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Inokuchi M, Someya Y, Endo K, Kamioka K, Katano W, Takagi W, Honda Y, Ogawa N, Koshiba-Takeuchi K, Ohtani-Kaneko R, Hyodo S. Development of branchial ionocytes in embryonic and larval stages of cloudy catshark, Scyliorhinus torazame. Cell Tissue Res 2024; 397:81-95. [PMID: 38748215 PMCID: PMC11291541 DOI: 10.1007/s00441-024-03897-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 05/02/2024] [Indexed: 08/03/2024]
Abstract
In teleost fish, branchial ionocytes are important sites for osmoregulation and acid-base regulation by maintaining ionic balance in the body fluid. During the early developmental stages before the formation of the gills, teleost ionocytes are localized in the yolk-sac membrane and body skin. By comparing with teleost fish, much less is known about ionocytes in developing embryos of elasmobranch fish. The present study investigated the development of ionocytes in the embryo and larva of cloudy catshark, Scyliorhinus torazame. We first observed ionocyte distribution by immunohistochemical staining with anti-Na+/K+-ATPase (NKA) and anti-vacuolar-type H+-ATPase (V-ATPase) antibodies. The NKA- and V-ATPase-rich ionocytes appeared as single cells in the gill filaments from stage 31, the stage of pre-hatching, while the ionocytes on the body skin and yolk-sac membrane were also observed. From stage 32, in addition to single ionocytes on the gill filaments, some outstanding follicular structures of NKA-immunoreactive cells were developed to fill the inter-filament region of the gill septa. The follicular ionocytes possess NKA in the basolateral membrane and Na+/H+ exchanger 3 in the apical membrane, indicating that they are involved in acid-base regulation like single NKA-rich ionocytes. Three-dimensional analysis and whole-mount immunohistochemistry revealed that the distribution of follicular ionocytes was limited to the rostral side of gill septum. The rostral sides of gill septum might be exposed to faster water flow than caudal side because the gills of sharks gently curved backward. This dissymmetric distribution of follicular ionocytes is considered to facilitate efficient body-fluid homeostasis of catshark embryo.
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Affiliation(s)
- Mayu Inokuchi
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-8657, Japan.
- Department of Life Sciences, Toyo University, Itakura, Gunma, 374-0193, Japan.
| | - Yumiko Someya
- Department of Life Sciences, Toyo University, Itakura, Gunma, 374-0193, Japan
| | - Keitaro Endo
- Department of Life Sciences, Toyo University, Itakura, Gunma, 374-0193, Japan
| | - Katsunori Kamioka
- Department of Life Sciences, Toyo University, Itakura, Gunma, 374-0193, Japan
| | - Wataru Katano
- Department of Life Sciences, Toyo University, Itakura, Gunma, 374-0193, Japan
| | - Wataru Takagi
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan
| | - Yuki Honda
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan
| | - Nobuhiro Ogawa
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan
| | | | | | - Susumu Hyodo
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan
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Blackburn DG, Hughes DF. Phylogenetic analysis of viviparity, matrotrophy, and other reproductive patterns in chondrichthyan fishes. Biol Rev Camb Philos Soc 2024; 99:1314-1356. [PMID: 38562006 DOI: 10.1111/brv.13070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 02/25/2024] [Accepted: 02/28/2024] [Indexed: 04/04/2024]
Abstract
The reproductive diversity of extant cartilaginous fishes (class Chondrichthyes) is extraordinarily broad, reflecting more than 400 million years of evolutionary history. Among their many notable reproductive specialisations are viviparity (live-bearing reproduction) and matrotrophy (maternal provision of nutrients during gestation). However, attempts to understand the evolution of these traits have yielded highly discrepant conclusions. Here, we compile and analyse the current knowledge on the evolution of reproductive diversity in Chondrichthyes with particular foci on the frequency, phylogenetic distribution, and directionality of evolutionary changes in their modes of reproduction. To characterise the evolutionary transformations, we amassed the largest empirical data set of reproductive parameters to date covering nearly 800 extant species and analysed it via a comprehensive molecular-based phylogeny. Our phylogenetic reconstructions indicated that the ancestral pattern for Chondrichthyes is 'short single oviparity' (as found in extant holocephalans) in which females lay successive clutches (broods) of one or two eggs. Viviparity has originated at least 12 times, with 10 origins among sharks, one in batoids, and (based on published evidence) another potential origin in a fossil holocephalan. Substantial matrotrophy has evolved at least six times, including one origin of placentotrophy, three separate origins of oophagy (egg ingestion), and two origins of histotrophy (uptake of uterine secretions). In two clades, placentation was replaced by histotrophy. Unlike past reconstructions, our analysis reveals no evidence that viviparity has ever reverted to oviparity in this group. Both viviparity and matrotrophy have arisen by a variety of evolutionary sequences. In addition, the ancestral pattern of oviparity has given rise to three distinct egg-laying patterns that increased clutch (brood) size and/or involved deposition of eggs at advanced stages of development. Geologically, the ancestral oviparous pattern arose in the Paleozoic. Most origins of viviparity and matrotrophy date to the Mesozoic, while a few that are represented at low taxonomic levels are of Cenozoic origin. Coupled with other recent work, this review points the way towards an emerging consensus on reproductive evolution in chondrichthyans while offering a basis for future functional and evolutionary analyses. This review also contributes to conservation efforts by highlighting taxa whose reproductive specialisations reflect distinctive evolutionary trajectories and that deserve special protection and further investigation.
