Reproduction and development in the pycnogonid Pycnogonum littorale

Aspects of the reproductive biology of Pycnogonum littorale (Ström) are examined. Vitellogenesis occurs between November and August, the process resembling that in Nymphon gracile, annelids, and Limulus polyphemus, in which the majority of the yolk is synthesized within the oöcyte, with only a small contribution from outside, thus contrasting with the method in insects. The mode of formation of the mature yolk platelets shows similarities with the process described in Cambarus spp. Growth occurs in the post larva by a series of moults, and sometimes in the adult by a process not involving moults. The male usually has 9 moults and the female 10 or 11.     

Oocyte development in the kuruma prawn Penaeus japonicus

Female kuruma prawns (Penaeus japonicus Bate) with undeveloped, early developing, developing, nearly ripe and ripe ovaries, were collected from Ise Bay, Japan, in 1984. Oocyte development of the kuruma prawn was classified into ten stages according to morphological characters, namely: (1) synapsis stage, (2) chromatin nucleolus stage, (3) early perinucleolus stage, (4) late perinucleolus stage, (5) oil globule Stage I, (6) oil globule Stage II, (7) yolkless stage, (8) yolk granule stage, (9) prematuration stage, and (10) maturation stage. The synapsis stage is a multiplication stage. The chromatin nucleolus stage, early and late perinucleolus stages are previtellogenesis and primary growth stages. Oil globule Stage I is an initial stage of primary vitellogenesis and secondary growth. Follicle cells on the oil globule Stage I oocytes expand rapidly and reach maximum size during oogenesis. Yolk granule stage oocytes are in the initial stages of secondary vitellogenesis. Strongly acidophilic yolk granules accumulate within basophilic vesicles of the cytoplasm. The yolk granules are first concentrated in the inner part of the cytoplasm, then gradually spread to the periphery. Cortical crypts, which are separated from the oocyte cytoplasm by the cytoplasmic membrane, are situated outside of oocyte cytoplasm. Germinal vesicle breakdown (GVBD) is initiated in the late phase of prematuration and continues until the late phase of maturation immediately prior to spawning. At the beginning of the maturation stage, the oocytes are ovulated, after which the nuclei further shrink and migrate out-wards. After ovulation, meiotic division of the ovarian oocyte progressed up to the metaphase of primary maturation division. Finally, the meiotic metaphase is visible just beneath the cytoplasmic membrane in the mature oocyte. Though ovulation is synchronous within the same ovary, GVBD is not completely synchronous. Ovulated mature oocytes have many club-shaped cortical crypts in the peripheral part of the cytoplasm and contain extensive accumulations of yolk granules dispersed throughout the cytoplasm. The apical end of the club-shaped cortical crypts and cytoplasmic membrane are coated by the vitellin envelope in the mature oocyte.     

Ovarian maturation of the multi-spawning spider crab <Emphasis Type="Italic">Maja brachydactyla</Emphasis> (Decapoda: Majidae) with special reference to yolk formation

In the study of the reproductive biology of the spider crab Maja brachydactyla, the morphology of the female reproductive system and yolk formation have long been overlooked. Females spawn two or three times during their annual reproductive cycle in northern Spain (Galicia). The ovaries consist of two lobes. The right and left lobes are connected by a small cross-lobe at the level of the heart and merge at the posterior edge. Before merging, the ovaries descend to the ventral part of the body, joining the spermathecae in the vagina, which opens through a chitin tube to the gonopore, located in the sternite, at the level of the third walking leg. No morphological changes have been observed between either the different parts of the ovaries or the different annual spawning periods. At the start of vitellogenesis, the oocyte of M. brachydactyla is characterized by a large number of vesicles in the cytoplasm. These vesicles are surrounded by a unit membrane whose size increases as the oocyte matures and contain fine granular material including a variable number of ovoid, electron-dense granules. The vesicles are of diverse origin, although most of them develop directly from the mitochondria and the Golgi complex (endogenous phase of vitellogenesis). In a subsequent phase, a series of substances (principally lipoproteins) are incorporated into the ooplasma by means of micropinocytosis. These substances are also involved in yolk formation (exogenous phase of vitellogenesis). During vitellogenesis in M. brachydactyla, mitochondria play the most important role since they are not only the energetic centre of the cellule, but they also act as containers of high-energy reserve substances: the yolk granules.     

