Distribution, growth rate, and death from octopod and gastropod predation ofTawera bollonsi(Bivalvia: Veneridae) at the Auckland Islands

Abstract

Tawera bollonsi, originally described from five valves whose colour suggested their derivation from a comparatively late fossiliferous deposit, is a common bivalve living at the Auckland Islands. Discoloration occurs during life and not after death. Its shell is more inflated than in any other Tawera species. It lives in mud, sandy mud, and fine sand in the inlets and harbours, often with the crustaceans Callianassa filholi and Heterosquilla tricarinata and the bivalve Chione aucklandica. The size frequency of both living specimens and valves is bimodal. For the living specimens the main peak is at 6-8 mm, with a secondary peak at 38-40 mm. The main peak for valves is at 25-37 mm with a secondary peak at 5 mm. Growth rate is very variable and may be genetically determined. Predation rates for both octopus and gastropod predation varied considerably but, with one exception, were less than 20%. Octopus predation, not previously been reported from waters as cold as the subantarctic Auckland Islands, is a more common cause of death than gastropod predation.

Population dynamics of the venerid bivalve Tawera gayi (Hupe, 1854) in the Ushuaia Bay, Beagle Channel

“…The shell growth pattern of T. gayi in Ushuaia Bayalternating narrow translucent and broad opaque bands (Fig. 3) -resemble growth patterns observed in other species of the genus Tawera (Luckens, 1990(Luckens, , 1991Isla and Gordillo, 1996) as well as in other venerid bivalves such as Eurhomalea exalbida (Lomovasky et al, 2002a,b), Mercenaria campichiensis (Jones et al, 1990;Arnold et al, 1996Arnold et al, , 1998, M. mercenaria (Jones et al, 1990;Arnold et al, 1991Arnold et al, , 1996Arnold et al, , 1998 and Venus verrucosa (Arneri et al, 1998). The presence of growth rings indicates periods of very slow or even halted shell growth (Rhoads and Lutz, 1980) possibly caused by either (i) low metabolic rates related to low environmental temperatures (Grizzle and Lutz, 1988;Jones et al, 1990;Lomovasky et al, 2002a); (ii) a lack of food (Green, 1973;Beukema and Desprez, 1986;Beukema and Cade´e, 1991;Kube et al, 1996;Arneri et al, 1998); or by (iii) a diversion of metabolic products away from shell growth into gamete production (Morton, 1978;Ankar, 1980;Peterson and Fegley, 1986;Ramo´n et al, 1995;Arneri et al, 1998;Lomovasky et al, 2002a).…”

“…The shell growth pattern of T. gayi in Ushuaia Bay – alternating narrow translucent and broad opaque bands (Fig. 3) – resemble growth patterns observed in other species of the genus Tawera (Luckens, 1990, 1991; Isla and Gordillo, 1996) as well as in other venerid bivalves such as Eurhomalea exalbida (Lomovasky et al., 2002a,b), Mercenaria campichiensis (Jones et al., 1990; Arnold et al., 1996, 1998), M. mercenaria (Jones et al., 1990; Arnold et al., 1991, 1996, 1998) and Venus verrucosa (Arneri et al., 1998).…”

“…as well as our field experiment strongly indicate that gastropods such as Xymenopsis muriciformis , Trophon geversianus and Natica sp., are the major predators of T. gayi from Ushuaia Bay, a situation similar to the one observed in T. mawsoni from Macquarie Island, New Zealand (Luckens, 1990). Tawera gayi , as other species of the genus Tawera from Australasian (Luckens, 1990, 1991), are usually found close the sediment surface. Thus, they are easier prey for snails than are the deeper‐dwelling venerids such as E. exalbida (Lomovasky et al., 2002a).…”

Marine reserves demonstrate trophic interactions across habitats

“…Snapper and other benthivorous fauna such as rays (Hines et al 1997) and octopus (Luckens 1991) are also likely to prey on these organisms. However, this study provides strong evidence that predation by rock lobster can be an important factor in the survivorship of adult bivalve populations.…”

Stereotypic boring behaviour inferred from the earliest known octopod feeding traces: Early Eocene, southern England

“…(1998) presented prey to the octopods in empty aquaria rather than allowing these infaunal prey to burrow down in sediment and assume their natural position which is likely to have had implications on prey handling. Although a study by Luckens (1991) on modern octopod drilling in bivalve prey discovered a positive correlation between drill hole and prey size, the study of Plio‐Pleistocene octopod drill holes in scallops by Harper (2002) did not.…”