Comparative anatomy of the extraocular muscles in four Myliobatoidei rays (Batoidea, Myliobatiformes)

Tendinous annulus of Zinn for a common origin of the extraocular rectus muscles: a histological study of the orbital apex from donated elderly cadavers

The medial, inferior, lateral, and superior rectus muscles (MR, IR, LR, SR), levator palpebrae superioris (LPS), and superior oblique muscle (SO) seem to originate from the tendinous annulus of Zinn, ring-like fibrous tissue crossing the bony orbital fissure. We observed the histological annulus structure using semi-serial histological sections of the orbital apex from 30 elderly donated cadavers. Nearly frontal sections demonstrated a ring-like fibrous structure (a candidate annulus) connecting or embedding four rectus muscles. The candidate annulus did not contain the LPS and SO, and, in the anterior side, the latter muscles originated from the optic canal opening. Far posterior to the annulus, there was a common tendon of the MR, IR, and LR attached to the infero-medial wall of the bony orbital fissure. At the superior part, the annulus is tightly attached to the optic nerve sheath and the periosteum. Sagittal (or Horizontal) sections clearly exhibited parts of the annulus at the MR (SR) origin. Both sagittal and horizontal sections displayed (1) the common origin of the three rectus muscles near the oculomotor nerve in the bony fissure and (2) an accessory, independent muscle bundle of the MR originating from the superomedial margin of the optic canal near the origins of the LPS or SO. Consequently, the so-called tendinous annulus appeared not to provide origins of all six muscles.

The fine structure of the turbot eye (Scophtalmus maximus): A macro-anatomical, light and scanning electron microscopical study

In fish species, the morphological structure of the eye varies depending on environmental conditions. Morphometric data about the sensory organs of fish is lacking. Therefore, this study aims to describe the morphological structure of the turbot eye using gross, light and scanning electron microscope examinations. The turbot eyeball was found to comprise three layers: the tunica fibrosa bulbi (cornea, sclera), the tunica vasculosa bulbi (choroidea, iris) and the tunica nervea bulbi (retina). The thickness of the centre of the cornea measured approximately 153.14 μm, and the peripheral thickness measured 410.81 μm. The sclera consisted of a two-part cartilage structure that was connected with elastic fibres. The choroideal rete was found in the tunica vasculosa bulbi, and its thickness measured 1.6 ± 0.1 mm. Moreover, no pigment was found in the choroidea. The lens was determined to be a very hard and transparent structure extending towards the cornea. In addition, we detected five ligaments in the equatorial plane of the eye, in which the tendon of the retractor lentis muscle attaches to the lens. Also, there were six extraocular muscles in the turbot. This study is the first to present detailed descriptions of morphological structures and morphometric data for all the layers of the turbot eye. Since the anatomical structure of the eye in fish is variable, it is thought that the data on the turbot eye will contribute to the anatomy literature.

Morphological description of ovary and uterus of the nurse shark (Ginglymostoma cirratum) caught off at the Fortaleza coast, Northeast Brazil

ABSTRACT: The nurse shark, Ginglymostoma cirratum (Bonnaterre, 1778) is one of the most studied species of elasmobranchs. However, the knowledge of their reproductive biology is still relatively rare, particularly in the western South Atlantic. This study aimed to describe the morphology of the uterus and the ovary of G. cirratum, based on specimens caught off at the Fortaleza/CE coast, northeast Brazil. Samples were collected from September 2012 to June 2013, from regular landings of artisanal fishing, which commercialize this species freely. A total of ten females were collected. The methodologies followed for analyzing the ovaries and uterus of those females included both macroscopic and histological analysis. G. cirratum has internal type ovary morphology, with invaginations of connective tissue, which defines compartments and separate oocyte groups in ovigerous lots. The epithelium lining the ovary changes from simple columnar ciliated in the area without ovigerous lots, which turns into a simple cubic epithelium in the coating portion of the epigonal organ where ovarian tissue is absent. The uterine mucosa has secretory cells denoted by Alcian Blue staining, indicating the production of mucopolysaccharides, even in immature individuals. This lecithotrophic shark has a uterine vascularized mucosa that is one characteristic of viviparous elasmobranch species.