Halicryptus

Abstract: A new species of Priapulida was discovered from the Beaufort Sea near Barrow, Alaska. Following an unusually strong autumnal storm, 30 adult specimens of Halicryptus higginsi n.sp. were collected, many alive, from intertidal beaches Additional specimens were found in museum collections misidentified as Halicryptus spinulosus von Siebold 1849. The new species represents the 11th priapulid species described since 1968 and increases the number of described extant species of Priapulida to 18. While all other recently described priapulids have been meiofaunal, Halicryptus higginsi n.sp. is macrofaunal and the largest extant priapulid species, with one specimen being 39 cm long in a contracted condition. Additional key words: arctic, benthos In recent years the concept of the marine phylum Priapulida has changed radically, from that of a macrobenthic, cold-water taxon, to one that is more speciose in the tropical meiofauna. Before 1968, only 7 extant species were known and additional species had been described from the fossil record; all extant species were macrobenthic and found only in cold-water habitats (Higgins et al. 1993). In 1968 the first meiobenthic priapulid, Tubiluchus corallicola VAN DER LAND 1968, was described from a tropical, shallowwater habitat (van der Land 1968). Since 1968 an additional 9 priapulid species, all meiobenthic and mostly inhabitants of tropical, shallow-water sediments, have been described. Tubiluchus arcticus ADRIANOV, MALAKOV, CHESUNOV, & TSETLIN 1989 is the only cold-water species that has been described in recent years, and it is a meiofaunal priapulid that inhabits shallow-water sediments in the arctic (Adrianov et al. 1989). During a survey of museum specimens of priapulids, one of us (VS) discovered that specimens in the United States National Museum of Natural History, Smithsonian Institution, misidentified as Halicryptus spinulosus von Siebold from Barrow, Alaska, had been used for scanning electron microscopy (Merriman 1981) and instead represented a new and undescribed congener. Subsequent to the museum discovery we found larvae and juveniles of the undescribed species a Author for correspondence. E-mail: fftcs@uaf.edu in the shallow subtidal during two expeditions to Barrow, Alaska in 1991 and 1992, but did not find adults of the new species. Following an unusually strong autumnal storm in 1993, 30 adult specimens of Halicryptus higginsi n.sp. were collected, many alive, from intertidal beaches near Barrow. In this paper we describe the new species and compare it with H. spinulosus. The larvae will be described in a separate pub-

Abstract: The blood of the priapulid Halicryptus spinulosus was investigated by protein electrophoresis and electron microscopy. Two cell types were encountered: irregularly shaped amoebocytes and spherical erythrocytes. In vitro, the former efficiently phagocytized bacteria and tended to coagulate. A 12-kilodalton polypeptide was the major molecule in erythrocytes, amounting to 20–30% of total erythrocytic proteins. It contained iron and probably formed complexes of higher molecular mass in the cells. These findings support suggestions that Halicryptus contains a haemerythrin-like pigment. Blood colour ranged from pink to black, probably depending on the hydrogen sulphide or oxygen concentration of the medium. Haematocrit values averaged 15.6%, and 58 000 erythrocytes were typically counted per microlitre of body fluid. The major blood constituent was a water-clear serum containing at least 20 proteins at very low and fairly variable concentrations; the molecular masses have been determined for 14 of these. A 46-k...

Abstract: The phylum Priapulida is a small group of marine worms that is allied with the nematodes, kinorhynchs, loriciferans and nematomorphs in a clade called the Cycloneuralia or Introverta. Together with the arthropods they are generally considered to comprise the Ecdysozoa, a clade of moulting animals. A number of recent priapulid species possess features that resemble the predicted Ecdysozoan ancestor. In addition, recent molecular studies have also shown that they are basal within the Ecdysozoa/Cycloneuralia (Garey 2001, Webster et al. 2006). Their putative basal position thus makes priapulids highly interesting research objects for understanding the evolution of Ecdysozoa. Earlier investigations of the early embryology of the priapulid Priapulus caudatus are critically revised with the aid of modern techniques and equipment, confirming earlier studies that the early cleavages are highly symmetrical, total, subequal, radial and stereotypical. New results show that up to the sixth cleavage, the spindles are oriented along the animal/vegetal axis at both poles. This unique cleavage pattern has only limited similarities to other animals. During the sixth cleavage two cells move inwards and gastrulation commences. If the mesoderm is derived from both cells, its origin differs from that of many other protostomes.Two previously undescribed larval stages of P. caudatus; the light bulb shaped hatchling and the first lorica larva are described. The second lorica larva superficially resembles the previously described type 2 lorica larva (Higgins et al 1993). Differences between the second lorica larva and the type 2 lorica larva, with respect to possible ecophenotypical variation and sub-specialization, are described. Preliminary data are presented on musculature development of P. caudatus. Preliminary data have also been obtained on the early development of a second priapulid, Halicryptus spinulosus. Comparison of Halicryptus and Priapulus may help to resolve developmental ground pattern of the priapulids.