Ultrastructure of the Juxtaganglionar Organ, a Putative Endocrine Gland Associated with the Cerebral Ganglia of<i>Aplysia juliana</i>

Switzer-Dunlap, Marilyn

doi:10.1080/01688170.1987.10510288

Cited by 6 publications

(6 citation statements)

References 15 publications

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“…Physiological characteristics of dorsal bodies suggest that these glands are inactive in virgin snails, are activated by mating, and remain active during the reproductive phase of the organisms (Joosse and Geraerts 1983;Khan et al 1990;Saleuddin et al 1997). Ultrastructural analyses have suggested that the juxtaganglionar organ of prosobranch snails may be analogous to the dorsal bodies (Switzer-Dunlap 1987).…”

Section: Hormonal Control Of Sexual Differentiation and Reproduction mentioning

confidence: 97%

Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs

et al. 2009

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Prosobranch snails have been afflicted globally by a condition whereby females develop male sex characteristics, most notably a penis. This condition, known as imposex, has been causally associated with the ubiquitous environmental contaminant tributyltin (TBT). Deduction of the mechanism by which TBT causes imposex has been hampered by the lack of understanding of the normal endocrine regulation of reproductive tract recrudescence in these organisms. We have reviewed the relevant literature on the environmental and endocrine factors that regulate reproductive tract recrudescence, sexual differentiation, and reproduction in gastropods. We provide a cohesive model for the environmental-endocrine regulation of reproduction in these organisms, and use this information to deduce a most likely mechanism by which TBT causes imposex. Photoperiod appears to be the predominant environmental cue that regulates reproductive tract recrudescence. Secondary cues include temperature and nutrition which control the timing of breeding and egg laying. Several hormone products of the central and peripheral nervous systems have been identified that contribute to recrudescence, reproductive behaviors, oocyte maturation and egg laying. Retinoic acid signaling via the retinoid X-receptor (RXR) has shown promise to be a major regulator of reproductive tract recrudescence. Furthermore, TBT has been shown to be a high affinity ligand for the RXR and the RXR ligand 9-cis retinoic acid causes imposex. We propose that TBT causes imposex through the inappropriate activation of this signaling pathway. However, uncertainties remain in our understanding of the environmental-endocrine regulation of reproduction in gastropods. Definitive elucidation of the mechanism of action of TBT awaits resolution of these uncertainties.

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Section: Hormonal Control Of Sexual Differentiation and Reproduction mentioning

confidence: 97%

Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs

et al. 2009

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“…Such organs were first reported in acochlidian species for the hermaphroditic Hedylopsis ballantinei and H. spiculifera by Sommerfeldt and Schrödl (2005). While Huber (1993) regarded dorsal bodies as an autapomorphy of pulmonates, similar structures called "juxtaganglionar organ" were additionally found in aplysiid opisthobranchs, especially during the period of female gonad development, in the gymnosome Hydromeles, and in both sexes of a number of gonochoric prosobranchs (Martoja, 1965a,b;Switzer-Dunlap, 1987). Based on the ultrastructural and neurosecretory function of female gonadotropic factors, dorsal bodies and juxtaganglionar organs were considered homologous by Switzer-Dunlap (1987).…”

Section: Nervous Systemmentioning

confidence: 97%

Computer-based three-dimensional reconstruction of the anatomy ofMicrohedyle remanei (Marcus, 1953), an interstitial acochlidian gastropod from Bermuda

et al. 2006

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Phylogenetic analysis of the highly enigmatic and aberrant acochlidian opisthobranch gastropods is mainly hindered by the lack of reliable anatomical data. Due to their small size, marine interstitial acochlidian species are not suitable for anatomical investigations by dissecting. The tinyness and complexity of, e.g., opisthobranch central nervous and reproductive systems make data derived from older paraffin-based histology and interpretation by hand-based graphical reconstruction questionable. In a former study, a hermaphroditic member of the basal acochlidian genus Hedylopsis ("Hedylopsacea") has been examined in detail. The present study uses the gonochoric Microhedyle remanei (Microhedylidae) as a model organism of the other traditional major acochlidian subgroup, the "Microhedylacea." More than 20 specimens with up to 2 mm body length were extracted from coarse subtidal sand near Castle Roads, Bermuda Islands. Their central nervous, digestive, circulatory, excretory, and genital systems were reconstructed three-dimensionally from serial semithin histological sections using AMIRA software. The radula was analyzed by SEM. Our specimens closely resemble the original description of M. remanei (Marcus, 1953; as Unela) from Brazil; apparent differences regarding the number of visceral loop ganglia or details of male genitalia are assumed to be due to oversights by the former author or because of different ontogenetic stages. Microhedyle remanei differs from all congeners due to the lack (vs. presence) of eyes; further distinguishing features are discussed. In contrast to members of the hedylopsacean Hedylopsidae, Acochlidiidae, and Tantulidae, M. remanei shows a nervous system with numerous precerebral accessory "ganglia" that are not differentiated into cortex and medulla. While all Microhedylidae previously were thought to lack a heart, M. remanei shows a two-chambered heart, as is usual for opisthobranchs. The oocytes of M. remanei are yolky and large in relation to body size and suggest intracapsular larval development. A comparative microanatomical discussion and the distribution of characters within acochlidian taxa indicate that the current classification of the Acochlidia does not reflect phylogenetic relationships. Detailed structural investigations on further poorly known species are required; the computer-based 3D reconstruction of semithin serial sections with AMIRA is shown to be an ideal tool for efficient analysis and presentation of the microanatomy of small specimens.

