Specific features of mandible structure and elemental composition in the polyphagous amphipod Acanthogammarus grewingkii endemic to Lake Baikal.
BACKGROUND
In crustaceans, several mechanisms provide for the mechanical strength of the cuticular "tools" (dactyli, claws, jaws), which serve to catch and crush food objects. Studies on the mandibles of the endemic Baikal amphipod Acanthogammarus grewingkii by means of electron microscopy and elemental analysis have revealed specific structural features of these mouthparts.


METHODS
The fine structure of the mandible has been studied by means of SEM, TEM, and AFM; methods used to analyze its elemental and phase composition include XEPMA, XPS, SEM-EDS analysis, and XRD.


CONCLUSIONS
Functional adaptations of the mandible in A. grewingkii provide for the optimum combination of mechanical hardness and fracture resistance, which is achieved due to a complex structure and composition of its cutting parts. Teeth of the mandible are covered by a thin layer of silica (10-20 µm). Their epicuticle is characterized by a high density, consists of three layers, and increases in thickness toward the tooth apex. The epicuticle is enriched with Br, while the concentrations of Ca and P reach the peak values in the softer internal tissues of the teeth. These data broaden the view of the diversity of adaptation mechanisms providing for the strengthening of cuticular "tools" in crustaceans.
Limnological Institute of the Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia. irinam@lin.irk.ru
Irina V
IV
Mekhanikova
Dmitry S
DS
Andreev
Olga Yu
OY
Belozerova
Yuri L
YL
Mikhlin
Sergey V
SV
Lipko
Igor V
IV
Klimenkov
Vladlen V
VV
Akimov
Valeriy F
VF
Kargin
Yelena V
YV
Mazurova
Vladimir L
VL
Tauson
Yelena V
YV
Likhoshway
D033304:Amphipoda / Q000033:anatomy & histology* / Q000737:chemistry*; D000818:Animals; D060106:Lakes; D008334:Mandible / Q000033:anatomy & histology / Q000737:chemistry / Q000648:ultrastructure; D014070:Tooth / Q000737:chemistry / Q000648:ultrastructure