Scavenging Amphipods

Dillenia  pentagyna Roxb.  is  a  medium  sized  tree  belonging  to  the
family Dilleniaceae. It is commonly known as Kaihzawl in Mizoram.
Traditionally,  a  decoction  prepared  by  boiling  the  bark  of  Dillenia
pentagyna Roxb.  is  used  for  various  stomach  ailments  and
inflammatory  diseases.  Preliminary  phytochemical  screening  and
evaluation  of  in-vitro  antioxidant  activity  were  carried  on  the
methanolic  extract  obtained  from  the  bark  of Dillenia  pentagyna
Roxb.  The  presence  of  flavanoids,  triterpenoids,  tannins,  alkaloids,
glycosides,  steroids  and  carbohydrates  was  indicated  by  the  tests
conducted.  The  in-vitro  antioxidant  activity  was  evaluated  using
DPPH radical scavenging activity, Reducing power, Hydroxyl radical
scavenging  activity  and  determination  of  total  phenolic  and
flavanoids  content.  Ascorbic  acid,  BHA,  Gallic  acid and  Quercetin
were used as reference standards. The methanolic extract of the plant
shows strong antioxidant activity camparable to that of the reference
standards.

The fossil giant amphipod Rosagammarus minichiellus n. gen., n. sp. occurs in Triassic limestone (Luning Formation, west-central Nevada) in association with giant ichthyosaurs (Shonisaurus sp.) and the deep-water trace fossil Protopaleodictyon ichnosp. Fossil pereion and pereiopod morphology suggest affinities with the Acanthogammaridae, a freshwater amphipod family largely endemic to Lake Baikal. The large size (17 cm) of the Triassic amphipod shows that supergiant, deep marine amphipods comparable to modern Alicella gigantea Chevreux, 1899 were extant during the early Mesozoic. By analogy with Alicella gigantea, Rosagammarus minichiellus n. gen., n. sp. was a necrophagous, benthopelagic scavenger that fed on ichthyosaur and other sea floor carcasses. Rosagammarus minichiellus n. gen., n. sp. appears to be the oldest known fossil amphipod. This discovery extends the known geological range of Amphipoda by at least 170 million years.

The life history and fecundity of five shallow-water lysianassoids from the Saint Lawrence Estuary were examined. Orchomenella minuta and Or. pinguis are annual and iteroparous (two broods), Psammonyx terranovae is iteroparous (two broods) and probably biennial, and Anonyx sarsi and Onisimus litoralis are biennial and semelparous. Females of A. sarsi and On. litoralis cease feeding on bait shortly before or after oviposition, whereas females of the iteroparous Or. pinguis stop feeding on bait only when broods are in the latest stages of embryo development. These ontogenetic changes may result from gut constriction caused by developing ovaries and broods, or may be due to behavioural changes. Data on the fecundity of the Lysianassoidea are reviewed, and it is concluded that deep-living species are probably much less fecund than shallow-living species. Anonyx nugax, Or. pinguis, and A. sarsi are more fecund than other lysianassoids, possibly because of their high-risk carrion-feeding and suprabenthic foraging activities.

The life history and fecundity of five shallow-water lysianassoids from the Saint Lawrence Estuary were examined. Orchomenella minuta and Or. pinguis are annual and iteroparous (two broods), Psammonyx terranovae is iteroparous (two broods) and probably biennial, ...

A large area of axis sediment (>500 m2) may be annually removed from the head of Monterey Submarine Canyon with the first onshore storm of the fall/winter storm season. In this scenario, flushing events are followed by accumulation of sediment and organic debris—especially macro-algae—in the shallow axis. Net accumulation of this fill material increases during the calmer spring and summer until the next fall-flushing. The benthic community at a canyon axis station was characterized by highly fluctuating populations of opportunistic polychaete worms and gammarid amphipods, primarily Capitella spp., Armandia brevis, and Orchomene pacifica. The canyon axis community was very different from communities living at two other stations where sudden flushing does not occur—an adjacent sloping-wall station and a sandflat station. Sloping-wall and sandflat stations harbored more and longer-lived species, larger individuals, and a less-variable population structure during a year of sampling. The Loma Prieta earthquake in the fall of 1989 triggered small sediment slumps on the canyon walls, but it did not trigger axis-flushing. The usual seasonal flushing of the axis occurred 2 weeks after the earthquake with the arrival of the first storm. Benthic communities were reduced in abundance inside earthquake-induced slumps; however, the slumped areas were rapidly colonized by Prionospio pygmaea, a polychaete opportunist common to the sandflat. Surprisingly, the physical and biological impacts of the earthquake were much less severe than the seasonal axis-flushing associated with storms. Observations of sediment-flushing combined with measurements of benthic community changes in Monterey Canyon head represent a step towards an ecological model of mass wasting with implications for the continental shelf and slope and possibly the deep sea. © 1997 Elsevier Science Ltd