Studies ontrichogramma buesi as a biocontrol agent againstPieris rapae in Egypt

Trichogramma buesi was reared in the laboratory on eggs of the Mediterranean flour moth,Anagasta kuehniella. The incubation period of the parasite's egg was 27 h at 23 °C and 22 h at 27 °C. The larval stage lasted 3.6 and 3.2 days, the pre-pupa lasted 16 and 23 h, and the pupa lasted 5.4 and 4.6 days at 23° and 27°C, respectively. The total developmental time (from egg to adult) averaged 9.2, 9.4, and 9.1 days when the parasite was reared on eggs ofPieris rapae, Spodoptera littoralis, andA. kuehniella, respectively, at 27 °C. Sex ratio inT. buesi was 1 ♂: 1 ♀ in nature and 1 ♂: 1.3 ♀ in the laboratory. The daily and total numbers or progeny produced/female were 5.1 and 98.2 adults, respectively. The parasite female, fed on honey, lived 10.7 days at 27 °C and 12.1 days at 23 °C. Percentages of parasitism byT. buesi on eggs ofP. rapae collected from cabbage fields ranged between 0 and 31.5 % in 1985 and betwcen 0 and 36.4% in 1986 during July through December. The respective figures on eggs collected from turnip fields were 16–42.2% and 12.5–32.1% during November and December.      

Reproduction and larval development of the gastropodAlaba vladivostokensis in Vostok Bay, the Sea of Japan

The reproduction and development of the prosobranch gastropodAlaba vladivostokensis Bartsch were studied. In Vostok Bay,A. vladivostokensis reproduces in the warmest season at water temperatures of 19–23°C. The females lay egg masses in the shape of flat, coiled bands on eelgrass leaves and on sargosso thalluses. The total period of development from egg laying to larval settling takes 25–27 days. The reproduction and development patterns and larval morphology ofA. vladivostokensis are similar to that ofAustralaba picta (A. Adams), which inhabits the coast of Japan. It is suggested that the population ofA. vladivostokensis in Peter the Great Bay should considered as part of the wide geographical range ofA. picta.     

A case for a free-running circannual rhythm in soldier developmental time of Formosan subterranean termites

The success of all insect societies relies on their ability to maintain optimal levels of different castes. Here we report on an apparent free-running circannual rhythm that optimizes the developmental time of the soldier caste of Coptotermes formosanus Shiraki. Over a 3 year period, bioassays were conducted each month (except June) with groups of 100 termite workers in a 28°C incubator in total darkness. The number of days needed for C. formosanus soldiers to develop varied depending on the time of the year (month). In March, just prior to the major swarming exodus for alates (April to June), 9 days were required before a worker molted to a presoldier. Longer times were required for such a molt in all other months, with an increasing trend from April to December (from 13 to 30 days) and a decreasing trend from January to February (from 25 to 12 days). Colony origin or the length of time that termites were kept in the laboratory under constant conditions (26 – 28°C, 70 – 80% RH) before testing (7 days – 1 year) did not affect this rhythm. This is the first demonstrated evidence of a free-running circannual rhythm in a social insect. Received 23 July 2007; revised 9 and 21 August 2007; accepted 23 August 2007.     

Survivorship,growth and reproduction of the non-native <Emphasis Type="Italic">Caprella mutica</Emphasis> Schurin, 1935 (Crustacea: Amphipoda)

Caprella mutica Schurin is an epifaunal amphipod crustacean which originates in north-east Asia and has spread throughout the world, yet very little is known about fundamental aspects of this species biology. This paper examined the survivorship of C. mutica reared under laboratory conditions at 13–14 °C, 14 h light: 10 h dark photoperiod and fed commercial salmon feed, the diatom Cylindrotheca fusiformis Reumann and Lewin, the macroalgae, Fucus vesiculosus L. and given no additional feed. In addition, growth, maturation and reproduction of C. mutica fed C. fusiformis were assessed. No significant difference in survivorship of C. mutica was observed for the diet types over the experimental period. C. mutica was able to survive for upto 20 days without additional food. Average survival time of males and females fed the diatom, C. fusiformis was 68.8 d (range = 62–73 d) and 82.0 d (range = 76–92 d). Juvenile C. mutica emerged from the brood pouch at a body length of 1.33 mm and moulted at 5.0–11.0 day intervals. Males exhibited faster growth rates than females after Instar VII. Females produced their first brood at Instar VII, 24–26 days post-hatching and with an average body length of 8.5 mm. Each female had an average of two broods sequentially and these were released at 20.2 day intervals. Brood size for a single female increased from 11.3 (±9.9) hatchlings at Instar VII to 25.5 (±11.5) at Instar IX and the maximum number of hatchlings produced by a single female was 82. The results suggest that C. mutica exhibits a number of life-history traits that would potentially enable it to withstand global transportation and to rapidly become established in an introduced region, if environmental conditions are suitable.     

