Branching patterns of the afferent branchial arteries and their phylogenetic significance in rays (Batoidea)

Rays of the superorder Batoidea comprise the most diverse group of chondrichthyans in terms of valid species and morphological disparity. Up to the present little agreement is observed in studies based on morphological and molecular data focused on uncovering the interrelationships within Batoidea. Morphology-based phylogenies of batoids have not included characters related to the afferent branchial arteries, and little is known about the variation in this anatomical complex in rays. Herein, representatives of 32 genera from 19 families currently recognized of rays were examined as well as some shark taxa. Seven new characters are proposed and tested in two different analyses, one on their own and in the other they were added to the morphological data matrix of the most recent analysis of interrelationships within Batoidea. The arrangement of afferent branchial arteries differs mainly among orders and families of batoids. The absence of a common trunk from which the three posteriormost afferent arteries branch is interpreted as a synapomorphy for Myliobatiformes and the presence of a coronary cranial artery as an autapomorphy for Mobula hypostoma. A close spatial relationship between the second and third afferent arteries within the common branch from the ventral aorta is proposed as a synapomorphy for Rajiformes with a secondary modification in Sympterygia. Data about patterns in afferent branchial arteries in additional taxa such as Squaliformes and Chimaeriformes are needed to better understand the evolution of this character complex among chondrichthyans.

Role of NO in arterial vascular function of intertidal fish (Girella laevifrons) and marine fish (Isacia conceptionis)

Previous studies performed in intertidal fish (Girella laevifrons),as well as marine fish (Isacia conceptionis), showed that acetylcholine (ACh) produced contractions mediated by cyclooxygenases that were dependent on the area and potency of contraction in several arterial vessels. Given that the role of nitric oxide is poorly understood in fish, the objective of our study was to evaluate the role of nitric oxide in branchial afferent (ABA), branchial efferent (ABE), dorsal (DA) and mesenteric (MA) arterial vessels from both Girella laevifrons and Isacia conceptionis. We studied afferent and efferent branchial, dorsal and mesenteric arteries that were dissected from 6 juvenile specimens. Isometric tension studies were done using dose response curves (DRC) for Ach (10–13 to 10–3 M) and blockade with L-NAME (10–5 M), and DRC for sodium nitroprusside (SNP, a donor of NO). L-NAME produced an attenuation of the contractile response in the dorsal, afferent and efferent branchial arteries and a potentiation of the contraction in the MA. SNP caused 70% dilation in the mesenteric artery and 40% in the dorsal artery. Our results suggest that Ach promotes precarious dilatation in MA mediated by NO; data that is supported by the use of sodium nitroprusside. In contrast, in the vessels DA, ABA and EBA our results support that the pathway Ach-NO-relaxation is absent in both species.

A Unique Vascular Configuration among the Efferent Branchial Arteries and Splanchnic Arteries in the Yellow Stingray, Urobatis jamaicensis

With light and scanning electron microscopy of vascular corrosion casts, we have observed in Urobatis jamaicensis that the fourth epibranchial arteries do not merge completely with the dorsal aorta. Instead they form a brief anastomosis with a short vessel projecting ventrally from the dorsal aorta and maintain their integrity as separately distinct vessels. Posterior to the anastomosis, the right epibranchial becomes the celiac trunk and left epibranchial becomes the anterior mesenteric artery/posterior intestinal artery. This vascular configuration appears to be unique in elasmobranchs.

Control of vascular tone in notothenioid fishes is determined by phylogeny, not environmental temperature

We examined potential vasomotor control mechanisms in an Antarctic fish ( Trematomus bernacchii; usual core temperature approximately −1°C), comparing sensitivity to agonists by means of the cumulative dose response and potency with reference to depolarization by 50 mM KCl. In efferent branchial arteries, norepinephrine (NE) produced ∼20% of the maximal KCl tension and ∼40% in the presence of 10−3M sotalol, suggesting a modest contribution of α- and β-adrenergic tonus [half-maximal response (pEC50) = 6.29 ± 0.37 M]. Carbachol (CBC) and serotonin (5-HT) had different sensitivities (pEC50 = 4.50 ± 0.40 and 6.82 ± 0.08 M, respectively) but similar potencies (21.6 ± 11.1 and 31.1 ± 5.3% of KCl). A related species from warmer waters around New Zealand, Paranotothenia angustata, had similar vascular reactivity for NE (pEC50 = 5.48 ± 0.31 M), CBC (pEC50 = 4.94 ± 0.22 M), and methysergide-sensitive vasoconstriction with 5-HT (pEC50 = 6.22 ± 0.40 M). Agonist potencies were 9, 65, and 45% that of KCl, respectively. Bovichtus variegatus, a member of the phylogenetic sister group to the notothenioids, also gave broadly similar responses. In contrast, Dissostichus mawsoni, a pelagic Antarctic notothenioid, showed a dominance of vasodilatation over vasoconstriction, with sensitive isoprenaline (pEC50 = 6.66 ± 0.05 M) but weak serotonergic (5.2 ± 1.5% KCl) responses. The unusual dominance of serotonergic control appears to be primarily a consequence of evolutionary lineage rather than low environmental temperature, but the pattern may be modified according to functional demand.

