James Gelsleichter

University of North Florida | UNF · Department of Biology

In the coastal waters of the southeastern United States, the black-tip shark (Carcharhinus limbatus) is targeted by recreational anglers and is currently one of the most often captured large coastal shark species. We estimated postrelease mortality (PRM) rates for blacktip sharks captured on rod and reel by shore-based and charter-boat-based fisher...

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in rel...

The present study examined temporal changes in plasma sex hormone concentrations and the morphology and histology of reproductive organs in mature northwest Atlantic (NWA) bonnetheads Sphyrna tiburo L. to characterize reproductive cycle, breeding periodicity and fertility in this still poorly studied population. Progressive increases in testis widt...

Metals occur naturally in the environment; however, anthropogenic practices have greatly increased metal concentrations in waterways, sediments, and biota. Metals pose health risks to marine organisms and have been associated with oxidative stress, which can lead to protein denaturation, DNA mutations, and cellular apoptosis. Sharks are important s...

The oceanic whitetip shark Carcharhinus longimanus is a widely distributed large pelagic shark species once considered abundant in tropical and warm temperate waters, but recently listed as Critically Endangered by the IUCN due to drastic population declines associated with overfishing. In addition to risks posed to its populations due to overexplo...

The integument plays essential roles in the structural support, protection, and hydrodynamic capability among fishes. Most research on shark skin has focused on the external epidermal layer, while the larger dermis anchoring the dermal denticles has been mostly ignored. Shark dermis is composed of two layers, the upper stratum laxum and the lower s...

Carolina hammerheads Sphyrna gilberti and scalloped hammerheads S. lewini are cryptic species with an overlapping distribution, and young-of-the-year (YOY) use similar coastal and estuarine nursery areas along the US Southeast coast. The diet of scalloped hammerheads has been widely studied throughout their global distribution; however, little is k...

Fisheries-independent data on the diversity, relative abundance, and demographic structure of poorly studied, threatened oceanic sharks are absent from much of the western North Atlantic Ocean, where multiple oceanic shark species have experienced significant population declines. Resource-limited management approaches require the identification of...

Oceanic whitetip sharks Carcharhinus longimanus aggregate at Columbus Point, Cat Island, The Bahamas, in at least April and May. We show that signs of putative mating activity (i.e. bite wounds) on mature females, which dominate the aggregation, are exceedingly rare at that time, but may be more common in July. Male plasma testosterone concentratio...

Animal behavior varies in response to capture between/within species and fisheries, and its expression may contribute to incidental mortality when behaviors result in physiological ramifications that cannot be resolved. However, this relationship between capture behavior and animal health is poorly understood, and it remains a logistical challenge...

One of the best studied global “hot spots” for ecological mercury (Hg) contamination is south Florida (USA), where elevated Hg concentrations in environmental media and regional wildlife were first described over thirty years ago. While Hg contamination has lessened in this region, it is still critical to monitor Hg uptake and potential risks in so...

The scalloped hammerhead (Sphyrna lewini) and its cryptic congener, Carolina hammerhead (S. gilberti), are sympatrically distributed in the western North Atlantic Ocean. Because the species are indistinguishable based on external morphology, little research focused on Carolina hammerheads exists. In this study, the distribution of Carolina hammerhe...

Invasive lionfish (Pterois volitans/miles) pose a serious threat to marine ecosystems throughout the western Atlantic Ocean and Caribbean Sea. The development of a fishery for lionfish has been proposed as a strategy for controlling populations; however, there is concern about consumption of this species by humans due to its high trophic position a...

The isotopic composition of tooth‐bound collagen has long been used to reconstruct dietary patterns of animals in extant and palaeoecological systems. For sharks that replace teeth rapidly in a conveyor‐like system, stable isotopes of tooth collagen (δ¹³CTeeth & δ¹⁵NTeeth) are poorly understood and lacking in ecological context relative to other no...

Female sperm storage (FSS) has been demonstrated to occur in representatives from all major vertebrate groups and has been hypothesized to have several possible adaptive benefits that may maximize reproductive success of its practitioners. However, while the range of taxa that exhibit FSS and its possible evolutionary benefits have received signifi...

1. The isotopic composition of tooth-bound collagen has long been used to reconstruct dietary patterns of animals in extant and paleoecological systems. For sharks that replace teeth rapidly in a conveyor-like system, stable isotopes of tooth collagen (δ13Ctooth & δ15Ntooth) are poorly understood and lacking in ecological context relative to other...

