Brian Morton

The functional morphology of Bentholyonsia teramachii (Bivalvia: Lyonsiellidae): clues to the origin of predation in the deep water Anomalodesmata

Bentholyonsia teramachii has hitherto been described from Japan, but a conspecific specimen is herein recorded from Western Australian shelf waters at a depth of ∼100 m. Hitherto placed in the Lyonsiidae, B. teramachii is herein relocated in the Lyonsiellidae, alongside a second genus –Lyonsiella. Features of the anatomy of Bentholyonsiateramachii, including highly sensory siphons, reduced ctenidia unable to collect and transport particulate food, non-sorting labial palps, and a simplified Type II stomach and muscular gut all suggest that the species is a predator like Lyonsiella formosa. Other features of the anatomy, such as pallial taenioid muscles, radial mantle glands, and the structure of the ctenidia all point to a link between B. teramachii and the Lyonsiellidae and thus with the Verticordiidae and Parilimyidae and, therefore, with some of the oldest anomalodesmatans, the Pholadomyidae. In the possession by B. teramachii of a unique pair of antero-dorsal suspensory muscles, the link with fossil pholadomyoideans is reinforced. Bentholyonsia thus represents another genus of predatory bivalve, not only expanding our view of the prevalence of this feeding mode in the deep sea by this class but also helping us show how it evolved, in anatomical terms, from a suspension- (or deposit-) feeding ancestor.

The biology and functional morphology of Nipponoclava gigantea : clues to the evolution of tube dwelling in the Penicillidae (Bivalvia: Anomalodesmata: Clavagelloidea)

Nipponoclava gigantea is restricted to the tropical Western Pacific waters of southern Japan at depths of between 5 and 70 m and lives in coarse sand and gravel. In many respects, N. gigantea appears to be similar to other endobenthic penicillids in that there is a true shell, the margins of which, via the intermediary of a narrow ‘saddle’, are united with an adventitious tube. This has a large watering pot anteriorly and pleated ruffles, representing either growth or repair events, posteriorly. Nipponoclava gigantea differs from other penicillids, however, in that its true shell is large, i.e. ˜20 mm high as compared to 2–3 mm, and the angle of valve splay is ˜80° as opposed to 180°. Internally the shell has a wide pallial line and shallow pallial sinus and there are anterior adductor muscle scars. There are possibly posterior adductor muscle scars also. These are not present in the adult animal, however, although the anterior adductor is. Also present are paired anterior and (possibly) posterior pedal retractor muscles, the latter having a nervous union with the visceral ganglia to create simple stretch or tonus proprioreceptors. It is argued that N. gigantea provides clues about how the tube-dwelling lifestyle has evolved in the various taxa of the Penicillidae. It is suggested that through a process of heterochrony, in which the animal produces its adventitious tube at progressively earlier and earlier developmental stages, the true shell has become actually and relatively smaller and smaller and, hence, more splayed in more derived penicillids. Nipponoclava gigantea is thus an important link between an hypothetical lyonsiid ancestor and the more specialized penicillids and helps us to understand the adaptive radiation of this group of tube-dwelling bivalves.

A new species and first record of the endobenthic clavagellid Stirpulina (Bivalvia: Anomalodesmata) from the late Eocene of southern Western Australia

Stirpulina pallinupense sp. nov. (Clavagellidae) is described from the late Eocene Pallinup Formation of the Bremer Basin, southern Western Australia. The Tehyan Stirpulina is hitherto unrecorded from the southern hemisphere. During the late Eocene, elements of a Tethyan — Southwest Pacific fauna and other, more cosmopolitan, groups of molluscs extended their ranges to southern Australia, joining endemic species to form the distinctive, blended, fauna of the Pallinip Formation.

[A New Genus and Species of Barnacle (Cirripedia, Pedunculata) Commensal with Arca Navicularis Bruguière, 1789 (Mollusca, Bivalvia, Arcoidea) from Queensland, Australia, with an Analysis of the Relationship, A New Genus and Species of Barnacle (Cirripedia, Pedunculata) Commensal with Arca Navicularis Bruguière, 1789 (Mollusca, Bivalvia, Arcoidea) from Queensland, Australia, with an Analysis of the Relationship]