Anatomy and adrenergic pharmacology of the coronary vascular bed of Pacific blue marlin (Makaira nigricans)

Coronary blood supply to the heart of Pacific blue marlin (Makaira nigricans) is derived principally from efferent branchial arteries of the third gill arch via the hypobranchial arteries. A single coronary artery courses caudally from the hypobranchial arteries along the dorsal aspect of the bulbus arteriosus to the ventricle wall in which it branches extensively. Arterial branches invest the compact myocardial shell, trabeculated myocardium, and the atrium. In common with coronary vascular beds of higher vertebrates, marlin coronary vascular beds contained α-constrictor adrenoceptors and β-dilator adrenoceptors.

Évocation des travaux français sur Latimeria notamment depuis 1972

French research on Latimeria published before 1972 is first briefly recalled. After the Anglo-Franco-American Expedition of 1972, the material obtained enabled us to focus attention on the histology of the kidney and ureter and on ultrastructural aspects of the postanal gland. Ovarian eggs of unusual volume have been collected, measured and weighed. Kinematic analysis of the intracranial articulation was carried out in 1973 on a frozen coelacanth that reached Paris. Studies in 1974 of a 41 cm specimen, the smallest known at that time and estimated to be 3½ years old, showed that the brain still filled the cranial cavity: thus, it is later that allometric growth of the cranial cavity relegates the brain to the posterior part of the skull. In the same specimen, radiographed after injection with colloidal barium oxide, we were able to specify the likely role of the contractile organs fused to the branchial arteries: they may serve to regulate arterial pressure in the head during sudden movements of the jaws, and thus of the anterior cranium, as prey is captured. Lastly, the structural characteristics of the teeth, scale denticles, and spines on the lepidotrichia have been revealed, as also has the lamellar structure of the scales, in which there is a crossed orientation of the fibres in the different layers. Brève évocation des travaux français effectués sur Latimeria avant 1972. Après l’expédition anglo-franco-américaine de 1972 le matériel obtenu a permis une mise au point de l'histologie du rein, de l’uretère et des aspects ultra-structuraux de la glande postanale. Des ovules nus d’un volume inusité, ont été recueillis, mesurés et pesés. Une analyse des mouvements de l’articulation intracrânienne a été réalisée en 1973 sur un coelacanthe arrivé congelé à Paris. En 1974, un spécimen de 41 cm, le plus petit à cette époque, a fait voir qu’à ce stade, dont l’âge a été évalué à trois ans et demi, l’encéphale emplissait encore la cavité crânienne; c’est done plus tard que la cavité crânienne subit une croissance allo-métrique reléguant le cerveau dans l’arrière crâne. Par ce même spécimen, soumis à la cinéradiographie avec injection à la baryte colloïdale, le rôle vraisemblable des organes contractiles greffés sur les artères branchiales a pu être précisé: ils doivent servir à une régulation de la pression artérielle céphalique lors des mouvements brusques des mâchoires, et par conséquent de l’avant-crâne, dans la capture des proies. Enfin l’identité structurale des dents, des denticules des écailles et des épines superficielles des lépidotriches a été mise en évidence, ainsi que la structure lamellaire des écailles avec une orientation régulièrement décalée des fibres de ses différentes couches.

The Role of the Cardiac Vagus in the Response of the Dogfish Scyliorhinus Canicula to Hypoxia

1. During normoxia, heart rate was governed by a vagal tone which increased at higher acclimation temperatures. This tonic influence was exerted predominantly via the branchial cardiac nerves. The increase in heart rate following atropinization or cardiac vagotomy was associated with a reduction in stroke flow in the ventral aorta in accordance with Starling's Law of the heart. 2. During slowly induced hypoxia there was a reflex bradycardia, the onset and extent of which varied with acclimation temperature, and which was mediated predominantly via the pair of branchial cardiac vagi. The branchial cardiac vagi were also wholely responsible for the transient marked bradycardia at the onset of rapidly induced hypoxia. 3. Direct measurement of blood flow to the anterior two pairs of branchial arteries demonstrated that they received approximately 37% of total cardiac output in normoxia and that this proportion was unchanged during hypoxia. 4. The bradycardia during hypoxia in control animals was partially offset by a rise in cardiac stroke volume so that cardiac output decreased slightly. Injection of the adrenergic -receptor blocker, Propranolol, abolished the increase in stroke flow during hypoxia, but did not effect the bradycardia, and the total blood flow was therefore reduced. 5. The values of PO2 during hypoxia from fish acclimated to 17 °C were significantly reduced from the control values following atropinization and either branchial cardiac vagotomy or total cardiac vagotomy. 6. The apparent power output of the heart was reduced during hypoxia at high acclimation temperatures due to the marked bradycardia.