OSTRACODA LATREILLE, 1806

Horne, David J., Smith, Robin J., Whittaker, John E. & Murray, John W., 2004, The first British record and a new species of the superfamily Terrestricytheroidea (Crustacea, Ostracoda): morphology, ontogeny, lifestyle and phylogeny, Zoological Journal of the Linnean Society 142 (2), pp. 253-288 : 255-262

publication ID	https://doi.org/ 10.1111/j.1096-3642.2004.00134.x
persistent identifier	https://treatment.plazi.org/id/74788546-FFB4-5136-FF35-FF56FCA3F895
treatment provided by	Diego
scientific name	OSTRACODA LATREILLE, 1806
status

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CLASS OSTRACODA LATREILLE, 1806 View in CoL ORDER PODOCOPIDA SARS, 1866

SUBORDER CYTHEROCOPINA GRÜNDEL, 1967 View in CoL SUPERFAMILY TERRESTRICYTHEROIDEA SCHORNIKOV, 1969 View in CoL [NOM. TRANS. HARTMANN & PURI, 1974] FAMILY TERRESTRICYTHERIDAE SCHORNIKOV, 1969 View in CoL GENUS TERRESTRICYTHERE SCHORNIKOV, 1969 View in CoL

Type species: Terrestricythere ivanovae Schornikov, 1969: 495–497 , figs 1–16.

Diagnosis

Carapace with curved dorsal margin, LV larger than RV. LV with small lobe-like extension overlapping RV towards anterior margin. Hinge ‘visordont’ (see section titled ‘The hinge of Terrestricythere ’, below, for formal definition), with two teeth on RV situated towards anterior and posterior margins and joined by ridge running along dorsal margin. Lobes interlock and rotate in two pits on hinge of LV so that LV dorsally overrides RV. Basic adductor muscle scar pattern of five in approximately vertical row, second and third from bottom diagonally offset from each other (second displaced anteriorly, third posteriorly, from imaginary vertical centre line). Antennula with five or six articulated podomeres. Antennal exopodite a plate with seven or eight long setae. Mandibular palp with rake setae and branchial plate with one ray. Female fifth limb endopodite with three articulated podomeres; modified into clasping palps in males. Sixth limb with four robust podomeres, with a series of short claws and setules along anterior edge. Seventh limb with five podomeres, terminating in two slender, hooked claws, one longer than the other. Furcal rami each reduced to three small setae. Eye absent.

TERRESTRICYTHERE ELISABETHAE SP. NOV.

( FIGS 1–17, 21 View Figure 21 , 25 View Figure 25 , 26 View Figure 26 )

Type locality

Tidal estuary of the River Cur (tributary of the Hamble Estuary) Hampshire, UK, 50∞54¢09.1≤N, 1∞15¢14.4≤W; oak leaf and reed litter overlying mud in the high intertidal zone reed marsh.

Type material

Holotype: a male, with soft parts dissected in Hydromatrix and sealed in a glass slide (No. 2003.1025). Collected 2 May 2002.

Allotype: a female, with soft parts dissected in Hydromatrix and sealed in a glass slide (2003.1023).

Paratypes: two males with soft parts dissected in Hydromatrix sealed in a glass slide and valves stored in a cavity slide (2003.1026 and 1027); one female with soft parts dissected in Hydromatrix sealed in a glass slide (2003.1024); two valves stored in a cavity slide (2003.1028); seven whole specimens critically point dried (2003.979, 980, 984–987, 997); three male specimens critically point dried each with one valve removed (2003.990, 992, 994).

Etymology

Named for Professor Elisabeth Alve (University of Oslo), friend and collaborator, who while researching the foraminiferal habitats of the Hamble creeks, in particular that of the agglutinating species Balticammina pseudomacrescens (Bronniman, Lutze & Whittaker) – the ‘highest’ of the high salt marsh foraminifera – and being of an inquisitive nature, found a niche that does not appear to have been searched before... and discovered the ostracod Terrestricythere .

Diagnosis

Species of Terrestricythere with five articulated podomeres in antennula (podomeres four and five fused) and four articulated podomeres in L7 endopodite. L7 terminating in one long and one short claw; long claw approximately five times length of short claw. Each valve bearing laterally three exceptionally long sensilla with bifurcated ends. Male copulatory appendage with two distal processes, larger elongate, curved, smaller hook-shaped.

Description of adult male ( Figs 1–6)

Carapace: Lateral view posterior more rounded than anterior. Dorsal margin strongly curved, with posterior and anterior angle. Ventral margin gently convex. LV larger than RV with most overlap dorsally. Dorsal view ovoid, posterior more rounded than anterior; LV with small lobe-like extension overlapping RV towards anterior margin. Hinge ‘visordont’ (see ‘The hinge of Terrestricythere ’, below, for formal definition), with two teeth on RV situated towards anterior and posterior margins and joined by ridge running along dorsal margin. Lobes interlock and rotate in two pits on hinge of LV. As carapace opens, dorsal portion of LV slides over RV ( Fig. 3 View Figure 3 ). Calcified inner lamella forms ‘U’ shape both anteriorly and posteriorly around pits on LV; calcified inner lamella anteriorly broader than posteriorly. Adductor muscle scars consisting of five elongate scars, slightly offset, but parallel with each other and anteriorly with one rounded scar ( Fig. 3 View Figure 3 ). Dorsally with six or seven small, round scars near ·

hinge. Surface of valves smooth, but with approximately 142–153 normal pores on each valve, more densely packed towards ventral margin ( Fig. 4 View Figure 4 ). Dorsally, sensilla of pore systems simple, but further towards ventral margin sensilla become increasingly bushy. Marginal pore canals numerous with protruding bushy ‘shaving brush’ sensilla. Each valve with additional three unusually long sensilla (up to 145 Mm in length) originating from mid lateral position, often with bifurcating tip.

An1: five segmented, robust and stout ( Fig. 5 View Figure 5 ). 1st podomere subquadrate. 2nd podomere subquadrate with one long and one shorter setae on ventral edge, one mid-apical seta and one short subapical-dorsal seta. 3rd podomere subquadrate with four apical setae. 4th podomere elongate, with four setae on dorsal edge and six dorsal-apical setae. 5th podomere with three apical setae and one apical aesthetasc.

An2: robust, stout and biramous ( Fig. 5 View Figure 5 ). 1st podomere (coxa) broad, with one anterior-apical and one posterior-apical setae. 2nd podomere (basis) with one small mid-positioned seta, and one longer anterior apical seta. Exopodite protrudes from anterior-apical corner of basis; consists of small rounded plate supporting seven or eight long and one short setae; long setae reach past distal end of limb with short setules along distal half, and terminate in small hooks. Endopodite with three podomeres. 1st podomere with three posterior-proximal aesthetascs, one large and one smaller claw on posterior edge. 2nd podomere elongate with one posterior-subproximal aesthetasc, two claws on posterior edge, one aesthetasc and one claw in posterior-subapical position, two anteriorsubapical claws and two anterior-apical claws. 3rd podomere small and subquadrate apically with four claws and one aesthetasc.

Md: coxa small, with reduced outer margin; with one seta on outer edge and five large and two smaller teeth ( Fig. 5 View Figure 5 ). Outermost tooth curved with setules, next tooth broad and rounded, with many small setules along edge. Other teeth robust and smooth. Basis with two setae on inner edge and branchial plate (exopodite) on outer edge consisting of one long seta with flat end. Endopodite consists of three quadrate podomeres. 1st podomere with two setae in innerproximal position and two inner-apical setulous setae. 2nd podomere with two outer-apical setae and one long, one short setae and one claw on inner-apical corner. 3rd podomere with one long, one mid-length and one short, curved claws. A row of eight closely spaced, setulous rake setae (= filter grille?) arising on palp near basis-endopodite joint; whether these setae inserted on basis or on proximal podomere of endopodite uncertain.

Oesophagus: in living specimens an amber-coloured plate was observed through the carapace, apparently within the oesophagus, in mid-position, anterior of maximum height. In dissections the plate was seen to have numerous setules pointing up towards the stomach.

Mx: endopodite with two segments, 1st podomere with one stout seta on outer edge and with one stout and one smaller setae on outer apical corner ( Fig. 5 View Figure 5 ). Final podomere quadrate, with two claws and two setae. 1st, 2nd and 3rd endites with numerous, setulous setae. Large, broad setulous seta originates near base of 2nd endite. Branchial plate with two large, broad, setulous reflexed setae and 18 setulous setae arranged around posterior edge.

L5: four segmented ( Fig. 6 View Figure 6 ). Protopodite with exopodite inserted on posterior-distal edge and represented by one long, setulous seta. Apically, protopodite with one long and four shorter setae on inner edge. 1st endopodite podomere elongate with four spines, two setulous setae and numerous setules on anterior edge; 2nd small and rectangular, wider than long; 3rd with one small posterior-apical seta and apically fused with large, broad, proximally curved claw.

