On four monostiliferous hoplonemerteans, including three new genera and species from Washington state and British Columbia Author Iwata, Fumio text Journal of Natural History 2006 2006-08-22 40 15 - 16 873 913 http://dx.doi.org/10.1080/00222930600833800 journal article 7447 10.1080/00222930600833800 3a090e10-1fd7-48bc-8aa7-54dfe7a309c8 1464-5262 4669044 Sanjuannemertes aeilloaesi gen., sp. nov. Type specimen Holotype : USNM 1072181 ; 22 slides of stained serial section, including transverse sections of the anterior portion of the body (9) and tail (5) and horizontal sections of the midgut (8). Type locality San Juan Channel, Washington , USA (48 ° 34.3 9 N, 123 ° 1.7 9 W), depth 62 fathoms, October 21, 1964 . Description External features The body was small and cylindrical, 15 mm long and 1.5 mm wide ( Figure 1.4 ). When contracted, it was 10 mm long and 2 mm wide. The anterior edge of the head was rounded ( Figure 17a, c ) or slightly indented ( Figure 17b ). The posterior end of the body had a papilla-like protrusion ( Figure 17e ). There were two oblique cephalic grooves on both the dorsal and the ventral sides of the head ( Figure 17 a–d). On the ventral side, the mouth and proboscis pore are in a slit-like depression that crosses the anterior cephalic groove ( Figure 17b ). The color of the body was orange or light vermilion. On both the dorsal and the ventral surfaces of the anterior portion of the body there were numerous narrow, pale orange or whitish transverse lines. The whitish proboscis apparatus could be seen through the body wall; the basis of the central stylet was evident as a milky white patch. The four ocelli, visible on the dorsal side, were arranged in the form of a trapezoid. The two anterior ocelli were closer than those of the posterior pair and were situated just in front of the anterior cephalic groove, whereas the other pair was situated underneath the posterior one ( Figure 17a, c, d ). Body aeall, musculature and parenchyma The body in transverse section is circular in both the cephalic and midgut regions ( Figure 18a ). The epidermis is of uniform thickness (about 60 mm ). Large unicellular glands are distributed over the entire body and are especially well developed in the midgut region. Cyanophilic glands are not present between them. In the cephalic region, the epidermis and longitudinal muscle layer of the body wall are nearly the same in thickness, and glandular cells are confined to the upper portion. The dermis, 5–10 mm thick, onefourth to one-tenth the thickness of the epidermis ( Figure 18b ). The body wall musculature consists of a thin outer circular layer ( 10 mm thick) and an inner longitudinal layer ( 60 mm thick). There is sparse lattice-type diagonal muscle layer between them. The longitudinal layer is not divided into inner and outer portions anteriorly. There are no head retractor muscles related to the longitudinal muscle layer. Dorsoventral and radial muscle fibres, as well as parenchyma, are absent. Rhynchodeum, rhynchocoel and proboscis The proboscis pore, 60 mm long and 110 mm wide, is a mid-ventral furrow. With the mouth it forms a common atrium ( Figures 17b , 18c and 19d ). Its wall is 15 mm thick and lacks cilia and glands. The rhynchodeum is circular in transverse section owing to the proboscis protruded into it and is covered by a thick layer ( 20–60 mm ) of circular muscles ( Figure 18d ). The rhynchodeum measures 260 mm long and is at first cylindrical, but then broadens to a width of 300–450 mm ( Figure 18 d–h). At the posterior end of the rhynchodeum, where its circular muscle sphincter disappears, the pre-cerebral septum is formed by radial longitudinal muscles derived from the longitudinal muscle layer in the dorsal side of the body; the proboscis insertion also becomes evident ( Figure 18g ). The lateral and ventral sides of the body contain no radial longitudinal muscles in the precerebral septum ( Figure 18h ). Figure 17. Sanjuannemertes aeilloaesi , new genus and new species , holotype. (a) Anterior portion, dorsal view; (b) anterior portion, ventral view; (c) anterior portion, dorsal view; (d) anterior portion, lateral view; (e) posterior end. Abbreviations: ap, anterior cephalic groove; ao, anterior ocellus; pg, posterior cephalic groove; pd, pore of mouth and proboscis opening; po, posterior ocellus. The proboscis diaphragm has a central stylet and a vase-shaped basis 400 mm long, 70 mm wide at its top and 60 mm wide at its middle portion ( Figure 19a, b ). In sections, the basis shows a strong affinity for eosin and its content is not extruded. The central stylet measures 40 mm long ( Figure 19a ). The basis of the central stylet rests on a small bolster, is surrounded by a thick layer of circular muscles ( Figure 19b ) and, in sections, shows no posteriorly inserted accessory stylet. The stylet bulb consists of a thick wall of circular muscles, 300 mm wide. There are two accessory stylet pouches, each containing two stylets ( Figure 19c ). The proboscis has 10 nerves. Figure 