Larvae In Seawater Research Articles

Phocanema decipiens (Nematoda: Anisakinae): experimental infections in marine copepods

Gravid female Phocanema decipiens were recovered from the stomachs of freshly killed harbour (Phoca vitulina) and grey seals (Halichoerus grypus). Ova dissected from the nematodes were incubated in seawater and the mean time to hatch varied from 8 days at 20 °C to 52 days at 5 °C. Posthatch survival of ensheathed larvae in seawater varied from 48 h at 20 °C to 140 days at 5 °C. Fifteen species of copepods collected from the North West Arm, Halifax, N.S., were exposed to freshly hatched larvae of P. decipiens. Exsheathed larvae of the parasite were subsequently detected in the haemocoel of 12 harpacticoid species including Danielsennia typica, Tisbe furcata, Ameira longipes, Enhydrosoma curticauda, and various undescribed species of the genera Halectinosoma, Tisbe, Alteutha, and Phyllothallestris and the family Diosaccidae. Phocanema decipiens also occurred in a cyclopoid copepod (Paracyclopina sp.) but calanoid copepods (Eurytemora sp. and Pseudocalanus sp.) did not become infected. The heaviest infections occurred in mature female copepods and prevalence and intensity of infection varied with host species. Adult male copepods and fifth copepodite females were lightly infected. Infected copepods survived for 3–7 days at 15 °C, 10–15 days at 10 °C, and 20–35 days at 5 °C. During the course of infection, larval P. decipiens grew an average of 60% and maximum of 130% in length but underwent little or no morphological change.

The anal portion as a salt-excreting organ in a seawater mosquito larva,A�des togoi Theobald

Larvae of the marine mosquito,Aedes togoi Theobald, tolerate environmental salinities ranging from fresh water to 300% sea water. When they were transferred from fresh water to sea water, sodium concentration in the haemolymph increased for the first 2 days and decreased to the seawater-adapted level within 4 days. When transferred from sea water to fresh water, the sodium concentration decreased markedly for the first 2 days and attained the freshwater adapted level after 4 days. When the larvae in sea water were ligated near the anus, they died within 3 days, showing an increased sodium level in the haemolymph. The larvae ligated at the neck lost considerable body weight and died within 4 days.

Osmoregulation in the Larva of the Marine Caddis Fly, Philanisus Plebeius (Walk.) (Trichoptera)

ABSTRACT The larva of Philanisus plebeius is capable of surviving for at least 10 days in external salt concentrations from 90 mm/l sodium chloride (about 15% sea water) to 900 mm/l sodium chloride (about 150% sea water). Over this range the osmotic pressure and the sodium and chloride ion concentrations of the haemolymph are strongly regulated. The osmotic pressure of the midgut fluid and rectal fluid is also strongly regulated. The body surface of the larva is highly permeable to water and sodium ions. In sea water the larva is exposed to a large osmotic flow of water outwards across the body surface. This loss is replaced by drinking the medium. The rectal fluid of larvae in sea water, although hyperosmotic to the haemolymph, is hypo-osmotic to the medium, making it necessary to postulate an extra-renal site of salt excretion. Measurements of electrical potential difference across the body wall of the larva suggest that in sea water this tissue actively transports sodium and chloride ions out of the body.