L6: five segmented and robust ( Fig. 6 View Figure 6 ). Protopodite with exopodite inserted on posterior-distal edge and consisting of one long, setulous seta. Additionally with one seta on anterior edge and apically with three setae on anterior corner. 1st endopodite podomere elongate with numerous setules along anterior edge and with two large and two small claws on anterior-apical cor- ·

ner. 2nd and 3rd endopodite podomeres both quadrate and each with one large and two small claws on anterior-apical corner. 4th endopodite podomere subquadrate with one small seta on posterior edge and apically with one large, and one smaller claw.

L7: five segmented and slender ( Fig. 6 View Figure 6 ). Protopodite proximally broad with two setae on anterior edge, and two anterior-subapical setae; exopodite seta (posterior-proximal) apparently absent. 1st endopodite podomere proximally curve; 2nd without setae; 3rd with one small anterior-apical seta; 4th with one short, curved, smooth claw and one much longer smooth, curved claw.

Fu: reduced to pair of small protuberances each bearing three small setulous setae, situated between bases of Hem ( Fig. 6 View Figure 6 ).

Hem: rounded with triangular process at base ( Fig. 6 View Figure 6 ). Distally with two clasping processes. Smaller clasping process with hooked end, blunt process on inner edge and rounded lobe on outer edge. Larger clasping process elongate with convexly curved edges, inner edge more curved than outer edge, and with rounded end.

Description of adult female

Carapace, An1, An2, Md, Mx, L6 and L7 similar to those of adult male.

L5: four segmented ( Fig. 6 View Figure 6 ). Protopodite with exopodite inserted on posterior-distal edge and consisting of one long, setulous seta. Apically, protopodite with one long and four shorter setae on inner edge. 1st endopodite podomere with one anterior-apical seta and numerous setules along anterior edge; 2nd with one large claw and two small spines on anterior-apical corner; 3rd subquadrate with one small seta on posterior edge and apically with one large, and one smaller claw.

Fu: pair of small protuberances each bearing three short distal setae, situated between genital lobes.

Female genitals: rounded lobe with wide internal duct ( Fig. 6 View Figure 6 ). Duct coiled at anterior end and straight posteriorly, terminating in rounded end.

Remarks

In addition to T. elisabethae sp. nov. there are two other described species belonging to the genus Terrestricythere : T. ivanovae Schornikov, 1969 and T. pratensis Schornikov, 1980 . The carapace shape of T. elisabethae is most similar to that of T. pratensis , although our species is slightly higher in lateral view. In contrast, T. ivanovae is distinctly more elongate than T. elisabethae and T. pratensis . The three long, lateral sensilla on each valve in T. pratensis and T. elisabethae seem to be absent in T. ivanovae . The An1 of T. ivanovae has six articulated podomeres, compared with five in both T. pratensis and T. elisabethae .

In other podocopid ostracod families the number of articulated podomeres is regarded as significant at generic level, e.g. in the Loxoconchidae (see Athersuch & Horne, 1984), but we do not think it would serve any useful purpose at present to split the genus Terrestricythere on the basis of this character. Both T. ivanovae and T. pratensis have an L7 that terminates with a long claw and a shorter claw approximately half the length of the long claw ( Fig. 7 View Figure 7 ). In T. elisabethae the shorter claw of the L7 is only about 1/5th of the length of the long claw. Also the L7 endopodite of T. ivanovae has only three articulated podomeres (the distal two being fused), while T. elisabethae and T. pratensis have four.

The hemipenes of all three species consist of a rounded basal capsule with two distal processes ( Fig. 7 View Figure 7 ). The outer edge of the larger process is smoothly curved in both in T. ivanovae and T. elisabethae , but in T. pratensis it is broader than in the other two species and bears an anvil-shaped protuberance on its outer edge which is pointed at both ends. The smaller process is short and rather quadrate in T. ivanovae , narrow and curved in T. pratensis , and rather broad and distinctly hook-shaped in T. elisabethae .

Schornikov’s (1969) original illustration of the L7 of T. ivanovae was misinterpreted by Horne, Cohen & Martens (2002: 33) who included the incorrect statement... ‘Seventh limb bearing a branchial plate with three rays’... in their diagnosis of the Terrestricytheroidea ; the apparent branchial plate is in fact the furca.

Ontogeny

The following section does not provide a detailed description of each instar, but notes the changes from one instar to the next.

Instar A-8

Carapace: Length 130 Mm, height 90 Mm (one specimen measured). Uncalcified and flexible, rounded, smooth surface. Dorsal margin strongly curved, ventral margin gently curved. Hinge adont. Each valve with three pore systems ( Fig. 4 View Figure 4 ).

An1: five podomeres, last four all wider than long ( Fig. 8 View Figure 8 ). 3rd podomere with one rounded, broad, dorsal-apical seta; 4th with two broad, short, rounded apical setae; 5th with four short, broad, rounded, apical setae.