Postnatal growth and development in Sorex unguiculatus.

Abstract

The postnatal growth period is of central interest for an understanding of the life histories of altricial mammals . Among the soricine shrews (Soricidae, Insectivora), however, there is only limited information available concerning the postnatal development of a few species (Crowcroft 1957;Harper 1977;Churchfield 1990;Innes 1994). In the long-clawed shrew Sorex unguiculatus Dobson, for example, there have been no reports of direct observations of postnatal growth and development although Okhotina (1984), Inoue (1990), and Nesterenko (1999) estimated the length of the postnatal period of this species, inferring from indirect observations. In the present paper, we describe our direct observations of the growth and development throughout the postnatal growth period of captive S. unguiculatus. Materials and methods A pregnant S. unguiculatus that had over-wintered was captured in the Experimental Forest of Forestry and Forest Products Research Institute in Sapporo on 31 August 2000.Immediately after capture, she was moved to a laboratory at the Institute of Low Temperature Science, Hokkaido University, Sapporo , where she gave birth to six neonates in the early morning of I September 2000.The family of shrews was kept in a semi-open house under natural conditions of temperature and daylight. A mixed paste diet (Ohdachi 1994) and water were supplied ad libitum. In addition the artificial diet was supplemented with living earthworms (Lumbricidae) or frozen silkworm (Bambyx man) pupae every day. At first, the mother and neonates were kept together in a plastic cage (35 em L x 20 em W x 25 em H), containing a wooden nest box, an exercise wheel, and sawdust on the floor (see Ohdachi 1994). They were moved, when the young became 23 days old, into a larger cage (65 em L x 35 cm W x 35 em H), containing four nest boxes with IO-cm deep soil covered with sawdust. Food and water trays were placed near each nest box. The young were separated from their mother and kept individually once they were 29 days old.Once neonates reached three days old they were weighed to the nearest 0.1 g using a portable electronic balance every second day. Body length was measured every third day by placing a neonate on a sheet of graph paper (I mm x I mm square). As individual siblings were not marked, individual growth could not be followed, except for those individuals iden tifiable by particular physical features. In this report, the sex of the newborn shrews was not determined .

Growth, development and maintenance of American water shrews (Sorex palustris) in captivity

“…Body mass began to plateau by day 23 (Fig. 2), comparable to that of long-clawed shrews and European water shrews (Vogel 1972a;Michalak 1987;Nesterenko and Ohdachi 2001), but substantially later than that observed for vagrant and masked shrews (16-17 days; Hooven et al 1975;Forsyth 1976). These data suggest that larger bodied shrews require an extended period of growth to attain adult mass compared to the cohorts of smaller bodied species.…”

“…Likewise, the eyes of vagrant and European water shrews reportedly open at 21, and between 20 and 24 days of age, respectively (Hooven et al 1975;Michalak 1987). However, the eyes of common, long-clawed and masked shrews open by days 9, 15 and 17-18, respectively (Forsyth 1976;Innes 1994;Nesterenko and Ohdachi 2001).…”

“…2). The rate of increase in mass of S. unguiculatus, S. cinereus and S. vagrans during similar stages in development ranged only from 0.20 to 0.23 g/day (Hooven et al 1975;Forsyth 1976;Nesterenko and Ohdachi 2001). The maximal rate of weight gain by S. palustris occurred from days 10 to 19 (0.67 ± 0.01 g/day), with shrews exhibiting an average mass of 10.94 ± 0.34 g (73% of adult body mass) by day 19.…”

“…Shrews constitute one of the more speciose mammalian families (335 recognized species; Wolsan and Hutterer 1998), yet only limited data regarding their postnatal growth and development are available (Vlasák 1972;Vogel 1972a;Hellwing 1973;Hooven et al 1975;Forsyth 1976;Nesterenko and Ohdachi 2001). From a comparative standpoint, American water shrews (Sorex palustris) provide a good model system to study ontogeny because they are one of the largest representatives of the Tribe Soricini ( ♂: 13-18 g,♀: 8-12 g; van Zyll de Jong 1983).…”

Peer Review #2 of "Osteohistology of Late Triassic prozostrodontian cynodonts from Brazil (v0.1)"

“…A deceleration in growth rate typically accompanies the onset of reproductive maturity in extant mammals that take several years to reach a large body size (Owens, Dubeski and Hanson, 1993;Köhler et al, 2012), but may occur after asymptotic size is reached in fast growing, very small mammals (e.g. the long-clawed shrew, Nesterenko and Ohdachi, 2001; grey mouse lemur, Castanet et al, 2004) or prior to this transition in very large taxa (e.g. elephant, Lee and Werning, 2008).…”