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PubMed1977

The diminution of Heterochromatic chromosomal segments in Cyclops (Crustacea, Copepoda).

The chromosomes of Cyclops divulsus, C. furcifer, and C. strenuus, like those of several other Copepods, undergo a striking diminution of chromatin early in embryogenesis. The process is restricted to the presumptive soma cells and occurs at the 5th cleavage in C. divulsus, at the 6th and 7th in C. furcifer, and at the 4th in C. strenus. The eliminated chromatin derives from the excision of heterochromatic chromosome segments (H-segments). Their chromosomal location is different in the three investigated species: Whereas in C. divulsus and C. furcifer the H-segments form large blocks-exclusively terminal in the former and terminal as well as kinetochoric in the latter-the germ line heterochromatin in C. strenuus is scattered all along the chromosomes. Extensive polymorphism exists with respect to the length of the terminal H-segments in C. furcifer, and with respect to the overall content of heterochromatin in the chromosomes of C. strenuus. In a local race of C. strenuus an extreme form of dimorphism has been found which is sex limited: females as a fule are heterozygous for an entire set of large (heterochromatin-rich), and a second set of small chromosomes in their germ line. Males are homozygous for the large set. In the first three cleavage divisions the H-polymorphism is solely expressed through differences of chromosome length. Following diminution the differences between homologous have disappeared. Feulgen cytophotometry demonstrates that in the three species the 1C DNA value for the germ line, as measured in sperm, is about twice that measured in somatic mitoses (germ line/soma C-values in picograms of DNA: C. strenuus 2.2/0.9, C. furcifer 2.9/1.44, C. divulsus 3.1/1.8). - The data imply that chromatin diminution is based on a mechanism which allows specific DNA segments, regardless of their location and size, to be cut out from the chromosomes without affecting the structural continuity of the remaining DNA. The mechanism may be analogous to that of prokaryotic DNA excision.

Animals↗
PubMed2002

Complete mitochondrial DNA sequence of Tigriopus japonicus (Crustacea: Copepoda).

The complete nucleotide sequence of the mitochondrial genome was determined for a harpacticoid copepod, Tigriopus japonicus (Crustacea), using an approach that employs a long polymerase chain reaction technique and primer walking. Although the genome (14,628 bp) contained the same set of 37 genes (2 ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes) as found in other metazoan animals, none of the previously reported gene orders were comparable to that of T. japonicus. Furthermore, all genes were encoded on one strand, unlike the mitochondrial genomes of most metazoan animals. Size reductions were notable for tRNA and rRNA genes, resulting in one of the smallest mitochondrial genomes in the arthropod lineage. Although it appears that such large-scale gene rearrangements have occurred in the ancestral species of T. japonicus, none of the proposed mechanisms parsimoniously account for this eccentric gene arrangement.

Journal Article↗
PubMed1999

Egg development, hatching and early life-history of Dissonus manteri (Copepoda), parasitic on the gills of coral trout, Plectropomus leopardus.

The early life-history of Dissonus manteri differs markedly from that of Caligidae and from that of its congener Dissonus nudiventris. The uniseriate egg strings are of typical caligid form, but the stage hatching from the egg is a preecdysis nauplius which moults immediately to the copepodid. The empty naupliar cuticle remains tethered to the egg string by a pair of posterior threads which attach to the internal surface of the egg membrane. The duration of egg development is 112 h and the mean duration of hatching is 5.2 h at 25 degrees C. Aeration and water movement are important for successful hatching. Under these conditions, hatching success is 94.8%, but decreases to 48.4% in static water with no aeration. Mean survival time of the copepodid in the absence of a host is 41.4 h at 25 degrees C. The reduction of early free-living stages in the life-cycle and the high survival rate from egg to copepodid could be important in future coral trout aquaculture, since the potential for re-infection by this parasite is very high.

