Biodiversity of Nearctic inland water: discovery of the genus Heterorotula (Porifera, Spongillida, Spongillidae) in the Appalachian Mountains, with biogeographical implications and description of new species

Renata Manconi; John Copeland; Stan Kunigelis; Roberto Pronzato

doi:10.3897/zookeys.1110.79615

Abstract

This paper reports the discovery of a small population of sponges in the Pigeon River of eastern Tennessee, USA, which were morphologically distinct from Spongillida of North America. A morphological comparative analysis resulted in the first Nearctic record of the genus Heterorotula with the description of a new species Heterorotula lucasi sp. nov. diverging from all other known species by its unique combinations of diagnostic morphotraits of spicules and gemmules. The new record enlarges the geographic range of the genus which has been known until now only from Australia, New Zealand, New Caledonia, Japan (as an alien species), and from subequatorial Brazil (as subfossil remains). The discovery of a biogeographic enclave of Heterorotula in the southeastern United States contributes to the understanding of Porifera inland water biodiversity, biogeographic patterns, and adaptive morphotraits in the Nearctic and globally. Data confirm that the Appalachian region (Ordovician–Permian origin) of Tennessee and, in general, of North America have high levels of diversity and endemicity.

Keywords

Aquatic biodiversity, biogeography, evolutionary history, freshwater sponges, morphotraits, Tennessee, United States

Introduction

The aquatic biodiversity of the southeastern United States is recognized as the most biologically rich on the North American continent (Elkins et al. 2019). Assessments of aquatic biodiversity have found the southeastern United States to have levels of diversity and endemism rivalling those of tropical regions (Abell 2000; Collen et al. 2014).

The mountains and valleys of the Appalachian region of North America extend for 3,200 km from the Canadian province of Newfoundland to central Alabama of the United States. There was no one-time orogeny creating the Appalachian Mountains; instead, these mountains were formed by several major and minor orogenies. Erosion has reduced ancient Appalachian peaks of over 5,000 m to slightly over 2,000 m today (Pickering et al. 2003).

The central and southern Appalachians did not experience Pleistocene glaciation. Their alignment north to south provided organisms a migration corridor to the south thereby avoiding extinctions (Pickering et al. 2003). Due to topography, climate, and being spared Pleistocene glaciation, the southern Appalachian Mountains are one of the most biologically diverse regions in the temperate world. High aquatic species diversity has led to this region being recognized as a global center of aquatic biodiversity (McLarney 1999; Curtin et al. 2002).

Until recently, little was known concerning the sponge fauna of the Appalachian region of Tennessee. However, including the species described in this article, 13 species have been documented from this region (Table 1) (Copeland et al. 2015, 2019, 2020). During July 2013 in the Pigeon River, a small population of sponges was discovered which was morphologically distinct from all other known extant Spongillida of North America. We report here on this population as the first record of the genus Heterorotula Penney & Racek, 1968 from the Nearctic Region and describe it as a new species.

Table 1.

Download as

CSV

XLSX

Checklist of the freshwater sponges (Porifera: Spongillida) of the Appalachian region of Tennessee (southeastern Nearctic Region) with the new species record (bold) from Pigeon River.

Family	Species
Potamolepidae	Cherokeesia armata Copeland, Pronzato & Manconi, 2015
Spongillidae	Corvospongilla becki Poirrier, 1978
	Ephydatia fluviatilis (Linnaeus, 1759)
	Ephydatia muelleri (Lieberkuhn, 1855)
	Eunapius fragilis (Leidy, 1851)
	Heteromeyenia latitenta (Potts, 1881)
	Heteromeyenia tubisperma ((Potts, 1881)
	Heterorotula lucasi sp. nov.
	Racekiela ryderi (Potts, 1882)
	Radiospongilla cerebellata (Bowerbank, 1863)
	Radiospongilla crateriformis (Potts, 1882)
	Radiospongilla crateriformis (Potts, 1882)
	Trochospongilla horrida (Weltner, 1893)

Study area

The Pigeon River arises in the Blue Ridge Mountains of western North Carolina and flows to the northwest until its confluence with the French Broad River in eastern Tennessee (Fig. 1A, B). The Pigeon and French Broad rivers are eastern head water tributaries of the Tennessee River. The Pigeon River traverses the Pisgah National Forest, the Cherokee National Forest, and drains much of the northeastern Great Smoky Mountains National Park. From Canton, North Carolina to its confluence with the French Broad River in Tennessee, anthropogenic impacts to the river have been substantial. The Pigeon River was once considered one of the most polluted rivers in North America (Etnier and Starnes 1993). In 1908 a paper mill began production in Canton, upstream of the Tennessee study area. Effluent from this mill contained a mixture of chemicals including dioxin, chloroform, organic halides, phenols, and catechols (Bartlett 1995). The toxicity of this mixture caused a significant loss of biodiversity. All gastropods (10 species), mussels (40 species), and many fish species disappeared from the river (Coombs 2010). Releases of high levels of tannins and lignin resulted in the river water becoming coffee brown in color and emitting a bad odor. Hot water releases from the mill raised water temperature.

Figure 1.

