Echiniscidae Thulin, 1928

Gąsiorek, Piotr & Michalczyk, Łukasz, 2025, Novel integrative data for Indomalayan echiniscids (Heterotardigrada): new species and old problems, Organisms Diversity & Evolution 25 (1), pp. 81-116 : 87-93

publication ID	https://doi.org/10.1007/s13127-023-00628-5
persistent identifier	https://treatment.plazi.org/id/2A7987F0-FFC2-0720-FCB2-FB62F6EDF924
treatment provided by	Felipe
scientific name	Echiniscidae Thulin, 1928
status

Treatment

Family: Echiniscidae Thulin, 1928 View in CoL

Genus: Echiniscus C.A.S. Schultze, 1840 (amended by Gąsiorek et al., 2017)

Species: Echiniscus africanus Murray, 1907

Table 3, Figs. 3 View Fig and 4 View Fig

The specimens from Celebes and Madagascar fully correspond phenotypically with a single individual originating from terra typica in South Africa and examined by us ( Gąsiorek et al., 2022), with a sole exception of the number of spines on the posterior margin of the scapular plate. Originally reported as having six spines ( Murray, 1907), this character was later disclosed as variable ( Gąsiorek & Vončina, 2019; Gąsiorek et al., 2022), and the Malayan specimens conform with this, having either two ( Figs. 3A and B View Fig , 4 View Fig ) or even no spines ( Fig. 3C View Fig ). Other trunk appendages may also be absent ( Fig. 3C View Fig ). The observations on the variability of chaetotaxy in E. africanus fully agree with initial data for a likely population of this species from Hawaii ( Tsaliki et al., 2018). The sister relationship between E. africanus and E. lapponicus (Fig. 2) confirms

◂ Fig. 2 Updated phylogeny of the Echiniscus -like genera in the Bayesian and Maximum Likelihood tree based on nuclear markers (almost identical topologies, see the text for details). Species currently classified within Kristenseniscus given in colour, and newly added Echiniscus spp. —in bold. The scale refers to the Bayesian tree and represents substitutions per position; posterior probability values are provided as first at the nodes, followed by bootstrap values after slash; The asterisk (*) indicates maximal support, pound sign (#) indicates no support. Diploechiniscus oihonnae and Testechiniscus spitsbergensis constitute an outgroup a previously hypothesised relatedness based on the presence of centrodorsal spines, often crossed in a scissor-like manner ( Fig. 4 View Fig ). This character can be now regarded as a synapomorphy for this clade.

Gąsiorek and Vončina (2019) have already stressed there are no morphological criteria for distinguishing between E. africanus and E. semifoveolatus . The latter species was reported from Japan and China ( Qiao et al., 2013; Suzuki, micrometer) of selected morphological structures of adult females of Echiniscus africanus mounted in Hoyer’s medium 2017). Considering the fact that E. africanus is potentially a pantropical species (Africa, Hawaii, Madagascar, the Malay Archipelago), it is imperative to test the conspecificity of these two species, with a potential junior synonymy pertaining to E. semifoveolatus that we designate as nomen inquirendum herein.

Species: Echiniscus minutus sp. nov.

Table 4, Figs. 5 View Fig and 6 View Fig

Locus typicus and type material: 0°57′58″S, 119°46′25″E, 1309 m asl; Indonesia, Celebes, Sulawesi Tengah, Marowola Mts.; moss from tree bark. Holotype (mature female on the slide ID.374.17), seven paratypic females and one exuvia (slides ID.374.15–16, ID.485.02, ID.486.01, ID.517.01, 26, ID.564.01). All are deposited in the Institute of Zoology and Biomedical Research of the Jagiellonian University in Kraków , Poland. GoogleMaps

Etymology: From Latin minutus = small, little. The name underlines the minute body size of adults of the new species, being one of the smallest representatives of Echiniscus . Adjective in the nominative singular.

