MIGRATION AND REPRODUCTION OF THE WOOD‐BORING ISOPOD, LIMNORIA, IN SOUTHAMPTON WATER

Abstract

ABsTRAcrThree species of Limnoriu occur together in Southampton Water. Migration began at a water temperature rising through 10°C in L. quaclripunctntn and L. Zignorum and through 15°C in L. tripunctata, Migratory activity followed the water temperature in L. tripunctata but declined in L. Zignorum before the highest tcmpcraturcs were reached. The migratory behavior of L. quadripunctata resembled that of L. tripunctata at one site and that of L. Zignorum at another. Overcrowding as a cause of migration was not supported.Migration was confined to large, sexually mature adults, excluding gravid females. The first migrants were predominantly male, and in L. Zignorum about twice as many malts as females migrated.Reproduction showed a marked increase in the summer, beginning at a water temperature of 10°C in L. quadripunctata and L. lignorum and of. 12°C in L. tripunctata. L. quadripunctutu differed from other species in being the only one in which the avcragc brood size of post-migrants was significantly greater than that of non-migrants, and in which a significant increase in brood size with body size occurred.No seasonal change in brood size was demonstrated in any species. Widely separated developmental stages were frcqucntly found in the same brood. The duration of the egg stage was longer than that of the embryo which in turn exceeded that of the larval stage.

Reproduction, growth and bionomics of Dynamene bidentata (Crustacea: Isopoda)

“…There is, too, some variation in the stage of development of embryos in about 25 % of brood pouches, with embryos at the posterior end often being more advanced than the others. This differs from the general rule among isopods that the brood is uniform (Green, 1965), but agrees with exceptional species such as Idotea (Howes, 1939;Kjennerud, 1950), and Limnoria (Eltringham & Hockley, 1961).…”

Breeding Biology and Seasonal Population Changes ofJaera Nordmanni NordicaLemercier [Isopoda, Asellota]

“…1974 Total nos. same stage of morphological development as is the general rule for isopods (Green, 1965;Jones, 1970;Jones & Naylor, 1971), though exceptions have been recorded (Howes, 1939;Kjennerud, 1950;Eltringham & Hockley, 1961;Holdich, 1968;Venkatakrishnan & Balakrishnan, 1973). Gravid females were rarely collected from November to March, but there was a high level of reproductive activity in April when the majority of gravid females collected had eggs (stage 1 young) in the brood chambers.…”

Breeding and bionomics of the British members of the Jaera albifrons group of species (Isopoda: Asellota)

“…In this method of analysis of breeding, the numbers of gravid females per month are expressed as a percentage of the total adult population (referred to as "gravidity"), following the method adopted by Eltringham & Hockley (1961) for Limnoria. The.data are presented in Fig.…”