A previous study reported that a peptide, sensorin-A, is expressed exclusively in mechanosensory neurons having somata in central ganglia of Aplysia. The present study utilized in situ hybridization, staining by nerve back-fill and soma injection, and electrophysiological methods to characterize the locations, numbers, and functions of sensorin-A-expressing neurons and to define the relationships between soma locations and the locations of peripheral axons and receptive fields. Approximately 1,000 cells express sensorin-A mRNA in young adult animals (10-30 g) and 1,200 cells in larger adults (100-300 g). All of the labeled somata are in the CNS, primarily in the abdominal LE, rLE, RE and RF, pleural VC, cerebral J and K, and buccal S clusters. Expression also occurs in a few sparsely distributed cells in most ganglia. Together, receptive fields of all these mechanosensory clusters cover the entire body surface. Each VC cluster forms a somatotopic map of the ipsilateral body, a "sensory aplunculus." Cells in the pleural and cerebral clusters have partially overlapping sensory fields and synaptic targets. Buccal S cells have receptive fields on the buccal mass and lips and display notable differences in electrophysiological properties from other sensorin-A-expressing neurons. Neurons in all of the clusters have relatively high mechanosensory thresholds, responding preferentially to threatening or noxious stimuli. Synaptic outputs to target cells having defensive functions support a nociceptive role, as does peripheral sensitization following noxious stimulation, although additional functions are likely in some clusters. Interesting questions arise from observations that mRNA for sensorin-A is present not only in the somata but also in synaptic regions, connectives, and peripheral fibers. (C) 2004 Wiley-Liss, Inc.

AbstractA previous study reported that a peptide, sensorin‐A, is expressed exclusively in mechanosensory neurons having somata in central ganglia of Aplysia. The present study utilized in situ hybridization, staining by nerve back‐fill and soma injection, and electrophysiological methods to characterize the locations, numbers, and functions of sensorin‐A‐expressing neurons and to define the relationships between soma locations and the locations of peripheral axons and receptive fields. Approximately 1,000 cells express sensorin‐A mRNA in young adult animals (10–30 g) and 1,200 cells in larger adults (100–300 g). All of the labeled somata are in the CNS, primarily in the abdominal LE, rLE, RE and RF, pleural VC, cerebral J and K, and buccal S clusters. Expression also occurs in a few sparsely distributed cells in most ganglia. Together, receptive fields of all these mechanosensory clusters cover the entire body surface. Each VC cluster forms a somatotopic map of the ipsilateral body, a “sensory aplunculus.” Cells in the pleural and cerebral clusters have partially overlapping sensory fields and synaptic targets. Buccal S cells have receptive fields on the buccal mass and lips and display notable differences in electrophysiological properties from other sensorin‐A‐expressing neurons. Neurons in all of the clusters have relatively high mechanosensory thresholds, responding preferentially to threatening or noxious stimuli. Synaptic outputs to target cells having defensive functions support a nociceptive role, as does peripheral sensitization following noxious stimulation, although additional functions are likely in some clusters. Interesting questions arise from observations that mRNA for sensorin‐A is present not only in the somata but also in synaptic regions, connectives, and peripheral fibers. J. Comp. Neurol. 471:219–240, 2004. © 2004 Wiley‐Liss, Inc.

Mechanosensory threshold of tail sensory neurons in Aplysia was tested after injecting the tail with neuromodulators known to affect defensive behavior in this animal. Serotonin (5-HT) and small cardioactive peptide (SCPB) reduced peripheral threshold, while FMRFamide, acetylcholine (ACh), and dopamine increased threshold. FMRFamide and ACh also reduced spontaneous activity of sensory neurons. Glutamate and taurine had no effect. SCPB effects persisted for 15–30 min after washout. Functional similarities between peripheral and central effects of these neuromodulators support the hypothesis of coordinate modulation of both regions of the sensory neuron by the same set of modulators following noxious stimulation.

Journal of ZoologyVolume 215, Issue 1 p. 55-81 Observations on the embryology of the unisexual lizard Cnemidophorus uniparens (Teiidae) Allen J. Billy, Allen J. Billy Department of Physiology and Cell Biology, University of Texas Medical School, Health Science Center, P.O. Box 20708. Houston, Texas, USA 77225Search for more papers by this author Allen J. Billy, Allen J. Billy Department of Physiology and Cell Biology, University of Texas Medical School, Health Science Center, P.O. Box 20708. Houston, Texas, USA 77225Search for more papers by this author First published: May 1988 https://doi.org/10.1111/j.1469-7998.1988.tb04885.xCitations: 4 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat REFERENCES Billy, A. J. (1987). Developmental deformities in Cnemidophorus uniparens (Teiidae) and the anomalous male phenomenon. Can. J. Zool. 64: 2418–2424. 10.1139/z86-361 Web of Science®Google Scholar Billy, A. J. & Crews, D. (1986). 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Cnemidophorus uniparens is a parthenogenetic unisexual lizard species in which each individual develops as a female. Male C. uniparens are unknown, but slightly masculinized animals were produced by administering consecutive pre- and post-hatching testosterone treatments. The present study sought to delineate and characterize the testosterone-sensitive period in C. uniparens development. In one experiment, multiple pre-hatching testosterone treatments influenced oviducal and femoral gland development whereas a single pre-hatching treatment did not, indicating that testosterone sensitivity exists in embryonic life. In a second experiment, 30- or 90-day testosterone treatments administered to juvenile animals produced no effects on morphological development, indicating that testosterone sensitivity is lost by the juvenile stage of development. The testosterone-sensitive period in C. uniparens development begins during the pre-hatching period, extends through at least the 1st month after hatching, and ends by the juvenile stage.

