Functional and phylogenetic interpretation of the forelimb myology of two South American carnivorans, the ring-tailed coati (Nasua nasua) and crab-eating raccoon (Procyon cancrivorus).

A comparative analysis of the forelimb myology of two neotropical procyonids (Nasua nasua and Procyon cancrivorus) was performed to assess how observed differences in their myological configuration would be related to their diverse ecological behaviors and phylogeny. Although both species are associated with the arboreal substrate, N. nasua is a more agile climber that usually digs; whereas P. cancrivorus spends most of its time on the ground foraging, climbing on the trees as shelter and is a good swimmer. Here, myological descriptions, muscle maps, phylogenetic optimizations, and muscle mass data of the forelimb of these two procyonids are presented. The main functional muscular groups are discussed in a comparative framework with other carnivorans that present a wide ecological diversity. Also, muscular characters were mapped onto a phylogeny to explore their evolution and to obtain ancestral state reconstructions. Results indicate clear myological differences among the two neotropical procyonids associated with their ecological preferences. One of the most remarkable anatomical differences is the arrangement and relative mass of the extrinsic musculature, mainly the musculus rhomboideus and the delto-pectoral complexes. In Nasua nasua, these suggested a greater stability in their shoulder girdle for climbing and digging and probably would provide stronger neck and head movements when they use them for foraging on the ground. Conversely, P. cancrivorus has a different extrinsic muscular configuration, which would allow an increment on the stride length and faster movements of the forelimb associated with more frequent terrestrial gaits. Also, significant differences are observed in the distal musculature, associated with strong movements of forepaws when climbing and digging in N. nasua; whereas, P. cancrivorus configuration suggested precise forearm and digits movements, related to manipulation of food items when they are catching prey or feeding. Most of the codified features of P. cancrivorus would reflect retention of plesiomorphies acquired in the common ancestor of caniforms or arctoids, whereas N. nasua shows derived traits, particularly in the proximal forelimb region. The present work increases the information available on the myology of these particular taxa and extant generalized arctoid models in general. The analyses presented here will be useful both for other comparative myological studies (morpho-functional and phylogenetic) and for muscular reconstruction in extinct procyonids, as well as other carnivorans.

Comparative osteology and functional morphology of the forelimb of Cyonasua (Mammalia, Procyonidae), the first South American carnivoran.

Extant procyonids only inhabit the Americas and are represented by six genera (Procyon, Nasua, Nasuella, Bassaricyon, Potos, and Bassariscus); all of them, except Bassariscus, are present in South America. The first records correspond to the early Miocene in North America (NA) and the late Miocene in South America (SA). Cyonasua was the first carnivoran to enter SA from NA, before the Great American Biotic Interchange, and went extinct in the early middle Pleistocene. This extinct procyonid is recorded in several localities of Argentina, and also in Venezuela. Paleobiological studies of procyonids are interesting from evolutionary and biogeographical viewpoints. In this study, the pectoral girdle and forelimb of 10 specimens of Cyonasua are described and compared with extant South American procyonids using a qualitative approach. Additionally, four functional morphology indexes were calculated for them and compared with an ecologically diverse sample of living carnivorans. Results indicate that Cyonasua most resembles Nasua nasua and Procyon cancrivorus, even though the extinct procyonid possessed peculiar features. Cyonasua had robust and relatively short forelimb bones, with strong stabilized joints, and movements associated with the sagittal plane, which suggest a tendency toward terrestrial habits, related to their ability to resist relatively high bending and shearing stresses. However, some features indicate a freedom in their range of movements, with moderate supination ability, compatible with climbing. When combined with previous analyses of dietary habits and estimated body mass, the morphology of Cyonasua would be well suited for digging and prey manipulation, allowing them to prey on small and relatively large-sized vertebrates, as well as to avoid some of the predators that were dominant in the Cenozoic of South America.

Effect of temperature, photoperiod, flooding, and drying on the hatching pattern of the eggs of Strelkovimermis spiculatus (Nematoda: Mermithidae).

We assessed the number of Strelkovimermis spiculatus preparasites obtained from a known initial number of nematode eggs and the effect of abiotic conditions (temperature, photoperiod, flooding-drying) on the number of emerged preparasites. Two egg groups were maintained: one continuously flooded, another with flooding-drying cycles (every 15, 30, 60 days). Each egg group was studied at 25°C and 14:10 (L:D) and 16°C and 12:12 (L:D). The flooded eggs contained a higher overall percentage of S. spiculatus preparasites compared to the wet-dry-cycle eggs. The conditions of continuous flooding at 16°C and 12:12 (L:D) produced the maximum percent of emerged J2s (30±15%). Preparasites were recorded by 7 (25°C) and 14 (16°C) days, suggesting this period as the minimum time for embryonic development. The preparasite-emergence time observed from the same flooded-egg batch (98 and 112 days at 25°C and 16°C, respectively) suggested a nonsynchronous hatching, possibly through nonuniform egg embryonation. The time of exposure to drought in the assays did not significantly affect the total average percentage of J2s obtained at 25°C and 14:10 (L:D), whereas at 16°C the number of emerged J2s diminished with a prolongation of the drying period. The oviposition period was also recorded only at 16°C and 12:12 (L:D): S. spiculatus eggs were detected at 12.6 days after postparasite emergence, and oviposition was complete at 51days under those conditions. We propose a flooding schedule to optimize the mass-rearing of S. spiculatus.