Diagnosis emend. Gender feminine. Prostomium incised, developed into two frontal lobes or weak horns; caruncle present or absent; occipital tentacle absent. Peristomial wings absent. Notopodia of setigers 2–4 with fascicles of heavy spines. Anterior neuropodial spines present. Dorsal branchiae from setiger 2; ventral branchiae from an anterior segment, branchiae closely associated with parapodial lamellae, continuing to posterior end. Setiger 1 reduced, with notopodia reduced to single lamellae lacking notosetae; notopodia and neuropodia with capillaries and hooded hooks. Pygidium simple, conical, lacking cirri.
Table 3 charts differences between the three species of Lindaspio recognized here.
From a morphological point of view, it is rather clear that these three species are very similar, even if we could consider the minute differences are significant. For example, L. dibranchiata and L. sebastiena have in common their width and the number of anterior heavy spines; L. southwardorum and L. sebastiena share the same number of the heavy spines and the level of appearance of the first neuro-hooks. However, differences in depth and geographical location at which L. sebastiena has been collected compared with the two other Lindaspio species are striking, and do not permit synonymy with either of them.
Another point to consider is the large and unusual size of the branchiae, chiefly the ventral ones, in Lindaspio species. In a recent paper, Hourdez et al. (1998) observed that polychaetes from hydrothermal vents (alvinellids and polynoids) and from cold seeps (orbiniids) exhibit increased specific gill surface area which could be anatomical and physiological adaptations to hypoxyia. This observation could be applied to spionids such as Lindaspio.
Another important point is the felting present on the branchiae of L. sebastiena which could be correlated with the environment, organically enriched in hydrocarbons and barium. Such a felting could represent an analogy with the bacterial accumulation on the posterior part of the body of Alvinella caudata Desbruyères and Laubier, 1986. It is of some interest to recall that L. sebastiena was collected together with an undescribed species of Vesicomyidae, Vesicomyarum sp. (Cosel and Salas, in preparation), and that various Vesicomyids are associated with symbiotic sulpho-oxidizing bacteria.