The inheritance of morphological variation in Pileolaria pseudomilitaris (Polychaeta: Spirorbidae)

The genetic control of morphological variation (expressed as heritability) was examined by means of laboratory culture in Pileolaria pseudomilitaris. Fourteen of 22 traits examined were shown to have an appreciable genetic component, after an analysis of variance among groups of full siblings. The range of variability for several traits is as large within a single sibling group as the difference between described species in the family.
Comparisons among samples of P. pseudomilitaris from two habitats revealed no consistent morphological dillerences. A similar comparison between P. pseudomilitaris and its nearest congener, I', potswaldi , indicated significant differences for 15 of 22 traits, although ranges overlapped for all bin two of these.     

Opposed bands of cilia in the nonfeeding larvae of the serpulid annelid Salmacina tribranchiata

The nonfeeding planktonic larvae of marine invertebrates typically lack larval feeding structures. One puzzling exception to this generalization is the annelid clade Sabellidae, in which nonfeeding larvae possess ciliary bands (specifically, food groove and metatroch) that, to the best of our knowledge, have no function other than in feeding. Nishi and Yamasu (1992b, Bulletin of the College of Sciences, University of the Ryukyus, 54 , 107–121) published a scanning electron micrograph showing that nonfeeding larvae of the serpulid annelid Salmacina dysteri also possess food groove and metatrochal cilia. Here I demonstrate that nonfeeding larvae of Salmacina tribranchiata also bear ciliary bands identifiable as food groove and metatroch by position. High‐speed video of ciliary beat patterns shows that, together with the prototrochal cilia, these bands function in an opposed band system. The presence of feeding structures in nonfeeding annelid larvae is thus more widely distributed than previously recognized. The presence of feeding structures may make evolutionary transitions to planktotrophy more likely, and may underlie an inferred origin of larval feeding in the common ancestor of one of the two major clades of serpulid annelids, Serpulinae.     

Soft‐bottom tube worms: from irregular to programmed shell growth

Like other secondary soft‐bottom dwellers, serpulid and sabellid tube worms used particular strategies in order to cope with their earlier loss of mobility. This is expressed by the transition from irregular to genomically programmed morphologies of their calcareous shells that guarantee a stable horizontal resting position. In contrast to permanent recliners, however, this attitude was probably only the starting position for active resurrection after the muddy tail of storm sediments had settled on top of the displaced animal.     

Development,morphology and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774) (Polychaeta: Sabellida: Fabriciinae)

Randel, N. and Bick, A. 2011. Development, morphology and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774) (Polychaeta: Sabellida: Fabriciinae). —Acta Zoologica (Stockholm) 93 : 409–421. Sabellidae and Serpulidae are well‐known tube‐building polychaetes with a distinctive and often spectacularly colourful branchial crown. Morphological investigations suggest that these taxa form the monophyletic clade Sabellida, with the adelphotaxa Sabellidae and Serpulidae, but the relationship between these taxa remains ambiguous. Molecular investigations have indicated that the Fabriciinae, major taxon of Sabellidae, belongs to Serpulidae, thereby making Sabellidae paraphyletic; however, morphological characters are absent to support this result. We investigate the development, anatomy and ultrastructure of the branchial crown of Fabricia stellaris (Müller, 1774), describing morphological characteristics useful not only for constructing morphological phylogenies but also for understanding the evolution of the branchial crown. The morphology of the radioles and pinnules does not differ from each other. The supporting tissue of the branchial crown consists of myoepithelial cells and a solid extracellular matrix (ECM). Both ciliated and non‐ciliated cells form the epidermal layer; ciliated cells shape the food groove. Most important is the result that radioles and pinnules within Sabellida may not be homologous, because the morphology and the branching of radioles and pinnules are completely different between Sabellinae, Fabriciinae and Serpulidae. The terms ‘primary branch’ for radioles and ‘secondary branch’ for pinnules are proposed for Fabriciinae. The phylogeny of the Sabellida is discussed.     

