A comparison of the external morphology of the membranous inner ear in elasmobranchs

Studies on the elasmobranch inner ear have focused predominantly on a small group of sharks, particularly, carcharhinids. As a result, subsequent studies in other species have subdivided species into two main groups: those typical and those atypical of carcharhinid sharks. This study proposes a different set of inner‐ear morphology groupings to those previously suggested. The inner ears from 17 species of elasmobranchs (representing both sharks and rays) are examined in this study and based on morphometric data some groups include both rays and sharks. Four groups are now proposed based predominantly on the shape and dimensions of the membranous otoconial organs, and characteristics of the semicircular canals. Evident morphological differences between the ear types belonging to the new groups include the membranes of the semicircular canals being bound to the otoconial organs in some species, while only being connected via the canal ducts in others, as well as clear variation present in saccular organ size. Previous studies examining variation in the inner ear have attributed differences to either phylogeny or functional significance. Results from this study suggest that neither phylogeny nor feeding strategy solely accounts for the morphological diversity present in the external morphology of the elasmobranch inner ear. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

The comparative morphology of pit organs in elasmobranchs

The pit organs of elasmobranchs (sharks, skates and rays) are free neuromasts of the mechanosensory lateral line system. Pit organs, however, appear to have some structural differences from the free neuromasts of bony fishes and amphibians. In this study, the morphology of pit organs was investigated by scanning electron microscopy in six shark and three ray species. In each species, pit organs contained typical lateral line hair cells with apical stereovilli of different lengths arranged in an “organ‐pipe” configuration. Supporting cells also bore numerous apical microvilli taller than those observed in other vertebrate lateral line organs. Pit organs were either covered by overlapping denticles, located in open grooves bordered by denticles, or in grooves without associated denticles. The possible functional implications of these morphological features, including modification of water flow and sensory filtering properties, are discussed. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Ovarian morphology and folliculogenesis and ovulation process in the flat-faced fruit-eating bat Artibeus planirostris and the Argentine brown bat Eptesicus furinalis: A comparative analysis

The Neotropical bat species Artibeus planirostris and Eptesicus furinalis present a different morphology of the female reproductive organs: the first presents a simplex uterus, while the second presents a bicornuate uterus, but there is no information about their ovaries. Our aim was to compare the general ovary morphology and the folliculogenesis process in these species to increase the knowledge about the reproductive diversity of tropical bats. We observed a morphological distinction between the ovaries of both species: A. planirostris presents the primordial follicles located in a cranial portion of the ovary and the interstitial gland cells are not distinctive, while in E. furinalis, the primordial follicles are located throughout the cortex, and there is an abundance of interstitial gland cells. Both species present binovular or triovular follicles. Artibeus planirostris is a monovular species, with a preferential ovulation in the left side. Some females of E. furinalis exhibited two corpora lutea in the same ovary, and others presented a corpus luteum in both right and left ovaries at the same time; thus, E. furinalis is a polyovular species. Our results express the variation between two Neotropical species, reflecting the great variation in the reproductive aspects in Chiroptera.     

Morphological patterns of cell death in ovarian follicles of primary and secondary growth and postovulatory follicle complex of the annual killifish Millerichthys robustus (Cyprinodontiformes: Cynolebiidae)

The dynamics of cellular development and homeostasis of the ovary depend on the balance between proliferation and cell death throughout the reproductive cycle. Millerichthys robustus is an annual fish whose ovarian follicles develop asynchronously, allowing daily reproduction from sexual maturity until death. The objective of this research is to describe, histologically, the processes of follicular atresia and regression of postovulatory follicular complexes (POC) throughout a reproductive cycle of M. robustus. Patterns of cell death were documented by apoptosis in atretic follicles and POC, and necrosis in the POC after ovulation with an associated inflammatory response. Atretic follicles were seen from the onset of sexual maturity, during week three post-hatching (PH), both in primary growth (from the Cortical alveoli step, with folliculogenesis completed) and secondary growth Stages, with a higher prevalence in the latter. POCs were observed in different stages of regression from week four PH until the death of the fish. The apoptotic characteristics found were: (i) fragmentation of the nuclear membrane and zona pellucida, and liquefaction of the cortical alveoli and yolk; (ii) follicular cells becoming phagocytic, increasing their size, and migrating within the oocyte; and (iii) formation of an intrafollicular lumen, a product of phagocytosis of the oocyte constituents and dispersed pigments that remain after the digestion of yolk and cortical alveoli. The morphological changes of the follicular cells of the POC, from a squamous morphology after ovulation to columnar during its regression with PAS+ contents, was documented, suggesting a secretory activity.     