Animals↗
PubMed2001

Effects of Oxyrrhis marina (Dinoflagellata), bacteria and vitamin D(2) on population dynamics of Tisbe holothuriae (Copepoda).

Laboratory experiments were performed to determine which food combinations had the most favorable effect on population dynamics of the harpacticoid copepod Tisbe holothuriae. In addition to basic diets of TetraMin (T), rice (R) or a mixture of both (T+R), supplements consisting of the following were given: the heterotrophic dinoflagellate Oxyrrhis marina, a bacterial suspension and vitamin D(2). Results show a beneficial effect of bacteria at a given concentration on T. holothuriae, which is enhanced in combination with vitamin D(2). A higher concentration of bacteria together with vitamin D(2), however, has a reverse effect leading to greater mortality, lower sex ratio and number of ovigerous females, and a dramatic decrease in production of eggs, regardless of the basic diet. We conclude that different concentrations of a given bacterial community may have variable effects on the reproduction of harpacticoid copepods and that, in addition to the bacteria, vitamin D(2) may also play a role in invertebrate nutrition.

Journal Article↗
PubMed2000

Laboratory maintenance of Eucyclops serrulatus (Copepoda: Cyclopoida).

A simple method for culturing a freshwater copepod Eucyclops serrulatus is described. A flagellate Chilomonas paramecium serves as the food organism. Starting from a single, egg-bearing female collected in a pond, the copepod proliferated for at least 10 generations apparently with no adverse changes. The stock culture has been maintained with minimal effort for at least 19 months. The method is expected to make the copepod useful in the laboratory as an intermediate host of various parasitic helminths.

Animals↗
PubMed1979

Two new species of Lepeophtheirus (Copepoda: Caligidae) parasitic on fishes from southern California waters.

Two new species of Lepeophtheirus are described and illustrated based on a collection from the Orange County sewer outfall, California. They are: L. remiopsis sp.nov. from the branchial cavities and external body surfaces of Parophrys vetulus Girard, Hippoglossina stomata Eigenmann & Eigenmann, Pleuronichthys verticalis (Jordan & Gilbert), Chitonotus pugetensis (Steindachner), and Porichthys notatus (Girard); and L. rotundipes sp.nov. from the external body surfaces and occasionally the gill cavities of Scorpaena guttata (Girard) and Citharichthys stigmaeus Jordan & Gilbert.

Animals↗
PubMed1990

Responses of the fish ectoparasite Salmincola edwardsii (Copepoda) to stimulation, and their implication for host-finding.

The short-lived infective copepodid stages of the copepod Salmincola edwardsii, ectoparasitic on brook trout, Salvelinus fontinalis, are under strong selective pressure to evolve efficient host-finding mechanisms. In laboratory experiments, we quantified the effects of visual and mechanical stimulation on the activity of the copepodids. We found that shadows passing above the copepodids and shock waves passing through the water generated marked increases in the rate and length of upward swimming bursts, which resulted in more time spent suspended in the water column and greater distances travelled. However, we found no strong evidence for a relationship between the magnitude of the copepodids' response and the intensity of stimulation. Although these responses are not host-specific, they allow the parasites to conserve their limited energy stores by increasing their host-finding activity only when potential hosts are nearby.

Analysis of Variance↗
PubMed1988

Characterization of two species of Lepeophtheirus (Copepoda, Caligidae) from flatfishes. Description of Lepeophtheirus europaensis sp. nov.

In the eastern Mediterranean, the copepod Lepeophtheirus thompsoni Baird, 1850, has been reported to infest turbot, brill and flounder. By combining several methods, including enzyme electrophoresis, we show that this species is found only in turbot. By contrast, brill and flounder are infested by a species of Lepeophtheirus that corresponds to no other species reported in the literature. We propose that the species be designated as L. europaensis and we describe the characteristics of the gravid female. This study was extended to the Atlantic populations of flatfishes and includes an investigation of L. pectoralis (Muller, 1776), which infects flounder in the North Sea; we also confirmed the presence of L. thompsoni (Baird, 1850) over the whole geographic range of turbot. Lastly, we discuss the specificity and distribution of these species along the European coasts.