The worm re-turns: hiding behavior of a tube-dwelling marine polychaete, Serpula vermicularis

The polychaete worm Serpula vermicularis (Serpulidae) filterfeeds at the mouth of its calcareous tube, but retreats intothe tube when startled by mechanical stimuli likely to be associatedwith predators. While in its tube, a worm is safe but cannotfeed. Thus, hiding has a lost-opportunity cost. We show thatthis cost can be substantial, given that food in the naturalhabitat appears in pulses, and good feeding conditions may notlast long or recur frequently. We expect that a worm's hidingtime will be sensitive to the lost-opportunity cost, and wepresent data from a series of experiments that support thisprediction. The worms seem able to track relatively short-termchanges in food availability, and some evidence suggests thatthey assess food availability on a relative basis, comparingcurrent feeding conditions to those recently experienced. Hidingand other types of cryptic behavior are common antipredatortactics, and animals may commonly adjust the durations of suchbehaviors to current benefits and costs (including lost opportunity),as they perceive them     

Polymorphism in Pomatoceros

Allelic variation at 13 sites for the intertidal Pomatoceros lamarckii (Quatrefages) and at six sites for the sublittoral P. triqueter (L.) in North-West Europe, when examined at 19 metabolic enzyme loci, showed significant differences between sites in the frequencies of the various enzyme morphs. There was no readily interpretable geographic or environmental trend. The Hardy-Weinberg equilibrium was maintained at almost all loci and all sites. The genetic distance between populations was very small in comparison with the difference between the two species.
Colour morphs of P. triqueter showed a clear latitudinal cline with blue and brown morphs predominating at more northerly latitudes, and grey, orange and red morphs at more southerly latitudes.
Interlocality variations in allele frequency, though statistically significant, were never sufficient to alter the order of frequency of the two or three commonest alleles, so that the frequency of all but rare alleles showed a consensus throughout the ranges studied for each species. Accounting for local genetic patchiness in gene frequencies in species with pelagic larvae raises problems if the alleles are selectively neutral; accounting for wide geographic uniformity raises problems if alleles are selected for or against by environmental factors.     

Microscopic evidence of serpulid affinities of the problematic fossil tube ‘Serpula’ etalensis from the Lower Jurassic of Germany

Tube structure, ultrastructure and mineralogy support serpulid affinities of the problematic worm fossil ‘Serpula’etalensis from the Lower Jurassic of Germany. The original tube mineralogy of ‘Serpula’etalensis is purely aragonitic and is preserved in Upper Pliensbachian specimens from eastern Germany. ‘Serpula’etalensis represent the earliest record of aragonitic mineralogy for serpulids. The tube is formed of irregularly oriented prismatic crystals that are 3–6 µm in length and 0.5–1.0 µm in diameter. Calcitic specimens of ‘Serpula’etalensis from Upper Sinemurian of southwestern Germany were recrystallized during the diagenesis and lack the original tube ultrastructure.     

On the unique isotropic aragonitic tube microstructure of some serpulids (Polychaeta,Annelida)

A Scanning electron microscopy study of peculiar serpulid tube microstructures was carried out to determine whether this structure is unique to serpulids and to understand its formation and evolution. The isotropic aragonitic tube microstructure of some serpulids, termed spherulitic irregularly oriented prismatic structure (SIOP), is unknown in other animal skeletons. After nucleation, initial spherulitic prismatic aragonite crystals presumably grow in length and width at one end, collide with the surrounding growing crystal fans, and then continue intertwined growth until the secreted carbonate‐charged mucus is completely crystallized. Spherulitic irregularly oriented prismati structure presumably evolved either from the IOP or homogeneous rounded crystal microstructures. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

A scanning electron microscopic study of larval development in the marine polychaete,Galeolaria caespitosa Lamarck (Serpulidae)

Summary Gametes and developing larvae of the polychaete Galeolaria caespitosa were examined by scanning electron microscopy. The sperm display a primitive morphology. When treated with 0.33 M CaCl₂, they release a branched acrosomal process. At spawning, the polygonal oocytes have a granular surface made up of spherules and the tips of microvilli. The oocyte coat develops a ridged appearance as the oocyte rounds up. At fertilization, the microvilli are withdrawn from the coat surface. Microvilli again appear on the coat surface during the trochophore stage, but the egg coat appears to be retained as the larval cuticle until the demersal stage. The surface of the larva now shows many microvilli. Details of the organization of several ciliary structures are clarified. Moreover, the present study shows rapid, sequential development of paired setal sacs, with the most anterior pair appearing first.     

深圳宋卡湖根管虫(多毛纲:龙介虫科)个体发育的初步观察

对分布于中国深圳的宋卡湖根管虫Ficopomatus talehsapensis Pillai,2008进行了实验观察.结果表明:1)雌雄异体,精子或卵从鳃冠基部喷射至水中,体外受精,繁殖力强,受精后约0.8h开始卵裂,生活史经历早期胚胎发育、担轮幼虫、后担轮幼虫、游毛幼虫、后游毛幼虫、刚节幼体及成虫;2)鳃丝具呼吸、感觉、滤食功能,以单细胞藻类和有机碎屑为食;3)担轮幼虫至成体均具眼点,但视觉功能退化;4)对水环境的适应能力极强.讨论了根管虫对生境水质的影响.