Unusual modes of oogenesis and brooding in bivalves: the case of Gaimardia trapesina (Mollusca: Gaimardiidae)

Abstract. I describe an unusual case of follicular oogenesis in a bivalve, Gaimardia trapesina , a common marine bivalve from the Magellan Region and adjacent Sub-Antarctic waters, whose members brood their developing larvae. The gonad in G. trapesina is an acinus organ that infiltrates the perivisceral connective tissue; the walls of the acini are formed by tall, slender cells with distal nuclei, supported by a thin conjunctive tissue layer. At the onset of vitellogenesis, each developing oocyte becomes surrounded by a one-cell-thick layer of follicle cells, which may originate from the wall of the acinus. The cells form a follicle that completely encompasses single oocytes, except at the basal zone, where oocytes are in contact with the acinus wall. The follicle persists beyond the end of vitellogenesis and spawning. After gamete release, the persistent follicle participates in the attachment of ova and developing embryos to the interfilamental junctions of the inner and outer demibranchs of the gill, where embryos are incubated until hatching as late-stage pediveliger larvae. Ripe eggs are large (∼250 μm diameter), suggesting that development is entirely lecithotrophic. The follicle cells that mediate connections between developing embryos and the maternal individual probably have a mechanical role only, providing support and possibly facilitating the accommodation of a large number of embryos to maximize the branchial space available for brooding.     

Quantification of the maternal-embryonal nutritional relationship of elasmobranchs: case study of wobbegong sharks (genus Orectolobus)

The present study used wobbegong sharks (genus Orectolobus) to assess the threshold value proposed by previous research to categorize strict lecithotrophic from incipient histotrophic species. Totals of 236 and 135 ornate wobbegong Orectolobus ornatus and spotted wobbegong Orectolobus maculatus, respectively, were collected from the New South Wales commercial fishery between June 2003 and May 2006. Eight pregnant gulf wobbegong Orectolobus halei were also recorded outside the sampling period for the first time. The three species were reproductively synchronous with a gestation of c. 10-11 months. Embryos started to be macroscopically visible during January and external yolk sacs were fully absorbed by June to July when embryos were c. 200 mm total length (L(T) ). Internal yolk sacs were first observed during April to May when embryos were c. 160 mm L(T) , reached a peak during June and persisted in embryos immediately prior to parturition. The total wet mass from uterine egg to full-term embryos increased by 44-89% and 45-62%, whereas the total organic mass decreased by 32-33% and 26%, for O. ornatus and O. maculatus, respectively, suggesting that these species are strict lecithotrophic yolk-sac viviparous sharks with no maternal nutrient input. A review of the literature identified various issues and suggested that the previously proposed organic mass loss threshold value separating strict lecithotrophic species from incipient histotrophic species might not be appropriate. Instead, it is recommended that a combination of methods (e.g. estimation of organic mass gain or loss between ovarian egg and developed embryo, histology and electron microscopy of the uterus, radio-tracer assay and uterine fluid analysis throughout gestation) is used to discern between strict lecithotrophic and incipient histotrophic species.     

The somatotopic organization of the olfactory bulb in elasmobranchs

The olfactory bulbs (OBs) are bilaterally paired structures in the vertebrate forebrain that receive and process odor information from the olfactory receptor neurons (ORNs) in the periphery. Virtually all vertebrate OBs are arranged chemotopically, with different regions of the OB processing different types of odorants. However, there is some evidence that elasmobranch fishes (sharks, rays, and skates) may possess a gross somatotopic organization instead. To test this hypothesis, we used histological staining and retrograde tracing techniques to examine the morphology and organization of ORN projections from the olfactory epithelium (OE) to the OB in three elasmobranch species with varying OB morphologies. In all three species, glomeruli in the OB received projections from ORNs located on only the three to five lamellae situated immediately anterior within the OE. These results support that the gross arrangement of the elasmobranch OB is somatotopic, an organization unique among fishes and most other vertebrates. In addition, certain elasmobranch species possess a unique OB morphology in which each OB is physically subdivided into two or more “hemi‐olfactory bulbs.” Somatotopy could provide a preadaptation which facilitated the evolution of olfactory hemibulbs in these species. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Morphological relationships and leukocyte influence on steroid production in the epigonal organ-ovary complex of the skate, Leucoraja erinacea