Study area A1 Tennessee in the southeastern region of the United States A2 location of Cocke County in Tennessee A3 type locality of Heterorotula lucasi sp. nov. is indicated by a black circle in the Pigeon River (35.9396, −83.1786) B riparian habitat of the new sponge species at the type locality C macrophotograph in vivo of holotype (USNM 1662182) with tawny color and encrusting growth form on a rocky substrate D macrophotograph of holotype in alcohol.

For 52 years there was no treatment of the mill’s effluent. The first effort at treatment occurred in 1960 with the removal of settleable solids (University of Tennessee 2021). In 1989 the mill began an effective dioxin control program. Dioxin has not been detected in tested water since 1989 (Coombs et al. 2010). In 1996 aquatic snails were re-introduced. The survival and recolonization of these snails led to the formation of the Pigeon River Recovery Project (PRRP) in 2001 (Coombs et al. 2010). The PRRP which is composed of volunteers from federal and state agencies, industry, and private organizations has the goal of increasing the aquatic biodiversity of the Pigeon River (Coombs 2010). Due to the reintroduction of aquatic organisms by the PRRP the Pigeon River has regained some of its biodiversity

Materials and methods

Two sites on the Pigeon River were surveyed by viewing appropriate hard substrates (i.e., rocks and logs) while wading. A total of 71 sponge specimens were collected, four of which were morphologically distinct from all other extant Spongillida of the Nearctic Region. A minimum of 1 human-hour of search time was spent at each collection site. Latitude and longitude were obtained using a Garmin GPSmap 76CSx receiver. Sponges were viewed using a 10× head-band magnifier for the presence of gemmules. If gemmules were found a section of the sponge was collected. Sponges were preserved in 70% ethanol until processed for light microscopy (LM) and scanning electron microscopy (SEM).

To characterize morphotraits and obtain clean spicule preparations for SEM observation and LM slides, excised sponge was dissolved in test tubes containing 65% nitric acid. Once dissolved, the remaining spicules were centrifuged to create a pellet. Pellets were rinsed and centrifuged three times in distilled water, followed by a final rinse and spin in 70% ethanol. Spicules were pipetted on to glass slides for LM analysis and onto stubs for SEM analysis. A glass substratum was placed under the spicules providing a black background in the SEM photomicrographs (Manconi and Pronzato 2000). Skeleton sections, disassociated spicules, entire gemmules, and gemmule cross-sections were sputter coated with gold-palladium using an Anatech Hummer IV (6.2) sputter coater and observed by Leo 982 and Hitachi TM 3000 SEM. Sponge identification was made using the keys of Manconi and Pronzato (2002, 2016) and descriptions of Reiswig et al. (2010), Penney and Racek (1968), and Racek (1969). To determine range, mean ± standard deviation for spicular lengths, widths, and rotule diameters 75 megascleres and gemmuloscleres were measured using the measurement program of the Hitachi TM 3000. Diameters of 10 gemmules were measured. A paired t-test analysis, using JMP software, was used to test the null hypothesis of no significant difference between diameters of gemmulosclere rotules.

Institutional acronyms

FW-POR R. Manconi and R. Pronzato collection, Italy.

USNM National Museum of Natural History, Smithsonian Institution, Washington DC, USA.

WAM Western Australian Museum, Perth, Western Australia.

Systematic account

Phylum Porifera Grant, 1836

Class Demospongiae Sollas, 1885

Subclass Heteroscleromorpha Cárdenas, Perez & Boury-Esnault, 2012

Order Spongillida Manconi & Pronzato, 2002

Family Spongillidae Gray, 1867

Genus Heterorotula Penney & Racek, 1968

Type species

Heterorotula capewelli (Bowerbank, 1863).

Heterorotula lucasi Manconi & Copeland, sp. nov.

https://zoobank.org/5886FA19-94E5-43D8-8EF6-AB41E0D819F3

Figs 1, 2, 3, 4, 5, 6, 7, 8, 9; Tables 1, 2

Type locality

Pigeon River 35.9396; −83.1786, Cocke County, Tennessee, USA.

Type data

Holotype. USNM 1662182, entire specimen, 70% ethanol, coll. J. Copeland, 30 July 2013. Paratype. USNM 1662183, fragments, 70% ethanol. Pigeon River, Cocke County, Tennessee, USA, 35.9396; −83.1786, coll. J. Copeland, 30 July 2013.

Other material

BMNH 1890.1.9.339, holotype, Heterorotula capewelli type species of genus Heterorotula. WAM Z27997, FW-POR 881, Heterorotula multiformis (Weltner, 1910) (Australia), WAM Z98316, FWPOR 883, Heterorotula cf. multidentata (Weltner, 1895) (Australia).

Diagnosis

Heterorotula lucasi sp. nov. is characterized by (a) gemmuloscleres as spiny birotules with flat rotules (distal and proximal) of significantly different diameters with crenulated/notched to shallowly incised margins, (b) absence of skeletal microscleres, (c) skeletal acanthoxeas spiny, and (d) free (not sessile) gemmules.

Etymology

The specific epithet lucasi refers to lux meaning light in Latin and is dedicated to Lucas Edward Copeland whose enthusiasm and love for the natural history of the forests and streams of the Appalachian Mountains of Tennessee resulted in many wonderful discoveries.

