The genus Perkinsiana (Polychaeta, Sabellidae) from Antarctica, with descriptions of the new species P. milae and P. borsibrunoi

Perkinsiana antarctica (Kinberg, 1867) and P. littoralis (Hartman, 1967) are redescribed from holo- and topotypes. Two new species, P. milae and P. borsibrunoi , are described from the Ross Sea (Antarctica) and compared with other species of the genus. Records of P. antarctica are numerous, but re-examination indicates that many of these represent misidentifications: the species may have a distribution limited to subantarctic areas.     

Contributions to the taxonomy of Sabellidae (Polychaeta)

The genus Potamilla Malmgren is particularly characterized by dorsal lips which lack any radiolar midrib; Pseudopotamilla Bush by compound radiolar eyes, dorsal collar lappets and flanges alongside the bases of the most dorsal radioles; Demonax Kinberg by a wide dorsal collar gap and companion setae with big heads and narrow blades; and Potamethus Chamberlin by an elongated first segment, enlarged ventral sacs, very long shafts to the thoracic uncini, and inferior abdominal setae much shorter than the superior ones. Perkinsiana gen. nov . lacks most of these characters, but the type species 'Potamilla' rubra Langerhans is remarkable in having red blood. It bores into limestone abundantly off S Wales and is here redescribed. Oriopsis hynensis sp. nov . from SW Ireland has a smooth collar set low on the first segment, with its ventral margin entire and free from the apex of the peristome. The new name Demonax langerhansi is proposed for Sabella (Potamilla) incerta Langerhans non Demonax incertus Kinberg.     

A revision of Sabella, Bispira and Stylomma (Polychaeta: Sabellidae)

Sabella is rediagnosed to include only species that have spiralled fascicles of abdominal chaetae, first thoracic shield with straight anterior border and radioles that lack composite eyes and flanges. Spirographis spallanzanii is synonymous with Sabella penicillus . The type of the genus is discussed and a neotype designated. The only other species retained in Sabella are S. pavonina and S. discifera ( = Branchiomma linaresi , once misplaced in Megalomma , but abdominal fascicles of Megalomma form transverse rows). Most species formerly placed in Sabella are transferred to Bispira , having C-shaped fascicles of abdominal chaetae, first thoracic shield with a 'W-shaped anterior border and, in most species, radioles with paired composite eyes and flanges. Bispira , with B. volutacornis as the type species, is rediagnosed to include B. crassicomis, B. fabricii, B. melanostigma, B. tricyclia, B. viola, B. manicata, B. poricfera, B, mariae, B. elegans, B. brunnea, B. guinensis, B. secusolutus, B. wireni, B. oatesiana, B. spirobranchia, B. pacifica, B. monroi , and B. turneri , many of which are described fully for the first time. Only five of these form bispiral crowns (bispirality is useful only specifically and occurs in other genera) and one, B. tricyclia , has a unispiral crown. Sabella palmata Quatrefages, the type of Stylomma is redescribed and its synonyms discussed. This genus has abdominal fascicles like those of Bispira , but radiolar eyes like those of Megalomma . The relative advantages of chaetal arrangement and eye position are discussed.     

Revision of the Fabriciinae genus Fabriciola Friedrich, 1939 (Polychaeta: Sabellidae)

The Sabellidae polychaete genus Fabriciola Friedrich is revised as a result of examination of as much of the type material as possible. The type species for the genus has been confused. The earliest designation appears to be Fabricia (Manayunkia) spongicola Southern, 1921, by Ushakov [ Akad. Nauk. SSSR, Opredeliteli po Faune SSSR 56: 1–445 (1955)], whereas subsequent works have incorrectly referred to Manayunkia pacifica Annenkova, 1934, as the type species. The following species are redescribed: Fabriciola baltica Friedrich, 1939, F. berkeleyi Banse, 1956, F. ghardaqa Banse, 1959 a . A new species, F. mediaseta, is described. A neotype is designated for F . baltica. Existence of the type material of F. spongicola (Southern), F. pacifica (Annenkova), and F. tonerella Banse, 1959 b is unknown, but these species are discussed in relation to species examined.     

