Prosorhochmus nelsoni ( Sanchez, 1973 )

Maslakova, Svetlana A. & Norenburg, Jon L., 2008, Revision of the smiling worms, genus Prosorhochmus Keferstein, 1862, and description of a new species, Prosorhochmus belizeanus sp. nov. (Prosorhochmidae, Hoplonemertea, Nemertea) from Florida and Belize, Journal of Natural History 42 (17 - 18), pp. 1219-1260 : 1248-1249

Prosorhochmus nelsoni ( Sanchez, 1973)

( Figure 7H , Tables 1–4)

Amphiporus nelsoni ( Sanchez 1973)

Prosorhochmus nelsoni ( Maslakova et al. 2005)

Etymology

Specific epithet is derived from the masculine name Nelson.

Type material

Neotype USNM 173164 , coll. Malva Sanchez from the type locality; designated by Maslakova et al. (2005).

Material examined

Prosorhochmus nelsoni ( Sanchez, 1973) . USNM 173162-173164 . Coll. M. Sanchez, Quintero, Chile ; USNM 1019782 , 1019784-6 . Coll. M. Thiel, Coquimbo, Chile .

Diagnosis

Prosorhochmus nelsoni possesses no known morphological apomorphies. It differs from Prosorhochmus claparedii , Prosorhochmus adriaticus , Prosorhochmus americanus and Prosorhochmus chafarinensis by being gonochoric and oviparous ( Sanchez 1973; Maslakova et al. 2005) and, additionally, from P. americanus in lacking welldeveloped purple cephalic glands ( Maslakova et al. 2005, p. 495). Central stylet (S) 49–108 Mm long (84 Mm average) significantly different from that of P. belizeanus sp. nov. but not P. chafarinensis or P. claparedii (p50.05), basis (B) truncated, 74– 132 Mm long (108 Mm average) significantly different from that of P. belizeanus sp. nov. and P. chafarinensis , but not P. claparedii (p50.05); S/B ratio 0.64–1.1 (average 0.79), significantly different from that of P. chafarinensis and P. claparedii , but not P. belizeanus sp. nov. (p50.05). Prosorhochmus nelsoni most resembles gonochoric and oviparous P. belizeanus sp. nov. but differs from it by having acidophilic cephalic glands intermixed with the basophilic mucus cephalic glands in the precerebral and cerebral region, so that they do not form a compact cluster ( Maslakova et al. 2005, Figures 3G–H , 6A–F ).

Habitat, type locality and distribution

Prosorhochmus nelsoni is fully marine and occurs in the mid-intertidal zone on the rocky shore, among the mytilid Perumytilus purpuratus and barnacles Jehlius cirratus according to Sanchez (1973) and on rocks and boulders covered by algal turf, inhabited by a wide variety of marine invertebrates (polychaetes, bivalves, and crustaceans, representing the most abundant groups; Thiel et al. 2001). Prosorhochmus nelsoni is reportedly the most common nemertean species in the rocky intertidal of the Chilean coast (Thiel, pers. comm.). It is commonly found during morning low tides, particularly under overcast conditions. Only known from Chile. Type locality: Quintero (32 ° 469 S, 71 ° 319 W) ( Sanchez 1973); other known localities: La Pampilla Beach near Coquimbo (29 ° 579 S, 71 ° 219 W) ( Thiel et al. 2001), Arica (18 ° 299 S, 70 ° 209 W) and Concepción (36 ° 509 S, 73 ° 039 W), Chile ( Maslakova et al. 2005).

Figures

Figure 3. Prosorhochmus belizeanus sp. nov. (A) Transverse section through the rhynchocoel wall; (B) transverse section through the anterior-most portion of the anterior proboscis. Note the non-glandular epithelium and proboscis nerves (indicated by the arrowheads). (C) Transverse section through the middle region of anterior proboscis; proboscis nerves (arrowheads); (D) longitudinal section through the wall of anterior proboscis showing the delicate layer or inner circular muscles overlaying longitudinal muscles; (E) transverse section through the posterior chamber of the proboscis; (F, G) transverse sections through the cephalic blood vessels showing ‘‘pouches’’ and ‘‘valves’’ (arrowheads); (H) transverse section through the vascular plug; lumen of the mid-dorsal blood vessel marked by an asterisk; (I) transverse section through the lateral nerve cord showing the upper nerve (asterisk) and nerve cord muscles (arrowhead); (J) longitudinal section through the ocelli; anterior to the right; (K) transverse section through the foregut region showing nephridial tubules in cross-section (arrowheads); (L) transverse section at the level of nephridioduct (arrowheads). Scales. (A, B, D, E and J–L): 50Mm; (C): 100 Mm; (F–I): 25Mm. Abbreviations: bgl, basophilic cephalic glands; dvm, dorso-ventral muscles; icm, inner circular muscles; lm, longitudinal muscles; lnc, lateral nerve cord; ogl, orange-G cephalic glands; pb, proboscis; pc, pigment cup of ocellus; pep, proboscis epithelium; plg, vascular plug; rhc, rhynchocoel.

Figure 6. A series of slightly oblique transverse sections of Prosorhochmus belizeanus sp. nov. from precerebral to pyloric region (proboscis is missing). (A) Section through one of the cerebral organ furrows and the anterior ocellus on the opposite side. (B) Posterior ocelli, precerebral septum and cerebral organs (outlined). (C) Cerebral ganglia and brain commissures. (D) Posterior portion of brain. (E) Section through the stomach and nephridia. (F) Pyloric region and ovaries. Scales 100 Mm. Abbreviations: agl - acidophilic cephalic glands, bgl - basophilic cephalic glands, cae - caecum, cg - cerebral ganglia, co - cerebral organ, cof - cerebral organ furrow, dc - dorsal brain commissure, dvm - dorso-ventral muscles, es - oesophagus, lnc - lateral nerve cord, npd - nephridioduct, nph - nephridial tubule, npp - nephridiopore, oct - oocyte, ogl - orange-G cephalic glands, pb - proboscis, pc - pigment cup of ocellus, ps - precerebral septum, pyl - pylorus, rhc - rhynchocoel, rhd - rhynchodeum, vc - ventral brain commissure.

Figure 7. Central stylets. The 100 Mm scale bar applicable to all, except (I). (A, B) Prosorhochmus chafarinensis (specimens from Croatia); (C, D) Arhochmus korotneffi comb. nov. (specimens from Croatia); (E) Prosorhochmus claparedii (specimen from Roscoff, France); (F) P. chafarinensis (after Frutos et al., p. 294, fig.1b); (G) Prosorhochmus americanus (after Gibson et al. 1986, p. 330, plate I, fig. e); (H) Prosorhochmus nelsoni (specimen from Coquimbo, Chile); (I) Prosorhochmus belizeanus sp. nov (200 Mm scale bar).