Microscopical studies of nephtyid chaetae (Annelida: Polychaeta: Nephtyidae) from Northern Europe and Arctic

Abstract

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 lyrate (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.

Nephtys sachalinensis sp. n. (Annelida: Nephtyidae): a new species from the upper sublittoral zone of northeastern Sakhalin Island, the Sea of Okhotsk

“…2e), regular and irregular rows of spines or sporadically scattered spines (see: [13]). In interramal areas of the both parapodial branches there are bun dles of chaetae with very small sporadically scattered spines (Fig.…”

“…n. neuropodial postacicular lamellae, unlike N. hud sonica and N. pente, are 2 times longer than acicular lobes and preacicular parapodial lobes are low and rounded, unlike the elongated bilobed preacicular lobes in N. hombergii. In addition, the new species has no protuberance at the branchial base that are charac teristic of N. hombergii and the proximal surface of the pharynx is covered with verrucae [4,11,13,14,16,18,23,38,39,41].…”

Nephtyidae (Polychaeta, Phyllodocida) from the Red Sea, with record of a new species

“…The descriptions included herein are based on the studied specimens unless otherwise stated. The chaetae were examined under a stereo compound light microscope and descriptions follow the terminology included in Dnestrovskaya & Jirkov (2011). Drawings were prepared from preserved specimens with a camera lucida.…”

One new species of Micronephthys Friedrich, 1939 and one new species of <br />Nephtys Cuvier, 1817 (Polychaeta: Phyllodocida: Nephtyidae) <br />from eastern Australia with notes on Aglaophamus australiensis (Fauchald, 1965) and a key to all Australian species

“…-Augener, 1927: 116.-Rullier, 1965: 18 (non Augener, 1913. Dnestrovskaya and Jirkov (2011) have recorded the presence of spinose chaetae (same as spinulated of Ravara et al 2010a) in A. malmgreni (Théel, 1879) so this apomorphy needs to be revisited and shows the need to examine nephtyid chaetae under the SEM to clarify the ornamentation of the capillary blades. Ravara et al (2010a) also suggest that other characters such as the presence or absence of lyrate chaetae, arrangement of papillae on the pharynx and shape of nuchal organs should also be taken into account.…”