Invasive lionfish ( Pterois volitans/miles ) pose a serious threat to marine ecosystems throughout the western Atlantic Ocean and Caribbean Sea. The development of a fishery for lionfish has been proposed as a strategy for controlling populations; however, there is concern about consumption of this species by humans due to its high trophic position...

There has been a growing concern in recent years about the effects of anthropogenic noise due to pile driving on underwater wildlife. Current guidelines for mitigating hydroacoustic effects associated with these geotechnical events are based upon relatively simple transmission loss formulations. The advantage to these guidelines is that computing t...

Few published studies have examined whether the elevated concentrations of the nonessential toxic metal mercury (Hg) often observed in shark muscle also occur in the shark brain or whether Hg accumulation affects shark neurophysiology. Therefore, this study examined accumulation and distribution of Hg in the shark brain, as well as effects of Hg on...

Recent studies on shark assemblages on the northeast Florida and southeast Georgia coast (hereafter referred to collectively as the “First Coast”) have demonstrated differences in species and age‐class composition of catch from previously characterized estuaries and newly surveyed area beaches, demonstrating that these regions may provide a critica...

Many elasmobranchs display K-selected life history characteristics, making species-specific life history parameters critical to development of the most accurate stock assessment models. Age, growth, and maturity were examined for Finetooth Sharks, Carcharhinus isodon, in coastal waters of the Western North Atlantic Ocean (WNA) from Winyah Bay, Sout...

Genetic polyandry was assessed in 27 litters of Blacknose Shark (Carcharhinus acronotus) from genetically distinct populations in the U.S. Atlantic (19 litters) and eastern Gulf of Mexico (eight litters) using 23 polymorphic microsatellite loci. Two methods were used to estimate genetic polyandry, and the overall observed rates were high (74% COLON...

This study examined the usefulness of portable ultrasonography in accurately predicting pregnancy and fecundity in the bonnethead shark Sphyrna tiburo by comparing ultrasound‐obtained data with those obtained from animal dissection, the gold standard for elasmobranch reproduction studies. Mature female S. tiburo (n = 66) were collected throughout t...

Patterns of population structure, genetic demographics, and gene flow in the small coastal shark Carcharhinus isodon (finetooth shark) sampled from two discrete nurseries along the southeastern U.S. coast (Atlantic) and three nurseries in the northern Gulf of Mexico (Gulf), were assessed using 16 nuclear-encoded microsatellites and 1077 base pairs...

Elasmobranchs are considered to be top marine predators, and in general play important roles in the transfer of energy within marine ecosystems. Despite this, little is known regarding the physiological processes of digestion and nutrient absorption in these fishes. One topic that is particularly understudied is the process of nutrient uptake acros...

Population structure and lineage diversification within a small, non-dispersive hammerhead shark species, the bonnethead shark Sphyrna tiburo, was assessed. Sphyrna tiburo is currently described as one continuously distributed species along the Atlantic continental margins of North, Central and South America, but recent genetic analysis of an insul...

The reproduction of the sandbar shark Carcharhinus plumbeus in the U.S. south-eastern Atlantic Ocean including the Gulf of Mexico was examined using a combination of histological and morphological characteristics of C. plumbeus collected through fishery-dependent and -independent sampling programmes (n = 1,567). Indices of maturity were constructed...

Sex-biased dispersal is expected to homogenize nuclear genetic variation relative to variation in genetic material inherited through the philopatric sex. When site fidelity occurs across a heterogeneous environment, local selective regimes may alter this pattern. We assessed spatial patterns of variation in nuclear-encoded, single nucleotide polymo...

Sex-biased dispersal is expected to homogenize nuclear genetic variation relative to variation in genetic material inherited through the philopatric sex. When site fidelity occurs across a heterogeneous environment, local selective regimes may alter this pattern. We assessed spatial patterns of variation in nuclear-encoded, single nucleotide polymo...

Sex-biased dispersal is expected to homogenize nuclear genetic variation relative to variation in genetic material inherited through the philopatric sex. When site fidelity occurs across a heterogeneous environment, local selective regimes may alter this pattern. We assessed spatial patterns of variation in nuclear-encoded, single nucleotide polymo...

As demonstrated in past studies, androgens appear to play critical roles in regulating reproduction in male sharks. However, little is known about the cell-specific actions of androgens in these fishes. To address this, this study examined androgen targets in reproductive organs of a seasonally reproducing shark, the bonnethead (Sphyrna tiburo). A...

