Roldán A ValverdeSoutheastern Louisiana University · Department of Biological Sciences
Roldán A Valverde
PhD
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64
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August 1996 - March 2001
August 1987 - December 1988
Publications
Publications (64)
When necessary, sea turtles are held captive for veterinarian care and research purposes. Protocols and basic guidelines have been described for husbandry of sea turtles with veterinarian needs but not considering physiological indicators of animal welfare. Because all sea turtle are imperiled species, monitoring their welfare is important. The aim...
Sea turtles are vulnerable to climate change since their reproductive output is influenced by incubating temperatures, with warmer temperatures causing lower hatching success and increased feminization of embryos. Their ability to cope with projected increases in ambient temperatures will depend on their capacity to adapt to shifts in climatic regi...
Knowing the age of individuals in a population is crucial to devise appropriate conservation strategies, especially on endangered long-lived species such as sea turtles. Sea turtles do not have external morphologic characters that indicate their age; therefore, age has been estimated by indirect methods such as biometric measurements or skeletochro...
Nancite is a fully protected beach within the Guanacaste Conservation Area, Costa Rica where olive ridley ( Lepidochelys olivacea ) sea turtles nest in synchronous mass‐nesting events known as arribadas. Arribadas decreased in magnitude at this beach by approximately 90% during the period 1971–2007 due to unknown causes. The total count estimate of...
Trends in abundance of different life stages present important opportunities to manage the conservation of threatened species. For marine turtles, most trend assessments are based on long-term monitoring of nesting aggregations, which provides critical information on rookery dynamics across years. Tortuguero, Costa Rica, is the largest nesting colo...
Vitellogenin (VTG), an egg yolk precursor, is abnormally produced by male and juvenile oviparous species upon exposure to estrogens. Plasma VTG in loggerhead sea turtles (Caretta caretta) helped us understand their reproductive maturation and investigate it as a biomarker of contaminant exposure. VTG presence was screened in plasma from 404 loggerh...
Vitellogenesis is the process in which female oviparous vertebrates synthesize the protein vitellogenin to develop egg yolk. In some species, vitellogenin has been used to investigate reproductive status, as a biomarker of clutch size and nesting frequency, and as a biomarker of exposure to endocrine-disruptive chemicals. The Diamond-backed Terrapi...
Although hybridization processes in the Cheloniidae family have been documented since the 19th century, detailed reports of these occurrences are scarce. Therefore, the record of a hybridization between Green Sea Turtles (Chelonia mydas) and Hawksbill Sea Turtles (Eretmochelys imbricata) signifies an important event. In this study, we report the th...
Tortuguero, Costa Rica is considered the second largest green turtle (Chelonia mydas) rookery in the world. By 1950, Tortuguero was one of the sites with the greatest take of green turtles in the Caribbean. Currently, Tor-tuguero is a worldwide example for ecotourism-based on sea turtle conservation. However, illegal take of nesting turtles still o...
Costa Rica is considered a hot spot for biodiversity and wildlife conservation in Central America, and sea turtles are a good example of this. Largely distributed along both the Caribbean and Pacific coast, adult females of five of the seven extant sea turtle species select beaches on both coasts as their breeding sites. Although Green Sea Turtles...
Costa Rica hosts two renowned olive ridley (Lepidochelys olivacea) arribada beaches: Nancite and Ostional. In addition, the country hosts a third nascent arribada beach in Corozalito. We documented the frequency of arribada events in Corozalito (9°50′55.40″ N; 85°22′ 47.67″ W) from 2008 to 2021 and the abundance of egg-laying females during 12 arri...
Understanding the timing of vitellogenesis is essential for identifying threats to the reproductive success of endangered oviparous vertebrate species, such as sea turtles. We measured concentrations of testosterone (T) and vitellogenin (VTG) in green sea turtles (Chelonia mydas) nesting at Tortuguero, Costa Rica, as biomarkers of ovarian developme...
The timing of reproductive cycles in reptiles is often linked to environmental correlates, including
temperature and photoperiod. The Diamondback Terrapin (Malaclemys terrapin) is a wide-ranging species that
occurs across multiple climatic regions over the eastern and Gulf coastal areas of the United States. Therefore,
the species may show variatio...
