Chamaedrilus asloae, Martinsson & Klinth & Erséus, 2018

Martinsson, Svante, Klinth, Mårten & Erséus, Christer, 2018, A new Scandinavian Chamaedrilus species (Clitellata: Enchytraeidae), with additional notes on others, Zootaxa 4521 (3), pp. 417-429 : 420-421

Chamaedrilus asloae sp. nov.

Figure 1 A–E

Holotype. . ZMBN126053 , specimen CE32716, immature, anterior part on slide, COI barcode, GenBank acc. no. MH 810224 , leg. Christer Erséus & Mårten Klinth, 2 Jun 2017.

Type locality. NORWAY: Akershus, Baerum, Sandvika, Sandvikselva River , in sandy river sediment close to the river bank ; N 59.8932, E 10.5094.

Paratypes. ZMBN126052 , specimen CE32715, immature, anterior part on slide, COI barcode, GenBank acc. no. MH 810230 , from type locality, same collection data as for holotype ; ZMBN126054 , specimen CE32735, immature, anterior part on slide, COI barcode, GenBank acc. no. MH 810228 ; NORWAY: Akershus, Baerum, Sandvika , Sandvikselva River , in sandy, gravelly river sediment in the middle of the river; N 59.8933, E 10.5094, same collection data as for holotype ; ZMBN126055 , specimen CE32736, immature, anterior part on slide, COI barcode acc. no. MH 810229 ; same locality and collection data as for second paratype above.

Other material. Three immature specimens on slides, one from Svartån River, Örebro, Sweden (CE27752), one from Frognerelva River, Oslo, Norway (CE26608), and one from Askelunden Forest, Mols Bjerge, Denmark (CE35144), see Table 1 for more details.

Etymology. The species epithet asloae is a noun in the genitive case formed of the Latin name for the capital of Norway, Oslo; two of the four localities where the species was found are in or close to Oslo.

Diagnosis. The species can be separated from all other Chamaedrilus species, except C. chalupskyi Martinsson, Rota & Erséus, 2015a on the basis of the following combination of characters: 2 chaetae in lateral bundles in II, 3 in all other bundles, 4–6 pairs of pharyngeal glands, 0-2 pairs of pharyngeal glands fused dorsally; dorsal blood vessel originates posterior to segment XV.

Description. External characters: Size: length of 20 anteriormost segments 3.2–4.2 mm, mean 3.8± 0.42 mm (n=5); body width in XII 0.24–0.43 mm, mean 0.34± 0.07 mm (n=6). Chaetae ( Fig. 1 D–E) sigmoid without nodulus, 55–90 µm long, chaetal formula 3–3(4):3–3, but with only 2 chaetae in the lateral bundles of II. Internal characters: Brain ( Fig. 1C ) slightly concave posteriorly, 150–240 µm long, about 1.5–2 times as long as broad. Pharyngeal glands ( Fig. 1 A–B, arrows) 4–6 primary pairs, sixth pair rudimentary if present, 0–2 anteriormost pairs dorsally fused, pair 4 and/or 5 with ventral lobes; development is irregular and glands are often smaller, or completely missing at one side, but present at the other. Dorsal blood vessel arising in XV–XVI. First pair of nephridia present at 8/9–9/10; nephridia ( Fig. 1F ) about 100–130 µm long, with efferent duct originating anteroventrally, close to septum in preclitellar segments, in postclitellar segments duct originating in middle of postseptale; anteseptale consisting of funnel only; postseptale elongate. Chloragogen cells 30–55 µm long. Coelomocytes finely granulated, round to oval, about 15–30 µm long, concentrated to posterior part of body.

One specimen (Paratype CE32715) with developing testes and sperm funnels in VIII and developing ovaries in IX, but these organs are too undeveloped to be further described. All other specimens immature.

Habitat and distribution. Mainly benthic, so far found in three rivers, Frognerelva and Sandvikselva in South-East Norway, and Svartån in South-Central Sweden, as well in wet soil in a deciduous forest in Central Denmark. The specimen from Frognerelva was found in sandy soil in a pond, with slowly flowing water directly connected with the river, in Sandvikselva the worms were found in sandy sediment with some gravel, two close to the shore (CE32715, CE32716) and two in the middle of the river (CE32735, CE32736), and in both places with rapid water moment above. The Svartån individual was also found in sandy sediment in a fast-flowing stretch of the river. At the Danish site at Askelunden also the aquatic Stylodrilus heringianus Claparède, 1862 (Lumbriculidae) was found, which indicates groundwater seepage.

Biology. The main mode of reproduction is unknown. One specimen (CE27752, from Sweden) had a regenerating head, and one paratype was in early stages of sexual maturity.

Remarks. No morphological characters clearly separating this species from C. chalupskyi were found in the studied specimens, and the two taxa must be considered a pair of cryptic species. In our scrutiny of the limited material of C. asloae , we did note a tendency for the new species to have fewer (only 0–2) pairs of pharyngeal glands that are fused dorsally than what is the case for C. chalupskyi (normally with 2–4 such pairs), but the state of this character is not always easy to determine in whole-mounted worms. The new species is also similar to C. valeriae ( Dumnicka, 2010) , only known from a stream in the Italian Alps. Both species share the fused anterior pharyngeal glands (2 pairs fused in C. valeriae ), presence of ventral lobes on some pharyngeal glands (present on 2–3 pair in C. valeriae ), and a more posterior arising of the dorsal blood vessel (arises in XXII in C. valeriae ), but C. valeriae has a mix of 2 and 3 chaetae in the preclitellar lateral bundles ( Dumnicka 2010; Martinsson et al. 2015a).

Figures

FIGURE 1. Chamaedrilus asloae sp. nov. A. Habitus of anterior part of body in dorsal view; pharyngeal glands marked with arrows (Holotype) B. Habitus of anterior part of body in lateral view, showing the size, shape and number of pharyngeal glands (arrows) (specimen CE26608). C. Brain, dorsal view (Holotype). D. Chaetal bundles in segments II and III (Paratype CE32736). E. Lateral chaetal bundle in segment XLI (Paratype CE32736). F. Nephridium, at 17/18, ventral view (Paratype CE32735). Abbreviations: b = brain; f = funnel; np = nephridial pore. Scale bars 100 µm.