Haplosyllis gula Treadwell, 1924

Lattig, Patricia & Martin, Daniel, 2009, A taxonomic revision of the genus Haplosyllis Langerhans, 1887 (Polychaeta: Syllidae: Syllinae), Zootaxa 2220, pp. 1-40 : 20-23

Haplosyllis gula Treadwell, 1924

( Figs 13 A–I, 14 A–H)

Haplosyllis gula Treadwell, 1924: 11 –12, pl. II. fig. 19–23.— Hartman, 1956: 251.

Examined material. Barbados, Caribbean Sea. 11 types USNM 20327, attached to polychaete hosts (3 to an unidentified glycerid, 8 to a unidentified eunicid) and 3 non-attached; 2 prepared for SEM). Collected by the Barbados-Antigua Expedition of 1918.

Description. Body translucent, slender, fragile, small. Length 2.5–3.8 mm, for 26–31 segments, width 0.23–0.27 mm, excluding parapodia. Anterior end wide, with noticeable broad pharynx, becoming gradually thinner from midbody to posterior end ( Figs 13 A, 14A). Preserved specimens yellow-pale. Prostomium subpentagonal, wider than long, difficult to observe due to broad pharynx; two pairs of small red eyes in trapezoidal arrangement. Median antenna with 17–27 articles, inserted on medium of prostomium; lateral antennae with 8–11 articles, inserted on anterior margin of prostomium. Palps long, broadly triangular, fused at their bases, separated all along their length; with cilia on ventral side. Pharynx reddish-brown, broad (0.14 – 0.26 mm wide), short, about 0.3 mm long, reaching to proventricle as funnel, extending about three segments; anteriorly, with small tooth, crown of 11–12 soft papillae, and an inner ring of short, numerous cilia ( Fig. 14 B–C). Papillae with cilia on ventral base and upper side. Proventricle cylindrical, dark-brown, 0.31– 0.42 mm long, extending 3–4 segments, about 0.2 mm wide, with 23–27 muscular cell-rows ( Fig. 13 A). Peristomium well defined, shorter than subsequent ones. Dorsal tentacular cirri (8–18 articles) longer than ventral ones. Dorsal cirri slender, slightly shorter at the tip, similar to antennae and tentacular cirri ( Fig. 13 A– B). First cirri long (19–29 articles), second small (7–13 articles), third and fourth slightly longer than second (12–14 and 21–26 articles, respectively), fifth small (6–11 articles) and sixth long (16–18 articles) ( Fig. 13 A). Subsequent cirri long, some exceed body width, gradually decreasing to posterior end, alternating with short (5–7 articles) and long (15–19 articles). Posterior cirri small (1–7 articles) ( Fig. 13 B). Ventral cirri triangular, anterior ones similar or longer than parapodial lobes ( Figs 13 C, 14D); posterior cirri very short ( Figs 13 D, 14E). Chaetae bidentate, all similar, US of MF with small denticles (only visible under SEM). Anterior chaeta smaller, with MJP straight and long ( Figs 13 E, 14F). Two chaetae per midbody parapodia, with LMF similar than SW; apical teeth long, distal one slightly smaller than proximal tooth; longer chaeta with MJP point straight and long ( Figs 13 H, 14G), short and slightly curved in smaller chaeta ( Figs 13 G, 14H). Aciculae stout, with curved tip 90º bent; two on anterior parapodia, one on midbody parapodia ( Fig. 13 F, I).

Reproduction. Unknown.

Host. Unknown. Probably a facultative parasite of other polychaetes. Types found attached to unidentified glycerid and eunicid polychaetes.

Distribution. Barbados, Caribbean Sea.

Remarks. Haplosyllis gula was described by Treadwell (1924). Since then, the species has only been mentioned in Hartman’s (1956) catalogue. According to our observations, the type material is in excellent condition, except some specimens having broken antennae. The shape of prostomium is difficult to distinguish due the presence of its noticeably broad, dark-red pharynx. These unusual characteristics together with the long, triangular anterior ventral cirri, make it easy to recognise.

Most specimens of the type series were firmly attached to the branchiae or dorsal cirri of other polychaetes. The broad pharynx of H. gula seems to be an adaptation to an ectoparasitic mode of life. The number of ectoparasitic polychaetes reported to remain firmly attached to their respective host is very few. In addition, like H. gula and with a few exceptions, they are only known from their original descriptions, which are often based on a single or a very few specimens ( Martin & Britayev 1998).

In addition to Haplosyllis gula , two specimens of Haplosyllis reported as H. cephalata by Treadwell (1909), were found attached to parapodial cirrus of an unknown eunicid host. No specific modifications were reported, but only the basal section of the host cirrus retained its form inside the pharynx of the parasite, and the distal part was apparently disintegrated and digested inside the parasite’s gut. These two specimens were not described and it is not mentioned if were deposited or not in a collection. Taken into account the geographical proximity and the similar habits and host, we suggest that they may correspond to H. gula instead of H. cephalata . Two more syllids have been reported as sucking ectoparasites: Haplosyllides aberrans (Fauvel, 1939) found inside the ventral brood pouch of the shrimp Platycaris latirostris Holthuis, 1952 , attached to a pleopod of the host (Martin et al. 2008) and Parasitosyllis claparede , was attached to an unidentified polychaete with the help of a highly modified pharynx ( Potts 1913), but also the polynoid Thormora johnstoni (Kinberg, 1855) , which lives in the burrows of the palolo worm, Palola viridis Gray, 1847 , was similarly attached to the caudal part of the host ( Hauenschild et al. 1968).

Figures

FIGURE 13. Haplosyllis gula. A—anterior end, dorsal view; B—posterior end, dorsal view; C—anterior parapodium; D—posterior parapodium; E—anterior chaeta; F—anterior aciculae; G—shortest chaeta, midbody; H—largest chaeta, midbody; I—posterior acicula. Scale bars: A – B = 200 Μm; C – D = 100 Μm; E – I = 20 Μm.

FIGURE 14. SEM micrographs of Haplosyllis gula. A—whole body, ventral view; B—anterior end, ventral view; Cciliated sensory organs, pharyngeal papillae; D—anterior parapodia; E—midbody parapodia; F—anterior chaeta; Glargest chaeta, midbody parapodium; H—smaller chaeta, midbody parapodium. Arrows in C indicating cilia of pharyngeal papillae, in D and E pointing ventral cirri. Bars in G and H indicate MJP. Scale bars: A = 500 Μm; B = 200 Μm; D – E = 100 Μm; C, G = 10 Μm, F, H = 5 Μm.