Sex-biased dispersal is expected to homogenize nuclear genetic variation relative to variation in genetic material inherited through the philopatric sex. When site fidelity occurs across a heterogeneous environment, local selective regimes may alter this pattern. We assessed spatial patterns of variation in nuclear-encoded, single nucleotide polymo...

Identifying the driving forces behind oceanic pelagic shark movements is key to a better understanding of their life history. Some oceanic pelagic shark species have been shown to aggregate in specific regions to mate and/or exploit abundant food resources. The oceanic whitetip shark Carcharhinus longimanus, a subtropical, ectothermic, oceanic pela...

Patterns of population structure and historical genetic demography of blacknose sharks in the western North Atlantic Ocean were assessed using variation in nuclear-encoded microsatellites and sequences of mitochondrial (mt)DNA. Significant heterogeneity and/or inferred barriers to gene flow, based on microsatellites and/or mtDNA, revealed the occur...

Previous studies have demonstrated that sharks, perhaps more so than any other fishes, are capable of bioaccumulating the non-essential toxic metal mercury (Hg) to levels that threaten the health of human seafood consumers. However, few studies have explored the potential effects of Hg accumulation in sharks themselves. Therefore, the goal of this...

Sharks are considered top predators in many marine ecosystems and can play an important role in structuring community ecology. As a result, it is necessary to understand the factors that influence their abundance and distribution. This is particularly important as fishery managers develop management plans for sharks that identify areas that serve a...

The presence of human pharmaceuticals in sewage-impacted ecosystems is a growing concern that poses health risks to aquatic wildlife. Despite this, few studies have investigated the uptake of active pharmaceutical ingredients (APIs) in aquatic organisms. In this study, the uptake of 9 APIs from human drugs was examined and compared in neonate bull...

Fish kills often occur overnight from low dissolved oxygen (DO) events, however many mortality events are of unknown cause, since little water quality monitoring occurs overnight. The hypoxia-inducible factor 1α (HIF-1α) protein is an excellent candidate as a biomarker for deciphering idiopathic fish kills. In this study, spot (Leiostomus xanthurus...

Publisher Summary Chondrichthyan fishes have a long evolutionary history that goes back more than 400 million years. Part of their evolutionary success is attributed to their diverse reproductive modes and adaptations related to reproductive physiology. Chondrichthyan fishes can be separated into two main groups, based on reproductive mode: oviparo...

Among the most conserved osmoregulatory hormone systems in vertebrates are the renin-angiotensin system (RAS) and the natriuretic peptides (NPs). We examined the RAS and NP system in the euryhaline Atlantic stingray, Dasyatis sabina (Lesueur). To determine the relative sensitivity of target organs to these hormonal systems, we isolated cDNA sequenc...

To examine variation in diet and daily ration of the bonnethead shark, Sphyrna tiburo (Linnaeus 1758), animals were collected from three areas in the eastern Gulf of Mexico: northwest Florida (∼29°40′N, 85°13′W), Tampa Bay near Anclote Key (∼28°10′N, 82°42.5′W), and Florida Bay (∼24°50′N, 80°48′W) from March through September, 1998–2000. In each ar...

Within the past decade, reproductive and health disorders have been reported to occur in unique populations of Atlantic stingrays (Dasyatis sabina) inhabiting certain components of Florida's St. Johns River. Since these irregularities are consistent with the alleged effects of organochlorine (OC) contaminant exposure in other Florida wildlife, the...

Environmental pollutants capable of disrupting endocrine function and impairing hormonally regulated processes such as animal reproduction pose significant threats to the health of aquatic wildlife populations. Unfortunately, broad assessments of endocrine-disrupting activity are difficult to perform for large aquatic ecosystems because of the subs...

The clasper gland of the Atlantic stingray, Dasyatis sabina, was examined over a 1-year period, covering an entire reproductive cycle. Changes in clasper gland tissue architecture, fluid production, and cell proliferation were assessed. No changes in tissue architecture were observed. Evidence of cell proliferation in the gland epithelium was not d...

Maternally provisioned yolk hormones have been determined to play critical roles in development across vertebrate taxa. This study ascertained the presence and concentration of thyroid hormones triiodothyronine (T(3)) and thyroxine (T(4)) in the maternal serum and yolk of the developing placental viviparous shark Sphyrna tiburo from one site adjace...

Because of their persistence in aquatic environments and ability to impair reproduction and other critical physiological processes, organochlorine (OC) contaminants pose significant health risks to marine organisms. Despite such concerns, few studies have investigated levels of OC exposure in sharks, which are fish particularly threatened by anthro...

