Loligo vulgaris

Wild, Elvira, Wollesen, Tim, Haszprunar, Gerhard & Heß, Martin, 2015, Comparative 3 D microanatomy and histology of the eyes and central nervous systems in coleoid cephalopod hatchlings, Organisms Diversity & Evolution (New York, N. Y.) 15 (1), pp. 37-64 : 50-53

publication ID	https://doi.org/ 10.1007/s13127-014-0184-4
persistent identifier	https://treatment.plazi.org/id/B94787AC-FFF4-D252-FF2B-1970C4D3F969
treatment provided by	Felipe
scientific name	Loligo vulgaris
status

Treatment

Loligo vulgaris View in CoL

The hatchlings of L. vulgaris are the smallest of the five decabrachian species investigated in this study ( Fig. 15 View Fig , supplement interactive Fig. 5 View Fig ; horizontal head diameter ca. 1.1 mm; see also Fig. 2e) with a cephalopodium tapering from the CNS region over the eyes to the short brachial crown ( Fig. 15a View Fig ). The first arm pair is just visible; consequently, the brachial nerves and ganglia of the ventral arm pairs are better developed than the dorsal ones. Also, the relative length of the tentacles is comparatively short in this species. Like in S. officinalis , the fixation quality is superior, but some signs of tissue shrinkage are detectable in the cornea and eye chamber region. The eyes (horizontal diameter 615 μm) fill the anterior head to a comparatively high percentage ( Fig. 15d View Fig ), with anterior chambers being quite narrow. The anterior chamber organ is torus-shaped (but with triangular profile) filling the angle between the eyes and optic lobes ( Fig. 3e View Fig ), additionally extending ventrolaterally far back along the optic lobes outer surface. Ventrally, it has a hole for the inferior ophthalmic nerves; dorsally, a constriction makes way for eye muscles. The eyes point slightly forward (Fig. 2e) in a horizontal plane ( Fig. 15d View Fig ). The compound lens (diameter 180 μm, distal segment 15 %) is embedded in a comparatively narrow vitreous body. In the L. vulgaris hatchling, the retina is well developed with a high photoreceptor density (thick layer of photoreceptor nuclei and remarkably developed plexus) and an exceptionally dark pigment layer (also between the distal segments; Fig. 4e View Fig ) and along the inner sides of the ciliary body and iris ( Fig. 3e View Fig ). The retina is rather thick (especially when compared to the eye diameter; Fig. 3e View Fig ), hemispherically shaped in the frontal half, and forming a flattened ramp in the temporal half. As in S. officinalis and R. macrosoma (but contrary to S. obscura and I. notoides ), the optic lobes are separated by the brachial lobe and inferior frontal lobes frontally. Frontolaterally, they are flattened by the eye cups only sligtly. In L. vulgaris , a thin second (inner) plexiform layer is visible just proximal to the inner granular layer ( Fig. 5f View Fig ). The ventral optic commissure runs directly across the esophagus. The dorsal part of the optic commissure follows and is in direct contact with the peduncle commissure.

The brachio-pedal and brachio-palliovisceral connectives, as well as the oculomotoric nerves, are slightly pushed togeth- er between the frontal margins of the optic lobes ( Fig. 10e View Fig ). At the level of arm pair 3 on both sides, a nerve, running backward to the pedal lobes, escorts the superior antorbital nerves ( Fig. 7e View Fig ; to the right of “bl”). As soon as possible, the anterior inferior oculomotor nerves diverge from the brachio-pedal connectives, running alongside the inner surface of the optic lobes ( Fig. 9e View Fig ; noai) and bifurcate into and ventral and dorsal branch ( Fig. 7e View Fig ; 9 View Fig ).

We have not discriminated between prebrachial and brachial lobes in the anterior subesophageal mass as Young (1976b) did; the same is true for the pedal lobe. The commissure between the subradular ganglia ( Young 1965a, 1971) was detectable only in outlines. The palliovisceral mass consists among others of prominent dorsolateral lobes (fin- and chromatophore lobes), and the crossing of the first-order giant fibers can be seen ( Fig. 15h View Fig , arrowhead).

The inferior frontal lobes are proportionally bigger compared with the superior buccal lobes and as in R. macrosoma positioned frontally to the latter. As in S. officinalis , the buccal and frontal lobes of L. vulgaris lie close to each other, so that the cerebrobuccal connectives are quite short ( Fig. 8e View Fig ). Since the buccal and frontal lobes are also very close to the brachial lobe, the bucco-brachial and cerebrobrachial connectives are short as well and appear fused at their entrance to the brachial lobe. The anterior basal lobes are divided into an anterior (ventral) and posterior (dorsal) part by a thin layer of cells ( Fig. 15e View Fig ; abl).

As in other decabrachian species investigated in this study, the profiles of the big statocysts (diameter 425 μm) appear slightly irregular due to some tissue shrinkage ( Fig. 15h View Fig ); statoliths are found in their frontal portion ( Fig. 15g View Fig ). The olfactory organs (275× 165×40 μm 3) are located on both sides ventrally to the optic lobes, i.e., well behind the eyes ( Fig. 15f View Fig ).