identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
03CD87BD3D63FF80A4FFFB5ABB97FA6C.text	03CD87BD3D63FF80A4FFFB5ABB97FA6C.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon corbiculinum Palatov 2023	<div><p>Symbiocloeon corbiculinum Palatov 2023</p><p>(Figs 1–2)</p><p>Symbiocloeon sp. 1: Bespalaya, Sousa, Gofarov, Kondakov, Kropotin, Palatov, Vikhrev &amp; Bolotov 2022: 2.</p><p>Symbiocloeon corbiculinus Palatov (in Bespalaya, Palatov, Gofarov, Kondakov, Kropotin, Sousa, Taskinen, Inkhavilay, Tanmuangpak, Tumpeesuwan, Vikhrev &amp; Bolotov) 2023: 6 (larva). Ending of the species name should be changed to -um according to neutral gender of the generic name formed from « Cloëon ».</p><p>Material examined. Holotype and paratypes. Descriptions. Larva as described by Bespalaya et al. 2023. Winged stages and eggs unknown.</p></div>	https://treatment.plazi.org/id/03CD87BD3D63FF80A4FFFB5ABB97FA6C	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D63FF80A4FFFF4CBEBFFB96.text	03CD87BD3D63FF80A4FFFF4CBEBFFB96.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon Muller-Liebenau & Heard 1979	<div><p>Genus Symbiocloeon Müller-Liebenau 1979</p><p>(Figs 1–60, 65, 67–70)</p><p>Symbiocloeon Müller-Liebenau (in Müller-Liebenau &amp; Heard) 1979: 58 (larva).</p><p>Type species: Symbiocloeon heardi Müller-Liebenau (in Müller-Liebenau &amp; Heard) 1979 .</p><p>Larva. Able for inhabitancy in mantle cavities of freshwater bivalve mollusks.</p><p>Both mandibles with prostheca stick-like, with setae between prostheca and mola (Figs 1–4). Maxilla of « Cloeon - type » (sensu Kluge 2017: 94), i.e. with distal dentiseta bent in same direction as canines and two other dentisetae (Figs 5–6). Labial palp 2-segented, i.e. lacking boundary between initial 2nd and 3rd segments and lacking muscle going from 2nd segment to base of 3rd segment (Figs 7–9).</p><p>Legs lacking long setae; two-channel setae of longitudinal row on outer-dorsal side of femur either very short (Fig. 22), or absent; other setae not longer or absent. Femoral patch absent. Apex of femur with incision on anterior side, caused by the fact that anterior-outer projection is shortened and not reaching anterior-inner projection (Fig. 25). Claws lacking denticles on proximal part; either without denticles, or with two rows of denticles in distal part only (Figs 23, 24, 68).</p><p>Scales on surface of abdominal terga either absent, or with opercula-bearing sockets (i.e., each socket with two operculae) (Fig. 68). Caudalii with primary swimming setae, without secondary swimming setae.</p><p>Winged stages. Hind wings absent. Other characters of winged stages known for S. laoense only (see below).</p><p>Distribution and species composition. Includes 4 described species distributed in the Oriental Region: Symbiocloeon madhyasthai Subramanian &amp; Sivaramakrishnan 2009 (known from Southern India), S. heardi Müller-Liebenau (in Müller-Liebenau &amp; Heard) 1979 and S. corbiculinum Palatov (in Bespalaya et al.) 2023 (both known from Thailand) and S. laoense Palatov (in Bespalaya et al.) 2023 (known from Laos). Larvae of all these species develop in mantle cavities of freshwater clams (Malacozoa, Bivalvia). Among them, larvae of S. madhyasthai and S. heardi inhabit large clams belonging to the family Unionidae, and S. corbiculinum and S. laoense inhabit small clams Corbicula fluminea .</p></div>	https://treatment.plazi.org/id/03CD87BD3D63FF80A4FFFF4CBEBFFB96	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D63FF90A4FFF9C7BD15FE53.text	03CD87BD3D63FF90A4FFF9C7BD15FE53.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon laoense Palatov 2023	<div><p>Symbiocloeon laoense Palatov 2023</p><p>(Figs 3–60, 63–65)</p><p>Symbiocloeon sp. 2: Bespalaya, Sousa, Gofarov, Kondakov, Kropotin, Palatov, Vikhrev &amp; Bolotov 2022: 2.