Copper and lead substitution reactions were found to be useful in demonstrating growth patterns in vertebrae from several elasmobranch species. In contrast, iron substitution was ineffective in detecting variations in vertebral mineralization. The present study provides two alternative methods for elasmobranch age determination that may prove usefu...

There is growing interest in the mating systems of sharks and their relatives (Class Chondrichthyes) because these ancient fishes occupy a key position in vertebrate phylogeny and are increasingly in need of conservation due to widespread overexploitation. Based on precious few genetic and field observational studies, current speculation is that po...

Among vertebrates, maternal transfer of hormones to offspring has been studied extensively in mammals (placental transfer) and more recently in oviparous birds and reptiles (yolk transfer). The placental viviparous bonnethead shark, Sphyrna tiburo, allows the investigation of both yolk and placental hormone transfers in a single organism. In this s...

The field of “elasmobranch endocrinology” began at the same time as the field of vertebrate endocrinology itself, when Bayliss and Starling (1903) used extracts from the intestines of sharks and skates to demonstrate the actions of secretin, the first described vertebrate hormone. Although perhaps coincidental, a pivotal role for sharks and their r...

Calcitonin is a 32-amino acid peptide hormone that is best known for its actions in maintaining skeletal integrity and calcium homeostasis in mammals. Calcitonin also appears to function in regulating certain aspects of animal reproduction, but the nature of this role remains unclear, particularly in nonmammalian vertebrates. The present study inve...

Relaxin is a 6-kd polypeptide hormone that is responsible for regulating several reproductive processes in female vertebrates, but its role in male reproduction remains unclear. To aid in clarifying this role, the objective of the present study was to investigate changes in endogenous relaxin levels associated with reproductive events in male elasm...

Changes inthe morphology and histologyofthe epididymis and seminal vesicle in male Atlantic stingrays (Dasyatis sabina) were examined in relation tothe seasonal reproductive cycle. Observations onthe size and structureofthese organs were accompanied by analysisof cell proliferation in genital duct epithelia using proliferating cell nuclear antigen...

The northwest Atlantic population of smooth dogfish (Mustelus canis) ranges from Cape Cod, Massachusetts, to South Carolina. Although M. canis is seasonally abundant in this region, very little is known about important aspects of its biology, such as growth and reproductive rates. In the early 1990s, commercial fishery landings of smooth dogfish dr...

Puberty is a critical, hormone-mediated event during which an animal acquires the ability to breed and propagate. Despite the importance of this stage in animal reproduction, little is known regarding the physiological factors that regulate and/or accompany puberty in several vertebrate groups including elasmobranchs. To address the need for such i...

Effects of insulin-like growth factor-I (IGF-I), corticosterone, and triiodothyronine (T(3)) on in vitro growth of vertebral cartilage of the clearnose skate, Raja eglanteria, were investigated. Uptake of [(35)S]sulfate in cultured vertebrae was used to characterize glycosaminoglycan (GAG) synthesis and cartilage growth. IGF-I significantly enhance...

Diet and feeding habits of the smooth dogfish, Mustelus canis, Atlantic sharpnose, Rhizoprionodon terraenovae, dusky, Carcharhinus obscurus, and the sand tiger, Carcharias taurus sharks, were investigated through analysis of stomach contents. Diet in M. canis was relatively homogeneous and was dominated by crustaceans, consisting mostly of rock cra...

The effectiveness of calcein as a fluorescent marker of elasmobranch vertebrae was examined in the nurse shark Ginglvmostotna cirratum. Intramuscular injection of calcein at a standard dosage of 25 mg/kg body weight (BW) produced distinct fluorescent marks in nurse shark vertebrae; however, it also induced physiological stress and mortality. Lower...

Studies were undertaken to examine the importance of organic proteoglycan matrices in the calcification of elasmobranch vertebral cartilage. Proteoglycans were extracted from the vertebral cartilage of the clearnose skate, Raja eglanteria Bosc, with a 3M guanidine hydrochloride/10% EDTA solution. Proteoglycan solutions (12 μg ml(-1)) were effective...

Recent studies have demonstrated that biologically active levels of ecoestrogens, environmental chemicals capable of altering estrogen-regulated processes in aquatic organisms, may be present in surface waters of southwest Florida's Caloosahatchee River Estuary and pose health risks to local wildlife. This study examined the concentrations of estro...

Thesis (B.S.)--Eckerd College, 1990.