In elasmobranchs, a unique association exists between an immune tissue, the epigonal organ (EO), and the gonads. In this study, the histological and vascular relationships of the EO and ovarian follicles of the little skate, Leucoraja erinacea, were assessed. Perfusions of Evans blue dye and Batson's monomer showed a shared vascular pathway from the gonadal artery into the epigonal-ovary complex, with blood first entering the EO and then perfusing the ovarian follicles. Histological studies demonstrated direct cellular contact between epigonal leukocytes and the follicle wall (FW), as well as the presence of leukocytes between the steroidogenic theca and granulosa cells. In vitro analyses demonstrated that epigonal cells co-cultured with FW cells cause a dose-dependent inhibition of estrogen (E2) and testosterone (T) production. In contrast, conditioned media from epigonal leukocytes, stimulated or unstimulated with lipopolysaccharide (10 microg/ml), increase the production of E2 and T from FW cells of the ovaries. These studies provide a basis for further investigations of leukocyte secreted factors and cell contact modulation of follicular steroid production.     

The impact of the Pull of the Recent on extant elasmobranchs

Modern elasmobranchs have a long evolutionary history and an abundant fossil record that consists mainly of teeth. Many fossil taxa have living representatives. However, the representation of extant taxa in the fossil record is unknown. To begin to understand the geological history of extant elasmobranchs, we here assess the quality of their fossil record. We do so by assessing the Pull of the Recent (POR). The POR can bias the fossil record because the rather complete record of living taxa allows palaeontologists to identify fossil members of the modern clades and to bridge time bins where fossils are absent. We assessed the impact of the POR by quantifying the proportion of extant elasmobranchs that have a fossil record, but do not occur in the last 5 million years (Pliocene and Pleistocene). We found that the POR does not affect orders and families, but it does affect 24% of elasmobranch genera. Within the different elasmobranch orders, the Lamniformes display the most complete generic fossil record, with no impact of the POR. Although modest, the impact of the POR in extant elasmobranch genera is higher than that found in other taxa. Overall, the geological history of elasmobranchs contradicts the usual assumption that the fossil record becomes worse backwards in time. This is the case across geographical regions and tooth size, further suggesting that sampling intensity and outcrop availability might explain the POR effect on sharks and rays.     

Morphological and quantitative evaluation of the ovarian recrudescence in Nile tilapia (Oreochromis niloticus) after spawning in captivity

The Nile tilapia is one of the most important fish species for aquaculture worldwide. Understanding their reproductive biology is essential for improving their aquaculture methods. The morphological and quantitative dynamics of ovarian recrudescence of Oreochromis niloticus was studied for 21 days postspawning. To accomplish this, breeding females were kept in controlled conditions and ovarian samples were collected weekly for histological, ultrastructural and morphometric analyses. Ovarian follicle morphology revealed an intense synthesis activity of the follicular cells, which actively contributed to formation of the zona radiata and oocyte development following spawning. Recently spawned ovaries contained follicles at all developmental stages, but they were predominantly early primary growth (～42%) and full‐grown follicles (～20%). Remnants of spawning, postovulatory follicle complexes represented approximately 5% of the former ovarian follicles immediately after spawning, and less than 1% after 7 days. Atretic follicles accounted for approximately 2% of the follicles studied during the period. The stock of primary growth follicles was stable during ovarian recrudescence, indicating their availability for continuous recruitment. Only the frequency of full‐grown follicles significantly increased in the ovaries during recrudescence, representing approximately 35% of the follicles 21 days postspawning. The diameters of all follicles were significantly different between the periods analyzed. The ovaries' morphological characteristics, the maintenance of young follicles stocks and the gradual and significant increase in the proportion and diameter of full‐grown follicles showed a rapid ovarian recovery and follicular growth of O. niloticus, in 21 days at 29.5°C, necessary for the next spawning. J. Morphol. 275:348–356, 2014. © 2013 Wiley Periodicals, Inc.     

卵泡液细胞外囊泡携带的microRNA对卵泡闭锁影响的研究进展

细胞外囊泡(extracellular vesicles, EVs)是细胞主动释放的膜结合颗粒。在原核生物和真核生物中,EVs被认为是细胞间进行信息交流的一种方式。EVs具有携带蛋白质、脂质和核酸等生物大分子的能力,可以影响亲本细胞和受体细胞的不同生理功能。其中,EVs携带的microRNA研究报道最多,在生物体生理功能方面发挥着重要作用。卵泡在发育过程中,只有少数卵泡可以充分发育、成熟、排卵,大多数卵泡在发育的不同阶段发生闭锁。在卵泡发育的整个过程中,每一阶段的变化以及卵泡闭锁调控机制还不完全清楚。本文在总结EVs类型、特性、分离方法及用途的基础上,从不同细胞因子、激素方面重点论述了卵泡液中EVs携带的microRNA是如何调控卵泡闭锁,同时对卵泡液EVs携带的microRNA在生殖调控和生殖疾病诊断方面的研究前景进行了展望,对于卵泡发育调控研究以及有效利用研究具有一定参考意义。     