</p><p>Symbiocloeon laoensis Palatov (in Bespalaya, Palatov, Gofarov, Kondakov, Kropotin, Sousa, Taskinen, Inkhavilay, Tanmuangpak, Tumpeesuwan, Vikhrev &amp; Bolotov) 2023: 16 (larva). Ending of the species name should be changed to -e according to neutral gender of the generic name formed from « Cloëon ».</p><p>Material examined. LAOS, boundary of Champasak and Attapu provinces, river Xekhamphor upstream village <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=106.182495&amp;materialsCitation.latitude=14.771111" title="Search Plazi for locations around (long 106.182495/lat 14.771111)">Kenang-Ang</a> (22 km E from Thang Beng by road 18), 14°48′45″N and 14°46′16″N, 106°10′57″E, 30.II–4.II.2025, coll. N. Kluge &amp; L. Sheyko, extracted from Corbicula fluminea: 1 L-S-I ♂, 2 L-S ♀, 46 larvae; collected at light: 1 S-I ♂, 1 S-I ♀. Holotype and paratypes, the same locality, 3.III.2018, coll. I.N. Bolotov, I. V. Vikhrev, E.S. Konopleva &amp; Y.E. Chapurina .</p><p>Larva. CUTICULAR COLORATION. In early larval instars cuticle colorless (Figs 10, 12), in later instars pigmented dorsally, with maximum pigmentation in last instar (Figs 11, 13).</p><p>CUTICULAR COLORATION IN LAST LARVAL INSTAR (Figs 14–18). Frons between frontal sutures and median ocellus dark brown (Figs 13, 17). Pronotum and mesonotum with brown, ochre and colorless areas; fore protopteron with two lighter stripes and fine darker lines along all longitudinal and main intercalary veins (Figs 13, 18). Metanotum brown medially, colorless laterally (Fig. 16). Thoracic pleura with colorless and brown areas, sterna colorless (Fig. 16). Legs entirely colorless (Figs 16, 19–21). Abdominal terga II–IX mostly brown, with lighter paired medio-anterior and medio-posterior sigilla; tergum X colorless anteriorly and brown posteriorly (Fig. 14). Abdominal sterna mostly colorless, sterna of some posterior segments diffusively darkened by brown in median part (Fig. 15). Cerci and paracercus entirely colorless (Figs 10–14).</p><p>HYPODERMAL COLORATION. Not expressed.</p><p>SHAPE AND SETATION. Described by Bespalaya et al. (2023). Following details should be added:</p><p>Maxilla of « Cloeon - type », i.e. with distal (1st) dentiseta bent in same direction as canines and other dentisetae (Kluge 2017: 94). Among 3 maxillary canines, two canines small and slender; all 3 dentisetae slender, either pointed, or bifurcate, or trifurcate (Figs 5–6). Maxillary palp enlarged and banana-shaped, without any setation, with week muscle going to its base, without muscle inside (i.e. one-segmented).</p><p>Labium and labial palps without any setae other than setae on dorsal side of paraglossae. Paraglossa greatly widened, with field of densely and irregularly situated small setae on dorsal side of distal half. Labial palp with week muscles going to bases of 1st and 2nd segments, but probably immovable; connection between 1st and 2nd segments wide and immovable. 2nd segment directed medially and overlapping paraglossa from ventral side, with immovable dorso-distal projection (possibly, vestige of 3rd segment lacking muscle).</p><p>Legs with few small hair-like setae and few small two-channel setae [term introduced by Kluge et al. (2023)]; each femur with sparse longitudinal row of small, pointed, two-channel setae on anterior side near outer margin (Fig. 22); other two-channel setae smaller.</p><p>Claws with two symmetric rows of blunt denticles near apex (Figs 23–24).</p><p>Tergalii unable for rhythmic respiratory movements, able for slow movements only; in living larva usually directed laterally, in one flatness (Figs 10–13).</p><p>POSE OF SUBIMAGINAL GONOSTYLI DEVELOPING UNDER LARVAL CUTICLE. In male larva of last instar, protogonostyli prominent and cone-shaped. Developing subimaginal gonostyli folded by « Nigrobaetis - type »: all segments directed caudally, 2nd segment sharply bent with convexity directed medially, 3rd (apical) segment deeply inserted into 2nd segment (Figs 47, 50) .