Macroscopic digestive anatomy of ring-tailed lemurs (Lemur catta), including a comparison of frozen and formalin-stored specimens

Abstract

Digestive tract measurements are often considered species-specific, but little information exists on the degree to which they change during ontogeny within species. Additionally, access to anatomical material from nondomestic species is often limited, with fixed tissues possibly representing the only available source, though the degree at which this material is representative in terms of dimensions and weight is debatable. In the present study, the macroscopic digestive tract anatomy (length of intestinal portions, and tissue weights of stomach and intestines) of n=58 Lemur catta (from neonates to 25 years of age) was quantified, of which 27 had been stored frozen and 31 fixed in formalin. Particular attention was paid to the caecum and the possible presence of an appendix. The intraspecific allometric scaling of body mass (BM)0.46[0.40;0.51] for total intestine length and BM0.48[0.41;0.54] for small intestine length was higher than the expected geometric scaling of BM0.33, similar to literature results on interspecific scaling. This difference in scaling is usually explained by the hypothesis that the diameter of the intestinal tube cannot increase geometrically, to maintain optimal absorption. Therefore, geometric volume gain of increasing body mass is accommodated by more-than-geometric length scaling. Literature describes L. catta as being variable with respect to the presence of an appendix. No appendix was found in specimens of the present study. The proportions of length measurements did not change markedly during ontogeny, indicating that proportions developed in the foetus are already representative for the adult animal. By contrast, width and tissue-mass scaling of the caecum indicated a disproportionate growth of this organ during ontogeny that was not reflected in its length. Compared to overall intraspecific variation, the method of storage (frozen vs. formalin) had no relevant impact on length or weight measurements.

Increased physical activity is not related to markers of cardiometabolic health in two lemur species

“…In gray mouse lemurs (Microcebus murinus), an agerelated decline in body mass occurs in captivity, but not in the wild(Hämäläinen et al, 2014). We found that adult body mass did not decline with age in ring-tailed lemurs, similar to results from wild and captive ring-tailed lemurs(Clauss et al, 2021;Koyama et al, 2008). Body fat percentage and adjusted TEE of ring-tailed lemurs did not change with age.…”

Gastrointestinal morphology and ontogeny of foregut‐fermenting primates

“…Indeed, comparisons of intestine length measurements between frozen ( n = 3) and formalin‐fixed material ( n = 3) indicated some degree of shortening during formalin storage (Hume, Jazwinski, & Flannery, 1993). However, based on a comparison with a larger sample size of Lemur catta intestines stored either frozen ( n = 27) or fixed in formalin ( n = 31), the method of preservation does not have a relevant impact on length or weight measurements (Clauss et al, 2021), suggesting little effects of storage method on our results. This is also supported by the generally good data fit with literature data based on specimens not fixated in formalin (Figure 13).…”

“…Lemur catta intestines stored either frozen (n = 27) or fixed in formalin (n = 31), the method of preservation does not have a relevant impact on length or weight measurements (Clauss et al, 2021), suggesting little effects of storage method on our results. This is also supported by the generally good data fit with literature data based on specimens not fixated in formalin (Figure 13).…”

“…The challenge of combining milk feeding with a composite stomach anatomy may also make foregut fermenters peculiar in the ontogeny of their digestive tract. Mammals that rely, as adults, on hindgut fermentation only can have the respective anatomical structures developed even before birth, even though they may somewhat increase disproportionately in size when used due to plant food ingestion (reviewed in Clauss et al, 2021). This is because a hindgut fermentation site will not interfere with auto‐enzymatic milk digestion, being located after the small intestine where the latter takes place.…”