip of Cuba, along the boundary between the Caribbean and North American plates. This earthquake was the largest to strike southern Cuba since 1917 and the largest ever recorded in that region by global seismic networks. It is therefore a key element for our understanding of the tectonic and kinematic regime along the northern Caribbean plate boundary. In order to test the previously proposed source parameters of the Cabo Cruz earthquake and to better constrain its focal mechanism, we derived a new set of source parameters from unfiltered broad-band teleseismic records. We used a hybrid ray tracing method that allows us to take into account propagation effects of seismic waves in a realistic crustal model around the source. Our solution is consistent with the long-period focal mechanism solution of Virieux et al. (1992). Our solution also models the higher frequency crustal and water layer phases. The primarily strike-slip focal mechanism has a small thrust component. Its shows an east-west trending nodal plane dipping 55° to the north that we interpret as the rupture plane since it corresponds to the geometry of the major active fault in that area. The displacement on this plane is a left-lateral strike-slip combined with a small amount of southward thrust. The result is in good agreement with the active tectonic structures observed along the Oriente fault south of Cuba. The small thrust component demonstrates that, contrary to prior belief, the transpressive regime extends along this whole segment of the Caribbean/North American plate boundary. Together with historical seismicity, it suggests that most of the stress accumulated by the Caribbean/North American plate motion is released seismically along the southern Cuban margin during relatively few but large earthquakes.

From transcurrent faulting to frontal subduction: A seismotectonic study of the Northern Caribbean Plate Boundary from Cuba to Puerto Rico

Recent marine and onland geophysical and geological investigations along the northern Caribbean plate boundary call for a review of its tectonic interpretation, in the light of a new compilation of the seismological data avalaible from Cuba to Puerto Rico. We show that the shallow seismicity in the northeastern Caribbean is concentrated along an east‐west trending lineament corresponding to the trace of the major strike‐slip fault system. The most intense seismicity is located around restraining bends such as southern Cuba and northern Hispaniola. The stress and strain distribution deduced from focal mechanisms and microtectonic analysis lead us to infer a small N‐S convergence component associated with the major eastward strike‐slip motion of the Caribbean plate versus North America. Earthquake distribution and focal mechanisms suggest the existence of a lithospheric slab inherited from the frontal subduction under the Lesser Antilles diping down under Puerto Rico and eastern Hispaniola. We propose a model in which this slab is disconnected from the Atlantic oceanic lithosphere by transcurrent faulting along the plate boundary.

The avifauna of the cayerias of southern Cuba, with the ornithological results of the Paul Bartsch Expedition of 1930

The avifauna of the cayerias of southern Cuba, with the ornithological results of the Paul Bartsch Expedition of 1930

Investigations of the Benthos of Mangrove Coastal Lagoons in Southern Cuba

AbstractBenthic studies were undertaken in two mangrove‐lagoons on the south coast of Cuba. Both lagoons are approximately 30–50 cm deep and the tidal range is 15–20 cm. There is little influx of fresh water, and the lagoons are normally euhaline. Most of the lagoon bottom is not colonized by plants, although filamentous algae (Cladophora and Enteromorpha spp.) and Thalassia testudium grow in a few places. Meiobenthic organisms account for 92% of the invertebrates in the benthic zone of the lagoon. The five most common taxa (Nematoda, Copepoda, Tanaidacea, Oligochaeta, Polychaeta) account for 88–94% of the total number of individuals in Tolete Lagoon and in Basto Lagoon the five most common taxa (Nematoda, Copepoda, Ostracoda, Amphipoda, Polychaeta) account for 97–98%. Biomasses were 26.6 g/m2 in Tolete and 20.2 g/m2 in Basto Lagoon. The dominant taxon on the roots of Rhizophora mangle is Crustacea (Balanus eburneus, B. recurvus and Corophium insidiosum), accounting for over 60% of the total number of individuals. They are followed by molluscs (Crassostrea rhizophora) and the polychaetes (serpulids).

Cenozoic Basin Development in Hispaniola: ABSTRACT

Four distinct generations of Cenozoic basins have developed in Hispaniola (Haiti and Dominican Republic) as a result of collisional or strikeslip interactions between the North America and Caribbean plates. First generation basins formed when the north-facing Hispaniola arc collided with the Bahama platform in the middle Eocene; because of large post-Eocene vertical movements, these basins are preserved locally in widely separated areas but contain several kilometers of arc and ophiolite-derived clastic marine sediments, probably deposited in thrust-loaded, flexure-type basins. Second generation basins, of which only one is exposed at the surface, formed during west-northwesterly strike-slip displacement of southern Cuba and northern Hispaniola relative to central Hispani la during the middle to late Oligocene; deposition occurred along a 5-km (3-mi) wide fault-angle depression and consisted of about 2 km (1 mi) of submarine fan deposits. Third generation basins developed during post-Oligocene convergent strike-slip displacement across a restraining bend formed in central Hispaniola; the southern 2 basins are fairly symmetrical, thrust-bounded ramp valleys, and the third is an asymmetrical fault-angle basin. Fourth generation basins are pull-aparts formed during post-Miocene divergent strike-slip motion along a fault zone across southern Hispaniola. As in other Caribbean areas, good source rocks are present in all generations of basins, but suitable reservoir rocks are scarce. Proven reservoirs are late Neogene shallow marine and fluvial sandstones in thi d generation basins. End_of_Article - Last_Page 503------------

