Hyalogyrina glabra Marshall, 1988
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publication ID |
https://doi.org/ 10.1007/s13127-011-0048-0 |
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persistent identifier |
https://treatment.plazi.org/id/03DC2538-0372-BF08-FF7A-3A60B5C13F95 |
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treatment provided by |
Felipe |
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scientific name |
Hyalogyrina glabra Marshall, 1988 |
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Hyalogyrina glabra Marshall, 1988 View in CoL
( Figures 18, 19 View Fig and 20 View Fig )
External morphology and pedal structures
Again the snout is tapered and the mouth opening is quite small. The smooth cephalic tentacles are quite long, but a copulatory organ is not present. A long, densely ciliated pallial tentacle emerges from the right anterior mantle edge.
There is a single pedal gland, which opens via a wide pore at the anterior border of the foot. Again a densely packed aggregation of large (diameter 80 μm) and transparent calcium cells is found in the center of the foot. The foot sole is densely ciliated.
Shell muscle, haemocoel, and mantle cavity
Concerning the columellar muscle and the histology of the haemocoel the conditions in H. glabra appear similar to the preceding species, but histological analysis has been limited due to poor preservation.
The mantle roof ( Fig. 18d) is equipped with a dense net of blood sinuses throughout its area. At the very left of the mantle cavity a small osphradium with an underlying ganglion is present ( Fig. 20 View Fig ). It is followed to the right by a (left) pallial gland (not shown in Fig. 18) with many, small mucous cells, and more posteriorly by the kidney and the heart. The central mantle cavity is occupied by the gill, and posterior of the latter by the rectal loops with the anal opening on the anterior right side. The genital apparatus with gonoduct and receptaculum fills the right corner of the mantle cavity, the most anterior portion is covered by a pallial gland on the right ( Fig. 18: pg).
The gill is again a bipectinate structure without skeleton or bursicles, but is fixed to the pallial roof only at its left side, otherwise it reaches freely into the cavity.
Excretory organ, heart and circulatory system
Conditions of excretory organ (single, left, pallial), heart (monotocardian), and circulatory system (with median head aorta) are nearly identical to those described for the other species investigated. We could not detect a nephridial gland, but this might be due to insufficient preservation.
Genital system ( Fig. 19 View Fig )
The hermaphroditic gonad fills the most posterior part of the body, is a compact organ and shows spermiogenesis in its outer, oogenesis in its inner portions ( Fig. 19d View Fig ). The gonad reaches forwards up to the line of the posterior end of the mantle cavity and is continued by a hermaphroditic duct and the glandular part of the gonoduct, where the lumen is branched into a vas deferens and an oviduct, although both ducts continue forwards in parallel and intimately associated ( Fig. 19c View Fig ). Whereas the vas deferens is a thin, ciliated tube, the oviduct is a thick, glandular structure with a lumen that appears slit-like in cross-sections. Again there are various mucous cell types resulting three distinct portions of the oviduct, and at midlength of the latter there is a small pouch (bs1). Vas deferens and oviduct each have their own openings into the right mantle cavity.
Close to the two genital openings there are two further openings. Laterally at left there is the opening of the separated, tube-like receptaculum seminis, which is surrounded by a muscular layer and has a densely ciliated epithelium ( Fig. 19b View Fig ). It includes up to two spermatophores, with densely packed sperm in one specimen ( Fig. 19e View Fig ). Distally the second opening forms a small cavity (‘genital atrium’) around male and female openings. From there a long, thin flagellum reaches backwards.
right/left radular musculature, rs = radular sheath, st = stomach. Supplementary plate 4 offers an interactive 3D model of Hyalogyrina glabra that can be accessed by clicking into Fig. 18 (Adobe Reader version 7 or higher required). Rotate model: drag with left mouse button pressed; shift model: same action+ctrl; zoom: use mouse wheel (or change default action for left mouse button). Select or deselect (or change transparency of) components in the model tree, switch between prefab views, or change surface visualization (e.g. lighting, render mode, crop, etc.)
Unfortunately, the flagellum in the specimen investigated ends at a break, thus could not be analyzed fully.
Alimentary tract ( Fig. 18d–f)
The whole buccal apparatus is structured nearly identically to those of the preceding species. Again we recognized a specific paired retractor muscle from the anterior lateral buccal wall to the posterior wall of the ovotestis; (e) proximal receptaculum seminis with spermatophore. Labels: ci = cilia, e = eggs, ex = external milieu, fl = flagellum, g = gonad, ovotestis, ga = genital atrium, gd = gonoduct, hd = hermaphroditic duct, mc = mantle cavity, rs = receptaculum seminis, sp = autosperm, vd = vas deferens head, with an enclosed nerve which contacts the buccal ganglion.
Also the conditions of the oesophagus and stomach strongly resemble those in the other species. We recognized a single tooth of the gastric shield, and the two digestive glands have a common opening into the stomach. The very short intestine starts at the anterior wall of the stomach. The rectum passes beneath the heart, runs forwards to the left, then makes an anterior and a posterior loop in the pallial roof, and finally reaches the anal opening in the anterior right mantle cavity.
Nervous system and sensory organs ( Fig. 20 View Fig )
The epiathroid and streptoneurous nervous system is nearly identical to those in the species described above. Due to insufficient preservation we could not clarify the condition of the posterior visceral loop.
Sensory structures resemble Hyalogyrina grasslei in that the cephalic tentacles are supplied by a bifid nerve and eyes are entirely lacking. Again the small statocysts contain single statoliths.
Available data from other sources
Marshall (1988) described the shell as small (max. 1.7 mm), turbinate, transparent, and sculptured (op.cit.: figs. 7F–H, J). The hyperstrophic protoconch has 1.25 whorls (fig. 7I). The radula is rhipidoglossate with the formula n 1 1 1 n, (figs. 16A–D), “the single pair of positionally laterals would seem to be marginals, the original laterals … have presumably been lost” (op.cit.: p. 1000). Marshall also provided a drawing of the head (op. cit.: fig. 9G), which carries a long snout, no eyes, but a filiform ‘copulatory organ’ (according to our results the pallial tentacle) behind the basis of the right cephalic cerebropedal connective, 4’ = left pleuropedal connective, 5 = pedal commissure, 6/6’ = right/left anterior pedal nerve, 7/7’ = right/left ventral pedal nerve, 9 = buccal commissure (not fully reconstructed), 10 = supraoesophageal connective, 11 = supraoesophageal-osphradial connective, 13 = suboesophageal connective tentacle. The foot shows two anterior lappets; epipodial tentacles again are lacking.
Hedegaard (1990: pl. 52, fig. 3) figured a shell break demonstrating the shell’ s purely aragonite structure. Finally Warén and Bouchet (1993: fig. 42D) have provided SEM images of the protoconch that clearly show the hyperstrophic condition.
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