Thalassas, 27 (2): 169-192 An International Journal of Marine Sciences

COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

KATHE R. JENSEN(1)

Key words: Shelled Sacoglossa, mantle complex, comparative morphology, Heterobranchia, Mollusca

ABSTRACT osphradium is closely associated with shell adductor or cephalic/ pharyngeal retractor muscles, indicating The mantle cavity and pallial structures of that it is associated with the closure of incurrent water 18 species from 8 genera of shelled Sacoglossa flow to the mantle cavity. The genera Cylindrobulla, (Mollusca, Opisthobranchia) have been examined and Ascobulla and Volvatella are unique in having a compared with literature information about several long narrow section of the aperture between the taxa of Heterobranchia. Recent molecular studies anterior incurrent opening and the posterior excurrent have indicated an affiliation of the Sacoglossa and opening. This section forms a functional separation the Siphonariidae, a family of intertidal limpets of water currents and is lined by a row of glandular usually referred to basommatophoran Pulmonata. The bosses. In conclusion the Sacoglossa definitely stand gill of shelled Sacoglossa is unique within the taxa out from opisthobranch taxa, but the similarities with usually referred to Opisthobranchia by its attachment siphonariids are superficial and may be explained as to the surface of the kidney. Morphologically the homoplasies in response to similar environments. sacoglossan gill is similar to that of siphonariids, but In the future the fine structure of the kidney and the latter is located behind the kidney. The heart of pericardium of shelled Sacoglossa should be studied shelled Sacoglossa is almost completely detorted. in detail. This also differs from other basal heterobranch taxa. In the shelled Sacoglossa the inconspicuous INTRODUCTION

Traditionally the Sacoglossa have been included as a monophyletic clade within the Opisthobranchia (Gosliner, 1981; Haszprunar, 1985a; Schmekel, 1985; (1) Zoological Museum (Natural History Museum of Denmark), Jensen, 1996a,b, 1997c; Mikkelsen 1996, 1998). Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark However, inclusion of molecular data has led to E-mail: [email protected] ambiguous relationships among the Euthyneura

169 Kathe R. Jensen

Figure 1: A, Cylindrobulla sp. drawn by K.R. Jensen. B, Ascobulla fischeri from Jensen and Wells, 1990. C, Volvatella viridis from Jensen, 2003. D, Julia japonica redrawn from Kawaguti and Yamasu, 1962. E, Berthelinia darwini from Jensen, 1997a. F, Oxynoe azuropunctata, modified from Jensen, 1980. G, Roburnella wilsoni redrawn from Marcus, 1982. H, Lobiger souverbii redrawn from Marcus and Hughes, 1974

170 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

(=Opisthobranchia + Pulmonata) (Wägele et al., Based on morphological characters the 2003; Grande et al., 2004; Vonnemann et al., 2005). Volvatellidae, Julliidae and Oxynoidae form a The early molecular studies left the Sacoglossa monophyletic suborder, Oxynoacea (Jensen, 1996a), relatively unresolved between Opisthobranchia and and Cylindrobullidae is most likely sister group to Pulmonata (Thollesson, 1999; Dayrat et al., 2001), all remaining Sacoglossa (Jensen, 1996a,b), although but these studies included only one or two species some molecular studies include it in the Oxynoacea of Sacoglossa. Several new studies have indicated a (Händeler and Wägele, 2007; Maeda et al., 2010). closer relationship between the Sacoglossa and the Cylindrobulla and Ascobulla (Fig. 1A, B) have almost Siphonariidae, a family of limpets usually referred to identical cylindrical, thin, fragile shells with elastic the Pulmonata (Grande et al., 2008; Klussmann-Kolb periostracum and a sutural slit and keel (Jensen, 1989, et al., 2008; Dinapoli and Klussmann-Kolb, 2010; 1997c; Jensen and Wells, 1990; Mikkelsen, 1998). Jörger et al., 2010; Dinapoli et al., 2011; Dayrat et Volvatella (Fig. 1C) also has a thin, fragile shell with al., 2011). an elastic periostracum. Posteriorly the aperture is drawn out forming an exhalent spout. The foot is The mantle cavity and the pallial organs have relatively short, even in the extended state, and there been used to elucidate evolutionary theories for the are no parapodia or external pallial lobes to support Gastropoda for many years (reviewed by Lindberg the shell. In all of these three genera the head and and Ponder, 2001). The mantle structures of shelled foot may be completely withdrawn into the shell, and Sacoglossa are poorly studied. Most information the shell may be contracted by an anterior adductor is from descriptions of new species or anatomical muscle (Jensen, 1996a,b, 1997c). re-description of old species. The few existing comparative studies have been conducted from the The Juliidae are the bivalved sacoglossans. The point of view that the Sacoglossa were firmly lodged shell in these species has been divided into two in the Opisthobranchia (Gonor, 1961; Morton, 1988; “valves” of which the left bears the typical spirally Jensen, 1996b, 1997a,b). coiled protoconch and the right one covers the mantle fold. The “valves” are connected by an elastic The shelled Sacoglossa comprises the genera ligament. The animal can be completely retracted into Cylindrobulla, Ascobulla, Volvatella, Berthelinia, the shell (Baba, 1961). In Julia (Fig. 1D) the shell is Julia, Oxynoe, Lobiger and Roburnella (Fig. 1). thick and the protoconch is located far towards the The bivalved genera Tamanovalva, Edenttellina posterior end. Berthelinia (Fig. 1E) has thin shells and Midorigai are here considered synonyms of and the protoconch is located only slightly behind Berthelinia as no synapomorphic characters have been the middorsal point. Several fossil genera are known described to justify separate genera. The inclusion of from this family (Le Renard et al., 1996). Cylindrobulla in the Sacoglossa has been discussed previously (Jensen, 1989, 1996a,b; Mikkelsen, In the Oxynoidae the shell covers only the 1996, 1998), and the phylogenetic relationship of visceral mass and there is a long muscular tail and families and genera of shelled Sacoglossa remains lateral muscular parapodia. The head and anterior unclear (Händeler and Wägele, 2007; Händeler foot may be partly retracted into the shell, but et al., 2009; Maeda et al., 2010). Usually four the tail and parapodia cannot. The aperture of the families of shelled Sacoglossa are recognized: (1) shell is very wide. Oxynoe (Fig. 1F) has one pair Cylindrobullidae (Cylindrobulla), (2) Volvatellidae of parapodia, which can cover the shell almost (Volvatella, Ascobulla), (3) Juliidae (Julia, Berthelinia completely. Roburnella (Fig. 1G) has low parapodia, (Tamanovalva, Edenttellina, Midorigai)), (4) which carry two pairs of rolled extensions; these Oxynoidae (Oxynoe, Lobiger, Roburnella). may be folded across the shell or extended laterally.

171 Kathe R. Jensen

Figure 2: Cylindrobulla sp. A, dorsal view after removal of shell. B, right anterior view, C, left side view, D, ventral view, E, mantle floor after removal of mantle fold. Arrow points to posteriormost point of aperture, i.e., where mantle edge turns forwards. F, ventral view of same, showing entrance to upper whorls. Legend: a – anus; add – shell adductor muscle; ar – adhesive ridge; cs – cephalic shield; dci – dorsal ciliated band; dci2 – dorsal ciliated band of penultimate whorl; dg – digestive gland; f – foot; fa – female aperture; fg – female glands; hy2 – second band of hypobranchial gland; i – intestine; ip – infrapallial lobe; k – apical keel of shell; me – mantle edge; g – gill; he – heart; hy – hypobranchial gland; sg – spawn groove; sh – shell; vci – ventral ciliated band.