Quantitative and ultrastructural studies on the reproductive biology of the polychaete Pholoe minuta in Galway Bay

Previous works by the present authors have identified, in a qualitative fashion, the reproductive cycle of Pholoe minuta (Fabricius) in inner Galway (53°13.5N; 9°7W). This quantitative, histological study, carried out over the period late May 1981 to late April 1982, shows that P. minuta is polytelic (two to three annual spawnings in an individual's lifespan). Individuals become sexually mature for the first time when approaching 3 yr of age. Estimates were made of the size of the reproductively active population (47 to 49%), sex ratio (1:1), duration (10 to 11 mo) and pattern (unimodal) of gametogenesis and fecundity levels (210 198 eggs m^-2). Maturation (mean oocyte size=85 m) and spawning (for 1 wk during late March through early April) were shown to be synchronised. Throughout oogenesis, follicle cells play an important role in binding together oocyte clusters, and desmosomal contacts are evident between oocyte and follicle cell plasmalemmas. No evidence for the synthesis of yolk precursors in the follicle cell cytoplasm was discovered. Oocytes are rich in Golgi apparatuses (yolk synthesising) and nuclear pores are numerous. Rough endoplasmic reticulum is distended in nature. Egg envelope development does not appear to commence until after the onset of vitellogenesis. Mature spermatozoa are of the primitive bullet-shaped type, with an unmodified acrosome. A possible method of elevation membrane formation is described.     

Ovarian morphology and oogenesis in Aurelia aurita (Scyphozoa: Semaeostomae): ultrastructural evidence of heterosynthetic yolk formation in a primitive metazoan

In Aurelia aurita, the ovaries arise as horseshoe-shaped evaginations of the gastrodermis in the floor of four interradial gastric pouches. Germ-cell islands arise within endodermally-derived gastrodermal cells. Oocytes grow and gradually bulge into the mesoglea while maintaining physical contact throughout vitellogenesis with specialized cells called trophocytes. Ultrastructural changes suggest that these cells transport yolk precursors from the coelenteron to the oocytes in a manner similar to that reported for the trophonema cells of anthozoan ovaries. Vitellogenesis involves both the autosynthetic activity of the oocyte organelles (Golgi complex and rough endoplasmic reticulum) and the heterosynthetic incorporation of precursors through endocytotic processes involving both coated pits and vesicles and smooth-surfaced tubules. Ultrastructural data suggest that different types or classes of yolk precursors enter the oocyte through the trophocytes and via the surrounding mesoglea. To our knowledge, this is the most primitive animal in which this type of yolk synthesis has been described. The trophocyte-oocyte relationship in oocytes of A. aurita is reminiscent of the trophonema-oocyte relationship in anthozoans and supports the belief that the Anthozoa and Scyphozoa share a close phylogenetic relationship.     

Microgeographical shell variation in Littorina striata, a planktonic developing periwinkle

Littorina striata is a strictly Macaronesian, intertidal periwinkle with planktonic development. The species produces both nodulose and smooth shells, which co-occur at Ilheu de Vila Franca do Campo, a drowned crater situated about 1000?m off the south coast of São Miguel, Azores. The present work describes and analyzes the shell variation, temporal change and ecological distribution of the two shell types at this crater over a 3-year period. Nodulose shells were more common in the sheltered lagoon inside the crater, while smooth specimens dominated the outside of the wave-exposed crater. Moreover, nodulose specimens were smaller and weighed less compared to smooth ones. However, regardless of morphotype, shells from the lagoon had a smaller aperture and were less globose than those from the outside. Within an exposure regime, smooth specimens had a larger aperture. These patterns remained constant over time. They are tentatively interpreted as functional adaptations to thermal stress and wave exposure. The mechanisms that maintain these patterns are still unknown. Yet, aperture height of specimens transplanted from the lagoon to the outside increased markedly over a period of 5 months, whereas no comparable changes were observed in other experimental groups (i.e. transplanted from the outside into the lagoon, transplanted within the outside and transplanted within the lagoon; the latter two transplant groups being the blancos). This suggests that at least the aperture size in L. striata may be an ecophenotypically plastic trait.     

