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Genomic studies of vertebrate chromosome evolution have long been hindered by the scarcity of chromosome-scale DNA sequences of some key taxa. One of those limiting taxa has been the elasmobranchs (sharks and rays), which harbor species often with numerous chromosomes and enlarged genomes. Here, we report the chromosome-scale genome assembly for the zebra sharkStegostoma tigrinum, an endangered species that has the smallest genome sequenced to date among sharks (3.71 Gb), as well as for the whale sharkRhincodon typus. Our analysis employing a male–female comparison identified an X chromosome, the first genomically characterized shark sex chromosome. The X chromosome harbors a Hox C cluster whose intact linkage has not been shown for an elasmobranch fish. The sequenced shark genomes exhibit a gradualism of chromosome length with remarkable length-dependent characteristics—shorter chromosomes tend to have higher GC content, gene density, synonymous substitution rate, and simple tandem repeat content as well as smaller gene length, which resemble the edges of longer chromosomes. This pattern of intragenomic heterogeneity, previously recognized as peculiar to species with so-called microchromosomes, occurs in more vertebrates including elasmobranchs. We challenge the traditional binary classification of karyotypes as with and without microchromosomes, as even without microchromosomes, shorter chromosomes tend to have higher contents of GC and simple tandem repeats and harbor shorter and more rapid-evolving genes. Such characteristics also appear on the edges of longer chromosomes. Our investigation of elasmobranch karyotypes underpins their unique characteristics and provides clues for understanding how vertebrate karyotypes accommodate intragenomic heterogeneity to realize a complex readout.

The many diverse reproductive strategies of elasmobranchs (sharks, skates and rays) from lecithotrophic oviparity to matrotrophic viviparity have attracted significant research attention. However, the endocrine control of elasmobranch reproduction is less well-documented largely due to their reproductive characteristics, such as a long reproductive cycle, and/or repeated internal fertilization using stored sperm in oviparous species. In the present study, for the first time, we succeeded in non-invasive monitoring of the continuing egg-laying cycle of the cloudy catshark Scyliorhinus torazame using portable ultrasound devices. Furthermore, long-term simultaneous monitoring of the egg-laying cycle and measurement of plasma sex steroids revealed cycling patterns of estradiol-17β (E2), testosterone (T) and progesterone (P4). In particular, a decline in T followed by a reciprocal surge in plasma P4 were consistently observed prior to the appearance of the capsulated eggs, implying that P4 is likely associated with the ovulation and/or egg-case formation. While the cycling pattern of E2 was not as apparent as those of T and P4, threshold levels of E2 (5 ng/mL) and T (1 ng/mL) appeared to be crucial in the continuation of egg-laying cycle. The possibility to trace the dynamics of plasma sex steroids in a single individual throughout the reproductive cycles makes the catshark a useful model for regulatory and mechanistic studies of elasmobranch reproduction.

Display of whale sharks in public aquariums demands the largest aquarium habitats yet designed and presents a number of significant challenges. Nonetheless, these facilities offer extraordinary opportunities to advance our understanding of whale sharks in ways that are different from, and complementary to, field research. In this chapter, scientists, veterinarians and husbandry experts from two facilities that house whale sharks present data and lessons from their care in public aquariums, including acquisition, habitat design, feeding, behavior management, veterinary care, growth, and reproduction. Approaches to drawing blood are discussed and normal blood values for hematology, clinical chemistry, and fatty acid composition are presented. Future successful breeding efforts with whale sharks in public aquariums may prove the best and possibly even the only chance to answer some of the most pressing questions about reproduction in the world’s biggest fish. Beyond the scientific opportunities, public aquariums will continue to provide a way to raise the public profile of whale sharks because far more people visit these facilities than can (or should) participate in wildlife tourism with this species.