[A previously undescribed heteralepadomorph genus and species is recorded as attached to the inside of the shell of the living epibenthic bivalve Arca navicularis, dredged from the waters of Moreton Bay, Queensland. The combination of anatomical features exhibited by the barnacle match some of the characteristics of Malacolepas. However, several characters are distinctive and a new genus and species is, therefore, proposed and named Arcalepas brucei sp. nov. Occurring in groups of up to ten individuals inside each host, Arcalepas brucei sp. nov. clearly benefits from the protection afforded by inhabiting the living bivalve and the flow of oxygenated water created by Arca navicularis. However, the barnacle also exploits the ciliary rejection currents of its host and appears to collect the pseudofaeces the bivalve removes from its mantle cavity along the rejectory tracts that internally occupy each ventral mantle margin. It does this by expanding its cirral net into the rejectory tracts and plucking up the unwanted particles collected by the suspension feeding activities of the bivalve. The barnacles relationship with its host is thus best described as commensal. This is the first record of such an association from Australian waters. Eine bisher unbeschriebene Gattung und Art einer heteralepadomorphen Seepocke wird hier von der Schaleninnenseite einer lebenden epibenthischen Muschel (Arca navicularis) von Moreton Bay, Queensland (Australien) beschrieben. Die Kombination einiger anatomischer Merkmale dieser Seepocke stimmt mit Besonderheiten von Malacolepas uberein. Allerdings besitzt die neue Art charakteristische Merkmale, die die Beschreibung einer neuen Gattung rechtfertigen. In Gruppen bis zu zehn Individuen besiedelt Arcalepas brucei gen. und sp. nov. ihren Wirt, in dem sie nicht nur Schutz findet, sondern auch vom Strom sauerstoffreichen Wassers profitiert, der von Arca navicularis erzeugt wird. Die Seepocke nutzt die dem Abtransport des Abfalls dienenden Wimperstrome des Wirtes, indem sie ihnen Pseudofaeces entnimmt, die die Muschel aus der Mantelhohle entlang von Wimperbahnen entfernt, die innen auf den ventralen Mantelrandern verlaufen. In diese Wimperbahnen halt die Seepocke ihre Zirren und bedient sich an dem von der Muschel verschmahten Material, das wahrend ihrer Nahrungsaufnahme ausgesondert wird. Die Beziehung zwischen Seepocke und Muschel ist daher am besten als kommensal zu bezeichnen und ist bis jetzt die einzige Beziehung dieser Art, die von australischen Gewassern bekannt ist., A previously undescribed heteralepadomorph genus and species is recorded as attached to the inside of the shell of the living epibenthic bivalve Arca navicularis, dredged from the waters of Moreton Bay, Queensland. The combination of anatomical features exhibited by the barnacle match some of the characteristics of Malacolepas. However, several characters are distinctive and a new genus and species is, therefore, proposed and named Arcalepas brucei sp. nov. Occurring in groups of up to ten individuals inside each host, Arcalepas brucei sp. nov. clearly benefits from the protection afforded by inhabiting the living bivalve and the flow of oxygenated water created by Arca navicularis. However, the barnacle also exploits the ciliary rejection currents of its host and appears to collect the pseudofaeces the bivalve removes from its mantle cavity along the rejectory tracts that internally occupy each ventral mantle margin. It does this by expanding its cirral net into the rejectory tracts and plucking up the unwanted particles collected by the suspension feeding activities of the bivalve. The barnacles relationship with its host is thus best described as commensal. This is the first record of such an association from Australian waters. Eine bisher unbeschriebene Gattung und Art einer heteralepadomorphen Seepocke wird hier von der Schaleninnenseite einer lebenden epibenthischen Muschel (Arca navicularis) von Moreton Bay, Queensland (Australien) beschrieben. Die Kombination einiger anatomischer Merkmale dieser Seepocke stimmt mit Besonderheiten von Malacolepas uberein. Allerdings besitzt die neue Art charakteristische Merkmale, die die Beschreibung einer neuen Gattung rechtfertigen. In Gruppen bis zu zehn Individuen besiedelt Arcalepas brucei gen. und sp. nov. ihren Wirt, in dem sie nicht nur Schutz findet, sondern auch vom Strom sauerstoffreichen Wassers profitiert, der von Arca navicularis erzeugt wird. Die Seepocke nutzt die dem Abtransport des Abfalls dienenden Wimperstrome des Wirtes, indem sie ihnen Pseudofaeces entnimmt, die die Muschel aus der Mantelhohle entlang von Wimperbahnen entfernt, die innen auf den ventralen Mantelrandern verlaufen. In diese Wimperbahnen halt die Seepocke ihre Zirren und bedient sich an dem von der Muschel verschmahten Material, das wahrend ihrer Nahrungsaufnahme ausgesondert wird. Die Beziehung zwischen Seepocke und Muschel ist daher am besten als kommensal zu bezeichnen und ist bis jetzt die einzige Beziehung dieser Art, die von australischen Gewassern bekannt ist.]