Comparisons were made between the protein concentrations and protein profiles of uninfected Gammarus pulex and those infected with cystacanths of Pomphorhynchus laevis. Comparisons of the extractable haemolymph volumes from uninfected and infected G. pulex, when related to host tissue weight, showed that there was no difference in the host tissue/haemolymph volume ratio between infected and uninfected individuals. SDS-PAGE of haemolymph samples resolved 36 bands of protein, the major components being band 6(19 kDa) and 21(33 kDa). Densitometric analysis of haemolymph samples showed that infected gammarids had total protein concentrations elevated by 84%. The (88 kDa) subunit was identified as the monomer of the respiratory protein haemocyanin. This band was significantly elevated in infected individuals (one-way ANOVA P < 0.001); increasing from 30 to 45% of the total haemolymph proteins.

The reactive formation of lymphoid follicles and germinal centres in lymph nodes, induced by subcutaneous transfer of in vitro activated splenic adherent cells into syngeneic mice, were studied. Adherent cells were obtained by incubating spleen cell suspensions for 24 h and activated by incubating for 1 h in the medium containing keyhole limpet haemocyanin (KLH) absorbed onto alumina. Some of the treated adherent cells were irradiated with 10 Gy x-rays, while others were either not stimulated or were stimulated with alumina-KLH but killed by repeated freezing and thawing. Examination of adherent cell smears immunostained with antibodies against, F4/80, Mac-1, Mac-2 and NLDC-145 indicated that many adherent cells displayed macrophage markers but few displayed the interdigitating cell marker. Animals transfused with KLH-treated adherent cells with or without irradiation showed a marked increase in the number of lymphoid follicles and germinal centres in draining lymph nodes, whereas those transfused with adherent cells which had not been KLH-treated or which had been killed after KLH treatment displayed no significant change in the number of follicles. These results were interpreted as indicating that following transfusion, antigen-activated adherent macrophages migrated into the draining lymph nodes and induced the reactive formation of lymphoid follicles and germinal centres outside preexisting follicles.

When compared with sea water, most marine invertebrates are isosmotic but show varying degrees of ionic regulation, from accumulation of potassium and calcium to reductions of magnesium and sulphate. A reduction of sulphate in pelagic animals such as jellyfish and salps, and an accumulation of ammonium ions in arrow-worms (Sagitta) contribute to their near-neutral buoyancy. Marked reductions in salinity exclude mahy marine invertebrates. In the Baltic, polychaetes, bivalve molluscs and decapod crustaceans are reduced from 193, ninety-two and sixty-four species in the Belt Sea (salinity S 10-30‰) to three, four and two in the Gulf of Finland (salinity S 5-9‰). The chelicerate Limulus can stand a wide range in salinity, a few insect larvae can tolerate concentrations of 200% sea water, while the branchiopod shrimp Artemia can stand crystallising brine (36-37% NaCl). Very few species can tolerate temperatures of 40°C. One such species is the polychaete Alvinella pompejana, a hydrothermal vent animal at East Pacific Ridge (to the W of S America). The harpacticid copepod Tigriopus living in evaporating rockpools has a lethal temperature of 42°C at a salinity of S 90‰, but at S 8‰ that temperature is 34°C. Lack of oxygen and presence of hydrogen sulphide limit the distribution of animals in certain areas. Most active animals have respiratory pigments in their principal body fluid. Burrowing invertebrates such as Arenicola and Lingula have respectively haemoglobin in the blood and haemerythrin in the coelomic fluid, with mean oxygen capacities of 6 ml O2 per 100 ml in each case, compared to 0·6 and 0·5 ml in sea water at 10° and 20°C.