</p><p>Subimago. CUTICULAR COLORATION. Head very light or colorless. Pronotum brown, with darker and lighter areas. Mesonotum mostly brown, with anteronotal protuberance colorless (Fig. 26). Pleura mostly colorless, with postsubalar sclerite and lateropostnotal crest brown (Fig. 27). Sterna colorless. Legs colorless (Figs 30–35). Abdominal terga very light brownish; each segment with pair of darker sublateral spots bearing enlarged microtrichia (Figs 28–29); sterna, gonostyli and cerci colorless (Fig. 28).</p><p>TEXTURE. On all legs of both sexes, initial 1st–4th tarsomeres covered with blunt microlepides, initial 5th</p><p>(last) tarsomere covered with pointed microlepides (Fig. 35).</p><p>Imago, male (Figs 36–46, 48). Head brown with ochre. Turbinate eyes wide, dull red, with facetted surface darker than stem. Thorax with sclerites dark brown, equally dark on dorsal, ventral and lateral sides; membranous areas ochre. Fore wings colorless, veins ochre, costal vein proximad of costal brace darkened by brownish, costal brace colorless. Cross veins of pterostigma oblique, non-branched, complete and incomplete. 2 marginal intercalaries in each space. Hind wings absent. Legs light ochre; femur, base and apex of fore tibia slightly darkened by brownish (Figs 41–42). Tarsus of middle and hind legs relatively short, with 2 apical spines (on initial 2nd and 3rd tarsomeres) (as in Fig. 35). Abdominal terga brown, each with pair of lighter ochre stripes corresponding to medio-anterior and medio-posterior sigilla and median ochre stripe between them; sternum I brown, sterna II–VIII ochre (Fig. 40). Cerci uniformly light ochre.</p><p>Abdominal sternum IX, unistyligers, gonostyli, penial bridge and gonovectes brown (Fig. 43–46). More or less well outlined brown median styligeral sclerite locates between bases of unistyligers; median sterno-styligeral muscle distinctly developed, not wide, posteriorly attached to median sclerite only (Figs 43, 48). Unistyligers about as long as wide, cylindrical. 1st segment of gonostylus (thickest and fused with 2nd) slightly narrowing distally; 2nd segment (longest and arched) equally wide over its length; 3rd segment (terminal) long, equally wide over its length. Penial bridge with prominent, rounded, sclerotized median projection. Gonovectes sharply bent, movably attached, deeply inserted into abdominal segment IX, with free ends bearing gonoducts (as characteristic for Baetovectata).</p><p>Imago, female (Figs 51–54). Coloration of head, thorax, legs, abdomen and cerci as in male. Head short and wide, eyes small and widely separated. Fore leg (Fig. 53): tibia with patella-tibial suture (as on middle and hind legs); tarsus with 2 apical spines on 2nd and 3rd tarsomeres (as on middle and hind legs).</p><p>Egg (Figs 55–60). Asymmetric, generally irregularly-oval, with one side more or less stretched cone-like. Surface with evenly dispersed small round papillae and irregular folds forming concentric wavy circles around papillae. Micropyle wide, oval.</p><p>Dimension. Fore wing length (and approximated body length of imago) 6 mm; larval body length up to 8 mm.</p><p>Distribution. Known from one locality in Laos.</p><p>Collecting site and larval habitat. All larvae used in this study, were found in mantle cavities of Corbicula fluminea collected near the type locality of S. laoense —in the river Xekhamphor (or Sekhamphon), which serves as the boundary between provinces Champasak and Attapu. Name of this river is transliterated also as «Khampho»</p><p>(on Russian map printed in 1974) and «Sein Kaphoe» (in the original description of S. laoense). Picture of the type locality (Bespalaya et al. 2023: fig. 1C) was made from this river in the village Kenang-Ang (Fig. 61).