Development of the salivary glands in embryos of Ixodes ricinus (Acari: Ixodidae)

We examined Ixodes ricinus embryos between 18 and 28 days of development with light, scanning and transmission electron microscopy. The differences in inner structure attested to establish three successive developmental stages: days 18–20, day 23, and days 26–28. Between 18 and 20 days the embryos are at early stages of organogenesis. Salivary glands cannot be identified at that stage. In 23-day-old embryos salivary glands are already outlined but the structure of alveoles is still different from that in larvae in which the embryonic development has been completed. Gland cells start to form alveoles and become active between 26 and 28 days of the development. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of temperature and photoperiod on the development and oviposition ofApanteles sp. groupUltor [Hym.: Braconidae], a larval parasite of the carob mothEctomyelois ceratoniae [Lep.: Pyralidae]

Development of the solitary parasitoidApanteles sp. groupultor in larvae ofEctomyelois ceratoniae was investigated at different constant temperatures. Temperature had a significant effect upon parasitoid development during both host-internal and host-external phases. The duration of the host-internal phase varied from 41 days at 15–17°C to 8.6 days at 29°C, the duration of the host-external phase varied from 16.5 days at 16–17°C to 5.4 days at 29°C. Effect of photoperiod upon parasite development and parasitization of hosts were determined under daily photophases, of 24, 16, 12, 8 and 0 hours. No significant differences in oviposition rate were found among the 5 treatments. In any photoperiod studied, the parasite progeny developed normally without entering diapause.      

Optimization of <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation conditions in mature embryos of elite wheat

Immature embryos have been used frequently as target tissues in the genetical transformation of wheat. However, obtaining a large number of high quality immature embryos throughout the year is a laborious and delicate process, because of the need to cultivate the plants under controlled conditions. To circumvent this, we have employed mature embryos rather than immature ones as starter explants for Agrobacterium-mediated transformation of an elite wheat (Triticum aestivum L.) cultivar EM12. The neomycin phosphotransferase ІІ (npt ІІ) and β-glucuronidase (gus) genes were used as selectable and screenable marker genes, respectively, to assess and optimize the performance of T-DNA delivery. With the aid of an orthogonal design, the effect of four factors in combination on transfer DNA (T-DNA) delivery was studied. These factors were preculture duration, different kinds of inoculation, length of inoculation and co-culture condition. Optimal conditions for T-DNA delivery were obtained for mature embryos precultured for 14 days, followed by immersing in inoculation suspension with full strength Murashige and Skoog (MS) salts in darkness at 23–25°C for 3 h, and then co-culturing with Agrobacterium under desiccating condition in the dark at 23–24°C for 2–3 days. Complete analysis of transgene insertion demonstrated that the optimized method for Agrobacterium-mediated transformation of mature embryos of wheat was efficient and practicable.     

Studies on the oviposition and longevity ofIlione albiseta [Dipt.: Sciomyzidae] — Potential biological control agent of liver fluke

The effect of 5 constant temperatures (10, 14, 17, 20 and 23°C) on the oviposition and longevity ofIlione albiseta was investigated. Most eggs were laid at 14–17°C and mean oviposition period declined progressively above and below 14°C. There was no significant difference between oviposition rates or preoviposition periods at each constant temperature, but the mean number of days between egg laying for each female was significantly greater at 10 °C than at 17, 20 and 23 °C than at 20 °C. The percentage of infertile eggs laid ranged from 9.2% at 23 °C to 17.9 % at 20 °C and these eggs tended to be laid at the beginning and end of each oviposition period. A possible association between sex ratio of the emergent adult and temperature is also discussed.      