Mature females (i.e. from the third instar onwards; measurements in Table 4). Body plump ( Figs. 5 View Fig , 6 View Fig ) and orange. Minute red eyes present. Primary and secondary clavae typical, of the Echiniscus - type; peribuccal cirri with well-developed cirrophores. Cirrus A very short (<<25% of the body length), with cirrophore. Body appendage configuration A -(B)- C -C d -D -D d -E, with all trunk appendages formed as robust spines with serrated edges ( Figs. 5 View Fig , 6 View Fig ). Spines B reduced, if present ( Fig. 6 View Fig ). Spines C with broad bases, more robust than the remaining appendages ( Fig. 5 View Fig ).

Dorsal plates strongly sclerotised and well-demarcated from each other, with the modified spinulosus type of sculpturing, consisting of typical pores located between aberrantly expanded epicuticular layer ( Figs. 5 View Fig , 6 View Fig ). Epicuticular layer forms striae in the median plates and the anterior portions of paired segmental plates and more or less separated granules in the scapular plate, lateral portions of paired segmental plates and the anterior margin of the caudal (terminal) plate ( Figs. 5 View Fig , 6 View Fig ). Both structures are atypical for the spinulosus morphogroup. The sculpturing vanishes in the centroposterior portions of paired segmental plates and in the lateralmost portions of the caudal plate. Pores are always without dark endocuticular rings. The cephalic plate consists of two weakly delineated halves, with a small, anterior chalice-like incision. The cervical (neck) plate is in the form of a narrow, grey belt, adjacent to the scapular plate; it can be unsculptured ( Fig. 5 View Fig ) or sculptured, with minute pores ( Fig. 6 View Fig ). The scapular plate is non-facetted, with a central weak sulcus/ incision ( Fig. 5 View Fig ) and lateral sutures at the level of primary clavae demarcating unsculptured, rectangular portions ( Figs. 5 View Fig , 6 View Fig ). Three median plates: m1 and m3 are unipartite, whereas m2 is bipartite, with a wide transverse belt ( Fig. 5 View Fig ). Two pairs of large segmental plates, their narrower anterior portions are separated from posterior portions by wide, non-sculptured transverse belts. The caudal (terminal) plate with short unsclerotised incisions, non-facetted ( Figs. 5 View Fig , 6 View Fig ).

Ventral cuticle smooth beside the gonoporal area, where a pair of grey, unsculptured genital plates flanks a hexapartite gonopore anteriorly to a trilobed anus, placed between legs IV. Pedal plates are present on all legs, small with minute pores on legs I–III, and unsculptured on legs IV ( Fig. 6 View Fig ). Weak pulvini present on all legs ( Fig. 5A View Fig ). Spine I rudimental and exhibiting various stages of reduction: from a punctiform mass ( Fig. 5A View Fig ) to minute cone ( Fig. 6 View Fig ). Dentate collar IV is composed of numerous short teeth. Papilla on leg IV is present ( Figs. 5 View Fig , 6 View Fig ). Claws short; claws IV higher than claws I–III. External claws on all legs are smooth. Internal claws with needle-like spurs positioned at ca. 25% of the claw height, tightly adjacent to the branches and homomorphic on all claws ( Fig. 6 View Fig , insert).

Juveniles, larvae and eggs. Unknown.

Phylogenetic position: Echiniscus minutus sp. nov. is a sister species to the clade of the mostly tropical/Southern Hemisphere taxa (Fig. 2).

Phenotypic differential diagnosis: Small body size of adult females, a complex subtype of sculpturing (intermingled pores and granules) and the reduction of spine I make a combination of traits allowing for an easy identification of E. minutus sp. nov. There are several species that exhibit a similar morphotype of E. minutus sp. nov. but can be distinguished from it as follows:

• Echiniscus marcusi , a representative of Australian fauna ( Pilato et al., 1989), being the only other member of the spinulosus morphogroup with well-developed striae in some elements of the dorsal armour, by the presence of epicuticular granules (present in E. minutus sp. nov. vs absent in E. marcusi ), and by the presence of pores on legs (present in E. minutus sp. nov. vs absent in E. marcusi ).

• Several species having typically strongly serrated trunk spines, such as E. duboisi or E. manuelae ( Richters, 1902; da Cunha & do Nascimento Ribeiro, 1962; Claxton, 1996; Gąsiorek & Kristensen, 2018), exhibit a uniform, classical spinulosus sculpturing without the epicuticular matrix in the form of striae and granules.