Validation of age determination using otoliths of the European anchovy (Engraulis encrasicolus L.) in the Bay of Biscay

Validation of the age determination procedure using otoliths of European anchovy in the Bay of Biscay was achieved by monitoring very strong year-classes in successive spring catches and surveys, as well as the seasonal occurrence of edge types. Historical corroboration of the ageing method was obtained by cross-correlation between successive age groups by year-classes in catches and surveys (1987–2013). Summary annual growth in length is also presented. Yearly annuli consist of a hyaline zone (either single or composite) and a wide opaque zone, disrupted occasionally by some typical checks (mainly at age-0 and age-1 at peak spawning time). Age determination, given a date of capture, requires knowledge of the typical annual growth pattern of otoliths, their seasonal edge formation by ages and the most typical checks. Most opaque growth occurs in summer and is minimal (translucent) in winter. Opaque zone formation begins earlier in younger fish (in spring), and this helps distinguish age-1 from age-2+.

Evidence for the Presence of a Metamorphic Check in Capelin (Mallotus villosus) Otoliths and Implications for Age Determination

The otolith method of aging capelin (Mallotus villosus) from the estuary and western Gulf of St. Lawrence was validated. Hyaline zones are deposited annually in the late fall and winter and thus can be used in age determination. Back-calculated mean length at the first hyaline zone corresponded well with the average length of capelin larvae collected in November and this zone is interpreted as the first annulus. The mean size at the second hyaline zone corresponded exactly with the length at which capelin undergo a profound metamorphosis. This second hyaline zone, which is laid down in the summer of the 2nd yr, was thus interpreted to be a metamorphic check. The third hyaline zone, deposited at a mean length of 95 mm, which corresponded with the peak in the length frequency distribution (when allowance was made for growth), was interpreted as the second annulus. Analysis of two otolith aging techniques currently used suggests that the "Newfoundland" method misinterprets the metamorphic check as the first annulus, rejecting the true first annulus as a "larval check,” a feature having no biological basis in fact. This results in correct ages, but estimates of lengths at the first annulus are exaggerated. The "Greenland" or "Danish" method may misinterpret the metamorphic check as the second annulus thereby resulting in erroneous ages. Key words: capelin, Mallotus villosus, otoliths, age verification, Gulf of St. Lawrence

The fine structure of conidial development in the genus Torula. III. T. graminis Desm.

Torula graminis produced blastoconidia in acropetalous chains after the evagination of a characteristic conidiogenous cell. Conidia consisted of up to 15 cells and their cell wall was differentiated into an outer melanized zone and an inner hyaline zone. A consistent cytoplasmic feature of conidial cells was the presence of dictyosomal-like membranous stacks often closely associated with the nucleus. Vesicles that developed from the dictyosomal-like cisternae were probably involved in conidial wall synthesis.

The fine structure of conidial development in the genus Torula. I. T. herbarum (Pers.) Link ex S. F. Gray and T. herbarum f. quaternella Sacc.

Conidiogenesis in Torula herbarum and T. herbarum f. quaternella was observed by scanning and transmission electron microscopy. Conidia of the former were shown to be made up of three equally sized cells capped by a distinctive, and easily recognizable, conidiogenous cell. Conidiogenous cells also arose terminally on erect hyphae and on prostrate hyphae. The single-layered conidial cell walls were differentiated into an inner hyaline zone and an outer electron-dense zone formed by the deposition of melanin. Conidiogenous cells lacked melanin at the apex and, before conidiation, the lateral walls were strengthened by a further deposition of melanin. The apex bulged outwards and was modified into a new multicelled conidium bearing another apical conidiogenous cell. Continued development of new conidia resulted in an acropetal chain which became disarticulated after cytolysis within the conidiogenous cell. The relative distinctions between holoblastic and enteroblastic development are discussed and it is concluded that the conidia should be referred to as blastoconidia.

Otolith Age Validation of Greenland Halibut (Reinhardtius hippoglossoides)

Length and age distribution, together with evidence indicating the annual formation of an opaque and translucent hyaline zone on the otoliths of Greenland halibut (Reinhardtius hippoglossoides), point to the validity of using otoliths in age determination. The high incidence of opaque zones during July–October suggests that these fish grew fastest during this period. Young fish appeared to have a longer annual growth period than the older specimens.

Development and structure of the aleuriospores of Humicola grisea Traaen

Aleuriospores of H. grisea are bounded by a thick, single-layered cell wall differentiated into an outer, electron-dense melanized zone and an inner, hyaline zone. Melanization was initiated at the periphery of the cell wall and progressed inwards towards the cytoplasm. To distinguish between chlamydospores and aleuriospores, the presence of a secondary cell wall in the former and the presence of a partially melanized, single-layered cell wall in the latter might prove a useful criterion in distinguishing between the two spore types. However, before such a distinction is made, similar studies on other aleuriospore-producing species are necessary.

Cytological and cytochemical studies of centrifuged eggs of the slug Avion ater rufus L.

The stratification of various cell organelles and of important chemical substances have been studied in the eggs of the slug, after moderate centrifugation. As in other molluscs the egg contents stratify typically into three well-defined zones - lipid, L hyaline and yolky zones - but a distinct equatorial band of inclusions consisting mainly of F phagosomes and associated lysosomes was detected in the most centrifugal region of the hyaline zone. The sub-stratification of various cell inclusions in their respective zones was determined in some detail. The role of the cell membrane and egg cortex in the redistribution of these inclusions and the nature of the ergastoplasm are discussed in the light of electron-microscope studies of eggs of this slug and of the sea urchin.