Iberobathynellini Camacho & Serban 1998
Creators: name: Camacho, Ana Isabel
name: Mas-Peinado, Paloma
name: López-Estrada, E. Karen
name: Dorda, Beatriz A.
name: Rey, Isabel
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Bathynellacea
Parabathynellidae

description: Tribe Iberobathynellini Camacho & Serban, 1998
Diagnosis (after Camacho et al., 2000): AI seven-segmented, very rarely six-segmented. AII three-segmented (fig. 9 A-J), small and with four setae on the last segment. Common or special structure (hook-like teeth) (fig. 9S) on labrum, usually with eight main teeth. Strongly inclined connection of the mandible with the cephalon. Usually seven pairs of thoracopods, thoracopod I with a one-, two- or three-segmented exopod (fig. 13 A-K) and the rest of the thoracopods with a two, three or four-segmented exopod; cox a of thoracopods with distinct conical projection at inner distal corner; thoracopod I without epipod. Male thoracopod VIII of type “ Iberobathynella ” (fig. 15 A-K): large outer lobe, partially fused with basipod; small exopod on latero-external side of basipod, covered by outer lobe; endopod always present with distal end oriented towards the latero-external side. Pleopods usually absent.
In the Iberobathynellini tribe, the outer lobe of the male thoracopod VIII is well developed in both length and width, and is highly distinctive as a massive element of the lateral face always close to the endopod, in some case covering the distal part of the basipod, a very marked feature in I. rouchi; the main axis of the lobe can be vertical to inclined on the postero-distal or antero-distal side; its fusion with the basipod (Serban, 1977) is at the level of the basal parts of the posterior edge of the lobe and the anterior face of the basipod; the exopod is greatly reduced. In Iberobathynellini, the outer lobe (O.lb) is small; in Parabathynella (fig. 15M), it is narrow and slightly longer than the exopod and the outer lobe is not fused with the basipod. The exopod is located on the lateral face of the basipod and is covered by the distal part of the outer lobe, however, its small size makes it the most difficult structure to observe in species of the Iberobathynellini tribe.
The division of the tribe into three subtribes (Camacho & Serban, 1998) is based on the diversification of the thoracopods at the exopod level in Iberobathynellina and Paraiberobathynellina, on the different number of thoracopods in Hexaiberobathynellina (table 3), and to organize the taxonomy of the morphogroup and to understand the relationships between the genera.
Type genus: Iberobathynella Schminke, 1973
Subtribe: Iberobathynellina Camacho & Serban, 1998
Paraiberobathynellina Camacho & Serban, 1998
Hexaiberobathynellina Camacho & Serban, 1998
The main morphological differences identified among the three subtribes and six genera (and subgenera) in 1998 are shown in table 3. Morphospace was organized by fitting all known species into the three subtribes and established subgenera.
The number of thoracopods clearly separated the subtribes Iberobathynellina and Paraiberobathynellina from Hexaiberobathynellina, whichhavesevenandsix, respectively. More than two segments on the exopod of thoracopods II to VII are only found in the genera of the subtribe Paraiberobathynellina (Paraiberobathynella and Texanobathynella) and in I. (E.) magna (in thoracopods IV and V). The number of teeth in the distal endite of MxI also distinguishes the genera: five in Texanobathynella, six in Hexaiberobathynella and Guadalopebathynella, seven in Californibathynella and Paraiberobathynella, and in the subgenera of Iberobathynella, seven in Iberobathynella and Espanobathynella and six in Asturibathynella. Guadalopebathynella shares many character states with the subgenus Asturibathynella, but its curved (hook-like) teeth in both the labrum and distal endite of MxI clearly distinguish G. puchi from I. (A.) imuniensis, with which it is most similar. Other characters are not exclusive to a single subgenus or genus; however, the set of characters allowed the identification of the nine morphotypes corresponding to the six genera and five subgenera (see table 3). But as new species were found, the characters overlapped between subtribes and subgenera and some species such as I. pedroi Camacho, 2003 no longer fit into any of the 3 subgenera of Iberobathynella (table 4).
