Regeneration in the sea cucumberLeptosynapta. I. The process of regeneration

✍ Scribed by Smith, Gerald N.

• Publisher: John Wiley and Sons
• Year: 1971
• Tongue: English
• Weight: 911 KB
• Volume: 177
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1401770306

✦ Synopsis

Abstract

The process of regeneration of a lost posterior by an anterior piece of the sea cucumber Leptosynapta crassipatina (Apoda) is described.

The methods used were histological study and direct observation of regenerating animals. Vital stains were used to define growth patterns.

The regeneration process is morphallaxis; the residual tissues are remodeled to produce a smaller but functionally complete animal. The process can be seen by sing the divisions of the gut as linear markers.

Leptosynapta has a straight, unlooped digestive tract consisting of three externally visible division: the esophagus, the stomach and the intestine. The esophagus and stomach are suspended in the dorsal mesentery; the intestine is suspended in the ventral mesentery.

Near the middle of the animal, the mesenteric attachment of the gut to the body wall changes from dorsal to ventral and the digestive tract crosses the coelomic cavity. This is the crossover point.

In anterior pieces, produced by sectioning animals just anterior to the crossover point the posterior end of the stomach crosses the coelom creating a new crossover point near the amputation surface. This crossover point then moves anteriad to restore the normal location of a crossover. crossing over is accompanied by redifferentiation, so that normal gut proportions and structure are attained.

Crossover is faster at more posterior levels of transection. The vital stain technique showed a region of elongation just anterior to the amputation surface. No elongation was ever shown within, or just posterior to, the oral complex. Histological study revealed low mitotic activity in all parts of the oral complex.