Description

Adult sponges with gemmules. No brooded larvae were found. Growth form (Fig. 1C) encrusting 1–4 mm in thickness and to 16 cm in diameter. Surface with irregular ridges, hispid from emerging spicules, and with a network of subdermal canals covered by a hyaline dermal membrane. Color tawny in vivo (Fig. 1C), light yellow to light brown in alcohol (Fig. 1D). Consistency of live sponge soft and fragile. Spongin scanty in skeletal network, arranged as irregular polygonal meshes, to abundant in gemmular theca and basal spongin plate. Ectosomal skeleton of slender megascleres in paucispicular fibres, with no special architecture (Fig. 2B) supports the dermal membrane. Choanosomal skeleton (Fig. 2A) as a network of multi-spicular fibres, with scanty spongin. Basal spongin plate well developed.

Megascleres (Figs 2, 3) fusiform acanthoxeas 223.1–335.0 μm (276.8 ± 24.7) in length and 7.7–13.7 μm (10.9 ± 1.0) in width, slightly curved, with variably dense spines except towards the variably pointed tips, to less frequently nearly spineless. Acanthoxeas shaft from slender in ectosomal area to stouter in the endosome. Microscleres absent.

Figure 2.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Micrographs of skeletal network with scanty spongin by SEM A multispicular fibres of entosomal area B paucispicular fibers of ectosomal area. Scale bar: 500 μm.

Figure 3.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Micrographs of skeletal megascleres by SEM A acanthoxeas fusiform from nearly spineless to variably spined excepts towards the tips B detail of an oxea smooth only at the tip C spiny shaft of an acanthoxea; scattered spines and microspines on shaft. Scale bars: 100 μm (A); 20 μm (B); 10 μm (C).

Gemmules (Fig. 4) scattered in skeletal network, subspherical, 448–613 μm (528 ± 55.9) in diameter. Foramen simple (Fig. 4E, F) with smooth undulate margins, slightly elevated above gemmule surface. Gemmular cage (Fig. 4C, D) of acanthoxeas with small spines.

Figure 4.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Micrographs of gemmules by SEM A gemmule with multilayered theca armed by radial gemmuloscleres around the central cavity bearing a mass of totipotent cells B outer layer at theca surface with a few emerging rotules of gemmuloscleres, acanthoxeas of the cage and sligtly elevated foramen closed by a membrane C theca of an aged gemmule covered by diatoms frustules, surrounded by the spicular cage of acanthoxeas and outer layer with open foramen after hatching D theca with a fragment of spicular cage and outer layer armed by dense distal rotules of gemmuloscleres E fibrous structure of outer layer with sligtly elevated foramen closed by a membrane before hatching F fibrous structure of outer layer around foramen and sparse broken shafts of gemmuloscleres. Scale bars: 500 μm (C, D); 300 μm (A, B); 100 μm (E); 20 μm (F).

Gemmular theca trilayered ~50 μm in thickness (Fig. 5). Outer layer fibrous to compact with distal rotules more or less embedded (Fig. 5A, B, D). Pneumatic layer well developed and thick, ranging in the same gemmule from mainly fibrous to chambered network of irregularly polygonal meshes of variable size (Fig. 5B, C). Inner layer (Fig. 5A, D) multilayered of 3–5 layers of compact spongin. Gemmuloscleres radially embedded (Fig. 5A, B) as a dense monolayer in pneumatic layers of theca, with distal smaller rotules partly covered by outer layer and proximal larger rotules, partly overlapping one to each other, not embedded into inner layer (Fig. 5A, B).

Figure 5.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Micrographs of gemmular theca cross sections by SEM A theca with the radial monolayer of short and long spiny birotules bearing crenulated/notched margins of rotules. proximal, partly overlapping, rotules adherent to the multilayered inner layer (cross section, outer layer, and pneumatic layer not evident) B trilayered theca with short and long spiny birotules embedded in the fibrous/chambered pneumatic layer in between the smooth outer layer and the multilayered inner layer, C radial birotules in the fibrous to chambered pneumatic layer D proximal rotule with crenulated/notched margins adherent to the multilayered inner layer surrounding the central gemmular cavity containing totipotent cells. Scale bars: 100 μm (A); 50 μm (B); 30 μm (C); 20 μm (D).

Gemmuloscleres (Figs 6–8) slender birotules 19.8–48.6 μm (35.1 ± 5.5) in length, with narrow spiny shaft 2.7–4.4 μm (3.3 ± 0.3) in width. Shaft spines of three types (a) simple, short curved to straight, smooth spines, (b) spines with tips arranged in asterose clusters (microspines in rosettes), and (c) large, acute spines up to 3 μm long bearing secondary microspines (Fig. 7). Rotules flat with crenulated/notched to shallowly incised margins and both rotules inner and outer surfaces bearing numerous microspines sometimes in radial tows (Fig. 8A) of significantly different diameters t (74) = 18.67, p < 0.00005) (Fig. 6). Large proximal rotules 19.4–24.4 μm (21.6 ± 1.1) in diameter, small distal rotules 16.6–21.7 μm (18.9 ± 1.1) in diameter.