A Revision of Samolus ebracteatus (sensu lato) (Primulaceae)

A revision of the Samolus ebracteatus-cuneatus complex is presented recognizing five varieties of S. ebracteatus: S.e. var. ebracteatus from the Caribbean and Florida; var. alyssoides from coastal Texas to Mexico; var. cuneatus from inland Texas to Nevada and central Mexico; var. coahui- lensis (var. nov.) from central Coahuila; and var. breviflorus (var. nov.) from southern Mexico. Preparation of a treatment of Samolus L. for M. C. Johnston's Chihuahuan Desert Flora has lead to this revision of the entire Samolus ebracteatus-cuneatus complex. This was necessary to properly accommodate a new taxon from central Coahuila. Three taxa have been described within this complex. All are relatively similar in vegetative and floral characteristics (Fig. 1) and distinguished from other species in the genus by the absence of bracts on pedicels and absence of distinct epipetalous staminodia attached to the corolla tube and alternate to its lobes (Pax and Knuth, 1905). Samolus ebracteatus was described by Kunth (1815) from a collection by Humboldt and Bonpland from southern Cuba near Batabano, south of Havana. While the original description and illustration make no note of stipitate glands, study of other specimens from the type locality indicate that material from Cuba, Florida, and the West Indies are all similar and characterized by stipitate glands on pedicels, inflorescence axes, and moderately large, mostly pinkish-white corollas. A second taxon, S. alyssoides was described by Heller (1895) from a sandy habitat along the east coast of Texas. He distinguished the new species from S. ebracteatus on the basis of growth habit, emphasing its erect, more compact nature in contrast to a more leafy, spreading habit of S. ebracteatus. He also noted the new taxon had glaucous leaves and larger flowers than S. ebracteatus. Though not noted by Heller, S. alyssoides differs from Floridian-West Indian populations of S. ebracteatus by the lack of stipitate glands on pedicels and inflorescence axes. In that paper, Heller (1895) also cites a collection of S. ebracteatus from near Kerrville, Texas which he apparently had used to contrast his S. alyssoides. He distributed the specimens of that collection identified as a new species, but never published the new name. In 1897 Small cited Heller's Kerrville specimen as the type of a new species S. cuneatus noting it could be distinguished from S. ebracteatus and S. alyssoides by its smaller flowers measuring only 4-5 mm (not 6-9 mm) in breadth and by its more cuneate (not suborbicular) petal lobes. Like the Floridian-West Indian specimens of S. ebracteatus it also has stipitate glands on the pedicels and inflorescence axes.

Geophysical study of the Cayman Trough

The deepest water and the shallowest depths to mantle within the Caribbean Sea south of the Caribbean Island arc occur in the Cayman (or Bartlett) trough. The thin crust, indicated by the seismic refraction studies and by gravity data, suggests that the trough is a feature produced by extension with concomitant upwelling of dense mantle material to more shallow depths. During cruises of the R. V. Chain in 1965 we investigated the Cayman trough, utilizing continuous bathymetric, gravity, and magnetic measurements. These investigations confirm that in addition to the Bartlett and Oriente deeps, which occur south of the Cayman Islands and Cuba, respectively, there is a depression about 5700 meters deep on the south side of the Cayman trough west of 79°30′W. Negative free-air gravity anomaly values occur over the deeps of the Cayman trough, and computed structure models show that there are mass deficiences beneath the deeps and mass excesses beneath the adjacent ridges. The deeps and adjacent ridges are not in isostatic equilibrium, and it appears that the rising of portions of the crust is here a concomitant aspect of the sinking of adjacent portions of the crust. The width of the individual structures that are out of isostatic equilibrium is about 40 km. All the gravity profiles show a hump in the Bouguer anomaly curve across the trough. The computed structure model confirms that the rise in the mantle-crust interface extends across the width of the trough and is centered on the axis of the trough. The axis of the Bouguer high clearly does not cross the Windward Passage between Cuba and Haiti but instead curves eastward and enters the Gonave Gulf between the northern and southern peninsulas of Haiti. Steps of about 200 to 400 γ in the magnetic field on the sides of the trough can be traced along almost the entire length of the Cayman trough. These steps generally occur on the southern slope of the Cayman trough and on the northern side of the Cayman ridge. Lithofacies maps of southern Cuba suggest that the initiation of the extension that produced the trough began in the Paleocene or earlier, and studies in Guatemala suggest that extension was active during the Cretaceous. The much slower extension rate and the lack of characteristic central magnetic anomalies suggest that the Cayman trough probably resulted from processes different from the ones producing the world rift system. Rather than a direct manifestation of an upwelled convection cell, the trough may be a tensional feature associated with failure of the crust under conditions of an eastward drift of the Caribbean region. It is suggested that the rift structure is now growing toward the east along the Enriquillo-Cul de Sac trough in southern Hispaniola. It is also concluded that the Cayman trough structure is not a westward continuation of the structure that produces the Puerto Rico trench negative free-air anomaly belt.