ИСТИНА

The chaetal structure of some species of Nephtyidae from the North Polar Ocean has been studied using both stereo compound light microscopy (LM) and scanning electron microscopy (SEM): Aglaophamus malmgreni, A. rubellus, Micronephthys hartmannschroederae, M. minuta, M. neotena, Nephtys assimilis, N. caeca, N. ciliata, N. cirrosa, N. hombergii, N. hystricis, N. kersivalensis, N. longosetosa, N. paradoxa, N. pente and N. rickettsi. All nephtyid chaetae are simple; noto- and neurochaetae are similar. There are four main chaetal types: capillary, barred, chaetae with spines and lyr¬ate (the latter are absent in investigated species). Chaetae that appear smooth under LM usually have at least some small sporadically scattered spines under SEM, but truly smooth chaetae also exist. All barred chaetae are preacicular. Chaetae with spines, and capillary chaetae, are mainly postacicular. The basal regions of chaetae with spines are smooth, and spines appear in sporadically scattered arrangements, gradually becoming more dense but still in irregular rows. In the most ornate cases (spinose chaetae), the spines gradually join together basally, at first in irregular, then regular, rows and form ‘combs’. The number of spines in such combs can increase from 3-4 up to 20-25 along the chaetae. In old chaetae, the combs can become detached as a whole unit. The chaetal morphology is most developed in the middle of a spinose chaeta, and thereafter the pattern and form of the spines changes in reverse order (combs, irregular combs, sporadic spines) terminating in smooth tips. Spinose chaetae of different species and genera can differ in the number of spines forming the combs, the distance between combs, and size of the spines. Some species have ‘combs’ with single spines (so-called serrate chaetae). Other species have no distinct combs at all. Geniculate chaetae are a form of serrate chaetae. Keywords: Nephtyidae, chaetae, structure, taxonomy