ISSN 1812-9250 
ISSN 1814-0815






Volume 6, Number 2

Published online 31/03/2010


R.N. Burukovsky

Morphology and biology of shrimp Nematocarcinus gracilipes Filhol, 1884 (Decapoda: Nematocarcinidae)

Kaliningrad State Technical University, Kaliningrad, 236000, Russia.

ABSTRACT: The distal-ventral organ of abdomen’s IV segment in shrimp Nematocarcinus gracilipes Filhol 1884 differ from ones of all another species of this genus by presence of unfledged, thickened, spindle-shaped by form and close located chaetae. The rostrum traits are changed during ontogenesis and its allometric growth is positive regarding the carapace. The rostrum growth take place due to mainly active growth of its distal part that is without spines. In juvenile shrimps distal part is not more than 0.3 of rostrum length, but in adult it is 0.7–0.8. The V abdominal segment’s pleura form is changed during ontogenesis also. In mature adults with carapace length 15 mm and more the pleura has small spine. The spine is lacking in smaller shrimps, and the upper edge of pleura is rounded. Females of this species become mature at carapace length 18 mm.

KEY WORDS: Nematocarcinus gracilipes: the morphological description, the ontogenetic variability

(in Russian with English Summary)

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A.G. Dvoretsky 1, T.A. Britayev 2

Population biology of symbiotic amphipods Ischyrocerus spp. and their relationships with the host, the red king crab, in the Barents Sea

1 Murmansk Marine Biological Institute KSC RAS, Vladimirskaya Str. 17, 183010 Murmansk, Russia.

2 A.N. Severtsov Institute of Problems of Ecology and Evolution RAS, Leninsky pr. 33, 119071, Moscow, Russia.

ABSTRACT: The relationship between two amphipod species of the genus Ischyrocerus and the alien species, the red king crab, and the population structure of these amphipods were studied in the Barents Sea. In 2004, 58.4% and 21.5% of crabs were colonized by I. commensalis and I. anguipes respectively. For both species of amphipods proportion of crabs with amphipods increased with the increase of the host size. All crabs with carapace width (CW) more than 140 mm were infested by I. commensalis. For I. anguipes prevalence never exceeded 50 %. Small crabs with CW less than 56 mm were never infested. The amphipods I. commensalis were located on the mouth appendages, gills, pereiopods between basiopodite and ischiopodite as well as between meropodite and carpopodite. Less frequently they were located on the abdomen, carapace, and eggs of crab females. Specimens of I. anguipes were located on the same sites but they were rarely found on the mouth appendages, gills and female eggs masses. The two species co-occurred on 47 crabs out of 132, other crabs were hosts of I. commensalis only. In smaller crabs with 60–120 mm CW, the ratio between amphipod species was 50:50. In larger crabs with CW > 120 mm, more than 80% of symbiotic amphipods were I. commensalis. In populations of both species, females were more abundant and larger than males. In both amphipod species, the proportion of females at later stages of maturity increased as crab size increased. There were marked differences in the diameter of the embryo at the first maturity stage and mean individual fecundity between the two amphipod species. These values were 0.40±0.05 mm and 23.0 eggs on average in I. commensalis, and 0.28±0.06 mm and 7.0 eggs on average in I. anguipes. Our results demonstrated that I. commensalis is more closely associated with the host than I. anguipes. The relationships of both amphipods with the red king crab are discussed.

KEY WORDS: red king crab, symbionts, amphipods, population biology, Barents Sea.

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O.V. Ezhova, V.V. Malakhov

Three-dimensional structure of the skeleton and buccal diverticulum of an acorn worm Saccoglossus mereschkowskii Wagner, 1885 (Hemichordata: Enteropneusta)

Moscow State University, Biological Faculty, Department of Invertebrate Zoology; Leninskie Gory, 1, bldg. 12, Moscow, 119991 Russia.