Figure 6.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Size differences in proximal and distal rotules. Scale bars: 5 μm (A); 5 μm (B); scale bars are slightly different in length.

Habitat

(Fig. 1B). All four specimens of Heterorotula lucasi sp. nov. were found bearing gemmules on the underside of shaded rocky substrate in shallow running water at an altitude of 325 m. Associated aquatic community was composed of diatoms, Spongillidae of three genera/species Heteromeyenia latitenta (Potts, 1881), Radiospongilla cerebellata (Bowerbank, 1863), and Trochospongilla horrida (Weltner, 1893); Mollusca of two families Pleuroceridae and Corbiculidae, Diptera larvae of the families Chironomidae and Simuliidae; Ephemeroptera larvae of two families Baetidae and Heptageniidae; Trichoptera larvae of family Hydropsychidae, and Odonata larvae of family Gomphidae. The climate of the study area is temperate having an average annual rainfall of 112 cm. In addition to rain events, flow rates of the Pigeon River are influenced by water releases from a hydroelectric dam in Haywood County, North Carolina. Over its 113 km course the Pigeon River drops from an elevation of 800 m at Canton, North Carolina to 310 m at its confluence with the French Broad River near Newport, Tennessee.

Figure 7.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality). Spine morphology of shafts of gemmuloscleres by SEM.

Geographic range

Heterorotula lucasi sp. nov. is only known from Pigeon River (type locality, 35.9396, −83.1786) in Tennessee. The location of this single population lays far outside the previously known range of the genus.

Figure 8.

Heterorotula lucasi sp. nov. from the Pigeon River, Tennessee (type locality) A crenulated margins and miceospines of rotules and gemmulosclers B variation in size and spines of gemmuloscleres. Scale bars: 30 μm (B); 20 μm (A).

Discussion

The genus Heterorotula was erected by Penney and Racek (1968: 96–97) to allocate five species from the Australasian Region (Fig. 9), i.e., Heterorotula capewelli (Bowerbank, 1863) as type species, Heterorotula kakahuensis (Traxler, 1896), Heterorotula multidentata (Weltner, 1895), Heterorotula multiformis (Weltner, 1910), and Heterorotula nigra (Lendenfeld, 1887) for genus transfer (see Bowerbank 1863; von Lendenfeld 1887; Weltner 1895, 1910; Traxler 1896; Penney and Racek 1968; Rützler 1968) from genera Ephydatia Lamouroux, 1816, Spongilla Lamarck, 1816, Tubella Carter, 1881, and Meyenia Potts, 1882 with junior synonyms, e.g., Spongilla capewelli Bowerbank, 1863; Spongilla sphaerica Lendenfeld, 1887, Tubella nigra Lendenfeld, 1887, Ephydatia multidentata (Weltner, 1895), Tubella multidentata Weltner, 1895, Ephydatia kakahuensis Traxler, 1896, Ephydatia lendenfeldi Traxler, 1896, Ephydatia multiformis Weltner, 1910, and Ephydatia nigra Gee, 1931.

Figure 9.

Disjunct biogeographic pattern of genus Heterorotula (Porifera, Spongillida, Spongillidae) with enclaves in Nearctic and Neotropical regions. The Nearctic H. lucasi sp. nov. from Tennessee is indicated in red. Heterorotula multidentata is considered an alien species in Japan.

A year later, Heterorotula caledonensis (Rützler, 1968) was described as Ephydatia multidentate f. caledonensis by Rützler (1968). In his synopsis on the Australian freshwater sponges, Racek erected Heterorotula contraversa (Racek, 1969). Later, Volkmer-Ribeiro and Motta (1995) described Heterorotula fistula from Brazil. Additionally, H. multidentata was reported in Japan (Palaearctic) by Masuda (1998, 2006) and Ishijima et al. (2008) as an alien species (Fig. 9).

The reason given by Penney and Racek (1968: 96–97) to justify the erection of the new genus was that “The peculiar structure and often greatly varying length of the gemmoscleres, so typical for this genus.” They also stated that: “Heterorotula is more closely related to Ephydatia than to any other genus.” Effectively not all the Heterorotula species share very close gemmuloscleres morphologies and, in some cases, a correct identification is not easy.

As for the morphotraits of Heterorotula species, Penney and Racek (1968), Racek (1969), and Manconi and Pronzato (2002) focused on length differentials of gemmuloscleres, morphologies of rotule margins, and diameter differences between proximal and distal rotules. An exhaustive and clear key together with images was provided by Racek (1969: 292–293) for morphological divergencies among the five Australasian Heterorotula species. As for the main diagnostic traits of the two genera Heterorotula and Ephydatia, see the following key.