Comparative morphological analysis of the Iberobathynellini and non-Iberobathynellini genera from the study area
Table 4 lists the set of character states exhibited by the 33 morphotypes of the Iberobathynellini tribe, and the five species of Montanabathynella and Parabathynella, included in the present study. This list highlights the level of variability in the main morphological characters often used to discriminate taxa in taxonomic studies of this group of crustaceans. Below, we briefly review the main characters and discuss the distribution of variability among the nine taxa (genera and subgenera). Of the species of Iberobathynella, 21 can be placed into one of the three morphologically established subgenera. However, the species I. pedroi displays character states present in the subgenera Asturibathynella and Espanobathynella and is therefore compared separately.
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Species belonging to the Iberobathynellini tribe vary considerably in size, with some barely reaching or exceeding one millimetre: for instance, I. celiana measures 0.9 mm; I. serbani, 1.0 mm; I. lamasonensis and I. pedroi, 1.2 mm and Californibathynella californica, 1.1 mm. Some species of the subgenera Asturibathynella and Espanobathynella can reach 2.2 mm and 1.9 mm, respectively. Paraiberobathynella fagei and Pi. notenboomi can reach 2.8 mm, while the species I. gracilipes and I. paragracilipes, both from the subgenus Iberobathynella, are some of the largest, with some specimens measuring up to 4.0 mm or 3.2 mm, respectively. Large species are also found in Montanabathynella, such as M. salish Camacho, Newell & Stanford, 2009, which can measure up to 3.0 mm. Finally, some species of Parabathynella can measure 2.5 mm.
The variability in the selected morphological structures are described below and illustrated in figs. 9 to 17.
Antennule: Seven-segmented AI characterizes most species of the tribe (28 species). Two species of Iberobathynella (I. celiana and I. guarenensis) and four of Texanobathynella present a six-segmented AI. The five species comprising the genera Montanabathynella and Parabathynella also have a seven-segmented AI. The number of setae and aesthetascs on the segments varies among the genera and species.
Antenna (fig. 9): All species of the tribe have three segments (fig. 9 A-J) and only setae (four) on the last segment; segment length may vary slightly between species. Montanabathynella (fig. 9K) has six segments while Parabathynella has five (fig. 9L).
Labrum (fig. 9 M-X): The labrum presents as relatively flat (fig. 9M, N, R, T, U), concave (fig. 9O, P, Q, V) or convex (fig. 9S). Most species have eight main teeth on the labrum except I. guarenensis (10 teeth); I. magna (9 teeth); Pi. notenboomi (11 teeth) (fig. 9U) and those of Texanobathynella (9 or 10 teeth) (fig. 9V). The labrum in Guadalopebathynella is convex (fig. 9S), and has eight hook-like shaped teeth. Compared with the other species, the number of main teeth varies more in Montanabathynella (8 to 12 teeth; fig. 9W) and Parabathynella (8 to 13 teeth; fig. 9X).
Mandible (fig. 10): The number of teeth in the pars incisive varies between four and 12 in Iberobathynella: six to 12 in the subgenus Iberobathynella (fig. 10F), four to seven in Asturibathynella (fig. 10A, B) and four to eight in Espanobathynella (fig. 10D, E); I. pedroi has six teeth (fig. 10C). Fewer teeth characterize the other genera: Hexaiberobathynella has four to six (fig. 10H), Californibathynella has five (fig. 10J), Paraiberobathynella has six to nine, despite having very large specimens (fig. 10G), and Texanobathynella has four to six (fig. 10K). Montanabathynella (fig. 10L) and Parabathynella (fig. 10M) have only four teeth except M. salish, which has five. In the pars molaris, the number of teeth is highly variable among species of the tribe, ranging between five and 16; teeth features also varies: they can be with or without denticles, have the two most proximal teeth always joined and have fine setules. Species with the most teeth belong to the subgenera Iberobathynella (6 to 16 teeth) (fig. 10F) and Paraiberobathynella (6 to 12 teeth) (fig. 10G); Montanabathynella has six or seven teeth (fig. 10M), and P. motasi has only four (fig. 10N), whereas P. badenwuerttembergensis has eight. All species have a small tooth on the ventral edge between both parts that is variable in size, more or less triangular and, in some cases, with small setae at the base (fig. 10D, F, H). The mandibular palp consists of one segment that is variable in size, with a single seta that either reaches the distal edge of the mandible (fig. 10D, F, J, K), surpasses it (in five species only), as in P. motasi (fig. 10N), or does not even reach it (fig. 10G).
