Stratiodrilus circensis Steiner & Amaral, 1999

Daudt, Luiz C. C. & Amato, José F. R., 2007, Morphological variation of Stratiodrilus circensis (Polychaeta, Histriobdellidae) from a new host, Aegla leptodactyla (Crustacea, Anomura, Aeglidae) with identification of its type host species *, Zootaxa 1450, pp. 57-62 : 58-60

Stratiodrilus circensis Steiner & Amaral, 1999

( Figs. 1–12 )

Description (based on 82 mounted specimens)

Male (n = 28) ( Figs. 1 , 3–4 ): 730–1230 in total body length (892.4; 125.2). Head 100–180 long (143.7; 16.7) with five antennae; median antenna (T1) as long as the first lateral pair (T2), both unsegmented; second lateral pair (T3) bisegmented, twice as long as the length of T2. Three pairs of lateral, unsegmented cirri (C1, C2, C3) a little longer than T2 length, with a pair of posterior cirri (C4) as long as C1-C3 length, with adjacent, conical ventral lobes (Lb), half, shorter or as long as C4; each posterior locomotor appendage with two tubercles (Tu). Posterior locomotor appendages (Pl) 349.6–580 long (450.3; 50.5). Jaw apparatus (Ja) 77.7– 160.9 long (114.1; 22.7) not reaching the limit with the first trunk segment; fulcrum (Fu) 30–100 long (62.2; 19.3). Penis (Pe) 38.8–122.1 long (71.0; 19.2; n = 22). Claspers (Cl) 83.2–88.8 long (86.0; 3.9; n = 2). Female (n = 25) ( Figs. 2 , 5–6 ): 710.4–1120 in total body length (864.7; 97.2). Head 127.6–180 (142.4; 12.8) long. Birth pores (Bp) immediately behind C3 ( Fig. 2 ). Posterior locomotor appendages 344.1–540 long (443.6; 44.4). Jaw apparatus 77.7–150 long (112.2; 16.7); fulcrum 33.3–100 long (60.3; 16). Number of eggs (Eg) per female, 0–5.

Host: Aegla leptodactyla Buckup & Rossi, 1977 .

Hosts deposited: Coleção de Crustáceos UFRGS Nº 4119 to 4147. The type host specimen as well as two other specimens of A. schmitti , collected from Rio Piraquara, State of Paraná, were deposited in the same collection under Nº 4175.

Site of infestation: Branchial chamber.

Locality: Rio da Divisa, locality of Silveira, Municipality of São José dos Ausentes, RS, Brazil (28º38’17”S, 049º57’46”W).

Prevalence: 70%.

Intensity of infestation: 1 to 41 (arithmetic mean 13.3; SD 10.4).

Deposited specimens: Ex. A. leptodactyla - adult male CHIOC Nº 36.837 (SBA 1907-2-11); adult female CHIOC Nº 36.838 (SBA 1910-2-19); juvenile male CHIOC Nº 36.839 (SBA 1907-2-3); juvenile female CHIOC Nº 36.840 (SBA 1910-2-5); adult male INPA Nº 127 (SBA 1907-2-12); adult female INPA Nº 128 (SBA 1907-2-4); juvenile male INPA Nº 129 (SBA 1907-2-13); juvenile female INPA Nº 130 (SBA 1907-2- 14); and juvenile male MZUEC Nº 150 (SBA 1907-2-18); adult female MZUEC Nº 151 (SBA 1907-2-1); adult male MZUEC Nº 152 (SBA 1907-2-6); juvenile female MZUEC Nº 153 (SBA 1910-2-9). Ex. A. schmitti - adult male MZUEC Nº 154 (SBA 2084-2-1) and adult female MZUEC Nº 155 (SBA 2084-2-3).

Specimens examined: 11 specimens of S. circensis (mounted in toto) from Rio Carvalho, collected from the branchial chamber of A. schmitti .

Figures

FIGURES 1 – 2. Stratiodrilus circensis. 1. diagram, male in ventral view; 2. diagram, female in ventral view. T 1 — median antenna, T 2 — first lateral pair of antennae, T 3 — second lateral pair of antennae, Ja — jaw apparatus, Ala — anterior locomotor appendages, Fu — fulcrum, C 1 - C 3 — lateral pairs of cirri, Cl — claspers, Eg — egg, Pe — penis, Bp — birth pores, Pla — posterior locomotor appendages, Tu — tubercles, Lb — conical ventral lobes, C 4 — posterior pair of cirri. Scale bars = 300 µm.

FIGURES 3 – 6. Stratiodrilus circensis. 3 – 4. males with short and long antennae, cirri, conical ventral lobes, and tubercles, respectively; 5 – 6. females with short and long antennae, cirri, conical ventral lobes, and tubercles, respectively. Scale bars = 250 µm.

FIGURES 7 – 12. Stratiodrilus circensis. Diagram of the posterior locomotor appendages, showing the progressive variation in length of the conical ventral lobe in relation to C 4 in the different length classes of C 4 (‘ normal’, ‘ intermediary’, and ‘ long’). Scale bars = 50 µm.