Key to the genera Ephydatia and Heterorotula

1	Gemmuloscleres only birotules of one length (short shaft) radially arranged; rotule margins evidently indented and spiny with marginal teeth deep and straight; pneumatic layer chambered; microscleres absent; megascleres as microspiny and/or smooth oxeas	*Ephydatia*
–	Gemmuloscleres only birotules of varying length with rotules (short to long shaft) radially arranged; rotules frequently of different diameter, margins crenulated/incised, with many small spines; pneumatic layer fibrous to chambered; microscleres absent; megascleres as microspiny and/or smooth oxeas	*Heterorotula*

As for the only record of the genus known until now from Americas, Heterorotula fistula is an intriguing species for its biogeographic location and palaeoecology. It is recorded as a fossil/subfossil taxon from spongolites remains in sedimentary deposits of permanent and temporary freshwater bodies of the subequatorial Brazilian areas of Rio Grande do Norte, Goiás Mato Grosso do Sul and Minas Gerais in the Neotropical Region (Volkmer-Ribeiro and Motta 1995; Machado et. al. 2014, 2016; Docio et. al. 2021). Although its subfossil condition cannot support its status as either a true living species or a recently extinct one, the Neotropical enclave of this species enlarged the disjunct biogeographic pattern of Heterorotula to the western hemisphere (Fig. 9).

In any case, the very different geological histories of the Gondwanian, Australasian, and Neotropical regions, after the Pangea breakup (~175 Mya), do not provide an explanation for this biogeographic pattern of Heterorotula. This task is made more difficult because very few ancient fossils of freshwater sponges have been found (Pronzato et al. 2017; Samant et al. 2021).

Results of a comparative analysis of H. lucasi sp. nov. with congeneric species, on the basis of museum collection and original descriptions, revealed that it significantly diverges from all other species of Heterorotula by a few robust characters.

The growth form, oscules, color, and skeletal architecture are not diagnostic morphotraits for the new species and for genus Heterorotula, as for most Spongillida. The absence of skeletal microscleres is shared by all species of the genus.

The trait “megascleres as fusiform oxeas prevalently spiny to nearly spineless” is partly and differently shared with some Heterorotula species. The comparsion between the type species H. capewelli and H. lucasi sp. nov. revealed that the megascleres of the former (195–300 × 13–18 μm) are stout oxeas predominantly smooth with few evident scattered spines, while those of the new species are slimmer oxeas predominantly and abundantly microspiny. The oxeas lengths range reported by Penney and Racek (1968) for other species is from H. nigra (224–360 × 7–13 μm), H. multidentatae (284–320 × 10–18 μm), H. multiformis (330–420 × 13–20 μm) to H. kakahuensis (185–260 × 9–12 μm). Length and width measurements for megascleres, gemmuloscleres, and gemmules of the known living species of Heterorotula are presented in Table 2.

Table 2.

Download as

CSV

XLSX

Length and width ranges, in microns, for spicules and gemmules of living species of Heterorotula.

Species	ML	MW	LBL	SBL	BSW	PRD	DRD	GW
H. capewelli	195–330	13–18	38–52	34–45	3–4	24–45	20–23	510–560
H. nigra	224–360	7–13	56–73	35–48	2–4	13–16	10–14	230–360
H. multidentata	284–320	10–18	64–84	32–48	4–6	19–22	17–20	490–580
H. kakahunesis	185–260	9–12	30–42			17–22		380–540
H. multiformis	330–420	13–20	35–52	24–44	2–4	14–24	14–18	480–680
H. caldonensis	250–410	8–20	35–85		4	19–26	18–22	450–600
H. controversa	210–395	12–21	21–57		3–4	20–24	18–21	470–590
*H. lucasi*	223–335	7.7–13.7	19.8–48.6		2.7–4.4	19.4–24.4	16.6–21.7	448–613

The gemmule architecture and dimensions and its morphotraits, i.e., spicular cage, pneumatic layer, and foramen matches the genus range. The gemmuloscleres of H. lucasi sp. nov. are unique. Both rotules are finely spined and with crenulated/incised margins. The slim shaft of gemmuloscleres displays spines moderately long and variable in length.

Only the type species of the genus, H. capewelli, shares with H. lucasi sp. nov. the trait “crenulated rotules.” The term “crenulated” refers to the New Latin term crenulatus, from crenula, diminutive of Medieval Latin crena (notch) was introduced by Racek (1969: 293) and meaning “Having a margin contour with shallow, usually rounded notches and projections; finely notched or scalloped.” However, the two species diverge for gemmulosclere shaft morphologies, H. capewelli has smooth to finely granulated shafts whereas the shafts of the new species are variously spined. All other species of the genus show gemmuloscleres with margins of rotules variously indented/incised and with variably long to very long shafts.

Among freshwater sponges gemmuloscleres birotules are shared by several genera having a wide range of rotule morphotraits, e.g., flat, curved, umbonate, indented, hooked, smooth, and variably spiny/tubercled. In Heterorotula, the morph “rotules with margins only crenulated” seems to be shared by only two species, H. capewelli and H. lucasi sp. nov. However, also the margins of the rotules of the Neotropical Ephydatia facunda (Pinheiro et al. 2004) resemble those of the new species but diverges from it for the shaft morphology, whereas the Middle Eocene fossil E. cf. facunda from Canada totally diverges from H. lucasi sp. nov. in the outline of the birotules (Pisera et al. 2016).

In contrast, it is noteworthy that the southeastern Nearctic harbors Ephydatia millsi (Potts, 1887), which is exclusively endemic to the type locality at Sherwood Lake near DeLand, Florida (Potts 1887; Penney and Racek 1968; Manconi and Pronzato 2016). This aberrant species, which does not match the diagnosis of Ephydatia, was considered “eventually to be an ecomorph of one of the more widely distributed Ephydatia species” (Penney and Racek 1968: 96) because it displays the morph “spiny, flat rotules with lacinulate margins” (Penney and Racek 1968; Reiswig et al. 2010). Ephydatia millsii must still be considered as rather insufficiently known.