Two new species of an atypical group of Pseudobranchiomma Jones (Polychaeta: Sabellidae)

The genus Pseudobranchiomma Jones, 1962 can be divided into three groups: (A) those with paired serrated flanges along all or most of the crown radioles, as in the type species P. emersoni Jones, 1962; (B) those with such flanges only on the distal parts of the radioles; (C) those with flanges reduced or absent (without serrations) as in two new species described here from Florida and Italy. Group C also contains Pseudobranchiomma longa (Kinberg, 1867), P. punctata (Treadwell, 1906) and P. minima (Nogueira & Knight-Jones, 2002). Lists of species (and their synonyms) in the other two groups are given, and scissiparity, thoracic length, chaetal arrangements and types of radiolar eyes are discussed.     

Ultrastructure of spermiogenesis, sperm, and the spermatheca in Terebrasabella heterouncinata (Polychaeta: Sabellidae: Sabellinae)

Abstract. The sabellid polychaete, Terebrasabella heterouncinata, forms burrows in gastropod shells. It is a small, intratubular brooder that breeds semi‐continuously. It has been shown to self‐fertilize, but its reproductive biology suggests that some form of sperm transfer must occur between individuals. To gain an understanding of its fertilization biology, the ultrastructure of spermiogenesis and the sperm in T. heterouncinata was described, and the animal examined for sperm storage structures. Spermiogenesis occurs in clusters of eight spermatids. The mature sperm has an elongate nucleus and a bilaterally symmetrical acrosome with twisted subacrosomal spaces. The midpiece is short, with three crescent‐shaped mitochondria, and forms a tight sheath around the axoneme. A single spermatheca, which opens on the inner ventral part of the crown near the buccal region, is present. It is a simple blind‐ending duct that runs below the ventral nerve cord and is longer than 100 μm. This is the first record of a single spermatheca in Sabellidae. The shape of the sperm and the presence of a spermatheca confirm that individuals of T. heterouncinata produce ent‐aquasperm and would normally cross‐fertilize.     

Factors influencing latitudinal pattern of biodiversity: An example using Sabellidae (Annelida, Polychaeta)

The latitudinal gradient of biodiversity hypothesis was tested utilising the geographical distribution of species taxa belonging to the family Sabellidae (Annelida: Polychaeta), one of the polychaete families studied by only a few specialists around the world. An increase in species richness towards the Tropical region was revealed, with an asymmetric distribution between the two hemispheres. Data show that most of the species were found in Northern latitudes, producing a Northern area much richer than the Southern one. The Atlantic-Mediterranean Region was particularly rich, with the number of species close to those from the Indo-Pacific Region. Mediterranean species richness is discussed in the light of the particular history of the basin, also emphasising the importance of naturalistic studies that have made the Mediterranean marine flora and fauna one of the best known in the world. The existence of extrinsic factors that obscure the real pattern of distributions is hypothesised. Differences found between the two hemispheres could be attributed primarily to the higher number of specialists working in the Boreal Domains, including the Mediterranean area. Global trends produced by some representative genera are also discussed with respect to the distribution of the taxonomic specialists.     

Ultrastructure of the Spermathecae of Parafabricia ventricingulata and Three Species of Oriopsis (Polychaeta: Sabellidae)

Parafabricia ventricingulata females have a pair of spermathecae located in the radiolar crown anterio-dorsal to the buccal opening. The spermathecae have three regions; an entrance, 7 μm across, leading into a ciliated ‘atrium’ that is approximately 50 μm long; a connecting piece, 2–5 μm across and 25 μm long, leading from the ‘atrium’ to the sperm receptacle. The sperm receptacle is heavily pigmented and spherical. The sperm lie in a large mass in the receptacle with no particular orientation. Oriopsis bicoloris females have a pair of unpigmented spermathecae in the collar behind the radiolar crown. Each spermatheca is a simple blind duct 100 μm long, with a lumen 8 μm in diameter. Between 30 and 40 sperm lie in the lumen of each spermatheca. Oriopsis brevicollaris females have a pair of spermathecae located in the radiolar crown above the buccal opening. From the opening, 10 μm across, a blind duct runs for 90 μm. Sperm are stored in the distal region of the duct. Sperm lie along the margins of the duct in close contact with microvilli. Up to 10 sperm were found in each spermatheca. Oriopsis mobilis females have a pair of spermathecae located in the radiolar crown above the buccal opening. The opening, 3 μm across, leads into a blind duct that runs for 30 μm. Sperm are stored in the distal region of the spermathecae where they are embedded in spermathecal cells. Between 10 and 20 sperm were found in each spermatheca. Oriopsis dentata was found not to have spermathecae. The homologies of the spermathecae found within the Sabellinae and Fabriciinae (Sabellidae) and the Spirorbinae (Serpulidae) are discussed, but cannot be resolved on present evidence.     

