Rossia macrosoma, Delle Chiaje, 1829

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 : 42-44

publication ID	https://doi.org/ 10.1007/s13127-014-0184-4
persistent identifier	https://treatment.plazi.org/id/B94787AC-FFFC-D245-FC93-19FFC266F96E
treatment provided by	Felipe
scientific name	Rossia macrosoma
status

Treatment

Rossia macrosoma View in CoL

The hatchling of R. macrosoma ( Fig. 12 View Fig , supplement interactive Fig. 2) is the second largest (horizontal head diameter ca. 3.1 mm) of the six species investigated in this study, has a comparatively thick epidermis, and appears dorsoventrally compressed in the eye region ( Fig. 12c, d View Fig ). The arms were not completely enclosed in the section series, but the peripheral (arm and tentacle) nervous system reveals the standard organization (Fig. 2b).

The eyes are centered virtually in the horizontal midline of the head ( Fig. 12a View Fig , horizontal diameter 1150 μm) and point slightly forward (Fig. 2b) and upward ( Fig. 12d View Fig ). Conspicuous bulges border the cornea. In the given specimen, the eyes and retinae are not deformed and suspended in the center of voluminous anterior chambers (like in S. officinalis ). Anterior chamber organs are well developed in this stage ( Fig. 12d–g View Fig , Fig. 3b View Fig , and Fig. 5b View Fig ). The retinae are ellipsoidal cups (horizontal diameter ca. 1,025 μm, vertical diameter ca. 715 μm) with regular curvature and thickness, and the photoreceptors possess noticeably short distal segments. A voluminous vitreous body causes a quite large distance between lens and retina ( Fig. 3b View Fig ). The lens (diameter 425 μm, distal segment ca. 21 %) is characterized by a thick capsule (of artificially? detached lens plates, see, e.g., Willekens et al. 1984), constituting about 85 % of the total lens volume. Due to a preparation artifact, the lens is broken at the septum, accentuating the connections of the ciliary body to both the distal and proximal segment of the lens ( Fig. 3b View Fig ).

As in Sepia , the brachial lobes, esophagus, and inner yolk sac, but not the buccal and frontal lobes, are located between the frontal portions of the optic lobes. The very thin ventral part of the optic commissure runs directly across the hardly visible esophagus under which a profile of the inner yolk sac is visible ( Fig. 6b View Fig ). The peduncle commissure is only discernible at its entrance in the right peduncle lobe.

The brachiopedal connectives are elongate (twofold compared to S. officinalis ) because of the greater distance between the brachial and pedal lobes ( Fig. 10b View Fig ).

In the supraesophageal mass, the inferior buccal lobes lie frontally to the superior buccal lobes as in Loligo . The superior buccal lobes and the inferior frontal lobes are spaced ca. 500 μm by long buccobrachial and cerebrobrachial connectives (Fig. 2b and Fig. 9b View Fig ); cerebrobuccal connectives are visible in outlines but could not be tracked. Also, the distance between buccal and brachial lobes is quite big. The dorsal basal lobes appear rather narrow in this species (Fig. 2b).

The statocysts are well preserved in the given specimen and comparatively small sized with respect to the total head volume (vertical diameter in transversal sections 590 μm). Olfactory organs are visible as flat “anlagen,” ventrolateral to the rear portion of the anterior chamber organ.