Bionomics ofTetrastichus sesamiae [Hymenoptera: Eulophidae], a pupal endo-parasitoid ofMaruca testulalis [Lepidoptera: Pyralidae]

The biology and behaviour ofTetrastichus sesamiae Risbec, a pupal endoparasitoid ofMaruca testulalis Geyer, were studied under laboratory conditions. Most adults emerged from the host pupae between 08.00 h and 09.00 h and mating and oviposition started almost immediately. Both ♂♂ and ♀♀ mated repeatedly, and each ♀ could lay eggs for up to 6 days and in up to 5 host pupae. Progeny production ranged from 0–263 offspring per ♀ and adult longevity was from 4.3–13.9 days. The quality of food available to the adults was a major factor influencing progeny production, and longevity. The species was capable of parasitizing and completing development on pupae of such other major Lepidopteran crop pests asChilo partellus Swinhoe,Busseola fusca Fuller,Eldana saccharina Wlk andSpodoptera exempta Wlk, an important finding for biological control of these pests under intercropped agro ecosystems. Apart from parasitism, ♀♀ ofT. sesamiae also caused considerable mortality by stinging, and presumably paralyzing, host pupae without ovipositing.      

Embryonic, larval and juvenile development of the roughskin sculpin,Trachidermus fasciatus (Scorpaeniformes: Cottidae)

Embryonic, larval and juvenile development of the catadromous roughskin sculpin,Trachidermus fasciatus, were described using eggs spawned in an aquarium. The eggs, measuring 1.98–2.21 mm in diameter, were light reddish-yellow and had many oil globules, 0.05–0.18 mm in diameter. Hatching occurred 30 days after spawning at 2.3–11.3°C. The newly-hatched larvae, measuring 6.9–7.3 mm BL, had a single oil globule, 9–10+25–26=34–36 myomeres and 6 or 7 large stellate melanophores dorsally along the gut. The yolk was almost resorbed, number of pectoral-fin rays attained 16–17, and two parietal, one nuchal and four preopercular spines were formed, 5 days after hatching, at 8.2–8.4 mm BL. The oil globule disappeared, and one supracleithral spine was formed, 11 days after hatching, at 8.9–9.5 mm BL. Notochord flexion began 15 days after hatching, at 9.7–10.3 mm BL. A posttemporal spine was formed 20 days after hatching, at 10.7–10.9 mm BL. The first dorsal fin spines (VII–VIII), second dorsal fin and anal fin rays (18–19, 16–18, respectively) appeared 23 days after hatching, at 12.0–13.7 mm BL. The pelvic fin spine and rays (I, 4) were formed and black bands on the head and sides of the body began to develop 27 days after hatching, at 13.8–15.8 mm BL. Newly-hatched larvae swam just below the surface in the aquaria. Preflexion larvae (8.9–9.5 mm BL), in which the oil globule had disappeared, swam in the middle layer, while juveniles (13.8–15.8 mm BL) began swimming on the bottom of the aquaria. Swimming behavior observed in the aquaria suggested that the fish started to change to a demersal existence at the juvenile stage.     

Development of eggs, larvae and juveniles of laboratory-reared blue whiting,Sillago parvisquamis (Percoidei: Sillaginidae)

The embryonic, larval and juvenile development of blue whiting,Sillago parvisquamis Gill, are described from a series of laboratory-reared specimens. Mean egg diameter and mean total length (TL) of newly-hatched larvae were 0.71 mm and 1.58 mm, respectively. The eggs were non-adhesive, buoyant and spherical with an oil globule (mean diameter 0.18 mm). Hatching occurred about 20 hours after fertilization at a temperature of 24.0–25.0°C, newly-hatched larvae having 38–40 myomeres. The yolk and oil globule were completely absorbed 3 days after hatching at 2.8–3.2 (mean 3.0) mm TL. Notochord flexion was completed by 7.2–8.2 (7.7) mm TL, and pectoral and caudal fin rays fully developed by approximately 10 mm and 8.5 mm TL, respectively. Completion of fin development occurred in the following sequence: caudal, pectoral, anal and second dorsal, first dorsal and pelvic, the last-mentioned by approximately 11 mm TL. The larvae ofS. parvisquamis andS. japonica, which closely resemble each other in general morphology and pigmentation, could be distinguished as follows. Newly-hatchedS. parvisquamis larvae had more myomeres thanS. japonica (38–40 vs. 32–34) and more melanophores on the dorsal surface of the body (19–28 vs. about 40).Sillago japonica had a vertical band of melanophores on the caudal peduncle, which was lacking in postflexionS. parvisquamis larvae. In addition, juveniles ofS. parvisquamis (larger than 23 mm TL) had melanophores on the body extending anteriorly to below the lateral line to form a midlateral band, whereas no obvious band occurred on similarly-sizedS. japonica juveniles.     

