Assessing the reproductive biology of the Greenland shark (Somniosus microcephalus).

The Greenland shark (Somniosus microcephalus, Squaliformes: Somniosidae) is a long-lived Arctic top predator, which in combination with the high historical and modern fishing pressures, has made it subject to increased scientific focus in recent years. Key aspects of reproduction are not well known as exemplified by sparse and contradictory information e.g. on birth size and number of pups per pregnancy. This study represents the first comprehensive work on Greenland shark reproductive biology based on data from 312 specimens collected over the past 60 years. We provide guidelines quantifying reproductive parameters to assess specific maturation stages, as well as calculate body length-at-maturity (TL50) which was 2.84±0.06 m for males and 4.19±0.04 m for females. From the available information on the ovarian fecundity of Greenland sharks as well as a meta-analysis of Squaliform reproductive parameters, we estimate up to 200-324 pups per pregnancy (depending on maternal size) with a body length-at-birth of 35-45 cm. These estimates remain to be verified by future observations from gravid Greenland sharks.

Freezing material without electricity.

When collecting in the field, biological samples can be kept cool at 0 C in ice slush, or frozen at -20 C in a crushed ice + salt (NaCl) cold mixture, in well-insulated containers, for several hours or days.

Low detection efficiency of candling as a commonly recommended inspection method for nematode larvae in the flesh of pelagic fish.

The third-stage larvae of the parasitic nematode Anisakis simplex commonly occur in most commercially important fish species from the North Atlantic. In this study, the occurrence and site distribution of Anisakis larvae in various size groups of Norwegian spring spawning herring (Clupea harengus), blue whiting (Micromesistius poutassou), and mackerel (Scomber scombrus) from the Northeast Atlantic was investigated. Although most of the larvae were found in the abdominal cavity, the small proportion lodged in the flesh was sufficient to affect food quality and safety. However, the prevalence of Anisakis larvae in fish fillets varied considerably among the size groups of each species: 15 to 60% in herring, 32 to 77% in mackerel, and 89 to 100% in blue whiting. The commonly recommended nematode detection method in the fish processing industry is candling, i.e., a brief visual inspection on a light table. Comparison of successively more accurate detection methods, i.e., candling, enzymatic degradation, and UV illumination, for fillets of each fish species revealed that only 7 to 10% of the nematode larvae present in the fillets were detected by candling. The candling efficiency was apparently independent of fillet thickness. Thus, candling is not sufficient to detect the majority of the nematodes that are actually present in the fillets of pelagic fish from the Northeast Atlantic. These findings emphasize the importance of adequate deep-freezing of any fresh pelagic fish product, especially if it is intended for consumption in a raw or semiraw state.

Growth, fecundity and sex ratio of adult whaleworm (Anisakis simplex; Nematoda, Ascaridoidea, Anisakidae) in three whale species from the North-East Atlantic.

The growth rate, fecundity, and sex ratio of Anisakis simplex in minke whales (Balaenoptera acutorostrata), porpoises (Phocoena phocoena) and long-finned pilot whales (Globicephala melas) was studied on the basis of material from the North Atlantic. A total of 8,135 mature A. simplex were collected from 24 minke whales, 11 porpoises and eight pilot whales. For both males and females, the prevalence was 100% for all three host species, with a mean intensity of 1,727, 262 and 139, respectively. The mean body length of adult female A. simplex was 126 mm in minke whales, 71 mm in the porpoises and 73 mm in pilot whales; and for males the averages were, respectively, 106 mm, 57 mm and 68 mm. Eggs from the uteri of 32 females of length 87-176 mm collected in minke whale stomachs were counted in a Fuchs-Rosenthal chamber. Total egg production was measured in 14 females cultivated at sea. The female growth period was estimated to be 30-60 days, and apparently all eggs were shed during the last week of life. A female of size 150 mm produces approximately 1.5 million eggs. In the cultivation experiment, about 85% of the total egg production was shed during the first 3 days after spawning started.

Post-embryonic development of Camallanus cotti (Nematoda: Camallanidae), with emphasis on growth of some taxonomically important somatic characters.

In this paper, the quantitative post-embryonic development of the Asian freshwater fish nematode Camallanus cotti Fujita, 1927, is described. Larval and adult morphometrics were obtained by following the parasite's life cycle experimentally using copepods Macrocyclops albidus (Jurine) as intermediate host and guppies Poecilia reticulata (Peters), southern platyfish Xiphophorus maculatus (Günther) and paradise fish Macropodus opercularis (L.) as definitive host. Additionally, adult worms were obtained from heavily infected paradise fish imported from Singapore. It is suggested that the gradual change in proportions of the worm's somatic body parts reflects the specific ecological role of each developmental stage. The free-living infective first-stage larva seems to be adapted for transmission, as indicated by its relatively long tail, designed to generate host-attracting movements, and its non-functional intestine. The second- and third-stage larvae from the copepod intermediate host seem mainly to invest in trophic functionality, i.e., the development of the buccal capsule and the oesophagus, which are crucial structures for the worm's successful establishment in the definitive fish host. Once in the fish intestine, the larvae enter a period of considerable growth. After the fourth (i.e., last) moult, a 72% increase in average female body length occurs. This is accompanied by doubling the average vulva-tail tip distance and the average tail length. The length of the female hind body expands in an accelerating allometric fashion, and seems to be closely linked to the posterior-wards expansion of the uterus. In the males however, growth seems to cease after the final moult. We conclude that female post-maturational body size, but especially the length of the hind body and the tail, are closely related to reproductive state, i.e., the developmental stage of the offspring in the uterus, and, probably, the worms' age. Any future taxonomical studies of camallanids in general, and C. cotti in particular, should thus be aware of the reproductive state of the females used.

The development and morphogenesis of Camallanus cotti Fujita, 1927 (Nematoda: Camallanidae), with notes on its phylogeny and definitive host range.

The freshwater fish nematode Camallanus cotti Fujita, 1927 (Spirurida: Camallanidae) is naturally distributed in East, South and Southeast Asia. During the past three or four decades the species has been disseminated to Europe, North America, Australia and Hawaii, mainly due to the extensive ornamental fish trade. In the present study, its development and larval morphogenesis is described. Newborn first-stage larvae are ingested by copepods and within hours reach the haemocoel, where the worms moult twice. At 22 degrees C ambient temperature, fully-developed third-stage larvae appear on day 11 p.i. After transmission into the fish intestine two further moults occur before the adult stage is reached. At 23 degrees C water temperature, the final moult is initiated around day 33 p.i. in males and between 34 and 42 days p.i. in females. Morphologically the young and older adults are similar, but the buccal capsule of both young males and young females is not yet fully sclerotised. Based on the close similarity in the development and adult morphology of the buccal capsule in C. cotti and three congeners from Europe and North America, we suggest, in general agreement with earlier workers, that the Camallanus Railliet & Henry, 1915 originated in tropical Asia and subsequently radiated to species when adapting to new climatic and/or host-related conditions in the Old World and the New World. C. cotti may thus represent a lineage of speciation which did not apparently involve extensive changes in relation to their natural geographical distribution or definitive host range.