The gemmuloscleres of H. capewelli are birotules with a slender, smooth shaft bearing sometimes few spines. Rotules with unequal diameter are flat with small spines and margins irregularly crenulated with rare teeth. In comparison the birotules of H. lucasi sp. nov. are smaller and with margins of rotules irregularly crenulate/incised and evidently spiny, with also a stouter shaft bearing abundant rosetta-shaped microspines and rare long spines. Diameter of rotules is unequal.

Summarizing, the new species is characterized by slimmer megascleres that are predominantly and abundantly microspiny to nearly spineless; smaller gemmuloscleres that are abundantly microspiny on rotules and the stout shaft (the latter with also spines in rosettas), and a very distant disjunct geographical range.

This biogeographic enclave in Tennessee contributes to the understanding of the origin of Nearctic inland water biodiversity, biogeographical patterns, and morphological adaptive traits in Nearctic sponges. The present record matches the recent discovery in Tennessee of Cherokeesia armata Copeland, Pronzato & Manconi, 2015, the first living Nearctic Potamolepidae (Copeland et al. 2015). Data confirm that the Appalachian region (Ordovician–Permian origin) of Tennessee and, in general, of southeastern North America have high levels of diversity and endemicity (Curtin et al. 2002; Hodkinson 2010; Erlandson et al. 2021).

With the present record of a new species in Tennessee, the biogeographic pattern of the genus Heterorotula matches the Australasian–Pacific Islands–Neotropical regions in the southern hemisphere (Australia n = 5 species; New Caledonia n = 2; New Zealand n = 1; Brazil n = 1 species), with one spot in a Nearctic enclave (n = 1 species, H. lucasi sp. nov.) and an alien species in the insular easternmost Palaearctic (Japan n = 1) (Fig. 9) (Manconi and Pronzato 2008; Manconi et al. 2016; Pronzato and Manconi 2019; de Voogd et al. 2022).

Not considering the Japanese record of an alien species, the scenario that arose with the unexpected discovery of a Heterorotula species in the southwestern Laurasian Nearctic (North America), and the subsequent tripartite geographic range, is anomalous but not unique to and shows a similitude with, for example, marsupials of which the majority of species is strictly Australasian but having some key species recorded from the Neotropical and Nearctic regions (e.g., Opossum, Didelphis virginiana (Voss 2022)).

Acknowledgements

J. Copeland and S. Kunigelis are grateful to the Tennessee Wildlife Resources Agency for funding. Funding to R. Manconi was provided by the Regione Autonoma della Sardegna [grant RAS2012-LR7/2007-CRP-60215], Università di Sassari [grant Fondo di Ateneo per la Ricerca 2019-2021], Fondazione di Sardegna [grant FdS/RAS-2016/CUP J86C1800082005], and Parco Nazionale dell’Asinara [grant PNA-2016].

References

Abell RA (2000) Freshwater Ecoregions of North America: a Conservation Assessment. Island Press, Washington DC, 368 pp. https://archive.org/details/freshwaterecoreg0000unse

Bartlett RA (1995) Troubled Waters Champion International and the Pigeon River Controversy University of Tennessee Press, Knoxville, 348 pp.

Bowerbank JS (1863) A monograph of the Spongillidae. Proceedings of the Zoological Society of London 1863: 440–472, pl. 38.

Collen B, Whitton F, Dyer EE, Baillie J, Cumberlidge N, Darwall WR, Pollock C, Richmond N, Soulsby A, Bohm M (2014) Global patterns of freshwater species diversity, threat, and endemism. Global Ecology and Biogeography 23(1): 40–51. https://doi.org/10.1111/geb.12096

Coombs JA (2010) Pigeon River recovery project: 2001–2010. https://volumes.lib.utk.edu/news/presentation-on-the-pigeon-river-recovery-project-2001-to-2010/ [Accessed on: 2022-6-15]

Coombs J, Wilson JL, Burr J, Fraley SJ, Russ TR (2010) Pigeon River recovery project: bringing back aquatic diversity. https://www.se-eppc.org/2010/pdf/Coombs.pdf [Accessed on 2020-4-15]

Copeland J, Pronzato R, Manconi R (2015) Discovery of living Potamolepidae (Porifera: Spongillina) from Nearctic freshwater with description of a new genus. Zootaxa 3957(1): 37–48. https://doi.org/10.11646/zootaxa.3957.1.2

Copeland J, Kunigelis S, Tussing J, Jett T, Rich C (2019) Freshwater sponges (Porifera: Spongillida) of Tennessee. American Midland Naturalist 181(2): 310–326. https://doi.org/10.1674/0003-0031-181.2.310

Copeland J, Kunigelis S, Stuart E, Hanson K (2020) First records of freshwater sponges (Porifera: Spongillidae) for Great Smoky Mountains National Park. Journal. Tennessee Academy of Science 95(1): 59–62. https://doi.org/10.47226/JTAS-D-18-00004

