Comparative innervation of cephalic photophores of the loosejaw dragonfishes (Teleostei: Stomiiformes: Stomiidae): Evidence for parallel evolution of long‐wave bioluminescence

Four genera of the teleost family Stomiidae, the loosejaw dragonfishes, possess accessory cephalic photophores (AOs). Species of three genera, Aristostomias, Malacosteus, and Pachystomias, are capable of producing far‐red, long‐wave emissions (>650nm) from their AOs, a character unique among vertebrates. Aristostomias and Malacosteus posses a single far‐red AO, while Pachystomias possesses anterior and posterior far‐red AOs, each with smaller separate photophores positioned in their ventral margins. The purpose of this study was to establish the primary homology of the loosejaw AOs based on topological similarity of cranial nerve innervation, and subject these homology conjectures to tests of congruence under a phylogenetic hypothesis for the loosejaw dragonfishes. On the basis of whole‐mount, triple‐stained specimens, innervation of the loosejaw AOs is described. The AO of Aristostomias and the anterior AO of Pachystomias are innervated by the profundal ramus of the trigeminal (Tpr), while the far‐red AO of Malacosteus and a small ventral AO of Pachystomias are innervated by the maxillary ramus of the trigeminal (Tmx). The largest far‐red AO of Pachystomias, positioned directly below the orbit, and the short‐wave AO of Photostomias are innervated by a branch of the mandibular ramus of the trigeminal nerve. Conjectures of primary homology drawn from these neuroanatomical similarities were subjected to tests of congruence on a phylogeny of the loosejaws inferred from a reanalysis of a previously published morphological dataset. Optimized for accelerated transformation, the AO innervated by the Tpr appears as a single transformation on the new topology, thereby establishing secondary homology. The AOs innervated by the Tmd found in Pachystomias and Photostomias appear as two transformations in a reconstruction on the new topology, a result that rejects secondary homology of this structure. The secondary homology of AOs innervated by the Tmx found in Malacosteus and Pachystomias is rejected on the same grounds. Two short‐wave cephalic photophores present in all four genera, the suborbital (SO) and the postorbital (PO), positioned in the posteroventral margin of the orbit and directly posterior to the orbit, respectively, are innervated by separate divisions of the Tmd. The primary homologies of the loosejaw PO and SO across loosejaw taxa are proposed on the basis of similar innervation patterns. Because of dissimilar innervation of the loosejaw SO and SO of basal stomiiforms, primary homology of these photophores cannot be established. Because of similar function and position, the PO of all other stomiid taxa is likely homologous with the loosejaw PO. Nonhomology of loosejaw long‐wave photophores is corroborated by previously published histological evidence. The totality of evidence suggests that the only known far‐red bioluminescent system in vertebrates has evolved as many as three times in a closely related group of deep‐sea fishes. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

THE COMPLEX EVOLUTIONARY HISTORY OF SEEING RED: MOLECULAR PHYLOGENY AND THE EVOLUTION OF AN ADAPTIVE VISUAL SYSTEM IN DEEP‐SEA DRAGONFISHES (STOMIIFORMES: STOMIIDAE)

The vast majority of deep‐sea fishes have retinas composed of only rod cells sensitive to only shortwave blue light, approximately 480–490 nm. A group of deep‐sea dragonfishes, the loosejaws (family Stomiidae), possesses far‐red emitting photophores and rhodopsins sensitive to long‐wave emissions greater than 650 nm. In this study, the rhodopsin diversity within the Stomiidae is surveyed based on an analysis of rod opsin‐coding sequences from representatives of 23 of the 28 genera. Using phylogenetic inference, fossil‐calibrated estimates of divergence times, and a comparative approach scanning the stomiid phylogeny for shared genotypes and substitution histories, we explore the evolution and timing of spectral tuning in the family. Our results challenge both the monophyly of the family Stomiidae and the loosejaws. Despite paraphyly of the loosejaws, we infer for the first time that far‐red visual systems have a single evolutionary origin within the family and that this shift in phenotype occurred at approximately 15.4 Ma. In addition, we found strong evidence that at approximately 11.2 Ma the most recent common ancestor of two dragonfish genera reverted to a primitive shortwave visual system during its evolution from a far‐red sensitive dragonfish. According to branch‐site tests for adaptive evolution, we hypothesize that positive selection may be driving spectral tuning in the Stomiidae. These results indicate that the evolutionary history of visual systems in deep‐sea species is complex and a more thorough understanding of this system requires an integrative comparative approach.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Long-term treadmill exercise improves spatial memory of male APPswe/PS1dE9 mice by regulation of BDNF expression and microglia activation

Increasing evidence suggests that physical activity could delay or attenuate the symptoms of Alzheimer''s disease (AD). But the underlying mechanisms are still not fully understood. To investigate the effect of long-term treadmill exercise on the spatial memory of AD mice and the possible role of β-amyloid, brain-derived neurotrophic factor (BDNF) and microglia in the effect, male APPswe/PS1dE9 AD mice aged 4 months were subjected to treadmill exercise for 5 months with 6 sessions per week and gradually increased load. A Morris water maze was used to evaluate the spatial memory. Expression levels of β-amyloid, BDNF and Iba-1 (a microglia marker) in brain tissue were detected by immunohistochemistry. Sedentary AD mice and wildtype C57BL/6J mice served as controls. The results showed that 5-month treadmill exercise significantly decreased the escape latencies (P < 0.01 on the 4th day) and improved the spatial memory of the AD mice in the water maze test. Meanwhile, treadmill exercise significantly increased the number of BDNF-positive cells and decreased the ratios of activated microglia in both the cerebral cortex and the hippocampus. However, treadmill exercise did not significantly alleviate the accumulation of β-amyloid in either the cerebral cortex or the hippocampus of the AD mice (P > 0.05). The study suggested that long-term treadmill exercise could improve the spatial memory of the male APPswe/PS1dE9 AD mice. The increase in BDNF-positive cells and decrease in activated microglia might underpin the beneficial effect.     

Comparative neurochemical features of the innervation patterns of the gut of the basal actinopterygian,Lepisosteus oculatus,and the euteleost,Clarias batrachus

The structure and physiology of enteric system are very similar in all classes of vertebrates, although they have been investigated only occasionally in non‐mammalian vertebrates. Very little is known about the distribution of the neurotransmitters in the gut of actinopterygian fishes. Anatomical and physiological studies of enteric nervous systems in the spotted gar (Lepisosteus oculatus) and airbreathing catfish (Clarias batrachus), a non‐teleost and teleost actinopterygian, respectively, have not been undertaken. This study provides the first comprehensive characterization of the range of neurochemical coding in the enteric nervous system of these two species, including the chemical diversity of the mucosal endocrine cells in the pyloric stomach of Clarias. Autonomic innervation of the secretory glands is also described and reported herein for the first time for fishes. We also report splanchnic (spinal) innervation of the stomach, submucosal ganglia (that also colocalize with nNOS) and caudal intestine of Clarias. In both fish species, numerous 5HT, ChAT, nNOS and TH‐positive nerve fibres have been observed. These discoveries demonstrate that much more physiological and pharmacological data are needed before a comprehensive model of enteric nervous system control in vertebrates can be developed.     

Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822)

Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l^?1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and duration- dependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l^?1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled.