Crenoicus Nicholls 1944
Creators: name: Wilson, George D. F.
name: Ho, L. E.
Publisher: name: Zenodo
Year: 1996
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Phreatoicidae
Crenoicus

description: <i>Crenoicus</i> Nicholls, 1944 <i>Crenoicus</i> Nicholls, 1944: 21-23. Type species. <i>Crenoicus mixtus</i> Nicholls, 1944. Generic diagnosis. Eyes absent. Head length subequal to width in dorsal view, maxillipeds inserting near posterior margin of head. Dorsal surface with scattered fine setae, lacking tubercles or ridges. Pereonites lacking epimeral plates, all coxae visible in lateral view. Pereopodal coxae lacking distinct lateral projections. Gut with minimal typhlosole, "u" shaped in cross section. Pleonites with well-developed ventral epimera, pleopodal protopods not visible in lateral view. Pleotelson depth greater than length; posteriorly trilobed in dorsal or ventral view; medial tip not cleft, not distinctly longer than lateral lobes; ventral margin anterior to insertion of uropods with row of simple robust setae. Antennula terminal article shorter and narrower than subterminal articles, roughly globular. Right mandible lacking lacinia mobilis. Maxillula medial lobe narrower than lateral lobe, with 4 large plumose setae and 2 small simple setae (6 plumose setae sometimes occurring). Pereopod I male propodal palm with short, broadly conical, dorsally angled setae on low ridge; female propodal palm with row of broad based simple setae. Male pereopod IV subchelate between dactylus and propodus, propodal palm with proximal large broad based setae. Penes smooth, lacking setae, strongly curved posteriorly, tapering distally to rounded point. Pleopod I exopod distally pointed, widest at midlength; endopod without setae. Male pleopod 11 appendix masculina curved, distally stylet-like, distal tip spatulate or spine-like with long single subdistal seta. Uropodal protopod distoventral margin with 1 robust distally spinose seta; propodal medial margin lacking distal projection; rami distally pointed, spine-like. Remarks. Nicholls (1944) classified his genus <i>Crenoicus,</i> an exclusively Australian genus, in the subfamily Phreatoicinae which otherwise contains New Zealand forms. His subfamily concept may be too broad because the elongate subterranean genera <i>Phreatoicus</i> Chilton, 1883 and <i>Neophreatoicus</i> Nicholls, 1944 can be distinguished from the more typically shaped species of <i>Crenoicus</i> and <i>Notamphisopus</i> Nicholls, 1944. Nevertheless, Poore <i>et at.</i> (in press) expand the definition of the subfamily to include genera of Paraphreatoicinae Nicholls, 1944 plus <i>Uramphisopus</i> Nicholls, 1943, and raise this group to family level. We do not diagnose the family Phreatoicidae because the family level systematics of the Phreatoicidea should be reviseu using phylogenetic methods. With this new composition of the Phreatoicidae, more genera must be compared with <i>Crenoicus.</i> The New Zealand species of <i>Phreatoicus</i> and <i>Neophreatoicus</i> are much more elongate than other Phreatoicidae and have a pleotelson whose length is greater than its depth. <i>Crenoicus</i> can be distinguished from <i>Colacanthotelson</i> Nicholls, 1944, <i>Mesacanthotelson</i> Nicholls, 1944 and <i>Onchotelson</i> Nicholls, 1944 by the lack of any unusual alterations of the dorsal cuticle, the pleotelson tip or the coxae (i.e. the cuticle is not rugose, the pleotelson does not have an elongate tip and the coxae are not laterally expanded). The other phreatoicid genera <i>Uramphisopus</i> Nicholls, 1943, <i>Colubotelson</i> Nicholls, 1944, <i>Metaphreatoicus</i> Nicholls, 1944, <i>Paraphreatoicus</i> Nicholls, 1944 and <i>Notamphisopus</i> Nicholls, 1944 are more similar to <i>Crenoicus.</i> Unlike Knott (1975) and Poore <i>et al.</i> (in press), we are uncertain whether the genera <i>Metaphreatoicus, Colubotelson</i> and <i>Paraphreatoicus</i> should be synonymised into <i>Uramphisopus.</i> <i>Uramphisopus pearsoni</i> Nicholls, 1943 has a large medial extension of the uropodal protopod, while none of the species attributed to other three genera have this feature. Other characters, such as the setation of the pleopodal endopods and the uropods, also suggest more diversity than a single genus should contain. Consequently, we prefer to recognise these genera until the suborder is revised. All of these genera, however, lack a distally pointed appendix masculina seen in <i>Crenoicus</i> and instead have a typically rounded tip with multiple setae. These genera also differ in other details such as the setation of the first pleopod and the number of spinose setae on the distal margin of the uropodal protopod. While most Australian Phreatoicidae have eyes, <i>Crenoicus</i> species are completely blind, although the head may have a cuticular remnant of the eyes. <i>Crenoicus</i> species also have a subcuticular white patch of unknown function in the ocular region of the head. Species included. <i>Crenoicus mixtus</i> Nicholls, 1944; C. <i>shephardi</i> (Sayce, 1900); C. <i>harrisoni</i> Nicholls, 1944 and C. <i>buntiae</i> n.sp. Nicholls (1944: 31) noted another undescribed species from the New England region of New South Wales. The morphological conservatism of this genus coupled with substantial intrapopulation variation in some characters (discussed later in this paper) makes identification of species difficult. A complete species inventory for <i>Crenoicus,</i> therefore, will require careful morphometric and genetic studies. Distribution of <i>Crenoicus</i> species. Throughout springs and swamps of Victoria and New South Wales: near Ballarat (c. <i>mixtus),</i> Plenty Range near Melbourne Vic. (c. <i>shephardi),</i> Barrington Tops NSW (c. <i>harrisoni),</i> Boyd Plateau NSW (c. <i>buntiae</i> n.sp.), Otway Range Vic. <i>(Crenoicus</i> sp.-undescribed). Our collecting activities have shown other undescribed species of <i>Crenoicus</i> to be widespread in NSW springs and marshes above 1000 m (see Fig. 1).
description: Published as part of <i>Wilson, George D. F. &amp; Ho, L. E., 1996, Crenoicus Nicholls, 1944 (Crustacea, Isopoda, Phreactoicidea): Systematics and biology of a new species from New South Wales, pp. 7-32 in Records of the Australian Museum 48 (1)</i> on pages 9-10, DOI: 10.3853/j.0067-1975.48.1996.279, http://zenodo.org/record/4654870
description: {"references": ["Nicholls, G. E., 1944. The Phreatoicoidea. Part 11. The Phreatoicoidae. Papers and Proceedings of the Royal Society of Tasmania 1943: 1 - 156.", "Chilton, C., 1883. Further additions to our knowledge of the New Zealand Crustacea. Transactions of the New Zealand Institute 15: 69 - 86.", "Nicholls, G. E., 1943. The Phreatoicoidea. Part I. The Amphisopidae. Papers and Proceedings of the Royal Society of Tasmania 1942: 1 - 145.", "Knott, B., 1975. Systematic studies on the Phreatoicoidea (Order Isopoda) with a discussion on the phylogeny and zoogeography of other freshwater malacostracan crustaceans from Australia and Tasmania. Ph. D. Thesis. (unpublished, in 2 vols.). University of Tasmania, Hobart, pp. 344.", "Sayce, O. A., 1900. Phreatoicus shephardi-a new species of fresh-water Isopoda from Victoria. Proceedings of the Royal Society of Victoria, n. s. 13: 25 - 28 (pI. 3)."]}