</p><p>Collecting in the river Xekhamphor near the village Kenang-Ang (Fig. 61) gave little result: among 959 examined individuals of Corbicula fluminea, only 10 individuals contained 10 larvae of S. laoense . Much more density of S. laoense occurred upstream of this place, especially 3 km to the north, where a road from Ban Nakala reaches the river (Fig. 62).</p><p>Mantle cavities of Corbicula fluminea contained larvae of S. laoense of various instars, from rather young larvae (Fig. 12) to mature larvae ready to molt to subimago. Besides the mayfly S. laoense, some clams contained larvae or pupae of Chironomidae . Each clam contained no more than one insect―either mayfly larva, or chironomid larva or pupa. While larvae and pupae of Chironomidae were located between the mantle and the shell, larvae of S. laoense were located on the gills of clam (Figs 63–65). Clams are small (mostly about 10–15 mm length) and mayfly S. laoense is relatively large (6 mm length in adult stage), so that mature larva occupies significant part of mantle cavity and can be longer than body of the clam (Fig. 65). Most mayfly larvae sited on the clam body immovably, being covered with mucus (Fig. 65), but some were clean and were able to move by the clam body (Figs 63–64).</p><p>Being taken out from the clam and moved into a net cage placed in running water, larvae were able to sit on the net surface of the cage and swim when necessary. Before molt to subimago, larva floats on the water surface in the same manner as other mayflies. It remains to be unclear, how larva ready to molt to subimago escapes from the clam.</p><p>Among 9 mature larvae placed into the cage, only one male and two females were able to shed the larval cuticle; among them, one male successfully molted from larva to subimago and from subimago to imago (Fig. 36), but died just after this molt, so its cuticle of gonostyli did not harden and crumpled (Fig. 46). Both emerged female subimagines died not spreading their wings. The description of winged male and female imagines given here, is completed by examination of two specimens reared from subimagines, which were attracted to on ultraviolet lamp placed close to the river (Figs 39, 50–51).</p></div>	https://treatment.plazi.org/id/03CD87BD3D63FF90A4FFF9C7BD15FE53	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D73FF90A4FFFD9DBCA3FCF1.text	03CD87BD3D73FF90A4FFFD9DBCA3FCF1.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon undefined-1	<div><p>Symbiocloeon sp. 1</p><p>(Fig. 70)</p><p>Specimens reported as «the larvae of an undescribed species of Symbiocloeon from Myanmar »: Bespalaya et al. 2023: 19.</p><p>Material examined: MYANMAR, Kachin State, Man Say Khun District, river Nam Shu (left tributary of river Irrawaddy) near village Lipu, 27°32′51.0″N, 97°22′13.8″E, 14.III.2014, coll. I.N. Bolotov, I. V. Vikhrev &amp; A. V. Kondakov, extracted from Yaukthwa cf. dalliana (Frierson 1913): 3 larvae .</p></div>	https://treatment.plazi.org/id/03CD87BD3D73FF90A4FFFD9DBCA3FCF1	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D73FF90A4FFFC72BCC6FB1C.text	03CD87BD3D73FF90A4FFFC72BCC6FB1C.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon undefined-2	<div><p>Symbiocloeon sp. 2</p><p>(Figs 67–69)</p><p>Symbiocloeon sp. 2: Tomilova et al. 2021, AVK-2021c, GenBank NCBI, taxonomy ID 2905744 (non Bespalaya et al. 2022).</p><p>Material examined: RUSSIA, Far East, Primorsky Krai, Khankaysky District, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=132.0803&amp;materialsCitation.latitude=44.580414" title="Search Plazi for locations around (long 132.0803/lat 44.580414)">river Melgunovka</a>, 12 km upstream from mouth at <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=132.0803&amp;materialsCitation.latitude=44.580414" title="Search Plazi for locations around (long 132.0803/lat 44.580414)">Lake Khanka</a>, 44°34′49.5″N, 132°04′49.1″E, 01.VII.2018, coll. I.N. Bolotov, I. V. Vikhrev &amp; A. V. Kondakov, extracted from Nodularia douglasiae (Gray 1833): 5 larvae .