172 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

Table 1: List of species and origin of material

Species Locality/year Use Referencea Cylindrobulla phuketi Jensen, 1989 Phuket, Thailand 1990 Dissection Jensen, 1989, 1996b Cylindrobulla sp. Solomon Isl., 2007 Dissection present study Ascobulla ulla (Marcus and Marcus, Florida, 1978 Sections Marcus and Marcus, 1970) 1956; Jensen, 1996b; Mikkelsen, 1996, 1998 Ascobulla fischeri (Adams and Albany, WA, 1988 Dissection, Jensen and Wells, 1990; Angas, 1864) SEM Jensen, 1996b Ascobulla fragilis (Jeffreys, 1856) Mar Menor, Spain, 1993 Dissection present study Volvatella australis Jensen, 1997 Darwin, NT, 1993; Houtman Dissection Jensen, 1997a,b; present Abrolhos Islands, 1994 study Volvatella ventricosa Jensen and Albany, WA, 1988 SEM Jensen and Wells, 1990 Wells, 1990 Volvatella vigorouxi (Montrouzier, Singapore, 2006 Dissection Jensen, 2009 1861) Berthelinia babai (Burn, 1965) Victoria (Australia), 1988 SEM present study Berthelinia darwini Jensen, 1997 Darwin, NT, 1993; Houtman Dissection Jensen, 1997a,b; present Abrolhos Islands, 1994; study Cottesloe, WA, 1996 Berthelinia rottnesti Jensen, 1993 Rottnest Isl, WA 1991 Dissection Jensen, 1993 Julia cf. zebra Kawaguti, 1981 New Caledonia, 1993 Dissection present study Roburnella wilsoni (Tate, 1889) Rottnest Isl., WA 1991, 1996 Dissection Jensen, 1993; present study Lobiger souverbii Fischer, 1856 Barbados, 1977 Dissection Marcus, 1957; present study Oxynoe antillarum Mørch, 1863 St. Thomas, US Virgin Sections, Marcus and Marcus, Islands, 1982; Florida, 1992 dissection 1970; present study Oxynoe azuropunctata Jensen, 1980 Florida, 1978 Dissection Jensen, 1980 Oxynoe viridis (Pease, 1861) Abrolhos Islands, WA, 1994 Dissection, Jensen and Wells, 1990; Darwin, NT, 1993 SEM Jensen, 1997b Oxynoe olivacea Rafinesque, 1819 Sicily, 1998 Dissection Schmekel and Portmann, 1982; present study aDescription or re-description of anatomy

Lobiger (Fig. 1H) has a very flat shell and two pairs of J. japonica Kuroda and Habe, 1951, has been long parapodia, which usually have scalloped edges studied anatomically (Yamasu, 1968), and also the and a brightly colored pigmented band on the inner anatomy of the monospecific genus Roburnella is surface. The parapodia are usually held erect and insufficiently described (Jensen, 1993). The following with infolded margins, but if the animal is disturbed it organs and structures have been examined: Mantle extends the parapodia laterally, exposing the brightly edge, gill, osphradium, heart and pericardium, colored bands. kidney, hypobranchial gland, ciliated bands, pallial gonoducts, intestine and anus, and shell adductor In the present study mantle organs of all shelled muscle. This has been compared with literature sacoglossan genera are examined. Taxon sampling information on heterobranch gastropods, especially is considered important, and particularly those “lower pulmonate” taxa from marine and brackish genera for which anatomy is scantily described water, and the relationship of the Sacoglossa within have been included. Only one species of Julia, the Heterobranchia is discussed.

173 Kathe R. Jensen

Figure 3: Volvatella australis. A, dorsal view after removal of shell. B, ventral view of same. Arrow points to mantle edge with glandular bosses. C, ventro- lateral view of same. D, dorso-lateral view of same after removal of mantle fold. Legend: a – anus; add – shell adductor muscle; add2 – left side attachment of adductor muscle; al – anterior lobes of cephalic shield; dci – dorsal ciliated band; dg – digestive gland; dl – dorsal lobes of cephalic shield; f – foot; g – gill; he – heart; hy – hypobranchial gland; hy2 – second band of hypobranchial gland; i – intestine; ip – infrapallial lobe; me – mantle edge; ph – posterior surface of head; vci – ventral ciliated band.

MATERIALS & METHODS RESULTS

The species used in this study are listed in Table General outline of mantle cavity in shelled 1, and overview drawings of mantle structures and Sacoglossa general anatomy can be found in the publications listed in the table. Most of the species have been anatomically In shelled Sacoglossa the longitudinal axis of the described by the author, and light microscopy body whorl of the shell and visceral mass is in the preparations, some stained with acetocarmine prior same plane as that of the head-foot, i.e., they are almost to mounting, and serial sections (hematoxylin-eosin bilaterally symmetrical. Hence the terms anterior and or toluidine-blue stained), have been re-examined posterior when describing mantle structures refer and photographed with a digital camera mounted on to anterior and posterior in relation to the head-foot dissection and compound microscopes. The genera longitudinal axis. Similarly, left and right refer to that have not previously been examined by the author positions relative to this axis regardless of the fact that have been dissected and also additional specimens of there is an involute spire in most genera. previously studied species have been included. SEM preparations were made by dehydrating in a series of The mantle fold in the shelled Sacoglossa is ethanol-acetone followed by critical point drying and a thin sheet of tissue, which consists mostly of mounting on SEM-stubs. hemolymph spaces and scattered muscle strands

174 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

Figure 4: Posterior mantle edge with glandular bosses. A, Ascobulla fischeri; arrow points to glandular bosses. B, Ascobulla fragilis; arrow points to glandular bosses. C, Light micrograph of Volvatella australis; insert is a higher magnification of same; white arrows point to droplets secreted from glands. D, Light micrograph of section of mantle and infrapallial edges of Ascobulla ulla. Legend: dg – digestive gland; f – foot; gb – glandular boss; ip – infrapallial lobe (secreting callous covering inner lip of shell); me – mantle edge; sg – groove with shell gland; sh – shell; vci – ventral ciliated band. between two layers of epithelium (Fig. 4D). The There is a functional incurrent aperture between the mantle edge is thicker and contains the shell gland adductor muscle and the female genital papilla (Fig. along a submarginal line (Fig. 4C). Ciliated cells 2D). Behind this the mantle cavity is functionally are numerous along the mantle edge, and also gland closed by the ciliated ridges running along the mantle cells occur. margin dorsally and the infrapallial lobe ventrally (Fig. 3B). Along the mantle margin of the narrow part In the Volvatellidae and Cylindrobulla the mantle of the aperture are regularly spaced epithelial bosses cavity is large, extending the full turn of the body along the edges of mantle as well as infrapallial lobe whorl at the level of the gill. The mantle fold (Figs 3B and 4A-C). These bosses contain glands, thus completely surrounds the visceral mass, which which in living animals exude a transparent substance forms the floor of the mantle cavity. Behind the gill in response to minor disturbance. Posteriorly an the ciliated bands and associated glandular bands excurrent aperture is formed by the apical sutural continue into the “upper” (involute) whorls, not slit. In Volvatella the posterior shell spout functions as a separate, exogyrous pallial caecum but as an as excurrent aperture. In juvenile specimens of extension of the mantle cavity (Figs 2F and 3B). Volvatella the anterior aperture is large as in Oxynoe Anteriorly the opening to the mantle cavity is blocked (see below), but the overlapping part of the body whorl by an anterior adhesive ridge and the right side and the visceral mass comprise an increasing part attachment of the adductor muscle (Figs 2B and 3A). of the shell. The infrapallial lobe contains digestive

175 Kathe R. Jensen

Figure 5: Juliidae. A, Berthelinia darwini, right lateral view after removal of shell. B, same (different specimen) after removal of shell and mantle fold. C, same specimen as A, mantle fold, internal view. D, Julia cf. zebra right lateral view after removal of shell. E, same, left lateral view. F, same after removal of mantle fold. Legend: a – anus; add – shell adductor muscle; f – foot; g – gill; he – heart; hy – hypobranchial gland; i – intestine; ip – infrapallial lobe (=left mantle fold); pp – pharyngeal pouch; r – rhinophore; sg – spawn groove; vci – ventral ciliated band-

