Spelaeogriphus lepidops, Gordon, 1957

Wirkner, Christian S. & Richter, Stefan, 2007, The circulatory system and its spatial relations to other major organ systems in Spelaeogriphacea and Mictacea (Malacostraca, Crustacea) - a three-dimensional analysis, Zoological Journal of the Linnean Society 149 (4), pp. 629-642 : 632-634

SPELAEOGRIPHUS LEPIDOPS

DIGESTIVE SYSTEM ( Figs 1A, F and 2A–C, G): A stout oesophagus is followed by a voluminous stomach chamber filling most of the cephalothorax ( Fig. 2B). The cardio-oesophageal valve is formed by two lateral valves (valvulae laterales oesophagi; nomenclature after Kobusch, 1999) and a dorsal valve (valvula dorsalis oesophagi). In the stomach chamber, a filter apparatus is found that is made up of a relatively flat midventral invagination (inferomedianum anterius), flanked by shallow primary filtering grooves. In the anterior part of the stomach, two pairs of lateralia (lateralia anteriores and posteriores) form the dorsal part of the filter apparatus. The stomach dorsal piece (superomedianum, sm) protrudes in a posterior direction from the anterior-dorsal roof of the stomach. Proximally it is convex in shape and then becomes more and more cylindrical with the tip pointing slightly dorsally. The pyloric region forms a large sac at the postero-ventral end of the stomach (py; Fig. 2A). Inside the pyloric sac large paired lateral invaginations (inferolateralia posteriores) and a high but narrow midventral invagination (inferomedianum posterius; imp) form deep secondary filter grooves ( Fig. 2C). Subsequent to the pyloric region, a small antechamber (ar) for the midgut glands (mgg) is situated ( Figs 1F and 2B, G). Here, two pairs of midgut glands emanate in a posterior direction and, in addition, one very small pair in an anterior direction. The posterior midgut glands are much smaller in diameter in relation to the midgut, and run to the rear thoracic segments (mgg; Fig. 1A ).

CENTRAL NERVOUS SYSTEM ( Fig. 1D, E ): The anterior medial cells (am) are split deeply. Ventrolaterally of these two cell clusters the lateral protocerebrum emanates on each side running into the eye stalks. This part of the lateral protocerebrum most probably represents the medulla terminalis. There are no optic neuropils visible. Hemielipsoid bodies could also not be found. A more detailed analysis of the lateral protocerebrum was not possible, as shrinkage of the nervous tissue in the eye stalks occurred in all specimens studied ( Fig. 2B, C). In the median protocerebrum, a central body and a protocerebral bridge are easily discernible. Laterally in the deutocerebrum, small olfactory lobes with distinct antennal glomeruli are present (alg; Fig. 2C). An olfactory globular tract could not be observed. A clear distinction between the tritocerebrum and the oesophageal connective is not possible as the strong antenna II nerves (an2) lead off rather ventrally, where the brain is already split into a right and a left strand ( Fig. 1D ).

CIRCULATORY SYSTEM ( Figs 1A–C, F and 2D–G): The central circulatory organ is the tubular heart. With a diameter of about 120 µm, it runs between the midgut and the dorsal cuticle from the posterior part of the cephalothorax to the 8th thoracic segment ( Fig. 2A). It is formed by a weak myocardium that features spirally arranged muscle fibres that lie far away from each other ( Fig. 2A, G). Two pairs of incurrent ostia occur at the border of the 5th−6th and the 7th−8th thoracic segments ( Fig. 2F). Neither lateral cardiac arteries nor a posterior aorta emanate from the heart. A pericardial sinus is constricted by the dorsal diaphragm, which stretches through the whole trunk (dd; Fig. 2D, G). Podo-pericardial sinuses run from the legs to the pericardium laterally in each thoracic segment (pp; Fig. 2E).

The transition of the heart to the anterior aorta is situated in the posterior part of the cephalothorax, directly above the invagination of the stomach dorsal piece (arrow; Fig. 1F ). Two vertical arranged flaps form a valve at this transition ( Fig. 2D). Here, the dorsal vessel has no contact to the dorsal stomach wall. The anterior aorta runs anteriorly, and bends around the anterior stomach wall widening to form a dilation. Laterally, at the bend, two vessels branch off that open at the lateral stomach wall (la; Fig. 1A–C, F ). Slightly anteriorly, a median vessel branches off the aorta making its way through the two anterior medial cell clusters. It is rather strong (diameter ∼45 µm) and bends ventrally around the brain ( Fig. 1F ). Two pairs of arteries emanate from it: the first, at the anteriormost part of the pericerebral vessel, runs along the lateral protocerebrum into the eye stalks (oa); the second, further ventrally, runs into the first antennae (a1). The aorta dilation converges and lies between the posterior side of the brain and the anterior oesophagus wall ( Figs 1C, F and 2A). The two oesophageal dilator muscle pairs m104 and m103 (nomenclature after Scheloske, 1976) are inserted at the anterior oesophageal wall and run through the aorta dilation. This complex is therefore called ‘myoarterial formation a’ (see the Discussion). Arteries branch off the dilation laterally through a channel between the median protocerebrum and the olfactory lobes. They unite with branches of the dilation and then run together with the antenna II nerves into these appendages. The dilation opens ventrally into the labral haemocoel.

Figures

Figure 1. Reconstructions of the major organ systems in Spelaeogriphus lepidops. A, Schematic diagram of the haemolymph vascular system (HVS) and digestive system. Arteries running into the antennae are depicted by broken lines. B, C, three-dimensional reconstructions (surface rendering) of a horizontal semithin section series showing the HVS in the cephalothorax. B, antero-lateral aspect. C, Lateral aspect. D, E, three-dimensional reconstructions (surface rendering) of a horizontal semithin section series showing the central nervous system (CNS) in the cephalothorax. D, dorsal aspect. E, frontal aspect. F, three-dimensional reconstructions (surface rendering) of a horizontal semithin section series showing the major organ systems in the cephalothorax. Green, digestive system; red, HVS; yellow, CNS. The CNS is shown as slightly transparent. See the Appendix for a list of abbreviations used.