Reversal of a hallmark of brain ageing: lipofuscin accumulation.

The prospect of removing cellular deposits of lipofuscin is of considerable interest because they may contribute to age related functional decline and disease. Here, we use a decapod crustacean model to circumvent a number of problems inherent in previous studies on lipofuscin loss. We employ (a) validated lipofuscin quantification methods, (b) an in vivo context, (c) essentially natural environmental conditions and (d) a situation without accelerated production of residual material or (e) application of pharmacological compounds. We use a novel CNS biopsy technique that produces both an anti-ageing effect and also permits longitudinal sampling of individuals, thus (f) avoiding conventional purely cross-sectional population data that may suffer from selective mortality biases. We quantitatively demonstrate that lipofuscin, accrued through normal ageing, can be lost from neural tissue. The mechanism of loss probably involves exocytosis and possibly blood transport. If non-disruptive ways to accelerate lipofuscin removal can be found, our results suggest that therapeutic reversal of this most universal manifestation of cellular ageing may be possible.

Cuticular Photophores of Two Decapod Crustaceans, Oplophorus spinosus and Systellaspis debilis.

The organization, ultrastructure, growth, and development of two types of cuticular photophore in oplophorid shrimps (Oplophorus spinosus and Systellaspis debilis) are described. Photophores located in the third maxilliped consist of a unit structure comprising a single photocyte and associated pigment cells. Reflecting pigment cells contain white pigment and form an apical cap above the photocyte; sheath cells contain red carotenoid pigment and form a light-absorbing layer around the photophore. Photophores located on the pleopods are compound structures comprising many photocytes. They also contain the same types of pigment cell that are found in the unit photophores of the maxilliped. Paracrystalline bodies at the apical ends of the photocytes in both types of photophore are thought to be associated with light generation. Both types of photophore have mechanisms for tilting in the pitch plane. In the maxilliped, the apices of the photophores are connected to a ligament that has its origin in the propodus. Flexion or extension of the dactylus displaces the ligament, which tilts the photophores synchronously. The cuticular window beneath each photophore remains stationary. The tilt mechanism of the pleopod photophores is quite different, and depends upon muscular contraction. A main and an accessory longitudinal muscle cause backwards rotation of the photophore by deforming the cuticle surface. A loop muscle that passes around the anterior face of the photophore causes forward rotation. The two mechanisms optimize the use of the photophores in ventral camouflage. They allow photophore rotation to compensate for changes in the shrimp's orientation in the plane of pitch and thus maintain the ventral direction of the luminescence.

Comparative Morphology of the Eyes of Postlarval Bresiliid Shrimps From the Region of Hydrothermal Vents.

The structure and ultrastructure of the eyes of postlarval vent shrimps provisionally designated `Alvinocaris' and `Chorocaris' are described. The eyes of the postlarval `Alvinocaris' are cylindrical, borne on short stalks, and contain closely packed rhabdoms. The ommatidia lack dioptric apparatus and have rhabdoms extending almost to the cornea. The rhabdoms consist of orthogonal layers of microvilli typical of crustacean rhabdoms. The eyes of the `Chorocaris' are similar, but the rhabdom layer extends back through the reduced eyestalks and covers some of the dorsal surface of the cephalothorax. The rhabdoms from both the anterior and the thoracic regions consist of layered microvilli. The eyes of a slightly smaller postlarval vent shrimp, termed `Type A', differ. Although clearly related to the other vent shrimps, Type A has stalked eyes held at an angle to the head. The eye displays a gradient of ommatidial development, with the older ommatidia closely resembling those seen in the other postlarval types. Between the cornea and the rhabdom layer, the youngest ommatidia possess quadripartite crystalline cones similar to those seen in related families of caridean shrimps; these are absent in the more mature ommatidia. The external structure of the anterior and thoracic eyes of juvenile Rimicaris exoculata (after settlement at the vent site) is also described. Juveniles up to 9 mm in carapace length have anterior corneas similar to those seen in postlarvae, whereas in larger specimens the corneas are progressively replaced by an ocular plate.