176 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

gland tubules (Fig. 4D), and in some species of have been counted in large specimens of Ascobulla Volvatella digestive gland tubules also extend into the and Volvatella. Even juvenile specimens of Volvatella mantle roof. with shell length of less than 1 mm and visible protoconch have a fully formed gill. Almost half of In the Juliidae the mantle cavity extends the full the gill lamellae are located ventrally when the animal size of the right valve (Fig. 5A, C, D). The mantle crawls on a horizontal surface. Unless the respiratory fold is attached only along the dorsal line and at current is very strong, these lamellae will most likely the subcentral adductor muscle. In Julia cf. zebra collapse. During feeding (and probably also during there may be a partial anterior closure formed by burrowing in Cylindrobulla and Ascobulla) the shell the long, muscular pharyngeal pouches (Fig. 5D, F), is held slightly upwards, which will permit extension but no observations on living animals are available of all the gill lamellae. to confirm this. In the Oxynoidae there is a large anterior mantle cavity, which can accommodate the In the Juliidae the gill is in a vertical position due to retracted head (Fig. 6A-C, F). Behind this, the mantle the lateral compression of these species. In Berthelinia cavity is closed off by muscles that may be cephalic the gill extends the height of the right valve (Fig. 5A, or pharynx retractors. Between these muscles the C), but in Julia the gill continues across the middorsal mantle fold is attached by an adhesive ridge to the thin line to the left side (Fig. 5E). In Oxynoe the gill is epithelium covering the retracted pharyngeal complex. located rather far towards the posterior end, probably The mantle cavity opens on the right side between the to make room for the pharyngeal complex when this is retractor muscle and the conspicuous female genital retracted (Fig. 6A-B). Each gill lamella may be folded papilla, behind which the mantle cavity of Oxynoe is (Mikkelsen, 1998) or smooth, and it may be longer functionally closed by the base of the right parapodium. towards one end (Fig. 7D). The shape does not seem In Roburnella two incurrent openings may be formed if to be species specific, but may be related to individual the basal parapodium is contracted, leaving an opening size, larger specimens needing a larger respiratory between the two parapodial extensions at the level of surface. Short lamellae are found interspersed with the gill. Posteriorly an excurrent aperture is formed by long lamellae of the full gill length (Fig. 7A-B). The the mantle edge, which is reflected over the posterior epithelium of the gill lamellae is ciliated, though part of the shell aperture. In Lobiger the posterior the cilia do not form discrete bands; sometimes cilia margin of the mantle fold, which forms the excurrent occur in tufts scattered on the surface, sometimes the siphon, is displaced from the “spire” of the shell, which cilia appear to be evenly distributed on the surface. is located on the left side. In Oxynoe and Lobiger the Hemolymph spaces (vessels) are found in each lamella mantle edge often has pigmented spots as found on (Fig. 8B, D). Along the anterior edge a distinct “efferent rhinophores, parapodial and foot margins. vessel” is found. In dissections it was not possible to see whether it connects the gill sinuses to the auricle Gill or the pericardium. A corresponding “afferent vessel” runs along the posterior edge of the gill. The sacoglossan gill consists of a band of parallel lamellae located in the mantle roof behind the heart Osphradium and on the surface of the kidney. In Cylindrobulla, Ascobulla and Volvatella the gill extends a full 360° The small osphradium is located on the right side (or more when the outer lip overlaps the reflected of the mantle roof, adjacent to the attachment point inner lip). It consists of longitudinal lamellae, of the adductor (or retractor) muscle. It is innervated completely surrounding the visceral mass of the body by a small osphradial ganglion, connected to the whorl (Figs. 2A-D and 3A-C). More than 100 lamellae supraesophageal ganglion. Due to the tough texture

177 Kathe R. Jensen

Figure 6: Oxynoidae. A, Oxynoe viridis after removal of shell. B, Oxynoe olivacea after removal of shell. C, Oxynoe antillarum after removing shell and mantle fold and cutting off right parapodium. D, Roburnella wilsoni after removal of shell and cutting off parapodia. E, same after removal of mantle fold. F, Lobiger souverbii after removal of parapodia. Legend: a – anus; dci – dorsal ciliated band; dg – digestive gland; e – eye; ep – esophageal pouch; fp – female genital papilla; g – gill; he – heart; hy – hypobranchial gland; mb – muscular bulges of oral tube; me – mantle edge; pa – parapodium; ph – pharynx; pl – parapodial lobe (cut off); pp – pharyngeal pouch; r – rhinophore; rm – retractor muscle; si – exhalant siphon; t – tail; vci – ventral ciliated band.

178 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

of the adductor muscle the mantle is often torn at this or syrinx has not been observed, but in some cases point during dissection as well as serial sectioning. branching vessels occur in the pericardium (Fig. This makes the osphradium difficult to locate. Usually 10A). Marcus (1957) described a renal pore behind the osphradial ganglion can be identified (Fig. 9C, the gill in Lobiger souverbii, and in Berthelinia limax D), but not the fine structure of the osphradium. In and Julia japonica the renal pore was found between Cylindrobulla and Volvatella the osphradium is oval the gill lamellae towards the dorsal end (Baba, 1961; (Fig. 9A, B), in Berthelinia and Lobiger it appears to be Yamasu, 1968). circular (Fig. 9C, D). The position of the osphradium indicates that it is associated with closure of the Hypobranchial gland anterior (incurrent) mantle opening. In all shelled sacoglossans there is a band of Heart and pericardium white mucus secreting glands behind the gill (Figs 2A-D, 3A-C, 5A, C-D, 6A, 10C). This is considered The heart, composed of one auricle and one homologous to the hypobranchial gland of other ventricle, is located in a thin-walled pericardial sac gastropods. In some species, e.g. Volvatella vigourouxi in front of the gill, i.e., the pericardial complex is the glandular cells are orange in live animals rather than located in the mantle roof. The auricle is usually white (Jensen, 2009). In Cylindrobulla, Ascobulla and triangular in outline (Fig. 10A, D) and the ventricle Volvatella there is a second glandular band behind the may be triangular (Fig. 10A, C, D) or almost circular dorsal ciliated band (Figs 2A-C and 3A-C). In Oxynoe (Fig. 10B). In Ascobulla and Volvatella the heart is the corresponding white gland forms a triangular patch seen approximately in the dorsal midline of the body just inside the mantle margin behind the gill (Fig. 6A); (Fig. 3A) and bent at an angle relative to the gill. The it continues as a narrow band along the afferent vessel aorta passes from the ventricle into the visceral mass, as in the other species. There is a second glandular which marks the left anterior border of the mantle area associated with the dorsal ciliated band near cavity. Marcus and Marcus (1956) described the heart the excurrent opening (Fig. 10C); this has previously of Ascobulla ulla (as Cylindrobulla sp.) as torted, i.e., been interpreted as the hypobranchial gland (Jensen with the ventricle posterior to the auricle. This has not and Wells, 1990). In Lobiger and Roburnella the been seen in any of the shelled species studied here; the hypobranchial gland is very thick. auricle is always behind the ventricle. In the Oxynoidae the heart is big and the ventricle is oriented slightly Ciliated bands towards the left (Figs 6B and 10D). In Berthelinia the heart is located dorsally in the mantle fold (Fig. 5C). In This is one of the important synapomorphies of the Julia it is found on the left side of the body, near the Euthyneura and lower Heterobranchia and the outline “posterior” end of the gill (Fig. 5E). Pericardial glands, of these bands have been used to develop phylogenetic as seen in many Acteonoidea (Rudman, 1972a,b,c), hypotheses (Haszprunar, 1985a; Mikkelsen, 1996). In have not been observed in any species of Sacoglossa. shelled Sacoglossa the ciliated bands are usually not distinctly elevated from the surrounding epithelium, Kidney but the cilia appear to be both longer and denser than in the general mantle surface (Fig. 4D). The ventral The kidney forms a thin layer of tubules running ciliated band is usually more elevated than the dorsal parallel to the gill lamellae, which are attached to the one (Fig. 2E, F), and in many species the anus opens surface of the kidney (Fig. 8A, C). The tubules are just anterior to the ventral ciliated band (Figs 2E, 3D, lined by highly vacuolized epithelium (Fig. 8B, D), 5F, 6C). In Cylindrobulla, Ascobulla and Volvatella characteristic of gastropod kidneys. A nephrostome the ciliated bands are rather wide, about the same

179 Kathe R. Jensen

Figure 7: SEM photos of sacoglossan gills. A, Ascobulla fischeri. B, Volvatella ventricosa. C, Berthelinia babai. D, Oxynoe viridis. Legend: hy – hypobranchial gland; pe – pericardium; si – exhalant siphon. width as the gill, and they are curved forwards along by contraction of the shell adductor muscle where the right edge of the gill in the mantle roof and along present. In the upper whorls the ciliated bands may the infrapallial lobe in the mantle floor (Fig. 2D). have a respiratory function; hemolymph spaces occur In the Juliidae the ciliated bands are very narrow below the epithelium of the ventral ciliated band. and at least the one on the mantle floor (on the right side of the body) distinctly elevated (Fig. 5F). In the Pallial gonoducts Oxynoidae the ciliated bands are indistinct. The fact that the ciliated bands extend into the upper whorls of There are no real pallial gonoducts in the the shell, all the way to but not into the protoconch, Sacoglossa. The duct of the bursa copulatrix enters shows that this is part of the mantle cavity rather than the female genital papilla at the mantle floor on the a pallial caecum as seen in many Acteonoidea and right anterior side. In Berthelinia the female mucus Cephalaspidea (Rudman, 1972a,b,c; Brace, 1977). gland may form a bulge in the mantle floor (right Probably it is the long dense cilia of the prominent side of body), but it remains embedded in the visceral ciliated bands that drive the ventilation current of mass. In the Oxynoidae the female genital papilla is the sacoglossan mantle cavity. This may be aided very big (Fig. 6A,C-E), whereas there is no distinct