Phylogenetic trends in the abundance and distribution of pit organs of elasmobranchs

Pit organs (free neuromasts of the mechanosensory lateral line system) are distributed over the skin of elasmobranchs. To investigate phylogenetic trends in the distribution and abundance of pit organs, 12 relevant morphological characters were added to an existing matrix of morphological data (plus two additional end terminals), which was then re-analysed using cladistic parsimony methods ( paup * 4.0b10). Character transformations were traced onto the most parsimonious phylogenetic trees. The results suggest the following interpretations. First, the distinctive overlapping denticles covering the pit organs in many sharks are a derived feature; plesiomorphic elasmobranchs have pit organs in open slits, with widely spaced accessory denticles. Second, the number of pit organs on the ventral surface of rays has been reduced during evolution, and third, spiracular pit organs have changed position or have been lost on several occasions in elasmobranch evolution. The concentrated-changes test in macclade (version 4.05) was used to investigate the association between a pelagic lifestyle and loss of spiracular pit organs (the only character transformation that occurred more than once within pelagic taxa). Depending on the choice of tree, the association was either nonsignificant at P  = 0.06 or significant at P  < 0.05. Future studies, using species within more restricted elasmobranch clades, are needed to resolve this issue.     

Persistence and recovery of regressing 3-mm ovarian follicles in heifers

The persistence and outcome of 3-mm follicles before the emergence of follicular wave 1 were studied every 6 hours in 15 heifers beginning on Day 14 (Day 0 = ovulation). A mean of 9.1 ± 1.3 persistent 3-mm follicles (P3Fs) per heifer was detected with persistence for 3.5 ± 0.1 days. The P3Fs either regressed continuously and remained in the 3-mm range (3.0–3.9 mm) or regressed but with a transient increase in diameter during regression. Some (43%) P3Fs were rescued to become growing follicles in wave 1. The number of follicles that became part of wave 1 was less (P < 0.0001) for follicles that originated from a P3F (4.2 ± 1.0 P3Fs) than for follicles that did not originate from a P3F (11.9 ± 1.6 follicles). The day of rescue of wave 1 follicles from a P3F (Day −1.1 ± 0.6) was earlier (P < 0.001) than for emergence of follicles at 3 mm that did not originate from a P3F (Day −0.5 ± 0.5). A cluster of 5.1 ± 0.6 P3Fs was identified in 10 of 15 heifers by the synchronized peaks of transient diameter increases at the 6-hour interval corresponding to Day −4.0 ± 0.3. Concentrations of FSH oscillated at 12-hour intervals with a peak (P < 0.05) 6 hours before and 6 hours after the beginning of a transient diameter increase during a P3F. Concentration of FSH was greater (P < 0.02) in heifers with a high number (11–18) of P3Fs per heifer (0.27 ± 0.02 ng/mL) than with a low number (2–9) per heifer (0.17 ± 0.008 ng/mL). Results supported the novel hypothesis that 3-mm follicles may persist for two or more days and may be rescued to become growing follicles of wave 1.     

In vitro steroid production by isolated ovarian follicles of the striped trumpeter

Ovarian follicles from striped trumpeter Latris lineata were incubated in L15 medium alone, or medium supplemented with gonadotropin (GtH) preparations (human chorionic GtH, carp maturational GtH or partially purified salmon GtH), testosterone (T) or 17-hydroxyprogesterone (17P). Levels of oestrone (E₁), 17 β -oestradiol (E₂), T, and 17,20 β -dihydroxy-4-pregnen-3-one (17,20 β P) in the medium after incubation were measured by radioimmunoassay. Basal production of E₂ was high from previtellogenic follicles, whereas little T was produced. Both T and E₂ production increased in response to treatment with GtH or steroid precursors. Vitellogenic follicles showed basal production of both T and E₂, and T but not E₂ levels generally increased in response to hormone treatment. Preparations containing follicles nearing final maturation showed low basal production of E₂ but high production of T. Treatment with steroids resulted in little change in E₂ but often very large increases in T production, whereas GtH stimulated lesser increases. 17,20 β P production was detectable from incubations of maturing follicles from two out of five fish, and in those two incubations, increased in response to treatment with 17P. E₁ was not detectable in any incubations. The results indicate that there is a shift in steroidogenesis from E₂ to T production during oocyte development, and provide further evidence that steroid biosynthesis in non-salmonids is principally regulated by substrate availability.     