Endangered leatherback sea turtles (Dermochelys coriacea) are wide‐ranging, long‐distance migrants whose movements are often associated with environmental cues. We examined the spatial distribution and habitat use for 33 satellite‐tracked leatherbacks from nesting beaches on the Caribbean coast of Costa Rica and Panama from 2004 to 2018, an importa...
Estimates of illegal wildlife trade vary significantly and are often based on incomplete datasets, inferences from CITES permits or customs seizures. As a result, annual global estimates of illegal wildlife trade can vary by several billions of US dollars. Translating these figures into species extraction rates is equally challenging, and estimatin...
Sea turtles are among several hundred species whose sex is determined by incubation conditions during critical developmental periods. Consequently, these marine reptiles may be vulnerable to global climate change, and under the assumption of continued climate warming, numerous studies pose dire predictions for future populations based primarily on...
Frequently, stranded sea turtles require rehabilitation under controlled conditions. Currently, few publications have described the conditions under which rehabilitation is to take place, particularly with respect to the hatchling life stage. To address this paucity of data, we conducted some experiments to assist rehabilitating facilities assess t...
Tortuguero is a small Caribbean village of Costa Rica, where sea turtles have always played a central role in the culture and economy. Historically, Tortuguero based its economy on the exploitation of natural resources, including marine turtles. However, thanks to long term conservation efforts, policy modifications and a change in the mindset of t...
Sea turtle conservation and research efforts in Tortuguero, Costa Rica, began in the 1950s. Legislation protecting sea turtles and creating Tortuguero National Park (TNP) in the 1960 and 1970s caused the village economy to change, from natural resource exploitation to an economy based on ecotourism. Tourism increased in the park rapidly, and so did...
Jaguar (Panthera onca) predation on sea turtles occurs across the Americas; however, records are scattered and not frequently presented in terms of their potential effects on sea turtle populations. In this study, we documented Jaguar predation events on nesting sea turtles at Nancite Beach, Santa Rosa National Park, Costa Rica, between the 2009–20...
In species presenting long intervals between reproductive seasons, atmospheric-oceanic phenomena can affect the yearly number of individuals that become reproductively active. Sea turtles take multiyear intervals between reproductive seasons, which are influenced by environmental processes affecting their nutrition. Atmospheric-oceanic phenomena af...
Important indicators of population health needed for large-scale sea turtle population recovery efforts include demographics, disease and mortality trends, condition indices, and baseline blood data. With this comprehensive health assessment of adult female green sea turtles
Chelonia mydas nesting on Juno Beach, Florida, USA, we (1) established bas...
During the mass nesting of olive ridley sea turtles, Lepidochelys olivacea, thousands of adult females aggregate offshore, then emerge from the ocean together to lay their eggs along small, specific stretches of coastline. Little is known about the mechanisms that underlie synchronization of mass nesting. As a first step towards identifying environ...
Marine turtles are challenging species to protect because they occur over large geographic scales. Tagging individual turtles at nesting beaches and foraging areas, and the resulting mark-recapture data sets have gradually enabled us to understand their migratory behaviour and dispersal. Within the Caribbean region, several turtle tagging projects...
Oceanic dispersal characterizes the early juvenile life‐stages of numerous marine species of conservation concern. This early stage may be a ‘critical period’ for many species, playing an overriding role in population dynamics. Often, relatively little information is available on their distribution during this period, limiting the effectiveness of...
First report of leusistic green turtle females successfully nesting at Tortuguero, Costa Rica. evaluation of their nesting success and assessment of their progeny.
Anuran vocalization is one of the most energetically expensive behaviors recorded in vertebrates. To sustain this
behavior, circulating hormones in male frogs must act to promote calling behavior while mobilizing energy reserves.
We hypothesize that this is accomplished through the actions of testosterone (T) and corticosterone (CORT). T is
thought...
Here we report on a newly discovered nesting population of east Pacific green turtles (Chelonia mydas) in northwest Costa Rica at San José Island, Murcíelago Archipelago, that rivals those of Mexico and the Galápagos Islands, Ecuador. A total of 1232 individual green turtles were tagged over 4 nesting seasons (2012–2013 to 2015–2016). Mean (± SD) a...
