The cephalopod digestive gland (DG) is responsible for enzyme production as well as nutrient and lipid storage. Octopus maya (Mollusca: Cephalopoda) is a holobenthic octopus species with aquaculture potential. To develop a balanced food for the rearing of this octopus, it is necessary to understand its digestive physiology. We performed histological studies on the structural change of the DG (cytological ontogeny) associated with age (from 0 to 30 d posthatching, DPH) and food (postprandial change in 120 DPH juveniles). Early ontogeny of DG was defined in 3 stages: (1) yolk platelets stage (0 to 5 DPH), (2) transition stage (6 to 10 DPH) and (3) heterolysosomes (food reserves) stage (>12 DPH). In Stage 1, the DG had anatomically undifferentiated tubules, but was filled with yolk platelets. The tubular structures developed lumen by 5 DPH. Stage 2 (starting at 6 DPH) corresponds to mixed exogenous and endogenous feeding. At that time, the yolk platelets were gradually consumed until completely exhausted at 9 DPH. At the onset of Stage 3, the DG structure was completely tubular, exhibiting digestive cell microvilli and other cellular features typical to octupus DGs. During exogenous feeding (12 DPH and onward), acidophilic secretory lysosomes, heterolysosomes and some heterophagosomes appeared on DG cells. O. maya has long digestive cycles in which the extracellular and intracellular digestion can take up to 8 h. Although the ecological implications of this information for aquaculture will still have to be proven, results demonstrated that O. maya is an energetically efficient species and thus suitable for rearing in captivity.

This study aimed to evaluate the nutrient digestibility of growing rabbits fed diets with different levels of either Leucaena leucocephala (LLM) or Moringa oleifera (MOLM) leaf meals and also to compare total collection and TiO2 marker methods for estimating digestibility. A total of 30 California growing rabbits (1.81±0.19 kg live weight on average) were randomly distributed into five experimental groups of six rabbits each and were housed in individual cages. The groups were control, 30% LLM, 40% LLM, 30% MOLM, and 40% MOLM. All groups received pelleted diets for two weeks; diets also contained 4 g/kg titanium dioxide as dietary marker. Daily feed intake was recorded during the whole experimental period and total feces were collected daily and weighed individually during four days. The results showed that there were no difference (p>0.05) in feed, dry matter (DM), organic matter (OM), crude protein (CP), digestible energy, and crude fiber (CF) intake between the control group and the other experimental groups. The apparent digestibility values of DM, OM, CP, CF, acid detergent fiber, and gross energy were the highest for control group (p = 0.001), meanwhile MOLM diets had generally higher nutrient digestibility coefficients than LLM diets. Increasing the inclusion level of leaf meal in the diet from 30% to 40% improved the digestibility of CF from 45.02% to 51.69% for LLM and from 48.11% to 55.89% for MOLM. Similar results for apparent nutrient digestibility coefficients were obtained when either total collection or indigestible marker method was used. In conclusion, the digestibility of MOLM containing diets were better than LLM diets, furthermore TiO2 as an external marker could be used as a simple, practical and reliable method to estimate nutrients digestibility in rabbit diets.

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