18. Sanjuannemertes aeilloaesi , new genus and species , holotype. (a) Transverse sections between 19 and 104 from anterior end of body, showing body circular in transverse section; (b) stomach region; (c) proboscis pore and mouth separated; (d) circular muscle layer of rhynchodeum and proboscis; (e) end of the mouth and stomach wall (oesophagus lacking); (f) stomach; (g) radial longitudinal muscles from body wall longitudinal muscle layer in the dorsal side of the head; (h) proboscis insertion in the lateral side of the head. Scale 100 mm (b–h) and 200 mm (a). Abbreviations: ad, anterior cephalic groove formed by dorsal and ventral grooves united at mid-lateral portion of head; ag, anterior ventral cephalic groove; bc, body wall circular muscle layer; bl, body wall longitudinal muscle layer; br, brain; cb, cephalic blood vessel; cn, cerebral organ canal; cr, circular muscle layer of rhynchodeum; cs, cerebral sensory organ; cv, cephalic nerves; dg, dorsal ganglion; dr, dermis; mo, mouth; oc, ocellus; pn, proboscis nerve; pr, proboscis; ps, proboscis sheath; rc, rhynchocoel; rd, rhynchodeum; rl, radial longitudinal muscles from body wall longitudinal muscle layer; st, stomach; vg, ventral ganglion; wt, wall of stomach. Figure 19. Sanjuannemertes aeilloaesi , new genus and species , holotype. (a) Longitudinal sections between 57 and 63 in proboscis diaphragum and transverse sections between 16 and 209 from anterior end of body, showing central stylet and anterior portion of basis; (b) posterior portion of basis and its bolster; (c) accessory stylet pouch; (d) proboscis pore, mouth and lips of mouth; (e) posterior portion of mouth and transitional part of stomach without showing oesophagus; (f) transitional area of stomach into pylorus and anterior diverticula of intestinal caecum; (g) deep lateral diverticula of intestine; (h) anastomose of cephalic blood vessels. Scale 50 mm (a), 100 mm (b–f, h) and 200 mm (g). Abbreviations: ac, anastomose of cephalic blood vessel; ag, anterior ventral cephalic groove; ai, anterior diverticula of intestinal caecum; as, accessory stylet; bs, bolster; ce, central stylet; cp, circular muscle layer of proboscis sheath; ct, central stylet basis; db, dorsal blood vessel; in, intestine; la, lateral diverticula of intestine; ls, longitudinal muscle layer of proboscis sheath; mo, mouth; oc, ocellus; pa, pouch of accessory stylet; pn, proboscis nerve; pr, proboscis; ps, proboscis sheath; py, pylorus; rc, rhynchocoel; wt, wall of stomach. Alimentary canal The alimentary canal has four major divisions; stomach, pylorus, midgut (with anteriorly directed caecum and lateral diverticula) and hind gut. The mouth and the proboscis pore open into a common atrium on the ventral side of the head; they are not joined together ( Figures 17b , 18c, e and 19d, e ). There is no oesophagus; the mouth leads directly to the stomach ( 500 mm long). The stomach has a deep lengthwise fold for its entire length and is far longer ( 160 mm ) than the brain ( Figure 18e, f ). The stomach has no diverticulum. The pylorus is long, measuring one and one-sixth times the length of the stomach. The intestinal caecum has a pair of short anterior pouches 40 mm long ( Figure 19f ) and three pairs of lateral diverticula, beginning immediately behind the posterior end of the brain. The intestinal canal has long lateral diverticula ( Figure 19g ). The hindgut is 100 mm long and ends at the anus. Blood υascular system The blood vascular system has three longitudinal vessels. The two cephalic vessels lateral to the rhynchodeum anastomose above the rhynchodeum near the tip of head to form a simple vascular loop 200 mm wide, 10 mm high and 20 mm long. The vascular loop is not a continuous space ( Figure 19h ). Farther posteriorly, the cephalic vessels do not form large lacunae and do not give off cerebral vessels. They are slender, at first running alongside the rhynchocoel or near the dorsolateral side of the cerebral organ canal, and then above the cerebral organs, but do not enter the brain ring ( Figures 18d, h and 20 b–d, f, h). Near the posterior end of the cerebral organ, the cephalic vessels extend down between the brain lobes and the rhynchocoel, and fuse into a dorsal vessel; this does not form a median vascular plug inside the proboscis sheath. A lateral vessel from the cephalic vessels, on the other hand, comes down outside the cerebral ganglia ( Figure 20a ). There are no pseudometameric anastomoses of blood vessels. The dorsal and lateral vessels anastomose at a level, 40 mm from the posterior end of the body. Nerυous system The brain and lateral nerves are covered by a thin layer of fibrous connective tissue. The cerebral ganglia are small; they lie immediately outside the large rhynchocoel and have neither neurochord cells nor an inner neurilemma. The nervous system has no accessory lateral nerves. The dorsal and ventral ganglia are not demarcated externally. The ventral ganglia are not distinctly separated from the dorsal ganglia except posteriorly ( Figures 18a and 20a, g ). The dorsal and ventral fibre cores, measuring 140 mm in length, are not divided anterior to the middle portion of the brain; the dorsal cores ( 30 mm long), are less voluminous than the ventral cores ( Figure 18a ). The ventral ganglia behind the posterior end of the dorsal ganglia do not immediately extend laterally to form the lateral nerve cords ( Figure 20a ). The dorsal ganglia do not have bifurcated fibre cores. Figure 20. Sanjuannemertes aeilloaesi , new genus and species , holotype. (a) Transverse sections between 12 and 97 from anterior end of body, showing posterior portion of right dorsal ganglion, dorsal and lateral blood vessel; (b) cephalic furrow united from dorsal and ventral transverse grooves; (c) short canal of cephalic groove above the dermis; (d) posterior ocelli on cerebral sensory organ; (e) ocelli in the right side of the head and frontal glands; (f) cerebral sensory organ in the right side of the head; (g) cerebral sensory organ in the left side of the head and brain lobes; (h) posterior end of cerebral organ canal widened in its outer portion. Scale 100 mm (a–h). Abbreviations: ad, anterior cephalic groove formed by dorsal and ventral grooves united at mid-lateral portion of head; ao, anterior ocellus; br, brain; cb, cephalic blood vessel; cn, cerebral organ canal; cp, canal of cephalic groove in epidermis; cr, circular muscle layer of rhynchodeum; cv, cephalic nerves; cw, cerebral organ canal widened outward; dg, dorsal ganglion; dr, dermis; dv, dorsal blood vessel; eo, eosinophilic glandular mass; fg, frontal glands; gc, ganglionic mass; lv, lateral blood vessel; ne, nephridia; pn, proboscis nerve; po, posterior ocellus; ps, proboscis sheath; rc, rhynchocoel; rd, rhynchodeum; sa, sensory canal of cerebral sensory organ; st, stomach; vg, ventral ganglion; wa, wall of sensory canal of cerebral sensory organ. The dorsal commissure, curving dorsally for 650 mm , is 20 mm in dorsoventral thickness and 30 mm in longitudinal thickness. The ventral commissure is straight and shorter, measuring 300 mm long and 50 mm in dorsoventral thickness and 60 mm in longitudinal thickness; it is situated much farther posteriorly than the dorsal commissure, there being 160 mm between the transverse levels at which they lie. A proboscis nerve trunk arises from the anterior surface of the brain at the root of the dorsal commissure and extends upward, soon branching into 10 nerves. The pair of foregut nerves originate from the ventral ganglia and run anteriorly along the lateral side of the stomach. There are no transverse connectives. Special sensory organ and frontal organ Of the two oblique cephalic grooves, the anterior one is narrow and has a ridge bearing long cilia ( Figure 18e ). The anterior grooves on both the dorsal and ventral sides of the head are united laterally and, at the point of union, form a short canal that extends nearly to the dermis ( Figure 20b, c ). The anterior two ocelli are buried in the middle portion of the head, where the longitudinal musculature is dominant ( Figure 20e ), but the posterior ones are situated above the posterior portion of the cerebral sensory organs ( Figure 20d ). All four ocelli are the same size, measuring 60 mm wide, 90 mm high and 60 mm long ( Figure 20d, e ). Each ocellus consists of an outer layer of ocular cells and an internal cytoplasmic portion. The frontal organ and frontal glands are not well-developed; the former opens on the ventral side of the anterior end of the head, while the latter forms a small mass of glands, 20 mm long ( Figure 20e ). Cephalic glands and sub-muscular glands are absent. The cerebral sensory organs are large and reach the lateral sides of the brain lobes. The one on the right side of the head is crescentic in section, 230X 90 mm in diameter in its anterior portion ( Figure 20f ); whereas on the left side is flattened between the body wall and the brain, being 70 mm wide, 420 mm high and 110 mm long in the middle portion ( Figure 20g ). It has a sensory canal that is 50X 70 mm in diameter and possesses welldeveloped eosinophilic glands on both the dorsal and ventral sides ( Figure 20f, g ). The ganglionic mass is found lateral to the sensory canal ( Figure 20f, g ). The cerebral organ canal, ciliated and 120 mm long, begins at the mid-lateral side of the anterior cephalic groove of the head, and extends posteriorly inside the longitudinal muscle layer of the body wall ( Figures 17d and 20h ). The canal consists of a medial part with a sensory function and a ciliated outer wall that is widened outward forming a sac ( Figure 20h ). A slender nerve from the lateroventral corner of the dorsal ganglion enters the posterior end of the cerebral organ. Excretory and reproductiυe system The excretory system is weakly developed and quite short in the foregut region. No excretory tubules winding around and along the lateral blood vessels have been observed. The single efferent ducts on each side opens dorsolaterally. The gonads are immature.