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Affiliation(s)
- Daniel G Blackburn
- Department of Biology & Electron Microscopy Center, Trinity College, 300 Summit St, Hartford, Connecticut, 06106, USA
| | - Daniel F Hughes
- Department of Biology, Coe College, 1220 First Avenue NE, Cedar Rapids, Iowa, 52402, USA
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Arimura S, Wong MKS, Inoue R, Kawano M, Shimoyama K, Fujimori C, Tokunaga K, Takagi W, Hyodo S. Functional characterization of follicle-stimulating hormone and luteinizing hormone receptors in cloudy catshark, Scyliorhinus torazame. Gen Comp Endocrinol 2024; 354:114542. [PMID: 38685391 DOI: 10.1016/j.ygcen.2024.114542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 04/08/2024] [Accepted: 04/26/2024] [Indexed: 05/02/2024]
Abstract
The follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) in cloudy catshark were cloned, and recombinant FSHR and LHR were expressed for characterization. Ventral lobe extract (VLE) from the pituitary contains homologous FSH and LH, and it stimulated the cAMP signaling of FSHR and LHR dose-dependently. Two transcript variants of LHR (LHR-L with exon 10 and LHR-S without) were identified, and LHR-S was the dominant form with higher basal cAMP activity without VLE stimulation. Among various developmental stages of follicles, FSHR expression was mainly associated with the pre-vitellogenic and early white follicles. When follicles were recruited into vitellogenesis, the expression of FSHR decreased while of LHR was upregulated reciprocally, suggesting that LHR may also be responsible for the control of vitellogenesis in chondrichthyans. The expression of LHR-L was upregulated among maturing follicles before ovulation, indicating LHR-L could have a specific role in receiving the LH surge signal for final maturation. Plasma LH-like activity was transiently increased prior to the progesterone (P4)-surge and testosterone-drop at the beginning of P4-phase, supporting a pituitary control of follicle-maturation via LH signaling in chondrichthyans. The expression of follicular LHR was downregulated during the P4-phase when LH-like activity was high, indicating that the LH-dependent downregulation of LHR is conserved in chondrichthyans as it is in other vertebrate lineages. (213 words).
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Affiliation(s)
- Shogo Arimura
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Marty Kwok Shing Wong
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan; Center for Earth Surface System Dynamics, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Ryotaro Inoue
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Mai Kawano
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Koya Shimoyama
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Chika Fujimori
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan; Department of Biological Sciences, Faculty of Science, Hokkaido University, Kita-10 Nishi-8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.
| | - Kotaro Tokunaga
- Ibaraki Prefectural Oarai Aquarium, Oarai, Ibaraki 311-1301, Japan.
| | - Wataru Takagi
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Susumu Hyodo
- Laboratory of Physiology, Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan; Center for Earth Surface System Dynamics, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
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Shimizu M, Takagi W, Sakai Y, Kayanuma I, Furukawa F. Gluconeogenesis in the yolk syncytial layer-like tissue of cloudy catshark (Scyliorhinus torazame). Physiol Rep 2024; 12:e16088. [PMID: 38811349 PMCID: PMC11136554 DOI: 10.14814/phy2.16088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Accepted: 05/12/2024] [Indexed: 05/31/2024] Open
Abstract
Glucose has important roles in the development of zebrafish, the vertebrate animal model; however, in most oviparous animals, the amount of maternally provided glucose in the yolk is scarce. For these reasons, developing animals need some ways to supplement glucose. Recently, it was found that developing zebrafish, a teleost fish, undergo gluconeogenesis in the yolk syncytial layer (YSL), an extraembryonic tissue that surrounds the yolk. However, teleost YSL is evolutionarily unique, and it is not clear how other vertebrates supplement glucose. In this study, we used cloudy catshark (or Torazame catshark), an elasmobranch species which possesses a YSL-like tissue during development, and sought for possible gluconeogenic activities in this tissue. In their yolk sac, glucose increased, and our isotope tracking analysis detected gluconeogenic activities with glycerol most preferred substrate. In addition, many of gluconeogenic genes were expressed at the YSL-like tissue, suggesting that cloudy catshark engages in gluconeogenesis in this tissue. The gluconeogenesis in teleost YSL and a similar tissue in elasmobranch species implies conserved mechanisms of yolk metabolism between these two lineages. Future studies on other vertebrate taxa will be helpful to understand the evolutionary changes in the modes of yolk metabolism that vertebrates have experienced.