International audience; Advances in biologging technology have enabled 3D dead-reckoning reconstruction of marine animal movements at spatiotemporal scales of meters and seconds. Examining high-resolution 3D movements of sharks (Galeocerdo cuvier, N = 4; Rhincodon typus, N = 1), sea turtles (Chelonia mydas, N = 3), penguins (Aptenodytes patagonicus, N = 6), and marine mammals (Arctocephalus gazella, N = 4; Ziphius cavirostris, N = 1), we report the discovery of circling events where animals consecutively circled more than twice at relatively constant angular speeds. Similar circling behaviors were observed across a wide variety of marine megafauna, suggesting these behaviors might serve several similar purposes across taxa including foraging, social interactions, and navigation

There was an error in [Journal of Experimental Biology (2019) 223, jeb210286][1] ([doi: 10.1242/jeb.210286][2]). The authors inadvertently transposed the explanations of the colours in Fig. 4. HTC models in red are with the rate of temperature change due to internal heat production and those in

It is generally assumed that the body temperature of large animals is less likely to change due to their large body size, resulting in a high thermal inertia and a smaller surface area to volume ratio. The goal of this study was to investigate the stability of body temperature in large fish using data from field experiments. We measured the muscle temperatures of free-ranging whale sharks (Rhincodon typus), the largest extant fish globally, and investigated their ectothermic physiology and the stability of their body temperatures. The measured muscle temperature of the whale sharks changed substantially more slowly than the water temperature fluctuations associated with vertical movements, and the whole-body heat-transfer coefficients (HTC) of whale sharks estimated using heat-budget models were lower than those of any other fish species measured to date. The heat-budget models also showed that internal heat production does not contribute to changes in muscle temperature. A comparative analysis showed that the HTC at cooling in various fish species including both ectothermic and endothermic species ranging from 10−4 to 103 kg was proportional to body mass−0.63. This allometry was present regardless of whether the fish were ectothermic or endothermic, and was an extension of the relationship observed in previous studies on small fish. Thus, large fish have the advantage of body temperature stability while moving in environments with large temperature variations. Our results suggest that the large body size of whale sharks aids in preventing a decrease in body temperature during deep excursions to more than 1000 m depths without high metabolic costs of producing heat.

The present study provides a noninvasive method to estimate the body volume of sharks (Elasmobranchii, Selachii) using a computational geometric model. This method allows the volume of sharks to be estimated from lateral and ventral photographs assuming an elliptical body cross-sectional geometry. A comparison of the estimated and actual body volumes of several shark species showed that the estimation error was Applying this model to captive whale sharks (Rhincodon typus) that were 8.0 and 8.8 m in total length revealed that their body volumes were 3.5 and 4.5 m3, respectively. These estimates allowed for the quantitative evaluation of our hypothesis, that the whale shark uses suctioned air for buoyancy control during vertical feeding—a behavior unique to this species among elasmobranchs. The volume estimates of the captive whale sharks, together with the density estimates from their liver proportions, revealed that the air occupying a part of oro-pharyngeal and branchial cavities can help the whale sharks to keep their body floating. This hypothesis may explain how the whale shark sometimes stays at the water surface without fin motion during vertical feeding, even though their body density is greater than that of seawater.

It is generally assumed that the body temperature of large animals is less likely to change because of their large body size, resulting in a high thermal inertia and a smaller surface area to volume ratio. The goal of this study was to investigate the stability of body temperature in large fish using data from field experiments. We measured the muscle temperatures of free-ranging whale sharks (

Most cartilaginous fishes live principally in seawater (SW) environments, but a limited number of species including the bull shark

Most of the cartilaginous fishes live principally in seawater (SW) environments, while a limited number of species including the bull shark, Carcharhinus leucas, inhabit both SW and freshwater (FW) environments during their life cycle. Euryhaline elasmobranchs maintain high internal urea and ion levels even in FW environments, but little is known about the osmoregulatory mechanisms that enable them to maintain internal homeostasis in hypoosmotic environments. In the present study, we focused on the kidney because this is the only organ that can excrete excess water from the body in a hypoosmotic environment. We conducted a transfer experiment of bull sharks from SW to FW and performed differential gene expression analysis between the two conditions using RNA-seq. A search for genes up-regulated in the FW-acclimated bull shark kidney indicated that the expression of the Na+-Cl− cotransporter (NCC; Slc12a3) was ten times higher in the FW-acclimated fish compared to that in SW fish. In the kidney, apically-located NCC was observed in the late distal tubule and in the anterior half of collecting tubule where basolateral Na+/K+-ATPase was also expressed, implying that these segments contribute to NaCl reabsorption from the filtrate for diluting the urine. This expression pattern was not observed in the houndshark, Triakis scyllium, that had been transferred to 30% SW; this species cannot survive in FW environment. The salinity transfer experiment combined with a comprehensive gene screening approach demonstrates that NCC is a key renal protein that contributes to the remarkable euryhaline ability of the bull shark.