Maxillulle (fig. 11): In the proximal endite, all species have four claws (spine-like) of different sizes. The number of teeth in the distal endite varies between six and seven in Iberobathynella but is constant in all species of each subgenus: six teeth in Asturibathynella (fig. 11A, B) and seven in Espanobathynella (fig. 11D, E) and Iberobathynella (fig. 11F), and also in I. pedroi (fig. 11C). Paraiberobathynella and Californibathynella each have seven teeth (fig. 11G, J); Hexaiberobathynella and Guadalopebathynella have six (fig. 11H, I); Texanobathynella has five (fig. 11K); Montanabathynella has eight to nine (fig. 11M) and Parabathynella has five (as in P. motasi, fig. 11L) to six or nine. The three subterminal smooth setae on the outer distal margin, common in the family Parabathynellidae, are of different lengths, which differ among the species of the tribe.
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Maxilla (fig. 12): The three segments comprising maxilla differ in size in the different species, however, the third segment is always the longest, and the second, the shortest. In the proximal segment, most species of the tribe present a single seta (fig. 12A, B, D, E, F-I, J); the two species of Hexaiberobathynella lack setae (fig. 12H), as do the species I. asturiensis, I.parasturiensis, I.cavadoensis, I.ortizi, I.lamasonensis (fig. 12C), I. serbani and I. guarenensis, all of the subgenus Asturibathynella, and I. pedroi. The two species of Montanabathynella have two setae (fig. 12K), as do the species of Parabathynella except P. motasi (fig. 12L), which has one. In the second segment, species of Iberobathynella have four setae (fig. 12 A-D), as do those of Guadalopebathynella (fig. 12H), Hexaiberobathynella (fig. 12F) and Californibathynella (fig. 12I), whereas Paraiberobathynella has three (fig. 12G); Texanobathynella has two, three or four (fig. 12J); Montanabathynella has four or five (fig. 12K) and Parabathynella has two, four or five (fig. 12L). The number of setae in the third segment of MxII (or third and fourth together) varies very little, between 14 and 16, among genera and species of the tribe (fig. 12 A-J) (some specimens of different species of Texanobathynella present 13 setae). Montanabathynella presents between 19 and 21 setae (fig. 12K), and P. motasi (fig. 12L) and P.stygia Chappuis, 1926 have 12 and 14, respectively, but P. badenwuerttembergensis Fuchs, Hahn & Cho, 2012 has 20.
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Thoracopod I (fig. 13): All species of the tribe lack an epipod on this leg (fig. 13 A-K), as do the species in the genera Montanabathynella (fig. 13l) and Parabathynella (fig. 13M). The basipod has a smooth seta in the distal outer margin. The exopod may have one segment (in 18 species) (fig. 13A, B, D, F, H, J), two segments (fig. 13C, E, H, I, K), (in 14 species) or, in the case of two species of the Paraiberobathynella (fig. 13G) three segments. Irrespective of segment number, the exopod is always shorter than the endopod. Normally, setation consists of three setae in the first or single segment (except in Californibathynella, which only has two distal setae in its single segment) (fig. 13J) and two terminal setae (of which, one is always plumose) in the second and, when present, third segments (fig. 13G); clusters of ctenidia present at the base of setae and on the posterior side (fig. 13C, E, G). Endopod consists of four segments of different sizes: the first is about half the length of the second and third, which are similar in length, and the fourth is very small; on the fourth segment, species of the Iberobathynellini tribe and those in the genera Montanabathynella and Parabathynella all present two terminal (claw-like) setae of different lengths and a shorter subterminal seta; on the third segment all genera have two distal setae (except Texanobathynella, which has only one or no internal seta; fig. 13K), the internal one resembles to a small spine; on the first and second segments, the setation is variable, with different species sharing setal formulas: the formula (1-2-2-3) is shown by some species of the subgenus Asturibathynella (fig. 13A) and by Hexaiberobathynella (fig. 13F); (2-2-2-3), by species of the subgenera Asturibathynella (fig. 13B) and Espanobathynella (fig. 13C) and by Guadalopebathynella (fig. 13I) and Californibathynella (fig. 13J); (2-3-2-3), by Iberobathynella (fig. 13E) and some species of the subgenera Espanobathynella (fig. 13D) and Paraiberobathynella (fig. 13G); in Texanobathynella,therearethreedifferentcombinations among the five species: (1-2-1-3) (fig. 13K), (2-2-1-3) and (2-1-0-3). Montanabathynella (fig. 13L) and Parabathynella (fig. 13M) present other combinations with more setae in the first three segments (see table 4 for details). The internal seta of the second endopod segment is always plumose.
