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1. The effects of age, sex, and habitat on body size and shape of the blackstripe topminnow, Fundulus notatus (Cyprinodontiformes: Fundulidae) (Rafinesque 1820): Size and Shape of the Blackstripe Topminnow

   https://doi.org/10.1111/bij.12022  

   Welsh, Daniel P. ; Zhou, Muchu ; Mussmann, Steven M. ; Fields, Lauren G. ; Thomas, Claire L. ; Pearish, Simon P. ; Kilburn, Stephanie L. ; Parker, Jerrod L. ; Stein, Laura R. ; Bartlett, Jennifer A. ; et al ( April 2013 , Biological Journal of the Linnean Society)
2. Variable rates of hybridization among contact zones between a pair of topminnow species, Fundulus notatus and F. olivaceus

   https://doi.org/10.1002/ece3.10399  

   Duvernell, David D. ; Remex, Naznin S. ; Miller, Jeffrey T. ; Schaefer, Jacob F. ( August 2023 , Ecology and Evolution)

   Pairs of species that exhibit broadly overlapping distributions, and multiple geographically isolated contact zones, provide opportunities to investigate the mechanisms of reproductive isolation. Such naturally replicated systems have demonstrated that hybridization rates can vary substantially among populations, raising important questions about the genetic basis of reproductive isolation. The topminnows,Fundulus notatusandF. olivaceus, are reciprocally monophyletic, and co‐occur in drainages throughout much of the central and southern United States. Hybridization rates vary substantially among populations in isolated drainage systems. We employed genome‐wide sampling to investigate geographic variation in hybridization, and to assess the possible importance of chromosome fusions to reproductive isolation among nine separate contact zones. The species differ by chromosomal rearrangements resulting from Robertsonian (Rb) fusions, so we hypothesized that Rb fusion chromosomes would serve as reproductive barriers, exhibiting steeper genomic clines than the rest of the genome. We observed variation in hybridization dynamics among drainages that ranged from nearly random mating to complete absence of hybridization. Contrary to predictions, our use of genomic cline analyses on mapped species‐diagnostic SNP markers did not indicate consistent patterns of variable introgression across linkage groups, or an association between Rb fusions and genomic clines that would be indicative of reproductive isolation. We didmore »observe a relationship between hybridization rates and population phylogeography, with the lowest rates of hybridization tending to be found in populations inferred to have had the longest histories of drainage sympatry. Our results, combined with previous studies of contact zones between the species, support population history as an important factor in explaining variation in hybridization rates.

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3. Intra- and Intersexual swim bladder dimorphisms in the plainfin midshipman fish ( Porichthys notatus ): Implications of swim bladder proximity to the inner ear for sound pressure detection

   https://doi.org/10.1002/jmor.20724  

   Mohr, Robert A. ; Whitchurch, Elizabeth A. ; Anderson, Ryan D. ; Forlano, Paul M. ; Fay, Richard R. ; Ketten, Darlene R. ; Cox, Timothy C. ; Sisneros, Joseph A. ( November 2017 , Journal of Morphology)
4. Melatonin receptor expression in vocal, auditory, and neuroendocrine centers of a highly vocal fish, the plainfin midshipman ( Porichthys notatus )

   https://doi.org/10.1002/cne.24629  

   Feng, Ni Y. ; Marchaterre, Margaret A. ; Bass, Andrew H. ( January 2019 , Journal of Comparative Neurology)

   Melatonin plays a central role in entraining activity to the day–night cycle in vertebrates. Here, we investigate neuroanatomical substrates of melatonin‐dependent vocal–acoustic behavior in the nocturnal and highly vocal teleost fish, the plainfin midshipman (Porichthys notatus). Using in situ hybridization (ISH) and quantitative real‐time PCR (qPCR), we assess the mRNA distribution and transcript abundance of melatonin receptor subtype 1B (mel1b), shown to be important for vocalization in midshipman fish and songbirds. ISH shows robustmel1bexpression in major nodes of the central vocal and auditory networks in the subpallium, preoptic area (POA), anterior hypothalamus, dorsal thalamus, posterior tuberculum, midbrain torus semicircularis and periaqueductal gray, and hindbrain.Mel1blabel is also abundant in secondary targets of the olfactory, visual, and lateral line systems, as well as telencephalic regions that have been compared to the amygdala, extended amygdala, striatum, septum, and hippocampus of tetrapods. Q‐PCR corroboratesmel1babundance throughout the brain and shows significant increases in the morning compared with nighttime in tissue samples inclusive of the telencephalon and POA, but remains stable in other brain regions. Plasma melatonin levels show expected increase at night. Our findings support the hypothesis that melatonin's stimulatory effects on vocal–acoustic mechanisms in midshipman is mediated, in part, by melatonin bindingmore »in vocal, auditory, and neuroendocrine centers. Together with robustmel1bexpression in multiple telencephalic nuclei and sensory systems, the results further indicate an expression pattern comparable to that in birds and mammals that is indicative of melatonin's broad involvement in the modulation of physiology and behavior.

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5. Metabolic rates from Bluntnose minnow ( Pimephales notatus ) populations at lower latitudes are more sensitive to changes in temperature than populations at higher latitudes

   https://doi.org/10.1111/eff.12507  

   Beachum, Collin E. ; Michel, Matt J. ; Knouft, Jason H. ( October 2019 , Ecology of Freshwater Fish)

   Predicting the potential effects of changes in climate on freshwater species requires an understanding of the relationships between physiological traits and environmental conditions among populations. While water temperature is a primary factor regulating metabolic rates in freshwater ectotherms, how metabolic rates vary across the species range is unclear. In addition, photoperiod has also been hypothesised to influence metabolic rates in freshwater taxa based on seasonal changes in activity rates. Using an experimental approach, we investigated whether variation in routine metabolic rate (RMR) and sensitivity of RMR to changes in temperature are correlated with local thermal regimes, photoperiods and body mass among ten populations across the geographic range of the Bluntnose minnow (Pimephales notatus), a North American freshwater fish species. Routine metabolic rate data were collected from populations acclimatised to three temperature treatments (9, 18 and 27°C) and correlated with water temperature and photoperiod estimates at collection locations for each population. Routine metabolic rate was negatively correlated with minimum photoperiod at 9°C, negatively correlated with weekly high temperature at 18°C and positively correlated with weekly high temperature at 27°C. Body mass was also a predictor of RMR at each temperature treatment. Thermal sensitivity of RMR was positively correlated with weeklymore »high temperature, indicating that individuals from warmer low latitude populations experienced greater sensitivity of RMR to changes in temperature than individuals from cooler high latitude populations. These results indicate differential responses among populations to variation in temperature and suggest the importance of recognising this variation when characterising responses of freshwater taxa to increases in water temperature.

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