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“…Identical organs have been described from basommatomorphan pulmonates (see Switzer-Dunlap, 1987) and are commonly regarded as an autapomorphy for pulmonates (see Huber, 1993). However, their presence seems plesiomorphic not only for euthyneurans; similar, but less concentrated neurosecretory tissues associated with the cerebral ganglia ('juxtaganglionar organ') have also been detected in aplysiid opisthobranchs, the gymnosome Hydromeles, and several prosobranchs such as Patella, Trochocochlea, Diodora and Haliotis, especially during the period of female gonad maturation (Martoja, 1965a, b;Switzer-Dunlap, 1987). Careful studies will ultimately reveal dorsal bodies to be present in other acochlidian species and other opisthobranch groups as well, and their special structure and functions might have some phylogenetic significance.…”

Section: Morphologymentioning

confidence: 99%

Microanatomy Of Hedylopsis Ballantinei, A New Interstitial Acochlidian Gastropod From The Red Sea, And Its Significance For Phylogeny

Sommerfeldt

Schrödl

2005

Journal of Molluscan Studies

120

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This is the first description of an acochlidian gastropod species from the Red Sea. More than 20 specimens of Hedylopsis ballantinei n. sp. have been extracted from subtidal coral sand in the Gulf of Aqaba. As a model organism for this poorly known, highly aberrant and enigmatic opisthobranch group, the anatomy of this new species is described in detail. Major organ systems have been reconstructed from histological semithin serial sections. The central nervous system has also been studied by means of immunocytochemical staining and confocal laser scanning techniques; dorsal bodies and rhinophoral ganglia are described for the first time for Acochlidia. Hardparts were examined using SEM, the midpiece of an acochlidian sperm is described with aid of TEM for the first time. Our results show Hedylopsis ballantinei n. sp. to be similar to the European H. spiculifera (junior synonym H. suecica). Differences include tropical occurrence, larger rhinophoral ganglia, different arrangement of ampulla and genital glands, and the probable absence of anterior male genitalia. Hedylopsis ballantinei n. sp. plays an important role in understanding acochlidian phylogeny, since it combines an array of morphological features that appear plesiomorphic for Acochlidia, e.g. a (small) mantle cavity, a unidirectional stomach lacking any cuticular elements, a tube-like, holohepatic digestive gland, a prepharyngeal, epiathroid central nervous system with separate cerebral, pleural and pedal ganglia, dorsal bodies associated with the cerebral ganglia, a (short) visceral loop with three ganglia, a monaulic and hermaphroditic reproductive system, and elongate spiral sperm. On the other hand, the absence of anterior male genitalia appears to be a derived condition that is shared with microhedylacean species. The aberrant possession of three glycogen helices in the sperm midpiece appears unique for opisthobranchs. With present, limited knowledge, the Acochlidia is regarded as a monophyletic group that is supported by several autapomorphies, with a hypothetical origin from acteonoidean opisthobranchs, i.e. diaphanid-like ancestors.

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Ultrastructure of the Juxtaganglionar Organ, a Putative Endocrine Gland Associated with the Cerebral Ganglia ofAplysia juliana

Cited by 6 publications

References 15 publications

Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs

Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs

Computer-based three-dimensional reconstruction of the anatomy ofMicrohedyle remanei (Marcus, 1953), an interstitial acochlidian gastropod from Bermuda

Microanatomy Of Hedylopsis Ballantinei, A New Interstitial Acochlidian Gastropod From The Red Sea, And Its Significance For Phylogeny

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