Plantlet regeneration of <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> var. adik-adik by tissue culture

Three color morphotypes of Kappaphycus alvarezii var. adik-adik (brown, green and red) collected from a farming area in Tictauan Is., Zamboanga City, Philippines were used as explants in the study in order to micropropagate ‘new’ plants. Individual sections of sterile Kappaphycus alvarezii var. adik-adik, initially cultured in a 48-well culture plate containing ESS/2 + E3 + PGR, released callus cells after 4–5 days of incubation at 23–25°C, 13:11H LD cycle and 10–15 μmol photons m⁻² s⁻¹ light intensity. True calli were formed after 29–35 days following dense formation of filaments or undifferentiated round cells at the medullary and inner cortical layers of the section. Plantlets (2–3 mm long) of Kappaphycus alvarezii var. adik-adik were able to regenerate after 98, 150 and 177 days in-vitro among the reds, greens, and browns, respectively. This study established successful methods for the production and regeneration of tissue explants of Kappaphycus alvarezii var. adik-adik which can possibly be used to mass produce ‘new’ cultivars for land- and sea-based nurseries as sources for commercial farming. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Rearing of two predators,Thanasimus dubius andTemnochila virescens, for the biological control ofIps grandicollis in Australia

Rearing methods for two coleopterous predators,Thanasimus dubius andTemnochila virescens, imported into Australia for the biological control ofIps grandicollis, were developed. Bionomic data obtained from laboratory rearings between 1982–1987 showed thatT. dubius eggs took about 7 days to hatch and that duration of the larval stage was about 42 days. Observations showed thatT. dubius had a prolonged prepupal stage (x=56.4 days, range 14–274 days), which was probably non-diapausal in nature. Mean adult longevity was 50 days (range 1–358 days).Temnochila virescens eggs took almost 9 days to hatch, and a lengthy larval stage (x=155.4 days, range 73–333 days) was observed. Mean duration of the pupal stage was 14 days (range 7–28 days). A long preoviposition period (x=141 days, range 47–206 days) was observed, and adults were very long-lived (x=232.7 days, range 14–667 days). Capacity for increase (r_c) calculated from rearing data suggested that numbers ofT. dubius could be increased faster thanT. virescens. Mortality between 1982–1987 averaged about 70% for both species. However, mortality ofT. dubius in 1987 increased significantly, suggesting that inbreeding or other methodological factors could be responsible. A mass-rearing method usingIps-infested pine billets was developed as a cheaper alternative to laboratory rearing, and was shown to be effective in producing large numbers of insects for release.     

Climate change affects timing and size of populations of an invasive cyanobacterium in temperate regions

Cylindrospermopsis raciborskii, an invasive freshwater cyanobacterium, originated from the tropics but has spread to temperate zones over the last few decades. Its northernmost populations in Europe occur in North German lakes. How such dramatic changes in its biogeography are possible and how its population dynamics in the newly invaded habitats are regulated are still unexplained. We therefore conducted a long-term (1993–2005) study of two German lakes to elucidate the mechanisms behind C. raciborskii population dynamics and to identify the abiotic constraints on its development. Our data revealed that pelagic populations of C. raciborskii thrived for three months during the summer, contributing up to 23% of the total cyanobacteria biovolume. Population sizes varied greatly between years without exhibiting any distinct long-term trends. In the annual lifecycle, C. raciborskii filaments emerged in the pelagic habitat when the temperature rose above 15–17 °C. At that time, mean photosynthetically active radiation in the mixed water column (I _mix) overstepped its maximum. Rates of population net increase were highest at the beginning of the season (0.15–0.28 day⁻¹), declined continuously over time, and were significantly positively correlated with I _mix. This indicates that the onset of the pelagic population is temperature-mediated and that I _mix controls its growth. Since I _mix peaks before the population onset, the time of germination is of crucial importance for successful development. To test this hypothesis, we designed a model to simulate pelagic population size, starting at different dates in the annual cycle. Moving the population onset forward by 30 days resulted in a doubling of the population size. We therefore conclude that an earlier rise in water temperature associated with climate change has promoted the spread of C. raciborskii to the temperate zone. Earlier warming permits earlier germination, thereby shifting the pelagic populations to a phase with higher I _mix, which advances growth and the population establishment.     