180 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

papilla at the female genital opening of Cylindrobulla it is very difficult to cut loose from the mantle fold (Fig. 2D). The vas deferens is embedded in the body without ripping the latter. wall medially to the female genital opening and thus not visible inside the mantle cavity. There is a A shell adductor muscle has also been identified in separate penial opening in the cephalic region. Cylindrobulla (Jensen, 1989; Mikkelsen, 1998; present study), Ascobulla (Marcus and Marcus, 1956; Jensen Intestine and anus and Wells, 1990; Mikkelsen, 1998), and Volvatella (Baba, 1966; Jensen and Wells, 1990; Jensen, 1997a,b; The intestine of shelled sacoglossans is short, present study). Here it is less conspicuous, running ascending through the digestive gland from the stomach diagonally from the anterior right corner of the mantle to the mantle floor. In Cylindrobulla, Ascobulla and fold (and shell) (Figs 2A and 3A) to the inner lip of the Volvatella the intestine is seen as a white line on the shell on the ventral side (Fig. 3C). In the Oxynoidae mantle floor on the surface of the digestive gland; the the aperture is wide and there is no use for an adductor anus is in front of the ventral ciliated band (Figs 2E muscle. The muscles attaching to the shell are the and 3D). In Berthelinia the intestine appears on the retractors of the head and/or the pharyngeal complex. surface of the mantle floor behind the bulge formed by the mucus gland of the female reproductive system DISCUSSION and in front the ciliated band (Fig. 5B). In Julia only a short segment of the intestine is visible dorsally Examination of the mantle cavity and its associated on the surface of the digestive gland in front of the structures in 18 species of shelled Sacoglossa from ciliated band (Fig. 5F). In Roburnella the intestine runs all 8 genera has yielded several conclusions: (1) diagonally on the surface of the digestive gland on the The inclusion of the genus Cylindrobulla in the right side. The anus opens towards the ventral side (Fig. Sacoglossa is confirmed. Most of the characters 6E). In Oxynoe (Fig. 6C) and Lobiger the anus is more shared with other shelled sacoglossans have been dorsal on the surface of the digestive gland. Pigmented considered plesiomorphic, but in this study the anal glands, as seen in several lower heterobranchs character of regularly spaced glandular bosses along (Haszprunar, 1985a; Ponder, 1991), have not been the posterior mantle and infrapallial lobe edges observed in shelled Sacoglossa. has been found in Cylindrobulla, Ascobulla and Volvatella. This character has not been described in Shell adductor muscles other opisthobranchs or heterobranchs, and if this is considered a synapomorphy, then Cylindrobulla A shell adductor muscle forming a scar on the may be included in the suborder Oxynoacea. Also, shell valves was first described for the Juliidae when the long lamellate gill attached throughout its length these were still thought to be bivalves. This muscle to the surface of the kidney and the diagonal shell has been intensively studied in the Japanese species adductor muscle are synapomorphies shared by the Berthelinia (=Tamanovalva) limax (Kawaguti three genera. However, the suprageneric affiliations and Yamasu, 1960a,b). It develops soon after of Cylindrobulla cannot be determined on the basis of metamorphosis as a diagonal muscle connecting only shell and mantle characters. the incipient right “valve” and the left side of the teleoconch. In the adult Juliidae the adductor (2) The gill consisting of parallel folds forming muscle is usually distinctly visible by its darker or a band across the mantle roof differs from that of denser colour (Fig. 5A-F). It is surrounded by a thin all other heterobranchs by being located on the epithelium and therefore easily separated from the surface of the kidney. This has been described many visceral mass during dissection. On the other hand times before in individual species descriptions, e.g.,

181 Kathe R. Jensen

Figure 8: Light micrographs of sacoglossan gill and kidney. A, Ascobulla ulla stained with hematoxylin-eosin. B, same at higher magnification. C, Oxynoe antillarum stained with toluidine-blue. D, same at higher magnification. Legend: dg – digestive gland; g – gill lamellae; k – kidney tubule with vacuolized epithelium; mc – mantle cavity; pa - parapodium

Ascobulla ulla (as Cylindrobulla sp.) (Marcus and (3) Shell adductor muscles are found in Marcus, 1956), Berthelinia (=Tamanovalva) limax Cylindrobulla, Ascobulla, Volvatella and the bivalved (Baba, 1961), Oxynoe viridis (as Lophocercus viridis) Juliidae. The osphradium is located where this muscle (Eliot, 1906), Lobiger serradifalci (Mazzarelli, 1892) attaches to the mantle fold, indicating that the muscle and L. souverbii (Marcus, 1957), but apparently is activated when the osphradium is stimulated. In the nobody has attached any phylogenetic importance to Oxynoidae retractor muscles, cephalic or pharyngeal, it. Gill structure and attachment differ widely among serve as attachment of the body and mantle fold to the Heterobranchia (Table 2), and it seems likely that the shell on the left side, and on the right side are homoplasies are involved. associated with the osphradium, thus probably having

182 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

Figure 9: Position of osphradium or osphradial ganglion in shelled sacoglossans. A, Cylindrobulla phuketi; arrow points to presumed osphradium. B, Volvatella australis; arrow points to osphradium. C, Berthelinia darwini; arrow points to osphradial ganglion. D, Lobiger souverbii; arrow points to osphradial ganglion. Legend: add – shell adductor muscle; g – gill; rm – retractor muscle.

the function of retracting the head, which closes anteriorly by muscles and an adhesive ridge, and off the incurrent opening, when adverse factors are opens on the right side of the body. This indicates detected by the osphradium. a 90º (partial) detorsion. However, the heart is (4) In the bivalved genus Julia the mantle cavity oriented at an angle which is usually less than 45º extends across the middorsal line of the shell. This from the longitudinal axis of the body, indicating is interpreted here as more ancestral than the shorter almost complete detorsion. Also, the heart is located mantle cavity of Berthelinia, covering only the right approximately in the middorsal line, as in the non- side of the body. shelled Sacoglossa. The almost completely detorted (5) The sacoglossan mantle cavity is closed off heart as well as its position differ from the situation in

183 Kathe R. Jensen

Figure 10: Heart of shelled sacoglossans. A, Volvatella australis. B, Ascobulla fragilis. C, Oxynoe azuropunctata. D, Lobiger souverbii. Legend: au – auricle; dci – dorsal ciliated band (apparently on glandular tissue); g – gill; hy – hypobranchial gland; pe – pericardium; ve – ventricle.

Acteonidae (Fretter and Graham, 1954; Brace, 1977) (Haszprunar, 1985a). Since then the basal clades and also from lower pulmonates (Table 2; Brace, of Opisthobranchia, Pulmonata and “lower 1983). Heterobranchia” have been moved around in almost every analysis that has been published (Grande et al., Comparison with other Heterobranchia 2008; Klussmann-Kolb et al., 2008; Malaquias et al., 2009; Dinapoli and Klussmann-Kolb, 2010; Jörger et The reorganization of Euthyneura (= al., 2010; Dinapoli et al., 2011; Dayrat et al., 2011). Opisthobranchia + Pulmonata) was initiated with the For comparison with shelled Sacoglossa several of resurrection and re-definition of the Heterobranchia these “problematic” taxa were selected (Table 2).