The reproductive cycles of turtles are linked to environmental factors, such as photoperiod and temperature. Currently, the reproductive physiology of diamondback terrapins (Malaclemys terrapin) is poorly understood, especially in Gulf of Mexico. The reproductive cycles of terrapins are thought to follow typical seasonal patterns. However, latitudi...
This study describes records of scavenging behaviour of pumas Puma concolor at jaguar Panthera onca kills in Costa Rica. We set camera traps at fresh carcasses predated by jaguars on Nancite beach between March 2010 and July 2017. Pumas were recorded at four out of 70 monitored kills. Jaguars interacted with the carcasses mainly at night while puma...
Five species of sea turtles occur in the Gulf of Mexico: Kemp’s ridley (Lepidochelys kempii), loggerhead (Caretta caretta), green (Chelonia mydas), leatherback (Dermochelys coriacea), and hawksbill (Eretmochelys imbricata). Nesting, distribution, abundance, habitat, and life history information has been reviewed for each sea turtle species in the G...
We report here new sites where jaguars Panthera onca prey upon sea turtles in Costa Rica. We conducted carcass counts (n = 228) along eight beaches located in Santa Rosa National Park NP, which makes part of Guanacaste Conservation Area, between June and August 2016. The olive ridley sea turtle Lepidochelys olivacea was the most common species pred...
Kemp’s Ridley Sea Turtle (Lepidochelys kempii) conservation practices permitted by National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS), under authority of the U.S. Endangered Species Act of 1973, include translocations in which eggs or turtles are taken into captivity for various reasons and intervals, and turtles ar...
Vitellogenin (VTG) is an egg yolk-precursor protein that serves as a nutrient source for developing embryos in oviparous vertebrates. The hormonal control of this protein has been studied in a variety of taxa, but details about the dynamics of this protein remain to be elucidated in sea turtle species. To investigate the dynamics of VTG in a multi-...
Ostional Beach, Costa Rica, supports a large mass nesting (arribada) aggregation of Olive Ridley Sea Turtles (Lepidochelys olivacea). A large number of egg clutches is lost to egg harvest and to nest destruction by nesting females after every arribada. Accordingly, the purpose of our study was to generate estimates of the net number of clutches lef...
![Fig 1. Mean (± SE) hatching success [hatchlings clutch-1 (%)] for...](profile/Roldan-Valverde/publication/272817423/figure/fig10/AS:342107354091520@1458576157172/Mean-SE-hatching-success-hatchlings-clutch-1-for-nests-relocated-into_Q320.jpg)
Several studies have suggested that significant embryo mortality is caused by microbes,
while high microbial loads are generated by the decomposition of eggs broken by later nesting
turtles. This occurs commonly when nesting density is high, especially during mass
nesting events (arribadas). However, no previous research has directly quantified mic...
Sea turtle hatching success at mass nesting beaches is typically lower than at solitary nesting beaches, presumably due in part to high rates of microbial metabolism resulting from the large input of organic matter from turtle eggs. Therefore, we tested the hypothesis that hatching success varies across areas of the beach in conjunction with differ...
Vitellogenin is the egg yolk precursor protein produced by oviparous vertebrates. As endogenous estrogen increases during early reproductive activity, hepatic production of vitellogenin is induced and is assumed to be complete in female sea turtles before the first nesting event. Until the present study, innate production of vitellogenin has not be...
The olive ridley sea turtle (Lepidochelys olivacea), a species listed by the International Union for Conservation of Nature as vulnerable, is characterized by its mass-nesting behavior, also known as arribada. For decades, this phenomenon has facilitated the utilization of this species by coastal communities, much of it illegally. At Ostional beach...
Agouti-related protein (AgRP), is a signaling peptide that affects feeding behavior, energy homeostasis, and has also been shown to stimulate the hypothalamic-pituitary-adrenal axis. The purpose of this study was to determine the effects of 90 min of treadmill exercise on circulating AgRP concentrations and the relationship of AgRP responses to cor...
Amylin is a pancreatic β-cell peptide that facilitates the regulation of blood glucose concentration by inhibiting release of glucagon and modulating gastric emptying. Prolonged exercise may alter amylin and aid in the maintenance of blood glucose concentration; however, no studies have investigated the effects of prolonged exercise on amylin.
