Some Patterns of the Distribution of Bottom Fauna in the Indian Ocean

Neyman, A. A.; Sokolova, M. N.; Vinogradova, N.G.; Pasternak, F. A.

doi:10.1007/978-3-642-65468-8_42

Cited by 5 publications

(2 citation statements)

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“…The deep-sea floor of the Central Indian Basin (CIB) is known to harbour a remarkable benthic biodiversity (Neymann et al 1973;Parulekar et al 1982;1992Ingole et al 1992Ansari et al 1996Ingole et al 1999Ansari, 2000;Ingole et al 2000). However, there is very little information on deep-sea benthos of this area in relation to environmental parameters.…”

Section: Introductionmentioning

confidence: 99%

Response of deep-sea macrobenthos to a small-scale environmental disturbance

Ingole

Ansari

Rathod

et al. 2001

Deep Sea Research Part II: Topical Studies in Oceanography

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To assess the possible effect of nodule mining on deep-sea environment, the Indian Deep-sea Environment Experiment (INDEX) was undertaken in the Indian Basin. The present investigation is a part of the disturbance and recolonization study. Pre-and post-disturbance sediment samples were collected from 21 stations between 10 0 01' -10 0 03' S and 75 0 59' -76 0 02' E at water depths of 5300 -5350 m to assess the effect of benthic disturbance. There was a significant change in the composition and biomass of macrofauna after the disturbance. Post-disturbance vertical profiles indicated a 63% reduction in the numerical count in the top 0-2-cm layer and high aggregation of macrofauna in deeper (5-10-cm) sediment layer. The impact of the disturbance was severe, as the mean biomass of macrofauna was significantly reduced in the disturbed area, probably due to the displacement and /or mortality caused by the benthic disturber.

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Section: Introductionmentioning

confidence: 99%

Response of deep-sea macrobenthos to a small-scale environmental disturbance

Ingole

Ansari

Rathod

et al. 2001

Deep Sea Research Part II: Topical Studies in Oceanography

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“…Between 800 and 1000 m depth, at the base of the oxygen minimum zone, a greatly increased diversity and biomass of megafauna were detected (see Gage 1995 ;Levin et al 1997). Similar increases in biomass and diversity of organisms at the bottom of oxygen minimum zones have been reported in other regions (Neyman et al 1973 ;Wishner et al 1990Wishner et al , 1995Levin et al 1991). At a depth of approximately 1000 m aggregations of spider crabs were photographed at densities of up to 137 m −# (Bett 1995).…”

Section: Discussion (A) Distribution and Biology Of Encephaloides Armstrongimentioning

confidence: 58%

The population biology and genetics of the deep–sea spider crab,Encephaloides armstrongiWood–Mason 1891 (Decapoda: Majidae)

Creasey

Rogers

Tyler

et al. 1997

Phil. Trans. R. Soc. Lond. B

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Numerous specimens of the majid spider crab, Encephaloides armstrongi , were sampled from six stations (populations) between 150 and 650 m depth, on the continental slope off the coast of Oman. This extended the known geographic and bathymetric range of E. armstrongi , which is now known to occur along the continental margins of the northern Indian Ocean from the western coast of Burma to the coast of Oman. This band–like distribution is contiguous to the oxygen minimum zone in this region. The biology and genetics of populations of Encephaloides armstrongi separated by depth were studied. The overall sex ratio of the E. armstrongi sampled was male–biased ( p < 0.01; 3.3 males: 1 female; S o = 0.538). However, sex ratio varied both between populations ( p < 0.01) and between size classes of crabs. Size frequency analysis indicated that the male and female crabs consisted of at least two instars, one between 6 and 16 mm carapace length and one between 16 and 29 mm carapace length, which probably represented the terminal (pubertal) moult for most individuals. Accumulation of female crabs in the terminal instar probably caused the variation of sex ratio with size classes. Some male crabs grew to a larger size (up to 38 mm carapace length), possibly as a result of maturity at later instars. Length frequency distribution was significantly different between sexes (one–way ANOVA p < 0.001). Within sexes, length frequency distributions varied between different populations. In both male and female Encephaloides armstrongi the individuals from a single population located at 150 m depth were significantly smaller than individuals at all other stations and were considered to represent a juvenile cohort. For female crabs no other significant differences were detected in length frequency between populations from 300 m to 650 m depth. Significant differences in length frequency were detected between male crabs from populations between 300 and 650 m depth. Horizontal starch gel electrophoresis was used to detect six enzyme systems coding for eight loci for individuals sampled from each population of Encephaloides armstrongi . Genetic identity ( I ) values between populations of E. armstrongi ( I = 0.98−1.00) were within the normal range for conspecific populations. Observed heterozygosity ( H o = 0.080−0.146) was lower than expected heterozygosity ( H e = 0.111−0.160), but in the normal range detected for eukaryotic organisms. F –statistics were used to analyse between population ( F ST ) and within population ( F ) genetic structure. For both male and female E. armstrongi significant genetic differentiation was detected between the population located at 150 m depth and all other populations. Analyses of F IS and F ST , excluding the 150 m population indicated that for female E. armstrongi there was no significant structuring within or between populations. For male E. armstrongi significant heterozygote deficiencies were detected within populations and significant genetic differentiation between populations. The most likely explanations for the observations of the present study are: the population of Encephaloides armstrongi located at 150 m depth represented a juvenile cohort that is genetically distinct from deeper populations; female E. armstrongi formed a single population between 300 m and 650 m depth in the sampling area; male E. armstrongi were from two or more genetically distinct populations which are represented by different numbers of individuals at stations between 300 m and 650 m depth. This caused the observed significant differences in morphology (size distribition) and allele frequencies of male populations. It is likely that E. armstrongi exhibits gender–biased dispersal and that the crabs collected between 300 m and 650 m depth formed spawning aggressions. This also explains the bias in sex ratio of individuals sampled in the present study.

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