Abstract: We describe and illustrate the morphology of unpaired proboscis skeleton and buccal diverticulum of a hemichordate Saccoglossus mereschkowskii for the first time and compare them to homologous structures in other species. The proboscis skeleton is a unique structure found only in enteropneust hemichordates. It is made of cartilaginous-like material and supports the buccal diverticulum. The proboscis skeleton is a Y-shaped organ, which consists of the unpaired anterior plate and two posterior horns. The anterior part of the plate bears the conical rostrum with the two symmetrical supporting saucers on each side. The ventral side bears a central fossa. A pair of lateral wings extends on each side of the proboscis skeleton. The ventral keel passes along the ventral midline. The horns are curved symmetrical outgrowths separating the flattened diverticulum base from the buccal tube. The buccal diverticulum consists of three main parts: the flattened base, the isthmus and the hood-shaped anterior region, supported by the skeletal rostrum. The isthmus consists of the axial part with a small spherical lumen. The base of diverticulum anterior part has three outpocketings: one ventral and two lateral. The skeleton growths fit the appropriate depressions of the buccal diverticulum surface. The morphology of the skeleton and the buccal diverticulum in enteropneusts varies from species to species and can serve as a potentially useful taxonomic character.

KEY WORDS: Saccoglossus mereschkowskii, proboscis skeleton, buccal diverticulum, morphology, taxonomy.

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V.G. Gagarin

New species of enoplids (Nematoda: Enoplida) from Mediterranean Sea

Institute of Inland Waters Biology, Russian Academy of Sciences, Borok, Yaroslavl region, 152742, Russia.

ABSTRACT: Three new species of free-living nematodes of the order Enoplida were found at the sea cost of Mediterranean Sea near Israel: Cylicolaimus brachyurus, Epacanihion mac­ro­laimus, Micoletzkyia sedata. Cylicolaimus brachyurus sp.n. is similar to C. obtusidens Ditlevsen, 1926, but has a shorter body, longer outer labial sensillae and relatively shorter tail. Epacanthion macrolaimus sp.n. differs from E. brevispiculosum Mawson, 1958 in a absence of somatic setae, longer outer labial sensillae, shorter tail, shorter spicules of copulatory apparatus and other location of precloacal supplement in male. Micoletzkyia sedata sp.n. is similar to M. mucronata Vitiello, 1970, but do not have somatic and caudal setae, has a shorter oesophagus, longer and slender tail

KEY WORDS: nematodes, Mediterranean Sea, new species.

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V.P. Nikishin

Structure and differentiation of tissues of cysticercoids. 2. Differentiation of the exocyst in typical diplocyst of Aploparaksis bulbocirrus (Cestoda: Hymenolepididae)

Institute of the Biological Problems of the North, Portovaya Str. 18, 685000 Magadan, Russia

ABSTRACT: The fine structure of tail appendix of the typical dyplocyst Aploparaksis bulbocirrus Deblock et Rausch, 1968 since first invagination up to stage of mature cysticercoid has been investigated. In composition of exocyst elements of epithelial and muscle tissues are defined and, besides, few low-differentiated cells of peculiar organization (“dark cells”) are found. Elements of the connective tissue are not revealed. The exocyst histogenesis is characterized by differences in tegument construction of its outer and inner surfaces, destructive changes of tegument after invagination of scolex, low-differential level of myocytes. The obtained data support the idea of protective and trophic functions of exocysts.

Key words: cysticercoid, diplocyst, ultrastructure, first invagination, scolexogenesis, tail appendix, exocyst.

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N.I. Zaslavskaya, E.S. Kornienko, O.M. Korn

Genetic similarity between Pagurus gracilipes (Stimpson, 1858) (Decapoda: Paguroidea) and another pagurid and diogenid hermit crabs from Russian waters of the Sea of Japan

A.V. Zhirmunsky Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, 17 Palchevskogo Str., Vladivostok 690041, Russia.  

Abstract: Biochemical genetic approach was applied to clarify the taxonomic status of the hermit crab Pagurus gracilipes which was compared with five species of the family Paguridae (P. brachiomastus, P. ochotensis, P. middendorffii, P. proximus, P. minutus) and with two species of the family Diogenidae (Diogenes nitidimanus and Stratiotes nigroapi­culus) using 18 allozyme loci. Genetic identity values between P. gracilipes and species of the family Paguridae (from 0.611±0.117 for P. gracilipes vs P. proximus, to 0.249±0.102 for P. gracilipes vs P. middendorffii) suggest that this species should retain its position in the genus Pagurus. This conclusion is supported by similar average identity value between other species of the genus Pagurus (I=0.444±0.110) and low genetic similarity between the genera Diogenes and Stratiotes (I=0.167±0.084) and between the families Paguridae and Diogenidae (I=0.102±0.005).

Key words: Decapoda; hermit crab; allozyme electrophoresis; genetic similarity; Sea of Japan.

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