O. M. Korn

Larval Development in Peltogasterella Studied by Scanning Electron Microscopy (Crustacea: Cirripedia: Rhizocephala)

SEM and light microscopic studies on the larvae of the rhizocephalan barnacles Peltogasterella gracilis and P. sulcata reared in the laboratory revealed the presence of 5 naupliar instars, the newly found stage being instar 3. It resembles instar 2 but is larger and has a body slightly tapering towards the posterior end, a reduced subapical (preaxial) seta on the antennule, and both transverse grooves and a specific denticle ornamentation on the hind body of female larvae. In cultures, the larvae of both species develop into cyprids within 4-5 days after release. Peltogasterella nauplii have a size comparable to that seen in Sacculina and Peltogaster, but they are much smaller than the larvae of the cold-water Briarosaccus. The nauplii of Peltogasterella are lecitotrophic and have limb setation and other feeding structures highly reduced. Peltogasterella nauplii have a cuticular flotation collar encircling the body, but it is very small, delicate, and almost smooth. It therefore differs from the homolo- gous, but much larger, and heavily ornamented flotation collars seen in nauplii of Peltogaster and Briarosaccus. A characteristic feature in Peltogasterella nauplii is the single subterminal seta at the distal end of each frontolateral horn, whereas nauplii of Briarosaccus and Peltogaster have two such setae. The antennulary basipod carries a short additional seta, which represents the only remaining rudiment of gnathobases. Nauplii of Briarosaccus and Peltogaster have a homologous, but significantly longer seta, whereas Sacculina nauplii lack this seta altogether. The nauplii of P. gracilis and P. sulcata are very similar in size and morphology, but those of P. sulcata differ by somewhat longer frontolateral horns and furcal spines. Another distinctive feature of P. gracilis nauplii is the ven- tral ornamentation of the hind body that shows different pattern at different stages of development and reflects an internal development of segments. This ornamentation is only weakly pronounced in P. sulcata nauplii. Compari- son with larval development in Briarosaccus tenellusleads to the conclusion that the rhizocephalan ground pattern comprises six naupliar stages just as in other cirripedes (e.g., Thoracica). Comparison of lattice organ morphology indicates a sister group relationship between the families Peltogastridae and Lernaeodiscidae. Our study highlights the value of SEM revealed larval characters and of characters other than appendage setation as being important in rhizocephalan phylogeny.

Illustrated key for the identification of brachyuran zoeal stages (Crustacea: Decapoda) in the plankton of Peter the Great Bay (Sea of Japan)

A dichotomous key for brachyuran megalopae from Peter the Great Bay (Russian waters of the Sea of Japan) is provided. The key covers 18 taxa identified to species level and uses only the external characters of larvae that are easy to observe with a stereomicroscope without specimen dissection. The key is mainly based on the new original descriptions of larvae obtained both from plankton samples and from laboratory culture. Period of occurrence of larvae of each species in the plankton is also presented.

Combined Effects of Seawater Temperature and Salinity on Development of the Larvae of the Rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia)

The effects of seawater temperature (12, 16, 20, 22, and 25°C) and salinity (of 8 to 34‰) in different combinations on the larvae of the rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia), a parasite of the hermit crab Pagurus proximus, were examined. The development of P. reticulatus is comprised of five naupliar stages and one cypris stage. Nauplii have a specific structure, the flotation collar encircling the dorsal side of the larval body. Larvae lack the pigmented nauplius eye, and they show no positive phototaxis. Successful naupliar development occurred in temperature and salinity ranges of 16–25°C and 20 to 34‰, respectively; but all nauplii died at 12°C and 16‰. The duration of each naupliar stage increased under lowering of the seawater temperature. At 22–25°C and 26–28‰, the entire development cycle was completed in 72–80 h; and at 16°C and 20‰ it lasted 153 h. The cypris larvae showed a greater resistance to decreased salinity in comparison with the nauplii. At temperatures of 16–25°C and salinities of 14 to 34‰, the lifespan of cyprids was 6 to 12 days, and it decreased at increasing temperature.

Peculiarities of reproductive biology and larval development of the red king crab Paralithodes camtschaticus in Peter the Great Bay, Sea of Japan

Based on materials from trawling (2002–2005) and plankton (2004–2006) surveys, some problems of the reproduction biology of the red king crab Paralithodes camtschaticus (Tilesius, 1815) population from Peter the Great Bay are considered. It was shown that the width of the carapace varied from 105 to 190 mm in female red king crabs with eggs; 50% of the females reached maturity with a carapace width of 112.8 mm. The average individual absolute fecundity of females was 200000 (114000–296000) eggs. A direct linear correlation between fecundity and female carapace width was recorded. The zoeas I–IV of the red king crab occurred in the plankton from the middle of April up to the end of the second decade of May at water temperatures from 2.8 up to 9.3°C. The periods of larval occurrence in plankton in various years correlated with the water temperature, with a temperature decrease, the duration of the pelagic period increased. No direct correlation was revealed between the phytoplankton bloom and larval release. The density of red king crab larvae in Peter the Great Bay did not exceed 0.02–13.3 spec./m3. The maximum concentration of zoeas was recorded in the central part of Ussuriysky Bay.

The larval development of Pagurus proximus (Decapoda: Anomura: Paguridae) reared in the laboratory

The larval development of the hermit crab Pagurus proximus is described and illustrated from the larvae reared in the laboratory. The development included four zoea and a single megalopa, thus following the typical pattern in the Paguridae. At 20–22°C megalopa of P. proximus was attained 17 to 23 days after hatching. Morphological characters of zoea and megalopa of P. proximus are compared with those described for the related species P. brachiomastus . The distinctive differences between larvae of these two species lend support to the separation of P. proximus from P. brachiomastus. The main larval features allow to assign P. proximus larvae to the Group A of Pagurus larvae (typical representative: P. bernhardus ).