Thoracopods ii - vii: All species of the Iberobathynellini tribe have epipod on thoracopods II to VII, and one outer distal smooth seta on the basipod; Montanabathynella lacks an epipod on thoracopods II and III. The exopod, which is always shorter than the four segments of the endopod, consists of two segments in most species of the tribe, except I. magna (three segments in thoracopods IV and V) and species of Paraiberobathynella (three or four segments) and Texanobathynella (three segments in some thoracopods) (see table 4); Montanabathynella can have between two and six segments, and in these cases, the exopod is longer than the endopod, and Parabathynella has two segments in all thoracopods, except in P. badenwuerttembergensis, which has two, six or seven segments in thoracopods IV and V; two terminal barbed setae are commonly present on each segment and, on the last one, one of the setae is plumose; ctenidia groups present at the base of the setae and on the posterior side. The endopod consists of four segments of different sizes: the first is about half the length of the second and third, which are similar in length, and the fourth is very small; segment one short and without setae except in the species of the subgenus Iberobathynella that have a terminal inner plumose seta (also found in species of Montanabathynella and P. badenwuerttembergensis); segment two with two groups of lateral ctenidia and two setae, one plumose and one smooth (absent on thoracopod VII and sometimes thoracopod VI); segment three with one tiny seta (except in Texanobathynella) and segment four with one seta and two similar strong claws.
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Female thoracopod viii (fig. 14): The eighth pair of thoracopods is greatly reduced in species of the Parabathynellidae family. In the tribe Iberobathynellini (except the genus Texanobathynella) it reduced to a simple segment with a relatively triangular appearance, a wrinkled (in six species of the subgenera Asturibathynella and Espanobathynella, fig. 14A, B, E, H, I, O) or smooth cuticle (fig. 14C, D, F, G, J-N, P-Z), one, two or three small teeth and without setae (fig. 14 A-Z); in Texanobathynella, it has a scale-like appearance with small terminal denticles (fig. 14 AA, BB). Thoracopod VIII in females of Montanabathynella consists of two segments of similar length (basal segment slightly wider than the second one) (fig. 14 CC, DD); Parabathynella also has two segments but the basal segment is slightly longer than second one (fig. 14 EE). In both cases, denticles are present on the first segment, and three setae, on the second.
Male thoracopod viii (fig. 15): Its general appearance is almost square in most species of the tribe (fig. 15 A-D, F-H, J), rectangular in I. pedroi (fig. 15E) and in species of Texanobathynella (fig. 15K) and trapezoidal in Paraiberobathynella (fig. 15I); very large (twice as long as wide) in Montanabathynella (fig. 15L) and elongated in Parabathynella (fig. 15M). In species of the Iberobathynellini tribe, the penial region has three lobes: an outer lobe (O.lb), a dentate lobe (D.lb) and an inner lobe (I.lb). Montanabathynella has an additional lobe, the small lobe (S.lb) (fig. 15L), and Parabathynella has three lobes, the outer, inner and small lobes, but not a dentate lobe (fig. 15M). In all species of the tribe, the outer lobe of the male thoracopod VIII is well developed, in both length and width, the main axis of the lobe can be vertical or inclined on the posterodistal or anterodistal side, partially fused with the basipod at the level of the basal parts of the posterior edge of the lobe and the anterior face of the basipod (Serban, 1977) and is distinctive as a massive element of the lateral face always close to the endopod. The outer lobe differs in the various species: in the subgenera of Iberobathynella, it is rectangular with a sloping main axis in Espanobathynella (fig. 15A, D); orientated towards the posterior part and with a curved main axis in Asturibathynella (fig. 15B, C) and triangular with vertical main axis in Iberobathynella (fig. 15G); and in the other genera, it has a posterior part that is longer than the anterior part and a rectangular lateral side in Guadalopebathynella (fig. 15J); a distal part orientated towards the posterior side in Californibathynella (fig. 15F); an outer lobe smaller than the dentate lobe, with a triangular- or trapezoidal-shaped distal end in Paraiberobathynella (fig. 15I); triangular with setules on the distal end of the inner lobe in Texanobathynella (fig. 15K) and, in Hexaiberobathynella (fig. 15H) and anterior part shorter that is shorter than the posterior, a distal part strongly inclined toward the caudal part and a postero-distal inclination on the main axis; the outer lobe in Parabathynella is narrow and slightly longer than the exopod, and is not fused with the basipod (fig. 15M). The dentate lobe has between eight and 12 small teeth. The inner lobe, generally larger than the dentate lobe, may have small setules on the distal edge, as in the subgenus Iberobathynella (fig. 15G) and in I. asturiensis and I. espaniensis, or small spinules as in Texanobathynella (fig. 15K). The basipod (Bsp) is more or less conical and has a seta on the latero-external face of its distal end. The exopod, which is on the latero-external side of the basipod and covered by the outer lobe, is greatly reduced in all species of the Iberobathynellini tribe, and due to its small size, is the most difficult structure to observe in these species (fig. 15 A-K); sometimes with small teeth or denticles; Parabathynella has a row of small spines. Endopod always present, with distal end oriented on the latero-external side and with two setae; also present in Parabathynella (fig. 15M) and Montanabathynella (fig. 15L).
