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The morphology of the rhynchocoel blood vessel was studied in 26 specimens representing 14 species of the family Cephalotrichidae. In eight specimens the vascular system could not be traced because of their small size, poor fixation, or contraction during fixation. In the other 18 specimens, a short mid-dorsal rhynchocoel vessel was found. In Cephalothrix adriatica, C. hongkongiensis, C. kefersteini, C. oestrymnica, C. orientalis, C. rufifrons, C. cf. fasciculus and C. cf. simula, the mid-dorsal rhynchocoel vessel penetrates the dorsal side of the proboscis insertion, and extends backward abutting the mid-dorsal rhynchocoel wall (Type A). In C. filiformis sensu Iwata (1954), the vessel is pendant in the rhynchocoel above the proboscis (Type B). In C. filiformis s.str., the vessel runs in the proboscis wall, after passing through the proboscis insertion (Type C). Morphology of the rhynchocoelic vessel might have taxonomic significance in cephalothrichids. [ABSTRACT FROM AUTHOR]

A survey of the nemertean fauna along the Swedish west coast found specimens of 20 genera and 32 species, of which one genus and species is new to science (Tetraneuronemertes lovgreni gen. et sp. n.). The proportions of the three taxa Hoplonemertea, Heteronemertea, and Palaeonemertea are 34, 55, and 11%, respectively, with respect to specimen numbers, and the proportions for species within these taxa are 53, 31 and 16%, respectively. The most common species encountered during the survey were the heteronemerteans Lineus bilineatus, Micrura fasciolata, and Micrura purpurea, the hoplonemertean Nipponnemertes pulcher, and the palaeonemertean Cephalothrix rufifrons. [ABSTRACT FROM AUTHOR]

The ultrastructure of the pseudocnidae (filament‐core rhabdoids) of the palaeonemerteans Cephalothrix cf. rufifrons and Carinomella lactea is described and the phylogenetic utility of these organelles evaluated. Pseudocnidae of Cephalothrix cf. rufifrons are clavate structures, measuring 3–5 µm in length with a bulbous lateral process present near their midregion, whereas those of Carinomella lactea are rod‐shaped structures, measuring 2–3 µm in length and lack a lateral process. In both species, these structures exhibit a somewhat electron‐lucent cortex, an electron‐dense medulla and a distinct filament‐like core, extending from the apex of the pseudocnida toward its base. The pseudocnidae are situated within pseudocnida‐forming cells that constitute a portion of the glandular proboscis epithelium and are oriented parallel to the apical basal axis of the cell. No evidence of core extrusion was observed in these species. Comparative structural analyses confirm that these secretory granules are neither rhabdite homologues nor cleptocnidae. Position and ultrastructure of palaeonemertan pseudocnidae support the hypothesis that they are homologous to those of heteronemerteans, and pseudocnidae are interpreted as a provisional synapomorphy of the Anopla, as suggested in previous studies. However, recent molecular phylogenies of nemerteans do not support anoplan monophyly, necessitating alternative interpretations of pseudocnida evolution, namely, that these structures were present in the nemertean common ancestor and subsequently lost in the hoplonemerteans and Carinoma or that they evolved independently in the Pilidiophora and a Cephalothricidae + Tubulanidae clade. A rigorous explanation of pseudocnida evolution awaits a simultaneous analysis of molecular and morphological characters inclusive of pseudocnidae. [ABSTRACT FROM AUTHOR]

Specimens of Tubulanus riceae new species (Nemertea: Palaeonemertea) were collected from a Phragmatopoma worm reef in the surf zone at Fort Pierce (Florida, USA) and from sublittoral rubble at Carrie Bow Cay (Belize) and Bocas del Toro (Panama). They have well‐developed lateral sensory organs, form a cellophane‐like tube and appear to have ocelli‐like structures. The latter, if confirmed as ocelli, would be the first reported for a tubulanid. The new species is characterized by a unique color pattern, resembling that of Tubulanus rhabdotus , but it is distinctive in its milky‐tan ground color with annular bands of brown pigment bounded by white margins and in having up to six to eight dorsal, longitudinal, but broken, reflective white stripes. [ABSTRACT FROM AUTHOR]