Modern cartilaginous fishes are divided into elasmobranchs (sharks, rays and skates) and chimaeras, and the lack of established whole-genome sequences for the former has prevented our understanding of early vertebrate evolution and the unique phenotypes of elasmobranchs. Here we present de novo whole-genome assemblies of brownbanded bamboo shark and cloudy catshark and an improved assembly of the whale shark genome. These relatively large genomes (3.8–6.7 Gbp) contain sparse distributions of coding genes and regulatory elements and exhibit reduced molecular evolutionary rates. Our thorough genome annotation revealed Hox C genes previously hypothesized to have been lost, as well as distinct gene repertories of opsins and olfactory receptors that would be associated with adaptation to unique underwater niches. We also show the early establishment of the genetic machinery governing mammalian homoeostasis and reproduction at the jawed vertebrate ancestor. This study, supported by genomic, transcriptomic and epigenomic resources, provides a foundation for the comprehensive, molecular exploration of phenotypes unique to sharks and insights into the evolutionary origins of vertebrates. Genomic resources for cartilaginous fishes are scarce. Here, the authors sequence the genome of three sharks and provide insights on the molecular basis of adaptation to underwater lifestyle and the evolutionary origins of vertebrates.

Captive breeding in aquaria is a useful means for ex situ preservation of threatened elasmobranch species. To promote captive breeding, it is important to determine the female reproductive status. However, information regarding reproductive status in female elasmobranchs is limited. Here, we used zebra sharks, Stegostoma fasciatum, as a model for elasmobranch reproduction in captivity. We investigated the relationships among changes in the sex steroid hormone levels, follicle size, and egg-laying period to develop indicators for the female reproductive status. We confirmed that mature female zebra sharks undergo an annual reproductive cycle. Additionally, we showed that the variations in sex steroid hormone levels correlated with reproductive status in mature female zebra sharks. Plasma estradiol-17s (E2) concentrations increased two months before ovarian follicle development and decreased along with follicle regression. Interestingly, E2 levels were inversely correlated with water temperature (R = −0.901). Moreover, high levels of testosterone (T) correlated well with the laying period. These results strongly suggest that E2 is an indicator for ovarian follicle development, and that T is a useful indicator for both the onset and end of the egg-laying period in captive zebra sharks.

Background In this study, we report the first case of a male reef manta ray, Mobula alfredi, becoming sexually mature in captivity and present its reproductive characteristics. Methods We investigated changes in external morphology, behavior, and levels of steroid hormones in a male M. alfredi during its sexual maturation process. Results At 2 years and 6 months of age, the male exceeded 300 cm in disc width. Then, at around 3 years of age, the male started to chase a female in the tank and exhibited androgen levels similar to that of another matured male, indicating that the study specimen had begun sexual maturation endocrinologically. Its first copulation event was observed at 5 years and 4 months and appeared behaviorally similar to field observations. Seven months after copulation, we performed a biopsy to collect its semen, including any motile sperm. Conclusion Taken together, these results indicate that the captive male M. alfredi individual shows signs of sexual maturation (size of disc width, testosterone levels, reproductive behavior) already with the age of 2.5 to 3 years. As a first copulation was observed with 5 years 4 months of age and the presence of sperm were confirmed at the age of 5 years 11 months of age, the studied animal reached its full sexual maturity at the latest at the age of around 5 years.

