Pycnogonum cessaci Bouvier 1911
Creators: name: Müller, Hans-Georg
name: Krapp, Franz
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Pycnogonida
Pantopoda
Pycnogonidae
Pycnogonum
Pycnogonum cessaci

description: Pycnogonum cessaci Bouvier, 1911   
Fig. 64  
 Pycnogonum cessaci Bouvier, 1911: 72. Child 1975: 72. Stock 1986: 405. Stock 1990: 231.   
 Material: 17.— 1 fem. (INVEMAR), among stone blocks with Cnidoscyphus, lower mesolittoral, 7.VI.1985. 1 male (ZMA 3377), among stone blocks with Cnidoscyphus, lower mesolittoral, 8.VII.1985. 1 juv. (SMF 1209), among stone blocks with Cnidoscyphus, lower mesolittoral, 9.VII.1985. 1 male, 2 juv. (SMF 1210), among stone blocks with Cnidoscyphus, lower mesolittoral, 8.XI.1985. 4 juv. (SMF 1211), on short algal turf on stone blocks, mesolittoral down to about 0.5 m, 7.I.1986.   
 19.— 1 fem. (ZFMK), Thalassia, 5l substratum, 0.5–4 m, 7.I.1986.   
 20.— 1 juv. (SMF 1212), on Sargassum cymosum, 5l substratum, mesolittoral - 0.5 m, 9.IX.1985. 1 male, 2 fem., 4 juv. (SMF 1213), on Sargassum cymosum, 5l substratum, mesolittoral, 7.I.1986. 4 juv. (SMF 1214), on Sargassum cymosum, 5l substratum, mesolittoral, 12.II.1986, 2 fem., 1 juv. (SMF 1215), on Sargassum cymosum, 5l substratum, mesolittoral, 3.III.1986.   
 21.— 1 juv. (SMF 1216), on Digenia simplex, 5l substratum, mesolittoral, 13.VIII.1985.   
 31.— 1 juv. (SMF 1217), under stones, mesolittoral, 9.IV.1986.   
 45.— 1 male (ZSM), on algae, hydroids and bryozoanson rock, 6–10 m, 25.IX.1985.   
 Description of male: Robust, dorsal trunk outline oval, all segments separate. Crurigers separated by half of their diameter; dorso-distally with flat tubercles, each topped by a short seta; these tubercles absent on the first crurigers in some specimens. Segments 1–3 each with a rounded tubercle in dorso-median line, each of these tubercles bearing 1–2 short setae. Ocular process flat and broadly rounded, eyes darkly pigmented. Abdomen directed horizontally, overtopping the 4 th crurigers with 4/5 of its length.   
Proboscis robust, cylindrical, 1.5 times as long as diameter, bearing sparse short setae. Oviger 7-articled and without setae, small; all articles short, terminal one claw-like.  
Legs very robust, sparsely setose; coxae 1–3 of similar length; femur the most robust and longest article, with flat round ventroproximal tubercle; tibia 1 1.2 times as long as tibia 2; tarsus as long as broad, with 4 short setae ventrally; propodus moderately curved, rather slender and without heel; sole slightly concave, with 3–10 short setae in distal half; main claw relatively strongly curved and robust, 2/5 length of propodus; auxiliary claw slender, 1/5 length of main claw.  
 Measurements: Trunk length 1.24; width 0.49 (across 1 st crurigers); length of abdomen 0.25; length of probosics 0.32; length of articles of leg 3: coxa 1—0.12; coxa 2—0.14; coxa 3—0.12; femur 0.21; tibia 1— 0.20; tibia 2—0.17; tarsus 0.08; propodus 0.25; main claw 0.10; auxiliary claw 0.02.   
 Female: In habitus like male apart from the lack of ovigers, but mostly slightly larger.   
 Larva: First trunk segment with a broad cephalon part, ocular process very flat; trunk in dorso-median line with 3 flat round knobs; crurigers 1–2 dorso-distally each with short seta; proboscis cone-shaped, distally not longer than chelae. Palps and ovigers are three-articled clasping extremities, distal articles hook-shaped. Legs 1–2 normally formed, leg 3 a stump, leg 4 not yet present. Total length 0.4.   
 This stage corresponds to larval stage V of laboratory-raised Pycnogonum litorale Strøm, 1762 in Behrens (1981). It is the stage coming before the post-larva of P. litorale with 3 pairs of completely developed legs and stump-like legs of fourth pair.   
 Postlarva: The dorso-median knobs on the crurigers absent and in their place of segments 2–4 a short seta; leg 4 a mere stump, without articulation, not longer than abdomen. Total length 0.74.   
 Remarks: P. cessaci is possibly most-closely related to Pycnogonum pusillum Dohrn, 1881, which is distributed from the European Mediterranean, down the western coast of Africa to South Africa. Morphologically both species are nearly identical, but the terminal and auxiliary claws in pusillum are distinctly longer and slenderer, the ventral tubercle in proximal half of femur is somewhat variable and not well suited to distinguish these species (compare Fig. 64; Hoenigman & Stock 1955: 534, Figs. 1, 2).   
 Pycnogonum cessaci is a species of shallow waters, its depth range in the research area was 0–10 m, in good agreement with data in the literature. In the Santa Marta region the preferred substratum was mostly algal stands and hydroids of the genus Cnidoscyphus. McCloskey (1967: 131) found ovigerous males from North Carolina (east coast of U.S.A.) in months IX–XII only.   
 Distribution: Mainly amphi-atlantic, in the tropics and subtropics (Stock 1990: 231). Child (1979: 72) lists 2 records from the Pacific coast of Panamá. Stock (1986: 405) gives a compilation of the regions colonized.
description: Published as part of 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, pp. 1-138 in Zootaxa 2319 (1) on pages 122-124, DOI: 10.11646/zootaxa.2319.1.1, http://zenodo.org/record/5317868