Pleopod: The first pair of pleopods, reduced to simple setae, is only present in Californibathynella californica. The other 32 species of the tribe, and those of Montanabathynella and Parabathynella, do not present pleopods nor simple setae.
Pleotelson: Dorsal margin of pleotelson with anal operculum not pronounced in most species of the tribe (21 species) and pronounced in the rest (13 species), including eight species of the subgenus Asturibathynella, one of Espanobathynella, I. pedroi, the two species of Hexaiberobathynella and the one of Californibathynella. Montanabathynella salish and P. motasi have a pronounced anal operculum but little protrusion.
Uropod (fig. 16): The sympod is considerably longer than wide in all species of the tribe, and almost always twice as long as the exopod and endopod; it has a row of spines that are equal in size (homonomous), as in the species I. burgalensis (fig. 16B), I. magna, I. cantabriensis and Pi. notenboomi (fig. 16I), or it has a row of spines in which the distal one is greater than the rest (inhomonomous) (fig. 16A, C-F, H, J-K); Montanabathynella (fig. 16L) and Parabathynella (fig. 16M) present an inhomonomous row of spines, similar to most species of the Iberobathynellini tribe; the row of spines can occupy half to two thirds of the sympod or almost its entire length (as in I. pedroi, fig. 16E); the number of spines is highly variable, between nine and 27 in the species of the subgenus Iberobathynella (fig. 16G) and between five and 13 in the subgenera Asturibathynella (fig. 16C, D) and Espanobathynella (fig. 16A, B) and in the rest of the tribe species (fig. 16E, F, H-K); species of Montanabathynella have 15 spines (fig. 16L) and those of Parabathynella, between six and 18 (fig. 16M). The endopod, in lancet form, has approximately the same length as the exopod in almost all species; it may lack setae (only I. cornejoensis and I. burgalensis, fig. 16B, C) or have one [nine species, including all of Paraiberobathynella (fig. 16I) and G. puchi (fig. 16H)], two [nine species (fig. 16D, E) including those of Hexaiberobathynella (fig. 16J)] or three (17 species, fig. 16A, F, G, K) setae that may be smooth, barbed or plumose and of different lengths. Exopod with apical and subapical setae (between two and five) and with (fig. 16A, C, D, E, G-K) or without (fig. 16B, F) a basal seta on the internal side; Montanabathynella (fig. 16L) has between seven and 11 setae, and Parabathynella, between four and eight (fig. 16M).
Furcal rami (fig. 17):The general shape is triangular or trapezoidal, with a variable number of spines, from five or six (as in I. cornejoensis, I. pedroi, Hi. mateusi, Californibathynella and Texanobathynella, fig. 17A, F, H, J-L) to 12 or 13 (as in I. paragracilipes and Pi. notenboomi, fig. 17E, I), and the two most distal spines are always larger; Montanabathynella has 11 to 14 spines (fig.17M) and Parabathynella has five to 10 (fig. 17N). On the dorsal side, the furcal rami have two plumose setae of different lengths.
description: Published as part of Camacho, Ana Isabel, Mas-Peinado, Paloma, López-Estrada, E. Karen, Dorda, Beatriz A. & Rey, Isabel, 2022, Split distribution, biogeography and morphological and genetic diversity of the Iberobathynellini Tribe in the family Parabathynellidae (Crustacea, Malacostraca, Bathynellacea), pp. 1-61 in Contributions to Zoology 91 (1) on pages 33-48, DOI: 10.1163/18759866-BJA10024, http://zenodo.org/record/8359271