Intra‐species variability in foraging strategies may be common, which has significant implications for efforts to understand and manage enigmatic species like the whale shark Rhincodon typus. The ecological relevance of differences in tissue isotopes within and between individuals in the context of foraging however depends on understanding tissue turnover times and carbon (Δ¹³C) and nitrogen (Δ¹⁵N) discrimination, which can vary with physiology, metabolism, and diet quality. Here, we examine isotope dynamics in captive R. typus as a basis for enhanced ecological insights into wild populations of the world's largest fish and other enigmatic species. A variable diet, principally consisting of two krill (Euphausia pacifica and Euphausia superba) provided an average of 48 ± 20 MJ/d (mean ± SD), or 2.7 ± 1.3 times basal metabolic requirements. On this diet, in agreement with allometric relationships, large body sizes (3,000–4,000 kg) were matched by slow plasma and cartilage turnover rates (empirically derived as 9 months and 3 yr, respectively), which provide tissue‐specific limits on the timescales over which we can isotopically detect diet changes in this species. Average diet‐to‐tissue discrimination showed significant variation between tissues (plasma and cartilage), and among growing and fasting individuals (Δ¹³C range, 1.5 to 5.5‰; Δ¹⁵N range, −0.1 to 2.9‰). Assimilation rates increased with temperature and were higher for the smaller E. pacifica (15 ± 2 mm) than E. superba (48 ± 2 mm). Growth significantly lowered both Δ¹⁵Nₚₗₐₛₘₐ and Δ¹⁵Ncₐᵣₜᵢₗₐgₑ, with inappetence markedly reducing Δ¹⁵Nₚₗₐₛₘₐ and Δ¹³Cₚₗₐₛₘₐ, as well as significantly altering blood biochemistry. Captive findings facilitated the first robust multi‐tissue growth‐ and nutrition‐corrected isotope analysis of a wild R. typus population, suggesting individual foraging specialization on low trophic level mid‐ocean or coastal prey. Long‐term fasting during ocean‐basin‐scale migrations may be common and such metabolic effects should be carefully quantified when isotopically assessing intra‐species foraging differences. The metabolically constrained multi‐tissue, multi‐isotope approach described can facilitate ecological insights that are indispensable for effective conservation and management of globally threatened, but poorly understood, species by identifying differences in key foraging areas and target prey within and between individuals.

Background Okinawa Churaumi Aquarium has established a long-term husbandry program for whale sharks since 1980. Currently, three individuals (1 male and 2 female) are housed in the 7,500 m3 capacity main exhibit tank. The male shark was caught by a set-net on March 11, 1995, and it measured a total length (TL) of 460 cm; a subsequent measurement in December 2015 revealed the TL had increased to 865 cm. The corresponding TLs of the female sharks that have been housed in this facility for nine and eight years were 762 cm and 787 cm, respectively. The growth rate, hormonal trends, quantity of food ingested, behaviors, and other physical changes along with maturation of these sharks are presently monitored. Approach The total length of each whale shark was estimated by measuring the length between the snout tip and the first dorsal fin using an equation formulated by us. Periodic measurements of the girth at the posterior margin of the pectoral fin have been recorded since May 2014. For measuring hormonal levels, blood was collected underwater from free-swimming individuals and plasma samples were extracted. The plasma concentration of steroid hormone was measured using time-resolved fluorescent antibody analysis. This data has been collected since May 2008. The quantity of food consumed and the feeding behavior of the whale sharks are recorded each day. Results The TL of the male whale shark increased from 460 cm to 744 cm by March 2005, at an average annual growth rate of 28 cm/year. Since 2005, there has been a decrease in the growth rate, to 12.5 cm/year. The two females have been growing at an annual rate of 33 cm/year (TL = 762 cm) and 37 cm/year (TL = 787 cm). Our data shows that the rate of change of girth appears to be associated with calorie intake. The plasma concentration of steroid hormone of the male shark increased from June 2011 to June 2012 (21.49 ng/ml; TL: 850 cm). This appears to be in synchrony with the rapid elongation of the claspers. Additionally, since April 2012, we have been observing the male shark rotating its entire body laterally crossing both claspers, which is a behavioral indication that the male has reached maturity. Conclusions From our long-term study on captive whale sharks, details on direct observations on the maturity process, growth rate, required food consumption, behavioral patterns, and proportional measurement changes are available. Based on these details, we expect that future attempts for reproduction in captivity would be successful and would allow us to unravel many mysteries of whale shark reproduction.

