Tanystylum isabellae Marcus, 1940

Müller, Hans-Georg & Krapp, Franz, 2009, The pycnogonid fauna (Pycnogonida, Arthropoda) of the Tayrona National Park and adjoining areas on the Caribbean coast of Colombia 2319, Zootaxa 2319 (1), pp. 1-138 : 46-48

Tanystylum isabellae Marcus, 1940

Fig. 22

Tanystylum isabellae Marcus, 1940: 102 . Hedgpeth 1943: 55. Fage 1949: 29. Sawaya 1950: 73. Stock 1955: 247. Stock 1986: 402.

Tanystylum tubirostre Stock, 1954 :—Bourdillon 1955: 600.

Material: 16.— 2 males (1 ov.), 1 fem. (gravid) ( SMF 1392 ), on Sargassum , mesolittoral, 8.VII.1985 . 3 males (1 ov.), 1 fem., 1 juv. ( SMF 1393 ) from Cnidoscyphus on rocks, mesolittoral, 8.VII.1985 .

20.— 32 males (12 ov.), 18 fem. (11 gravid), 1 juv. ( SMF 1394 ), on Sargassum cymosum , 5 l substratum, 0–0.5 m, 7.VI.1985 . 4 males (1 ov.), 1 fem., 1 juv. ( ZFMK), same locality, 13.VIII.1985 . 3 males (1ov.), 3 fem. ( ZMA 3380 ), same locality, 8.XI.1985 . 60 males (40 ov.), 57 fem. (39 gravid), 53 juv. ( SMF 1395 ), same locality, 7.XII.1985 . 1 fem. (gravid) ( SMF 1396 ), same locality, 7.I.1986 . 81 males (31 ov.), 67 fem. (59 gravid), 35 juv. ( SMF 1397 ), same locality, 12.II.1986 . 27 males (15 ov.), 10 fem. (6 gravid), 1 juv. ( SMF 1398 ), same locality, 3.IV.1986 .

21.— 2 males (1 ov.), 1 fem. ( INVEMAR), on Digenia simplex , 5 l substratum, mesolittoral, 3.IV.1986 .

Description of male: Dorsal trunk outline nearly circular, crurigers touching each other on their entire length; all trunk segments fused. Cephalon bearing a short seta above origin of palps. Ocular process twice as high as basal diameter, abruptly narrowing in its distal half and normally pointed. Eyes large and distinctly pigmented. Crurigers 2–4 bearing 1–2 rounded distal tubercles dorso-laterally. Abdomen relatively short, curved feebly upwards, with about 5 short setae in its distal half. Abdomen surpassing 4 th crurigers by about 1/ 3 of its length. Proboscis bottle-shaped, distal half strongly narrowing and forming a broad tube.

Cheliphores one-articled, very short and distally rounded, barely showing at frontal margin of cephalon, distally with 1–2 short setae. Palp 6-articled, with an indistinct separation between the short 3 rd and the longest 4th article; terminal article almost twice length of penultimate article, with ca. 17 ventral, ventro-lateral and distal setae. Oviger 10-articled; articles 4 and 5 elongate and of equal length; 7 th article with an obtuse tubercle with 4 short spines on top; terminal article the shortest, bearing 2 denticulated leaf-like spines. Legs robust, articles beset with irregularly distributed setae of different lengths; coxae 1 of all legs on their distal rim armed with round tubercles in a antero- and postero-lateral as well as dorsal position; these tubercles mostly with one, seldom 2 short setae; coxae 1 and coxae 3 of same length; coxae 2 1.6 times as long as coxae 1 and coxae 3; cement gland on dorsodistal end of femur with short and little bent tubiform terminal region; tibia 2 slightly longer than tibia 1, both bearing two flat dorsal tubercles; tarsus about as long as broad, ventrally with a short spine and 2 setae; propodus relatively strongly curved, without distinct heel; proximal third of sole with 3 robust spines, distally with about 9 setae and spines; main claw rather strongly bent and of about 1/2 length of propodus; auxiliaries less strongly bent and of 1/4 length of propodus.

Measurements: Trunk length 0.7; width (across 2 nd crurigers) 0.65; abdomen 0.21; proboscis 0.47; 3 rd leg: coxa 1, 0.15; coxa 2, 0.25; coxa 3, 0.14; femur 0.43; tibia 1, 0.38; tibia 2, 0.44; tarsus 0.09; propodus 0.43; main claw 0.22; auxiliary 0.13.

Female: In habitus like male, only the tubercles atop the lateral processes and coxae 1 of all legs much less developed. Oviger much smaller and more slender than in male, 4th and 5 th article shortened, the tiny terminal article armed with a pair of large denticulated flattened spines.

Remarks: The material from Colombia agrees very well with the original description from Brazil — except that articles 3 and 4 are only partly sepatated. The species is closely related to Tanystylum tubirostrum Stock, 1954 , from which it is differentiated by the somewhat more robust proboscis, which is distinctly narrower in its distal half only, as well as the clear round tubercles on top of the coxa 1 (see Fig. 34 ).

Ovigerous males were found all year round except months I, III, V, IX and X, which is an indication of eurychrony. The bulk of the research material comes from Sargassum cymosum in Bahía Concha, where a substantial rise of numbers during the months XII, II and IV seems apparent. As during the research time in month I only a single fem. and in V none at all were sampled, it may be assumed that the species is discontinuously distributed in the substratum sampled. Tanystylum isabellae is an obligate inhabitant of shallow water, which in the research area does not occur in depths under 0.5 m.

Distribution: In the western Atlantic the species was reported from Brazil (Markus 1940b: 102; Hedgpeth 1943b: 55; Sawaya 1950: 73), as well as from the Caribbean islands of St.Thomas and St.John (Stock 1955b: 247). The material recorded by Bourdillon (1955: 600, Pl.III, figs.2–4) from Bermuda as Tanystylum tubirostre corresponds unambiguously with T. isabellae by comparing these figures. The only record from the eastern Atlantic comes from the Congolese coast by Fage (1949: 29).

Figures

FIGURE 22. Tanystylum isabellae Marcus, 1940: A male dorsal, B female dorsal, C male lateral, D female ocular process lateral, E male proboscis and palps ventral, F male palp, G male oviger, H male leg 3, I cement gland duct, J female oviger.

FIGURE 34. Callipallene brevirostris (Johnston, 1837), male: A dorsal, B ocular process lateral, C proboscis ventral, D leg 3, E tarsus and propodus, leg 3, F another tarsus and propodus, leg 3.