This...
Morphological and molecular studies have inferred multiple hypotheses for the phylogenetic relationships of Testudines. The hypothesis that Testudines are the only extant anapsid amniotes and the sister taxon of diapsid amniotes is corroborated by morphological studies, while the hypothesis that Testudines are diapsid amniotes is corroborated by mo...
Full-length cDNAs for thyrotropin β (TSHβ) and glycoprotein hormone α (GSUα) subunits were cloned and sequenced from the red drum (Sciaenops ocellatus). The cDNAs for TSHβ (877 bp) and GSUα (661 bp) yielded predicted coding regions of 126 and 94 amino acid proteins, respectively. Both sequences contain all invariant cysteine and putative glycosylat...
Hatching success in olive ridley mass nesting arribada beaches is typically low. We conducted a short study to understand whether incubation temperature in dry months accounts for exceedingly low hatching success at Ostional Beach, Costa Rica, a mass nesting rookery. We measured in situ incubation temperatures in nests from 4 arribadas recorded in...
Although the olive ridley sea turtle (Lepidochelys olivacea) is the most abundant sea turtle in the world, the species has exhibited a significant decrease in the size of arribadas at Nancite Beach, Costa Rica, since its discovery in 1970. In the present study, we compiled data on number of nesting females per arribada from previous authors for the...
Olive ridley sea turtles (Lepidochelys olivacea) distribute widely throughout Eastern Pacific (EP) waters. During reproduction these animals aggregate near coastal waters where they may be exposed to indus-trial or agrochemical environmental pollutants that may disrupt the endocrine system of these reptiles. One group of compounds of concern is the...
Corticotropin-releasing hormone (CRH) plays multiple roles in vertebrate species. In mammals, it is the major hypothalamic releasing factor for pituitary adrenocorticotropin secretion, and is a neurotransmitter or neuromodulator at other sites in the central nervous system. In non-mammalian vertebrates, CRH not only acts as a neurotransmitter and h...
Corticotropin-releasing hormone (CRH) plays a key role in the regulation of responses to stress. The presence of a high affinity binding protein for CRH (CRH-BP) has been reported in mammals. We have characterized the biochemical properties and expression of CRH-BP in the South African clawed frog, Xenopus laevis. Apparent inhibition constants (Ki[...
Adrenocortical responsiveness to turning stress was examined in wild, reproductively-active olive ridley sea turtles (Lepidochelys olivacea) in relation to their mass nesting (arribada) behavior. We hypothesized that the high sensitivity threshold (HST) observed in ovipositing sea turtles is associated with a diminished sensitivity of the hypothala...
Adrenocortical responsiveness to turning stress was examined in wild, reproductively-active olive ridley sea turtles (Lepidochelys olivacea) in relation to their mass nesting (arribada) behavior. We hypothesized that the high sensitivity threshold (HST) observed in ovipositing sea turtles is associated with a diminished sensitivity of the hypothala...
Migratory marine turtles are extremely difficult to track between their feeding and nesting areas, and the link between juvenile
and adult habitats is generally unknown. To assess the composition of a feeding ground (FG) population of juvenile green turtles
(Cheloniamydas Linnaeus), mitochondrial DNA control region sequences were examined in 80 pos...
Estimates of the number of nesting female turtles are illustrated, using an instanta- neous count (IC) procedure modified by sampling in space as well as time. Variations of the modified IC procedure are shown to be equivalent to four methods, including the strip transect (in time), the line intersect (in time), and quadrat sampling (in time), depe...
Includes bibliographical references: p. 133-147. Vita. Thesis (Ph. D.)--Texas A&M University, 1996. "Major Subject: Zoology".
Questions
Questions (2)
I use Cyaman Chm ELISA kits (https://www.caymanchem.com/app/template/Product.vm/catalog/582701). The testosterone kit has shown to be unreliable. The results have not been reproducible. A large kit works only the first time, but then within a few days it stops working. Specifically, either the standard curve falls apart, the assay does not develop well, the samples come up with very high background, etc. In short, the problems are not consistent. I would love to hear from someone who has recently run this kit successfully. Thanks
My understanding is that Federal agencies are not funding much of this. Is this true? Thanks
