Electrophoretic evaluation of the taxonomic status of two species of sea anemone

Puerto Rican populations of two species of sea anemones (Bunodosoma cavernata and B. granulifera) which had previously been considered one were assayed electrophoretically for enzymes encoded by 12 loci. The two species shared no common allozymes at 6 of the 12 loci. Genetic distance and identity values based on these allozymes were computed for the Puerto Rican populations and for B. cavernata from Florida and B. granulifera from Panama. The Puerto Rican populations of both species had much higher genetic identities for their geographically distant conspecifics than for each other. These results indicate that the two species are reproductively isolated and should be considered as separate valid species. Average heterozygosities are presented which are the first published for coelenterate species.     

Parameters that specify the timing of cytokinesis.

One model for the timing of cytokinesis is based on findings that p34(cdc2) can phosphorylate myosin regulatory light chain (LC20) on inhibitory sites (serines 1 and 2) in vitro (Satterwhite, L.L., M.H. Lohka, K.L. Wilson, T.Y. Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard. 1992. J. Cell Biol. 118:595-605), and this inhibition is proposed to delay cytokinesis until p34(cdc2) activity falls at anaphase. We have characterized previously several kinase activities associated with the isolated cortical cytoskeleton of dividing sea urchin embryos (Walker, G.R., C.B. Shuster, and D.R. Burgess. 1997. J. Cell Sci. 110:1373-1386). Among these kinases and substrates is p34(cdc2) and LC20. In comparison with whole cell activity, cortical H1 kinase activity is delayed, with maximum levels in cortices prepared from late anaphase/telophase embryos. To determine whether cortical-associated p34(cdc2) influences cortical myosin II activity during cytokinesis, we labeled eggs in vivo with [(32)P]orthophosphate, prepared cortices, and mapped LC20 phosphorylation through the first cell division. We found no evidence of serine 1,2 phosphorylation at any time during mitosis on LC20 from cortically associated myosin. Instead, we observed a sharp rise in serine 19 phosphorylation during anaphase and telophase, consistent with an activating phosphorylation by myosin light chain kinase. However, serine 1,2 phosphorylation was detected on light chains from detergent-soluble myosin II. Furthermore, cells arrested in mitosis by microinjection of nondegradable cyclin B could be induced to form cleavage furrows if the spindle poles were physically placed in close proximity to the cortex. These results suggest that factors independent of myosin II inactivation, such as the delivery of the cleavage stimulus to the cortex, determine the timing of cytokinesis.     

Rare and new cumaceans (Crustacea,Peracarida) from?the southern margin of the Cap Ferret Canyon (Bay of Biscay)

A new cumacean genus and species, Ithyleucon sorbei gen. et sp. n., was described from material collected in the southern margin of the Cap Ferret Canyon (Bay of Biscay, NE Atlantic). Although the new genus resembles Pseudoleucon Zimmer, 1903, in terms of the general aspect of the carapace and the pseudo-rostrum position, it shows important differences in the uropod structure and in the size of the antenna 1 accessory flagellum. In addition, some comments regarding the morphology of certain rare species (Mesolamprops denticulatus Ledoyer, 1983, Hemilamprops normani Bonnier, 1896 and Schizocuma spino-culatum (Jones, 1984)) are also provided.     

Marine insects: genital morphology, phylogeny and evolution of sea skaters, genus Halobates (Hemiptera: Gerridae)

Five species of sea skaters, genus Halobates Eschscholtz, are the only insects to have successfully colonized the open ocean. In addition, 36 species are found in sheltered coastal waters throughout tropical Indo-Pacific. The taxonomy of the genus is relatively well known, but reliable hypotheses about phylogenetic relationships are required if the biogeography and evolution of sea skaters is to be discussed in a meaningful way. This work presents the results of a study of new characters from the genital segments, especially those of the male phallus and the female gynatrial complex, and a reinterpretation for several other characters. In total 64 characters were scored for 26 species of Halobates , two species ofAsclepios and one species of Metrocoris. With Asclepios and Metrocoris species as outgroups, the character state sets were analysed cladistically using the computer program Hennig86. After critical evaluations of both characters and clades, a phylogeny for Halobates is presented and its taxonomic implications are discussed. A number of monophyletic species groups are delimited. One genus-level synonymy and three species-level synonymies are suggested. The evolution of Halobates is discussed in the light of the reconstructed phylogeny and present knowledge of the ecology and behaviour of sea skaters. A hypothesis of ecological evolution in halobatine water striders is proposed and tested.     

COMPARISON OF VERTICAL AERIAL PHOTOGRAPHIC AND GROUND CENSUSES OF STELLER SEA LIONS AT AÑO NUEVO ISLAND, JULY 1990-1993

Counts of Steller sea lion ( Eumetopias jubatus ) pups and non-pups (adults and juveniles) from aerial photographs of rookeries at Año Nuevo Island between 1990 and 1993 were significantly higher than those made on the ground. Based on regression of natural logs of photographic counts versus year, the number of pups declined at a rate of −0.099yr while non-pup numbers declined at −0.315/yr. Examination of ground count data for the same period revealed a significant decline in non-pups (−0.139/yr), but no trend was detected in the ground counts of pups. The regression coefficients from photographic and ground counts of non-pups did not differ significantly. Power analyses using the program TRENDS indicated that detectable rates of change in abundance from four annual surveys were much lower for counts of pups than counts of non-pups where sampling precision was based on fits to linear models.     