Ultrastructure of the ovary and oogenesis in the jellyfish Linuche unguiculata and Stomolophus meleagris,with a review of ovarian structure in the Scyphozoa

Ovarian structure and oogenesis has been examined in six scyphozoan species including the semaeostome Diplumularis antarctica Maas, 1908 (collected in 1987 in McMurdo Sound, Antarctic), the rhizostomes Cassiopea xamachana Bigelow, 1892 (collected in Belize in 1988), and Stomolophus meleagris L. Agassiz, 1862 (collected in Ft. Pierce Inlet in 1988), and the coronates Periphylla periphylla (Peron and Lesueur, 1810), Nausithoe atlantica Broch, 1914 (both collected in the Bahamas in 1988), and Linuche unguiculata (Schwartz, 1788) (collected in Nassau Harbor, Bahama Islands in 1989). Based on these findings and information on five other scyphozoan species from additional literature sources, at least two fundamentally different types of ovaries exist in the Scyphozoa. In semaeosotome and rhizostome species, oocytes develop in close association with specialized gastrodermal cells called trophocytes which may serve a nutritive function. However, coronate species lack trophocytes and oocytes develop freely in the mesoglea. The ovaries of S. meleagris and L. unguiculata are used as models to represent the ultrastructural events occurring during oogenesis in species having trophocytes and those lacking them, respectively. In both L. unguiculata and S. meleagris, the ovaries arise as evaginations of the gastrodermis in the floor of interradial pouches. Germ cells appear to originate from endodermally-derived gastrodermal cells and migrate into the mesoglea prior to vitellogenesis. In L. unguiculata, the oocytes develop freely within the mesoglea throughout vitellogenesis, while in S. meleagris each oocyte maintains contact with specialized gastrodermal cells called trophocytes. In the vitellogenic oocytes of both species, numerous invaginations of the oolemma result in the formation of intraooplasmic channels throughout the ooplasm. These channels are intimately associated with cisternae of rough endoplasmic reticulum and may play some role in yolk precursor uptake by substantially increasing the surface area of the oocyte. Vitellogenesis is similar in both species and involves the autosynthetic activity of the Golge complex and rough endoplasmic reticulum, and the heterosynthetic incorporation of yolk precursors through receptor-mediated endocytosis. However, in the oocytes of S. meleagris, the trophocytes probably play a role in the transfer of nutrients from the gastrovascular cavity to the oocyte. The present study suggests that scyphozoans were among the first metazoans to develop ovarian accessory cells during their reproductive evolution. The trophocyte-oocyte association observed in some scyphozoans is similar to but structurally less complex than the trophonema-oocyte association described from anthozoans. Scyphozoan ovarian morphology helps support the view that the Scyphozoa share a closer phylogenetic relationship with the Anthozoa than with the Hydrozoa.     

Oogenesis in the marine mussel Mytilus edulis: an ultrastructural study

Ultrastructural changes occurring during the course of development in oocytes of Mytilus edulis are described for mussels collected at monthly intervals over a period of one year (September 1981 to October 1982) from a site in Cornwall, England. During early stages of oogenesis the oocyte is surrounded by a small number of follicle cells but, as development proceeds, the follicle cells are restricted to the stalk region which attaches the oocyte to the acinar wall. Contact between the follicle cells and the developing oocyte is maintained by means of desmosomelike gap junctions. Organelles and inclusion bodies present in the ooplasm during oogenesis include rough endoplasmic reticulum (RER), Golgi bodies, mitochondria, free ribosomes, Balbiani's vitelline body, annulate lamellae and yolk and cortical granules. The RER, in particular, varies considerably throughout the course of development. Evidence for uptake of exogenous macromolecules into oocytes by pinocytosis is presented; it occurs in the basal region of previtellogenic oocytes prior to the formation of the vittelline coat. Lipid-yolk granules invariably have mitochondria in close association and, during the winter months, develop in close proximity to small, apparently glycogen-rich vesicles possibly suggesting that conversion of glycogen to lipid takes place in developing oocytes. Oocyte degeneration was commonly observed and involves initial breakdown of the plasma membrane followed by rupture of the vitelline coat. The oocyte contents once released into the acinar lumen are resorbed by the epithelial cells of the gonoducts, which are prevalent throughout the mantle of ripe individuals.     