</p></div>	https://treatment.plazi.org/id/03CD87BD3D73FF90A4FFFC72BCC6FB1C	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D74FF97A4FFFEC7BC2EFBE9.text	03CD87BD3D74FF97A4FFFEC7BC2EFBE9.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon Muller-Liebenau & Heard 1979	<div><p>Position of Symbiocloeon within Baetovectata</p><p>Does Symbiocloeon belong to Baetungulata? The taxon Baetungulata Kluge &amp; Novikova 2011 comprises overwhelming majority of Baetovectata; it is characterized by asymmetric larval claw bearing a single row of denticles on its inner side, which represents the inner-anterior row among two initial rows; the second (inner-posterior) row is either absent (in overwhelming majority of Baetungulata), or consists of denticles much smaller than denticles of the inner-anterior row.Among Baetungulata, in Nigrobaetis (Takobia) maxillaris (Braasch &amp; Soldán 1983) denticles on claw are completely lost. In taxa other than Baetungulata, either two inner rows of denticles (the inner-anterior and the inner-posterior ones) are equally developed, or both rows are equally reduced or lost.</p><p>In all species of Symbiocloeon, claws do not have the single row of denticles characteristic for Baetungulata. Claws of S. heardi and S. madhyasthai lack any denticles, and claws of S. corbiculinum and S. laoense have two symmetric rows of peculiar denticles near the claw apex (Figs 23–24), which are probably not homologous to more proximal denticles of other Baetidae . The modified claw structure of Symbiocloeon does not allow us to determine if they originated from the claws characteristic for Baetungulata, or not.</p><p>Baetovectata other than Baetungulata. Among Baetovectata not belonging to Baetungulata (which can be indicated as Baetovectata-non-Baetungulata), the Old World fauna contains only the genus Centroptella Braasch &amp; Soldán 1980 (including subgenera Centroptella, Crassolus Salles et al. 2016 and Chopralla Waltz &amp; McCafferty 1987) (Kluge 2021). Symbiocloeon clearly differs from Centroptella by non-modified patella-tibial suture on larval legs, so it could not originate from Centroptella . All other representatives of Baetovectata-non-Baetungulata are found in New World only and probably have Neotropical origin, while all species of Symbiocloeon are known from the Old World.</p><p>We proceed from the assumption that Symbiocloeon belongs to Baetungulata and have lost the primary denticles on claw, similar to Nigrobaetis (Takobia) maxillaris .</p></div>	https://treatment.plazi.org/id/03CD87BD3D74FF97A4FFFEC7BC2EFBE9	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
03CD87BD3D74FF95A4FFFB7BBD65F884.text	03CD87BD3D74FF95A4FFFB7BBD65F884.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symbiocloeon Muller-Liebenau & Heard 1979	<div><p>Position of Symbiocloeon within Baetungulata</p><p>Difference between Symbiocloeon and Baetofemorata. The taxon Baetofemorata Kluge &amp; Novikova 2011 comprises most part of Baetungulata; it has the following characters: (1) Femoral patch is always present (the same in some Labiobaetini). (2) Inner margin of both mandibles between prostheca and mola always lacks setae. (3) If larval abdominal terga and other body parts bear wide scales, sockets of these scales are semicircular, lacking side operculae. (4) On all legs of subimago each tarsal segment is covered mainly by blunt microlepides; only in distal parts of segments pointed microlepides can be present (Kluge 2022). (5) In mature larva ready to molt to subimago, developing subimaginal gonostyli are folded under larval cuticle either by the « Baetis - type », or the « Acentrellatype » (see above); in these cases both 2nd and 3rd segments of gonostylus are directed medially.