Loading...
Please wait, while we are loading the content...
Similar Documents
Natural History and Copulatory Behavio R of the Spiny Orbweaving Spide R Micrathena Gracilis ( Araneae , Araneidae )
| Content Provider | Semantic Scholar |
|---|---|
| Author | Bukowski, Todd C. |
| Copyright Year | 2004 |
| Abstract | We examine copulatory behavior and the reproductive natural history of the spiny orb weaver, Micrathena gracilis . Censuses were conducted on free-ranging, individually marked spiders . After molting to adulthood, males induct sperm into their palps and then search for mates . Females inhabit solitary, individually-constructed webs . Males preferentially remain with penultimate-instar females, thos e about to molt and mate for the first time . After a female molts and constructs a viscid spiral, males buil d mating threads on which they court . After copulating, the male must dismount and reapproach the female to inseminate her second reproductive tract . Two copulations are therefore required for a complete mating between male and female . Some males, however, obtained only one copulation and two males often copulated with a given female . Staged encounters in the field revealed the important observation that whe n a male did copulate twice with a female, the duration of the second copulation was more than twice a s long as the first . Shortly after the second copulation, the male inducted sperm into the palps and moved away. Females remained sexually receptive throughout their lives and apparently mated with any male . Females oviposited about 30 days after molting and mating . Egg sacs were cryptic in appearance and ye t clutch mortality was high . Copulatory behavior is discussed in relation to this reproductive natural history . Spiders offer an intriguing model for th e study of reproduction . To begin, the sexes often differ dramatically in both morphology and behavior (Foelix 1980 ; Vollrath & Parker 1992) . The female orbweaver, for example, i s generally a relatively large, sedentary predato r while the adult male is smaller and, at leas t as an adult, a wanderer. The shape and presence and arrangement of sperm intake and fertilization ducts of the female spider's reproductive tracts is thought to have a strong influence on male sexual maturation rates and the pattern of cohabitation with females . Conduit spermathecae, those with separate insemination and fertilization ducts (entelegynes) , are thought to promote a first male advantag e in fertilization due to a serial ordering of sperm and a first-in/first-out usage pattern (Austad 1984) . Consequently, males of suc h species usually mature before females and co habit with penultimate-instar females approaching the final molt and sexual maturit y (Christenson & Goist 1979 ; Robinson & Robinson 1980 ; Jackson 1986; Watson 1990 ; Dodson & Beck 1993) . Cul-de-sac spermathecae, those with common insemination and fertilization ducts (haplogynes), are thought to promote a last male advantage because the sperm from the last mating are nearer to the exit of the duct and a last-in/first-out usage pattern (Austad 1984) . This is supported by Kastner & Jacobs (1997 ; but see Eberhard et al . 1993) . In this case there should be no selective pressure for early male maturation and preferential cohabitation with females approaching sexual maturity . Males mature at about the same time or after females and cohabitation with juvenile females is not noted (Huff & Coyle 1992 ; Eberhard et al . 1993) While the morphology of the female reproductive tract may influence male advantage patterns for fertilization of a female's eggs , sexual maturation rates and male cohabitation patterns, the relationship between the female' s reproductive tract morphology and copulator y behavior is uncertain. It is known that male s of species with cul-de-sac spermathecae ofte n simultaneously insert both palps during copulation (Foelix 1980) . The patterns of palpal insertion and duration of copulation amon g species with conduit spermathecae show extreme variability within and between species (Robinson & Robinson 1980 ; Elgar 1995) . Males can insert one palp several times befor e |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.americanarachnology.org/JoA_free/JoA_v25_n3/JoA_v25_p307.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