Bathycamptus eckmani gen. et spec. nov. (Copepoda,Harpacticoida) with a review of the taxonomic status of certain other deepwater harpacticoids

Bathycamptus eckmani gen. et spec. nov., which is associated with mudballs produced by the. cirratulid Tharyx luticastellus, is described from bathyal muds in San Diego Trough, off California. ?Heteropsyllus minutus Wells from the Haden Ground, Scotland is considered to be its closest relative and is placed in the same genus. The genera Bathycamptus and Psammocamptus Mielke are regarded as sister groups on the basis of the shared sexual dimorphism shown by P3-P4. Relationships with other marine Canthocamptidae are discussed, and a re-evaluation of the genus Hemimesochra Sars is made. It is concluded that this genus should encompass only the type species H. clavularis Sars. ?Leimia dubia Wells and H. nympha Por are transferred to the new genus Boreolimella, which is closely related to Bathycamptus but not to Leimia Willey. The genus Perucamptus gen. nov. is established to include H. rapiens Becker and shows no clear relationship with the other genera. H. trisetosa Coull is assigned to Caroliiaicola gen. nov., which is regarded as being an advanced member of the Paranannopidae. H. secunda Wells is recognised as belonging to Mesopsyllus Por; whilst H. nixe Por is considered the type species of a new genus Pusillargillus.     

Copepoda from deep-sea hydrothermal vents and cold seeps

Recent explorations of hydrothermal vents in the eastern Pacific (Juan de Fuca spreading zone, Guaymas Basin in the Gulf of California, East Pacific Rise at 21° N and 13° N, and Galapagos Rift) and on the Mid-Atlantic Ridge have revealed many copepods, mostly siphonostomatoids with few poecilostomatoids. In these habitats in depths from 1 808 to 3 650 m water temperatures may reach nearly 15 ° C. Among more than 22 000 copepods from vents examined two new families, 11 new genera, and 32 new species were represented.In addition, two new copepods were found in 3 260 m at cold seeps at the base of the West Florida Escarpment in the Gulf of Mexico, an environment not thermally active, with water temperatures about 4.39 °C.Some of these copepods were associated with host invertebrates such as a Nuculana-like protobranch bivalve, a polychaete, and two species of shrimps. Others were obtained from washings of bivalves or vestimentiferans or by means of corers or slurp guns.     

Ionophore-induced efflux of sodium and potassium ions from sea urchin eggs

The efflux of K⁺ and Na⁺ from sea urchin eggs during Ca²⁺ ionophore A23187-induced parthenogenesis was studied in a K⁺ and Na⁺-free artificial seawater using extracellular ion-specific electrodes. We have probed this model system with monovalent cation-specific ionophores to determine if they affect K⁺ efflux in the unfertilized egg and whether any changes in ionophore sensitivity are observed during egg activation. In 500 mM choline chloride, 10 mM CaCl₂, 50 mM MgCl₂, 10 mM Tris-Cl pH 8.0, A23187 induced a rapid efflux of K⁺ and Na⁺ from the eggs after a short lag time (10–15 seconds). After the burst, the rate of K⁺ efflux remained higher than the pre-activation rate, but was lower than during the burst phase, while the rate of Na⁺ efflux became nearly zero. Monovalent cation-specific ionophores (valinomycin, gramicidin and nigericin) had no effect on K⁺ efflux from the unfertilized eggs in our model system. However, once the egg was activated by A23187, each of the above ionophores caused a prolongation of the burst phase for many minutes. These results show that the unfertilized egg plasma membrane (using our artificial conditions) is not susceptible to the monovalent cation-specific antibiotics and suggest that either the inserted cortical granule membrane or the developing fertilization envelope interacts with these ionophores to cause the change in rate-limiting step for K⁺ efflux observed egg activation.     

Copper ions and hydrogen peroxide form hypochlorite from NaCl thereby mimicking myeloperoxidase

Sea urchins have elaborated multiple defenses to assure monospermic fertilization. In this work, we have concentrated on a study of the mechanism(s) by which hydrogen peroxide (H₂O₂) prevents polyspermy in Arbacia punctulata. We found that it is not H₂O₂ but probably hypochlorous acid/hypochlorite (HOCl/OCl^?) derived from H₂O₂ that is toxic to the supernumerary sperm. The spermicidal activity of H₂O₂ is potentiated by at least one order of magnitude by cupric ions (Cu²⁺). This increased toxicity is not due to the formation of hydroxyl radicals (·OH) because ·OH scavengers did not counteract the activity of Cu²⁺. More-over, substitution of Cu²⁺ by ferrous ions (Fe²⁺), which are known to cause formation of ·OH from H₂O₂, had no effect on fertilization even at 10²?10³ times higher concentrations. In contrast, 3-amino-1,2,4-triazole (AT), an HOCl/OCl^? scavenger, totally reversed the toxic effects of Cu²⁺. Furthermore, we found that HOCl/OCl^? is generated in solutions of H₂O₂ and Cu²⁺ in the presence of 0.5 M NaCl and that its accumulation is abolished by AT. Thus it is possible that the antifertility properties of copper are due to its ability to mediate formation of HOCl/OCl^?. HOCl/OCl^? generated by Cu²⁺ from H₂O₂ and Cl^?, a low concentration of exogenously added HOCl/OCl^?, or increased concentrations of H₂O₂ has similar inhibitory effects on the fertilization process in sea urchins. Therefore, we suggest that polyspermy is prevented by the action of a myeloperoxidase that affects the formation of HOCl/OCl^? from the Cl^? present in sea water through reaction with H₂O₂ generated by the newly fertilized egg.