</p><p>No one of these characters occurs in Symbiocloeon: (1) In all known species of Symbiocloeon femoral patch is absent. (2) Both mandibles bear setae between prostheca and mola (Figs 1–4). (3) In that species of Symbiocloeon, which abdominal terga retain scales, sockets of these scales have well-developed side operculae (Fig. 68). In S. corbiculinum and S. laoense these scales and their sockets are completely lost. (4) In the single species with known subimago ( S. laoense), the last tarsomere is entirely covered with pointed microlepides (Fig. 35). (5) In the single species, which development of subimaginal gonostyli is known ( S. laoense), the gonostyli are folded by the « Nigrobaetis - type », i.e. with apices of 2nd segments directed laterally (Figs 47, 50).</p><p>Difference between Symbiocloeon and Labiobaetini . The large tribe Labiobaetini Kluge &amp; Novikova 2016 belongs to Baetungulata and has the following characters: (1) In male imago sterno-styligeral muscle is completely lost. (2) In mature larva ready to molt to subimago, developing subimaginal gonostyli are folded under larval cuticle either by the « Labiobaetis - type », or the « Acentrella- type » (see above); in these cases both 2nd and 3rd segments of gonostylus are directed medially.</p><p>No one of these characters occurs in Symbiocloeon: (1) In the single species with known male imago ( S. laoense), the sterno-styligeral muscle is retained (Fig. 43). (2) In the single species, which development of subimaginal gonostyli is known ( S. laoense), the gonostyli are folded by the « Nigrobaetis - type », i.e. with apices of 2nd segments directed laterally (Fig. 47, 50).</p><p>Difference between Symbiocloeon and Indobaetis . The small Oriental genus Indobaetis Müller-Liebenau &amp; Morihara 1982 has the following characters (Kluge &amp; Novikova 2014): (1) On fore leg of female subimago and imago 1st tarsomere is completely fused with 2nd tarsomere, so the tarsus is 4-segmented, like tarsi of middle and hind legs. (2) In mature larva ready to molt to subimago, developing subimaginal gonostyli are folded under larval cuticle by the « Labiobaetis - type », with 2nd and 3rd segments of gonostylus directed medially.</p><p>No one of these characters occurs in Symbiocloeon: (1) In the single species, which female subimago and imago are known ( S. laoense), tarsus of fore leg is 5-segmented (Figs 32, 53), as on fore leg of male (Fig. 30), and in contrast to middle and hind legs (Fig. 34). (2) In the single species, which development of subimaginal gonostyli is known ( S. laoense), the gonostyli are folded by the « Nigrobaetis - type », i.e. with apices of 2nd segments directed laterally (Figs 47–50).</p><p>Comparison of Symbiocloeon and Nigrobaetis . The Arctogean genus Nigrobaetis Kazlauskas (in Novikova &amp; Kluge) 1987 is distributed in Holarctic, Oriental and Afrotropical Regions. Its larvae differ from most other Baetidae and most other mayflies by characteristic shape of head, with antennae bases brought together and the frons forming elevated longitudinal carina between them (Kluge &amp; Novikova 1987: figs 1. 14, 1. 16). The same feature is found in Indobaetis and some Neotropical taxa.</p><p>Larvae of Symbiocloeon do not have this character: their frons is not carinate, and antennal bases are widely separated (Bespalaya et al. 2023: figs 6B, 12A). Other characters of Symbiocloeon are either in agreement with that of Nigrobaetis, or represent apomorphies which can be derived from the structures belonging to Nigrobaetis . Possibly, shape of larval head was secondarily changed in Symbiocloeon, in connection with general flattening of the body adopted for inhabitance in mantle cavity of mollusks.