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The jumbo or Humboldt squid, Dosidicus gigas, is an important fisheries resource and a significant participant in regional ecologies as both predator and prey. It is the largest species in the oceanic squid family Ommastrephidae and has the largest known potential fecundity of any cephalopod, yet little is understood about its reproductive biology. We report the first discovery of a naturally deposited egg mass of Dosidicus gigas, as well as the first spawning of eggs in captivity. The egg mass was found in warm water (25 -278C) at a depth of 16 m and was far larger than the egg masses of any squid species previously reported. Eggs were embedded in a watery, gelatinous matrix and were individually surrounded by a unique envelope external to the chorion. This envelope was present in both wild and captive-spawned egg masses, but it was not present in artificially fertilized eggs. The wild egg mass appeared to be resistant to microbial infection, unlike the incomplete and damaged egg masses spawned in captivity, suggesting that the intact egg mass protects the eggs within. Chorion expansion was also more extensive in the wild egg mass. Hatchling behaviours included proboscis extension, chromatophore activity, and a range of swimming speeds that may allow them to exercise some control over their distribution in the wild.

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The effects of ten different water temperatures on the growth of newly released ephyrae of Aurelia labiata were explored. Ephyrae grown at 21°C showed the greatest growth, increasing in bell diameter from about 4.0 mm to 14.5 mm in 14 days and remained in good condition for the duration of the experiment. Ephyrae subjected to other temperatures grew at different rates. Ephyrae maintained at 8°C gradually decreased in size during the experiment, shrinking in bell diameter from about 4.0 mm to 3.8 mm by day 14, but remained in apparent good condition. Ephyrae reared at 22.5°C and above everted their bells, were in poor condition, and were unable to feed or swim effectively by about day ten. In this study the optimal temperature range for rearing A. labiata ephyrae was 12°C—21°C, which corresponds with the reported range for this species.

Egg capsules of the squid Doryteuthis (= Loligo) opalescens were reared in the laboratory to assess the dependence of time‐to‐hatching (incubation time) and hatching success rate on temperature and light regime. Both incubation time and hatch duration were found to be inversely related to temperature. More than 96% of paralarvae hatch from eggs reared at temperatures between 9 and 14 °C. Hatch rate drops below 90% in warmer and colder water. No eggs hatch below 7 °C, and the upper limit of viability is near 25 °C. The vast majority (91%) of hatchlings emerged during the dark phase of the photoperiod. Egg capsules reared at 13.4 °C with a supposedly commensal polychaete, Capitella ovincola, had a slightly higher hatch rate than those without the annelid. Because eggs are naturally laid closely together, crowding was hypothesized to cause decreased ventilation and a lower hatch rate. Crowding was tested by placing two capsules (rather than one) into the small incubation chambers (50 ml). This treatment did not result in a lower hatch rate at 13.4 °C, but at 21.4 °C it decreased the hatch rate by 20%. Brood incubation duration is related to temperature by the equation: Incubation (days) = 14.97 + 177.40 × exp(−0.119 × Temperature –°C) (χ2 = 282.5, P = 0.001). Stable isotope analysis confirmed that C. ovincola worms eat the capsule matrix, not the paralarvae. These polychaetes had a δ15N value of 12.79‰versus 12.06‰ for squid paralarvae, and 10.54‰ for the gelatinous matrix of egg capsules. This fractionation factor ε of 2.25‰ is consistent with marine food webs. Provision of nutrients and shelter for the annelids and increased hatch rate for the squid embryos suggests a symbiotic relationship between these organisms.

Phacellophora camtschatica has long been assigned to the semaeostome scyphozoan family Ulmaridae. Early stages (scyphistomae, strobilae, ephyrae, postephyrae, and young medusae) of the species were compared with those of several other semaeostomes currently assigned to Ulmaridae, Pelagiidae, and Cyaneidae. Juveniles of P. camtschatica did not strictly conform with characters of those of any of these families, and appeared intermediate between Cyaneidae and Ulmaridae. A new family, Phacellophoridae, is proposed to accommodate P. camtschatica.

Laboratory incubation experiments were conducted to examine the effects of different temperatures (4, 9, 14, 19, 23°C) and salinities (21, 27, and 34) on survival and asexual reproduction of scyphistomae of Cyanea capillata, Cyanea lamarckii, Chrysaora hysoscella, and Aurelia aurita in order to better understand how climate variability may affect the timing and magnitude of jellyfish blooms. Significant mortality was only observed for C. capillata and Ch. hysoscella at the highest and lowest temperatures respectively, but temperature and salinity significantly affected the asexual reproductive output for all species. As temperature increased production rates of podocysts increased and, if produced, progeny scyphistomae by side budding also increased. However, strobilation rates, and therefore the mean number of ephyrae produced, decreased when scyphistomae were exposed to elevated temperatures. These results provide a mechanistic explanation for why ephyrae of these species tend to be produced during colder periods of the year whilst summer and early autumn are probably important periods for increasing the numbers of scyphistomae in natural populations.

Abstract. Gelatinous zooplankton play important roles in marine ecosystems and at times can have significant impacts on human activities. Many scyphozoans have enigmatic life cycles and the specific habitat for benthic life history stages is unknown. This is especially true for many of the large surface‐cruising scyphomedusae of the northeast Pacific Ocean. Phacellophora camtschatica belongs to the family Ulmaridae and is known to have scyphistomae in the life history. However, the life cycle of P. camtschatica has not been formally described. Here the life cycle of members of P. camtschatica is described based on laboratory observations and compared with early life history stages in the scyphomedusa Aurelia labiata.