Stockmyzon crassus (Stock, 1966) Bandera & Huys, 2008
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2008.00375.x |
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persistent identifier |
https://treatment.plazi.org/id/8D5F87C6-5F4E-0C45-0D27-FDE0C09A724E |
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treatment provided by |
Felipe |
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scientific name |
Stockmyzon crassus |
| status |
sp. nov. |
STOCKMYZON CRASSUS SP. NOV.
Synonym: Asterocheres mucronipes Stock, 1960 sensu Stock (1966) .
Original description: Stock (1966: 146–147, fig. 1a–c).
Type locality: Mauritius, Chenal du Trou d’Eau Douce; associated with “small flabby orange sponges”, without skeleton ( Oscarella sp. ), in small “grottos” in the reef at 6–10 m depth’ .
Material examined: Holotype female and 16 paratype females (originally identified as A. mucronipes ) ( ZMA Co. 100.955) from type locality; collected by J.H. Stock, 7 February 1964.
Description: Restricted to differences with the type species.
Female: Body ( Fig. 7A View Figure 7 ): cyclopiform, consisting of dorsoventrally flattened prosome and cylindrical urosome. Total length measured from rostral margin to posterior margin of caudal rami, 652 Mm [564–664, N = 6 according to Stock (1966)]; maximum width, 440 Mm measured at 4/5 length of cephalothorax. Ratio of length to width of prosome: 1.08: 1. Ratio of length of prosome to that of urosome: 2.5: 1. Genital double somite and free abdominal somites: covered with large epicuticular scales arranged in an overlapping pattern ( Fig. 8E View Figure 8 ); scales larger than in S. mucronipes . Somite bearing leg 5 ( Fig. 7B View Figure 7 ): wider than long, with some spinules around bases of outer basal setae. Genital double somite ( Fig. 7B–C View Figure 7 ): narrower and less laterally produced than in S. mucronipes , about 1.2 times wider than long; with lateral postgenital setular tufts.
Caudal rami ( Figs 7B–C View Figure 7 , 8E View Figure 8 ): slightly longer than wide (measured along outer margin), ornamented with epicuticular scales all over. Caudal setae IV–V: distinctly swollen in proximal half.
Antennule ( Fig. 7D View Figure 7 ): 20-segmented, about 312-Mm long; segmental fusion pattern as in S. mucronipes . Segments 1–8, each with two setae; segment 9, with six setae and a small spine; segment 10, with two setae; segment 11, with one seta and one small spine; segments 12–17, each with two setae; segment 18, with two setae plus an aesthetasc; segment 19, with three setae; segment 20, with nine setae. Segment 10(XIII), reduced, forming incomplete sclerite partly overlapped by distal expansion of compound segment 9(IX–XII). All setae smooth.
Antenna ( Fig. 7E View Figure 7 ): biramous, 186-Mm long. Coxa and basis: without spinule rows. Exopod: as in S. mucronipes . Endopod: three-segmented; proximal segment with spinular ornamentation as illustrated; middle segment with one smooth seta; distal segment with one naked seta and one distal claw, and with few spinules along margin and long setules on anterior surface.
Siphon ( Fig. 8A View Figure 8 ): long and slender, reaching to intercoxal sclerite of leg 1.
Mandible ( Fig. 9A View Figure 9 ): comprising stylet-like gnathobase and slender two-segmented palp. Proximal segment of palp unarmed; distal segment with two plumose, unequally long, apical setae. Stylet: as in S. mucronipes .
Maxillule ( Figs 8C View Figure 8 , 9B View Figure 9 ): bilobed. Praecoxal gnathobase four times longer than palp; ornamented with a row of long spinules distally, and a row of shorter spinules laterally; armed with five distal setae (one of them smooth and short). Palp strongly reduced; with one elongate, strongly plumose seta, and two short pinnate setae.
Maxilla ( Figs 8B View Figure 8 , 9C View Figure 9 ): essentially as in S. mucronipes , but coxal part of syncoxa without surface spinule row. Vestigial element on claw-like basis: not discernible.
Maxilliped ( Fig. 9D View Figure 9 ): as in S. mucronipes , but basis and endopod relatively more slender; endopod segments 1–2 separated by suture on anterior side only.
Swimming legs 1–4 ( Figs 8D View Figure 8 , 10A–D View Figure 10 ): intercoxal sclerite present in legs 1–4, ornamented with patches of spinules in legs 1–3. Spine and seta formula: as for S. mucronipes . Coxae ornamented with spinule rows laterally, as illustrated. Middle and distal endopodal segments in legs 1–4: with a beak-shaped spiniform process distally (e.g. Fig. 8D View Figure 8 ). Leg 1 differs from that of S. mucronipes in the following characteristics: outer basal seta shorter; inner coxal seta pinnate instead of bare; proximal outer spinous process on middle endopod segment shorter; outer seta of distal endopod segment extending just beyond distal spinous process. Legs-2–3 inner coxal seta and outer basal seta: much shorter than in S. mucronipes . Proximal inner seta of middle endopod segment of leg 4: much longer than in S. mucronipes and approaching the length of the distal inner seta.
Fifth leg ( Fig. 7B View Figure 7 ): as in S. mucronipes except for lateral exopodal seta being distinctly shorter. Sixth legs ( Fig. 7B View Figure 7 ): represented by paired opercular plates closing off gonopores on genital double somite; armed with one short, smooth seta, and one spiniform element.
Male: Unknown.
Etymology: The specific name is derived from the Latin crassus , meaning thick, and refers to the swollen caudal setae.
Remarks
Stock’s (1966) redescription of A. mucronipes from Mauritian sponges is concise and limited to illustrations of the urosome, leg 4, and the maxillule. Stock confirmed several similarities with the Mediterranean type population, such as the annulated struc- ture of the mandibular stylet and the presence of beak-shaped processes on the swimming legs; however, he also claimed that the maxillule differed slightly in the shape of the ‘outer ramus’ or palp, being gonflate basally, and distinctly narrower distally ( Stock (1966: fig. 1b). This could not be confirmed in the Mauritian material or in the types of S. mucronipes (Stock doubted his original observation) ( Figs 2D View Figure 2 , 9B View Figure 9 ); instead, our re-examination revealed that Stock (1966) had overlooked a seta on both the maxillulary endite and palp. His illustration of leg 4 also shows minor discrepancies with our Figure 10D View Figure 10 , such as proportional length differences in the outer seta of the proximal exopodal segment and the inner proximal seta of the middle endopodal segment, and the apparent slenderness of the outer
| ZMA |
Universiteit van Amsterdam, Zoologisch Museum |
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