Further revisions of the Sabellidae subfamilies and cladistic relationships among the Fabriciinae (Annelida: Polychaeta)

Cladistic relationships of the sabellid subfamilies Fabriciinae and Sabellinae are examined in light of recent revisions of fabriciin taxa. The potential placement of Caobangia in the Sabellinae is suggested from an initial analysis of selected fabriciin species and genera. Subsequent cladistic analyses at the family level produced over 1800 cladograms, among which Caobangia is the most plesiomorphic taxon of either the Fabriciinae or Sabellinae. Successive approximations weighting reduced this ambiguity, consistently placing Caobangia in the Sabellinae. Subfamilies are emended on the basis of these results. Cladistic relationships of fabriciin taxa, exclusive of Caobangia , display topological instability among some genera and species. Genera are, however, monophyletic in all topologies. Incorporating ontogenetic data for branching ventral filamentous appendages in Augeneriella reduces ambiguity among genera and suggests alternative transformation series for ventral filamentous appendages.     

The social feather duster worm Bispira brunnea (Polychaeta: Sabellidae): aggregations,morphology and reproduction

The fan worm Bispira brunnea is one of the most attractive sabellid polychaetes from Caribbean coral reef areas and it is exploited for ornamental purposes. An understanding of the structure of its aggregations, morphology and reproductive biology will provide information required to facilitate artificial propagation of this species. Ten aggregations were collected in October 2013, February and March 2014 in the Majahual reef lagoon, Mexican Caribbean. Whole aggregations were examined under light microscopy and scanning electron microscopy and the histology of oogenesis was determined. Aggregations were composed of 24–56 individuals and included juveniles and adults. The adults (5–20?mm) did not display any noticeable form of sexual dimorphism. In B. brunnea both sexual (hermaphroditism or gonochorism) and asexual reproduction occurred at the same time within the population: 92.71% reproduced sexually and 52% by architomy. The buds produced by architomy were inside the parental tube, at three regenerative stages. The sex ratio was 36.75% males, 33.11% females, 22.84% hermaphrodites and 7.28% unknown (gametes not seen). Gametes were distributed in the last thoracic segments and throughout the abdomen. Oogenesis was extra-ovarian, development followed four discrete stages and the oocytes were small and asynchronous (60.97 μm in diameter). Sperm morphology was adapted to external fertilization in the water column. Sequential (protandrous) hermaphroditism is suggested to occur in B. brunnea. The pyramidellid ectosymbiont mollusc Odostomia (Eulimastoma) caniculatum is recorded here for the first time as being associated with a sabellid worm.     

Ultrastructure of spermiogenesis and spermatozoa of four Oriopsis species (Sabellinae, Sabellidae, Polychaeta)

The ultrastructure of sperm from four species of Oriopsis is described. Males of Oriopsis bicoloris produce sperm with an elongate nucleus divided into four rods, connected proximally, and four long mitochondria lying along the nucleus. The axoneme runs in the middle of the nuclear and mitochondria1 rods. Oriopsis brevicollaris males have sperm with an elongate nucleus and long midpiece comprised of four mitochondria wrapped around the axoneme. Males of O. mobilis have sperm with an elongate nucleus and long midpiece similar to that of O. brevicollaris , although the midpiece is much longer. Oriopsis dentata males havc sperm with a flattened head, similar to those of mammals, though the midpiece is simple and the axoneme free. The variability of reproductive mechanisms within the Polychaeta is discussed with reference to the elucidation of the function of various sperm morphologies. The implications for the taxonomy and systematics of Oriopsis , and the Sabellidae as a whole, are also discussed. It is concluded that Oriopsis is not monophyletic and examination of reproductive structures in other small sabellids is required. Study on reproduction in the type species, O. armandi , is needed to establish the reproductive method of Oriopsis and so allow revision of this genus.     