Oogenesis and spawn-formation in the pigmy lion fish Dendrochirus brachypterus (Pteroidae)

Dendrochirus brachypterus possesses a special type of ovary in which the germinative epithelium surrounds a spongy stroma hanging in the lumen. The inner side of the ovarian wall is covered by a special type of epithelium that produces a gelatinous envelope around the gametes (spawn) during reproduction. In general, oogenesis in the lion fish resembles that of other teleosts, the characteristic difference being in the formation of ovigerous peduncles-protrusions of the spongy stroma, each of which bears a single oocyte. During oogenesis the oocytes rise above the germinal epithelium, enveloped in their follicular epithelia. The larger the oocyte the greater the length of its peduncles and the further its position from the germinal layer (Fig. 3). During this phase of development, a marked multiplication of yolk granules occurs; they increase their diameter and finally homogenize at ovulation. Under favorable thermal conditions, oogenesis continues all year round. The peduncular growth of oocytes enables the growing egg cells to move away from the egg-producing surface, thus making space available for the ovary to produce more eggs. This ability should have a survival value for these fish if we take into consideration that the most vulnerable stage in their life history is that of planktonic larvae (Fishelson, 1975).     

Nutrient fluxes at the landscape level and the R* rule

Nutrient cycling in terrestrial ecosystems involves not only the vertical recycling of nutrients at specific locations in space, but also biologically driven horizontal fluxes between different areas of the landscape. This latter process can result in net accumulation of nutrients in some places and net losses in others. We examined the effects of such nutrient-concentrating fluxes on the R* rule, which predicts that the species that can survive in steady state at the lowest level of limiting resource, R*, can exclude all competing species. To study the R* rule in this context, we used a literature model of plant growth and nutrient cycling in which both nutrients and light may limit growth, with plants allocating carbon and nutrients between foliage and roots according to different strategies. We incorporated the assumption that biological processes may concentrate nutrients in some parts of the landscape. We assumed further that these processes draw nutrients from outside the zone of local recycling at a rate proportional to the local biomass density. Analysis showed that at sites where there is a sufficient biomass-dependent accumulation of nutrients, the plant species with the highest biomass production rates (roughly corresponding to the best competitors) do not reduce locally available nutrients to a minimum concentration level (that is, minimum R*), as expected from the R* rule, but instead maximize local nutrient concentration. These new results require broadening of our understanding of the relationships between nutrients and vegetation competition on the landscape level. The R* rule is replaced by a more complex criterion that varies across a landscape and reduces to the R* rule only under certain limiting conditions.     

Diphasy in the advertisement calls of Geocrinia laevis (Anura: Leptodactylidae): vocal responses of males during field playback experiments

Summary The advertisement calls of Geocrinia laevis are diphasic, and consist of a single introductory note, followed by a series of repeated notes; diphasy is based on differentiation in the temporal structure of the two phases. In a series of field playback tests used to investigate the functional significance of diphasy, calling males were presented with one of three types of acoustic stimulus: complete calls (introductory and repeated notes), introductory notes only, or repeated notes only. There were no marked differences in the effects of these stimuli, and all resulted in a reduction in the rates of production of introductory notes and of repeated notes. Playback at levels of 110 dB PSPL and above caused virtual cessation of calling. The results suggest that one of the functions of the advertisement call, the communication of territoriality between males, does not reside in either the introductory note or the repeated notes, so that diphasy in the advertisement call has no apparent functional basis in this context. Whether the attraction of reproductively ripe females is a particular function of either phase remains untested. The advertisement calls of G. laevis are much less diphasic than those of a closely related species, G. victoriana, for which there is a clear partitioning of the functions of communication of territoriality and the attraction of conspecific mates between the introductory notes and the repeated notes, respectively. Furthermore, the acoustic repertoire of G. laevis is less complex than that of G. victoriana in lacking a vocalisation which functions specifically in close-range aggressive encounters between males.     

