Chamaedrilus glandulosus (Michaelsen, 1888)

Martinsson, Svante, Rota, Emilia & Erseus, Christer, 2015, On the identity of Chamaedrilusglandulosus (Michaelsen, 1888) (Clitellata, Enchytraeidae), with the description of a new species, ZooKeys 501, pp. 1-14 : 3-4

Taxon classification Animalia Enchytraeida Enchytraeidae

Chamaedrilus glandulosus (Michaelsen, 1888) sensu stricto Fig. 2

Pachydrilus sphagnetorum var. glandulosus Michaelsen, 1888: 490, plate 23, fig. 2 a–c.

Marionia sphagnetorum var. glandulosa ; Michaelsen 1889: 29.

Marionina glandulosa ; Michaelsen 1900: 74.

Chamaedrilus glandulosus ; Friend 1919: 174, partim.

Enchytraeoides glandulosa ; von Bülow 1955: 257.

Cognettia glandulosa ; Nielsen and Christensen 1959: 43, fig. 30, partim; Schmelz and Collado 2010: 79, partim.

Cognettia glandulosa B; Martinsson and Erséus 2014.

Lectotype.

ZMUH V 429a, mature anterior part, in alcohol, leg. W. Michaelsen, date not given (before 1888).

Type locality.

GERMANY: Hamburg, banks of Bille River, in detritus ("Billeufer, im Detritus") (N 53.54°, E 10.09°).

Paralectotype.

ZMUH V 429b, immature specimen, in alcohol; same collection data as for lectotype.

Additional type material

(not studied). Paralectotypes ZMUH V 429b, 8 specimens in alcohol, same collection data as for lectotype.

Other material.

See Table 1. In total 15 specimens, of which 1 from Finland, one from Norway and 13 from Sweden (whereof one mature and three submature). All specimens except one are DNA barcoded (Table 1).

Diagnosis.

Can be separated from all other European species of Chamaedrilus except Chamaedrilus varisetosus by its unique combination of 2-4 pairs of well-developed secondary pharyngeal glands, two chaetae per lateral bundle in preclitellar segments, and three chaetae in all other bundles, spermathecae with comparatively long ectal ducts, and genitalia shifted forward 3-4 segments (in relation to normal placement in Enchytraeidae ). No characters completely separate this species from Chamaedrilus varisetosus sp. n., but specimens of Chamaedrilus glandulosus are usually larger and have only two chaetae in the lateral bundles of preclitellar segments, whereas Chamaedrilus varisetosus usually has three chaetae in lateral bundles of III-V. Furthermore, Chamaedrilus glandulosus is found in aquatic habitats only (i.e. submerged under water for most of the time), whereas Chamaedrilus varisetosus is found in both aquatic and terrestrial habitats; so far we have not found them occurring together.

Description.

EXTERNAL CHARACTERS: Size: length of 20 anteriormost segments 3.49-6.68 mm, mean 4.55 ± 0.87 (n=11); body width in XII 0.24-0.56 mm, mean 0.42 ± 0.10 (n = 14). Chaetae sigmoid without nodulus, 60-100 µm long, chaetal formula 2,(3)-3:3-3, with 3 lateral chaetae per bundle from VII-IX; in sexually mature specimens, ventral chaetae, or both ventral and lateral chaetae, missing in the segment bearing male pores (VIII or IX). In the sexually mature and submature specimens examined, clitellum poorly developed.

INTERNAL CHARACTERS: Brain concave posteriorly, 160-210 µm long. Pharyngeal glands 3-4 primary pairs; 2-4 pairs of well-developed secondary glands (Fig. 2A), secondary glands behind the first pair of primary glands sometimes missing. Dorsal blood vessel arising in XVI–XX. First pair of nephridia present at 7/8-8/9; nephridia with efferent duct originating antero-ventrally, close to septum; anteseptale consisting of funnel only; postseptale elongate (Fig. 2 C–D). Chloragogen cells granulated; 35-55 µm long. Coelomocytes granulated, round to oval, 25-30 µm long.

Seminal vesicle distinct and unpaired in one specimen (CE18516), poorly developed in all other mature or submature specimens. Other genitalia paired. Sperm funnel about 200 µm long, tapering, 25 µm wide basally, 50 µm wide proximally; collar 55-60 µm wide. Spermatozoa on collar in a few mature/submature worms. Vas deferens long, simple, with several loops, about 12 µm wide. Penial bulb poorly developed, about 25 µm wide, 60-65 µm long (Fig. 2B). Male pores in VIII or IX. Spermathecae paired; pores located slightly below lateral chaetae; ectal duct smooth, 240 µm long, about 17 µm wide; ectal gland 35-40 µm in diameter; ampulla oval, about 150 µm long, not attached to oesophagus (Fig. 2E); sperm in ampulla of lectotype only. Spermathecae confined to V or entering into VI.

Habitat and distribution.

Occurs in freshwater habitats, in sand and gravel bottoms in lakes and small streams, and climbing on vegetation and dead wood in water. Barcoded specimens document occurrence in Finland, Germany, Norway and Sweden, but the species is probably more widely distributed, not only in Europe. For instance, Chamaedrilus glandulosus s. l. has also been reported from North America: the records by Nurminen (1973) and Healy (1996) are insufficiently described and cannot even tentatively be assigned to any of the two species, and the records by Schlaghamerský (2013) and Schlaghamerský et al. (2014) are likely to be Chamaedrilus varisetosus , see under Habitat and distribution for that species.

Biology.

Seems to reproduce mainly parthenogenetically; specimens with developing genitalia are found from June to July (Sweden).

Remarks.

Michaelsen (1888; 1900) described this species as sturdier than Chamaedrilus sphagnetorum , with 2 chaetae per preclitellar lateral bundle and three chaetae in all other bundles. This together with the fact that Michaelsen’s type material was collected at an aquatic site makes us confident that our new material is conspecific with Michaelsen’s species. Michaelsen (1888) described the spermathecae in vivo as very long ("they often project, in spite of much meandering, up to the segment VII") and the ampullae to consist each of an ectal enlargement followed by a long connecting tube and an expanded ental chamber (Fig. 2F). In our new material the spermathecae seem to be either not fully developed or much contracted after fixation: they show simple oval ampullae, not differentiated into ectal and ental compartments. In the mature lectotype we can only follow the spermathecae to what we interpret as the ampullar ectal enlargement. Chamaedrilus glandulosus is larger than Chamaedrilus varisetosus described below. Both the length of the 20 anteriormost segments (P = 1.5E-5) and the width in segment XII (P = 5.5E-5) differ significantly between the two species (Fig. 1).

This species is represented in BOLD by BIN: AAT8923.