Background Okinawa Churaumi Aquarium (formerly Okinawa Expo Aquarium) has been conducting research on the whale shark, both in captivity and in the wild since 1975. Proportional measurements, including total length, girth, and weight, are essential to examine the growth, maturity, and physical condition of the animal, as well as to estimate the required quantity of food and drug dose for medical treatment. However, measurement of the precise length of large aquatic animals is very difficult and often results in errors. We formulated an allometric equation used to estimate the total length (TL) and body weight (BW) by measuring appropriate smaller body parts. Approach We used morphometric data from 33 individuals stranded or accidentally caught by commercial fishery off Okinawa Island between 1979 and 2010. We examined 66 measured characters of each whale shark. Furthermore, we applied the conventional allometric function, and modified the function to be logarithmic to use a liner approximation. The reduced major axis (RMA) test was applied to all logarithmic morphometric data, and we chose to measure characters that were highly correlated with TL. Some of the characters showing high correlation with TL according to the RMA test were further analyzed for sex-based differences using the t-test. The most suitable morphometric characters that were measurable in free-swimming sharks were chosen from the set of characters that passed those tests. In addition, we analyzed weight data from 8 specimens (7 male and 1 female) that were considered to be in an almost normal condition. We applied the conventional allometric function to an estimation equation. Girth measurement at the posterior margin of the pectoral fins was directly performed on the free-swimming individuals. Results A high coefficient of determination (R2) was obtained for 8 morphometric characters: pre-first dorsal length (PD1), pre-second dorsal length (PD2), pre-caudal length (PRC), pre-pelvic length (PP2), pre-anal length (PAL), length of dorsal caudal margin (CDM), mouth width (MOW), and interorbital space (INO). We considered that the equation formulated using PD1 was the most suitable based on sex-based differences and the animal's swimming properties. The following equation estimates the TL in centimeters:log TL = 0.964 log PD1 + 0.443 (R2 = 0.930, n = 33)For BW estimation, the sex-based differences could not be tested because of the small sample size. The following equation estimates BW in kilograms:BW = 4.510 TL3.280 (R2 = 0.958, n = 8)The data of girth measurements was collected from captive (n = 3) and wild (n = 6) sharks. Conclusions Data on proportional measurements is useful as an index of growth condition. Our focus is to monitor the size of our females and track the physiological indicators of maturation to achieve the first captive reproduction of whale sharks.

More than 50 specimens of the megamouth shark Megachasma pelagios have been reported so far, but biological obser- vations on the species are still limited. We examined a female megamouth specimen that was captured by the bonito purse seine fishery in the Kuroshio Extension in July 2007 and donated to the Okinawa Churaumi Aquarium. The specimen was an immature female, 3,667 mm in total length and 361 kg in weight. The stomach contents measured 2,200 mL excluding the portion that was lost from the specimen before measurement. Detailed examination of a small part (14.6 mL) of the stomach contents revealed un- damaged worm-like organisms, 10 partially damaged euphausiids and abundant fragmented pieces of euphausiids. The worm-like organisms were probably parasites such as tapeworms. The partially damaged euphausiids were identified as Euphausia pacifica except for one individual of Nematoscelis difficilis. Based on the number of fragmented right mandibles, which were less damaged than the other fragmented appendages, the total number of euphausiids in the stomach contents is estimated to be at least 18,000 in- dividuals. The high abundance of euphausiids in the stomach contents suggests that the present specimen has fed on a swarm of E. pacifica in an oceanic area.

The molecular structure of trans -cinnamaldehyde (( E )-3-phenyl-2-propenal) was determined by means of gas electron diffraction. The nozzle temperature was 165 °C. The results of B3LYP calculations with the 6-31G ∗∗ basis set were used as Supporting information . It was found that this molecule has two stable conformers, s- cis and s- trans , which differ in the orientation of the CH O group. Their abundances at 165 °C were determined to be 25 ± 19% and 75%, for the s- cis and s- trans , respectively. This conformational composition is consistent with the prediction by the theoretical calculations. The determined structural parameters ( r g and ∠ α ) of the more abundant conformer, s- trans , of trans -cinnamaldehyde are as follows: r (C C) ring > = 1.398(1) A; r (C C) = 1.348 (←) A; r (C 1 C) = 1.470(8) A; r (C C( O)) = 1.473(←) A; r (C O) = 1.225(6) A; r (C H)> = 1.116(6) A; ∠C 6 C 1 C 2 = 118.6(3)°; ∠C 1 C 2 C = 121.0(←)°; ∠C C 6 C 1 = 121.4(←)°; ∠C 2 C 1 C( C) = 122.0(26)°; ∠C 1 C C = 128.3(26)°; ∠C C CO = 115.3(27)°; ∠C C O = 126.6(19)°. The C 1 , C 2 and C 6 atoms are on the ring with the C 1 attached to the CH CH CHO group, and the C 2 and C 6 are on the cis and trans sides to the C C bond, respectively. Angle brackets denote average values; parenthesized values are the estimated limits of error (3 σ ) referring to the last significant digit; left arrows in the parentheses mean that the differences to the preceding parameters are fixed.