Life History of the Barnacle Balanus Amphitrite Darwin and Its Role in Fouling Communities of Peter the Great Bay, Sea of Japan

The life history of the barnacle Balanus amphitrite Darwin and its role in fouling communities of Golden Horn Bay (Peter the Great Bay), which is subjected to thermal pollution, were studied. The warm-water B. amphitrite occurs as a common minor species on operational vessels and waterworks in Peter the Great Bay, where it was brought by ocean-going ships operating on Russia–Japan lines. Even in the conditions of the higher temperature regime of Golden Horn Bay, the reproductive season of B. amphitrite is confined to the summer and autumn months. The adult individuals brought by ships in summer produce 2–3 generations of larvae. The development of larvae and their settling on the substrate occurs from August to October within a broad temperature range from 22.5 up to 12°C. Even in the low temperatures of Golden Horn Bay the larvae attain a greater size than those in tropical and subtropical waters. The juveniles have time to reach maturity and to produce their own progeny, but most often they perish with winter drop in the water temperature. It was shown that in Peter the Great Bay there is dependent population of B. amphitrite inhabiting the anthropogenic substrates only in the warm season: water works, idle vessels, and operational offshore vessels. The water temperature is the limiting factor of successful acclimation of that species.

The complete larval development of the lobster shrimp Boasaxius princeps Boas, 1880 (Decapoda: Axiidea: Axiidae) obtained in the laboratory

The complete larval development of Boasaxius princeps (Boas, 1880) (Decapoda: Axiidea: Axiidae) is described and illustrated for the first time from material reared in the laboratory. The development includes eight zoeal stages and a single megalopal stage. At 20–22°C the first megalopa was attained 38 days after hatching. It is the first description of the larvae of a lobster shrimp with long development obtained under laboratory conditions. An identification key to zoeal stages of B. princeps is presented. Numerous characters show that zoeae of B. princeps are similar to the larvae of Axiopsis serratifrons. Thus, according to the overall similarities of the larval characters, Boasaxius and Axiopsis are closer to each other than other axiid genera.

Symbiotic Crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae) from Vostok Bay, Sea of Japan: A New Species for the Fauna of Russia

A symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae) that lives in burrows of the large ghost shrimp Upogebia major (De Haan, 1841) and U. issaeffi (Balss, 1913) (Upogebiidae) was found in Vostok Bay (Peter the Great Bay, Sea of Japan) for the first time. The occurrence of mature and juvenile specimens indicates the existence of a stable population of this species in the investigated region. This finding substantially extends the distribution area of S. balssi in the Sea of Japan.

Comparative morphology of larvae of coastal crabs (Crustacea: Decapoda: Varunidae)

The larval development of three crabs of the Varunidae family, (Hemigrapsus sanguineus, H. penicillatus, and H. longitarsis), widely spread in Russian waters of the Sea of Japan, were studied under laboratory conditions. At a temperature of 20–22°C and a salinity of 32‰ about 30% of larvae a complete developmental cycle, including five zoeal stages and megalopa, took from 22 to 30 days. All larval stages are illustrated and described in detail. Zoea I and zoea II of the studied crabs are not distinguishable. Zoea III–V of these species differ in the number of dorsomedial setae on the abdominal somite I and in the number of setae on the posterodorsal arch. The megalopae of three Hemigrapsus species possess a different number of segments, aesthetascs and setae on the antennular exopod. In spite of the great similarity of larvae of genera Hemigrapsus and Eriocheir, the latter possesses a number of distinctive features in all developmental stages, supporting the separation of these genera.

Acclimation and introduction of hydrobionts ships’ ballast water organisms in the Port of Vladivostok

Work on the investigation of organisms of ballast water and sediments of ships sailing on Russia-Japan and Russia-China lines was started in the Port of Vladivostok for the first time for the Far East seas of Russia. In total, 145 taxa, 37 microalgal species, 24 holoplankton species, 22 meroplankton taxa, and 10 meiofauna groups were revealed, 24 species of microscopic mycelia fungi were attributed, and 28 morphologically distinct bacterial stains were isolated. Potentially toxic microalgal species were found: the dinoflagellates Dinophysis acuminate and Prorocentrum cordatum and the diatom Pseudo-nitzschia pungens. The tropical-subtropical copepod Pseudocalanus inopinus was recorded in ballast water. Polychaete larvae of the Polydora genus with an unusual morphology, which were not occurring in the Peter the Great Bay previously, were recorded as probable southern migrants from the coastal waters of the southwest coast of Honshu Island. Live larvae of the hermit crab Diogenes nitidimanus were revealed in ballast water, supporting the possibility of introduction of this species in the Peter the Great Bay. Based on an analysis of the total number of colony-forming units of heterotroph microorganisms (within the order of 103–104 cells/ml), the ballast water of ships sailing on the Russia-Japan line was characterized as moderately polluted. The detection of Escherichia coli strains, exceeding the standards quoted in the International Convention by three times or more, showed the potential danger of a mass bioinvasion. Conditionally pathogenic and toxinogenic mycelial fungi, which are able to induce mycoses and mycotoxicoses in invertebrates and fishes, were isolated from ballast water. It was determined that ballast water of the “rusty” type was poorly suited for the existence of zoo- and phytoplankton forms. In the case of the construction of an oil terminal in the Peter the Great Bay, a sharp increase of the introduction of exotic species via the ballast water and foulings of tankers is inevitable