Factors regulating the breeding and foraging activity of a tropical opisthobranch

Abstract

This study investigated the influence of environmental factors on the foraging cycle, breeding activity, settlement and growth of the opisthobranch Hydatina physis using laboratory trials and field observations. Results showed that H. physis follows a nocturnal circadian rhythm mediated by photic intensity and modulated by food availability. The adults foraged between 1900 and 0530 h, with an activity peak between 2000 and 2200 h, and remained inactive and burrowed in the sand during the day. This pattern was clearly influenced by cloud cover, rain and laboratory manipulated light:dark cycle. The reproduction of H. physis was primarily influenced by the lunar cycle. For 4 consecutive months, hermaphroditic reciprocal copulation, preceded by pre-copulatory courtship behaviour, occurred at night 5-7 d before the full moon. Spawning occurred 3-5 d later for up to 5 consecutive nights, the egg mass gradually decreasing in size with each spawning. An overcast sky or rain prevented or delayed both copulation and egg release. Settlement of veligers was largely influenced by the nature of the substrate. In multiple-choice experiments, settlement occurred predominantly on sand containing cirratulid polychaetes. The juveniles reached ca. 3.9 mm in shell length after 5.5 months growth.

Diet, reproduction, settlement and growth ofPalio dubia(Nudibranchia: Polyceridae) in the north-west Atlantic

“…The experiment was performed at 6.58C in a thermostatic bath, under natural light and photoperiod for a maximum of 5 d. Data are based on the release of 50 larvae per container (N ¼ 3) and expressed as mean + SD. (Karlsson & Haase, 2002) and Hydatina physis (Hamel & Mercier, 2006). Like in P. dubia, mating in other opisthobranchs occurs in the head-to-tail position, side by side, following the general pattern described for other opisthobranchs, most of which are hermaphrodites that undergo reciprocal internal copulation and sperm storage (Hadfield & Switzer-Dunlap, 1984;Karlsson & Haase, 2002;Hamel & Mercier, 2006).…”

“…Hadfield & Switzer-Dunlap (1984) noted that many opisthobranch larvae display this so-called 'searching behaviour', which refers to alternate periods of swimming and settlement. Such larvae are usually capable of undergoing metamorphosis when a substratum is deemed suitable in some subtle way, and are thus referred to as competent larvae (Hamel & Mercier, 2006).…”

“…The feeding habits, reproductive cycles and larval biology of most species have yet to be fully elucidated, and this relative scarcity of published data may in part be due to the sporadically explosive breeding mode of most opisthobranchs (Beeman, 1977;Hamel & Mercier, 2006).…”

Life in the arena: infaunal gastropods and the late Phanerozoic expansion of marine ecosystems into sand

“…Sand‐burrowing habits in these basal shell‐bearing heterobranchs are documented for species in the Acteonidae, Haminoeidae ( Aliculastrum and Atys ) (Fig. ), Hydatinidae and Philinidae (Fretter & Graham ; Fretter ; Rudman , b; Yonow ; Hamel & Mercier ). I conservatively accept only one transition to the infaunal habit in this assemblage.…”

Record of striped paper bubble shell, Hydatina physis (Linnaeus, 1758), from Indian waters

“…Reports of the genus Hydatina have been made for the species Hydatina zonata (Lightfoot, 1786) from the Indian coast off Chennai, Pamban, Kundukkal point, Mandapam (Burn & Thompson, 1998;Burn, 2006;Ganesh et al, 2009;Bouchet & Gofas, 2014) along the south-east coast, off Koyyam (Burn & Thompson, 1998) along the north-east and from the Gulf of Kutch (Gosliner et al, 2008) along the north-west coast of India. Hydatina velum (later synonymized with Hydatina zonata) has also been observed from the coast of the Gulf of Mannar, south-east coast of India (Habe et al, 1950), and also from the coast of the Lakshadweep islands (Hamel & Mercier, 2006).…”