Contraception within an elasmobranch captive breeding programme: a case report on the eagle ray Aetobatus ocellatus using gonadotrophin-releasing hormone (GnRH) agonist deslorelin (Suprelorin)

This study describes the first case of contraception within a captive elasmobranch breeding programme where an implant of Suprelorin, containing a long-acting gonadotrophin-releasing hormone (GnRH) analogue Deslorelin, was implanted in an eagle ray Aetobatus ocellatus, which successfully halted breeding.     

Effect of follicle size and quality on the ability of follicular fluid to support cytoplasmic maturation of bovine oocytes

Recent studies have shown that the developmental capacity of in vitro-matured oocytes is affected by the origin of follicular fluid (FF) supplemented to the maturation medium. The aims of this study were (1) to determine if follicle size and quality would influence the capacity of FF to support bovine oocyte maturation and (2) to determine if fetal calf serum (FCS) and FF had an additive effect when added together to the maturation medium. Follicular fluid collected from 108 follicles was classified according to size (<6, 6–8, >8 mm in diameter) and quality (healthy, early atretic, and atretic). Quality, first determined by mitosis/pycnosis ratios in granulosa cell smears, was subsequently confirmed by insulin-like growth factor binding protein (IGFBP) patterns and estradiol concentrations. While most small- or medium-sized follicles showed some atresia (88% and 67%, respectively), fewer of the large follicles were atretic (30%). In experiment 1 bovine oocytes (n = 2,152) were matured either in TCM199 alone, with 10% FCS, or with 10% FF from the following follicle types: small healthy (SH); small early atretic (SEA); small atretic (SA); medium healthy (MH); medium early atretic (MEA); medium atretic (MA); large healthy (LH); large early atretic (LEA); and large atretic (LA). Following IVM, oocytes were fertilized and subsequently cultured in synthetic oviduct fluid (SOF). Day 8 blastocyst yields were 23% in TCM199 alone; 37% in TCM199 plus FCS; and, in medium supplemented with FF, SH, 36%; MH, 32%; LH, 30%; SEA, 21%; MEA, 26%; LEA, 28%; SA, 32%; MA, 33%; and LA, 38%. All FF from healthy or atretic follicles resulted in significantly improved blastocyst yields compared to M199 alone (P < 0.05) However, FF from early atretic follicles irrespective of size did not yield a significant improvement. In experiment 2 we examined the effect of addition of FF-LH and serum together to the maturation medium. In terms of blastocyst yield, no additional benefit was observed when TCM199 was supplemented with 10% FCS + 10% FF (33%) compared to 10% FCS or FF alone (35% and 30%, respectively). The efficacy of FF as a supplement to the maturation medium to improve cytoplasmic maturation appears to vary with follicle quality but not size. However, in general, the addition of 10% FF or FCS to the maturation media resulted in a similar blastocyst yield with no additional improvement when media was supplemented with both FCS and FF. © 1996 Wiley-Liss, Inc.     

Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid-May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined.     

The fine structure of the follicular cells in growing and atretic ovarian follicles of the domestic goose

Summary The structure of follicular layer of growing and atretic follicles in the ovary of the domestic goose, was studied by electron microscopy. In small follicles, the wall is lined with a narrow layer of tightly packed small, cuboidal cells separated from the thecal tissue by the basal lamina. During growth, they transform into tall, columnar cells arranged in a single row. The cells display several peculiar ultrastructural features. First, annulate lamellae are commonly observed. Second, cytoplasmic dense-cored granules accumulate in close association with fenestrated cisternae and networks of tubuli derived from the RER. They consist of spheres and strands of amorphous substance of unknown origin. Third, the cells contain many transosomes, a unique organelle of the avian follicle cell consisting of a dense plaque associated with ribosome-like particles. The mature forms of transosomes are located at the tips of lateral and apical cell projections, while bodies thought to be their precursors, are found in the apical cytoplasm. In follicles larger than 8 mm in diameter, most of the transosomes and their precursors have disappeared. Follicular atresia occurs in all of the size-classes of follicles investigated. A loss of transosomes (in follicles up to 8 mm in diameter) and an accumulation of lipid droplets are the first atretic events detectable by electron microscopy. Morphologic features, including deep nuclear indentations, accumulation of lipid droplets frequently encireled by membrane whorls, dilation and disintegration of RER cisterns, swelling of mitochondria and accumulation of dense irregular masses of unknown origin in the cytoplasm, are taken as evidence for advanced degradation. We conclude that necrosis is the dominant type of cell death of the follicular cells during atresia. However, a small fraction of cells, characterized by dark condensed cytoplasm, seems to die by apoptosis.