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Affiliation(s)
- Marino Shimizu
- School of Marine BiosciencesKitasato UniversitySagamiharaKanagawaJapan
| | - Wataru Takagi
- Laboratory of PhysiologyAtmosphere and Ocean Research Institute, The University of TokyoKashiwa, ChibaJapan
| | - Yuki Sakai
- School of Marine BiosciencesKitasato UniversitySagamiharaKanagawaJapan
| | - Isana Kayanuma
- School of Marine BiosciencesKitasato UniversitySagamiharaKanagawaJapan
| | - Fumiya Furukawa
- School of Marine BiosciencesKitasato UniversitySagamiharaKanagawaJapan
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Fujimori C, Umatani C, Chimura M, Ijiri S, Bando H, Hyodo S, Kanda S. In vitro and in vivo gene transfer in the cloudy catshark Scyliorhinus torazame. Dev Growth Differ 2022; 64:558-565. [PMID: 36376176 PMCID: PMC10099843 DOI: 10.1111/dgd.12824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 09/20/2022] [Accepted: 09/29/2022] [Indexed: 11/16/2022]
Abstract
Cartilaginous fishes have various unique physiological features such as a cartilaginous skeleton and a urea-based osmoregulation strategy for adaptation to their marine environment. Also, because they are a sister group of bony vertebrates, understanding their unique features is important from an evolutionary perspective. However, genetic engineering based on gene functions as well as cellular behavior has not been effectively utilized in cartilaginous fishes. This is partly because their reproductive strategy involves internal fertilization, which results in difficulty in microinjection into fertilized eggs at the early developmental stage. Here, to identify efficient gene transfer methods in cartilaginous fishes, we examined the effects of various methods both in vitro and in vivo using the cloudy catshark, a candidate model cartilaginous fish species. In all methods, green fluorescent protein (GFP) expression was used to evaluate exogenous gene transfer. First, we examined gene transfer into primary cultured cells from cloudy catshark embryos by lipofection, polyethylenimine (PEI) transfection, adenovirus infection, baculovirus infection, and electroporation. Among the methods tested, lipofection, electroporation, and baculovirus infection enabled the successful transfer of exogenous genes into primary cultured cells. We then attempted in vivo transfection into cloudy catshark embryos by electroporation and baculovirus infection. Although baculovirus-injected groups did not show GFP fluorescence, electroporation successfully introduced GFP into muscle cells. Furthermore, we succeeded in GFP transfer into adult tissues by electroporation. The in vitro and in vivo gene transfer methods that worked in this study may open ways for genetic manipulation including knockout experiments and cellular lineage analysis in cartilaginous fishes.
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Affiliation(s)
- Chika Fujimori
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Chie Umatani
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Misaki Chimura
- Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Shigeho Ijiri
- Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Hisanori Bando
- Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Susumu Hyodo
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Shinji Kanda
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
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Inoue T, Shimoyama K, Saito M, Wong MKS, Ikeba K, Nozu R, Matsumoto R, Murakumo K, Sato K, Tokunaga K, Kofuji K, Takagi W, Hyodo S. Long-term monitoring of egg-laying cycle using ultrasonography reveals the reproductive dynamics of circulating sex steroids in an oviparous catshark, Scyliorhinus torazame. Gen Comp Endocrinol 2022; 327:114076. [PMID: 35710034 DOI: 10.1016/j.ygcen.2022.114076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 11/24/2022]
Abstract
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.