</p><p>The genus Nigrobaetis is divided into subgenera Nigrobaetis s.str., Takobia Novikova &amp; Kluge 1987 (= Alainites Waltz &amp; McCafferty (in Waltz, McCafferty &amp; Thomas) 1994 and Margobaetis Kang &amp; Yang (in Kang, Chang &amp; Yang) 1994 (see below).</p><p>Comparison of Symbiocloeon and Margobaetis . The subgenus Margobaetis is distributed mostly in the Oriental and Afrotropical Regions with a few species in southern Palaearctic; it is characterized by a peculiar structure of eggs, which have one side stretched cone-shapely (Figs 73–74) (Kluge et al. 2024). The same egg structure occurs in the single examined species of Symbiocloeon, S. laoense (Figs 55–60; 71–72).</p><p>Comparison with Nigrobaetis (Margobaetis) minutus . The Oriental species Nigrobaetis (Margobaetis) minutus (Müller-Liebenau 1984), has special similarity with Symbiocloeon laoense in egg structure (Figs 71–74; compare also Figs 55–60 with Kluge et al. 2024: figs 39–43).</p><p>These two species have also similarity in structure of male imaginal genitalia (compare Figs 43–46 with Kluge et al. 2024: figs 35–37). This similarity is caused by similar shape of the gonovectes, similar shape of the gonostyli with elongate terminal segment, similar median sclerotized projection of the penial bridge, and similar median styligeral sclerite located between the unistyligers. Among these features, the sharp bent of gonovectes is characteristic for Baetovectata, and their shape is usual among Baetovectata; the elongate distal segments of gonostyli is usual for Nigrobaetis and some other taxa; the median projection of penial bridge and the presence of median styligeral sclerite are species-specific characters. Similar median projection of penial bridge is well known as a species-specific character of some non-related baetid species belonging to various genera.</p><p>The median styligeral sclerite is less known. One of autapomorphies of Baetidae is reduction of median part of male imaginal styliger, so that the styliger is transformed into a pair of unistyligers with incision between them; the unpaired median sterno-styligeral muscle is terminated on integument of this incision (Kluge &amp; Novikova 2011: p. 5, fig. 3). In some baetids, the incision between unistyligers bears a distinctly outlined, sclerotized and pigmented median styligeral sclerite, on which the unpaired median sterno-styligeral muscle is terminated. This sclerite is present in various representatives of the plesiomorphon Protopatellata (Kluge 2018: fig. 46, 49, 51) and in a few Anteropatellata.Among Anteropatellata, the median styligeral sclerite is present in Cheleocloeon truncifolium Kluge 2016 (Kluge 2016a: fig. 110), but absent in other species of the genus Cheleocloeon; it is present in Centroptella ornatipes Kluge 2021 (Kluge 2021: figs 149–150), but absent in other species of the genus Centroptella; it is present in Nigrobaetis (Margobaetis) minutus (Müller-Liebenau 1984) (Kluge et al. 2024: figs 35, 37), but absent in other species of the genus Nigrobaetis . The median styligeral sclerite is present also in Symbiocloeon laoense (Figs 43, 48).</p><p>All features of larvae and imagines other than the egg structure and the structure of male imaginal genitalia, are quite different in Nigrobaetis (Margobaetis) minutus (see Kluge et al. 2024) and Symbiocloeon laoense (see above and Bespalaya et al. 2023).</p></div>	https://treatment.plazi.org/id/03CD87BD3D74FF95A4FFFB7BBD65F884	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Kluge, Nikita J.;Vishnevskaya, Maria S.;Palatov, Dmitry M.	Kluge, Nikita J., Vishnevskaya, Maria S., Palatov, Dmitry M. (2025): Winged stages of Symbiocloeon laoense Palatov 2023 (Ephemeroptera: Baetidae) and systematic position of larvae developing inside mantle cavities of bivalve mollusks. Zootaxa 5728 (2): 287-320, DOI: 10.11646/zootaxa.5728.2.3, URL: https://doi.org/10.11646/zootaxa.5728.2.3