184 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

Omalogyridae, Cornirostridae and Orbitestellidae Interpretation of the evolution of gastropod are classical “lower Heterobranchia”, i.e. small mantle cavity and the pallial organs has changed species with a dextral shell (Haszprunar, 1988; through time (Lindberg and Ponder, 2001). In Ponder, 1990a,b, 1991). The Glacidorbidae and many “lower Heterobranchia” the gill is absent Amphiboloidea also have dextrally coiled shells, but or reduced (Table 2). In the species which have have variously been included in the Pulmonata or a gill it is interpreted as a secondary one, due to “lower Heterobranchia” (Ponder, 1986; Golding et absence of skeletal rod and arrangement of cilia al., 2007). The Pyramidelloidea has been transferred (Ponder and Lindberg, 1997). True ctenidia are from “Prosobranchia” to “Opisthobranchia” connected to vessels originating from the kidney based on morphological characters (Fretter and (Ponder and Lindberg, 1997). The sacoglossan gill Graham, 1949), and later to “lower Heterobranchia” lamellae also contain vessels that surround the renal (Haszprunar, 1985a). Pyramidelloidea typically tubules, whereas in “Architectibranchia” (sensu have small heterostrophic shells, but limpet-like Haszprunar, 1985a) as well as most Cephalaspidea forms exist (Ponder, 1987). The Acteonoidea were the kidney is wedged in between the gill and the traditionally included in the Opisthobranchia pericardium, and vessels from the gill run across (Fretter & Graham, 1954), but were transferred to an the kidney (Fretter and Graham, 1954; Rudman, informal group, “Architectibranchia” (Haszprunar, 1972a,b,c; Brace, 1977). Ponder and Lindberg 1985a; Grande et al., 2004). Morphologically the (1997) claim that the kidney is located to the right Acteonoidea are similar to many Cephalaspidea of the pericardium in heterobranchs as well as having typical “bubble-shells” (Mikkelsen, 1996). caenogastropods. In the shelled Sacoglossa the The genus Akera is included in the Anaspidea kidney is located behind the pericardium, and blood in morphological as well as molecular studies flow is most likely from mantle vessels through the (Morton, 1972), but was previously considered a kidney to the gill lamellae and from the gill to the typical cephalaspidean (Brace, 1977). Its shell has auricle. A direct connection from the kidney to several similarities to that of Cylindrobulla and the pericardium may also be possible considering Ascobulla, e.g., sutural slit and keel (Jensen, 1996b). the close relationship between these organs in The Siphonariidae are limpet-like gastropods, shell-less Plakobranchoidea. Unfortunately the fine usually included in basommatophoran Pulmonata structure of the kidney of shelled Sacoglossa (Yonge, 1952; Marcus and Marcus, 1960), although has not been described, but the ultrastructure of anatomical affinities to Opisthobranchia have the kidney and excretory system was studied in been pointed out (Köhler, 1893). Till recently the two non-shelled species (Fahrner and Haszprunar, Heterobranchia were assumed to have affiliations 2001). They found podocytes in the epicardial with taenioglossate Caenogastropoda (Haszprunar, wall of the auricle of Bosellia mimetica. This is 1985a; Ponder, 1991). However, the inclusion of the considered plesiomorphic in the Mollusca. family Hyalogyrinidae with rhipidoglossate radula and apparently a true ctenidium in the Heterobranchia The sacoglossan gill has been interpreted due to their heterostrophic shells and presence as a variation of the typical opisthobranch of ciliated bands in the mantle cavity (Warén plicatidium (Mikkelsen, 1996). However, a band and Bouchet, 2009) has added further confusion of simple, sparsely ciliated folds is difficult to to the origin of Heterobranchia. Hyalogyrinidae homologize with the complex structures found in have typical dextral shells with a large umbilicus. “Architectibranchia”, or Cephalaspidea (Fretter and In shelled Sacoglossa the body whorl completely Graham, 1954; Rudman, 1972a,b,c; Brace, 1977). overgrows the “upper” (inner) whorls, so that in The gill structure is superficially similar to the adult animals the protoconch is completely hidden. gills found in siphonariids, i.e., it consists of a band

185 Kathe R. Jensen ost completely ost completely ntle opening to ntle opening 56; Baba, 1961, 1961, 56; Baba, Middorsal,in front of kidney); (and gill alm posteriorly posteriorly 1966; Gonor, 1961; 1989, 1993, Jensen, 1997a,b, 1996a,b, and Jensen 2009; Wells, 1990; present study detorted detorted to surface of kidney of kidney to surface dorsal ciliated band Small;anterior; right, next to adductor whorl innermost floor mantle in Deep in front of ventral ciliated band; facing 1892; Mazzarelli, Marcus and Marcus, 19 In mantle roof; band band roof; mantle In gill overlying Band of parallel Band of parallel lamellae encircling attached body whorl; Dorsal and ventral ventral and Dorsal right bands from ma s mantle s mantle nted nted Siphonariidae Sacoglossa Sacoglossa Siphonariidae Köhler, 1893; 1893; Köhler, Marcus and de 1960; Marcus, and Villiers 1987 Hodgson, mantle floor) kidney cavity posterior to posterior cavity gill anterior end of end anterior muscle shell of side On right at mantle floor; exhalent opening 1945; Hubendick, 1952; Yonge, (one in mantle in mantle (one one in roof, ventral and Dorsal bands transversely acros U-shaped band of band U-shaped parallel lamellae; attached; behind anterior left On transversely side; orie Close to right Large; 2 parts parts Large; 2 all, anterior; all, anterior; vity vity Sm In mantle roof; roof; In mantle Akera Akera Posterior to ciliated ventral exhalent at band, 1972; Morton, 1977 Brace, Absent Absent Narrow bands along along Curving bands on backwards right side into Narrow Absent Absent Plicate; partly partly Plicate; attached by membrane to On left anterior left anterior On mantle of side ca siphon long, attached attached long, caecum pallial kidney and floor on right side side on right anterior to gill b,c; Brace, b,c; Brace, e nd floor of mantle of nd floor Large; left side of of side left Large; Small, anterior; on anterior; Small, side left Graham, and Fretter 1954; Rudman, 1972a, mantle roof roof mantle edge mantle From (anteriorly or exhalent siphon) attached (to roof a Associated with band 1977 into pallial caecum caecum into pallial cavity) Deep in mantle mantle in Deep left of cavity; ciliated ventral ciliary bands, or bands, ciliary absent Posteriorly or Posteriorly transversely on left sid terior of of terior nd nd mantle cavity; cavity; mantle aszprunar, aszprunar, Simple; left of of left Simple; dorsal ciliated ba anterior to anus 1985b; Ponder, 1987 on right side side on right Fretter and Fretter 1949; Graham, H Not reaching margin posterior of Behind kidney; in or mass visceral pos Pigmented mantle mantle Pigmented organ mantle of end cavity mantle roof roof mantle lidae Pyramidellidae Acteonoidea Pyramidellidae lidae nt Absent or present partly Plicate; antle roof roof antle roof; In mantle ity ity 007 kidney; kidney; or pigmented; anterior right side roof mantle of Goldingal., et 2 absent Full length of of length Full or cavity, mantle only exhalent On extreme left On extreme mantle of side cav Anterior right side side right Anterior posterior In left In m r, 1986; 1986; r, 1945; Hubendick, terior terior Absent or but indistinct, to ciliated mantle Absent Anterior Behind at kidney, pos fold present mantle wall Right posterior In mantle In mantle roof; large Comparison of mantle structures of shelled Sacoglossa and 9 other heterobranch taxa of shelled Sacoglossa and 9 other heterobranch Comparison of mantle structures nt; left Absent at Simple; ent on ent art antle roof antle roof Table 2: Table right side pigmented Absent Abse Prese mantle of part cavity In mantle roof; roof; In mantle anterior to he Absent; ciliated lobe pres gland Mantle behind present osphradium; Behind kidney in posterior m In posterior In posterior e Orbitestellidae Glacidorbidae Glacidorbidae Amphibo Orbitestellidae e ind gill; stly free free stly allial tentacle ill; in bipectinate; mo left anterior, Beh anterior to anterior heart posterior posterior roof mantle Possibly by replaced p Absent; pigmented present strip of the right To gill base 1990b Ponder, 1990a Ponder, Ponde Behind of left kidney; g t side) t side) ght side side ght ociated ociated terior terior 988 posterior posterior anus (or from on lef Ass with ciliated bands across pos cavity mantle on ri Haszprunar, 1 mantle wall wall mantle Character Omalogyridae Cornirostrida Triangular, Omalogyridae Character Gill Absent Absent Osphradium Small; Kidney roof; In mantle Ciliated bands Anteriorly Hypobranchial gland Heart Obliquely in Deep Anus 1948; Fretter, References