Curtin M, McCown D, Morris E, Shields C, Whitley K (2002) Land Use and Biodiversity on the Highland Plateau: a Carolina Environmental Program Report. Highlands Biological Station, Highlands, NC, 57 pp.

de Voogd NJ, Alvarez B, Boury-Esnault N, Carballo JL, Cárdenas P, Díaz M-C, Dohrmann M, Downey R, Hajdu E, Hooper JNA, Kelly M, Klautau M, Manconi R, Morrow CC, Pisera AB, Ríos P, Rützler K, Schönberg C, Vacelet J, van Soest RWM (2022) World Porifera Database. Heterorotula Penney & Racek, 1968. http://www.marinespecies.org/porifera/porifera.php?p=taxdetails&id=167176 [Accessed on 2021-7-11]

Docio L, Rasbold GG, da Silva ALC, Parolin M, Caxambu MG, Pinheiro U (2021) An assessment of the wealth of information given by sponge spicules as a paleoenvironmental tool: The case of two lakes in northeast (Brazil). Journal of South American Earth Sciences 107: 103099. https://doi.org/10.1016/j.jsames.2020.103099

Elkins D, Sweat SC, Kuhajda BR, George AL, Hill KS, Wenger SJ (2019) Illuminating hotspots of imperiled aquatic biodiversity in the southeastern US. Global Ecology and Conservation 19: 1–13. https://doi.org/10.1016/j.gecco.2019.e00654

Erlandson K, Bellemare J, Moeller DA (2021) Limited range-filling among forest herbs in eastern North America and its implications for conservation with climate change. Frontiers in Ecology and Evolution 9: 1–13. https://doi.org/10.3389/fevo.2021.751728

Etnier DA, Starnes WC (1993) The Fishes of Tennessee. The University of Tennessee Press, Knoxville, 681 pp. https://trace.tennessee.edu/utk_utpress/2/ [Accessed on: 2022-6-15]

Hodkinson BP (2010) First Assessment of lichen diversity for one of North America’s ‘biodiversity hotspots’ in the southern Appalachians of Virginia. Castanea 75(1): 126–133. https://doi.org/10.2179/09-033.1

Ishijima J, Iwabe N, Masuda Y, Watanabe Y, Matsuda Y (2008) Sponge cytogenetics—Mitotic chromosomes of ten species of freshwater sponge. Zoological Science 25(5): 480–486. https://doi.org/10.2108/zsj.25.480

Machado VS, Volkmer-Ribeiro C, Iannuzzi R (2014) Late Pleistocene climatic changes in central Brazil indicated by freshwater sponges. International Journal of Geosciences 5(8): 799–815. https://doi.org/10.4236/ijg.2014.58071

Machado VDS, Volkmer-Ribeiro C, Iannuzzi R (2016) Investigation of freshwater sponges spicules deposits in a karstic lake in Brazil. Brazilian Journal of Biology 76(1): 36–44. https://doi.org/10.1590/1519-6984.09814

Manconi R, Pronzato R (2000) Rediscovery of the type material of Spongilla lacustris (L., 1759) in the Linnean herbarium. The Italian Journal of Zoology 67(1): 89–92. https://doi.org/10.1080/11250000009356300

Manconi R, Pronzato R (2002) Spongillina n. subord. Lubomirskiidae, Malawispongiidae n. fam., Metaniidae, Metschnikowiidae, Palaeospongillidae, Potamolepidae, Spongillidae. In: Hooper J, van Soest RWM (Eds) Systema Porifera. A guide to the classification of sponges. Vol. 1. Kluwer Academic/Plenum Publisher, New York, 921–1019. https://doi.org/10.1007/978-1-4615-0747-5_97

Manconi R, Pronzato R (2008) Global diversity of sponges (Porifera: Spongillina) in freshwater. In: Balian EV, Lévêque C, Segers H, Martens K (Eds) Freshwater animal diversity assessment. Hydrobiologia 595: 27–33. https://doi.org/10.1007/s10750-007-9000-x

Manconi R, Pronzato R (2016) Phylum Porifera. In: Thorp J, Rogers DC (Eds) Keys to Nearctic Fauna. Thorp and Covich’s Freshwater Invertebrates, 4^th Edn., Vol. 2. Academic Press, London, UK, 39–83. https://doi.org/10.1016/B978-0-12-385028-7.00003-2

Manconi R, Cubeddu T, Pronzato R (2016) Australian freshwater sponges with a new species of Pectispongilla (Porifera: Demospongiae: Spongillida). Zootaxa 4196(1): 61–76. https://doi.org/10.11646/zootaxa.4196.1.3

Masuda Y (1998) A scanning electron microscopy study on spicules, gemmule coats, and micropyles of Japanese freshwater sponges. In: Watanabe Y, Fusetani N (Eds) Sponge Sciences. Multidisciplinary Perspectives. Springer Verlag, Tokyo, 295–310.

Masuda Y (2006) An overview of Japanese freshwater sponges. TAXA. Proceedings of the Japanese Society of Systematic Zoology 20: 15–22. https://www.jstage.jst.go.jb/browse/taxa

McLarney WO [Compiler] (1999) Protection of aquatic biodiversity in the southern Appalachian National Forests and their watersheds: information for use in the forest plan revision process and beyond. A Report of the Southern Appalachian Forest Coalition and Pacific Rivers Council, Portland, 34 pp.

