The structure of the conus arteriosus of the sturgeon (<i>Acipenser naccarii</i>) heart: II. The myocardium, the subepicardium, and the conus‐aorta transition

2006

Anat. Rec.

The heart outflow tract (OFT) of primitive fish is formed by two portions: a proximal conus arteriosus and a distal bulbus arteriosus. The OFT of modern teleosts is considered to be formed by a single component, the bulbus, the conus having been lost through evolution. This article challenges the concept of the disappearance of the conus arteriosus in the teleost heart. A total of 28 teleost species belonging to 19 families and 10 orders were analyzed. The hearts were divided into two large groups: those having entirely trabeculated ventricles, and those possessing a compacta. In the hearts having entirely trabeculated ventricles, the conus arteriosus appears as a distinct segment interposed between the ventricle and the bulbus arteriosus, being formed by compact vascularized myocardium. However, the conus of several species lacks vessels. In these cases, the conus presents large intercellular spaces bounded by collagen. In the hearts possessing a ventricular compacta, the conus either appears as a muscular ring of variable length connecting the ventricle and the bulbus or forms a crown or ring of myocardium apposed to the ventricular base. In all the teleosts studied, the conus can be recognized as an anatomic entity different from the ventricle. Furthermore, the conus appears as a distinct heart segment in the developing fish. Therefore, the conus arteriosus has not been lost in evolution and constitutes a fundamental part of the teleost OFT. In all the species studied, the conus supports the OFT valves, which should properly be named conus valves. Anat Rec Part A, 288A:900 -908, 2006.

Section: Oft In Primitive Fishmentioning

confidence: 54%

Section: Oft In Primitive Fishmentioning

confidence: 95%

Section: Oft In Primitive Fishmentioning

confidence: 99%

See 1 more Smart Citation

Conus arteriosus of the teleost heart: Dismissed, but not missed

2006

Anat. Rec.

“…At this point, it should be noted that, at stages 4-5 dph, the outflow tract is completed by the formation of a new segment, the intermediate (conus-aorta transition) segment (Icardo et al, 2002) or bulbus arteriosus (Guerrero et al, 2004), which is added to the cranial end of the heart, between the conus arteriosus and the ventral aorta. We could not find evidence for the progression of the epicardium into this segment (Fig.…”

Section: Resultsmentioning

confidence: 99%

The Development of the Epicardium in the Sturgeon Acipenser naccarii

Guerrero

Durán

et al. 2009

The Anatomical Record

Self Cite

This article reports on the development of the epicardium in alevins of the sturgeon Acipenser naccarii, aged 4-25 days post-hatching (dph). Epicardial development starts at 4 dph with formation of the proepicardium (PE) that arises as a bilateral structure at the boundary between the sinus venosus and the duct of Cuvier. The PE later becomes a midline organ arising from the wall of the sinus venosus and ending at the junction between the liver, the sinus venosus and the transverse septum. This relative displacement appears related to venous reorganization at the caudal pole of the heart. The mode and time of epicardium formation is different in the various heart chambers. The conus epicardium develops through migration of a cohesive epithelium from the PE villi, and is completed through bleb-like aggregates detached from the PE. The ventricular epicardium develops a little later, and mostly through bleb-like aggregates. The bulbus epicardium appears to derive from the mesothelium located at the junction between the outflow tract and the pericardial cavity. Strikingly, formation of the epicardium of the atrium and the sinus venosus is a very late event occurring after the third month of development. Associated to the PE, a sino-ventricular ligament develops as a permanent connection. This ligament contains venous vessels that communicate the subepicardial coronary plexus and the sinus venosus, and carries part of the heart innervation. The development of the sturgeon epicardium shares many features with that of other vertebrate groups. This speaks in favour of conservative mechanisms across the evolutionary scale. Anat Rec, 292:1593Rec, 292: -1601Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.

“…In addition, a distinct intima-like layer is located between the inner elastica and the smooth muscle cells. These structural differences between the two aortic portions indicate that the intrapericardial segment constitutes a transitional segment, the embryonic origin of which might differ from that of the extrapericardial ventral aorta (Icardo et al, 2002b).…”

mentioning

confidence: 97%

Differentiation of the cardiac outflow tract components in alevins of the sturgeon Acipenser naccarii (Osteichthyes, Acipenseriformes): Implications for heart evolution

Guerrero

Durán

et al. 2004

Journal of Morphology

Self Cite

Previous work showed that in the adult sturgeon an intrapericardial, nonmyocardial segment is interposed between the conus arteriosus of the heart and the ventral aorta. The present report illustrates the ontogeny of this intermediate segment in Acipenser naccarii. The sample studied consisted of 178 alevins between 1 and 24 days posthatching. They were examined using light and electron microscopy. Our observations indicate that the entire cardiac outflow tract displays a myocardial character during early development. Between the fourth and sixth days posthatching, the distal portion of the cardiac outflow tract undergoes a phenotypical transition, from a myocardial to a smooth muscle-like phenotype. The length of this region with regard to the whole outflow tract increases only moderately during subsequent developmental stages, becoming more and more cellularized. The cells soon organize into a pattern that resembles that of the arterial wall. Elastin appears at this site by the seventh day posthatching. Therefore, two distinct components, proximal and distal, can be recognized from the fourth day posthatching in the cardiac outflow tract of A. naccarii. The proximal component is the conus arteriosus, characterized by its myocardial nature and the presence of endocardial cushions. The distal component transforms into the intrapericardial, nonmyocardial segment mentioned above, which is unequivocally of cardiac origin. We propose to designate this segment the "bulbus arteriosus" because it is morphogenetically equivalent to the bulbus arteriosus of teleosts. The present findings, together with data from the literature, point to the possibility that cells from the cardiac neural crest are involved in the phenotypical transition that takes place at the distal portion of the cardiac outflow tract, resulting in the appearance of the bulbus arteriosus. Moreover, they suggest that the cardiac outflow tract came to be formed by a bulbus arteriosus and a conus arteriosus from an early period of the vertebrate evolutionary story. Finally, we hypothesize that the embryonic truncus of birds and mammals is homologous to the bulbus arteriosus of fish.