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Volume 86 - Issue 6 - December 2006

Journal of the Marine Biological Association of the United Kingdom Volume 86 - Issue 6 -
Contents

Page 2 of 2

Research Article

  • The effects of Splanchnotrophus willemi infecting Ancula gibbosa (Gastropoda: Opisthobranchia: Nudibranchia)

  • Helen C. Marshall, Peter J. Hayward
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1437-1441

  • The parasitic copepod, Splanchnotrophus willemi, is recorded infecting the nudibranch Ancula gibbosa for the first time in the UK. Seven out of twenty Ancula gibbosa sampled from Mumbles, Swansea, UK, were found to be infected with S. willemi. Light microscopy was used to investigate the effects of S. willemi on its host. In six hosts the internal damage caused was minimal. However, in one host the damage was extensive resulting in the disintegration of the digestive and reproductive viscera. One other A. gibbosa not parasitized, exhibited similar damage and it was postulated that this animal may have survived infection. In all cases of infection there was never more than one male or one female S. willemi present.

  • Assessment of trophic relationships between symbiotic tropical ophiuroids using C and N stable isotope analysis

  • D. Fourgon, G. Lepoint, I. Eeckhaut
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1443-1447

  • Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiuroids, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess the potential benefit obtained by the symbiotic Ophiomastix venosa juveniles. A tracer experiment was also carried out to clarify the contribution of algae to the nitrogen uptake amongst the tested ophiuroids. Our results suggest that Ophiocoma scolopendrina adults occupy a higher position in the food web than Ophiomastix venosa and mainly feed on neuston. In contrast, O. venosa adults feed on the alga Sargassum densifolium and on organic matter associated with sediment. Free juveniles and symbiotic juveniles of O. venosa have intermediate δ13C values between both adult species. The high proportion of 13C in the symbiotic juveniles compared to the one in their conspecific adults indicates that their diet slightly differs from the latter and is closer to that of Ophiocoma scolopendrina. This raises the hypothesis that symbiotic juveniles steal neuston from their associated host, O. scolopendrina.

  • Abundance of demersal fish resources in the Persian Gulf and Oman Sea

  • T. Valinassab, R. Daryanabard, R. Dehghani, G.J. Pierce
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1455-1462

  • We report on results of a trawl survey during 2003–2004 to assess the abundance of demersal fish resources in the Persian Gulf and Oman Sea. Samples were taken at a total of 316 trawl stations selected following a stratified random procedure. Catch rates (catch per unit area, CPUA) and total biomass were estimated. Total demersal fish biomass was estimated to be approximately 73,000 tonnes in Persian Gulf waters and approximately 39,000 tonnes in the Oman Sea. The lowest CPUA was recorded in the west of the study area (stratum A, approximately 1700 kg/n.m.2) and the highest in the east (stratum Q, 13943.4 kg/n.m.2), although density of commercially important species was higher in the central area (stratum K). Catch rate and biomass varied significantly in relation to seabed depth. Commercially important demersal species made up around 60% of the estimated total biomass. The most abundant species groups were rays, catfish, grunts, nemipterids and carangids. Several important species (e.g. silver pomfret, croakers and sharks) appear to have declined since the late 1970s while others, such as rays and catfish, have increased.

  • PCR–RFLP analysis of mitochondrial DNA for identification of Rutilus rutilus caspicus populations on the southern coast of the Caspian Sea, Iran

  • Sohrab Rezvani, Amin Eimanifar, Reza Aghili, Faramarz Laloei
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1463-1467

  • Genetic analysis using restriction fragment length polymorphisms (RFLPs) of cytochrome b in mtDNA was made to clarify genetic variations among two Iranian Rutilus rutilus caspicus populations of commercial importance from the southern coast of the Caspian Sea. Polymorphism was detected using six restriction enzymes and a total of six composite haplotypes were identified. Four haplotypes were rare occurring only once in two regions (west and east of the southern Caspian Sea). Nucleotide and haplotype diversities were higher in the south-west region of the Caspian Sea (π=3.43%, h=23.3).The nucleotide divergence between the two populations was low (0.064%). The test for heterogeneity of composite haplotype frequencies gave no significant outcome for all samples (χ2=0.137, P≤0.05). The results indicate that significant attention should be paid to the genetic characterization of R. rutilus caspicus populations for conservation of their genetic pools and aquaculture policies at the coastlines of the Caspian Sea.

  • Hypoxic tolerance of Chinese black sleeper Bostrichthys sinensis embryos at heartbeat stage

  • Shixi Chen, Wanshu Hong, Wei Zhou, Qiyong Zhang
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1473-1476

  • Tolerance of hypoxia in Chinese black sleeper (Bostrichthys sinensis) embryos at heartbeat stage was examined at different oxygen concentrations. Embryonic response to hypoxic conditions was expressed in terms of the intensity of variation in heartbeat rate (V). Exposure of the embryos at 25°C to 0.5, 1.0 and 1.5 mg/l dissolved oxygen (DO), caused bradycardia, which was developed within the first 10 min of hypoxia, followed by a plateau, and lasted until termination of the hypoxia. The V values were significantly affected by DO concentrations (P<0.01). Exposure of the embryos to 0.2 mg/l DO at 25°C caused a periodic heartbeat (including a period of heartbeat and a period of silence). This phenomenon was first recorded in the present study. During the period of heartbeat, the heartbeat rates were faster at first (147±5 beats per min), and then decreased gradually until the period of silence. As the exposure time increased, the duration of heartbeat was prolonged significantly from 43.4±2.4 second to 126.2±8.2 second (P<0.01), and the duration of silence was also prolonged significantly from 68.0±5.5 second to 247.9±11.5 second (P<0.01). At the beginning of exposure, the primary heartbeat rates displayed tachycardia, and their V values were significantly lower than the V values of average heartbeat rates (P<0.05). However, the V values were not significantly different between primary heartbeat rate and average heartbeat rate after 90 min exposure (P>0.05).

  • Desseria zei sp. nov. (Adeleorina: Haemogregarinidae) infecting Zeus capensis from deep waters off the south and west coasts of South Africa

  • N.J. Smit, A.J. Davies
  • Published online by Cambridge University Press:
    15 December 2006, pp. 1477-1480

  • Blood films from a marine fish, the Cape Dory (Zeus capensis), trawled at depths between 149 and 389 m off the south and west coasts of South Africa, contained a new species of haemogregarine, Desseria zei sp. nov. The apicomplexan, found in 25/97 fish from the two regions, was generally intra-erythrocytic. Parasitaemia was usually low, but attained infection levels of 1/10 erythrocytes in one fish. The parasite stages were all gamonts and monomorphic, but likely varied in maturity; they were 3.3–4.5 μm wide by 14.7–18.3 μm long, curved with bluntly pointed ends, and existed singly within erythrocytes, or in pairs in the heavy infection. Their cytoplasm was deep blue, granular, and stained deeply at the anterior and sometimes, posterior extremities. Two or three vacuoles occurred in the cytoplasm between the anterior cap and the gamont nucleus, which was positioned in the posterior third of the parasite body. Gamonts lay close to the host cell nucleus, often curved around it. Distortion of host cells and host nucleus displacement occurred when single gamonts curved away from the host nucleus, or if they were paired. A few extracellular gamonts were observed, occasionally associated with the remnants of the erythrocyte nucleus.

Other

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