Penney JT, Racek AA (1968) Comprehensive revision of a worldwide collection of freshwater sponges (Porifera: Spongillidae). Bulletin - United States National Museum 272(272): 1–184. https://doi.org/10.5479/si.03629236.272.1

Pickering J, Kays R, Meier A, Andrew S, Yatskievych K (2003) The Appalachians. In: Mittermeier C, Mittermeier G, Pilgrim J, Fonseca G, Konstant WR, Brooks T (Eds) Wilderness – Earth’s last wild places. Conservation International, Arlington, VA, 458–467.

Pinheiro US, Hajdu E, Correa MD (2004) First description of gemmules of Ephydatia facunda Weltner, 1895 (Porifera, Haplosclerida, Spongillidae) by scanning electron microscopy, with underwater observations of a large population from north-eastern Brazil. Journal of Natural History 38(9): 1071–1080. https://doi.org/10.1080/0022293031000064404

Pisera A, Manconi R, Siver R, Wolfe A (2016) The sponge genus Ephydatia from the Middle Eocene: Environmental and evolutionary significance. Palaontologische Zeitschrift 90(4): 673–680. https://doi.org/10.1007/s12542-016-0328-2

Potts E (1881) A new form of freshwater sponge. Proceedings. Academy of Natural Sciences of Philadelphia 1881(2): 176.

Potts E (1887) Contribution toward a synopsis of the American forms of freshwater sponges with description of those named by other authors and from parts of the world. Proceedings Academy of Natural Sciences of Philadelphia 39: 158–279.

Pronzato R, Manconi R (2019) An overview on the freshwater sponge fauna (Demospongiae: Spongillida) of New Zealand and New Caledonia with new insights into Heterorotula from deep thermal vents of the Lake Taupo. Journal of Natural History 53(35–36): 2207–2229. https://doi.org/10.1080/00222933.2019.1694716

Pronzato R, Pisera A, Manconi R (2017) Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review. Acta Palaeontologica Polonica 62(3): 467–495. https://doi.org/10.4202/app.00354.2017

Racek AA (1969) The freshwater sponges of Australia (Porifera: Spongillidae). Marine and Freshwater Research 20(3): 267–310. https://doi.org/10.1071/MF9690267

Reiswig HM, Frost TM, Ricciardi A (2010) Porifera. In: Thorp JH, Covich AP (Eds) Ecology and Classification of North American Freshwater Invertebrates. Academic Press, New York, 91–123. https://doi.org/10.1016/B978-0-12-374855-3.00004-2

Rützler K (1968) Fresh-water sponges from New Caledonia. Cahiers de l’Office de la Recherche Scientifique et Technique d’Outre-Mer (Hydrobiologie) 2(1): 57–66. https://repository.si.edu/bitstream/handle/10088/7854/iz_Ruetzler_1968b.pdf [Accessed on: 2022-6-15]

Samant B, Pronzato R, Mohabey DM, Kumar D, Dhobale A, Pizal P, Manconi R (2021) Insight into the evolutionary history of freshwater sponges: a new genus and new species of Spongillida (Porifera: Demospongiae) from Upper Cretaceous (Maastrichtian) Deccan intertrappean lacustrine deposits of the Malwa Group, Central India. Cretaceous Research 126: 104851. https://doi.org/10.1016/j.cretres.2021.104851

Traxler L (1896) Über einen neuen Süsswasserschwamm aus Neu-Seeland. Természetraja Füzetek 19(1): 102–105[, pl. 2].

University of Tennessee (2021) Pigeon River Recovery Project. https://fwf.utk.website/pigeon/webpages/history.asp

Volkmer-Ribeiro C, Motta JFM (1995) Esponjas formadoras de espongilitos em lagoas no Triângulo Mineiro e ajacências com indicaçao de preservaçao de habitat. Biociencias 3(2): 183–205.

von Lendenfeld R (1887) Die Süsswasser-Coelenteraten australiens. Zoologische Jahrbucher, Abteilungfür Systematik, Geographie und Biologie der Thiere 2: 87–108.

Voss RS (2022) An annotated checklist of recent opossums (Mammalia: Didelphidae). Bulletin of the American Museum of Natural History 455(1): 1–76. https://doi.org/10.1206/0003-0090.455.1.1

Weltner W (1893) Über die Autorenbezeichnung von Spongilla erinaceus. Berichte der Gesellschaft für Naturforschender Freunde Berlin 1893: 7–13.

Weltner W (1895) Spongillidenstudien III. Katalog und Verbreitung der bekannten Süsswasserschwämme. Archiv für Naturgeschichte 61(1): 114–144.

Weltner W (1910) Spongillidae. In: Michaelsen W, Hartmeyer R (Eds) Die Fauna südwest-australiens. Ergebnisse der Hamburger südwest-australischen Forschungsreise 3(5), 137–144.

﻿Abstract

Keywords

﻿Introduction

﻿Study area

﻿Materials and methods

﻿Institutional acronyms

﻿Systematic account

﻿Phylum Porifera Grant, 1836