186 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

of parallel lamellae, each lamella consisting of a derived in several heterobranch groups. Apparently fold of epithelium with scattered ciliated cells and they are absent in several small groups (Table 2). surrounding a hemocoelic space with transverse In shelled Sacoglossa the ciliated bands extend into trabeculae (Villiers and Hodgson, 1987). However, the upper whorls, forming a small cavity on the in the Siphonariidae the gill is located behind (and surface of the visceral mass. This was interpreted above) the kidney, and the heart is turned about as an “attached” pallial caecum (Jensen, 1996a,b), 90º from the longitudinal axis of the body (Yonge, but probably should be considered a true part of the 1952; Villier and Hodgson, 1987). Also, growth of mantle cavity. The pallial caecum of Akera, although gill lamellae in Siphonaria may be different from attached to the visceral mass, only extends over one that of shelled Sacoglossa. In Siphonaria capensis whorl (360°) (Morton, 1972). In Siphonaria dorsal the largest gill lamella are found towards the center and ventral ciliated bands are located behind the gill, of the U-shaped gill (Villier and Hodgson, 1987), following the outline of the posterior gill margin indicating that new lamellae are added towards the (Villier and Hodgson, 1987), and a small pallial ends. In shelled Sacoglossa short gill lamellae occur caecum has been described in S. hispida (Marcus and in between long ones, and only towards the inner Marcus, 1960). and outer ends are lamellae generally shorter. This indicates that addition of new lamellae during growth The osphradium of heterobranch gastropods is occurs between two existing lamellae. This growth less complex in structure than that of caenogastropods pattern has also been suggested for Siphonaria (Haszprunar, 1985b). In Architectonicids and alternata (Yonge, 1952). Architectonicidae, another pyramidellids the osphradium is located in the left “lower heterobranch” family, also has a lamellate side of the mantle cavity. In most cephalaspids the gill, but here the gill lamellae are formed by osphradium is located to the right of the attachment folding of the epithelium of the hypobranchial membrane of the gill (Edlinger, 1980; Haszprunar, gland (Haszprunar, 1988). Thus the gill lamellae 1985b). In Acteon it is located in front of the gill are solid, composed of two cell layers. In the base (Edlinger, 1980), whereas it is at the extreme limpet-like pyramidelloid Amathina tricarinata the anterior left side of the mantle cavity in some other gill is also composed of parallel lamellae attached acteonids (Rudman, 1972a). An osphradium has not to the mantle roof. However, the gill is located in been described in Hydatina, Bullina and Micromelo front of the kidney, and the pericardium and heart (Rudman, 1972b,c), and it seems to be absent in most are located behind this (Ponder, 1987). In some of the heterobranch groups that do not have a gill “Architectibranchia”, e.g. Acteon tornatilis the gill (Table 2). In the shelled Sacoglossa the osphradium is attached by a membrane to the edge of the kidney, is inconspicuous in preserved specimens, but may but the gill structure of these species is much more be identified more easily in live animals (Gonor, complex (Brace, 1977; Jensen, 1996b), and in the 1961). Its fine structure has not been examined, Siphonariidae the kidney is wedged in between the but it is associated with the adductor or retractor gill and pericardium, and furthermore it is divided muscle located at the anterior right opening of the into a dorsal and ventral lobe (Yonge, 1952; Villier mantle cavity. A similar position of the osphradium and Hodgson, 1987). has been observed in several species of Siphonaria (Hubendick, 1945; Yonge, 1952; Marcus and Marcus, Opposing ciliated bands in mantle roof and floor 1960) and also in Amphiboloidea (Table 2) and the are considered a synapomorphy of all Heterobranchia eupulmonate Chilinidae (Brace, 1983). In Akera (Haszprunar, 1985a; Ponder and Lindberg, 1997; the osphradium is also at the right anterior corner Warén and Bouchet, 2009), though Ponder (1991) of the mantle cavity, but to the right of the anterior noted that ciliated bands were probably independently adductor muscle (Brace, 1977).

187 Kathe R. Jensen

The hypobranchial gland is generally thought to have an unresolved trichotomy. What seems clear be homologous throughout the Gastropoda (Fretter is that the Sacoglossa are not closely related to and Graham, 1954; Ponder and Lindberg, 1997). any of the traditional opisthobranch groups. The However, several other glands may occur in the sacoglossan gill is probably not homologous with mantle cavity of the Heterobranchia. These include the plicatidium, and the almost completely detorted the opaline and purple glands of Anaspidea (Morton, heart shows that they are probably not closely 1972; Dayrat and Tillier, 2002), repugnatorial glands related to “lower Heterobranchia”. However, it is of several Acteonoidea and Cephalaspidea (Fretter not possible to infer a phylogenetic relationship with and Graham, 1954; Rudman, 1972a,b,c; Wägele and the Siphonarioidea or with any pulmonate group, Klussmann-Kolb, 2005), and the “pigmented mantle including Pyramidelloidea and Acochlidia. If further organ” (PMO) of several “lower heterobranchs” molecular studies should continue to support an (Ponder, 1987; Table 2). In the shelled Sacoglossa affiliation of the Sacoglossa and the Siphonariidae, glands are located along the mantle margin, but more other organ systems of both groups need to be densely between the gill and dorsal ciliated band. analyzed by comparative morphology. According to Fretter and Graham (1954) the ciliated bands are formed in the hypobranchial area, and ACKNOWLEDGEMENTS the glands accompanying the bands are considered homologous with the hypobranchial gland. The majority of the material used in the present study has been collected during several international The present study has found a number of workshops in Australia. The organizers of these morphological similarities between the shelled workshops are thanked for providing the permits Sacoglossa and the Siphonariidae. However, these and facilities and Carlsberg Foundation for funding are either plesiomorphic (ciliated bands, lamellate my participation, and for funding microscopes and and attached gill with different location) or possibly digital camera equipment. Collecting in Ghizo, homoplasies (position of osphradium). The shell Solomon Islands was funded by a grant from muscles of the siphonariids are probably not Villum Kann Rasmussen Foundation to prof. R.M. homologous to the shell adductor muscle or cephalic Kristensen of the Zoological Museum (SNM) in retractor muscle of the Sacoglossa, and therefore the Copenhagen, and was part of the Danish Galathea association of the osphradium with muscles at mantle 3 Expedition 2006-2007. Specimens from Florida opening are related to function rather than being were collected as part of my Ph.D. study at Florida homologous. Most siphonariids are intertidal and Institute of Technology, Melbourne, Florida. Dr. most sacoglossans also live in shallow water. Hence J. Just, formerly at the Zoological Museum in the morphological similarities may be interpreted as Copenhagen, now in Townsville, Australia, collected adaptations to a similar environment. Some molecular the specimens of Lobiger souverbii in Barbados, studies have the Sacoglossa and Siphonarioidea as Dr. P. Gianguzza, University of Palermo collected sister groups and the combined clade as sister group Oxynoe olivacea in Sicily, Dr. J. Templado, Museo to the remaining Pulmonata plus Glacidorboidea, National de Ciencias Naturales in Madrid provided Amphiboloidea, Pyramidelloidea and Acochlidia the specimens of Ascobulla fragilis, and Julia cf. (Klussmann-Kolb et al., 2008; Jörger et al., 2010). zebra was obtained from the Muséum national Others have a paraphyletic grade of Sacoglossa, d’Histoire naturelle in Paris thanks to Dr. P. Bouchet. Siphonarioidea and the above groups, with either Finally I wish to thank Dr. J. Troncoso and his team the Sacoglossa being basal to the remaining groups for organizing the 3rd International Opisthobranch (Dayrat et al., 2011) or the Siphonarioidea (Dinapoli Workshop, providing the opportunity to present the et al., 2011). Dinapoli and Klussmann-Kolb (2010) results of the present study.

