Recent reviews of the species of brachiopods and sipunculans reported from Costa Rica were conducted by Emig (2009) and Vargas and Dean (2009), respectively.
nudus and other sipunculans were reported by Spongberg (2006).
No recent published data is available on the abundances of brachiopods and sipunculans from the Gulf of Nicoya estuary.
However, while the metameric organization of the nervous system is retained in the adult stage of most annelids and echiurans (although the ventral nerve cords may fuse), the sipunculans lose this arrangement during development by migration of the perikarya.
Despite a high degree of variation in the number of longitudinal nerve cords in annelids (including echiurans) and sipunculans, neurodevelopmental studies have shown that a paired ventral nerve always forms the first anlage of the future ventral nervous system, even in those annelid taxa that as adults have multiple ventral cords.
Occurrence of teleplanic pelagosphaera larvae of sipunculans in tropical regions of the Pacific and Indian Oceans.
Genetic differentiation despite teleplanic larval dispersal: allozyme variation in sipunculans of the Apionsoma misakianum species-complex.
2003), Leiosolenus hanckoki (Keen 1971, Cantera and Contreras 1988, Kleeman 1990), and four sipunculans, Aspidosiphon steenstrupii, Paraspidosiphon klunzingeri (synonym of P.
calyculata and Leiosolenus hanckoki, two sipunculans Phascolosoma puntarenae and Paraspidosiphon klusingeri, the polychaete Dorvillea (Schistomeringos) annulata, and the crustaceans Pomatogebia rugosa and P.
Sipunculans are oxiconformant worms that have low levels of antioxidant enzymes compared to vertebrates, but also compared to other marine invertebrates, and they are thought to be protected from the formation of reactive oxygen species in mitochondria by a low respiration rate and an alternative, branched electron pathway (Buchner et al.
Given the importance of a homeostatic balance of apoptosis in immunity, regulation of coelomocyte apoptosis could be significant to the sipunculan immune system, and several environmental factors could have an impact on the coelomocytes, thus triggering the apoptotic program.
1997), prosobranchs (McGee and Targett, 1989; Boettcher and Targett, 1998), sipunculans (Rice, 1986), and other echinoids (Pearce and Scheibling, 1990b) are induced to settle and metamorphose by dissolved compounds arising from appropriate substrata, prey species, or conspecific individuals.
1972), sponges that live among or within the skeletons of the corals (Glynn, 1997), serpulid polychaetes whose tubes become embedded in living coral colonies, polychaetes and asteroids that feed on corals, sipunculans that burrow into coral skeletons, and many others (Paulay, 1997).
Invertebrates with erythrocytes are relatively rare, but phylogenetically diverse; they include representatives of the annelids, brachipods, echinoderms, echiurans, molluscs, priapulids, and sipunculans.
Our survey encompasses annelid, brachiopod, echinoderm, echiuran, molluscan, priapulid, and sipunculan representatives among the invertebrates (Table 1), as [TABULAR DATA FOR TABLE I OMITTED] well as a wide range of vertebrates including fish, amphibians, reptiles, birds, newborn marsupials, and placental mammals (Cohen and Nemhauser, 1985; Cohen et al.