Ontogenetic diel vertical migration of the planktonic copepodCalanus sinicus in the Inland Sea of Japan

Abstract

The ontogenetic die1 vertical migration of the planktonic copepod Calanus sinicus was investigated in the Inland Sea of Japan in summer 1988, when the water was thermally stratified with a thermocline of ca 5 °C between 35 and 45 m. Stage-specific differences in the diel vertical migration behavior of C. sinicus were found. Eggs were spawned primarily within the surface-waters between midnight and dawn by ascending females, and sank gradually to deeper waters until they hatched into nauplii. Non-feeding nauplius stages (NI and II) were distributed throughout the water column, but the first feeding stage (NIII) performed an ontogenetic upward migration. NIV to VI and copepodite (C) stages I to III continuously aggregated in the phytoplankton-rich euphoric layer. However, the depth of the median CI to III populations descended as stage progressed. The onset of prominent diel vertical migration took place in CIV, and the amplitude of vertical migration increased with age, being maximal in adult females (CVI?). Adult males (CVI~), however, remained in the layer below 20 m, and did not migrate dielly. The ecological significance of ontogenetic diel vertical migration is discussed.

Ontogenetic diel vertical migration behaviors of the marine planktonic copepods Calanus pacificus and Metridia lucens

“…1955). Such patterns were seen in a population of C. pacificus in the Southern California Bight (Mullin 1986) and in Calanus sinicus, a species closely allied to C. pacificus, in the Inland Sea of Japan (Uye et al 1990, Huang et al 1992). However, Williams & Conway (1984) observed a large portion of all the Calanus helgolandicus copepodid stages in the Celtic Sea migrating over 60 m in May but only the older copepodids migrating during the summer.…”

Cannibalism by female Calanus finmarchicus on naupliar stages

“…While young Calanus spp. nauplii do not perform DVM (Nicholls 1933, Huntley & Brooks 1982, Uye et al 1990), females show a high flexibility in DVM amplitude (Irigoien et al 2004) in relation to food (Huntley & Brooks 1982) and predators (Bollens & Frost 1989). During periods of food scarcity, however, DVM is considered to be a non-rewarding strategy even at high predation risk (Manteifel 1959, Fiksen & Giske 1995.…”

Has zooplankton 24 hour vertical distribution pattern in Lough Derg (Ireland) been changed over the period of ∼90 years?

“…Liu et al 2006 wrote that DVM is only a tip of an iceberg from the perspective of the whole picture of zooplankton behaviors , though it appears to be the most marvelous spectacle during the lifetime of the performers. DVM is notable for its diel rhythm, magnitude of migration and ontogenetic variances (Mclaren 1963;Uye et al 1990;Zaret, Suffern 1976), but all these remarkable features do not mean to decouple the mechanisms underlying DVM from the behavioral strategies directing the ''everyday concerns'' of an individual animal. In other words, one mechanism, if it is reasonable for interpreting the general behaviors, will be recommendable for the understanding of DVM, and vice versa.…”