188 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

REFERENCES Ultrastruktur und Physiologie der chemischen Sinnesorgane einiger Cephalaspidea (Mollusca, Baba K. (1961). On the identification and the affinity of Opisthobranchia). Zoologischer Anzeiger, 205: 90-112. Tamanovalva limax, a bivalved sacoglossan mollusc Eliot CH (1906). Nudibranchs and tectibranchs from the in Japan. Publications of the Seto Marine Biological Indo-Pacific. II., Notes on Lophocercus, Lobiger, Laboratory, 9: 37-62, plates 1-4. Haminaea and Newnesia. Journal of Conchology, 11: Baba, K. 1966. Gross anatomy of the specimens of the 298-315. shelled sacoglossan Volvatella (=Arthessa) collected Fahrner A, Haszprunar G (2001). Anatomy and ultrastructure from Okino-Erubu Island, southern Kyushu, Japan of the excretory system of a heart-bearing and a (Nudibranchia). Publications of the Seto Marine heart-less sacoglossan gastropod (Opisthobranchia, Biological Laboratory, 14: 197-205, plates 7-10. Sacoglossa). Zoomorphology, 121: 85-93. Brace RC (1977). The functional anatomy of the mantle Fretter V (1948). The structure and life history of some complex and columellar muscle of tectibranch molluscs minute prosobranchs of rock pools: Skeneopsis (Gastropoda: Opisthobranchia), and its bearing on the planorbis (Fabricius), Omalogyra atomus (Philippi), evolution of opisthobranch organization. Philosophical Rissoella diaphana (Alder) and Rissoella opalina Transactions of the Royal Society of London B, 277: (Jeffreys). Journal of the Marine Biological Association 1-56. of the U.K., 27: 597-632. Brace RC (1983). Observations on the morphology and Fretter V, Graham A (1949). The structure and mode of life behaviour of Chiline fluctuosa Gray (Chilinidae), with of the Pyramidellidae, parasitic opisthobranchs. Journal a discussion on the early evolution of pulmonate of the Marine Biological Association of the U.K., 28: gastropods. Philosophical Transactions of the Royal 493-532. Society of London B, 300: 463-491. Fretter V, Graham A (1954). Observations on the Dayrat B, Tillier A, Lecointre G, Tillier S (2001). New opisthobranch mollusc Acteon tornatilis (L.). Journal clades of euthyneuran gastropods (Mollusca) from of the Marine Biological Association of the United 28S rRNA sequences. Molecular Phylogenetics and Kingdom, 33: 565-585. Evolution, 19: 225-235. Golding RE, Ponder WF, Byrne M (2007). Taxonomy Dayrat B, Tillier S (2002). Evolutionary relationships and anatomy of Amphiboloidea (Gastropoda: of euthyneuran gastropods (Mollusca): a cladistic Heterobranchia: Archaeopulmonata). Zootaxa, 1476: re-evaluation of morphological characters. Zoological 1-50. Journal of the Linnean Society, 135: 403-470. Gonor JJ (1961). Observations on the biology of Lobiger Dayrat B, Conrad M, Balaya S, White TR, Albrecht C, serradifalci, a shelled sacoglossan opisthobranch from Golding R, Gomes SR, Harasewych MG, Martins AM the Mediterranean. Vie et Milieu, 12:381-403. de F (2011). Phylogenetic relationships and evolution of Gosliner TM (1981). Origins and relationships of pulmonate gastropods (Mollusca): New insights from primitive members of the Opisthobranchia (Mollusca: increased taxon sampling. Molecular Phylogenetics and Gastropoda). Biological Journal of the Linnean Society, Evolution, 59: 425-437. 16: 197-225. Dinapoli A, Klussmann-Kolb A (2010). The long way Grande C, Templado J, Cervera JL, Zardoya R (2004). to diversity – Phylogeny and evolution of the Molecular phylogeny of Euthyneura (Mollusca: Heterobranchia (Mollusca: Gastropoda). Molecular Gastropoda). Molecular Biology and Evolution, 21(2): Phylogenetics and Evolution, 55: 60-76. 303-313. Dinapoli A, Zinssmeister C, Klussmann-Kolb A (2011). Grande, C., Templado, J. and Zardoya, R. 2008. Evolution of New insights into the phylogeny of the Pyramidellidae. gastropod mitochondrial genome arrangements. BMC Journal of Molluscan Studies, 77: 1-7. Evolutionary Biology, 8: 61. Edlinger, K. 1980. Beiträge zur Anatomie, Histologie, Händeler K, Wägele H (2007). Preliminary study on

189 Kathe R. Jensen

molecular phylogeny of Sacoglossa and a compilation Jensen KR (1996b). The Diaphanidae as a possible sister of their food organisms. Bonner zoologische Beiträge, group of the Sacoglossa (Gastropoda, Opisthobranchia). 55(3/4): 231-254. In: J. Taylor, ed, Origin and evolutionary radiation of Händeler K, Grzymbowski YP, Krug PJ, Wägele H (2009). the Mollusca, Oxford University Press, Oxford, pp. Functional chloroplasts in metazoan cells – a unique 231-247. evolutionary strategy in animal life. Frontiers in Jensen KR (1997a). Sacoglossa (Mollusca, Opisthobranchia) Zoology, 6(1): 28. from the Darwin Harbour area, Northern Territory, Haszprunar G (1985a). The Heterobranchia - a new concept Australia. In: J.R. Hanley, G. Caswell, D. Megirian and of the phylogeny of the higher Gastropoda. Zeitschrift H.K. Larson, eds, Proceedings of the Sixth International für zoologische Systematik und Evolutionsforschung, Marine Biological Workshop: The Marine Flora and 23: 15-37. Fauna of Darwin, Northern Territory, Australia, Haszprunar G (1985b). The fine morphology of the Darwin, Australia: Museums and Art Galleries of the osphradial sense organs of the Mollusca. II. Northern Territory and the Australian Marine Sciences Allogastropoda (Architectonicidae, Pyramidellidae). Association, pp. 163-186. Philosophical Transactions of the Royal Society of Jensen KR (1997b). Sacoglossa (Mollusca, Opisthobranchia) London B, 307: 497-505. from the Houtman Abrolhos Island and central Western Haszprunar G (1988). On the origin and evolution of Australia. In: F.E. Wells, ed, Proceedings of the Seventh major gastropod groups, with special reference to the International Marine Biological Workshop: The Marine Streptoneura. Journal of Molluscan Studies, 54: 367- Flora and Fauna of the Houtman Abrolhos Islands, 441. Western Australia, Western Australian Museum, Perth, Hubendick B (1945). Phylogenie und Tiergeographie der pp. 307-333. Siphonariidae zur Kenntnis der Phylogenie in der Jensen KR (1997c). Sacoglossernes systematik, fylogeni og Ordnung Basommatophora und des Ursprungs der evolution (Mollusca, Opisthobranchia). Systematics, Pulmonatengruppe. Zoologiska Bidrag från Uppsala, phylogeny and evolution of the Sacoglossa (Mollusca, 24: 1-126. Opisthobranchia), Vestjydsk Forlag, Vinderup, 94 pp. Jensen KR (1980). Oxynoe azuropunctata n.sp., a new Jensen KR (2003). Distributions, diets and reproduction of sacoglossan from the Florida Keys (Mollusca: Hong Kong Sacoglossa (Mollusca: Opisthobranchia): Opisthobranchia). Journal of Molluscan Studies, 46: a summary of data, 1980-2001. In: B. Morton, ed, 282-292. Perspectives on Marine Environmental Change in Hong Jensen KR (1989). A new species of Cylindrobulla from Kong and Southern China, 1977-2001. Proceedings of Phuket, Thailand, with a discussion of the systematic an International Workshops Reunion Conference, Hong affiliation of the genus. Phuket Marine Biological Kong 2001. Hong Kong University Press, Hong Kong, Center, Research Bulletin, No. 52: 1-11. pp. 347-365. Jensen KR (1993). Sacoglossa (Mollusca, Opisthobranchia) Jensen KR (2009). Sacoglossa (Mollusca: Gastropoda: from Rottnest Island and central Western Australia. Opisthobranchia) from Singapore. Raffles Bulletin of In: FE Wells, DI Walker, H Kirkman, R Lethbridge, Zoology, Supplement 22: 207-223. eds, Proceedings of the Fifth International Marine Jensen KR, Wells FE (1990). Sacoglossa (=Ascoglossa) Biological Workshop: The Marine Flora and Fauna of (Mollusca, Opisthobranchia) from southern Western Rottnest Island, Western Australia. Western Australian Australia. In: F.E. Wells, D.I. Walker, H. Kirkman Museum, Perth, pp. 207-253. and R. Lethbridge, eds, Proceedings of the Third Jensen KR (1996a). Phylogenetic systematics and International Marine Biological Workshop: The Marine classification of the Sacoglossa (Mollusca, Gastropoda, Flora and Fauna of Albany, Western Australia 1, Opisthobranchia). Philosophical Transactions of the Western Australian Museum, Perth, pp. 297-331. Royal Society of London B, 351: 91-122. Jörger KM, Stöger I, Kano Y, Fukuda H, Knebelsberger