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Affiliation(s)
- Takuto Inoue
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Koya Shimoyama
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Momoko Saito
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Marty Kwok-Shing Wong
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Kiriko Ikeba
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Ryo Nozu
- Okinawa Churashima Research Center, Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206, Japan
| | - Rui Matsumoto
- Okinawa Churashima Research Center, Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206, Japan; Okinawa Churaumi Aquarium, 424 Ishikawa, Motobu, Okinawa 905-0206, Japan
| | - Kiyomi Murakumo
- Okinawa Churaumi Aquarium, 424 Ishikawa, Motobu, Okinawa 905-0206, Japan
| | - Keiichi Sato
- Okinawa Churashima Research Center, Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206, Japan; Okinawa Churaumi Aquarium, 424 Ishikawa, Motobu, Okinawa 905-0206, Japan
| | - Kotaro Tokunaga
- Ibaraki Prefectural Oarai Aquarium, Oarai, Ibaraki 311-1301, Japan
| | - Kazuya Kofuji
- Ibaraki Prefectural Oarai Aquarium, Oarai, Ibaraki 311-1301, Japan
| | - Wataru Takagi
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Susumu Hyodo
- Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
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Molecular mechanism of nutrient uptake in developing embryos of oviparous cloudy catshark (Scyliorhinus torazame). PLoS One 2022; 17:e0265428. [PMID: 35290397 PMCID: PMC8923501 DOI: 10.1371/journal.pone.0265428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/01/2022] [Indexed: 11/19/2022] Open
Abstract
Forms of embryonic nutrition are highly diverse in cartilaginous fishes, which contain oviparity, yolk-sac viviparity and several types of matrotrophic viviparity (histotrophy, oophagy, and placentotrophy). The molecular mechanisms of embryonic nutrition are poorly understood in these animals as few species are capable of reproducing in captivity. Oviparous cartilaginous fishes solely depend on yolk nutrients for their growth and development. In the present study, we compared the contribution to embryonic nutrition of the embryonic intestine with the yolk sac membrane (YSM). RNA-seq analysis was performed on the embryonic intestine and YSM of the oviparous cloudy catshark Scyliorhinus torazame to identify candidate genes involved in nutrient metabolism to further the understanding of nutrient utilization of developing embryos. RNA-seq discovery was subsequently confirmed by quantitative PCR analysis and we identified increases in several amino acid transporter genes (slc3a1, slc6a19, slc3a2, slc7a7) as well as genes involved in lipid absorption (apob and mtp) in the intestine after ‘pre-hatching’, which is a developmental event marked by an early opening of the egg case about 4 months before hatching. Although a reciprocal decrease in the nutritional role of YSM was expected after the intestine became functional, we observed similar increases in gene expression among amino acid transporters, lipid absorption molecules, and lysosomal cathepsins in the extraembryonic YSM in late developmental stages. Ultrastructure of the endodermal cells of YSM showed that yolk granules were incorporated by endocytosis, and the number of granules increased during development. Furthermore, the digestion of yolk granules in the YSM and nutrient transport through the basolateral membrane of the endodermal cells appeared to be enhanced after pre-hatching. These findings suggest that nutrient digestion and absorption is highly activated in both intestine and YSM after pre-hatching in catshark embryos, which supports the rapid growth at late developmental stages.
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Leigh SC, Summers AP, Hoffmann SL, German DP. Shark spiral intestines may operate as Tesla valves. Proc Biol Sci 2021; 288:20211359. [PMID: 34284626 DOI: 10.1098/rspb.2021.1359] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Looking to nature for inspiration has led to many diverse technological advances. The spiral valve intestine of sharks has provided the opportunity to observe the efficiency of different valve systems. It is supposed that the spiral intestine present in sharks, skates and rays slows the transit rate of digesta through the gut and provides increased surface area for the absorption of nutrients. In this investigation, we use a novel technique-creating three-dimensional reconstructions from CT scans of spiral intestines-to describe the morphology of the spiral intestine of at least one species from 22 different shark families. We discuss the morphological data in an evolutionary, dietary and functional context. The evolutionary analyses suggest that the columnar morphology is the ancestral form of the spiral intestine. Dietary analyses reveal no correlation between diet type and spiral intestine morphology. Flow rate was slowed significantly more when the two funnel-shaped spiral intestines were subjected to flow in the posterior to anterior direction, indicating their success at producing unidirectional flow, similar to a Tesla valve. These data are available to generate additional three-dimensional morphometrics, create computational models of the intestine, as well as to further explore the function of the gastrointestinal tract of sharks in structural and physiological contexts.
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Affiliation(s)
- Samantha C Leigh
- Department of Biology, California State University Dominguez Hills, Carson, CA 90747, USA
| | - Adam P Summers
- Biology and School of Aquatic and Fisheries Sciences, University of Washington, Friday Harbor, WA 98250, USA
| | | | - Donovan P German
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92617, USA
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