Fine Structure of the Phaosomous Photoreceptor in the Larvae of Polydora ligni Webster (Polychaeta: Spionidae)

Niilonen, T. 1980. Fine structure of the phaosomous photoreceptor in the larvae of Polydora ligni Webster (Polychaeta: Spionidae). (Institute of Comparative Anatomy, Copenhagen, Denmark.) — Acta zool. (Stockh.) 61(3): 183–190. Phaosomes are described in detail for the first time from the Polychaeta. They were only found in the larvae, whereas serial sections of one sexually mature adult did not reveal any. The photoreceptors of the phaosomous type are placed between the medial and lateral pigmentcup eyes. The distal part of the cell is in direct contact with the epidermal surface, whereas the proximal part rests on a basement membrane. The largest diameter of the spherical cell is 10 μm. In the area immediately around the phaosome very few pigment-granules are found. The body of the phaosome is dominated by the visual vacuole, which is totally occluded by numerous intertwining microvilli. The length of the microvilli is at least 5 μm. The cytoplasm around the visual vacuole is restricted to a narrow bordering zone. A presumed chemoreceptor is found in close association with the phaosome.     

Histochemical and ultrastructural analysis of the epidermal gland cells of Branchiomma luctuosum (Polychaeta, Sabellidae)

Abstract. This histochemical and ultrastructural study describes the epidermal gland cells of a tubicolous polychaete, Branchiomma luctuosum . The histochemistry was carried out using standard techniques and FITC-labelled lectins. Four types of secretory cells were identified in two categories: orthochromatic cells (Type 1) and metachromatic cells (Types 2, 3, and 4). The secretory product of the Type-1 orthochromatic cells contains neutral glycoproteins with Galβ1,3GalNAc residues. Metachromatic cells produce acidic, mainly sulfated, glycoconjugates with Galβ1,3GalNAc residues (Type 2) or glucosidic and/or mannosidic residues (Types 3 and 4). In sialylated chains, terminal sialic acid is bound to the penultimate GalNAc and Galβ1,3GalNAc residues. The complex composition of the mucus produced by epidermal gland cells of B. luctuosum may be correlated with its different functions. Ultrastructural studies of the epidermal gland cells showed differing morphology, and the presence in the gland cells of Types 3 and 4 of a funnel-shaped structure for the extrusion of the secretory material.     

Genetic Structure of PILEOLARIA PSEUDOMILITARIS (Polychaeta: Spirorbidae)

The genetic structure of Pileolaria pseudomilitaris was studied by means of gene-diversity analysis of allozyme frequencies. At an esterase locus, most of the gene diversity was due to subdivision of the population into colonies and subpopulations separated by less than 100 meters. Gene frequencies at a phosphoglucose isomerase locus were similar over many kilometers, but differed between two habitat types. Differences between colonies are attributed to drift and founder effect; similarities over greater distances are attributed to similar selection pressures. A mathematical appendix details the method of gene diversity analysis for a multi-leveled, hierarchically subdivided population.     

The effect of diet and live host presence on the growth and reproduction of Terebrasabella heterouncinata (Polychaeta: Sabellidae)

Summary

The effect of diet type and the presence or absence of a live host on the growth and production of eggs and larvae by Terebrasabella heterouncinata were quantified. Diet was shown not to have a significant effect on the time in which the worms on live hosts reached their maximum size. Diet did, however, influence the maximum size and consequently the growth rate of worms, which were larger and grew faster on kelp-fed abalone than on those fed a commercial pellet diet. Despite diet having no effect on fecundity and offspring size, kelp-fed worms matured earlier. The maximum size of kelp-fed worms was unaffected by the absence of a live host, suggesting that the worms do not rely on the host for food. The absence of a live host reduced the growth and sexual maturation rates of worms. There was no difference in the size of offspring in the two treatments, but fewer worms matured sexually and fewer broods were produced on “shells only” than on live hosts. The lower growth rate and reproductive output of worms on “shells only” may be due to the diversion of energy from growth and reproduction to burrow expansion.