孕酮诱导非洲爪蟾卵母细胞生发泡破裂(GVBD)实验方法的优化及干扰物质筛查

非洲爪蟾卵母细胞生发泡破裂(GVBD)是生物学上研究卵细胞成熟过程及其机制的良好模型。由于GVBD受激素的调控,曾有研究将孕酮诱导的非洲爪蟾GVBD试验用于内分泌干扰物的筛查。通过预注射人体绒毛膜促性腺激素(HCG)提高非洲爪蟾卵母细胞对孕酮的敏感性、缩小个体差异,缩短试验时间等优化GVBD试验方法;并选用甲氧氯作为阳性参照物对优化的方法进行验证,最后用此方法研究了米非司酮、来曲唑、咪鲜胺3种化学物质对孕酮诱导GVBD的影响。结果发现,甲氧氯对GVBD的发生具有明显抑制作用,随着剂量的增加抑制作用增强,显示优化方法的可靠性。米非司酮作为孕酮受体拮抗剂,没有表现出抑制GVBD的效应,证明孕酮诱导爪蟾GVBD并非完全由孕酮受体(PR)介导。同时,来曲唑和咪鲜胺对孕酮诱导爪蟾GVBD没有影响,显示此两种物质在孕酮诱导GVBD过程中不具有内分泌干扰作用。     

Lebenszyklus,Jugendentwicklung und Geschlechtsorgane von Rhabdomolgus ruber (Holothuroidea: Apoda)

Life-cycle, post-embryonic development, as well as organization and development of gonads, have been investigated in 1,970 specimens of Rhabdomolgus ruber Keferstein (1863), dredged near Helgoland from September 1968 to November 1969. The post-embryonic development is divided into 8 stages differing in number of tentacles. Five secondary tentacles are added, in regular sequence, to the 5 primary tentacles. There is only one reproductive period per year, which lasts from April to May. It is estimated that the life span of individuals ranges over 2 or 3 years. Cultivation experiments corroborate the values for duration of the 4 youngest stages calculated from the results of dredgings. Stage 1 (5 tentacles) lasts more than 44 days, stage 2 (5 to 6 tentacles) 11 days, stage 3 (5 to 7 tentacles) 12 days, and stage 4 (5 to 8 tentacles) 30 days. R. ruber hibernates at stage 5 (8 tentacles). The development of the gonad is analysed in detail from the first anlage in the pentactula to the condition in adult individuals. Eggs develop in the front part of the female gonad; yolk is produced in the inner epithelial layer of the middle part. The eggs migrate through the ovarial connective tissue to the tip of the ovary. R. ruber lives in the uppermost 2 cm of the sediment (“Amphioxus-sand”) near Helgoland (southern North Sea). Moving its tentacles over its mouth, the animal feeds from detritus. R. ruber is confined to the mesopsammal biotope. Adhesive capacity of glandular tentacles, resistance to mechanical damage, and direct ontogeny must be regarded as characteristic adaptations to mesopsammal life. The simple organisation of the gonads and the presumably free discharge of germ cells into the ambient sea water represent phylogenetically primitive properties of the species.     

Vocal competition in male Xenopus laevis frogs

Male Xenopus laevis frogs produce underwater advertisement calls that attract gravid females and suppress calling by male competitors. Here we explore whether groups of males establish vocal ranks and whether auditory cues alone suffice for vocal suppression. Tests of male–male pairs within assigned groups reveal linear vocal dominance relations, in which each male has a defined rank. Both the duration over which males interact, as well as the number of competitive opportunities, affect linearity. Linear dominance across the group is stable for about 2 weeks; rank is dynamic. Males engage in physical interactions (clasping) while paired but clasping and vocal rank are not correlated. Playbacks of advertisement calls suppress calling and calls from high- and low-ranking males are equally effective. Thus, auditory cues alone suffice to suppress vocal behavior. Playback intensities equivalent to a nearby male advertising effectively suppress calling while low-intensity playbacks are either ineffective or stimulate vocal behavior. X. laevis advertisement calls are biphasic, composed of alternating fast and slow click trills. Approximately half the males tested are more vocally suppressed by all slow than by all fast trills; thus, these males can distinguish between the two phases. The fully aquatic family Pipidae diverged from terrestrial ancestors approximately 170 mya. Vocal suppression in the X. laevis mating system may represent the translation of an ancient anuran social strategy to underwater life.     