Alleles↗
PubMed2000

Species of Caligus Müller, 1785 (Copepoda: Caligidae) parasitic on marine fishes of Taiwan.

Six species of copepods of the genus Caligus (Caligidae, Siphonostomatoida) parasitic on marine fishes of Taiwan are reported. They are: C. absens n. sp. from Priacanthus blochii and P. macracanthus; C. epinepheli Yamaguti, 1936 from Scolopsis vosmeri; C. kanagurta Pillai, 1961 from Decrapterts kurroides; C. laticaudus Shiino, 1960 from Lutjanus vitta and Parapristiopoma trilineatum; C. nengai Rangnekar, Rangnekar & Murti, 1953 from Triacanthus biaculeatus; and C. rotundigenitalis Yü, 1933 from Drepane punctata, Liza macrolepis and Terapon jarbua. C. distortus Pillai & Natarajan, 1977 is relegated to a synonym of C. nengai and C. multispinosus Shen, 1957 reported by Lin et al. (1994) from the cultured sea bream Acanthopagrus schlegeli is a misidentification for C. rotundigenitalis Yü, 1933.

Animals↗
PubMed2000

Parasitic copepods (Copepoda: Siphonostomatoida) from deep-sea and mid-water fishes.

The stages in the metamorphosis of the pennellid Cardiodectes medusaeus (Wilson) are described from mid-water fishes in the Indo-Pacific. The earliest metamorphic stage was found within the body cavity of the second host and indicates a double origin for the frontal processes of the cephalic holdfast in this species. A new species of Lophoura (family Sphyriidae) is described from a single female taken from a deep-water synaphobranchid eel caught in the North Atlantic. The new species, L. simplex, is characterised by the lack of any neck processes. Another sphyriid, Periplexis lobodes Wilson, is reported for the second time. It was found on a deep-sea alepocephalid belonging to the genus Rouleina in Fijian waters.

Animals↗
PubMed2001

Biogeography and phylogeny of Dermoergasilus Ho & Do, 1982 (Copepoda: Ergasilidae), with descriptions of three new species.

Three new species of Dermoergasilus are described from six species of grey mullet hosts. Dermoergasilus longiabdominalis n. sp. was found on Valamugil engeli (Bleeker) from the Philippines and Madagascar and on V. cunnesius (Valenciennes) from the Philippines and Mangalore, India. D. semiamplectens n. sp. occurred on Sicamugil hamiltoni (Day) from the Sittang River, Burma, on Liza subviridis (Valenciennes) and L. parsia (Hamilton Buchanan) from Calcutta, India, and on V. cunnesius (Valenciennes) from China. D. curtus n. sp. parasitised Rhinomugil squamipinnis (Swainson) from Alahabad, India. A key to the ten currently accepted species of Dermoergasilus is given. The biogeographical distribution of Dermoergasilus species is analysed and levels of host-specificity are surveyed within the genus. The phylogenetic relationships between the species of Dermoergasilus are also analysed.

Animals↗
PubMed2001

New species of Hatschekia Poche, 1902 (Copepoda: Hatschekiidae) parasitic on marine fishes of Kuwait.

Three new species of Hatschekia are described from the gill filaments of fishes taken in the Persian Gulf: H. seyi n. sp. from Heniochus acuminatus (Linnaeus), H. nodosa n. sp. from Lutjanus coccineus (Cuvier) and H. tanysoma n. sp. from L. fulviflamma (Forsskål). H. seyi differs from its congeners in having the cephalothorax longer than the trunk; H. nodosa, in having multiple nodules on the posterolateral margins of the trunk; and H. tanysoma, in having the trunk more than six times the length of cephalothorax and some pinnate setae on legs 1 and 2.

Animals↗