190 COMPARATIVE MORPHOLOGY OF THE MANTLE CAVITY ORGANS OF SHELLED SACOGLOSSA, WITH A DISCUSSION OF RELATIONSHIPS WITH OTHER HETEROBRANCHIA

T, Schrödl M (2010). On the origin of Acochlidia Marcus E deB-R, Hughes HPI (1974). Opisthobranch and other enigmatic euthyneuran gastropods, with molluscs from Barbados. Bulletin of Marine Science, implications for the systematics of Heterobranchia. 24: 498-532. BMC Evolutionary Biology, 10: 323. Marcus E, Marcus E (1956). On the tectibranch gastropod Kawaguti S, Yamasu T (1960a). Formation of the adductor Cylindrobulla. Anais da Academia Brasileira de muscles in a bivalved gastropod, Tamanovalva limax. Ciências, 28: 119-128. Biological Journal of Okayama University, 6: 150-159. Marcus E, Marcus E (1960). On Siphonaria hispida. Kawaguti S, Yamasu T (1960b). Electron microscope Boletins da Faculdade de Filosofia da Universidade de study on the adductor muscle of a bivalved gastropod, Sao Paulo, Zoologia, 23: 107-140. Tamanovalva limax. Biological Journal of Okayama Marcus E, Marcus E. (1970). Opisthobranchs from Curaçao University, 6: 61-70. and faunistically related regions. Studies on the Fauna Kawaguti S, Yamasu T (1962). Julia japonica found living of Curaçao and other Caribbean Islands, 33: 1-129. as a bivalved gastropod. Proceedings of the Japan Mazzarelli GF (1892). Ricerche sulla morfologia delle Academy, 38: 284-287. Oxynoeidae. Memoria della Società Italiana delle Klussmann-Kolb A, Dinapoli A, Kuhn K, Streit B, Scienze, 9: 1-33, plates I-III. Albrecht C (2008). From sea to land and beyond – New Mikkelsen PM (1996). The evolutionary relationships of insights into the evolution of euthyneuran Gastropoda Cephalaspidea s.l. (Gastropoda: Opisthobranchia): A (Mollusca). BMC Evolutionary Biology, 8: 57. phylogenetic analysis. Malacologia, 37: 375-442. Köhler A (1893). Beiträge zur Anatomie der Gatting Mikkelsen PM (1998). Cylindrobulla and Ascobulla in Siphonaria. Zoologischer Jahrbüchern. Abteilung für the western Atlantic (Gastropoda, Opisthobranchia, Anatomie und Ontogenie der Thiere, 7(1): 1-92, plates Sacoglossa): Systematic review, description of a new 1-6. species, and phylogenetic reanalysis. Zoologica Scripta, Le Renard J, Sabelli B, Taviani M (1996). On Candina 27: 49-71. (Sacoglossa: Juliidae), a new fossil genus of bivalved Morton JE (1972). The form and functioning of the pallial gastropods. Journal of Paleontology, 70(2): 230-235. organs in the opisthobranch Akera bullata with a Lindberg DR, Ponder WF (2001). The influence of discussion on the nature of the gill in the Notaspidea classification on the evolutionary interpretation and other tectibranchs. Veliger, 14: 337-349. ofstructure - a re-evaluation of the evolution of the Morton JE (1988). The pallial cavity. In: ER Trueman, MR pallial cavity of gastropod molluscs. Organisms Clarke, eds, The Mollusca. Vol. 11. Form and Function, Diversity and Evolution, 1: 273-299. Academic Press, pp. 253-286. Maeda T, Kajita T, Maruyama T, Hirano Y (2010). Molecular Ponder WF (1986). Glacidorbidae (Glacidorbacea: phylogeny of the Sacoglossa, with a discussion of gain Basommatophora), a new family and superfamily of and loss of kleptoplasty in the evolution of the group. operculate freshwater gastropods. Zoological Journal Biological Bulletin, 219: 17-26. of the Linnean Society, 87: 53-83. Malaquias MAE, Mackenzie-Dodds J, Bouchet P, Gosliner Ponder WF (1987). The anatomy and relationships of T, Reid DG (2009). A molecular phylogeny of the the pyramidellacean limpet Amathina tricarinata Cephalaspidea sensu lato (Gastropoda: Euthyneura): (Mollusca: Gastropoda). Asian Marine Biology, 4: 1-34. Architectibranchia redefined and Runcinacea Ponder WF (1990a). The anatomy and relationships of the reinstated. Zoologica Scripta, 38: 23-41. Orbitestellidae (Gastropoda: Heterobranchia). Journal Marcus, E. 1957. On Opisthobranchia from Brazil (2). of Molluscan Studies, 56: 515-532. Journal of the Linnean Society, Zoology, 43: 390-486. Ponder WF (1990b). The anatomy and relationships of Marcus E deB-R (1982). Systematics of the genera of the a marine valvatoidean (Gastropoda: Heterobranchia). order Ascoglossa (Gastropoda). Journal of Molluscan Journal of Molluscan Studies, 56: 533-555. Studies, Supplement 10: 1-31. Ponder WF (1991). Marine valvatoidean Gastropods -

191 Kathe R. Jensen

implications for early heterobranch phylogeny. Journal pp. 383-406. of Molluscan Studies, 57: 21-32. Wägele H, Vonnemann V, Wägele JW (2003). Toward a Ponder WF, Lindberg DR (1997). Towards a phylogeny of phylogeny of the Opisthobranchia. In: C Lydeard, gastropod molluscs: an analysis using morphological D Lindberg, eds, Molecular Systematics and characters. Zoological Journal of the Linnean Society, Phylogeography of Mollusks. Smithsonian Institution 119: 83-265. Press, Washington, DC, pp. 185-228. Rudman WB (1972a). A study of the anatomy of Pupa and Warén A, Bouchet P (2009). New gastropods from deep-sea Maxacteon (Acteonidae, Opisthobranchia), with an hydrocarbon seeps off West Africa. Deep-Sea Research account of the breeding cycle of Pupa kirki. Journal of II, 56: 2326-2349. Natural History, 6: 603-619. Yamasu T (1968). Anatomy and histology of a bivalved Rudman WB (1972b). The anatomy of the opisthobranch gastropod, Julia japonica. Biological Journal of genus Hydatina and the functioning of the mantle cavity Okayama University, 14: 35-53. and alimentary canal. Zoological Journal of the Linnean Yonge CM (1952). The mantle cavity in Siphonaria Society, 51: 121-139. alternata Say. Proceedings of the Malacological Society Rudman WB (1972c). Studies on the primitive opisthobranch of London, 29: 190-199. genera Bullina Férussac and Micromelo Pilsbry. Zoological Journal of the Linnean Society, 51: 105-119. Schmekel L (1985). Aspects of evolution within the opisthobranchs. In: ER Trueman, MR Clarke, eds, The Mollusca, Vol 10. Evolution, Academic Press, pp. 221-267. Schmekel L, Portmann A. (1982). Opisthobranchia des Mittelmeeres. Nudibranchia und Saccoglossa. Springer, Berlin - New York. Thollesson M (1999). Phylogenetic analysis of Euthyneura (Gastropoda) by means of the 16S rRNA gene: the use of a ’fast’ gene for ’higher-level’ phylogenies. Proceedings of the Royal Society of London, Series B, 266: 75-83. Villier CJ de, Hodgson AN 1987. The structure of the secondary gills of Siphonaria capensis (Gastropoda: Pulmonata). Journal of Molluscan Studies, 53: 129-138. Vonnemann V, Schrödl M, Klussmann-Kolb A, Wägele H (2005). Reconstruction of the phylogeny of the Opisthobranchia (Mollusca: Gastropoda) by means of 18S and 28S rRNA gene sequences. Journal of Molluscan Studies, 71: 113-125. Wägele H, Klussmann-Kolb A (2005). Opisthobranchia (Mollusca, Gastropoda) – more than just slimy slugs. Shell reduction and its implications on defence and foraging. Frontiers in Zoology, 2: 3. Wägele H, Klussmann-Kolb A, Vonnemann V, Medina M (2008). Heterobranchia I: the Opisthobranchia. In: WF Ponder, DR Lindberg, eds, Phylogeny and evolution of the Mollusca. University of California Press, Berkely,

192