Reproductive behaviour of wild-living wolves in Białowieża Primeval Forest (Poland)

Characteristics of the reproductive behaviour of wolves (Canis lupus) were studied by radio-tracking and snow-tracking of four packs in Białowieża Primeval Forest (BPF), Poland, in 1995–1999. Signs of mating occurred between 12 January and 22 March. Parturition occurred between 19 April and 12 May, and the denning period lasted for 49–64 days. During that time, wolves used 1–3 den sites, spending on average 27 days at each site. The dens were never reused in consecutive years, but year after year the breeding sites were located in the same parts of the pack’s territory. Ten days before parturition pregnant females reduced their normal mobility by half (from 23 to 13.5 km day⁻¹, on average). During the ten days post-partum, they spent 85% of their time with pups and travelled 3.9 km day⁻¹, only. On days 11–30 after parturition, females spent 74% of their time tending pups and increased their daily movement distance to a mean of 13.3 km. The females resumed full mobility 50–70 days after parturition, which coincides with termination of the weaning process. Anecdotal observations indicated that pups were tended by other pack members while the mother was absent. Compared with the years 1947–1950, in 1995–1999 the breeding season of wolves in BPF occurred two weeks earlier. A possible reason was the 1 to 1.5-degree increase in the mean annual temperature during the last 50 years.     

Chilling and heat requirements for the prediction of the beginning of the pollen season of Alnus glutinosa (L.) Gaertner in Ponferrada (León, Spain)

Winter-flowering trees such as the alder (Alnus glutinosa (L.) Gaertner) can survive periods of adverse climatic conditions, entering a period of dormancy in the early fall. The end of dormancy and the start of the pollen season require a period of low temperatures followed by another of warm temperatures. These requirements were studied from 1995 to 2002, in order to develop a model to predict the onset of the alder pollen season in Ponferrada (Spain). Chilling accumulation took place from late October to late December or early January. The best result was obtained with a threshold temperature of 6.5 °C and an average of 848 chilling hours (CH). Heat requirements were calculated at maximum temperature, an average 143 growth degree days (GDD) were needed, with a threshold temperature of 0 °C. In order to validate models, predicted values were compared with real values for 2002–2003, 2003–2004 and 2004–2005, years not used in developing the models. Predictions for the pollen-season start-date differed only slightly from observed dates: in 2002–2003 predicted and observed dates were the same, in 2003–2004 there was a difference of 7 days and in 2004–2005 a difference of 3 days.     

Ontogenesis of the cricket Gryllus argentinus Sauss. (Orthoptera, Gryllidae)

The development of Gryllus argentinus Sauss. was studied under stable laboratory conditions: the temperature of 26°C, the air humidity of 60%, and the photoperiod of 12h light: 12 h dark. The life cycle of Gryllus argentinus includes four stages: egg, pronymph, nymph, and adult. The duration of embryonic development is 18 days. The depth of egg bedding in the peat is 9.63 ± 0.12 mm (n =145), the clutch containing 2–4 eggs. A female can lay over 1100 viable eggs during the entire oviposition period. Nymphal development includes 9 instars and lasts 97 days. The duration of nymphal instars (days) is: I—5; II—6; III—6; IV—6; V—8; VI—10; VII—13; VIII—14; IX—29. The duration of the adult life is 51 days in males and 69 days, in females. In the imaginal ontogenesis of males and females, three periods can be distinguished: pre-reproductive, reproductive, and postreproductive. Males start to emit the aggressive signal on the 6th (5–8th) day (the pre-reproductive period). They enter the reproductive period (start to emit the calling song) on the 9th (8–13th) day. Females enter the reproductive period (become capable of responding to the calling song and of copulation) on the 9th (8–10th) day. Oviposition starts on the day after the first copulation. The reproductive period lasts about 40 (15–59) days in males and 58 (21–70) days in females. The post-reproductive period starts in females at the moment of finishing the egg laying period and in males, with disappearance of reproductive behavior. The period ends in the animal’s death.     