Factors influencing egg size in the gammarid amphipod Gammarus insensibilis

Developmental and seasonal changes in egg volume were examined in a population of the amphipod Gammarus insensibilis Stock occurring on the south coast of England, towards its northern limit of distribution. Results showed a marked increase in egg volume during development (2.9 times by Egg Stage V), resulting from water uptake and from the conversion of yolk reserves into structural elements. The maximum rate of increase coincides with the period of organ and limb development. At hatching, after initial rupture of the egg membrane by urosome spines, egg volume increases rapidly over a short period (15 to 20 min) by a further 30% (uptake rate 3.6×10^–5 mm³s^–1), followed by a post-hatching decrease in juvenile volume. Increase in size at hatching is the result of drinking by embryos, although changes in body-wall permeability may contribute. Females carrying eggs in an advanced stage of development exhibit egg-collecting behaviour. This is seen as an adaptation to an increased likelihood of egg loss with increase in volume of the brood as hatching approaches. Seasonal changes in Stage I (early) egg size are marked in this species, with winter eggs as much as 60% greater in volume than summer eggs. Egg size is inversely related to the temperature during oocyte development. A simple model has been derived to account for the observed seasonal pattern in egg size. The consequences of seasonal variation in egg and juvenile size are considered.     

Reproduction and development of Sabella media,a sabellid polychaete with extratubular brooding

Known reproductive patterns in the polychaete family Sabellidae include: (1) broadcasting of gametes, (2) depositing of benthic egg masses, (3) brooding outside the lip of the tube, and (4) brooding within the tube. There is little information for sabellids in the third category; there-fore we have studied the reproductive biology of Sabella (=Demonax) media (Bush), one of the few species known to brood its early developmental stages outside the tube. A total of 32 adults of S. media with egg cocoons were collected from the surfaces of compound ascidians (Aplidium sp. and Didemnum sp.) and from holdfasts of a brown alga (Hedophyllum sessile) at Eagle Cove, San Juan Island, Washington, USA, from June 1981 through June 1982, between tidal levels of 0.0 and 0.6 m. The donutshaped cocoons, each containing over 1 000 eggs, are deposited just outside the tube aperture from April through September. Larval development takes place within the cocoon through the 3-setiger stage, at which time the larvae emerge (about 8 d after egg deposition). The newly hatched larvae are demersal and swim near the bottom of the culture dish for 1 d before settlement. Metamorphosis takes nearly a week, and initial formation of the tube is also gradual. The reproductive patterns within the family Sabellidae are discussed, and the adaptive significance of extratubular brooding considered.     

黑斑蛙与非洲爪蟾蝌蚪急性毒性试验方法敏感性的比较

两栖动物蝌蚪急性毒性试验是评价化学品急性毒性的一种方法。以毒死蜱、乙草胺、重铬酸钾和全氟辛烷磺酸盐(PFOS)为测试物,比较了我国本土黑斑蛙(Rana nigromaculata)与国际通用种非洲爪蟾(Xenopus laevis)在蝌蚪急性毒性试验中的敏感性。结果发现：2类蝌蚪分别进行的11次试验中,空白对照组黑斑蛙蝌蚪死亡率(0.9%)远低于非洲爪蟾蝌蚪的死亡率(5.8%);重铬酸钾和PFOS对黑斑蛙蝌蚪的96 h-LC₅₀分别为34.0 mg·L^-1和81.0 mg·L^-1,而对非洲爪蟾蝌蚪的96 h-LC₅₀分别为51.6 mg·L^-1和92.1 mg·L^-1,显示黑斑蛙蝌蚪对这2种化学品的敏感性略高于非洲爪蟾蝌蚪;毒死蜱和乙草胺对黑斑蛙蝌蚪的96 h-LC₅₀分别为0.41 mg·L^-1和4.1 mg·L^-1,而对非洲爪蟾蝌蚪的96 h-LC₅₀分别为0.12 mg·L^-1和3.1 mg·L^-1,显示黑斑蛙蝌蚪对这2种化学品的敏感性略低于非洲爪蟾。鉴于2类蝌蚪对化学品的敏感性存在差异,且黑斑蛙蝌蚪的自然死亡率低,材料更易获得,笔者认为黑斑蛙蝌蚪比非洲爪蟾更适合作为蝌蚪急性毒性试验的材料,用于我国化学品环境管理中的毒性评价。     