Captive breeding of whale sharks is one of the great challenges for aquariums. However, there is limited information available related to reproductive physiology due to the difficulty of sampling and long-term observation. In the present report, we provide information on the reproductive physiology of female whale sharks, which were incidentally captured as bycatch in a set-net off the coast of Okinawa, Japan. Total lengths of three captured female whale sharks were 403, 665, and 761 cm, respectively, at the time of their death. Collected paired ovaries differed in size between right and left. However, it seems not to determine which side of ovary becomes developed. Histological observations revealed that oocytes surrounded by follicle cell layers localized in the developed ovary, and most developed oocytes exhibited yolk vesicle stage. Additionally, in the largest specimen, there were low levels of three steroid hormones (Testosterone, Dihydrotestosterone, and Estradiol-17s) that did not show seasonal variation. The present results indicate that even the whale shark over 7 m in TL are still histologically and endocrinologically immature. We expect that the present data will provide fundamental information related to reproductive physiology of female whale sharks, and will contribute to protection activities and increased success in captive breeding of whale sharks.

Central nervous system (CNS) relapse is a critical issue while treating Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). A 58-year-old woman with Ph-positive ALL who relapsed after bone marrow transplantation for meningeal leukemia was treated with high-dose methotrexate, which resulted in remission. She underwent allogeneic cord blood transplantation followed by reduced intensity conditioning chemotherapy with imatinib; however, she experienced CNS relapse and developed an extramedullary mass on the right side of the temporal region. We treated 40 mg of dasatinib once daily, which had to be temporarily discontinued because she developed grade 2 pleural effusion and grade 2 hematemesis. After reinitiation of dasatinib, the extramedullary mass disappeared and meningeal leukemia ameliorated almost immediately. With 40 mg dasatinib administered once daily, its trough level and cerebrospinal fluid (CSF) concentration were 32 ng/mL and below the sensitivity threshold of 1 ng/mL, respectively. Treatment was continued, and the patient remained in complete remission until she died of pneumonia 7 years after the initial diagnosis of ALL. Dasatinib can be an effective treatment for Ph-positive ALL with CNS relapse. Although the concentration in the CSF seems low, it may be sufficient to exert anti-leukemic effects in the human CNS.

Multiple myeloma (MM) is a malignancy of the plasmocyte and is associated with various symptoms such as anemia, immunodeficiency, bone lesions and kidney insufficiency. Although prognosis was poor until some years ago, recent advances that introduced newer molecular targeting agents such as bortezomib and thalidomide have resulted in a better prognosis for MM. However, clinical manifestations and the relationship between cellular and molecular findings, including chromosomal translocation and the related overexpression of oncogenes such as CCND1 (cyclin D1) and FGFR3 (fibroblast growth factor receptor 3), remain unclear. It has been reported that a specific translocation may influence the prognosis of MM. Although translocations and overexpressed genes should be examined in ordinary clinical investigations, limited definitive assays for translocation involve the use of FISH (fluorescent in situ hybridization) or SKY (special karyotypic) methods. We therefore, attempted to establish a quick detection method for major translocated genes such as FGFR3, CCND1, CCND3 and MAF using multiplex RT-PCR (MP-RT-PCR). MP-RT-PCR can be performed within several to 24 h after bone marrow samples are taken. Two of 21 bone marrow blood samples from MM patients were analyzed using MP-RT-PCR and double-color FISH, and the results of both methods were compatible. Future utilization and elaboration of this method may help our understanding of the cell biology and clinical features of MM.