Ambrosia pollen in the air of Lublin, Poland

Studies on Ambrosia pollen concentrations were carried out in Lublin in the period 1995–2004. The effects of a number of meteorological factors were analysed. In the first period of the study, the gravimetric method was used (1995–1999), while in the second period, the volumetric method was applied. The results show an increasing trend in the amount of airborne pollen. The Ambrosia pollen season in Lublin lasts from August to October. Over a period of 5 years, the highest number of pollen grains was recorded in September (53%), followed by August (44%) and October (3%). There were wide variations in annual totals. The annual total pollen counts was 167–1180 grains, with the peak value in 2002. Maximum daily pollen concentrations (56–312 pollen grains m⁻³) were recorded in the first half of August and in the first half of September. On the days when high Ambrosia pollen concentrations occurred, the temperature was above 21°C and the winds were mainly from the southeast, south and east. Maximum intradiurnal concentrations of pollen grains occurred in the afternoon hours. These results indicate, to some degree, that Ambrosia pollen is transported for long distances before descent.     

Suitability of stages of femaleEncarsia pergandiella [Hymenoptera: Aphelinidae] for development of conspecific male hyperprasites

Encarsia pergandiella Howard females develop as primary parasitoids of immature whiteflies, whereas ♀♀ develop as secondary parasitoids on ♂♂ of their own species or on other primary whitefly parasitoids. In this experiment, maleE. pergandiella development was examined in the laboratory at 24°C, using different stages of immatureE. pergandiella females [enclosed within the cuticle ofTrialeurodes vaporariorum (Westwood)] as hosts. Unmated adult femaleE. pergandiella were caged individually for 24 h on leaves of plants with either 5-day (early to late 3^rd instar larval), 7-day (late 3^rd instar to prepupal), or 9-day (pupal) hosts. In a control treatment, hosts were allowed to complete development without exposure to unmated adult females. Subsequent emergence of ♂♂ (hosts) and ♀♀ from all treatments was recorded daily. Pupal (9-day)E. pergandiella females were found to be the most suitable hosts for development of ♀♀. Nine- and 7-day hosts were attacked at a similar rate, as indicated by a similarly low proportion of host emergence, but ♀♀ emerged at a significantly higher rate in the 9-day treatment than in the 7-day treatment. Development time of ♀♀ was 15±1 days in the 9-day treatment, and 16±1 days in the 7-day treatment (p<0.005). The proportion of hosts emerging from the 5-day treatment was not significantly different from the control treatment. The data suggest that the colonizing ability ofE. pergandiella in greenhouses is likely to be limited by the delay of 7–9 days between oviposition of female eggs and the suitability of these ♂♂ for oviposition of male eggs. Since development time of the 2 sexes is similar this delay should cause a lack of synchrony in the emergence and mating of F₁ ♂♂ and ♀♀.      

Mortality of Herring Eggs on Different Algal Substrates (Furcellaria spp. and Cladophora spp.) in the Baltic Sea – An Experimental Study

In the Baltic Sea, herring (Clupea harengus membras) spawns in the littoral zone, where its eggs are attached to algae or vascular plants. Field studies indicate that egg mortality can be very high (up to 100%) in eggs that are attached to red algae (Rajasilta et al., 1989, 1993). Because high mortality can be due to allelochemical effects of the algae, we studied the mortality of herring eggs on different algal substrates experimentally. Four types of substrates were tested: fresh Cladophora and Furcellaria, and Furcellaria that had decomposed six days or 23 days. The incubation time in the experiments was 3 days and incubation temperature 12–13 ^oC (ca. 700–800 h-degrees). The results were in accordance with observations made in field studies and indicated significant differences among the substrate types. In eggs attached to fresh Cladophora, mortality was significantly lower (mean=2.8%; n=20) than in those attached to Furcellaria, independently of the treatment of the algae. The highest values of mortality (mean=14.4%; n=20) were found in eggs attached to Furcellaria that had decomposed over a six days’ period. This suggested that Furcellaria contain some chemical substances, which can cause mortality in herring embryos and the effect seems to be dependent on the state of decomposition of the algae.