Parthenogenetic species of lizard occasionally produce male progeny characterized by developmental defects and low viability. Production of anomalous males is an unresolved problem in sexual differentiation as parthenogenetic female lizards are expected to produce female offspring. The "anomalous male" phenomenon was examined by sexing nonviable embryos produced by the parthenogenetic whiptail lizard Cnemidophorus uniparens. Twenty-six deformed embryos were obtained; all were female except for three which did not possess gonads. Male embryos were not detected. Developmental deformities found in Cnemidophorus embryos included anophthalmia, micropthalmia, encephalocoele, hypoplasia of the lower jaw, head foreshortening, gastroschisis, and malformations of the vertebral column. Several embryos possessed a combination of defects. Four hypotheses are presented to account for production of anomalous males by reptilian parthenoforms. Three hypotheses involve production of sex-reversed males (genetic females). A fourth hypothesis asserts that anomalous males are derived from hybridization events between a female from a unisexual species and a male from a bisexual species. Of the four hypotheses, the hybridization hypothesis has the greatest utility in explaining production of anomalous males by parthenogenetic lizards.

Cnemidophorus uniparens is a parthenogenetic unisexual species of lizard in which each individual develops as a female, making it a unique animal model for the study of sexual differentiation. In one study, administration of exogenous testosterone before and/or after hatching influenced the development of the gonads, the accessory reproductive ducts, the renal sex segment of the mesonephric kidney, and the femoral glands, a secondary sex character. Testosterone treatment also affected the cross‐sectional area of the gonad and the proportions of cortical and medullary tissues present in the developing gonad. The oviducts and femoral glands of testosterone‐treated individuals were hypertrophied; the collecting tubules of the kidney of these animals contained granules, an androgen‐dependent, sexually dimorphic character in squamate reptiles. In another study, testosterone, dihydrotestosterone, or estradiol were administered to C. uniparens embryos. No treatment effects on gonadal development were detected on the day of hatching. However, estradiol, but not testosterone and dihydrotestosterone, stimulated development of the oviducts. Taken together these studies suggest that androgen aromatization may play a role in sexual differentiation in lizards.

A quantitative analysis of the relationship between pseudocopulatory behaviour and the ovarian cycle in the parthenogenetic lizard Cnemidophorus uniparens indicates (1) that this behaviour is frequently and regularly expressed by captive individuals, and (2) that the sexual role, either male-like or female-like, exhibited by an animal is correlated with its ovarian state. The expression of female-like behaviour patterns was associated with and primarily limited to the vitellogenic stage of the cycle. Male-like behaviour patterns occurred most frequently during post-ovulatory stages but was not limited to these stages. Neither behavioural role was ever expressed by non-reproductive individuals. Reproductive individuals often alternated in assuming the female-like and male-like roles during the progress of the ovarian cycle. These observations suggest that pseudosexual behaviour is hormonally activated in this species. However, it also appears that the prevailing social situation is an important factor determining which behavioural role is taken. This work strengthens the hypothesis that pseudosexual behaviour in all-female lizards occurs as the result of natural selection.

Groups of Sarotherodon mossambicus were treated with androgen by immersion or oral treatment at various stages of development. Fish were allowed to mature and the effects of treatment on gonadal and behavioral differentiation were examined. The effects of treatment on gonadal differentiation were assessed by determining the sex ratio for each group. Three treatments resulted in sex ratios significantly different from the 1:1 sex ratio obtained in untreated fish. Behavioral differences were detected between groups of males in three measures of territorial defense and aggression, and differences were detected between groups of females in two measures of male-female courtship interaction. A second experiment determined that early-treated females were more sensitive to a second androgen treatment later in life than females not exposed to androgen during development. A number of sex-reversed genetic females functioning as males were detected in two treatment groups with predominantly male sex ratios. There were no differences in the behavior of sex-reversed and non-sex-reversed male fish from the same treatment group. This study establishes that hormone treatments administered during development influence behavioral differentiation in a teleost.

Two groups of 30 Sarotherodon mossambicus were weighed and measured when alive, after 5 days in 10% formalin, and after 5, 10, 15, 20, 25, 30 and 65 days in 37.5% isopropyl alcohol. Fish from two size classes were preserved and all fish initially increased slightly in length and increased greatly in weight. The greatest increases in length and weight were noted after 5 days in formalin solution. After 65 days in isopropyl alcohol, the length of the preserved fish decreased to approach the live length while the weight of the fish stabilized at a higher than live weight value. This study is the first report of slight length increases or no shrinkage in preserved fish. Comments on the use of standard correction factors for lengthweight studies of preserved fish are provided.