The Behavior and Life History of a Sand‐Beach Isopod, Tylos Punctatus

Abstract

Tylos punctatus is an abundant oniscoid isopod on sheltered sandy beaches in southern California and in Baja California. It is strictly nocturnal, being buried in the sand or under wrack by day. During the winter it does not emerge onto the surface, remaining buried in the sand high up on the beach, the adults up to a meter deep and the juveniles shallower. From March to late October or November, however, it emerges at night to feed on stranded seaweeds and dead animals. When the high tide is early in the evening, T. punctatus emerges onto the surface only after the tide has begun to ebb from over the sand in which it is buried. Tylos moves seawards at first, but this strict seaward tendency diminishes the further down the beach it has walked. It apparently navigates by beach slope. Later in the night, having fed, Tylos moves back up the beach to bury itself at the previous night's high—water mark. T. punctatus is extremely abundant on El Estero Beach. Its reproductive rate is very low compared with that of other oniscoid isopods. Females breed once a year in summer. They incubate with that of other oniscoid isopods. Females breed once a year in summer. They incubate the embryos in their brood pouches in the sand above the high—tide line for about 9 weeks and produce an average of 13.6 young each. Larger females tend to produce more young. Very few if any females breed before they are 3 years old and most, if not all, die soon after. Some males, however, live for at least 4 years. T. punctatus only grows during a 5—month period in the summer. There is no significant difference between mean sizes or growth rates of males and females. Growth rate declines with age.

Foraging activity of the sand beach isopod Scyphax ornatus Dana

“…Tylos punctatus on the Californian coast feed mainly on stranded kelp but also eat carrion when it is available (Hamner et al 1969); T. capensis, and T. granulatus on the South African coast have a similar diet (Kensley 1974;Marsh & Branch 1979). The Mediterranean species T. latreilli eats marine amphipods and carrion such as dead fish (Vandel 1960).…”

Female sexual receptivity in the sandy-beach isopodTylos granuliferus(Crustacea)

“…Several species of the semi-terrestrial isopod Tylos have been studied to understand their ecology (Hamner et al 1969;Hayes 1974;Kensley 1974;Imafuku 1976;Brown and Odendaal 1994;Brown and Trueman 1996;Odendaal et al 1999;Sato et al 2005Sato et al , 2007Kuramochi 2006). However, the female reproductive cycle of T. granuliferus remains poorly understood.…”

Seasonal Dynamics of Diel Changes in Inshore Benthopelagic Communities of the Black Sea by the Example of the Golubaya Bay (Gelendzhik Town)

“…Many littoral organisms become planktonic during tides; their distribution, migrations, and numerous behavioral and morphological adaptations over both rock and mud/sand substrate attracted the attention of many researchers (Jansson and Kallander, 1968;Hamner, 1969;Fincham, 1970;Grant, 1980;Colombini et al , 1996). Sometimes such littoral organisms with benthic mode of life in the day-time and spread along the whole water column in the night-time are called "facultative plankton" (Robertson and Howard, 1978).…”