Action of eyestalks on the ovary in Rhithropanopeus harrisii and Crangon crangon (Crustacea: Decapoda)

The annual cycle of ovarian activity and eyestalk effects on the ovary in different phases of its activity were examined in the crab Rhithropanopeus harrisii Gould ssp. tridentatus Maitland, and the sand shrimp Crangon crangon L. In both species, the annual ovarian cycle consists of two phases of vitellogenesis and the resting phase. In R. harrisii, the eyestalks exert an inhibitory effect on vitellogenesis during the phase of vitellogenesis outside the breeding season, and are necessary for the process of oviposition during the breeding season. In C. crangon, ovary-inhibiting hormone is present in the eyestalks outside the breeding season, and has not been detected during this season. The resting phase of the ovary after the breeding season is caused by the ovary-inhibitiing hormone. Females of C. crangon are a suitable material for testing ovary-inhibiting hormone activity, while female R. harrisii are not.     

The reproductive biology of echinothuriid and cidarid sea urchins from the deep sea (Rockall Trough,North-East Atlantic Ocean)

The reproductive biology of 5 species of echinothuriid (Phormosoma placenta, Calveriosoma hystrix, Araeosoma fenestrum, Sperosoma grimaldii and Hygrosoma petersii) and 2 species of cidarid (Cidaris cidaris and Poriocidaris purpurata) sea urchins from the deep sea (Rockall Trough) has been examined from samples collected during 1973–1983. In all species the gonads lie within the interambulacrum attached to aboral gonopores and when fully developed occupy most of the test not occupied by the gut or Aristotle's lantern. In all the species, initial oocyte development takes place along the germinal epithelium embedded in nutritive tissue. In all the echinothuriids and in Poriocidaris purpurata, the oocyte grows to ca. 200 to 450 m, at which stage vitellogenesis begins. Oocyte growth continues until a maximum egg size of 1 100 to 1 500 m is attained. In the echinothuriids, two types of nutritive tissue are found. In the carly stages of gametogenesis the oocyte is surrounded by well-structured periodic acid Schiff (PAS)-positive tissue. As the oocyte grows this tissue becomes vacuolated, suggesting that there is a transfer of nutriment to the developing oocyte. In Phormosoma placenta, unspawned oocytes are phagocytosed. There is no evidence of seasonality in any of the echinothuriid species or in Poriocidaris purpurata. Extrapolation with shallow-water echinothuriids suggests that larval development is lecithotrophic, omitting any planktotrophic phase. Of the species examined, only Cidaris cidaris has a reproductive strategy which produces a known larva, although the limited samples did not permit any determination of seasonality in this deep-sea population.     

Pheromone of the elm bark beetle Scolytus laevis (Coleoptera: Scolytidae): stereoisomers of 4-methyl-3-heptanol reduce interspecific competition

Stereoisomers of 4-methyl-3-heptanol (MH) are pheromone components of several Scolytus bark beetles. The elm bark beetle Scolytus laevis (Coleoptera: Scolytidae) has in previous studies been caught in traps baited with commercial MH containing all four stereoisomers, but the lure has been considered a weak attractant. In this study, we addressed the question whether stereospecific responses by S. laevis to stereoisomers of MH might contribute to its niche separation from other sympatric Scolytus species. Using GC–MS, we analyzed extracts of hindguts and abdomens from male and female S. laevis and the sympatric S. triarmatus. We also tested all four MH-stereoisomers individually and in combinations in the field to determine their role for S. laevis. All four stereoisomers were synthesized via a boronic ester method with 1,2-dicyclohexylethanediol as chiral director. In addition, the (3S,4R)-stereoisomer of MH was prepared through enantioselective, lipase-mediated transesterification of a mixture of the four stereoisomers of MH. Females of both species contained small amounts of syn-MH, and males contained trace amounts of anti-MH. The anti stereoisomer (3R,4S)-MH was attractive to male and female S. laevis, whereas the syn stereoisomer (3S,4S)-MH acted as an inhibitor or deterrent and reduced the catch when added to the attractive isomer. The syn isomer is the main aggregation pheromone component of the larger and sympatric S. scolytus and possibly also of S. triarmatus. The avoidance response of S. laevis to the (3S,4S)-stereoisomer may reduce interspecific competition for host trees.